ABSTRACT
Salmonella spp. is an important zoonotic pathogen related to foodborne diseases. Despite that quinolones/fluoroquinolones are considered a relevant therapeutic strategy against resistant isolates, the increase in antimicrobial resistance is an additional difficulty in controlling bacterial infections caused by Salmonella spp. Thus, the acquisition of resistance to quinolones in Salmonella spp. is worrisome to the scientific community along with the possibility of transmission of resistance through plasmids. This study investigated the prevalence of plasmid-mediated quinolone resistance (PMQR) in Salmonella spp. and its association with fluoroquinolone susceptibility in Brazil. We evaluated 129 isolates, 39 originated from food of animal sources, and 14 from environmental samples and including 9 from animals and 67 from humans, which were referred to the National Reference Laboratory of Enteric Diseases (NRLEB/IOC/RJ) between 2009 and 2013. These samples showed a profile of resistance for the tested quinolones/fluoroquinolones. A total of 33 serotypes were identified; S. Typhimurium (63) was the most prevalent followed by S. Enteritidis (25). The disk diffusion test showed 48.8% resistance to enrofloxacin, 42.6% to ciprofloxacin, 39.53% to ofloxacin, and 30.2% to levofloxacin. According to the broth microdilution test, the resistance percentages were: 96.1% to nalidixic acid, 64.3% to enrofloxacin, 56.6% to ciprofloxacin, 34.1% to ofloxacin, and 30.2% to levofloxacin. Qnr genes were found in 15 isolates (8 qnrS, 6 qnrB, and 1 qnrD), and the aac(6')-Ib gene in 23. The integron gene was detected in 67 isolates with the variable region between ±600 and 1000 bp. The increased detection of PMQR in Salmonella spp. is a serious problem in Public Health and must constantly be monitored. Pulsed-field gel electrophoresis was performed to evaluated clonal profile among the most prevalent serovars resistant to different classes of quinolones. A total of 33 pulsotypes of S. Typhimurium were identified with a low percentage of genetic similarity (≤65%). This result demonstrates the presence of high diversity in the resistant clones evaluated in this study.
ABSTRACT
Antimicrobial resistance was evaluated for 12,582 strains of Salmonella isolated by public and private laboratories from commercial poultry carcasses and poultry products from different regions in Brazil between 2007 and 2011. These isolates were submitted unsolicited to the National Reference Laboratory for Bacterial Enteroinfections, Oswaldo Cruz Institute, Oswaldo Cruz Foundation, Rio de Janeiro, Brazil, for conclusive antigenic characterization. The prevalent Salmonella enterica serogroups were O:4 (B) (28.9%), O:9 (D1) (22.3%), O:21 (L) (15.9%), and O:7 (C1) (14.3%); the most prevalent serovars were Enteritidis, Minnesota, Typhimurium, Schwarzengrund, and Mbandaka. The antimicrobial susceptibility profiles of 1,234 strains indicated that 54.5% were resistant to up to eight antimicrobial drugs. Multidrug resistance (three or more classes) was observed in 16.4% of the strains, with 190 distinct patterns. The results showed increased resistance to ampicillin (12.4 to 18.9%), tetracycline (≈ 15.2 to ≈ 18.9%), and gentamicin (f7.0 to ≈ 9.6%) during the study period. Decreased resistance to nitrofurans (61.9 to 9.2%), quinolones (44.4 to 15.5%), and folate inhibitors (11.7 to 7.2%) was observed. Resistance to third-generation cephalosporins was detected in 5.5% of the strains throughout the study period; resistance to fluoroquinolones has been observed in 0.3% of the strains since 2009. These findings highlight the importance of surveillance along the food chain for detection of altered patterns among foodborne zoonotic bacteria that are important to public health.
