Recent years have seen the emergence of teicoplanin usage for staphylococcal infections, in particular endocarditis, osteomyelitis, septic arthritis, and methicillin-resistant Staphylococcus aureus (MRSA). Teicoplanin is now routinely used as an alternative to vancomycin, due to its safety profile and ease of administration. This article discusses the advantages for teicoplanin, the need for routine monitoring, and the various associated methodologies.
by Dr Francis H. Y. Fung
Background
Teicoplanin was first isolated and identified from antibiotic-producing strains of Actinoplanes teichomyceticus in 1978, and was shown to be highly active against both aerobic and anaerobic Gram-positive pathogenic bacteria [1]. This anti-bacterial agent was initially thought to belong in the class of glycopeptide antibiotics that act as cell wall inhibitors such as vancomycin, ristomycin, and mannopeptins. Barna et al. [2] first described the molecular structure of teicoplanin A2 in 1984, as five similar glycopeptides characterized by different fatty acid chains of 10 to 11 carbon atoms (which make up the majority of teicoplanins found in vivo) (Fig. 1), and four minor related compounds that may also be present in very minute quantities. The five major side chains (A2-1 to A2-5) have terminal groups of CH–NH2, whereas in the four minor compounds (R2-1 to R2-4) this is substituted by a C=O group.
The letter ‘R’ denotes where each fatty acid chain attaches to the side group on the teicoplanin molecule. Its structure contains the identical ABCD ring system that is also found in vancomycin, another antibiotic within the same family. In addition to a small modification in the DE ring system, teicoplanin lacks the β-hydroxyl group, a site of sensitivity in vancomycin, and it also has an additional FG ring system that is not present in vancomycin. It is these subtle yet crucial differences that will prove to be a major differentiating factor between the two drugs.
Teicoplanin versus vancomycin
In vitro binding studies revealed that teicoplanin interferes with the final stage of peptidoglycan synthesis (glycan polymerization and cross-linking) by binding to the terminal amino N-acyl-D-alanyl–D-alanine of the growing peptidoglycan or its precursors [2]. This N-acyl-D-alanyl–D-alanine group binds and forms a stoichiometric complex via the formation of five hydrogen bonds between the peptide backbone of the glycopeptide and the D-Ala–D-Ala dipeptide. The formation of this complex prevents any further peptidoglycan synthesis by sterically hindering the correct alignment of transglycosylase and its substrate. The antibiotic activity and potency of teicoplanin, particularly against Streptococcus and Enterococcus species, are also well documented [3]. Despite the increasing frequency of glycopeptide resistance, teicoplanin has always shown clinical worth, especially in treatment of life-threatening sepsis.
Vancomycin, a similar antibiotic in the same glycopeptide family, has historically been the drug of choice for the treatment of diseases caused by methicillin-resistant Staphylococcus aureus (MRSA). The emergence of MRSA strains in the community setting can cause infections ranging from cellulitis with skin abscesses to pneumonia in otherwise healthy individuals. Although vancomycin hydrochloride has been the accepted standard therapy for MRSA infections, its potential nephrotoxicity is one of the major limitations for its routine use. Some studies have found an increased risk of renal failure following vancomycin treatment [4], because of its effects on proximal tubular cells where the antibiotic can accumulate inside lysosomes.
Teicoplanin has been shown to have essentially the same efficacy as vancomycin but with some advantages, such as once-daily bolus administration for dose management. In addition, the pharmacokinetic profile of teicoplanin also offers the patient a choice of administration routes of either intramuscular or intravascular delivery. Several side effects of vancomycin treatment are known, such as ‘red man’ syndrome, a combination of erythema, pruritus, and hypotension, which can be an immediate adverse event of vancomycin infusion. The likelihood of this reaction is greatly reduced with teicoplanin [5]. Perhaps the most widely recognized clinical problem with the vancomycin regime is nephrotoxicity in the patient. Meta-analysis of comparative trials have demonstrated that adverse events were less likely to occur with teicoplanin (13.9%) compared with vancomycin (21.9%) (P=0.0003). This was particularly significant when nephrotoxicity was considered: 4.8% versus 10.7% (P=0.0005) for teicoplanin and vancomycin, respectively [6]. This is of added relevance for patients with renal failure, as evidence suggests dosage adjustment is of paramount importance because of their impaired renal clearance.
A number of studies have been carried out comparing the efficacy and safety of these two drugs, showing the potential for teicoplanin as a suitable alternative to vancomycin [7]. This systematic review and meta-analysis of 24 randomized controlled trials in 2009 highlighted the advantages of teicoplanin over vancomycin. More importantly, total adverse events were found to be less frequent, and nephrotoxicity to be lower for teicoplanin usage, especially when administered in combination with aminoglycosides. The safety profile of teicoplanin has also been shown to be favourable, where severe skin reactions can result due to vancomycin-related infusion and the subsequent release of histamine [8]. Comparison studies with other drugs also used for bacterial infection treatments such as clindamycin, rifampicin, netilmicin, and enoxacin provide further support for the pharmacological profile of teicoplanin [9].
There is evidence of disadvantages in teicoplanin administration, such as hypersensitivity manifesting as fever and chills. Some patients with a positive reaction to teicoplanin can also tolerate vancomycin, where no major advantage lies with either drug. Thrombocytopenia can also develop, although this occurred almost exclusively in patients receiving much larger teicoplanin doses than are now recommended. The majority of the available evidence favours the bacteriolytic effect of teicoplanin [10], where base concentrations of just 1 µg/mL can cause rapid lysis of streptococcal cells in exponential phase. Due to increased bacterial resistance to vancomycin through the substitution of the D-Ala–D-Ala terminus of the peptidoglycan precursor by D-Ala–D-Lac, teicoplanin does seem to hold several major advantages. In addition to the similar and competitive cost of treatment, teicoplanin is emerging as a suitable and appropriate alternative to vancomycin for Staphylococcus infections.
Therapeutic drug monitoring
Therapeutic drug monitoring (TDM) plays an important role in the optimization of drug therapy, especially for drugs with narrow therapeutic ranges. Since the introduction of home therapy and the use of teicoplanin in the community, clinicians have paid close attention to serum concentrations of teicoplanin in their administration regimen, as multifactorial education programmes with active TDM have been shown to be efficacious in maintaining the appropriate use of antibiotics in various healthcare settings [11].
Predominately (>90%) bound to plasma proteins, teicoplanin is mostly cleared renally and only 2–3% of an intravenously administered dose is metabolized. Total teicoplanin clearance rate has been reported to be 11 mL/h/kg, and steady state is achieved slowly – 93% after 14 days of repeated administration [12]. It is believed an optimal loading dose followed by appropriate maintenance doses should achieve the teicoplanin trough serum concentration of 25 µg/mL rapidly and steadily, increasing the chances of full recovery for the patient. Care should be taken when teicoplanin is substituted for vancomycin, as it has a longer half-life: about 40 hours compared to that of 3–5 hours for vancomycin [13]. Because of its longer half-life, teicoplanin only needs to be administered once daily. Administration should be tailored to the individual, as each patient has varying degrees of hepatic and renal function: age, infection, and concomitant use of certain drugs are a few factors that can alter the rate of clearance. Nevertheless, an 800 mg initial dose followed by 400 mg maintenance doses for the following 48 hours has been accepted for safely achieving an optimal teicoplanin trough level. Re-assessment would then take place to determine if additional maintenance doses are needed, and, if so, what the course of action would be. It is important to ascertain the ideal pre-dose serum concentrations, as it can be a predictor of outcome for the patient. However, the rate of success with the treatment declines with age, again highlighting the need to consider other factors pertaining to the individual patient.
Measurement of teicoplanin: a brief history
The solid-phase enzyme receptor assay (SPERA) was most widely used for TDM initially, capable of measuring glycopeptides of the vancomycin family. The assay was based around the interaction of teicoplanin and acyl-D-alanyl–D-alanine, where the antibiotic of interest and enzyme-labelled teicoplanin compete for a synthetic analogue of the biological receptor, albumin-E-aminocaproyl-D-alanyl–D-alanine. Using this method for teicoplanin determination in human serum the intra-assay CV (coefficient of variation) was reported to be 7.2%, inter-assay CV to be 11.2%, and the analytical recovery to be 94% [14]. SPERA correlated well with other available microbiological assays at the time, and it was accepted as a good tool for identification and quantitative detection of teicoplanin.
The disk diffusion (or Kirby Bauer) test used Petri dishes containing the antimicrobial agent covering the surface of the agar. The size of the area free of the microbe being tested was proportional to the effectiveness of the antibiotic. Similarly, the agar incorporation method used viable colonies from overnight cultures to inoculate Sensitivity Test Agar plates containing doubling teicoplanin concentrations. The lowest concentration that inhibited growth would then be assigned the MIC (minimum inhibitory concentration) value. These were more of a qualitative rather than a quantitative assay, and its clinical usage was fairly limited. There were also commercially available kits, such as the high-inoculum Etest method (AB Biodisk, Solna, Sweden) that detects intermediate glycopeptide susceptibility. Etest strips covered with teicoplanin are exposed to infusion agar and incubated for 48 hours at 37°C, and results read at the point of complete growth inhibition. A VITEK assay from bioMerieux (Marcy l’Etoile, France) also used overnight agar plate cultures to measure teicoplanin effect and determined its MIC. This latter method could be automated for the clinical laboratory; however, it still lacked the precision one expects from an assay used for TDM in MRSA resistance.
Increasing popularity of immunoassays paved the way for the implementation of fluorescence polarization immunoassay (FPIA). Based on the principle of competitive binding and the reagent limited concept, the TEICOPLANIN Assay System (Abbot TDx) uses fluorescein-labelled antigen to compete with sample antigen for a fixed number of antibody binding sites. In recent years there has been an emergence of high-performance liquid chromatography (HPLC) as an alternative to FPIA, a method that has several advantages over the traditional immunoassay. The improvements lie within the various components that constitute an HPLC system, since the characteristics of various compounds in a sample matrix can be very different (Fig. 2). Tandem mass spectrometry assays have also recently been developed to measure teicoplanin in patient serum [15], providing the most sensitive method yet for monitoring this therapeutic drug.
Conclusion
As teicoplanin administration gains popularity with clinicians dealing with TDM, there lies a growing need for close assessment of its serum levels. In addition to clinical outcomes, accurate measurement of teicoplanin allows the administration of a definitive loading dose and appropriate maintenance doses to ensure the rapid recovery of patients and improved quality of life. A large number of assays are now available in clinical biochemistry laboratories, and end users are encouraged to adopt these methodologies.
References
1. Parenti F, Beretta G, Berti M, Arioli V. Teichomycins, new antibiotics from Actinoplanes teichomyceticus Nov. Sp. I. Description of the producer strain, fermentation studies and biological properties. J Antibiot. (Tokyo) 1978; 31: 276–283.
2. Barna JC, Williams DH. The structure and mode of action of glycopeptide antibiotics of the vancomycin group. Annu Rev Microbiol. 1984; 38: 339–357.
3. Parenti F, Schito GC, Courvalin P. Teicoplanin Chemistry and Microbiology. J Chemother. 2000; 12(Suppl 5): 5–14.
4. Hidayat LK, Hsu DI, Quist R, Shriner KA, Wong-Beringer A. High-dose vancomycin therapy for methicillin-resistant Staphylococcus aureus infections: efficacy and toxicity. Arch Intern Med. 2006; 166: 2138–2144.
5. Wilson AP. Comparative safety of teicoplanin and vancomycin. Int J Antimicrob Agents 1998; 10: 143–152.
6. Wood MJ. Comparative safety of teicoplanin and vancomycin. J Chemother. 2000; 12(Suppl 5): 21–25.
7. Svetitsky S, Leibovici L, Paul M. Comparative efficacy and safety of vancomycin versus teicoplanin: systematic review and meta-analysis. Antimicrob Agents Chemother. 2009; 53: 4069–4079.
8. Davey PG, Williams AH. A review of the safety profile of teicoplanin. J Antimicrob Chemother. 1991; 27(Suppl B): 69–73.
9. Covelli I, Nani E. Microbiological profile of teicoplanin. J Chemother. 1991; 3(Suppl 1): 39–42.
10. Chmara H, Ripa S, Mignini F, Borowski E. Bacteriolytic effect of teicoplanin. J Gen Microbiol. 1991; 137: 913–919.
11. Pea F, Viale P, Pavan F, Tavio M, et al. The effect of multifactorial, multidisciplinary educational interventions on appropriate use of teicoplanin. Int J Antimicrob Agents 2006; 27: 344–350.
12. Wilson AP. Clinical pharmacokinetics of teicoplanin. Clin Pharmacokinet. 2000; 39: 167–183.
13. Boger DL. Vancomycin, teicoplanin, and ramoplanin: synthetic and mechanistic studies. Med Res Rev. 2001; 21: 356–381.
14. Corti A, Rurali C, Borghi A, Cassani G. Solid-phase enzyme-receptor assay (SPERA): a competitive-binding assay for glycopeptide antibiotics of the vancomycin class. Clin Chem. 1985; 31: 1606–1610.
15. Fung FH, Tang JC, Hopkins JP, Dutton JJ, et al. Measurement of teicoplanin by liquid chromatography-tandem mass spectrometry: development of a novel method. Ann Clin Biochem. 2012; 49(Pt 5): 475–481.
The author
Francis Fung PhD
Department of Clinical Biochemistry, Royal Liverpool University Hospitals, Liverpool, UK
E-mail: francis.fung@nhs.net
RX series
, /in Featured Articles /by 3wmediaAP32 IF Elite
, /in Featured Articles /by 3wmediaMedix MAB / Antigens
, /in Featured Articles /by 3wmediaUrine Analysis systems
, /in Featured Articles /by 3wmediaModular instruments for a synchronized lab
, /in Featured Articles /by 3wmediaCancer-causing pathogens: an update
, /in Featured Articles /by 3wmediaWhen the Scottish pathologist William Russell published his article “The Parasite of Cancer” in The Lancet over a century ago, it was met with complete incredulity by his medical colleagues who ‘knew’ that cancer was a non-communicable disease. Indeed it was not until the latter half of the 20th century, when the link between Epstein-Barr virus and Burkitt’s lymphoma was elucidated, that medical scientists finally gave some credence to Russell’s claim and conceded that there may be a very few cancer-causing pathogens. In the fifty years since then there has been a steadily expanding number of different viruses, bacteria and parasites found to cause cancer, the most serious in terms of numbers of cases being some of the Human Papilloma Viruses (cervical and anal cancer), Hepatitis B and C viruses (hepatocellular carcinoma) and Helicobacter pylori (gastric cancer). Such organisms can evade the host’s immune system, establish persistent infections of many years duration and ultimately trigger abnormal cell growth followed by tumour development. An article published a couple of years ago in The Lancet Oncology estimated that globally 16.1% of new cancer cases were due to infections.
Two years on this estimate might well be higher. The incidence of oropharyngeal cancers in developed countries had begun to decline with the decrease in tobacco use (smoking is a major risk factor), but this decline has not been sustained. Much current research is now being directed towards oropharyngeal cancers and HPV infection. Recent data suggest that over 40% of cases in Europe are attributable to this virus, and robust data from the Danish national database for head and neck cancers reveal an alarming 12-fold increase in oropharyngeal cancer in Denmark during the past 35 years, with HPV-positive disease increasing from 37% to 74% of cases during this period. Recent studies suggest that HPV may account for up to 80% of oropharyngeal cancer cases in North America. And now a team from the University of California has suggested that there may be a link between the common sexually transmitted parasite Trichomonas vaginalis and aggressive prostate cancer. It is known that this parasite can colonise the prostate, and the team found that it secretes a protein very similar to human macrophage migration inhibitory factor (HuMIF), a proinflammatory cytokine that is elevated in prostate cancer and that triggers inflammation and cell proliferation. Of course more work is needed to establish this and similar links between pathogens and cancer, but if vaccines and antimicrobial drugs could reduce the world’s cancer burden, then surely such research is crucial.
Teicoplanin in therapeutic drug monitoring
, /in Featured Articles /by 3wmediaRecent years have seen the emergence of teicoplanin usage for staphylococcal infections, in particular endocarditis, osteomyelitis, septic arthritis, and methicillin-resistant Staphylococcus aureus (MRSA). Teicoplanin is now routinely used as an alternative to vancomycin, due to its safety profile and ease of administration. This article discusses the advantages for teicoplanin, the need for routine monitoring, and the various associated methodologies.
by Dr Francis H. Y. Fung
Background
Teicoplanin was first isolated and identified from antibiotic-producing strains of Actinoplanes teichomyceticus in 1978, and was shown to be highly active against both aerobic and anaerobic Gram-positive pathogenic bacteria [1]. This anti-bacterial agent was initially thought to belong in the class of glycopeptide antibiotics that act as cell wall inhibitors such as vancomycin, ristomycin, and mannopeptins. Barna et al. [2] first described the molecular structure of teicoplanin A2 in 1984, as five similar glycopeptides characterized by different fatty acid chains of 10 to 11 carbon atoms (which make up the majority of teicoplanins found in vivo) (Fig. 1), and four minor related compounds that may also be present in very minute quantities. The five major side chains (A2-1 to A2-5) have terminal groups of CH–NH2, whereas in the four minor compounds (R2-1 to R2-4) this is substituted by a C=O group.
The letter ‘R’ denotes where each fatty acid chain attaches to the side group on the teicoplanin molecule. Its structure contains the identical ABCD ring system that is also found in vancomycin, another antibiotic within the same family. In addition to a small modification in the DE ring system, teicoplanin lacks the β-hydroxyl group, a site of sensitivity in vancomycin, and it also has an additional FG ring system that is not present in vancomycin. It is these subtle yet crucial differences that will prove to be a major differentiating factor between the two drugs.
Teicoplanin versus vancomycin
In vitro binding studies revealed that teicoplanin interferes with the final stage of peptidoglycan synthesis (glycan polymerization and cross-linking) by binding to the terminal amino N-acyl-D-alanyl–D-alanine of the growing peptidoglycan or its precursors [2]. This N-acyl-D-alanyl–D-alanine group binds and forms a stoichiometric complex via the formation of five hydrogen bonds between the peptide backbone of the glycopeptide and the D-Ala–D-Ala dipeptide. The formation of this complex prevents any further peptidoglycan synthesis by sterically hindering the correct alignment of transglycosylase and its substrate. The antibiotic activity and potency of teicoplanin, particularly against Streptococcus and Enterococcus species, are also well documented [3]. Despite the increasing frequency of glycopeptide resistance, teicoplanin has always shown clinical worth, especially in treatment of life-threatening sepsis.
Vancomycin, a similar antibiotic in the same glycopeptide family, has historically been the drug of choice for the treatment of diseases caused by methicillin-resistant Staphylococcus aureus (MRSA). The emergence of MRSA strains in the community setting can cause infections ranging from cellulitis with skin abscesses to pneumonia in otherwise healthy individuals. Although vancomycin hydrochloride has been the accepted standard therapy for MRSA infections, its potential nephrotoxicity is one of the major limitations for its routine use. Some studies have found an increased risk of renal failure following vancomycin treatment [4], because of its effects on proximal tubular cells where the antibiotic can accumulate inside lysosomes.
Teicoplanin has been shown to have essentially the same efficacy as vancomycin but with some advantages, such as once-daily bolus administration for dose management. In addition, the pharmacokinetic profile of teicoplanin also offers the patient a choice of administration routes of either intramuscular or intravascular delivery. Several side effects of vancomycin treatment are known, such as ‘red man’ syndrome, a combination of erythema, pruritus, and hypotension, which can be an immediate adverse event of vancomycin infusion. The likelihood of this reaction is greatly reduced with teicoplanin [5]. Perhaps the most widely recognized clinical problem with the vancomycin regime is nephrotoxicity in the patient. Meta-analysis of comparative trials have demonstrated that adverse events were less likely to occur with teicoplanin (13.9%) compared with vancomycin (21.9%) (P=0.0003). This was particularly significant when nephrotoxicity was considered: 4.8% versus 10.7% (P=0.0005) for teicoplanin and vancomycin, respectively [6]. This is of added relevance for patients with renal failure, as evidence suggests dosage adjustment is of paramount importance because of their impaired renal clearance.
A number of studies have been carried out comparing the efficacy and safety of these two drugs, showing the potential for teicoplanin as a suitable alternative to vancomycin [7]. This systematic review and meta-analysis of 24 randomized controlled trials in 2009 highlighted the advantages of teicoplanin over vancomycin. More importantly, total adverse events were found to be less frequent, and nephrotoxicity to be lower for teicoplanin usage, especially when administered in combination with aminoglycosides. The safety profile of teicoplanin has also been shown to be favourable, where severe skin reactions can result due to vancomycin-related infusion and the subsequent release of histamine [8]. Comparison studies with other drugs also used for bacterial infection treatments such as clindamycin, rifampicin, netilmicin, and enoxacin provide further support for the pharmacological profile of teicoplanin [9].
There is evidence of disadvantages in teicoplanin administration, such as hypersensitivity manifesting as fever and chills. Some patients with a positive reaction to teicoplanin can also tolerate vancomycin, where no major advantage lies with either drug. Thrombocytopenia can also develop, although this occurred almost exclusively in patients receiving much larger teicoplanin doses than are now recommended. The majority of the available evidence favours the bacteriolytic effect of teicoplanin [10], where base concentrations of just 1 µg/mL can cause rapid lysis of streptococcal cells in exponential phase. Due to increased bacterial resistance to vancomycin through the substitution of the D-Ala–D-Ala terminus of the peptidoglycan precursor by D-Ala–D-Lac, teicoplanin does seem to hold several major advantages. In addition to the similar and competitive cost of treatment, teicoplanin is emerging as a suitable and appropriate alternative to vancomycin for Staphylococcus infections.
Therapeutic drug monitoring
Therapeutic drug monitoring (TDM) plays an important role in the optimization of drug therapy, especially for drugs with narrow therapeutic ranges. Since the introduction of home therapy and the use of teicoplanin in the community, clinicians have paid close attention to serum concentrations of teicoplanin in their administration regimen, as multifactorial education programmes with active TDM have been shown to be efficacious in maintaining the appropriate use of antibiotics in various healthcare settings [11].
Predominately (>90%) bound to plasma proteins, teicoplanin is mostly cleared renally and only 2–3% of an intravenously administered dose is metabolized. Total teicoplanin clearance rate has been reported to be 11 mL/h/kg, and steady state is achieved slowly – 93% after 14 days of repeated administration [12]. It is believed an optimal loading dose followed by appropriate maintenance doses should achieve the teicoplanin trough serum concentration of 25 µg/mL rapidly and steadily, increasing the chances of full recovery for the patient. Care should be taken when teicoplanin is substituted for vancomycin, as it has a longer half-life: about 40 hours compared to that of 3–5 hours for vancomycin [13]. Because of its longer half-life, teicoplanin only needs to be administered once daily. Administration should be tailored to the individual, as each patient has varying degrees of hepatic and renal function: age, infection, and concomitant use of certain drugs are a few factors that can alter the rate of clearance. Nevertheless, an 800 mg initial dose followed by 400 mg maintenance doses for the following 48 hours has been accepted for safely achieving an optimal teicoplanin trough level. Re-assessment would then take place to determine if additional maintenance doses are needed, and, if so, what the course of action would be. It is important to ascertain the ideal pre-dose serum concentrations, as it can be a predictor of outcome for the patient. However, the rate of success with the treatment declines with age, again highlighting the need to consider other factors pertaining to the individual patient.
Measurement of teicoplanin: a brief history
The solid-phase enzyme receptor assay (SPERA) was most widely used for TDM initially, capable of measuring glycopeptides of the vancomycin family. The assay was based around the interaction of teicoplanin and acyl-D-alanyl–D-alanine, where the antibiotic of interest and enzyme-labelled teicoplanin compete for a synthetic analogue of the biological receptor, albumin-E-aminocaproyl-D-alanyl–D-alanine. Using this method for teicoplanin determination in human serum the intra-assay CV (coefficient of variation) was reported to be 7.2%, inter-assay CV to be 11.2%, and the analytical recovery to be 94% [14]. SPERA correlated well with other available microbiological assays at the time, and it was accepted as a good tool for identification and quantitative detection of teicoplanin.
The disk diffusion (or Kirby Bauer) test used Petri dishes containing the antimicrobial agent covering the surface of the agar. The size of the area free of the microbe being tested was proportional to the effectiveness of the antibiotic. Similarly, the agar incorporation method used viable colonies from overnight cultures to inoculate Sensitivity Test Agar plates containing doubling teicoplanin concentrations. The lowest concentration that inhibited growth would then be assigned the MIC (minimum inhibitory concentration) value. These were more of a qualitative rather than a quantitative assay, and its clinical usage was fairly limited. There were also commercially available kits, such as the high-inoculum Etest method (AB Biodisk, Solna, Sweden) that detects intermediate glycopeptide susceptibility. Etest strips covered with teicoplanin are exposed to infusion agar and incubated for 48 hours at 37°C, and results read at the point of complete growth inhibition. A VITEK assay from bioMerieux (Marcy l’Etoile, France) also used overnight agar plate cultures to measure teicoplanin effect and determined its MIC. This latter method could be automated for the clinical laboratory; however, it still lacked the precision one expects from an assay used for TDM in MRSA resistance.
Increasing popularity of immunoassays paved the way for the implementation of fluorescence polarization immunoassay (FPIA). Based on the principle of competitive binding and the reagent limited concept, the TEICOPLANIN Assay System (Abbot TDx) uses fluorescein-labelled antigen to compete with sample antigen for a fixed number of antibody binding sites. In recent years there has been an emergence of high-performance liquid chromatography (HPLC) as an alternative to FPIA, a method that has several advantages over the traditional immunoassay. The improvements lie within the various components that constitute an HPLC system, since the characteristics of various compounds in a sample matrix can be very different (Fig. 2). Tandem mass spectrometry assays have also recently been developed to measure teicoplanin in patient serum [15], providing the most sensitive method yet for monitoring this therapeutic drug.
Conclusion
As teicoplanin administration gains popularity with clinicians dealing with TDM, there lies a growing need for close assessment of its serum levels. In addition to clinical outcomes, accurate measurement of teicoplanin allows the administration of a definitive loading dose and appropriate maintenance doses to ensure the rapid recovery of patients and improved quality of life. A large number of assays are now available in clinical biochemistry laboratories, and end users are encouraged to adopt these methodologies.
References
1. Parenti F, Beretta G, Berti M, Arioli V. Teichomycins, new antibiotics from Actinoplanes teichomyceticus Nov. Sp. I. Description of the producer strain, fermentation studies and biological properties. J Antibiot. (Tokyo) 1978; 31: 276–283.
2. Barna JC, Williams DH. The structure and mode of action of glycopeptide antibiotics of the vancomycin group. Annu Rev Microbiol. 1984; 38: 339–357.
3. Parenti F, Schito GC, Courvalin P. Teicoplanin Chemistry and Microbiology. J Chemother. 2000; 12(Suppl 5): 5–14.
4. Hidayat LK, Hsu DI, Quist R, Shriner KA, Wong-Beringer A. High-dose vancomycin therapy for methicillin-resistant Staphylococcus aureus infections: efficacy and toxicity. Arch Intern Med. 2006; 166: 2138–2144.
5. Wilson AP. Comparative safety of teicoplanin and vancomycin. Int J Antimicrob Agents 1998; 10: 143–152.
6. Wood MJ. Comparative safety of teicoplanin and vancomycin. J Chemother. 2000; 12(Suppl 5): 21–25.
7. Svetitsky S, Leibovici L, Paul M. Comparative efficacy and safety of vancomycin versus teicoplanin: systematic review and meta-analysis. Antimicrob Agents Chemother. 2009; 53: 4069–4079.
8. Davey PG, Williams AH. A review of the safety profile of teicoplanin. J Antimicrob Chemother. 1991; 27(Suppl B): 69–73.
9. Covelli I, Nani E. Microbiological profile of teicoplanin. J Chemother. 1991; 3(Suppl 1): 39–42.
10. Chmara H, Ripa S, Mignini F, Borowski E. Bacteriolytic effect of teicoplanin. J Gen Microbiol. 1991; 137: 913–919.
11. Pea F, Viale P, Pavan F, Tavio M, et al. The effect of multifactorial, multidisciplinary educational interventions on appropriate use of teicoplanin. Int J Antimicrob Agents 2006; 27: 344–350.
12. Wilson AP. Clinical pharmacokinetics of teicoplanin. Clin Pharmacokinet. 2000; 39: 167–183.
13. Boger DL. Vancomycin, teicoplanin, and ramoplanin: synthetic and mechanistic studies. Med Res Rev. 2001; 21: 356–381.
14. Corti A, Rurali C, Borghi A, Cassani G. Solid-phase enzyme-receptor assay (SPERA): a competitive-binding assay for glycopeptide antibiotics of the vancomycin class. Clin Chem. 1985; 31: 1606–1610.
15. Fung FH, Tang JC, Hopkins JP, Dutton JJ, et al. Measurement of teicoplanin by liquid chromatography-tandem mass spectrometry: development of a novel method. Ann Clin Biochem. 2012; 49(Pt 5): 475–481.
The author
Francis Fung PhD
Department of Clinical Biochemistry, Royal Liverpool University Hospitals, Liverpool, UK
E-mail: francis.fung@nhs.net
Testing for gastrointestinal cytomegalovirus infection
, /in Featured Articles, Gastrointestinal Disorders /by 3wmediaby Dr Jingmei Lin and Dr Rong Fan Cytomegalovirus infection in the gastrointestinal tract likely occurs in periods of immunosuppression. The diagnosis of cytomegalovirus infection in the gastrointestinal tract can be made in several ways including serology, testing for viremia, viral culture from biopsy material, histopathologic examination coupled with immunohistochemistry, and molecular method […]
Improving the diagnosis of pulmonary tuberculosis in hard-to-reach patients in London, UK
, /in Featured Articles /by 3wmediaDeveloped countries have not escaped the rise in cases of multidrug-resistant tuberculosis. In the UK a mobile X-ray unit has been operating in London since 2005 and this service has been augmented with point-of-care testing (POCT) since 2011. POCT has been well received by patients and has greatly reduced the number of unnecessary hospital visits.
by Dr R. J. Shorten and Dr A. Story
Background
Tuberculosis (TB) is an infectious disease caused by the bacterium Mycobacterium tuberculosis. TB is primarily a respiratory disease, although it can affect any part of the body and it is spread from person to person via expectorated droplets by individuals with active pulmonary disease. TB is a significant international problem and in 1993 the World Health Organization declared tuberculosis a global emergency [1]. In 2012 there were 8.6 million new cases and 1.3 million deaths, the vast majority of these occurring in Asia and sub-Saharan Africa [2].
Multidrug-resistant TB
This global epidemic is further complicated by the increase in drug resistant M. tuberculosis. Multidrug-resistant TB (MDR-TB) is a form of TB caused by bacteria that do not respond to, at least, isoniazid and rifampicin, the two most effective, first-line anti-TB drugs. There were approximately 450 000 cases of MDR-TB globally in 2012. More than half of these cases were in India, China and the Russian Federation [2].
This epidemic has not been avoided in developed countries and following a century of decline, the incidence of TB in the UK has been rising since 1988. Data from Public Health England [3] shows that the majority of these cases are concentrated in urban areas, with almost 40% being in London (3426 cases in 2012). Additionally, one or more of the following risk factors were present in 7.3% of cases; history of problem drug use, alcohol misuse/abuse, homelessness or imprisonment. Furthermore, some of these individual risk factors are associated with smear positivity (those patients who are more likely to be contagious), drug resistance, poor adherence to treatment and loss to follow up [4]. Indeed, the growing problem of TB in these hard-to-reach groups has led to specific UK guidance [5].
Searching for patients
Find & Treat was established in 2005 to strengthen TB control in the socially excluded communities of London by working with over 200 partner organizations. The service has been evaluated as an innovative and cost-effective health and social care model [6]. The mobile X-ray unit (MXU) has been operating in London since this time and screens approximately 8000 patients per year (Fig. 1). It is staffed by TB nurse specialists, reporting radiographers, social workers and outreach workers and former TB patients with a lived experience of homelessness who work are Peer Educators. Its role is to identify hard-to-reach patients with suspected TB using digital chest radiographs. These patients are then linked into local healthcare provision via Accident & Emergency (A&E) departments or community TB programmes. In December 2011 the service was augmented with the Xpert MTB/RIF assay (Cepheid, Sunnyvale, California, USA), which was used as a point-of-care test (POCT) for the molecular detection of M. tuberculosis in sputum [7].
Point-of-care testing
Prior to the implementation of the Xpert assay, if a digital chest radiograph indicated active pulmonary TB (seen in 1–2% of patients screened), then the patient underwent immediate referral to the nearest hospital with a TB service. This involved a TB nurse specialist or outreach worker accompanying the patient to an A&E department for assessment, conventional microbiological investigation and possible admission. Approximately 20% of referred patients are subsequently confirmed to have TB and are initiated on a complex course of multiple antibiotics over a period of at least 6 months [8].
The Xpert MTB/RIF assay is a nucleic acid amplification test (NAAT). The easy to use analyser extracts, amplifies and detects DNA of M. tuberculosis in the patients’ sputum. The assay also detects approximately 95% of the common rifampicin resistance-conferring mutations in the rpoB gene (a surrogate marker of multidrug resistant TB) [9].
The hands-on time of the assay is minimal and a specimen container with a rubber septum in the lid allows the staff on the MXU to safely process sputum samples without the need for containment facilities or a microbiological safety cabinet (Fig. 2). MXUs exist in other European cities, but we believe that this is the first example of a NAAT POCT being used in this way anywhere in Europe.
Patients with abnormal X-rays that indicate active pulmonary TB are asked whether they can produce sputum. Those who can, expectorate a sample into the specific sample container. They seal the container and return it to the team on the MXU who assess the sputum for quality (sputum, rather than watery saliva is required). The sample reagent is carefully added through the rubber septum in the lid and swirled gently to allow homogenization of the sample. This process ensures that minimal aerosols are generated and that they are not released to cause exposure to the operator. The assay takes approximately 2 hours in total and the result will determine whether the patient requires immediate referral to a TB service. Patients with negative NAAT are followed up by two further sputum samples, including one early morning specimen, collected in the community and processed for routing smear microscopy and culture in hospital laboratories. Due to the high negative predictive value of the assay (94%) and the increased sensitivity compared to sputum microscopy [10], it is highly unlikely that any infectious cases will go undetected using this algorithm.
Considerations and advantages of POCT for TB
As the POCT is performed by non-laboratory staff, it is imperative that the MXU staff are comprehensively trained and assessed for competence. None of the staff had any laboratory or analytical experience prior to the implementation of this assay. Registered clinical laboratory staff are involved in all stages of implementation and training. A close working relationship between the MXU team and the clinical laboratory is required to ensure appropriate refresher training and review of standard operating procedures and risk assessments.
The assay has been well received by patients, particularly as a negative result prevents a referral to hospital. This allows MXU staff to focus resources on screening more patients, rather than accompanying patients to hospital who subsequently are confirmed to be clear of TB. The MXU regularly screens in custodial settings where capacity to effectively isolate suspected cases is limited and significant resources are required accompanying patients with suspected TB to hospital appointments for further investigations. The value of the assay in determining which patients are potentially infectious is especially useful in these settings. The ability of the Xpert MTB/RIF to detect most cases of rifampicin resistant (and therefore likely to be MDR) TB, allows the MXU team to initiate appropriate second-line therapy more rapidly. Additionally, the simplicity and safe use of the assay has been well adopted by the MXU staff. We have demonstrated the potential of this technology in focussing resources on the most appropriate individuals and therefore improving the quality of care in this vulnerable group of patients. A randomized controlled trial to assess the benefit of using this assay on patients with an abnormal chest X-ray against them being referred to secondary care is underway to accurately quantify the benefits of this assay in tackling TB in this group of patients.
Summary
The epidemiology of TB in 21st century big cities is characterized by a concentration of disease in hard-to-reach medically underserved populations. Capacity to outreach effective diagnostic platforms directly to high risk populations is likely to become an increasingly important feature of TB control [11].
References
1. World Health Organization (WHO). Tuberculosis. Fact sheet 104, 2012. 2. WHO. Tuberculosis. Media centre; Fact sheet 104, 2014.
3. Tuberculosis in the UK: Annual report on tuberculosis surveillance in the UK, 2013. London: Public Health England 2013.
4. Story A, Murad S, Roberts W, et al. Tuberculosis in London: the importance of homelessness, problem drug use and prison Thorax 2007; 62(8): 667–671.
5. National Institute for Health and Clinical Excellence (NICE): Public health guidance. Tuberculosis – hard-to-reach groups. PH37 2012.
6. Jit M, Stagg HR, Aldridge RW, et al. Dedicated outreach service for hard to reach patients with tuberculosis in London: observational study and economic evaluation. BMJ 2011; 343: d5376.
7. Boehme CC, Nabeta P, Hillemann D, et al. Rapid molecular detection of tuberculosis and rifampin resistance. N Engl J Med. 2010; 363: 1005–1015
8. NICE: Clinical guidelines. Tuberculosis: Clinical diagnosis and management of tuberculosis, and measures for its prevention and control. CG117 2011. (http://guidance.nice.org.uk/CG117)
9. Zhang Y, Yew WW. Mechanisms of drug resistance in Mycobacterium tuberculosis. Int Tuberc Lung Dis. 2009; 13(11): 1320–1330.
10. O’Grady et al. Evaluation of the Xpert MTB/RIF assay at a tertiary care referral hospital in a setting where tuberculosis and HIV infection are highly endemic. J Clin Infect Dis. 2012; 55(9): 1171–1178.
11. van Hest NA, et al. Tuberculosis control in big cities and urban risk groups in the European Union: a consensus statement. Euro Surveill. 2014;19(9): Article 7.
The authors
Rob J. Shorten1* BSc, MSc, PhD and A Story2 RGN MPH PhD
1Clinical Scientist, Department of Medical Microbiology, Central Manchester Foundation Trust and Honorary Research Associate, University College London Centre for Clinical Microbiology, UK
2Clinical Lead Find & Treat, University College Hospitals NHS Foundation Trust, London, UK
*Corresponding author
E-mail: rob.shorten@nhs.net
QC considerations for point-of-care testing
, /in Featured Articles /by 3wmediaPatient testing is increasingly being carried out at the bedside. Indeed the availability of point-of-care testing (POCT) instruments and devices has grown significantly in recent years. Undoubtedly POCT helps speed up the availability of results, but when such testing is moved outside of the laboratory setting how can accuracy be ensured? `
by Sarah Kee
In all patient testing, Quality Control (QC) exists to ensure accuracy and reliability. For many of the health care workers using POCT instruments, QC will be unfamiliar territory. Many of the standard QC procedures applied in laboratories cannot be applied to POCT devices. However, it is essential that both primary and community care settings apply well-structured QC procedures to ensure the accuracy and reliability of results, minimizing risk to patients and improving patient outcomes.
Designing a QC strategy for POCT
When designing a QC strategy for POCT devices there are three main issues that need to be considered:
1. Design of the devices
POCT devices can be broadly split into three categories with procedures varying according to instrument design:
For laboratory type instruments the design mirrors that of analysers found within the laboratory environment. Therefore, QC procedures should mirror those found within the laboratory: if patient tests are performed every day, then multi-level QC samples should also be run every day. The accuracy and reliability of these results should be monitored over time to provide a true reflection of performance. External Quality Assessment should be run in conjunction with Internal Quality Control (IQC).
For cartridge-based instruments, the technology differs from that found in standard laboratory type analysers and therefore to reflect this, QC should be performed differently.
Cartridge-based devices usually consist of a cartridge-based component and an electronic reader based component. The cartridge-based component contains all the necessary “ingredients” for the analysis of the patient sample while the electronic reader component is responsible for converting the result from the cartridge component into a numerical value. QC can be problematic as the QC technician is only ever testing the one particular disposable cartridge and the electronic function of the analyser that is in use at that specific time. Nevertheless, performing QC for these devices is still essential to ensuring the cartridge is performing correctly as damage may have occurred during transport, or the on-board reagents may have deteriorated. As a minimum, QC should be run when changing cartridge lot and periodically throughout the lot’s lifespan to ensure the stability of the on-board components. To fully ensure the instrument’s accuracy over time, technicians should also participate in an EQA scheme.
Strip-based instruments are very similar in design to cartridge-based instruments. Like cartridges, the strips are responsible for analysis of the sample, however, as the electronic component has no QC self-check feature, a faulty analyser could be producing erroneous results which remain undetected for some time. Because of this, QC processes should be more stringent for strip-based devices than cartridge-based devices. Strips should be checked on delivery using multi-level QC to ensure they have not been damaged during transit, as well as every day of patient testing. It is also important to participate in a frequent EQA scheme.
2. Possible risks to the patient
When implementing QC for POCT devices the risk of harm to the patient should be the foundation of the QC strategy: where and why do errors occur and what are the consequences of an erroneous result to the patient?
The QC strategy should balance the risk of harm to the patient with the stringency of the QC procedure applied. Studies have shown that the most common phase for errors in POCT is analytical, with 65.3% of errors occurring during this phase. In contrast, the analytical phase in laboratory testing is the least common source for errors. This highlights the need for QC procedures for POCT devices as the potential risk of harm to the patient is greater for POCT than laboratory-based tests.
As many POCT are used by non-laboratory professionals it is vital that users are trained to undertake QC – without QC results may not be accurate. Inaccurate results could have serious implications for the treatment the patient receives.
3. Who is responsible for QC in POCT?
According to ISO 22870:2006, a POCT management group should be set up with responsibility for managing and training staff using the equipment. This group should be responsible for the quality management strategy and implementing a programme of staff training, to include quality control, for all personnel performing POCT and interpreting results.
The running of QC samples on POCT devices should be performed by those who are using the devices regularly, as QC samples should be run as a patient sample would be and therefore must be performed by personnel who are responsible for patient testing.
IQC and EQA/PT – making appropriate choices for POCT Devices
Internal Quality Control (IQC) involves running samples containing analytes of known concentration, to monitor the accuracy and precision of the analytical process over time. Depending on the design of the device and risk of harm to the patient the IQC strategy will differ accordingly. When choosing appropriate IQC material for performing QC on POCT devices, it is important to look for material that offers the following benefits:
Interlaboratory data management software is available that will allow a laboratory to manage and interpret their QC data. This software is an extremely cost effective and efficient way to ensure that a laboratory’s POCT devices are performing at a high standard, allowing accuracy and precision to be monitored over time, thus providing a true reflection of performance of both the device and the personnel using the device.
This software is usually available with a peer group comparison functionality that will allow a laboratory to directly compare the results of their POCT devices to other laboratories using the same devices worldwide.
Proficiency Testing (external quality assessment) is strongly recommended for all point of care devices. ISO 22870:2006 states, “There shall be participation in external quality assessment schemes”. An EQA scheme assesses the accuracy of the POCT devices through direct results comparison of one device to identical devices worldwide. This peer comparison allows a laboratory to assess the accuracy of a device over time and provides confidence that the patient results being reported are accurate.
There are many PT schemes available for POCT devices; when choosing a scheme it is important that a laboratory considers the following:
The benefits of POCT are undisputed but only if we are assured of accurate results. Getting the right QC strategy in place now will ensure the contribution POCT makes to patient testing is a wholly positive one.
The author
Sarah Kee, BSc PGCE
QC Scientific Consultant
Randox Laboratories Ltd
E-mail: sarah.kee@randox.com
www.randox.com