Molecular characterization of multidrug resistant Salmonella from chicken and human in Yaounde

Abstract

Salmonella is one of the most common foodborne pathogens worldwide and chicken has been recognized as its main reservoir for human. The aim of this study was to investigate the occurrence of antimicrobial resistance genes in Salmonella isolates from chicken and human, and evaluate their genetic relationship. A total of 200 Salmonella strains (103 from Chicken and 97 from humans) were collected from 2006 to 2007 in Yaounde, and characterized for their antimicrobial susceptibility to a panel of 16 antimicrobials. Presence of antimicrobial resistance genes, class1 and class 2 integrons was investigated by PCR in Multidrug Resistant (MDR) isolates. Pulsed-Field Gel Electrophoresis (PFGE) analysis was used to investigate their genetic relatedness. Only serotypes Enteritidis, Hadar, Bareilly and II were recovered from both chicken and human. Overall, 16 isolates (8%) were susceptible to all antimicrobials including third generation cephalosporins and fluoroquinolons. Resistance was mostly observed to tetracycline (57%) in chicken isolates and to sulfonamides (78.3%) in human isolates. 78 (15.3%) strains were MDR. Class 1 integron was predominant in MDR Hadar and Typhimurium isolates. TEM-1 was the unique Extended Spectrum β-lactamase (ESBL) detected in the β-lactam resistant Typhimurium strain isolated from human. No qnr genes were identified in nalidixic acid resistant isolates. PFGE typing of Enteritidis isolates using XbaI restriction enzyme showed close genetic relationship between chicken and human isolates. For Hadar and Typhimurirum, variety of restriction patterns was observed. These results highlight the need for continuous surveillance of antimicrobial resistance in Salmonella isolates in Cameroon.