Etiology of multi-drug resistant Salmonella Kentucky isolates from retail chicken and a patient in Ningbo

Objective To understand the molecular characteristics and drug resistance pattern of Salmonella Kentucky isolated from retail chicken and a diarrhea patient's stool in Ningbo. Methods The S. Kentucky strains were identified with standard serum agglutination method. The susceptibility of the strains to 12 antibiotics was tested by using micro broth dilution method. Pulsed field gel electrophoresis (PFGE)was performed to compare the molecular characteristics of the isolates. PCR was used to detect the drug resistance genes,gyrA,bla_CTX-M14-like,bla_CTX-M15-like,bla_TEM and bla_OXA. Results Two strains of S. Kentucky isolated from different sources were all resistant to 9 antibiotics and multi-drug resistant Salmonella. The PFGE finger printing of the 2 isolates digested by 2 enzymes (XbaⅠ and BlnⅠ)were exactly the same. The quinolone-resistant gene gyrA contained mutations at codon 83 and 87,with substitutions of serine to phenylalanine and aspartate to glycine, respectively. The extended spectrum β-lactamases phenotype determining genes bla_CTX-M14-like,bla_CTX-M15-like and bla_TEM were all positive,while bla_OXA was negative. Conclusion Super ciprofloxacin resistant S. Kentucky strain was detected from retail chicken and a diarrhea patient's stool in Ningbo,which shared the same PFGE pattern,indicating the multi-drug resistant S. Kentucky had caused a sporadic case. Surveillance for super ciprofloxacin resistant S. Kentucky should be performed in the poultry farm and healthy population. More strict supervision should be carried out for rational use of antibiotics in the poultry farms to prevent multi-drug resistant of Salmonella.