Genetic characterization of clinical and agri-food isolates of multi drug resistant Salmonella enterica serovar Heidelberg from Canada

Abstract

BackgroundSalmonella enterica serovar Heidelberg ranks amongst the most prevalent causes of human salmonellosis in Canada and an increase in resistance to extended spectrum cephalosporins (ESC) has been observed by the Canadian Integrated Program for Antimicrobial Resistance Surveillance. This study examined the genetic relationship between S. Heidelberg isolates from livestock, abattoir, retail meat, and clinical human specimens to determine whether there was a link between the emergence of MDR S. Heidelberg in chicken agri-food sources and the simultaneous increase of MDR S. Heidelberg in human clinical samples.ResultsChromosomal genetic homogeneity was observed by pulsed-field gel electrophoresis (PFGE), DNA sequence-based typing (SBT) and DNA microarray-based comparative genomic hybridization (CGH). Sixty one percent of isolates were indistinguishable by PFGE conducted using XbaI and BlnI restriction enzymes. An additional 15% of isolates had PFGE patterns that were closely related to the main cluster. SBT did not identify DNA polymorphisms and CGH revealed only genetic differences between the reference S. Typhimurium strain and S. Heidelberg isolates. Genetic variation observed by CGH between S. Heidelberg isolates could be attributed to experimental variation. Alternatively, plasmid content was responsible for differences in antimicrobial susceptibility, and restriction fragment length polymorphism (RFLP) analyses followed by replicon typing identified two divergent plasmid types responsible for ESC resistance.ConclusionDue to the overall limited genetic diversity among the isolates, it was not possible to identify variable traits that would be suitable for source tracking between human and agri-food isolates of S. Heidelberg in Canada.

Occurrence of spvA Virulence Gene and Clinical Significance for Multidrug-Resistant Salmonella Strains

“…The absence of an association between pentaresistance R-types (ACSSuT and AKSSuT) and the origin of isolates is consistent with previous reports that MDR strains of Salmonella may also be found very commonly in pigs with no apparent clinical symptoms (1,12). On the other hand, the MDR pattern of AKSSuT was most often detected from nonclinical specimens of porcine origin but was extremely rare among clinical samples both from pigs and from humans.…”

Resistance Plasmid Families in Enterobacteriaceae

“…In addition, failure to identify AmpC ␤-lactamase producers may lead to inappropriate antimicrobial treatment and may result in increased mortality (88). Dissemination of organisms that produce CMY, an AmpC that originated from the chromosome of Citrobacter freundii, has been linked to specific plasmid families that are recurrent in isolates from animal sources (1,73,113).…”

First Report of New Delhi Metallo-Beta-Lactamase-1-ProducingKlebsiella pneumoniaein Iran

“…Detection of extended spectrum b-lactamase and MBLs genes by PCR Genomic DNAs were extracted by the standard phenolchloroform method as described by Andrysiak et al 2 The detection of extended spectrum b-lactamase (ESBL) genes was carried out by PCR with specific primers to detect bla TEM , bla SHV, bla CTX-M , bla PER , and bla VEB genes as previously described. 1,4,13,29 K. pneumoniae strain 7881 and P. aeruginosa, KOAS strain were used as the control strain in the detection of these genes.…”