Antimicrobial resistance in Salmonella spp. recovered from patients admitted to six different hospitals in Tehran, Iran from 2007 to 2008

The objective of this study was to assess the genotypic diversity associated with antimicrobial susceptibility of Salmonella serovars isolated from patients arriving with diarrhoea to six hospitals of Tehran, Iran. During 2007-2008, a cross-sectional convenience study was performed. Stool samples were screened for the presence of Salmonella, serotyped, tested for antimicrobial susceptibility using disk diffusion and examined for the presence of relevant resistance genes and integrons by PCR. A total of 1,120 patients were screened for the presence of Salmonella. Out of 71 Salmonella isolates recovered, the following serovars were identified: 17 Typhi, 14 Paratyphi C, 13 Enteritidis, 11 Paratyphi B, 10 Paratyphi A and six Infantis. Most resistance was observed towards sulfamethoxazole (30%), tetracyclines (25%), nalidixic acid (22%), spectinomycin (17%), trimethoprim (15%), ampicillin (14%) and kanamycin (14%). The tetracycline resistance genes tet(A), tet(B), and tet(G) were found in 28%, 14% and 6% of the tetracycline resistant isolates, respectively. The genes aadA, aadB, strA, strB and aphA1-Iab were present in 83%, 55%, 34%, 1% and 17% of the aminoglycoside resistant isolates, respectively. Additionally, bla(PSE) and bla(TEM) beta-lactamase genes were detected in 63% and 18% of the ampicillin-resistant isolates. The 23 sulphonamide resistant isolates harboured sul1 and intI1 genes, typical to class 1 integrons. Nine of these isolates also yielded amplicons for intI2 (class 2 integrons). The presence of multi-drug resistant Salmonella may compromise the successful treatment of enteric infection diseases. The enforcement of strict prescription practices will help to minimise the emergence of resistance.