Evaluation of antibiotic resistant clinical isolates of aerobic and anaerobic bacteria; investigation of the genetic background of resistance by molecular biological methods (OTKA T037475).

Participants: Dr. József Sóki (leader), Dr. Elisabeth Nagy, Dr. Ilona Veréb, Edit Urbán

Institute of Clinical Microbiology, University of Szeged, H-6725 Szeged, Somogyi B. tér. 1., Hungary

Examination of the resistance mechanisms against antibacterial agents has a great significance even today because of the appearance of more resistant organisms and the new resistance mechanism among them. Such bacteria are the staphylococci, Streptococcus pneumoniae, members of Enterobacteriacae and the clinically also important, anaerobic Bacteroides spp. having the emerging glycopeptide, penicillin, III. and IV. generation cephalosporin and carbapenem and nitroimidazole resistances, respectively. In the case of the bacterial groups and antibiotic resistances mentioned above we investigate not also the resistance levels but the molecular background of the resistance mechanisms. Among others, we focus on the IRT phenotype causing resistance against the b -lactam/b -lactamase inhibitor combinations among Escherichia coli and Klebsiella pneumoniae strains isolated in Hungary, and examine the modifications of the resistance genes. In the case of Bacteroides strains we investigate the mechanism of the activation of the imipenem and metronidazole resistance genes by insertion sequence elements, the genetic factors that harbor them, and also type our strains by molecular methods with respect the antibiotic resistance genotypes.

In 2002, the first year of our project, we studied a collection of carbapenem-resistant Bacteroides strains. (n=21), that were from the USA, Hungary and Kuwait.. 13 of them carried the well known metallo-β-lactamase gene (cfiA) and the possible role of insertion sequence elements in expression of these genes were demonstrated in 10 strains. Among these a new, un-described insertion sequence (IS943) element was identified and sequenced. In 3 strains other activation mechanism than the insertion sequence elements upstream of the cfiA resistance genes could be supposed. In 8 strains the carbapenem resistance could be mediated by other mechanism than the cfiA gene. (1) These results implicate that the carbapenem resistance among Bacteroides can be more diverse then previously thought. Also, we described the resistance mechanism of two metronidazole-resistant B. fragilis isolated in Hungary (1, 2), and we started to study a collection of members of Enterobacteriaceae that are amoxicillin/clavulanate-(Augmentin)resistant.

1. J. Sóki, E. Fodor, D. W. Hecht, R. Edwards, V. O. Rotimi, E. Urbán, E. Nagy (2002) Molecular investigation of the prevalence and mechanism of imipenem and metronidazole resistance of Bacteroides isolates. "Anaerobic Olympiad, 2002" June 29- July 2, Park City, UT, USA

2: E. Urbán, J. Sóki, J. S. Brazier, E. Nagy, B.I. Duerden

Prevalence and characterization of nim genes of Bacteroides spp. Isolated in Hungary

Anaerobe (in press)