Occurrence of virulent multidrug-resistantEnterococcus faecalisandEnterococcus faeciumin the pigs, farmers and farm environments in Malaysia

Abstract

BackgroundEnterococcus faecalis and Enterococcus faecium are ubiquitous opportunistic pathogens found in the guts of humans and farmed animals. This study aimed to determine the occurrence, antimicrobial resistance, virulence, biofilm-forming ability and genotypes of E. faecalis and E. faecium from swine farms. Correlations between the genotypes, virulotypes, antibiotic resistance, and the environmental factors such as locality of farms and farm hygiene practice were explored.MethodsE. faecalis and E. faecium strains were isolated from the oral, rectal and fecal samples of 140 pigs; nasal, urine and fecal samples of 34 farmers working in the farms and 42 environmental samples collected from seven swine farms located in Peninsular Malaysia. Antibiotic susceptibility test was performed using the disk diffusion method, and the antibiotic resistance and virulence genes were detected by Polymerase Chain Reaction. Repetitive Extragenic Palindromic-Polymerase Chain Reaction and Pulsed-Field Gel Electrophoresis were performed to determine the clonality of the strains. Crosstab/Chi-square test and DistLM statistical analyses methods were used to determine the correlations between the genotypes, virulence factors, antibiotic resistance, and the environmental factors.ResultsA total of 211 E. faecalis and 42 E. faecium were recovered from 140 pigs, 34 farmers and 42 environmental samples collected from seven swine farms in Peninsular Malaysia. Ninety-eight percent of the strains were multidrug-resistant (resistant to chloramphenicol, tetracycline, ciprofloxacin and erythromycin). Fifty-two percent of the strains formed biofilms. Virulence genes efa, asaI, gelE, esp, cyl and ace genes were detected. Virulence genes efa and asaI were most prevalent in E. faecalis (90%) and E. faecium (43%), respectively. Cluster analyses based on REP-PCR and PFGE showed the strains were genetically diverse. Overall, the strains isolated from pigs and farmers were distinct, except for three highly similar strains found in pigs and farmers. The strains were regional- and host-specific.DiscussionThis study revealed alarming high frequencies of multidrug-resistant enterococci in pigs and swine farmers. The presence of resistance and virulence genes and the ability to form biofilm further enhance the persistence and pathogenicity of the strains. Although the overall clonality of the strains were regionals and host-specific, strains with high similarity were found in different hosts. This study reiterates a need of a more stringent regulation to ensure the proper use of antibiotics in swine husbandry to reduce the wide spread of multidrug-resistant strains.

Assessment of Susceptibility to Five Common Antibiotics and Their Resistance Pattern in Clinical Enterococcus Isolates

“…Accordingly, in the current study, 72% of samples were infected with E. faecalis, 10.75% with E. faecium, and 17.25% with other Enterococcus species. Our results showed that among E. faecalis and E. faecium isolates, resistance to cell wall-active antibiotics (vancomycin, teicoplanin, and fosfomycin trometamol) were 33.5% and 53.5%, respectively, which are consistent with its global prevalence (8,40,46). However, among E. faecalis and E. faecium isolates the highest resistance was to fosfomycin trometamol antibiotic (27% and 32%, respectively) while for the other two antibiotics it was almost the same (5.5% and 10%, respectively).…”

“…The most common human infectious strains of Enterococcus are E. faecalis (85-90%) and E. faecium (10-15%) leading to urinary tract infections, endocarditis, bacteremia, wound infection, abdominal infections, pelvic infections, and meningitis (4). On the other hand, about 30% of all nosocomial bloodstream infections are associated with Enterococcus species and Staphylococcus aureus, resulting in significant morbidity and mortality (5)(6)(7)(8). Based on the United States Nosocomial Infections Surveillance System's data, Enterococci are considered as one of the nosocomial pathogens (9).…”

Comparative genomics of globaloptrA-carryingEnterococcus faecalisuncovers common genetic features and a chromosomal hotspot foroptrAacquisition

“…Figure 1 represents the phylogenetic tree constructed with the entire 28 optrA -carrying E. faecalis genomes using as reference the genome of E. faecalis V583. The healthy humans included correspond to a human volunteer (Efs 599) of the NIH Human Microbiome Project [30] and two swine farmers (Enfs94/P.En218) working in pig farms from Malaysia [23]. In the four E. faecalis genomes from hospitalized patients in China, linezolid resistance was not associated with the consumption of linezolid and an asymptomatic gut colonization was speculated by the authors [25].…”

“…no. MJBW01000000) lacked optrA , but as it was included in the same research project (“ Gastrointestinal health of animal handlers with special emphasis on potential zoonotic transmission of bacterial infection ”) of other related optrA -carrying E. faecalis isolated from pigs, we maintained it for comparison [23].…”

“…Interestingly, the optrA -negative Enfs94 is described as linezolid resistant (MIC not available) according with Tan et al . [23], and so its 23S rRNA (G388A/D130N) and rpl D/L4 protein (T301C/F101L) non-synonymous mutations might contribute to linezolid resistance expression as this strain does not have any other known linezolid resistance mechanism. Curiously, strains from healthy humans presented very different ABR profiles: ST227 strain from a pig farmer (Enfs94) only carried lsa (A) and the ST16 USA human (Efs 599) carried the oxazolidinones resistance genes poxtA and cfr in addition to optrA .…”