Antimicrobial resistance and genetic diversity of Salmonella Infantis isolated from foods and human samples in Morocco.

OBJECTIVES

Genotyping of Salmonella strains is an important molecular tool to discriminate isolates and to improve epidemiological studies when an outbreak occurs. Among the DNA-based genotyping methods, pulsed-field gel electrophoresis (PFGE) is currently used to subtype Salmonella isolates. In this study, the feasibility of genotyping Salmonella enterica serotype Infantis strains using XbaI restriction enzyme was evaluated. Separation of restricted fragments was performed by PFGE.

METHODS

To test the possibility of applying this methodology to epidemiological investigation, a collection of 26 Salmonella Infantis strains were tested for their susceptibility to 14 antimicrobial agents and were analysed by XbaI macrorestriction followed by PFGE. Detection of class 1 integrons as well as intI1 and blaTEM genes in resistant strains was also studied.

RESULTS

Antimicrobial susceptibility testing showed that 84.6% (22/26) of Salmonella Infantis isolates were susceptible to all of the antimicrobials tested, whereas 7.7% (2/26) had low-level resistance to β-lactams and harboured the blaTEM gene. A class 1 integron (0.8kb) and the intI1 gene (898bp) were detected in one Salmonella Infantis strain. However, five different PFGE profiles were defined by XbaI macrorestriction.

CONCLUSIONS

The PFGE method demonstrated adequate typing ability and represents a powerful tool to discriminate the serotype Salmonella Infantis.