Disk diffusion susceptibility of Branhamella catarrhalis and relationship of beta-lactam zone size to beta-lactamase production

Abstract

We tested 231 isolates of BranhameUa catarrhalis for P-lactamase production and drug susceptibility by the National Committee for Clinical Laboratory Standards disk diffusion method. The nitrocephin disk (Cefinase) identified 13-lactamase in 98% of the enzyme-producing strains, and a zone diameter of inhibition of <29 mm for penicillin correctly predicted the presence of P-lactamase in 99% of the isolates. No resistance to erythromycin, tetracycline, trimethoprim-sulfamethoxazole, or amoxicillin-clavulanic acid was observed.Branhamella catarrhalis has received increasing attention as a potential pathogen of the upper and lower respiratory tract (4). Otitis media, sinusitis, bronchitis, and bronchopneumonia (the latter two primarily in patients with underlying lung disease) appear to be the major clinical diseases (9,17,18,21). In a recent study with Gram stain-directed cultures, B. catarrhalis was recovered from 5% of all acceptable sputum samples from patients with chronic lung disease over a 30-month period, and 11.5% of the samples contained a recognized pathogen; this latter incidence approached 20% in the winter months (16).Of major concern therapeutically has been the recognition that B. catarrhalis produces P-lactamase. The first known report of P-lactamase in this species appeared in 1977 (10).Since that time 3-lactamase production has spread, and many isolates now produce the enzyme (2,14,20 Cockeysville, Md.) and by the addition of extracts from acetone-treated cells (11) to a solution of nitrocephin (15).Disk diffusion susceptibility testing was done at the time of isolation with MHA by the procedure recommended by the National Committee for Clinical Laboratory Standards (NCCLS) (12). Isolates which failed to grow adequately were retested under 5% CO2 with chocolatized MHA. The majority of isolates were frozen at -70°C and regrown at a later date for the P-lactamase testing of cell extracts and for isoelectric focusing (IEF).Crude extracts from acetone-treated cells containing 1B-lactamase were submitted to IEF on polyacrylamide gels with LKB instruments. The details of this procedure and IEF results for many of the current isolates have been presented elsewhere (11).A total of 231 isolates were identified during the study period. With the Cefinase disk, 171 isolates (74%) were 13-lactamase positive. Of the 231 isolates, 146 were also tested for ,B-lactamase production by using cell extracts. Two isolates which were 1-lactamase negative by the disk test were positive with the acetone-treated cell extracts. Both isolates which gave an initial negative ,B-lactamase result had the 1908-type enzyme.Twenty-six isolates (11%) failed to grow adequately on MHA in room air and had to be restudied in 5% CO2 on chocolatized MHA. The other 89% produced good growth on overnight incubation on MHA. By disk diffusion, no isolates were identified which were resistant to erythromycin, moxalactam, amoxicillin-clavulanic acid, chloramphenicol, cefotaxime, trimethoprim-sulfamethoxazole, or sulfisoxazole. There was no diff...

Molecular Characterization of the β-Lactamases from Clinical Isolates of Moraxella ( Branhamella ) catarrhalis Obtained from 24 U.S. Medical Centers during 1994–1995 and 1997–1998

“…Our study showed the same general trend of higher ampicillin resistance among BRO-1-producing strains reported previously (8,10,15); however, the wide range of ampicillin MICs observed for BRO-1 strains was unexpected and suggests that factors other than enzyme type determine antibiotic susceptibility.…”

“…Although substrate hydrolysis rates of BRO-1 and BRO-2 enzymes are similar, BRO-1-producing isolates are more resistant to penicillins than BRO-2 strains (8,10,15). The higher ␤-lactam minimum inhibitory concentrations (MICs) associated with BRO-1 strains have been attributed to larger amounts of enzyme produced (15).…”

Disk diffusion susceptibility testing of Branhamella catarrhalis with ampicillin and seven other antimicrobial agents

“…Indeed, the authors of this report emphasized the need for a systematic investigation of disk diffusion susceptibility testing of B. catarrhalis with the aim of clearly defining an optimum test method and suitable interpretive criteria. Recently, there have been two published studies which have addressed this issue (13,23). In one study, however, only 25 strains of B. catarrhalis were examined, and 15 of these were not clinical isolates (23).…”

Development of a Disk Diffusion Method for Testing Moraxella catarrhalis Susceptibility Using Clinical and Laboratory Standards Institute Methods: a SENTRY Antimicrobial Surveillance Program Report

“…They did not find strains with poor growth when agar was incubated in ambient air. Luman et al (27) studied 231 isolates grown on Mueller-Hinton agar, using CLSI disk contents. Like our study, they too noted that a proportion of strains, 11% in their case, grew poorly in ambient air, and required retesting in 5% CO 2 .…”