THE BETA-LACTAMASES OF MORAXELLA (BRANHAMELLA) CATARRHALIS ISOLATED FROM DANISH CHILDREN

Two distinct beta-lactamases have been isolated from Moraxella catarrh alis: the stronger acting BRO-1 enzyme and the weaker acting BRO-2. Se veral reports have noted an effect of penicillin and ampicillin on inf ections caused by M. catarrhalis in spite of the presence of beta-lact amase production. The purpose of this work was to characterize the bet a-lactamases of M. catarrhalis isolated from Danish children regarding type and susceptibility, and to relate these findings to the eradicat ion of beta-lactamases-producing strains by use of antibiotic treatmen t with penicillin or ampicillin. MICs for penicillin V, ampicillin, ce furoxime and amoxicillin/clavulanic acid (2:1) were determined in 70 s trains of M. catarrhalis: 46 strains from children with lower respirat ory tract infection (LRTI) and 24 strains from respiratory healthy chi ldren, beta-lactamase production was found in 59 strains. The BRO-1 en zyme was identified by isoelectric focusing in 55 strains (93.2%) and BRO-2 in 3 strains (5.1%); in 1 strain no isoelectric bands were produ ced. All strains were susceptible to cefuroxime and amoxicillin/clavul anic acid, and non-beta-lactamase-producing strains were susceptible t o penicillin and ampicillin. For the beta-lactamase-producing strains, MIC(50) of penicillin was 8.0 mu g/ml, while MIC(50) of ampicillin wa s 1.0 mu g/ml and MIC(90) of ampicillin was 2.0 mu g/ml. M. catarrhali s was more often eradicated from the children who received antibiotic treatment with penicillin or ampicillin than from those who did not re ceive any treatment, indicating an in vivo effect of penicillin and am picillin in spite of the beta-lactamase production.