Multilocus sequence typing and virulence factors analysis of Escherichia coli O157 strains in China

Pons M. Antimicrobial resistance and associated risk factors in Escherichia coli isolated from Peruvian dogs: A focus on extended-spectrum β-lactamases and colistin

Background and Aim

Established antimicrobial resistance (AMR) surveillance in companion animals is lacking, particularly in low-middle-income countries. The aim of this study was to analyze AMR and its risk factors in Escherichia coli isolated from dogs at two veterinary centers in Lima (Peru).

Materials and Methods

Ninety dogs were included in the study. Antimicrobial susceptibility was established by disk diffusion, whereas microdilution was used to determine colistin susceptibility. Mechanisms related to extended-spectrum β-lactamases (ESBL) and colistin resistance were determined by polymerase chain reaction. Clonal relationships of colistin-resistant isolates were assessed by XbaI-pulsed-field gel electrophoresis.

Results

Thirty-five E. coli strains were isolated. High levels of resistance to ampicillin (57.1%), nalidixic acid (54.3%), tetracycline (48.6%), and azithromycin (25.7%) were detected. Cephalosporin resistance levels were ≥20% and those for colistin were 14.3%. Twelve (34.2%) isolates were ESBL producers; of these, six blaCTX-M-55 (50.0%), 2 (16.6%) blaCTX-M-15, and 2 (16.6%) blaCTX-M-8-like genes were found. The five colistin-resistant isolates were clonally unrelated, with four of them presenting amino acid codon substitutions in the mgrB gene (V8A) or mutations in the mgrB promoter (a12g, g98t, and c89t). Furthermore, dog age, <6 years (p = 0.027) and raw diet (p = 0.054) were associated with resistance to a greater number of antibiotic families.

Conclusion

Despite small number of samples included, the study found that dogs studied were carriers of multidrug-resistant E. coli, including last-resort antimicrobials, representing a public health problem due to close contact between dogs and humans. This issue suggests the need for larger studies addressed to design strategies to prevent the spread of resistant micro-organisms in small animal clinics and domestic settings.

Traditional marketed meats as a reservoir of multidrug-resistant Escherichia coli

This study aimed to analyze Escherichia coli from marketed meat samples in Peru. Sixty-six E. coli isolates were recovered from 21 meat samples (14 chicken, 7 beef), and antimicrobial resistance levels and the presence of mechanisms of antibiotic resistance, as well as clonal relationships and phylogeny of colistin-resistant isolates, were established. High levels of antimicrobial resistance were detected, with 93.9% of isolates being multi-drug resistant (MDR) and 76.2% of samples possessing colistin-resistant E. coli; of these, 6 samples from 6 chicken samples presenting mcr-1-producer E. coli. Colistin-resistant isolates were classified into 22 clonal groups, while phylogroup A (15 isolates) was the most common. Extended-spectrum β-lactamase- and pAmpC-producing E. coli were found in 18 and 8 samples respectively, with blaCTX-M-55 (28 isolates; 16 samples) and blaCIT (8 isolates; 7 samples) being the most common of each type. Additionally, blaCTX-M-15, blaCTX-M-65, blaSHV-27, blaOXA-5/10-like, blaDHA, blaEBC and narrow-spectrum blaTEM were detected. In addition, 5 blaCTX-M remained unidentified, and no sought ESBL-encoding gene was detected in other 6 ESBL-producer isolates. The tetA, tetE and tetX genes were found in tigecycline-resistant isolates. This study highlights the presence of MDR E. coli in Peruvian food-chain. The high relevance of CTX-M-55, the dissemination through the food-chain of pAmpC, as well as the high frequency of unrelated colistin-resistant isolates is reported.

First Isolation and Molecular Characterization of bla CTX-M-121 -Producing Escherichia coli O157:H7 From Cattle in Xinjiang, China

The bovine Escherichia coli O157:H7 is a major foodborne pathogen causing severe bloody diarrhea, hemorrhagic colitis, and hemolytic uremic syndrome in humans. Cattle are recognized major reservoir and source of E. coli O157:H7. We investigated the antibiotic resistance, molecular profiles, and intrinsic relationship between 21 isolates of E. coli O157:H7 from cattle farms and slaughtering houses in Xinjiang. Using pulsed-field gel electrophoresis (PFGE) molecular typing, two types of PFGE were revealed through cluster analysis, including clusters I and II, with 66 and 100% similarity of PFGE spectra between 21 isolates. We also detected that 18 isolates (86%) carried at least one virulence gene, 16 isolates (76%) carried the eae gene, and 7 (33%) carried the stx1 + stx2 + eae + hly + tccp genes. Eighteen isolates were susceptible to antibiotics. Three isolates were resistant to antibiotics, and two were multidrug resistant. One of the two multidrug-resistant isolates detectably carried the bla CTX-M-121 gene. This is the first finding of the bla CTX-M-121 gene detected in E. coli O157:H7 isolated from cattle in Xinjiang. The bla CTX-M-121 gene is transferable between the bacterial strains via plasmid transmission. The results indicated that E. coli O157:H7 may have undergone clonal propagation in cattle population and cross-regional transmission in Xinjiang, China.

Multilocus-based phylogenetic analysis of extended-spectrum beta-lactamase Escherichia coli O157:H7 uncovers related strains between agriculture and nearby water sources

This study aimed to uncover related strains of extended-spectrum beta-lactamase Escherichia coli O157:H7 between agricultural matrices (soil, manure and irrigation water) and nearby water sources using multilocus-based phylogenetic analysis. Resistant and nonresistant E. coli O157:H7 were isolated, identified and characterised using standard microbiological methods. The results showed that soil samples had a high prevalence of E. coli O157:H7 (31.73%) and ESBL-producing E. coli O157:H7 (22.11%). Multilocus sequencing typing (MLST) analysis revealed that all ESBL-producing E. coli O157:H7 were identified as ST11. Phylogenetic analysis of E. coli O157:H7 indicated that irrigation water might be a reservoir for E. coli O157:H7. For antibiotic-resistant genes (ARG), the most common was bla_TEM in 85% (n = 34), followed by bla_OXA in 70% (n = 28), bla_NDM and sul1 30% (n = 12) and lastly mcr-1, which was only found in one soil isolate. The results showed that ESBL-producing E. coli O157:H7 isolates were intermixed in three clades, indicating close relatedness between isolated strains from different matrices.

Molecular and Phenotypic Characteristics of Escherichia coli Isolates from Farmed Minks in Zhucheng, China

In this study, the prevalence, phenotypes, and clonal relationships of Escherichia coli (E. coli) strains isolated from minks were investigated. In July 2017, a total of 62 fresh faecal swab samples were randomly collected from one large-scale mink farm in Zhucheng, Shandong Province, China. In all the samples, 50 E. coli strains were isolated and then assigned to serotyping, antimicrobial susceptibility test, detection of antimicrobial resistance genes and the Class 1 integrons, and multilocus sequence typing (MLST). Four pathogenic serotypes were identified among all the isolates, while the most common serotype was enterohemorrhagic E. coli O104:H4 (6.0 %). Antimicrobial sensitivity testing revealed that most isolates were susceptible to cefoxitin (96.0 %) and amikacin (82.0 %), while most isolates were resistant to ampicillin (92.0 %) and tetracycline (90.0 %). An analysis of the nucleotide sequences revealed that 7 isolates (14.0%) carried 4 types of Class 1 integron cassette, including dfrA27+aadA2+qnrA (57.1%), dfrA17+aadA5 (14.3%), dfrA12+aadA2 (14.3%), and dfrA1+aadA1 (14.3%). PCR screening showed that 14 antibiotic resistance genes were presented in 50 isolates, while the most prevalent resistance gene was qnrS, which was detected in 60.0 % of isolates, followed by sul2 (40.0%) and oqxA (38.0%). MLST analysis showed that 32 sequence types (STs) were identified, while ST46 was the predominant genotype among all isolates. Clonal complex 3 (CC3) was dominant. Compared with 340 human E. coli STs reported in China, the ST10 clonal complex, known as the largest human clonal complex, was also found in the 50 mink E. coli isolates. Meanwhile, mink-derived strain ST206 formed a new clonal complex, CC206, which was different from human ST strains. Our results showed that farmed minks could be reservoirs of antimicrobial-resistant E. coli with Class 1 integron cassettes and resistance genes, which were likely to pose a threat to public health. Therefore, continuous inspections and monitoring of E. coli in minks are essential for detecting and controlling emerging E. coli with different serovars as well as antibiotic resistance.

Molecular characterization of enterohemorrhagic E. coli O157 isolated from animal fecal and food samples in Eastern China

Objective. To elucidate the extent of food contamination by enterohemorrhagic Escherichia coli (EHEC) O157 in Eastern China. Methods. A total of 1100 food and animal fecal samples were screened for EHEC O157. Then, molecular characterization of each isolate was determined. Results. EHEC O157 was isolated as follows: pig feces, 4% (20/500); cattle feces, 3.3% (2/60); chicken feces, 1.43% (2/140); pork, 2.14% (3/140), milk, 1.67% (1/60); and chicken meat, 1.67% (1/60). The stx1, stx2, eae, and hlyA genes were present in 26.7% (8/30), 40% (12/30), 63.3% (19/30), and 50% (15/30) of the O157 isolates, respectively. Molecular typing showed that strains from fecal and food samples were clustered into the same molecular typing group. Furthermore, the isolates from pork and pig feces possessed the same characterization as the clinical strains ATCC35150 and ATCC43889. Biofilm formation assays showed that 53.3% of the EHEC O157 isolates could produce biofilm. However, composite analyses showed that biofilm formation of EHEC O157 was independent of genetic background. Conclusions. Animal feces, especially from pigs, serve as reservoirs for food contamination by EHEC O157. Thus, it is important to control contamination by EHEC O157 on farms and in abattoirs to reduce the incidence of foodborne infections in humans.