Resistance to beta-lactams in a Gram positive cocci identified as Gemella morbillorum

AMOROSO A; DEMARES D; LEARDINI N; MASSA R; MOLLERACH M; GUTKIND G

Lieja, Bélgica

Simposio; International Symposium From Peptidoglycan Biosynthesis to Antibiotic Resistance. Present and Future; 1997

Centro de Ingenieria de Proteínas. Universidad de Lieja

We studied two different clinical isolates preliminarily identified as Gemella morbillorum with strong differences in the antibiotic susceptibility. In the sensitive isolate (MIC<0.01 mg/l) both for penicillin or cefotaxime), three high molecular weight PBPs (from 78 to 64 kDa) and a low molecular weight PBP (<40 kDa could be detected). PBP1 and 2 were almost saturated at concentrations close to MIC value. In the resistant isolate (ß-lactamase negative) with MICs 8 and 16 mg/l respectively, changes in the apparent molecular weight and relative affinity for the HMW PBPs were observed suggesting a complex mechanism for resistance acquisition. Transformation assays were performed to evaluate the possibility of genetic exchange with pneumococci using Streptococcus pneumoniae R6 as recipient. Donor DNA from the resistant strain allowed to obtain transformants with higher MIC to cefotaxime than R6 (8 to 64 fold) and the MIC to benzylpenicillin (0.02 mg/l). A low affinity form of PBP2x was observed in the analysis of the PBP profile of two transformants. The inter-specific transformation could suggest the presence of genes homologous to the pneumococcal PBP2x in this resistant strain.