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Objectives: This study aimed to compare ESBL-producing Escherichia coli causing infections in humans with infecting or commensal isolates from animals and isolates from food of animal origin in terms of the strain types, the ESBL gene present and the plasmids that carry the respective ESBL genes., Methods: A collection of 353 ESBL-positive E. coli isolates from the UK, the Netherlands and Germany were studied by MLST and ESBL genes were identified. Characterization of ESBL gene-carrying plasmids was performed using PCR-based replicon typing. Moreover, IncI1-Iγ and IncN plasmids were characterized by plasmid MLST., Results: The ESBL-producing E. coli represented 158 different STs with ST131, ST10 and ST88 being the most common. Overall, blaCTX-M-1 was the most frequently detected ESBL gene, followed by blaCTX-M-15, which was the most common ESBL gene in the human isolates. The most common plasmid replicon type overall was IncI1-Iγ followed by multiple IncF replicons., Conclusions: ESBL genes were present in a wide variety of E. coli STs. IncI1-Iγ plasmids that carried the blaCTX-M-1 gene were widely disseminated amongst STs in isolates from animals and humans, whereas other plasmids and STs appeared to be more restricted to isolates from specific hosts., (© The Author 2016. Published by Oxford University Press on behalf of the British Society for Antimicrobial Chemotherapy. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.)

Objectives: The characterization of CTX-M-₁₅ β-lactamase-producing Escherichia coli and Salmonella isolates originating mainly from German livestock and food., Methods: E. coli (526, mainly commensals) and Salmonella (151) non-human isolates resistant to third-generation cephalosporins, originating from routine and monitoring submissions (2003-12) to the Federal Institute for Risk Assessment and different national targeted studies (2011-12), were examined for the presence of blaCTX-M-₁₅ genes by PCR amplification/sequencing. Additional resistance and virulence genes were screened by DNA microarray and PCR amplification. E. coli isolates with blaCTX-M-₁₅ were characterized by phylogenetic grouping, PFGE and multilocus sequence typing (MLST). The blaCTX-M-15 plasmids were analysed by replicon typing, plasmid MLST, S1 nuclease PFGE and Southern blot hybridization experiments., Results: Twenty-one E. coli (livestock, food and a toy; 4.0%) and two Salmonella (horse and swine; 1.3%) isolates were CTX-M-₁₅ producers. E. coli isolates were mainly ascribed to three clonal lineages of sequence types ST678 (German outbreak with enteroaggregative Shiga-toxin-producing E. coli O104:H4; salmon, cucumber and a toy), ST410 (poultry, swine and cattle farms) and ST167/617 (swine farms and turkey meat). The blaCTX-M-₁₅ genes were located on IncI1 and multireplicon IncF plasmids or on the chromosome of E. coli ST410 isolates., Conclusions: The prevalence of CTX-M-₁₅-producing isolates from non-human sources in Germany is still low. The blaCTX-M-₁₅ gene is, however, present in multidrug-resistant E. coli clones with pathogenic potential in livestock and food. The maintenance of the blaCTX-M-₁₅ gene due to chromosomal carriage is noteworthy. The possibility of an exchange of CTX-M-₁₅-producing isolates or plasmids between livestock and humans (in both directions) deserves continuous surveillance., (© The Author 2014. Published by Oxford University Press on behalf of the British Society for Antimicrobial Chemotherapy. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.)

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.

Objectives: The aim of this study was to generate baseline data on the prevalence and molecular basis of antimicrobial resistance in Escherichia coli O111 isolates., Methods: A total of 105 epidemiologically unrelated E. coli O111 isolates from humans and cattle (isolated between 1983 and 2003) were tested for susceptibility to 17 antimicrobial agents by broth microdilution. Resistant isolates were screened by molecular methods for resistance genes, class 1 and 2 integrons and mutations in the quinolone-resistance determining regions., Results: Resistance was found in 76% of the isolates, with a prevalence of 72% for multiresistance. The most prevalent resistances were to streptomycin, sulfamethoxazole and tetracycline (72-68%), followed by spectinomycin, ampicillin and kanamycin/neomycin (39-25%). For each antimicrobial agent, the predominant resistance genes were ampicillin, bla(TEM) (94%); chloramphenicol, catA1 (100%); gentamicin, aac(3)-IV and aac(3)-II (50% each); kanamycin, aphA1 (100%); streptomycin, aadA1- like (66%); sulfamethoxazole, sul1 (59%); tetracycline, tet(A) (86%); and trimethoprim, dfrA1-like (83%). Class 1 integrons were found in 41% of the isolates. They carried aadA1, dfrA1-aadA1 and dfrA15-aadA1. A class 2 integron (dfrA1-sat1-aadA1) was found in one isolate. Only three isolates (3%) were resistant to nalidixic acid (reduced susceptibility to ciprofloxacin), with a single mutation in the gyrA gene., Conclusions: E. coli O111 strains exhibit a wide repertoire of genetic elements to sustain antimicrobial pressure. Two specific antimicrobial resistance pheno/genotypes, [STR-SPT]-SUL-TET/aadA1-sul1-tet(A) and STR-SUL-TET-AMP-[KAN-NEO]/strA/B-sul2-tet(A)-bla(TEM)-aphA1, are predominant.

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.

Objective: Phenotypic and genotypic characterization of the antimicrobial resistance of German Escherichia coli strains isolated during 1999-2001 from cattle, swine and poultry., Materials and Methods: Three hundred and seventeen isolates were tested for their resistance to 17 antimicrobial agents by broth microdilution. Resistant strains were screened by molecular methods for resistance genes, integrons and mutations in quinolone-resistance determining regions., Results: Resistance was found in 40% and multiresistance in 32% of the strains. The resistance was significantly higher in isolates from poultry (61%) and swine (60%) than from cattle (25%) (P < 0.01). The most prevalent resistances were to sulfamethoxazole, tetracycline, streptomycin, ampicillin and spectinomycin (30-15%). For each antibiotic, the predominant resistance genes were: ampicillin, blaTEM1-like (92%); chloramphenicol, catA (68%) and cmlA1-like (36%); gentamicin, aac(3)-IV (60%); kanamycin, aphA1 (100%); streptomycin, aadA1-like (61%) and strA/B (59%); sulfamethoxazole, sul2 (66%), sul1 (42%) and sul3 (14%); tetracycline, tet(A) (66%) and tet(B) (42%); and trimethoprim, dfrA1-like (77%), dfrA17 (13%) and dfrA12 (7%). Class 1 integrons were found in 30% of the strains. They carried dfrA1-aadA1a (40%), aadA1a (29%), sat1-aadA1a (16%), dfrA17-aadA5 (11%), oxa1-aadA1a (5%) and dfrA12-aadA2 (3%). Eleven percent of the strains were resistant to nalidixic acid. Of these, 61% presented a reduced susceptibility to ciprofloxacin (MIC = 0.12-2 mg/L) and single mutations in gyrA or gyrA and parC genes, and 39%, full resistance to ciprofloxacin (MIC > or = 4 mg/L) and double and single mutations in gyrA and parC, respectively., Conclusion: The study gives baseline information on the magnitude of the resistance problem and its genetic background in contemporary German E. coli from food-producing animals.