Drug resistance and virulence-associated genes screening in Salmonella enterica isolated from Caspian pony, Iran

Abstract

The most serious problem in public health is salmonellosis, a common disease in horse. The aim of this study was to investigate the shedding of Salmonella serotypes in healthy Caspian pony. We examined 143 pony's fecal samples collected from the north of Iran belonging to different ages and sexes. Samples were cultured, then identification of isolates were performed by common bacteriological methods and polymerase chain reaction (PCR). The PCR was also used to explore the presence of fimA and salmonella secreted effector L (SseL) genes as virulence factors in the isolates and all were assigned to antibiotic susceptibility test via disc diffusion method. Results showed two fecal samples (1.39%) contaminated with Salmonella and further examination demonstrated the isolates belonging to S. enterica serotype typhimurium. Both serotypes were isolated from female and ˂6 years of age group of ponies and we detected fimA and SseL genes in the isolates. Observing multiple drug resistance and virulence genes in isolates is of utmost importance from both clinical and public health perspectives. It is highly likely that we face instances of salmonellosis in animals or humans that lead to severe infections and fail to respond to treatment in future. This study revealed that the occurrence of Salmonella was low in ponies, however, regarding the presence of virulence factors with multidrug resistant trend in this zoonotic bacterium, establishment of good hygienic measurement to prevent the transmission of bacteria between animal and human is necessary.

Keywords: Antibiotic resistance; Caspian pony; Salmonella; Virulence gene.

Fig. 1

The studied area (highlighted) and its location regarding Iran map.

Fig. 2

Agarose gel image of amplified fragment of 16S rRNA of Salmonella enterica (671 bp); M: 50-bp DNA ladder. Lane 1: Positive control, lane 2: Negative control, and lanes 3 - 4: Positive samples for 16S rRNA.

Fig. 3

Agarose gel image of amplified fragment of A) fimA gene (85 bp). M: 50-bp DNA ladder, lanes 1 - 2: Positive samples, lane 3: Positive control and lane 4: Negative control for fimA, and B) SseL gene (637 bp). M: 50-bp DNA ladder, lane 1: Positive control, lane 2: Negative control, and lane: 3 - 4: Positive samples for salmonella secreted effector L (SseL).