Epidemiology and Infection

Original Papers

Gastroenteritis/water

Antimicrobial resistance patterns and genotypes of Salmonella enterica serovar Hadar strains associated with human infections in Switzerland, 2005–2010

N. CERNELAa1, M. NÜESCH-INDERBINENa1, H. HÄCHLERa1 and R. STEPHANa1 c1

a1 Institute for Food Safety and Hygiene, Vetsuisse Faculty, University of Zurich, Zurich, Switzerland

SUMMARY

Salmonella Hadar ranks in the top ten serovars reported from humans in Switzerland. In this study, all 64 S. Hadar strains isolated from different patients from 2005 to 2010 in Switzerland were characterized by (i) assessing phenotypic antimicrobial resistance profiles using the disk diffusion method and (ii) by genotyping using pulsed-field gel electrophoresis (PFGE) in order to evaluate the relationship of the strains. The annual incidences varied between 0·32/100 000 in 2005 (highest incidence) and 0·065/100 000 in 2007 (lowest incidence). In total 71·8% of the isolates were resistant to nalidixic acid. Although 40·6% of the strains were resistant to the β-lactam antibiotic ampicillin, they remained susceptible to the third-generation cephalosporin cefotaxime. Genotyping revealed a primary cluster consisting of 42 strains, sharing a similarity of >92%, with a subcluster of 18 strains with indistinguishable patterns. Resistance profiles allowed further differentiation within this subcluster providing a link of two strains to an outbreak in Spain.

(Received September 03 2012)

(Revised January 29 2013)

(Accepted February 12 2013)

(Online publication April 16 2013)

Key words

  • genotypes;
  • human infections;
  • resistance profiles;
  • Salmonella Hadar

Correspondence

c1 Author for correspondence: Professor R. Stephan, Institute for Food Safety and Hygiene, Vetsuisse Faculty University of Zurich, Winterthurerstr. 272, CH-8057 Zurich, Switzerland. (Email: stephanr@fsafety.uzh.ch)

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