SUSCEPTIBILITY OF MORAXELLA-CATARRHALIS TO 21 ANTIMICROBIAL DRUGS - VALIDITY OF CURRENT NCCLS CRITERIA FOR THE INTERPRETATION OF AGAR DISH DIFFUSION ANTIBIOGRAMS

Ninety-four clinical isolates of Moraxella catarrhalis were examined f or susceptibility to 21 antimicrobial drugs; 67 isolates (= 71.3 %) pr oduced beta-lactamase(s). In terms of antibiotic resistance, the numbe r of isolates resistant to penicillin G, ampicillin, and cotrimoxazole were 56, 32, and 1, respectively. The number of isolates with interme diate susceptibility to penicillin G, ampicillin, ciprofloxacin, oflox acin, cotrimoxazole, and fosfomycin were 11, 34, 1, 2, 2, and 47, resp ectively. All 94 isolates proved susceptible to ampicillin + 10 mu g/m l of sulbactam, amoxicillin + 4 mu g/ml of clavulanic acid, cefuroxime , cefotaxime, cefepime, cefixime, imipenem, meropenem, chloramphenicol , doxycycline, tetracycline, fusidic acid, erythromycin, clarithromyci n, and rifampin, as based on currently valid NCCLS criteria, where app licable. There were no very major or major discrepancies between agar dilution and agar disk diffusion test results. There were only a few m inor discrepancies between test results, specifically: penicillin G (c ategory IV = 4, category VI = 1); ampicillin (category IV = 4, categor y V = 1, category VI 7), amoxicillin + clavulanic acid (category III = 11), cotrimoxazole (category IV = 1, category V = 1, category VI = 1) , ciprofloxacin (category V = 1), and ofloxacin (category VI = 2). The sole exception was fosfomycin, with a total of 25 minor discrepancies encountered (category III = 14, category V = 9, category VI = 2). Wil kins-Chalgren agar compared favorably with Mueller-Hinton agar followi ng examination with 11 selected antimicrobial drugs against 31 represe ntative isolates of M. catarrhalis.