Genome-Based Characterization of Multidrug-Resistant Escherichia coli Isolated from Clinical Bovine Mastitis.

Mastitis occurrence in dairy cows is a broad topic that involves several sectors, from antimicrobial resistance and virulence of strains to economic implications and cattle management practices. Here, we assessed the molecular characterization (antimicrobial resistance determinants, virulence genes, sequences type, serotypes, and plasmid types) of 178 Escherichia coli strains isolated from milk samples from cows with clinical mastitis using a genome-based k-mers approach. Of these, 53 (29.8%) showed multidrug resistance by disc diffusion. We selected eight multidrug-resistant mastitis-associated E. coli for whole-genome sequencing and molecular characterization based on raw data using k-mers. We assessed antimicrobial resistance genes, virulence factors, serotypes, Multilocus Sequence Typing (MLST), and plasmid types. The most antimicrobial resistance gene found were blaTEM-1B (7/8), tetA (6/8), strA (6/8), strB (6/8), and qnrB19 (5/8). A total of 25 virulence factors were detected encoding adhesins, capsule, enzymes/proteins, increased serum survival, hemolysin, colicins, and iron uptake. These virulence factors were associated with Extraintestinal Pathogenic E. coli. Three pandemic clones were found: ST10, ST101, and ST69. Two E. coli were assigned in the O117 serogroup and one in the O8:H25 serotype. The most common plasmid groups were IncFII (7/8) and IncFIB (6/8). Our findings contribute to the knowledge of virulence mechanisms, epidemiological aspects, and antimicrobial resistance determinants of E. coli strains obtained from clinical mammary infections of cows.

Antimicrobial resistance in diarrheagenic Escherichia coli from ready-to-eat foods.

Certain subgroups of Escherichia coli have congenital or acquired virulence properties that allow them to cause a wide spectrum of disease. The aim of this study was to investigate the occurrence of diarrheagenic E. coli strains in ready-to-eat (RTE) foods produced in institutional, commercial and hotel restaurants in Salvador, Brazil. The presence of virulent isolates and antimicrobial resistance were evaluated. Four hundred forty-six samples were collected and grouped into cereals and vegetables, meat-based preparations, cooked salads, raw salads, garnishes, soups and sauces, desserts and juices. E. coli were detected using the most probable number method, the presence of virulence factors in isolates was determined by polymerase chain reaction (PCR) assays, and antibiotic resistance was analyzed using the disc diffusion method. In total, 15 isolates (3.1%) of E. coli were recovered; raw salads had the highest detection rate, 1.4%, followed by cooked salads, 0.8%; meat-based preparations, 0.4%; and cereals and vegetables, 0.4%. PCR assays showed that none of the isolates had the virulence genes cnf1, cnf2, eae, sta, lt1, stx1, stx2 or cdtB. The isolates showed resistance to nine antibiotics of the 15 tested, and the highest levels of resistance were found for sulfamethoxazole/trimethoprim, tetracycline, ampicillin, and chloramphenicol (13.3% of isolates for each antibiotic). One isolate from cooked salad had plasmid-mediated multidrug resistance to tetracycline, trimethoprim/sulfamethoxazole, ampicillin and chloramphenicol. These results suggest that RTE foods, especially raw salads, can be reservoirs of E. coli and facilitate the spread of antibiotic resistance genes to the gastrointestinal microbiota of humans.