Characteristics of extended-spectrum cephalosporin-resistant Escherichia coli isolated from Swiss and imported poultry meat.

A worrisome phenomenon is the progressive global spread of Enterobacteriaceae in poultry and chicken meat expressing plasmid-mediated enzymes that inactivate ß-lactam antibiotics, suggesting that the food chain might play a role in the epidemiology and the transmission of extended-spectrum cephalosporin-resistant Enterobacteriaceae to humans. The aim of the present study was to further characterize 24 extended-spectrum cephalosporin-resistant Enterobacteriaceae isolated from domestic and imported poultry meat by antibiotic susceptibility testing, identification of the blaESBL/blapAmpC genes, conjugation mating experiments and determination of plasmid incompatibility types, multilocus sequence typing, and analysis of the Escherichia coli phylogenetic groups. On account of their resistance patterns, 21 of the total 24 isolates were classified as multidrug resistant. Eleven isolates carried a blaCMY-2 gene, whereas 13 isolates harbored a blaCTX-M-1 gene. All isolates harbored plasmids that were assigned to 8 of the 18 described plasmid incompatibility groups, the most frequent of which were IncI1, IncFIB, IncB/O, and IncFrepB. The blaESBL/blapAmpC genes were harbored mainly by transferable IncI1 and IncB/O plasmids. Multilocus sequence typing as well as E. coli phylogenetic group typing revealed a high heterogenicity even among different isolates of the same sample.

Diarrheagenic enteroaggregative Escherichia coli causing urinary tract infection and bacteremia leading to sepsis.

We report a case of a 55-year-old immunocompromised female who presented to the emergency department with severe diarrhea and vomiting following travel to the Philippines. Stool bacteriology revealed a mixed infection involving an enteropathogenic Escherichia coli and two distinct strains of enteroaggregative Escherichia coli (EAEC). During hospitalization, urine and blood culture tested positive for one of the diarrheagenic EAEC strains, necessitating urinary catheterization, intensive care, and antimicrobial treatment with trimethoprim-sulfamethoxazole, followed by meropenem. Although known to occasionally cause urinary tract infections, EAEC have not been previously associated with sepsis. Our report highlights the potential of EAEC to cause severe extraintestinal infections.

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

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 ß-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.

Outbreak of listerosis due to imported cooked ham, Switzerland 2011.

From 24 April to 31 July 2011, nine cases of listeriosis were registered in the cantons of Aargau, Basel-Land and Zurich, Switzerland. In six of the cases, infection with Listeria monocytogenes was laboratory confirmed, while three remained suspected cases. The suspected cases were family members of confirmed cases with identical or similar symptoms. All confirmed cases were infected with a L. monocytogenes strain belonging to serovar 1/2a: all had an indistinguishable pulsotype by pulsed-field gel electrophoresis (PFGE). The same strain was detected in samples of cooked ham that were on sale from a particular retailer. Two samples of ham tested contained 470 and 4,800 colony-forming units (CFU) L. monocytogenes per gram respectively. Data of shopper cards from two confirmed cases could be evaluated: both cases had purchased the contaminated ham. The outbreak initiated a product recall and alert actions at national and European level, through the Rapid Alert System for Food and Feed (RASFF). Following the RASFF alert, the company producing the contaminated ham was inspected by the responsible authorities. Their investigations showed that the ham was not contaminated in the production plant, but in the premises of a company to which slicing and packing was outsourced.

Search for magnetic monopoles in polar volcanic rocks.

For a broad range of values of magnetic monopole mass and charge, the abundance of monopoles trapped inside Earth would be expected to be enhanced in the mantle beneath the geomagnetic poles. A search for magnetic monopoles was conducted using the signature of an induced persistent current following the passage of igneous rock samples through a SQUID-based magnetometer. A total of 24.6 kg of rocks from various selected sites, among which 23.4 kg are mantle-derived rocks from the Arctic and Antarctic areas, was analyzed. No monopoles were found, and a 90% confidence level upper limit of 9.8 × 10(-5)/g is set on the monopole density in the search samples.

Epidemic of salmonellosis in passerine birds in Switzerland with spillover to domestic cats.

A die-off of passerine birds, mostly Eurasian siskins (Carduelis spinus), occurred in multiple areas of Switzerland between February and March 2010. Several of the dead birds were submitted for full necropsy. Bacteriological examination was carried out on multiple tissues of each bird. At gross examination, common findings were light-tan nodules, 1 to 4 mm in diameter, scattered through the esophagus/crop. Histologically, a necroulcerative transmural esophagitis/ingluvitis was observed. Bacterial cultures yielded Salmonella enterica subsp. enterica serovar Typhimurium. At the same time, 2 pet clinics reported an unusual increase of domestic cats presented with fever, anorexia, occasionally dolent abdomen, and history of presumed consumption of passerine birds. Analysis of rectal swabs revealed the presence of S. Typhimurium in all tested cats. PFGE (pulsed field electrophoresis) analysis was performed to characterize and compare the bacterial isolates, and it revealed an indistinguishable pattern between all the avian and all but 1 of the feline isolates. Cloacal swabs collected from clinically healthy migrating Eurasian siskins (during autumn 2010) did not yield S. Typhimurium. The histological and bacteriological findings were consistent with a systemic infection caused by S. Typhimurium. Isolation of the same serovar from the dead birds and ill cats, along with the overlapping results of the PFGE analysis for all the animal species, confirmed a spillover from birds to cats through predation. The sudden increase of the number of siskins over the Swiss territory and their persistency during the whole winter of 2009-2010 is considered the most likely predisposing factor for the onset of the epidemic.

Discovery of extended-spectrum beta-lactamase producing Escherichia coli among hunted deer, chamois and ibex.

The aim of the present study was to assess for the first time the dissemination of extended-spectrum beta-lactamase (ESBL) producing Escherichia coli in the wild animal ecosystem in Switzerland. Fecal samples of 84 red deer, 64 roe deer, 64 chamois, and 27 ibex were investigated. One sample from a roe deer tested positive for ESBL-producing E. coli. The isolate harboured blaCTX-M-1 and tested negative for both blaTEM and blaSHV. Based on these results low occurrence of ESBL-producing Enterobacteriaceae in the wild animal ecosystem in Switzerland must currently be postulated. Further studies are necessary to assess future trends.

Yersinia enterocolitica strains associated with human infections in Switzerland 2001-2010.

Yersinia enterocolitica infections are common in humans. However, very scarce data are available on the different biotypes and virulence factors of human strains, which has proved to be problematic to assess the clinical significance of the isolated strains. In this study, the presence of the ail gene and distribution of different bio- and serotypes among human Y. enterocolitica strains and their possible relation to the genotype and antimicrobial resistance were studied. In total, 128 Y. enterocolitica strains isolated from human clinical samples in Switzerland during 2001-2010 were characterised. Most (75 out of 128) of the Y. enterocolitica strains belonged to biotypes 2, 3 or 4 and carried the ail gene. One of the 51 strains that belonged to biotype 1A was also ail positive. Most of the ail-positive strains belonged to bioserotype 4/O:3 (47 out of 76) followed by 2/O:9 (22 out of 76). Strains of bioserotype 4/O:3 were dominant among patients between 20 and 40 years old and strains of biotype 1A dominate in patients over 40 years. Strains belonging to biotypes 2, 3 and 4, which all carried the ail gene, exhibited a high homogeneity with PFGE typing. Y. enterocolitica 2/O:5,27 and 2/O:9 strains showed resistance to amoxicillin/clavulanic acid and cefoxitin, but Y. enterocolitica 4/O:3 strains did not.

Comparison of genotypes and antibiotic resistance of Campylobacter jejuni isolated from humans and slaughtered chickens in Switzerland.

AIMS: To get an overview of genotypes and antibiotic resistances in Swiss Campylobacter jejuni implicated in human gastroenteritis and to examine the association with isolates from chickens. METHODS AND RESULTS: Multilocus sequence typing (MLST) and flaB typing were applied to 136 human clinical isolates. Phenotypic resistance to 12 antimicrobials and genotypic resistance to macrolides and quinolones were determined. MLST resulted in 35 known and six new sequence types (ST). The flaB analysis revealed 35 different types, which - in combination with MLST - increased the resolution of the typing approach. Resistance to quinolones, tetracycline and ampicillin was found in 37·5, 33·1 and 8·1% of the isolates, respectively, whereas macrolide resistance was found only once. Genotypic and phenotypic resistance correlated in all cases. A comparison to Camp. jejuni isolated from slaughtered chickens was performed. While 86% of the quinolone-sensitive human isolates showed overlapping MLST-flaB types with those of chicken origin, resistant strains showed only 39% of matching types. CONCLUSION: Mainly quinolone-sensitive Camp. jejuni strains implicated in human campylobacteriosis showed matching genotypes with isolates originating from chickens. SIGNIFICANCE AND IMPACT OF THE STUDY: A large proportion of human cases in Switzerland are likely to originate from domestic chickens, confirming that prevention measures in the poultry production are important.

Shiga toxin-producing Escherichia coli O157 associated with human infections in Switzerland, 2000-2009.

Shiga toxin-producing Escherichia coli (STEC), an important foodborne pathogen, can cause mild to severe bloody diarrhoea (BD), sometimes followed by life-threatening complications such as haemolytic uraemic syndrome (HUS). A total of 44 O157 strains isolated from different patients from 2000 through 2009 in Switzerland were further characterized and linked to medical history data. Non-bloody diarrhoea was experienced by 15.9%, BD by 61.4% of the patients, and 29.5% developed HUS. All strains belonged to MLST type 11, were positive for stx2 variants (stx2 and/or stx2c), eae and ehxA, and only two strains showed antibiotic resistance. Of the 44 strains, nine phage types (PTs) were detected the most frequent being PT32 (43.2%) and PT8 (18.2%). By PFGE, 39 different patterns were found. This high genetic diversity within the strains leads to the conclusion that STEC O157 infections in Switzerland most often occur as sporadic cases.

In vitro inhibition activity of different bacteriocin-producing Escherichia coli against Salmonella strains isolated from clinical cases.

AIMS: To compare in vitro the inhibitory activity of four bacteriocin-producing Escherichia coli to a well-characterized panel of Salmonella strains, recently isolated from clinical cases in Switzerland. METHODS AND RESULTS: A panel of 68 nontyphoidal Salmonella strains was characterized by pulsed-field gel electrophoresis analysis and susceptibility to antibiotics. The majority of tested strains were genetically different, with 40% resistant to at least one antibiotic. E. coli Mcc24 showed highest in vitro activity against Salmonella (100%, microcin 24), followed by E. coli L1000 (94%, microcin B17), E. coli 53 (49%, colicin H) and E. coli 52 (21%, colicin G) as revealed using a cross-streak activity assay. CONCLUSIONS: Escherichia coli Mcc24, a genetically modified organism producing microcin 24, and E. coli L1000, a natural strain isolated from human faeces carrying the mcb-operon for microcin B17-production, were the most effective strains in inhibiting in vitro both antibiotic resistant and sensitive Salmonella isolates. SIGNIFICANCE AND IMPACT OF THE STUDY: Due to an increasing prevalence of antibiotic resistant Salmonella strains, alternative strategies to fight these foodborne pathogens are needed. E. coli L1000 appears to be a promising candidate in view of developing biotechnological alternatives to antibiotics against Salmonella infections.

Imported aseptic meningitis due to Toscana virus acquired on the island of Elba, Italy, August 2008.

We describe a case of aseptic meningitis due to Toscana Virus imported to Switzerland and discuss the epidemiological situation. To our knowledge this is the first description of this infection acquired on the Island of Elba.

Outbreak of Salmonella enterica serovar Typhimurium in Switzerland, May-June 2008, implications for production and control of meat preparations.

An increased number of Salmonella Typhimurium cases were reported in Switzerland between May and June 2008. Investigations involved 72 cases. Results of PFGE typing identified several outbreak strains, the dominating one present in 43 of the 72 isolates. Strains affecting one third of the cases were also found in animal samples, in particular pork. However, no specific food source could be identified. Outbreaks described in this paper highlight the importance of food safety regulations such as those on minced meat and meat preparations issued by the European Commission and adopted by Switzerland into the national law.

Outbreak of Salmonella serovar Stanley infections in Switzerland linked to locally produced soft cheese, September 2006 - February 2007.

Salmonella serovar Stanley is rare in Europe. In Switzerland, the number of reported isolates has increased from 2 in 2000 to 25 in 2005. A nationwide outbreak of gastrointestinal illness due to S. Stanley occurred from September 2006 through February 2007. Eighty-two cases were documented. Males were 56%; mean age of the cases was 45.7 years (range 0-92). Forty-seven cases (57%) occurred in three western cantons: Vaud, Bern, and Geneva. Twenty-three cases (28%) were hospitalised. In the case-control study conducted to find the source of the outbreak, cases were more likely than controls to have eaten local soft cheese (OR 11.4, p=0.008). One clone of S. Stanley strain was isolated from soft cheese and from 77 cases (94%) who reported no history of having travelled abroad. The outbreak ended after the withdrawal of the cheese from the market. This is the first S. Stanley outbreak in Switzerland and the first in Europe unrelated to imported products, suggesting an increased local circulation of this previously rare serotype.

Development of an oligonucleotide microarray method for Salmonella serotyping.

Adequate identification of Salmonella enterica serovars is a prerequisite for any epidemiological investigation. This is traditionally obtained via a combination of biochemical and serological typing. However, primary strain isolation and traditional serotyping is time-consuming and faster methods would be desirable. A microarray, based on two housekeeping and two virulence marker genes (atpD, gyrB, fliC and fljB), has been developed for the detection and identification of the two species of Salmonella (S. enterica and S. bongori), the five subspecies of S. enterica (II, IIIa, IIIb, IV, VI) and 43 S. enterica ssp. enterica serovars (covering the most prevalent ones in Austria and the UK). A comprehensive set of probes (n = 240), forming 119 probe units, was developed based on the corresponding sequences of 148 Salmonella strains, successfully validated with 57 Salmonella strains and subsequently evaluated with 35 blind samples including isolated serotypes and mixtures of different serotypes. Results demonstrated a strong discriminatory ability of the microarray among Salmonella serovars. Threshold for detection was 1 colony forming unit per 25 g of food sample following overnight (14 h) enrichment.

MLST-v, multilocus sequence typing based on virulence genes, for molecular typing of Salmonella enterica subsp. enterica serovars.

Salmonella enterica subsp. enterica is one of the main causative agents of food-borne disease in man, and can also be the cause of serious systemic illness. Organisms belonging to this genus have traditionally been classified on the basis of the antigenic properties of the cell-surface lipopolysaccharide and of the phase 1 and phase 2 flagellar proteins. Primary isolation, biochemical identification, and serotyping are laborious and time consuming. Molecular identification based on suitable marker genes could be an attractive alternative to conventional bacteriological and serological methods. We have assessed the applicability of two housekeeping genes, gyrB, atpD, in combination with the flagellin genes fliC and fljB in multilocus sequence typing of Salmonella. Sequencing and comparative analysis of sequence data was performed on multiple strains from Austria, the United Kingdom, and Switzerland, representing all subspecies and 22 of the more prevalent non-typhoid S. enterica subsp. enterica serovars. A combination of these four marker genes allowed for a clear differentiation of all the strains analysed, indicating their applicability in molecular typing. The term MLST-v, for multilocus sequence typing based on virulence genes, is proposed to distinguish this approach from MLST based solely on housekeeping genes. An assortative recombination of the fliC gene was found in seven of the analysed serovars indicating multiple phylogenetic origin of these serovars.

Molecular epidemiology of extended-spectrum beta-lactamases from Klebsiella pneumoniae strains isolated in Zagreb, Croatia.

In order to assess the molecular epidemiology of 40 previously identified extended-spectrum beta-lactamase (ESBL)-producing clinical isolates of Klebsiella pneumoniae, gene sequencing was performed. While the previous examination of these isolates revealed one TEM producer, the sequencing procedure performed in this study identified 13 additional TEM producers, and all of the sequenced genes reflected production of nonESBL TEM-1. All 38 suspected SHV producers were confirmed to be carriers of blaSHV-ESBL genes using the PCR/Nhel test and sequencing. Among them, types SHV-2, SHV-5, and SHV-12 were found in 20, 10, and 7 isolates, respectively, and SHV-2a was identified in 1. SHV-5 and SHV-12 conferred higher resistance to ceftazidime and cefepime, while SHV-2 and SHV-2a raised the minimum inhibitory concentrations of cefotaxime and cefpirome. Fourth-generation cephalosporins were found to be more active against the isolates than third-generation cephalosporins.

Amino acid substitutions causing inhibitor resistance in TEM beta-lactamases compromise the extended-spectrum phenotype in SHV extended-spectrum beta-lactamases.

Three amino acid substitutions, Met-69-->Ile, Arg-244-->Ser and/or Asn-276-->Asp, mediate inhibitor resistance (IR) in TEM beta-lactamases. They were introduced in all possible combinations at homologous positions into either SHV-1 or the respective extended-spectrum beta-lactamases (ESBLs), SHV-2 or SHV-5. Susceptibility testing of the resulting set of seven variants of each parental strain, all in an isogenic background, was performed. The phenotypes of the constructions revealed that most substitutions resulted in reduced resistance to most tested single beta-lactam formulations. This decrease over-compensated for the expected increase in inhibitor resistance, so that most mutants showed no rise in resistance to inhibitor/beta-lactam combinations, although increases of MICs from one- to 43-fold compared with the respective parental strains were also measured. Combination of several IR-determining substitutions impaired both phenotypes in the carrier strains even more. None of the 14 mutants derived from the ESBLs, SHV-2 and SHV-5, showed a clinically relevant combined ESBL-IR phenotype. These findings indicate that the SHV beta-lactamase does not benefit proportionally from simultaneous substitution of residues relevant for the ESBL and the IR phenotype.