Detection of virulence and antibacterial resistance genes in Salmonella isolates from diarrhoeic dogs in Iran

This study investigated the presence of some virulence and antibacterial resistance genes in Salmonella isolates from diarrhoeic dogs in Iran. Seventy diarrhoeic dogs presented to the Islamic Azad University Veterinary Teaching Hospital (IAUVTH), Iran, were sampled purposively. Rectal swabs were collected and cultured for isolation and identification of Salmonella using standard biochemical and serotyping methods. Polymerase chain reaction (PCR) was used to detect 3 virulence genes: invA, invF and sitC; and 12 antibacterial resistance genes which encode for resistance to beta-lactam (bla(CMY-2) and bla(CMY-9)), tetracycline (tetA and tetB), trimethoprim (dhfrI and dhfrII), aminoglycosides (aac(3)-Ia and aac(3)-IIa), sulfonamide (sulI and sulII), and chloramphenicol (cat1 and cat2). Of 70 rectal swabs cultured, 13 (18.6%) were positive for Salmonella. Of the 13 positive samples/isolates, all (100%) were positive for invA while 3 (23.1%) were positive for invF. None of the isolates was positive for sitC. Out of the 13 isolates, 11 (84.6%) were positive for antibacterial resistance genes while 2 (15.4%) were negative for all the tested resistance genes. Of the 11 positive isolates, 7(63.6%) were positive for bla(CMY-2) and bla(CMY-9), 4 (36.4%) for aac(3)-Ia and aac(3)-IIa), 8 (72.7%) for tetA and tetB, 3 (27.3%) for dhfrI, dhfrII, sul1 and sul2 while 1 (9.1%) of the isolates was positive for cat1 and cat2. The isolates exhibited 5 multidrug resistant genotype patterns. Three (27.3%) of the isolates exhibited bla(CMY-2) + bla(CMY-9) + tetA+tetB, bla(CMY-2) + bla(CMY-9) + aac(3)-Ia+aac(3)IIa and tetA+tetB+dhfrI+dhfrII+sul1+sul2 patterns while 1 (9.1%) of the isolates exhibited bla(CMY-2) + bla(CMY-9) + aac(3)-Ia+aac(3)-IIa+tetA+tetB and tetA+tetB+cat1+cat2 patterns. This study has shown that salmonellae associated with canine diarrhoea in Iran habours several virulence and antibacterial resistance genes.