In-vitro activities of 11 antibiotics against vancomycin-resistant enterococci isolated in Japan

Antimicrobial resistance profile of Enterococcus species isolated from intestinal tracts of hospitalized patients in Jimma, Ethiopia

Background

Multi-drug-resistant Enterococci colonizing the intestinal tract of hospitalized patients are the major source of infection as well as nosocomial spread. Despite worldwide increasing rate of multidrug resistant Enterococci colonization and infection among hospitalized patients, there is scarcity of data from resource limited setting. The present study aimed at determining the antimicrobial resistance profile of Enterococcus species from intestinal tracts of hospitalized patients in Jimma, Ethiopia.

Methods

The study was conducted among hospitalized patients at Jimma University Specialized Hospital, from January to July 2013. Fecal samples were collected and processed for bacterial isolation and susceptibility testing to antimicrobial agents. Stool samples were inoculated onto enterococcus selective media (Bile Esculin azide agar plate) with and without 6 µg/ml of vancomycin. The isolates were identified to genus and species level by cultural characteristics, Gram’s stain, catalase test, growth in 6.5% NaCl broth, growth at 45°C, motility test and by using API 20 Streptococcus system. Sensitivity testing was done using Kirby–Bauer disk diffusion method. Minimum inhibitory concentrations for vancomycin were determined using E-test strips.

Result

Overall, Enterococci were isolated from 114 (76%) of the study subjects. The isolates were Enterococcus faecium (35.1%) followed by Enterococcusfaecalis (29.8%), Enterococcus gallinarum (17.5%), Enterococcuscasseliflavus (8.8%) and Enterococcusdurans (8.8%). Among 114 tested Enterococci isolates, 41 (36%) were resistant to ampicillin, 62 (54.4%) to streptomycin and 39 (34.2%) to gentamycin. Other alternative antibiotics to treat mixed nosocomial infection caused by Enterococci also showed high rate of resistance in vitro: ciprofloxacin (50% of resistance), norfloxacin (49.1%), erythromycin (63.2%), tetracycline (64.9%), chloramphenicol (34.2%), and nitrofrantoin (32.4%). Multiple drug resistance was observed among 89.5% of E. faecium and E. faecalis. Vancomycin resistant Enterococci were observed in 5% of E. faecium isolates.

Conclusion

This study reveals high rate of fecal colonization by multidrug-resistant Enterococci and prevalence of vancomycin resistance strains. Thus periodic surveillance of antibacterial susceptibilities is recommended to detect emerging resistance and to prevent the spread of antibacterial-resistant strains.

Emergence of vancomycin-resistant enterococci in a tertiary hospital in Crete, Greece: a cluster of cases and prevalence study on intestinal colonisation

The aim of this study was to investigate the clinical and epidemiological characteristics of five consecutive cases of infection with vancomycin-resistant enterococci (VRE) and the prevalence of faecal carriage of VRE among patients admitted to a 700-bed university hospital where no VRE had been isolated previously. In a 2-month period, five consecutive patients infected with VRE were detected. Three VanB+ Enterococcus faecium isolates were obtained from three patients, while two VanA+ E. faecium isolates, one VanA+ Enterococcus faecalis isolate and one VanC1+ Enterococcus gallinarum isolate were obtained from the other two patients. Of 218 faecal specimens from all hospital wards, 41 (18.8%) were found to contain VRE. Forty-two isolates of VRE were obtained, comprising one (2%) E. faecalis, 11 (27%) E. faecium, 24 (57%) E. gallinarum and six (14%) Enterococcus casseliflavus/flavescens. Four isolates carried the vanA gene, eight carried vanB, 24 carried vanC1, and six carried vanC2/C3. Use of glycopeptides, the presence of central venous catheters and renal dialysis all correlated with VRE colonisation. The prevalence rates were among the highest reported in the literature.

Drug resistance in fecal enterococci in Hong Kong

Our purpose was to estimate the rate of carriage of vancomycin-resistant enterococci (VRE) in hospitalized patients in a district hospital and in healthy subjects in the community in Hong Kong. Rectal swabs were collected from all patients admitted to the intensive care unit, and stool specimens were collected from all patients presenting with suspected antibiotic-associated diarrhea over a 2-month period. Stool specimens were also collected from healthy subjects in the community. Specimens were enriched and cultured on selective media for the isolation of enterococci. All isolates were identified, and their minimum inhibitory concentration for vancomycin was determined. Susceptibility to other antibiotics was investigated. Samples yielded 125 isolates of enterococci, the majority of isolates being Enterococcus faecalis (75) and E. faecium (35). Nine of 11 strains of E. gallinarum and 2 of 2 strains of E. casseliflavus isolated from hospitalized patients were intermediately resistant to vancomycin, but no strains highly resistant to vancomycin were isolated. Resistance to other drugs, including the fluoroquinolones, was present, and a high-level resistance to gentamicin and streptomycin was found in 37% and 46% of strains, respectively. Colonization with VRE remains low in Hong Kong. This result is supported by the low level of isolation of VRE from infections in the region and may be attributable to low levels of vancomycin use. High-level aminoglycoside resistance and fluoroquinolone resistance are common, and continued monitoring for VRE is suggested.

Efficacy of linezolid in treatment of experimental endocarditis caused by methicillin-resistant Staphylococcus aureus

The efficacies of orally (p.o.) dosed linezolid and intravenously (i.v.) dosed vancomycin against methicillin-resistant Staphylococcus aureus (MRSA) in rabbits with experimental aortic-valve endocarditis were investigated. After endocarditis was established with a recent clinical MRSA isolate, rabbits were dosed for 5 days with linezolid (p.o., three times a day) at either 25, 50, or 75 mg/kg of body weight or vancomycin (i.v., twice a day) at 25 mg/kg. The 25-mg/kg linezolid group had a high mortality rate and bacterial counts in the valve vegetations that were not different from those of the controls. Linezolid dosed p.o. at 50 and 75 mg/kg and i.v. vancomycin produced statistically significant reductions in bacterial counts compared to those of the untreated controls. The reduced bacterial counts and culture-negative valve rates for the animals treated with linezolid at 75 mg/kg were similar to those for the vancomycin-treated animals. Concentrations of linezolid in plasma were determined at several points in the dosing regimen. These results suggest that the efficacy of linezolid in this infection model is related to trough levels in plasma that remain above the MIC for this microorganism. At the ineffective dose of linezolid (25 mg/kg) the concentration at sacrifice was 0.045 times the MIC, whereas the concentrations of linezolid in plasma in the 50- and 75-mg/kg groups were 2 and 5 times the MIC at sacrifice, respectively. The results from this experimental model suggest that the oxazolidinone linezolid may be effective for the treatment of serious staphylococcal infections when resistance to other antimicrobials is present.

The epidemiology of vancomycin-resistant enterococci

Major differences in the epidemiology of vanA carrying enterococci exist between Europe and the USA, where these organisms have been well investigated. These differences are probably related to the differences in antibiotic use in humans and animals in both continents, but more research is needed before firm conclusions can be drawn.