Dissemination and genetic support of broad-spectrum beta-lactam-resistant Escherichia coli strain isolated from two Tunisian hospitals during 2004-2012.

Khaoula Ayari1, Amel Bourouis, Hela Chihi, Sihem Mahrouki, Thierry Naas, Omrane Belhadj.

1. Laboratory of Biochemistry and technobiology, Faculty of Sciences of Tunis, University Tunis El Manar,
2092 El Manar II, Tunisia.
2. Bacteriology-Virology service. CHU Bicetre 78 rue du Général Leclerc, 94275 Le Kremlin-Bicetre.

Abstract
Background: The dissemination of extended-spectrum β-lactamase (ESBL)-producing bacteria presented a great concern worldwide. Gram-negative organisms such as Escherichia coliand Klebsiella pneumoniaeare the most frequently isolated pathogens responsible for nosocomial infections.

Objectives: The aim of this study was to investigate and to follow the emergence of resistance and the characterization of Extended-Spectrum Beta-Lactamases (ESBL) among broad-spectrum beta-lactam-Escherichia coliclinical isolates recovered from the military hospital and Habib Thameur hospital in Tunisia.Methods: A total of 113 E.coliisolates obtained during the period 2004 through 2012 showed a significant degree of multi-resistance. Among these strains, the double-disk synergy test confirmed the ESBL phenotype in 46 isolates. These included 32(70%) strains from Hospital A and 14(30%) from Hospital B.

Results:The ESBL was identified as CTX-M-15. The ESBL resistance was transferred by a 60 kb plasmid CTXM-15-producing isolates were unrelated according to the PFGE analysis and characterization of the regions surrounding the blaCTX-M-15 showed the ISEcp1 elements located in the upstream region of the bla gene and 20 of them truncated by IS26.

Conclusion:ESBL producing E. coli strains are a serious threat in the community in Tunisia and we should take into consideration any possible spread of such epidemiological resistance.

Keywords: CTX-M-15, diverse clones, ESBLs, Escherichia coli.