Shiga toxin-producing Escherichia coli isolated from hunted wild boar (Sus scrofa) in Switzerland.

INTRODUCTION: Shiga toxin-producing Escherichia (E.) coli (STEC) are zoonotic foodborne pathogens of significant public health importance. While ruminants are considered the main reservoir, wild animals are increasingly acknowledged as carriers and potential reservoirs of STEC. The aim of this study was to determine the occurrence of STEC in a total of 59 faecal samples of hunted wild boars (Sus scrofa) from two different regions in Switzerland (canton Thurgau in northern Switzerland and canton Ticino in southern Switzerland), and to characterise the isolates using a whole genome sequencing approach. After an enrichment step, Shiga-toxin encoding genes (stx) were detected by real-time PCR in 41 % (95 % confidence interval (95 %CI) 0,29 - 0,53) of the samples, and STEC were subsequently recovered from 22 % (95 %CI 0,13 - 0,34) of the same samples. Seven different serotypes and six different sequence types (STs) were found, with O146:H28 ST738 (n = 4) and O100:H20 ST2514 (n = 4) predominating. Subtyping of stx identified isolates with stx1c/stx2b (n = 1), stx2a (n = 1), stx2b (n = 6), and stx2e (n = 6). No isolate contained the eae gene, but all harboured additional virulence genes, most commonly astA (n = 10), hlyE (n = 9), and hra (n = 9). STEC O11:H5, O21:H21, and O146:H28 harboured virulence factors associated with extra-intestinal pathogenic E. coli (ExPEC), and STEC O100:H20 and O155:H26 possessed sta1 and/or stb and were STEC/enterotoxigenic E. coli (ETEC) hybrid pathotypes. Our results show that wild boars are carriers of STEC which may be distributed in the environment, possibly leading to the contamination of agricultural crops and water sources. The serogroups included STEC O146 which belongs to the most common non-O157 serogroups associated with human illness in Europe, with implications for public health. Since Stx2e-producing STEC have frequently been reported in swine and pork, STEC O100:H20 harbouring stx2e in faeces of wild boars may be relevant to free-range systems of pig farming because of the potential risk of transmission events at the wildlife-livestock interface.

INTRODUCTION: Les Escherichia (E.) coli producteurs de shiga-toxine (STEC) sont des agents pathogènes zoonotiques d'origine alimentaire qui revêtent une grande importance pour la santé publique. Alors que les ruminants sont considérés comme le principal réservoir, les animaux sauvages sont de plus en plus souvent reconnus comme porteurs et réservoirs potentiels de STEC. L'objectif de cette étude était de déterminer la présence de STEC dans un total de 59 échantillons fécaux de sangliers (Sus scrofa) chassés provenant de deux régions différentes de Suisse (canton de Thurgovie dans le nord de la Suisse et canton du Tessin dans le sud de la Suisse) et de caractériser les isolats en utilisant une approche de séquençage du génome entier. Après une étape d'enrichissement, les gènes codant pour la Shiga-toxine (stx) ont été détectés par PCR en temps réel dans 41% (intervalle de confiance à 95% (95%CI) 0,29 - 0,53) des échantillons, et les STEC ont ensuite été récupérés dans 22% (95%CI 0,13 - 0,34) des mêmes échantillons. Sept sérotypes différents et six types de séquence (ST) différents ont été trouvés, avec une prédominance de O146:H28 ST738 (n = 4) et O100:H20 ST2514 (n = 4). Le sous-typage des stx a permis d'identifier des isolats avec stx1c/stx2b (n = 1), stx2a (n = 1), stx2b (n = 6) et stx2e (n = 6). Aucun isolat ne contenait le gène eae, mais tous hébergeaient d'autres gènes de virulence, le plus souvent astA (n = 10), hlyE (n = 9) et hra (n = 9). Les STEC O11:H5, O21:H21 et O146:H28 présentaient des facteurs de virulence associés à des E. coli pathogènes extra-intestinaux (ExPEC), et les STEC O100:H20 et O155:H26 possédaient sta1 et/ou stb et étaient des pathotypes hybrides STEC/E. coli entérotoxinogène (ETEC).

Characteristics of ESBL-producing Enterobacteriaceae and Methicillinresistant Staphylococcus aureus (MRSA) isolated from Swiss and imported raw poultry meat collected at retail level.

INTRODUCTION: This study was conducted to investigate the occurrence and genetic characteristics of extended spectrum ß-lactamase (ESBL) and methicillin-resistant Staphylococcus aureus (MRSA) in 80 samples of Swiss (n=36) and imported (n=44) raw chicken meat collected at retail level. In addition, ESBL-producers were screened for the presence of the plasmid-mediated colistin resistance gene mcr-1. Countries of import included Argentina (n=2), Austria (n=1), Brazil (n=3), Denmark (n=5), France (n=1), Germany (n=13), Hungary (n=5), Italy (n=8), and Slovenia (n=6). Forty ESBL-producing E. coli strains were isolated from 33 (41.3%) of the 80 samples, comprising seven (19.4%) of the Swiss and 26 (59%) of the imported samples. The most common blaESBL among the isolates were blaCTX-M-1 (n=14) and blaSHV-12 (n=16). Other genes comprised blaTEM-52 (n=4), blaCTX-M-2 (n=3), blaCTX-M-8 (n=1), blaCTX-M-14 (n=1) and a novel blaCTX-M-14-like variant (n=1). Two ESBL-producers isolated from samples from Germany (n=1) and Italy (n=1) tested additionally positive for the plasmid-mediated colistin resistance gene mcr-1. Six (7.5%) samples, all imported from Germany, were found to contain MRSA. Three isolates belonged to the livestock-associated CC398-MRSA-V-t034, and 3 to CC9-MRSA-IV-t13177, described here for the first time in chicken meat.

INTRODUCTION: Dans le cadre de la présente étude, on a examiné au total 80 échantillons de viande de volaille crue quant à la présence d'entérobactéries productrices de bétalactamase avec spectre élargi (ESBL) ainsi que de Staphylococcus aureus résistants à la méthicilline (MRSA). En outre les germes producteurs d'ESBL ont été examinés quant à la présence du gène mcr-1. La viande provenait de Suisse (n=36) ainsi que d'Argentine (n=2), d'Autriche (n=1), du Brésil (n=3), du Danemark (n=5), de France (n=1), d'Allemagne (n=13), de Hongrie (n=5), d'Italie (n=8) et de Slovénie (n=6). Au total, 33 échantillons (41.3%) contenaient des entérobactéries producteurs d'ESBL, 7 d'entre eux (19.4%) provenant de viandes suisses et 26 (59%) de viandes importées. Les variantes de gènes les plus fréquentes étaient blaCTX-M-1 (n=14) et blaSHV-12 (n=16) suivis par blaTEM-52 (n=4) blaCTX-M-2 (n=3), blaCTX-M-8 (n=1), blaCTX-M-14 (n=1) ainsi que par une nouvelle variante blaCTX-M-14 (n=1). Sur deux germes producteurs d'ESBL isolés sur des échantillons provenant d'Allemagne (n=1) et d'Italie (n=1), on a trouvé en outre le gène mcr-1 qui code la résistance vis-à-vis de la colistine. Six échantillons (7.5%), provenant tous d'Allemagne, étaient positifs aux MRSA. La génotypisation a permis d'en classer trois dans le clone associé aux animaux de rente CC398-MRSA-V-t034 et les trois autre dans le clone CC9-MRSA-IV-t13177. Ce dernier est décrit pour la première fois dans ce travail comme associé à des échantillons de viande de volaille.

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.

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.

Survey and molecular genetics of SHV beta-lactamases in Enterobacteriaceae in Switzerland: two novel enzymes, SHV-11 and SHV-12.

Sixty isolates of Enterobacteriaceae resistant to beta-lactam antibiotics were collected over a period of 2 years in Switzerland and screened by hybridization for the carriage of SHV genes. Thirty-four positive strains were found, and their SHV genes were amplified and sequenced. SHV extended-spectrum beta-lactamases (ESBLs) were found: 13 strains contained SHV-2a, 12 harbored SHV-2, and SHV-5 was found twice. Four strains were shown to contain SHV-1. In addition, we report two new SHV variants, termed SHV-11 (non-ESBL) and SHV-12 (ESBL). In spite of the carriage of SHV ESBLs, many strains showed only low resistance to one or more third-generation cephalosporins. In addition, 26 did not transfer the blaSHV gene in mating experiments.

Detection of genes coding for extended-spectrum SHV beta-lactamases in clinical isolates by a molecular genetic method, and comparison with the E test.

A highly sensitive and specific method, termed PCR/NheI, for the detection of genes coding for SHV extended-spectrum beta-lactamases (ESBL) in clinical isolates is presented. It is based on polymerase chain reaction (PCR) amplification of the blaSHV genes, followed by restriction with NheI. Due to the glycine (positive 238) (SHV-non-ESBL)-->serine (position 238) (SHV-ESBL) mutation, only PCR fragments from the genes coding for SHV-ESBLs were cleaved. A commercially available test for ESBLs, the E test ESBL, identified 52% of our 29 clinical isolates carrying blaSHV-ESBL genes as ESBL producers.

New system based on site-directed mutagenesis for highly accurate comparison of resistance levels conferred by SHV beta-lactamases.

We developed a system based on site-directed mutagenesis that allows a precise comparison of SHV enzymes under isogenic conditions. In addition, the influences of two different, naturally occurring promoters were examined for each SHV derivative. The system comprised two separately cloned DNA fragments, each the size of 3.6 kb. Both fragments encoded an SHV gene originating from clinical isolates but with different promoters. The structural genes were made identical by site-directed mutagenesis. Other mutations were then introduced into both fragments by means of site-directed mutagenesis, resulting in the SHV derivatives SHV-1, SHV-2, SHV-2a, SHV-3, and SHV-5. The amino acid exchange of glutamic acid at position 235 for lysine in SHV-5 resulted in the highest resistance levels. SHV-3, differing from SHV-2 by the exchange of arginine at position 201 for leucine and previously described as indistinguishable from SHV-2, was shown to cause slightly higher resistance to ceftazidime and lower resistance to ceftriaxone, cefotaxime, and cefepime than SHV-2. The point mutation in SHV-2a, with the leucine-to-glutamine replacement at the unusual position 31, previously considered almost insignificant, proved to increase resistance to ceftazidime but reduced the MICs of all other cephalosporins tested when compared with those for SHV-2. For all clones harboring SHV derivatives, resistance was increased by a stronger promoter, in some cases masking the effect of the point mutation itself and demonstrating the importance of regulatory mechanisms of resistance.