The occurrence of virulence traits among high-level aminoglycosides resistant Enterococcus isolates obtained from feces of humans, animals, and birds in South Korea.

Enterococcus isolates (1500) obtained from the feces of 48 humans, 209 domesticated food animals, and 155 wild geese in South Korea were characterized with respect to species status by PCR analyses and resistance to antibiotics. Of the 1500 strains examined, the majority (n=577) were Enterococcus faecalis from 224 (54.4%) of the samples feces, while 299 were of E. faecium from 125 of the samples (30.3%), 224 were E. hirae from 101 (24.5%) of the samples, 94 were E. casseliflavus from 43 (10.4%) of the samples, and one was E. gallinarum. While 305 isolated from 125 (30.3%) of the samples were unidentified species. Approximately 15, 60, 50, 55, 3, and 40% of samples obtained from beef cattle, chickens, ducks, swine, wild geese, and humans, respectively, yielded Enterococcus isolates that were resistant to high-levels of aminoglycosides (i.e., of gentamicin, kanamycin, and streptomycin, minimum inhibitory concentrations were >1000 mg/l). The 180 Enterococcus isolates that showed high levels of resistance to aminoglycoside antibiotics (HLAR) were screened for virulence genes encoding for aggregation substance (agg), cytolysin activator (cylA), gelatinase (gelE) and surface protein (esp). Of those, the gelE gene was found most frequently in chickens and ducks of the HLAR isolates, while 56 E. faecalis and 13 E. faecium HLAR were gelatinase positive and showed hemolysin activity. Multiple antibiotic resistant Enterococcus isolates carrying virulence genes were most frequently isolated from poultry and swine, and were mostly E. faecalis or E. faecium. These findings suggest that restriction of the use of antibiotics in food animal operations in South Korea, especially those involved in poultry and swine production would be desirable.

High diversity and abundance of antibiotic-resistant Escherichia coli isolated from humans and farm animal hosts in Jeonnam Province, South Korea.

The spread of antibiotics resistance among bacteria is a threat to human health. Since South Korea uses approximately 1.5 times more antibiotics than do other OECD countries, this is likely to impact the numbers and types of antibiotic-resistant bacteria found in the environment. In this study we examined feces from domesticated animals and humans for the diversity and abundance of antibiotic-resistant Escherichia coli. Abundant antibiotic-resistant E. coli were isolated from all the tested animals and humans and were examined by horizontal, fluorophore-enhanced, rep-PCR (HFERP) DNA fingerprint analysis. A total of 793 unique, non-clonal, E. coli isolates were obtained from the 513 human and animal hosts examined. Antibiotic resistance analysis, done using 14 antibiotics, indicated that 72.3% of the isolates (573 of 793) were found resistant to more than one antibiotic. The E. coli isolated from swine were resistant to the greatest number of antibiotics. Tetracycline resistant E. coli were routinely isolated from all animal hosts (36 to 77% per host), except for dairy cattle (9.3%). Twenty nine E. coli isolates from all hosts, except for duck, were resistant to more than 10 antibiotics. Gene transfer and southern hybridization studies revealed that resistance to 13 of the antibiotics was self-transmissible, and likely mediated by plasmids and integrons. Since genetically diverse and numerically abundant antibiotic-resistant E. coli were consistently recovered from chicken, swine and other domesticated animals in South Korea, our results suggest that the use of sub-therapeutic levels of antibiotics for disease prophylaxis and growth promotion should be curtailed.

Absence of Escherichia coli phylogenetic group B2 strains in humans and domesticated animals from Jeonnam Province, Republic of Korea.

Multiplex PCR analyses of DNAs from genotypically unique Escherichia coli strains isolated from the feces of 138 humans and 376 domesticated animals from Jeonnam Province, South Korea, performed using primers specific for the chuA and yjaA genes and an unknown DNA fragment, TSPE4.C2, indicated that none of the strains belonged to E. coli phylogenetic group B2. In contrast, phylogenetic group B2 strains were detected in about 17% (8 of 48) of isolates from feces of 24 wild geese and in 3% (3 of 96) of isolates obtained from the Yeongsan River in Jeonnam Province, South Korea. The distribution of E. coli strains in phylogenetic groups A, B1, and D varied depending on the host examined, and there was no apparent seasonal variation in the distribution of strains in phylogenetic groups among the Yeongsan River isolates. The distribution of four virulence genes (eaeA, hlyA, stx(1), and stx(2)) in isolates was also examined by using multiplex PCR. Virulence genes were detected in about 5% (38 of 707) of the total group of unique strains examined, with 24, 13, 13, and 9 strains containing hlyA, eaeA, stx(2), and stx(1), respectively. The virulence genes were most frequently present in phylogenetic group B1 strains isolated from beef cattle. Taken together, results of these studies indicate that E. coli strains in phylogenetic group B2 were rarely found in humans and domesticated animals in Jeonnam Province, South Korea, and that the majority of strains containing virulence genes belonged to phylogenetic group B1 and were isolated from beef cattle. Results of this study also suggest that the relationship between the presence and types of virulence genes and phylogenetic groupings may differ among geographically distinct E. coli populations.