Vancomycin therapeutic drug monitoring: is there a consensus view? The results of a UK National External Quality Assessment Scheme (UK NEQAS) for Antibiotic Assays questionnaire.

This study investigated vancomycin therapeutic drug monitoring (TDM) and issues related to patient management. Questionnaires were distributed to 310 participants in the UK National External Quality Assessment Scheme (NEQAS) for Antibiotic Assays. The response rate was 57.4%. The majority (76%) had an 'in-house' assay service based, almost exclusively, in the microbiology department, and a fluorescence polarization immunoassay (FPIA) was used by 97%. Almost half (48.7%) had an assay service available for 24 h/day, 7 days/week and 92.7% expected same-day results. The majority (80%) had issued guidelines for vancomycin use. A 12 hourly initial dosing regimen was used by 89%. Trough assay samples were taken <10 min before the dose by 91.5%. For post-dose assay samples, 44% took a sample at 1 h, 28% at 2 h and the remainder at 'other' times. For trough target ranges, 93% quoted <10 mg/L or 5-10 mg/L. There was no consensus with regard to post-dose assay sample times and 23 ranges were quoted. The majority (74.4%) regarded a trough level of >or=10 mg/L as 'toxic' but 13 concentrations were quoted as toxic post-dose measurements. In conclusion, there was a wide variability and poor consensus with regard to post-dose vancomycin assay sampling times, target ranges and what constituted a toxic level.

Typing of Listeria monocytogenes by random amplified polymorphic DNA (RAPD) analysis.

The aim of the study was to determine the effectiveness of random amplified polymorphic DNA analysis in typing Listeria monocytogenes from human infections. Twenty-five L. monocytogenes serogroup 1/2 and 70 serogroup 4 including 14 serovar 4b(x) were typed by RAPD-PCR analysis. Six primers were used to type each L. monocytogenes isolate and the DNA amplification performed with supertaq DNA polymerase in a Hybaid Thermal Reactor. Each bacterial strain was analysed separately with all primers and the profiles were judged by eye and designated to a group by comparison to other strains. Bands were classified as major or minor. Based on analysis of major band patterns, the 25 serogroup 1/2 isolates gave rise to 12 different groups. The groups only contained serovar 1/2a or 1/2b with a single exception. Using minor bands all isolates could be distinguished. All the serogroup 4 isolates gave the same major band patterns. The 14 serovar 4b(x) isolates which were epidemiologically related gave identical profiles with the exception of one isolate. Of the remaining strains, 41 produced individual patterns on minor band analysis. RAPD analysis with multiple primers is low cost, discriminatory and is most ideally suited to testing small (< 50) numbers of strains. We have shown that serogroup 1/2 L. monocytogenes strains are a more diverse group than serovar 4b strains and RAPD-PCR will provide a technique of considerable value in typing L. monocytogenes in the future.

A critical assessment of the agar dilution chequerboard technique for studying in-vitro antimicrobial interactions using a representative beta-lactam, aminoglycoside and fluoroquinolone.

The agar dilution chequerboard technique of studying antimicrobial interactions was assessed by testing a representative beta-lactam (piperacillin/tazobactam), aminoglycoside (gentamicin) and fluoroquinolone (ciprofloxacin) against themselves, that is piperacillin/tazobactam plus piperacillin/tazobactam, gentamicin plus gentamicin and ciprofloxacin plus ciprofloxacin. In addition, combinations of piperacillin/tazobactam plus gentamicin or ciprofloxacin were also tested against Enterobacteriaceae and Acinetobacter spp. in triplicate. The agar dilution chequerboard technique did not reliably show addition when agents were combined with themselves, and there was also considerable variation when beta-lactam plus aminoglycoside or fluoroquinolone combinations when tested in triplicate. These observations, and problems with the design of the method, indicate that the chequerboard technique should be used only with adequate controls and replication, and then interpreted with extreme caution; ideally, it should not be used as a method of assessing antimicrobial interactions.