[Serotype distribution and antimicrobial susceptibilities of Salmonella strains recovered from environmental samples...

Despite the measures taken and control applications worldwide, Salmonella infections continue to threat the public health. Since these infections also cause significant economical loss, the salmonellas continue to be forefront globally. The determination of Salmonella serotypes and their sources is important for epidemiological point of view. In this study, serotype distribution and antimicrobial resistance of environmental isolates of Salmonella spp. recovered from the poultry farms, that were send for confirmation and serotyping between seven years period, 2008-2014, were evaluated. Strains isolated from environmental samples that were sent to Public Health Institute, Department of Microbiology Reference Laboratory, National Reference Laboratory for Enteric Pathogens, were inoculated onto Salmonella-Shigella and Xylose Lysine Desoxycholate agar and evaluated after 18-24 hours of incubation at 37°C. The identification of the strains was performed by using standard biochemical tests from the suspected colonies. Strains compatible with Salmonella spp. were serotyped using polyvalent and monovalent Salmonella O and H antisera by slide agglutination method. Antibiotic susceptibility tests were performed and evaluated according to CLSI recommendation using Kirby-Bauer disk diffusion method. In our study, a total of 2011 Salmonella strains were evaluated and 15 different serogroups and 75 different serotypes were identified. The most common Salmonella serotypes were S.Infantis (30.6%), followed by S.Enteritidis (21.8%), S.Typhimurium (6.5%), S.Kottbus (5.2%), S.Tennessee (4.3%), S.Mbandaka (4.1%), S.Indiana (3.9%), S.Kentucky (3%), S.Corvallis (2.5%), S.Paratyphi B (1.9%) and S.Hadar (1.7%). Among the isolates, 50.1% (1008/2011) were found susceptible to all of the tested antimicrobials. The rate of isolates that were resistant to only one drug was found to be 15.6%, whereas 30.9% of the strains showed multi-drug resistance (resistant to ≥ 3 antimicrobial drugs). Antimicrobial resistance rates of the Salmonella strains were as follows; nalidixic acid 35.9%, tetracycline 30%, sulfonamides 27.5%, trimethoprim 25.6%, trimethoprim/sulfamethoxazole 25.4%, streptomycin 23.4% and ampicillin 13.5%, respectively. The highest resistance rates for streptomycin (91.4%) ampicillin (88.6%) and tetracycline (88.6%) were observed in S.Hadar strains; for sulfonamide (82.2%) and trimethoprim/sulfamethoxazole (78.2%) in S.Infantis strains, and for nalidixic acid in S.Indiana (97.4%), S.Hadar (91.4%) and S.Infantis (88.8%) strains. In conclusion, the origins, serotypes and antibiotic susceptibility patterns of the strains should be defined for the management of Salmonella infections which are still today a global problem.