Molecular characterization and antibiotic resistance of salmonella serovars isolated in the Apulia region of Italy

Abstract

During the period January 2013-December 2015, 175 cases of human salmonellosis were reported in the Apulia Region of Italy. The aim of this study was to characterize salmonella strains from the standpoints of serovars prevalence, antimicrobial resistance and clonal origin. The serological typing was performed by agglutination against antisera followed by a multiplex polymerase chain reaction (m-PCR). The obtained results were analyzed following the Kauffmann-White scheme. Susceptibility to antimicrobial agents was tested using the disk diffusion method on Muller-Hinton agar plates. All strains were tested by pulsed-field gel electrophoresis (PFGE) according to the PulseNet protocol, and cluster analysis was performed using BioNumerics software. It was found that the most prevalent isolated serovars were in order: i) S.Enteritidis, ii) S.Typhimurium and iii) S. 4,[5],12:i:–. The most common resistances were: i) Ampicillin (A) (38%), ii) Amoxicillin/Clavulanic Acid (AmC) (11%), iii) Streptomycin (S) (19%), iv) Sulphonamides (Su) (19%), v) Tetracycline (T) (30%), and vi) Piperacillin (Pip) (25%). Ten multidrugresistant (MDR) patterns were identified among the isolates, and the two most diffused ones were ASSuT and ASSuTPip, respectively. MDR patterns were predominantly expressed by Salmonella Typhimurium and Salmonella 4,[5],12:i:-. Molecular typing by PFGE yielded 60 different macrorestriction profiles among 33 serotypes.