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Salmonella enterica subsp. enterica serovar 4,[5],12:i:- is a monophasic variant of Salmonella Typhimurium. In this study, a total of 651 human and 107 food and environmental isolates of serovar 4,[5],12:i:- recovered from 2007 through 2011 in Switzerland were characterized by antibiotic resistance profiles and pulsed-field gel electrophoresis (PFGE). In addition, a selection of isolates belonging to the most frequent PFGE patterns was further subjected to multilocus variable-number tandem-repeat analysis (MLVA) and phage typing. Over the years 2007-2011, the reports of salmonellosis caused by Salmonella enterica serovar 4,[5],12:i:- significantly increased. A high prevalence of multidrug-resistant isolates, mainly showing an ampicillin-streptomycin-sulfonamide-tetracycline resistance pattern (ASSuT), was observed. In addition, four extended spectrum beta lactamase (ESBL) (CTX-M-55)-producing isolates were found. XbaI PFGE analysis of all isolates revealed over 150 different pulsotypes, and generally showed a considerable diversity within the monophasic isolates. Nevertheless, among these we identified seven dominant profiles, which encompassed 66% of all isolates tested. The PFGE type STYMXB.0131 dominated among human as well as food isolates. Multilocus variable-number tandem-repeat analysis profile 3-12-10-0-0211, which, in many cases, coincided with PFGE type STYMXB.0131 and phage type DT193 were the most prevalent types found for the isolates further characterized by these typing methods. Our data provide strong evidence for a spread of two specific Salmonella serovar 4,[5],12:i:- clones (PFGE pattern STYMXB.0131, resistance type ASSuT) and (PFGE pattern STYMXB.0131, resistance type SSuT). In contrast to the human isolates, the pork/poultry isolates expressed predominantly the SSuT resistance type.

Salmonella enterica serovar Infantis (Salmonella Infantis) is consistently isolated from broiler chickens, pigs, and humans worldwide. This study investigated 93 epidemiologically unrelated Salmonella Infantis strains isolated in Germany between 2005 and 2008 in respect to their transmission along the food chain. Various phenotypic and genotypic methods were applied, and the pathogenicity and resistance gene repertoire was determined. Phenotypically, 66% of the strains were susceptible to all 17 antimicrobials tested, while the others were almost all multidrug-resistant (two or more antimicrobial resistances), with different resistance profiles and preferentially isolated from broiler chickens. A number of phage types (PTs) were shared by strains from pigs, broiler chickens, and humans (predominated by PT 29). One, PT 1, was only detected in strains from pigs/pork and humans. Pulsed-field gel electrophoresis (PFGE) subdivided strains in seven different clusters, named A-G, consisting of 35 various XbaI profiles with coefficient of similarity values of 0.73-0.97. The majority of XbaI profiles were assigned to clusters A and C, and two predominant XbaI profiles were common in strains isolated from all sources investigated. Multi-locus sequence typing (MLST) analysis of selected strains representing the seven PFGE clusters revealed that they all belonged to ST32. The pathogenicity gene repertoire of 37 representative Salmonella Infantis strains analyzed by microarray was also identical. The resistance gene repertoire correlated perfectly with the phenotypic antimicrobial resistance profiles, and multidrug-resistant strains were associated with class 1 integrons. Overall, this study showed that two major closely related genotypes of Salmonella Infantis can transmit in Germany to humans through contaminated broiler meat or pork, and consequently presents a hazard for human health.

This study was conducted to elucidate the accuracy of the current streptomycin epidemiological cut-off value (ECOFF) for Escherichia coli and Salmonella spp. A total of 236 Salmonella enterica and 208 E. coli isolates exhibiting MICs between 4 and 32 mg/L were selected from 12 countries. Isolates were investigated by polymerase chain reaction for aadA, strA, and strB streptomycin resistance genes. Out of 236 Salmonella isolates, 32 (13.5%) yielded amplicons for aadA (n = 23), strA (n = 9), and strB (n = 11). None of the 60 Salmonella isolates exhibiting MIC 4 mg/L harbored resistance genes. Of the Salmonella isolates exhibiting MICs 8 mg/L, 16 mg/L, and 32 mg/L, 1.6%, 15%, and 39%, respectively, tested positive for one or more genes. For most monitoring programs, the streptomycin ECOFF for Salmonella is wild type (WT) ≤32 or ≤16 mg/L. A cut-off value of WT ≤32 mg/L would have misclassified 13.5% of the strains as belonging to the WT population, since this proportion of strains harbored resistance genes and exhibited MICs ≤32 mg/L. Out of 208 E. coli strains, 80 (38.5%) tested positive for aadA (n = 69), strA (n = 18), and strB (n = 31). Of the E. coli isolates exhibiting MICs of 4 mg/L, 8 mg/L, 16 mg/L, and 32 mg/L, 3.6%, 17.6%, 53%, and 82.3%, respectively, harbored any of the three genes. Based on the European Committee on Antimicrobial Susceptibility Testing guidelines (ECOFF ≤16 mg/L), 25% of the E. coli strains presenting MIC ≤16 mg/L would have been incorrectly categorized as belonging to the WT population. The authors recommend an ECOFF value of WT ≤16 mg/L for Salmonella and WT ≤8 mg/L for E. coli.

Objectives: This study was initiated to collect retrospective information on the occurrence of plasmid-mediated quinolone resistance (PMQR) in Salmonella enterica and Escherichia coli isolates in Europe and to identify the responsible genes., Methods: Databases of national reference laboratories containing MIC values for Salmonella and E. coli isolated between 1994 and 2009 in animals, humans, food and the environment from 13 European countries were screened for isolates exhibiting a defined quinolone resistance phenotype, i.e. reduced susceptibility to fluoroquinolones and nalidixic acid. PCR and sequence analysis were performed to identify the responsible PMQR genes., Results: Screening of databases of 13 European countries resulted in a selection of 1215 Salmonella and 333 E. coli isolates. PMQR genes were identified in 59% of the Salmonella isolates and 15% of the E. coli isolates selected. In Salmonella, qnrS1 (n = 125) and variants of qnrB (n = 138) were frequently identified, whereas qnrA1 (n = 3) and aac(6')-1b-cr (n = 3) were rarely found. qnrD was detected in 22 Salmonella isolates obtained from humans and animals. In E. coli, qnrS1 was identified in 19 isolates and qnrB19 was found in one isolate. No qnrC or qepA genes were detected in either Salmonella or E. coli., Conclusions: This study shows the occurrence and dissemination of PMQR genes in Salmonella and E. coli in Europe with a defined quinolone resistance phenotype. We also report the first detection of qnrD in Salmonella collected in Europe.

Objectives: Detection and characterization of extended-spectrum beta-lactamases (ESBLs) and AmpC-encoding genes was conducted in German Salmonella isolated from different sources from 2003 to 2007., Methods: Non-duplicate German isolates from the National Salmonella Reference Laboratory Collection (2003-07) with ceftiofur MICs of > or =4 mg/L were tested for beta-lactam/beta-lactamase inhibitor susceptibility, presence of ESBLs or AmpC-encoding genes, class 1 and 2 integrons, other resistance genes, and IS26 and ISEcp1 sequences by PCR/sequencing. The isoelectric point of the beta-lactamase was determined. Strains were analysed by PFGE and plasmid profiling. The bla genes were mapped by Southern-blot hybridization. Plasmids were characterized by rep-PCR typing., Results: Sixteen isolates (10 Salmonella Typhimurium, 2 Salmonella Anatum, 2 Salmonella Paratyphi B dT + , 1 Salmonella Infantis and 1 Salmonella London) carried bla(CTX-M) (15 bla(CTX-M-1) and one bla(CTX-M-15)) genes located on self-transferable IncB/O, IncI1 and/or IncN plasmids. Seven of the Salmonella Typhimurium isolates carried the SGI1-M variant. Six isolates (five Salmonella Agona and one Salmonella Kentucky) carried the bla(CMY-2) gene on IncI1 conjugative plasmids. bla(TEM-20) genes were detected in two Salmonella Paratyphi B dT+ isolates, and bla(TEM-52) in one Salmonella Paratyphi B dT+ and one Salmonella Virchow, located on IncI1 plasmids. All Salmonella Paratyphi isolates harboured a 2300 bp/dfrA1-sat2-aadA1 class 2 integron., Conclusions: Among the 22 679 German Salmonella isolates investigated, the ESBL and AmpC beta-lactamase prevalence was still low; however, it is slowly increasing. Various beta-lactamase genes are linked to a variety of genetic elements capable of horizontal DNA transfer. Consequently, their dissemination is likely and demands adequate risk management strategies.

Background: The project "Antibiotic resistance in bacteria of animal origin - II" (ARBAO-II) was funded by the European Union (FAIR5-QLK2-2002-01146) for the period 2003-2005, with the aim to establish a continuous monitoring of antimicrobial susceptibility among veterinary laboratories in European countries based on validated and harmonised methodologies. Available summary data of the susceptibility testing of the bacterial pathogens from the different laboratories were collected., Method: Antimicrobial susceptibility data for several bovine pathogens were obtained over a three year period (2002-2004). Each year the participating laboratories were requested to fill in excel-file templates with national summary data on the occurrence of antimicrobial resistance from different bacterial species.A proficiency test (EQAS - external quality assurance system) for antimicrobial susceptibility testing was conducted each year to test the accuracy of antimicrobial susceptibility testing in the participating laboratories. The data from this testing demonstrated that for the species included in the EQAS the results are comparable between countries., Results: Data from 25,241 isolates were collected from 13 European countries. For Staphylococcus aureus from bovine mastitis major differences were apparent in the occurrence of resistance between countries and between the different antimicrobial agents tested. The highest frequency of resistance was observed for penicillin. For Mannheimia haemolytica resistance to ampicillin, tetracycline and trimethoprim/sulphonamide were observed in France, the Netherlands and Portugal. All isolates of Pasteurella multocida isolated in Finland and most of those from Denmark, England (and Wales), Italy and Sweden were susceptible to the majority of the antimicrobials. Streptococcus dysgalactiae and Streptococcus uberis isolates from Sweden were fully susceptible. For the other countries some resistance was observed to tetracycline, gentamicin and erythromycin. More resistance and variation of the resistance levels between countries were observed for Escherichia coli compared to the other bacterial species investigated., Conclusion: In general, isolates from Denmark, England (and Wales), the Netherlands, Norway, Sweden and Switzerland showed low frequencies of resistance, whereas many isolates from Belgium, France, Italy, Latvia and Spain were resistant to most antimicrobials tested. In the future, data on the prevalence of resistance should be used to develop guidelines for appropriate antimicrobial use in veterinary medicine.

Background: The project "Antibiotic resistance in bacteria of animal origin - II" (ARBAO-II) was funded by the European Union (FAIR5-QLK2-2002-01146) for the period 2003-05. The aim of this project was to establish a program for the continuous monitoring of antimicrobial susceptibility of pathogenic and indicator bacteria from food animals using validated and harmonised methodologies. In this report the first data on the occurrence of antimicrobial resistance among bacteria causing infections in pigs are reported., Methods: Susceptibility data from 17,642 isolates of pathogens and indicator bacteria including Actinobacillus pleuropneumoniae, Streptococcus suis and Escherichia coli isolated from pigs were collected from fifteen European countries in 2002-2004., Results: Data for A. pleuropneumoniae from infected pigs were submitted from five countries. Most of the isolates from Denmark were susceptible to all drugs tested with the exceptions of a low frequency of resistance to tetracycline and trimethoprim - sulphonamide. Data for S. suis were obtained from six countries. In general, a high level of resistance to tetracycline (48.0 - 92.0%) and erythromycin (29.1 - 75.0%) was observed in all countries whereas the level of resistance to ciprofloxacin and penicillin differed between the reporting countries. Isolates from England (and Wales), France and The Netherlands were all susceptible to penicillin. In contrast the proportion of strains resistant to ciprofloxacin ranged from 12.6 to 79.0% (2004) and to penicillin from 8.1 - 13.0% (2004) in Poland and Portugal. Data for E. coli from infected and healthy pigs were obtained from eleven countries. The data reveal a high level of resistance to tetracyclines, streptomycin and ampicillin among infected pigs whereas in healthy pigs the frequency of resistance was lower., Conclusion: Bacterial resistance to some antimicrobials was frequent with different levels of resistance being observed to several antimicrobial agents in different countries. The occurrence of resistance varied distinctly between isolates from healthy and diseased pigs, with the isolates from healthy pigs generally showing a lower level of resistance than those from diseased pigs. The study suggests that the choice of antimicrobials used for the treatment of diseased animals should preferably be based on knowledge of the local pattern of resistance.

Objectives: The objectives of this study were to determine antimicrobial susceptibility and to characterize the molecular mechanisms of multidrug resistance among German food-borne Salmonella isolates of different serovars., Methods: A total of 319 epidemiologically independent multidrug-resistant isolates from German foodstuffs comprising 25 different serovars were tested for their antimicrobial susceptibility by broth microdilution. The presence of antimicrobial resistance genes, integrons of classes 1 and 2 and their integrated resistance gene cassettes as well as the Salmonella genomic island 1 (SGI1) was investigated by PCR and DNA sequencing. Localization of integrons and relevant resistance genes was done by Southern hybridization. Sequence analysis revealed mutations in the quinolone resistance-determining region of the gyrA gene., Results: The most prevalent resistances found in the multidrug-resistant serovars of Salmonella enterica from foods were to streptomycin (94%), sulfamethoxazole (92%), tetracycline (81%), ampicillin (73%), spectinomycin (72%), chloramphenicol (48%) and trimethoprim (27%). Twenty-four resistance genes covering six antimicrobial families (beta-lactams, aminoglycosides, phenicols, sulphonamides, tetracycline, and trimethoprim) were identified in the food isolates, many of them integrated as gene cassettes in class 1 and class 2 integrons. Class 1 integrons were detected in 65% of the multidrug-resistant Salmonella isolates comprising 16 different serovars, while class 2 integrons were found in 10% of the isolates belonging to two serovars only. The results demonstrate a clear predominance of both SGI1-borne resistance genes and class 1 integrons in Salmonella serovar Typhimurium DT104 and of class 2 integrons in Salmonella serovar Paratyphi B (d-tartrate positive). Nalidixic acid resistance found in 15% of the isolates was associated with single mutations in the gyrA gene., Conclusions: This study confirms the role of foods of animal and other origin as a reservoir of multidrug-resistant Salmonella and underlines the need for continuing surveillance of food-borne zoonotic bacterial pathogens along the food chain.