Study on drug resistance and molecular characteristics of Citrobacter

ObjectiveTo investigate the drug resistance, the virulence genes and the pulse field gel electrophoresis (PFGE) patterns of 37 strains of Citrobacter isolated from diarrhea patients and food. MethodsThe Kirby-Bauer disk diffusion test was conducted for Citrobacter isolates to test their resistance to 15 antibiotics; the detection of virulence genes (stx1, stx2, hly and eaeA ) of these isolates was performed by routine PCR assay. Homology analysis was performed by PFGE. ResultsAmong 37 strains of Citrobacter, 25 strains were C. youngae, 11 strains were C. freundii and 1 strain was C. braakii. These Citrobacter isolates were sensitive to most antibiotics, but resistant to cephalothin (100%). The results of virulence genes detection were negative for all the isolates. PFGE analysis revealed that the 37 strains belonged to 29 different patterns. The patterns of 6 strains of C. youngae (5 from food, 1 from patient) were same (MAS007), which had epidemiological link. ConclusionThe predominating strains of Citrobacter was C. youngae in the area surveyed. Some of the Citrobacter isolates were multi-drug resistant. PFGE is effective for the subtyping of ICitrobacter/I strains, which is favorable for the tracing of epidemic source. Diarrhea patients might have food borne infection of ICitrobacter/I, and more attention should be paid to it.