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Most often asked questions

Most often asked questions. Jenny Andrews. Current Working Party members. Aim of the Working Party. Provide recommendations appropriate for susceptibility testing in the UK and Ireland

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Most often asked questions

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  1. Most often asked questions Jenny Andrews

  2. Current Working Party members

  3. Aim of the Working Party • Provide recommendations appropriate for susceptibility testing in the UK and Ireland • Continually review the recommendations, taking into account the introduction of new antibiotics and emerging mechanisms of resistance • Provide support for users of the BSAC method

  4. BSAC recommendations • 1991- Guide to sensitivity testing (Questionnaire- 91% would consider using a standardized method) • 1998-Summer BSAC Newsletter (Standardized Disc Testing Method) • 1999- Amendments and additions • 2001-July Supplement Version 2 (website) • 2005- Version 4

  5. Scientists outside the UK asking for help

  6. Other requests for help • Degree/projects- have given advice to 29 individuals (USA Georgia Acidovora avenae found on water melons-advice given by Trevor Winstanley) • Veterinary laboratories (Northern Ireland, Scotland, England, Turkey, Australia) [Chris Teale represents this group on the working party] • Pharmaceutical industry

  7. Organisms Method Control UTI Respiratory Staphylococci Enterobacteriaceae Enterococci N. gonorrhoeae Mechanisms of resistance Etest NEQAS Website Main topics to be discussed

  8. Organisms

  9. Method • Template (written and supported by Trevor Winstanley) • Preparation of inoculum • Direct sensitivity tests (blood cultures & urines) • Can Oxoid Iso-Sensitest agar be substituted by media from other manufacturers? • Disc contents not used in the UK (SRGA data)

  10. Control strains • Filling the gaps in the recommendations (BSAC rolling programme) [devising intra-laboratory ranges until recommendations available] • Controls repeatedly outside the acceptable range [rolling programme](meropenem ATCC 27853 P. aeruginosa- no change; gentamicin NCTC 6571 S. aureus under review; trimethoprimNCTC & ATCC E. coli zone ranges increased 28-34mm to 30-37mm & 20-26mm to 25-31 mm respectively; co-amoxiclav E. coli NCTC 11560 range reduced from 18-23 mm to 12-18mm) • Using the acceptable ranges laboratories detected that one commercial supply of ciprofloxacin discs were under-dosed • Control ranges for N. gonorrhoeae ATCC 49226 • Providing controls to India, Egypt

  11. Organisms associated with uncomplicated UTIs in women of child-bearing age NB.Complicated UTIs and S. epidermidis and S. aureus (usually associated with more serious infections)- use systemic Zone diameter BPs • E. coli • P. mirabilis • Enterococci • S. saprophyticus • Group B streptococci

  12. UTI • Cotrimoxazole – because of blood and skin disorders associated with this combination there are no BSAC recommendations CSM recommendations: cotrimoxazole should only be used for UTIs when there is evidence of susceptibility and a good reason to prefer this combination to a single antibiotic. • Trimethoprim– John Washington: enterococci should be regarded as resistant because they utilise exogenous folate in vivo which is absent from the medium used for testing, therefore isolates appear falsely susceptible in vitro to trimethoprim and co-trimoxazole • An exhaustive search of the literature was unable to support the hypothesis of Washington • Recommendations now available for trimethoprim

  13. UTI • Gaps – often antibiotics used systemically therefore use these recommendations • Coliforms absent from the recommendations-where distribution is not good and there is overlap between the susceptible and resistant populations (e.g. cephalexin). • ID to species level is essential for applying expert rules(for amoxicillin/ampicillin/co-amoxiclav, `These interpretative standards apply only to E. coli and P. mirabilis and not species that havechromosomal penicillinases (Klebsiella spp.) or those that typically have inducible AmpC (e.g. Enterobacter spp., Citrobacter spp. And Serratia spp.’) • `In the absence of a definitive ID, use the recommendations most appropriate for the presumptive ID, accepting that on some occasions the interpretation may be incorrect. A more cautious approach is to use the systemic recommendations.’

  14. RespiratoryH. influenzae:Interpretation of amoxicillin/co-amoxiclav and cefuroxime • Isolates with zone diameters 2-3 mm smaller than the zone diameter BP for co-amoxiclav reported S to amoxicillin & cefuroxime (including NEQAS specimen 5853 [co-amoxiclav MIC 0.5 mg/L MIC BP 1 mg/L] • Zone diameter BPs reviewed and amended • Currently there are occasional enquiries from laboratories regarding isolates with borderline susceptibility to the three agents (Becky Walker undertaking a higher degree to elucidate the mechanisms of resistance to the -lactam antibiotics)

  15. Respiratory • S.pneumoniae: Interpretation of resistance to penicillin - `Organisms with a penicillin MIC  1 mg/L are considered susceptible to -lactam antibiotics except in infections of the central nervous system.’ • Recommendations for S. pneumoniae v trimethoprim- MIC 50 8 mg/L; MIC90 >128 mg/L; MIC BP 0.5 mg/L

  16. Respiratory • Interpretation of susceptibility of H. influenzae to cefaclor- Professor MacGowan `The pK/pD data indicates cefaclor has borderline activity against H. influenzae, even for community use (free drug T>MIC of 25% with 250 mg and 37% with 500 mg dosing, suggested conservative T>MIC for cephalosporins in the community practice is 40-50%; MIC50 = 2 mg/L, MIC90 = 8 mg/L, MIC BP 1 mg/L). The outcome of infection will be difficult to predict and susceptibility testing is likely to have limited value.’

  17. Staphylococci • Recommendations using cefoxitin to detect resistance in S. aureus • General problems with detection of methicillin resistance (possible penicillinase hyper-producing isolates – PCR or latex for confirmation of resistance) • Using -lactams other than meticillin/oxacillin/cefoxitin to detect resistance `Staphylococci exhibiting resistance to meticillin/oxacillin/cefoxitin should be regarded as resistant to other penicillins, cephalosporins, carbapenems and combinations of -lactam and -lactamase inhibitors’ Applies to S. saprophyticus

  18. Staphylococci • Mupirocin: Harbath et al suggest that there is a need to detect LLR because there is an association with persistence of carriage. Risk factors for persistent carriage of methicillin-resistant Staphylococcus aureus. Harbath et al Clin Infect Dis. 2000 Dec; 31(6):1380-5 • Method developed by the BSAC using a 20 g mupirocin disc. • Availability of discs

  19. Teicoplanin 30 ug disc with CNS - Cambridge 35 MIC 0.5 – 4 mg/L MIC 0.5–4mg/L 30 MIC 8-64 mg/L MIC 8–64mg/L 25 20 Number of isolates 15 10 5 0 6 8 10 12 14 16 18 20 22 24 26 28 30 Zone diameter (mm)

  20. MIC and zone diameter BPs for ampicillin, amoxicillin and co-amoxiclav for interpreting the susceptibility of Enterobacteriaceae

  21. Enterobacteriaceae:Reporting LLR to fluoroquinolones

  22. Enterococci • Recommendations for tetracycline • Detection of glycopeptide susceptibility – usually solved if plates incubated for 24 h to allow micro-colonies to be visualised

  23. N. gonorrhoeae • 2002 GRASP survey showed that resistance to ciprofloxacin had risen to 9.8%, indicating that the target of >95% efficacy in first-line therapy was no longer achievable. • Recommendations for cefixime(oral) & ceftriaxone (intramuscular) • Availability of ceftriaxone 5 g discs • Which cephalosporin for gonorrhoea? Professor Catherine Ison et al on behalf of the North Thames Audit group. This report underscores the use of cefixime and ceftriaxone, but finds that cefuroxime is a poor alternative

  24. Detection of mechanisms of resistance

  25. Etest • Availability of method for testing by the BSAC methodology (www.bsac.org.uk) in the BSAC Standardized Disc Susceptibility Method section, Additional Methods, The use of Etests with BSAC methodology • Do we run a course for use of Etest

  26. NEQAS • Derek Brown at Addenbrookes and the SMDC in Birmingham are the reference laboratories for MIC testing by BSAC methodology • Questions arise when laboratories do not get the expected result (often occurs with organisms with borderline susceptibility) • The Working Party tries to investigate the problems

  27. Website • Availability of latest version • Automatic notification of changes • Would it be possible to have a Word file available to download

  28. Final comment 2002 University of Utah, USA I am very curious why your committee saw the need for a different disc susceptibility method. Do you find major inaccuracies in the NCCLS method? It would seem that even if your methods are equally accurate, it confuses the world community to have two different standards. (EUCAST Harmonization - Gunnar Kahlmeter)

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