Salmonellosis in broiler flocks of Golestan province: frequency, serogroups and drug resistance patterns of Salmonella isolates

The use of antibiotics in food animal production systems has resulted in emergence of antibiotic resistant zoonotic bacteria such as Salmonella that can be transmitted to humans through the food chain. This survey was done to determine Salmonella contamination and to evaluate Salmonella drug resistance in broiler flocks as one of the most important sources of food in Golestan province. In this survey, samples were taken from 52 broiler farms (85 broiler houses) at different ages and, in total, 510 pooled manure samples were collected. Standard cultural method was performed for Salmonella isolation. The serogroup of each isolate was determined by using polyvalent and monovalent Salmonella antisera. The occurrence and the level of antimicrobial resistance patterns in Salmonella isolates were determined by disk diffusion method. Fourteen Salmonella were isolated from 510 pooled samples (2.74%). There was occurrence rate 16.47% in 85 houses. Three isolates belonged to group D, 9 isolates belonged to group C and 2 isolates did not belong to serogroups A to D. Thirteen different patterns of resistance were found. All of the isolates (100%) were sensitive to ceftriaxone and cefixime and resistant to nalidixic acid, flumequine, chlortetracycline, tylosin, erythromycin and doxycycline. Multiple resistances to at least four antimicrobial drugs were observed in all isolates. The highest resistance rate was found against most prevalent drugs in poultry industry reinforcing this hypothesis that wide usage of drugs results in the emergence of drug resistant bacteria.