Enterococcus species are considered as parts of the indicator strains for fecal contamination on retail meats because they reside in the gastrointestinal tracts of humans and animals. Frequent acquisition and dissemination of antibiotic resistance genes among enterococci have increased their morbidity and mortality rates and thus become a serious public health issue. For example, vancomycin (Van)-resistant and/or multidrug resistant (MDR) enterococci are increased during recent years. Currently, only a few therapeutic options have been approved for linezolid (LZD), daptomycin (DAP), and tigecycline (TGC) to treat VAN-resistant and/or MDR enterococcal infections. In this review, we have updated the recent status of enterococcal resistance to those three last-resort antimicrobials (LZD, DAP, TGC) among livestock animals and retail meats.

One hundred one enterococcal isolates from feces of livestock animals in Korea were screened for the presence of bacteriocins. Sixteen of 41 (39%) E. faecalis and 4 of 56 (7.1%) E. faecium isolates showed antimicrobial activity against at least one indicator strain. Only 4 of 20 the enterococcal isolates showing antimicrobial activity possessed at least one bacteriocin gene. While entA and entB were detected in three isolates as a pair of genotype, entQ, bac31, and AS-48 were not found in the enterococcal isolates. In almost all isolates, a correlation between genotype and phenotype of these determinants was not always observed.

From April 2008 to January 2009, a total 458 raw milk samples were randomly collected from 15 stock raising farms located in northern area of Kyunggi province and cultured for the presence of Enterococci spp. A total 170 enterococcal isolates were recovered from the raw milk samples. Enterococcus faecalis was predominant species recovered (64.7%), followed by E. faecium (18.8%), E. avium (5.9%), E. gallinarum (5.9%) and E. durans (4.7%). Antimicrobial resistance patterns of 170 Enterococci spp. against ampicillin, erythromycin, tetracyclin, chloramphenicol, vancomycin, ciprofloxacin and streptomycin were tested. According to the result, they showed high level resistance to erythromycin and streptomycin (82,9% and 93,5% respectively), moderately resistance to ampicillin, chloramphenicol and tetracyclin (50%, 45.9% and 32%, respectively) but fortunately, vancomycin and ciprofloxacin are still effective against this species.

Demand for the development of non-antibiotic growth promoters (AGP) in animal production surged in recent years. However, elucidating the specific mechanisms and action of prebiotics, probiotics, and synbiotics as non-AGP in animals is still in progress. This work investigated and compared faecal microbiotas of weaned piglets under the administration of a basal diet (CON) and with prebiotic lactulose (LAC), probiotic Enterococcus faecium NCIMB 11181 (PRO), or their synbiotic combination (SYN). Although prebiotics and/or probiotics in the diet significantly increased alpha-diversity compared with CON values, no differences were detected in richness and diversity values among the treatment groups (LAC, PRO, and SYN). At phylum level, the Firmicutes to Bacteroidetes ratio increased in the treatment groups in comparison to the CON group, and the lowest abundance of Proteobacteria was found in LAC group. At family level, Enterobacteriaceae decreased in all treatments, especially more than 10-fold reduction in LAC group compared with CON group. At genus level, the highest abundance of Oscillibacter was detected in PRO group, the highest Clostridium in LAC group, and the highest Lactobacillus in SYN group; the abundance of Escherichia was lowest in LAC group. Clustering in the DAPC plots illustrated distinct separation of the feeding groups (CON, LAC, PRO, and SYN) from one another, showing that microbial communities had different compositions according to different feed additives. Effects of LAC and PRO treatments on the faecal microbiota suggest independent mechanisms; nonetheless, the impact of SYN might also be distinct from that when each are administered singly as LAC or PRO.