KOETH LM, JACOBS M, BAJAKSOUZIAN S, WINDAU A, APPELBAUM P, KOSOWSKA K, HINDLER J; Interscience Conference on Antimicrobial Agents and Chemotherapy (43rd: 2003: Chicago, Ill.).

Abstr Intersci Conf Antimicrob Agents Chemother Intersci Conf Antimicrob Agents Chemother. 2003 Sep 14-17; 43: abstract no. D-230.

Laboratory Specialists, Inc., Westlake, OH.

BACKGROUND: Amoxicillin- and penicillin-resistant S. pneumoniae (SPNEU) with penicillin MICs 1-2 dilutions below the amoxicillin and amoxicillin-clavulanic acid (amox-CA) MICs, have recently, but infrequently (2-5%), been noted in surveillance studies. MICs of 15 of these strains that also had 10 similar changes in PBP2B were obtained. METHODS: Penicillin, amoxicillin and amox-CA were tested with frozen, dried, and freshly made broth microdilution MIC panels and agar dilution according to NCCLS standards and with Etest. Each MIC was compared to that obtained at site A using a frozen panel (REF) and each site tested all or a subset by one or more method. RESULTS: Method/site amoxicillin MICs that were within +/-1 dilution of the REF included: 100% for dried, fresh and agar (sites A-C); 80% for frozen (site B); 40% for Etest (site A); and 22.2% for Etest (site B). Amox-CA MICs were similar to amoxicillin MICs. The doubling dilution difference of amoxicillin MIC using various methods at sites A-C as compared to REF and %S, I, R are: [table: see text]. CONCLUSIONS: Etest amoxicillin MICs were lower than agar or broth methods (fresh, frozen or dried panels) for 15 Spneu with known alterations in PBPs. Most Etest results were S or I for isolates that were I or R by NCCLS methods. For MICs determined using NCCLS methods, site to site variation was observed resulting in a one category shift for amoxicillin (R to I) for some strains. As the development of additional resistance mechanisms occur in Spneu, MIC methodologies must be evaluated in order to assure adequate detection of resistance.

Publication Types:

• Meeting Abstracts

Keywords:

• Amoxicillin
• Amoxicillin-Potassium Clavulanate Combination
• Microbial Sensitivity Tests
• Penicillins
• Research Design
• methods

Other ID:

• GWAIDS0025076

UI: 102264700

From Meeting Abstracts