Asian Jr. of Microbiol. Biotech. Env. Sc. Vol. 16, No. (2) : 2014 : 19-27 © Global Science Publications ISSN-0972-3005 *Corresponding author’s email: mechaimanel@yahoo.fr; Phone : 00213669165103 PREVALENCE AND CHARACTERIZATION OF EXTENDED- SPECTRUM β-LACTAMASE- PRODUCING ENTEROBACTERIACEAE ISOLATED FROM HOSPITAL ENVIRONMENTS DEBABZA MANEL 1 , MECHAI ABDELBASSET 1,2 AND CHETTIBI HOURIA 2 1 Department of Natural and Life Sciences, Faculty of Exact Sciences and Natural and Life Sciences, Tebessa University, 12000. Algeria. 2 Microbiology laboratory, Faculty of natural and life sciences, Badji-Mokhtar University, Annaba 23000, Algeria. (Received : 22 November, 2013; accepted : 20 December, 2013) Key words: Enterobacteriaceae, Antimicrobial susceptibility, Extended-spectrum β-lactamase, hospital Environment. Abstract–Bacteria producing extended-spectrum β-lactamase (ESBL) among clinical isolates have been reported in many countries. However, data concerning the role of environmental contamination in the dissemination of (ESBL)-producing Enterobacteriaceae are currently lacking. In this context, the aim of this study was to investigate and characterise Enterobacteriaceae strains isolated from different places in a hospital and to determine the occurrence of extended-spectrum beta-lactamase (ESBL)-producing Enterobacteriaceae. The bacterial isolates were identified on the basis of standard cultural, morphological and biochemical characteristics. Antibiotic susceptibility of the isolates was tested by disk diffusion method. A total of 637 strains of Enterobacteriaceae were isolated between 2007-2012. Susceptibility study showed that the imipenem was the most active antibiotic against overall enterobacteria with resistance rate of 2.51%, however the high resistance rates were observed to ampicilin (98.11%) and cephalixin (78.65%). The prevalence of ESBL was 136 (21.35%) and ESBL-producing strains were K. pneumoniae 66 (28.45 %), E. coli 31 (25.41%), S. marcescens 18 (19.15%), K. oxytoca 9 (17.31%), En .cloacae 5 (5.43%), C. freundii 04 (16%) and P. mirabilis 03 (15%). ESBL production was confirmed by double disk screening, combination disk method and E-test ESBL strip. All selected isolates harbored from one to four different plasmids with molecular sizes ranging from 5-170 kb. In general, most transconjugants acquired ceftazidime resistance by an ESBL gene encoded on the largest plasmid (>125 kb) found in the respective isolate. In addition, these transconjugants co-expressed other antibiotic resistance markers such as amikacin and ciprofloxacin. INTRODUCTION β-Lactams are considered to be among the safest, most efficacious and most widely prescribed antibiotics for the treatment of bacterial infections. Benzylpenicillin (Penicillin G ) belongs to this class of antibiotic, was the first successful chemotherapeutic agent used during World War II (Abraham, 1977). The use of penicillin was followed by the development of newer antibiotics such cephalosporins and carbapenems for antibiotic resistant infections (Bradford, 2001). Resistance to β-lactams is mediated by four mechanisms; restriction of antimicrobial concentration within the bacterial cell (e.g. via porin loss or active efflux); a decrease in affinity of the β- lactam for the target PBP enzymes; or hydrolysis of the drug by a β-lactamase enzyme (Rupp and Fey, 2003). It has been reported that the appearance of β- lactamases with increased catalytic efficiency for β- lactams seem to be the major resistance mechanism in Gram negative bacteria. However, the combination of increased β-lactamase production with decreased β-lactam concentrations within the periplasm results in perhaps the most effective β- lactam resistance mechanism (Davies and Davies, 2010). Extended-spectrum beta-lactamases (ESBLs) are an increasingly important cause of resistance in Gram-negative bacteria throughout the world. Enterobacteriaceae are significant causes of serious infections and many of the most important members of this family are becoming increasingly resistant to currently available antibiotics. It is important to note