Frequency, Serovars and antibiotic resistant pattern of Salmonella spp. isolated from sheep in Golestan province, Iran

Back ground and Salmonella spp., genus of gram-negative rodshaped bacteria of the family enterobacteriaceae, are one of the most common bacteria can be transmitted from animals to humans and because of their wide range of reservoirs and transmission by feces origin, is one of the most important and commonest zoonotic disease. Salmonella spp. are able to cause severe gastroenteritis, sepsis and occasionally death in humans and livestock. Farm animals such as sheep and goats which are one of the important food sources for humans, can be potential reservoirs of zoonotic Salmonella spp. Although, antibiotic resistance in Salmonella spp. is an emerging problem during the last decades. The ultimate objective of this study was to determine shedding frequency of Salmonella spp in fecal samples of healthy sheep, serotype and antimicrobial resistance pattern of isolated Salmonella spp in rural flocks of Golestan Province.
A total of 120 fecal samples were directly obtained from rectum of apparently healthy sheep. Salmonella contamination of sampled fecal was surveyed by microbial culture and polymerase chain reaction (PCR) assay using primers of the Salmonella inv A gene. Serotype and antibiotic resistant pattern of detected salmonella were determined too. The statistical analysis was performed using SPSS, version 20, values were tested for statistical significance using chi-square test and P value of 0.05 or less was considered significant.
Out of the total 120 examined animals, 20 (16.6%) and 22 (18.3%) were Salmonella spp. carriers by microbial culture and PCR, respectively. In spite of higher detection rate of salmonella with PCR than microbial culture, the difference wasn’t significant (P˃0.05). In this study, all positive microbial culture results were confirmed with PCR. Serotype of isolates included: 13 (65%) S. enteritidis and 7 (35%) S. typhimurium. Salmonella contamination rate was similar in male and female sheep. Highest Salmonella shedding was observed in autumn. The highest rate of resistance was against Ciprofloxacin (75%), Tetracycline (60%) and Streptomycin (60%). Also results of the current study indicated that Furazolidone is a good antibiotics showing high activity against isolated Salmonella spp.
The results of this study confirm the role of sheep as potential Salmonella carriers so it is suggested that caution should be exercised in sheep growth and consumption of foods which are obtained from sheep in rural areas. Overall, the obtained results emphasize the need for a surveillance and monitoring system to emerge drug resistance in pathogenic bacteria in ruminant and other animals.