Susceptibility of Moraxella catarrhalis isolates to beta-lactam antibiotics in relation to beta-lactamase pattern.
Moraxella catarrhalis isolates (n = 413) were collected from 20 clinical laboratories in England and Scotland in 1991 and were examined for beta-lactamase production by isoelectric focusing. beta-Lactamases were found in 375 isolates of which, 349 (93.1%) had BRO-1 enzyme and 26 (6.9%) had BRO-2. Minor variation in electrofocusing pattern occurred within both enzyme types. Ampicillin MICs for BRO-1 producers were 25-fold higher than for non-producers, but those for BRO-2 producers were raised only four-fold. MICs of cefaclor, cefixime, loracarbef, co-amoxiclav and cefetamet generally were two- to four-fold higher for BRO-1 producers than for BRO-2 producers and enzyme non-producers. Similarly, the inhibition zones of discs containing cefaclor, cefixime, loracarbef or co-amoxiclav were smaller for BRO-1 producers than for non-producers. Amongst the compounds tested, cefetamet seemed the least affected by beta-lactamase production in both MIC and disc tests. Overall, these results indicate that BRO-1 enzyme predominates amongst M. catarrhalis isolates from the UK, as in other countries, and suggest that BRO-1 production gives slight protection against many of the newer oral beta-lactams as well as causing ampicillin resistance.
Fung
C P
CP
Department of Medical Microbiology, London Hospital Medical College, UK.
Yeo
S F
SF
Livermore
D M
DM
D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D006801:Humans; D007525:Isoelectric Focusing; D008826:Microbial Sensitivity Tests; D001936:Moraxella catarrhalis / Q000145:classification / Q000187:drug effects* / Q000201:enzymology; D001618:beta-Lactamases / Q000096:biosynthesis*; D047090:beta-Lactams
D000900:Anti-Bacterial Agents; D047090:beta-Lactams; D001618:beta-Lactamases