Molecular characteristics of Escherichia coli from bulk tank milk in Korea

Abstract

Background Escherichia coli , which causes subclinical or clinical mastitis in cattle, is responsible for transmitting antimicrobial resistance via human consumption of raw milk or raw milk products. Objectives The objective of this study was to investigate the molecular characteristics of 183 E. coli from bulk tank milk of five different dairy factories in Korea. Methods The molecular characteristics of E. coli such as serogroup, virulence, antimicrobial resistance, and integron genes were detected using polymerase chain reaction and antimicrobial susceptibility were tested using the disk diffusion test. Results In the distribution of phylogenetic groups, group D was the most prevalent (59.6%) and followed by group B1 (25.1%). The most predominant serogroup was O173 (15.3%), and a total of 46 different serotypes were detected. The virulence gene found most often was fimH (73.2%), and stx1 , fimH , incC , fyuA , and iutA genes were significantly higher in isolates of phylogenetic group B1 compared to phylogenetic groups A, B2, and D ( p < 0.05). Among 64 E. coli isolates that showed resistance to at least one antimicrobial, the highest resistance rate was observed for tetracyclines (37.5%). All 18 integron-positive E. coli carried the integron class I ( int1 ) gene, and three different gene cassette arrangements, dfrA12 + aadA2 (2 isolates), aac(6′)-Ib3+aac(6′)-Ib-cr+aadA4 (2 isolates), and dfrA17+aadA5 (1 isolate) were detected. Conclusions These data suggest that the E. coli from bulk tank milk can be an indicator for dissemination of antimicrobial resistance and virulence factors via cross-contamination.

Dairy Products: A Potential Source of Multidrug-Resistant Enterococcus faecalis and Enterococcus faecium Strains

“…This accords with what was reported by Hosseini et al, who analyzed enterococci isolated from meat and dairy products [ 2 ]. Similar findings were also presented by other authors [ 26 , 29 , 35 ]. For both E. faecium and E. faecalis , as many as 95% of strains were observed to be chloramphenicol-susceptible, an identical outcome to that in the study by Palmieri et al [ 29 ].…”

“…The most common Enterococcus spp. are E. faecium, E. faecalis, and E. durans which, excluding E. durans , were claimed in different studies to be the predominant species in most of the milk and dairy products intended for direct consumption [ 4 , 26 ]. Enterococci are a global health problem and are considered opportunistic pathogens and, in fact, these bacteria have been reported to be associated with some human and animal infections [ 27 ].…”

“…These genes may undergo horizontal transfer, which is one of the main mechanisms of their spread among enterococcal species. For this reason, the presence of enterococci in milk may be the cause of strains’ acquisition of MDR [ 26 ]. The use of antibiotics in food animals is noted to be associated with rates of antibiotic resistance in humans [ 11 ].…”

“…Previous investigations have reported varied prevalences of resistant enterococci to erythromycin, which were as follows: 14.3% [ 36 ], 46.2% [ 26 ], 52.5% [ 32 ], 53% [ 29 ], and 71.4% [ 4 ]. In this study, echoing the results of Chajęcka-Wierzchowska et al [ 36 ], the percentage of erythromycin-resistant enterococci was 14.8%, while in the research of other authors this percentage was higher and ranged from 46.2 to 71.4% [ 4 , 26 , 29 , 32 ]. Różańska et al noted 82.16% of enterococci isolated from mastitis samples to be lincomycin-resistant [ 37 ].…”

Genetic characterization of third- or fourth-generation cephalosporin-resistant avian pathogenic Escherichia coli isolated from broilers

“…The Statistical Package for Social Science version 25 (IBM SPSS Statistics for Windows, Armonk, NY, USA) was used for statistical analysis, which included the independent samples t-test, Fisher's exact test, and Pearson's chi-square test with Bonferroni correction as described previously (10,29). Differences were considered significant at p < 0.05.…”