Recent Changes to the Recommendations

Jenny Andrews

Members of the BSAC Working Party on Susceptibility Testing

ScientificDr. D. Brown (Chairman & Secretary of EUCAST)Mrs. Andrews(Secretary)Miss. KingDr. LivermoreDr. WinstanleyDr. Perry

Veterinary ServiceMr. C. Teale

MedicalProfessor MacGowan (President of the BSAC)Professor C. GemmellDr. N. DamaniDr. M. DrydenDr. N. BrownDr. G. Kahlmeter (SRGA & EUCAST)

IndustryMr. P. Wheat (Mast)Mr. C. Booth (Oxoid)

Versions of the recommendations

First publication in the BSAC Newsletter in the summer 1998Publications in the JACSupplement July 2001 Standardized disc method JAC May 2004Website

Version 2 July 20012.1 August 20012.1.1 January 20022.1.2 August 20022.1.3 February 20032.1.4 May 20032.1.5 November 20033 January 2004 (current version)

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BSAC website (www.bsac.org.uk)Site directory About BSAC Alliance for prudent use

of Antibiotics

What’s on Announcements Awards

News BSAC Working Party

Publications

Consumer-section

Resources Education Resource Evidence Based Medicine & Clinical Effectiveness

Guides Garrod Medal & Lecture Grants Programme

External Contacts JAC Membership

Discussions MISC National Prevalence Survey of MRSA Therapy

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What’s onSusceptibility Testing

Susceptibility TestingBSAC Working Party on Susceptibility TestingWorking Party membership and remit

Susceptibility Testing NewsBackground information on some of the recent updates to the BSAC Guidelines and issues currently under review

Susceptibility Testing – Powerpoint presentationsPowerpoint presentations from previous User Group Days

User Group Day ReportsReports and question & answer sessions from previous User Group Days

Residential Workshops & User Group DaysDetails of forthcoming events

Guide to Antimicrobial Susceptibility TestingThe complete guide to antimicrobial susceptibility testing (with links to individual chapters), based on the JAC Suppl 2001

BSAC Standardized Disc Susceptibility Testing MethodCurrent method with previous versions and other additional methodology

BSAC Disc Diffusion Template programme

BSAC Standardized Method Development Centre

Guide to Antimicrobial Susceptibility TestingChapter One: History and development of antimicrobial susceptibility testing

Chapter Two: Determination of minimum inhibitory concentrations

Chapter Three: Establishing MIC breakpoints and the interpretation of in vitro susceptibility tests

Chapter Four: The development of the BSAC standardized method of disc diffusion testing

Chapter Five: BSAC standardized disc susceptibility testing method

Chapter Six: Detection of beta-lactamase-mediated resistance

Chapter Seven: Detection of methicillin/oxacillin resistance in staphylococci

Chapter Eight: Quality assurance of antimicrobial susceptibility testing by disc diffusion

Chapter Nine: Recommendations for susceptibility tests on fastidious organisms and those requiring special handling

Chapter Ten: Instrumentation in antimicrobial susceptibility testing

Chapter Eleven: Interpretative reading: recognizing the unusual and inferring resistance mechanisms from resistance phenotypes

Resources - Susceptibility Testing

BSAC Working Party on Susceptibility TestingWorking Party membership and remit

Susceptibility Testing NewsBackground information on some of the recent updates to the BSAC Guidelines and issues currently under review

Susceptibility Testing – Powerpoint presentationsPowerpoint presentations from previous User Group Days

User Group Day ReportsReports and question & answer sessions from previous User Group Days

Residential Workshops & User Group DaysDetails of forthcoming events

Guide to Antimicrobial Susceptibility TestingThe complete guide to antimicrobial susceptibility testing (with links to individual chapters), based on the JAC Suppl 2001

BSAC Standardized Disc Susceptibility Testing MethodCurrent method with previous versions and other additional methodology

BSAC Disc Diffusion Template programme

BSAC Standardized Method Development Centre

BSAC Standardized Disc Susceptibility Testing Method

Current version Current version 3 January 2004Changes included in the most current version of the methodPrevious versionsVersion 2.1.5 November 2003Version 2.1.4 May 2003Version 2.1.3 February 2003Version 2.2.2 August 2002Version 2.1.1 January 2002Version 2.1 August 2001Version 2 July 2001Additional MethodologyDetection of Extended Spectrum Beta-lactamases (ESBLs) in E. coli and Klebsiella spp.The use of Etests with BSAC MethodologyMIC testing of M. catarrhalis with ampicillin/amoxycillinTesting for dissociated resistance in Staphylococci

Presentation of MIC breakpoints (mg/L)(Major organisational change)

In line with European consensus (EUCAST)MIC (as previously) MIC breakpoint concentration = organism susceptibleMIC > (previously ) MIC breakpoint concentration = organism resistantAppearance in the tables

Previously R 16, S 8Changes to R > 8, S 8

Avoids the theoretical `gap’ inherent in the previous system

MIC and zone breakpoints for Enterobacteriaceae and Acinetobacter

g. Salmonella spp. – for ciprofloxacin there is clinical evidence to indicate a poor response in systemic infections caused by Salmonella spp. with reduced susceptibility to fluoroquinolones (ciprofloxacin MICs 0.125-1 mg/L). This reduced susceptibility is most reliably detected with nalidixic acid 30 g discs as strains with reduced susceptibility show no zone of inhibition.

N. gonorrhoeaeResistance to ceftriaxone, cefotaxime and cefixime has not been described, however isolates with chromosomally encoded reduced susceptibility to penicillin have slightly reduced zones of inhibition with these antibiotics but remain susceptible. Results for isolates with reduced zones around ceftriaxone, cefotaxime and cefixime discs should be confirmed by MIC determinations.

NB. Referral to the Reference Laboratory at ColindaleOnly send isolates with reduced susceptibility to azithromycin or the cephalosporins

Detection of ESBLs in E. coli and Klebsiella species

As a general rule laboratories should test isolates to both ceftazidime (best indicator for TEM and SHV-derived ESBLs) and cefotaxime (the best indicator for CTX-M types)

Alternatively, cefpodoxime can be used as an indicator for all ESBLs

Any organism showing reduced susceptibility to ceftazidime, cefotaxime or cefpodoxime should be investigated for ESBL production

Many different methods but all depend on detecting synergy between clavulanic acid and the indicator antibiotic/s used in primary screening

S. maltophilia:All isolates with co-amoxyclav MICs of 32 mg/L

Data provided by Anna King

Stenotrophomonas maltophiliaDifficult to test because results are affected by temperature of incubation and media content.All aminoglycosides, polymixins and carbapenems should be reported resistant without testingMost, but not all, S. maltophilia are susceptible to cotrimoxazole.Testing should be at 300C zone of 20 mm = S.For -lactams and quinolones susceptibility testing is unreliable, but combinations of ciprofloxacin and a -lactam or aztreonam and co-amoxyclav have had a favourable clinical response.

Testing for dissociated resistance in staphylococci

Organisms exhibiting blunting

 

Isolate has MLSB

and clindamycin should be used with caution (if at all).

 

NB.

Disc on the left 5 g erythromycin, disc on right 2 g clindamycin

Under review

Alpha-haemolytic streptococci

Coryneforms

Fast growing anaerobes