Tracing the source of blaCTX-M-15 producing ST34 Salmonella typhimurium isolated from feces and wound secretion

Background: Salmonella enterica serovar typhimurium infection is common in food-borne diseases, isolating it from surgical incisions is rare. The aim of this study was to trace the transmission source of a surgical incision infected with Salmonella typhimurium in a Yunnan Province hospital patient and elucidate the underlying molecular mechanisms of antibiotic resistance. Methods Primers were designed to amplify the drug resistant genes by polymerase chain reaction (PCR). Susceptibility to antibiotics was determined using Etest. The identical macrorestriction profiles were analyzed by pulsed field gel electrophoresis (PFGE) using XbaI. The two isolates were characterized using an agglutination test and multilocus sequence typing (MLST). Results The MLST analysis revealed that isolates SM043 and SM080 belonged to the same genotype ST34, and the PFGE revealed that SM043 and SM080 had high similarity. The two S. typhimurium strains SM043 and SM080 were resistant to third generation cephalosporins. SM043 harbored blaCTX-M-15 , blaTEM-1 , qnrS-1 , qnrB , and acc-3 resistance genes, while blaCTX-M-15 , blaTEM-1 , blaCMY-2 , qnrS-1 , and acc-3 were detected in SM080. Conclusions The source of the surgical incision infection by S. typhimurium may be a hospital-derived transmission. Thus, it is critical to strengthen hospital sanitation by addressing hand hygiene and sterilization of the overall operational environment to avoid outbreaks of Salmonella nosocomial infections.