Salmonella entericaserotype Virchow associated with human infections in Switzerland: 2004-2009

Abstract

BackgroundSalmonellosis is one of the most important foodborne diseases and a major threat to public health. Salmonella serotype Virchow ranks among the top five serovars in Europe.MethodA total of 153 strains isolated from different patients from 2004 through 2009 in Switzerland were further characterized by (i) assessing phenotypic antibiotic resistance profiles using the disk diffusion method and (ii) by genotyping using pulsed-field gel electrophoresis (PFGE) after macrorestriction with XbaI in order to evaluate strain relationship.ResultsThe relative frequency of S. Virchow among other Salmonella serovars varied between 4th to 8th rank. The annual incidence ranged from 0.45/100'000 in 2004 to 0.40/100'000 in 2009. A total of 48 strains (32%) were resistant to one to 3 antimicrobials, 54 strains (36%) displayed resistance patterns to more than three antibiotics. No trend was identifiable over the years 2004 to 2009. We found a high prevalence (62%) of nalidixic acid resistant strains, suggesting an equally high rate of decreased fluoroqionolone susceptibility, whereas intermediate resistance to ciprofloxacin was negligible. Two strains were extended spectrum β-lactamase (ESBL) producers. Analysis of PFGE patterns uncovered a predominant cluster (similarity coefficient above 80%) consisting of 104 of the 153 strains.ConclusionThe worldwide increase of antibiotic resistances in Salmonella is an emerging public health problem. For Switzerland, no clear trend is identifiable over the years 2004 to 2009 for S. Virchow. Antimicrobial susceptibility and resistance profiles varied considerably within this period. Nevertheless, the situation in Switzerland coincided with findings in other European countries. Genotyping results of this strain collection revealed no evidence for an undetected outbreak within this time period.

Salmonella enterica serotype Kentucky associated with human infections in Switzerland: Genotype and resistance trends 2004–2009

“…2) (see Section 3.4 below) but were relatively consistent within those clusters, in that most of the MDR strains belonged either to cluster A or C, whereas strains within cluster B and D displayed either MR or full susceptibility. A similar correlation between MDR and PFGE clusters has already been reported with S. Virchow from Switzerland (Bonalli et al, 2011).…”

“…This hypothesis was supported by a similar recent study on S. Virchow in Switzerland (Bonalli et al, 2011). The incidence among people between 15 and 65 years (incidence: 0.23/100000) was three fold higher than that among children aged 6 to 14 years (incidence: 0.07/100000).…”

Quinolone Resistance Mechanisms in Salmonella enterica Serovars Hadar, Kentucky, Virchow, Schwarzengrund, and 4,5,12:i:−, Isolated from Humans in Switzerland, and Identification of a Novel qnrD Variant, qnrD2 , in S . Hadar

“…As all but two (N05-2379 and N0-2461) of the isolates belong to a large cluster found to be disseminated internationally (10), this suggests that S. Virchow maintains a highly established quinolone target gene resistance genotype. Interestingly, this serovar contained three of the four detected plasmid-mediated resistance genes (two qnrS1 genes and one qnrB2 gene).…”

“…Interestingly, this serovar contained three of the four detected plasmid-mediated resistance genes (two qnrS1 genes and one qnrB2 gene). Isolates N06-978 and N07-0090 harboring qnrS2 plasmids belong, together with a qnrS2-harboring S. Virchow isolate described previously (6), to a subcluster associated with travel to Thailand (10).…”

Complete nucleotide sequence of pVQS1 containing a quinolone resistance determinant from Salmonella enterica serovar Virchow associated with foreign travel

“…1 In the years 2004-09 in Switzerland, Salmonella Virchow ranked between the top four to eight serovars and the percentage of nalidixic acid resistance among these reached 62%. 2 Resistance to quinolones and fluoroquinolones in enteric bacteria develops mainly through target gene mutations in the type II (DNA gyrase) and type IV DNA topoisomerases. However, a number of plasmid-mediated quinolone resistance (PMQR) markers have been reported.…”