Antimicrobial resistance, virulence genes and molecular subtypes of S. Enteritidis isolated from children in Shanghai.

Introduction: Antimicrobial resistance of Salmonella poses a key threat to public health worldwide. Salmonella Enteritidis (S. Enteritidis) (119 isolates) from children under 10 years old with diarrhea in Shanghai from 2010-2012 were characterized for antimicrobial susceptibility, virulence gene profiles and pulsed field gel electrophoresis (PFGE) patterns.

Methodology: The minimum inhibitory concentration for the 119 S. Enteritidis isolates was determined using an agar dilution method. The presence of virulence genes was detected by polymerase chain reaction (PCR). All the isolates with antimicrobial resistance were subjected to PFGE analysis.

Results: Among these isolates, 71.4% (85) were resistant to sulfafurazole, 59.7% (71) were resistant to ampicillin, 47.1% (56) were resistant to streptomycin, 7.6% (9) were resistant to ceftiofur and 3.4% (4) were resistant to ceftriaxone. Multidrug resistance (MDR) was found in 63.9% (76) of the isolates; 23 resistance profiles were identified. All isolates harbored the ssaQ and sopE virulence genes in the 16 virulence profiles (VPs); VP1 accounted for 70.59% of the 119 isolates. There were 57 PFGE patterns among the 92 isolates tested, mainly grouped into five clusters (A to E). All of the 76 MDR isolates carried multiple virulence genes.

Conclusions: Our study provides useful microbiological data for the successful treatment of S. Enteritidis infections in Shanghai. Although broad spectrum antimicrobials may be useful in the treatment of invasive S. Enteritidis infections, clinicians need to be aware of common microbiological traits, because of the high prevalence of MDR.