Clonal diversity of vancomycin-resistant enterococci from an outbreak in a tertiary care university hospital

Hospital outbreak of vancomycin-resistant enterococci caused by a single clone of Enterococcus raffinosus and several clones of Enterococcus faecium

A mixed outbreak caused by vancomycin-resistant Enterococcus raffinosus and Enterococcus faecium carrying the vanA gene was analysed. The outbreak occurred in a large hospital in Poland and affected 27 patients, most of whom were colonised, in three wards, including the haematology unit. The E. raffinosus isolates had a high-level multiresistant phenotype and were initially misidentified as Enterococcus avium; their unambiguous identification was provided by multilocus sequence analysis. The molecular investigation demonstrated the clonal character of the E. raffinosus outbreak and the polyclonal structure of the E. faecium isolates. All of the isolates carried the same Tn1546-like element containing an IS1251-like insertion sequence, located on a c. 50-kb conjugative plasmid. One of the E. faecium clones, found previously to be endemic in the hospital, was probably the source of the plasmid. The results of the study suggest that difficulties in identification may have led to an underestimate of the importance of E. raffinosus in vancomycin-resistant enterococci (VRE) control strategies.

Recurrent episodes of shock-like syndrome caused by the same strain of vancomycin-resistant Enterococcus faecium in a pediatric patient

We present the case of a hospitalized pediatric patient with short bowel syndrome who was dependent upon total parenteral nutrition for 17 months. Shortly after admission she became colonized with vancomycin-resistant Enterococcus faecium (VRE) and developed 12 distinct episodes of serious infection associated with it. The course of VRE colonization and infections in this patient was studied through analysis of 40 representative isolates obtained from different sites during distinct episodes of infection. Standard microbiological techniques, automated ribosomal DNA typing, polymerase chain reaction, and pulsed-field gel electrophoresis (PFGE) were used. All isolates except for the one associated with the initial episode of bacteremia were VRE, and were multidrug resistant. The last four episodes of infection were caused by isolates resistant to all tested antibiotics except for intermediate susceptibility to chloramphenicol. The vanA genotype was a source of vancomycin resistance in all VRE isolates. Both ribotyping and PFGE showed two distinct clones of VRE in clinical and stool surveillance isolates: one was associated with clinical illness and the other was not associated with infection. Recurrent VRE infections occur as a consequence of prolonged gastrointestinal colonization. Morbidity is associated with host factors, the presence of co-pathogens, and possibly intrinsically more virulent VRE strain.

An in vitro study of the probiotic potential of a bile-salt-hydrolyzing Lactobacillus fermentum strain, and determination of its cholesterol-lowering properties

This study evaluated the use of a bile-salt-hydrolyzing Lactobacillus fermentum strain as a probiotic with potential hypocholesterolemic properties. The effect of L. fermentum on representative microbial populations and overall metabolic activity of the human intestinal microbiota was investigated using a three-stage continuous culture system. Also, the use of galactooligosaccharides as a prebiotic to enhance growth and/or activity of the Lactobacillus strain was evaluated. Administration of L. fermentum resulted in a decrease in the overall bifidobacterial population (ca. 1 log unit). In the in vitro system, no significant changes were observed in the total bacterial, Lactobacillus, Bacteroides, and clostridial populations through L. fermentum supplementation. Acetate production decreased by 9 to 27%, while the propionate and butyrate concentrations increased considerably (50 to 90% and 52 to 157%, respectively). A general, although lesser, increase in the production of lactate was observed with the administration of the L. fermentum strain. Supplementation of the prebiotic to the culture medium did not cause statistically significant changes in either the numbers or the activity of the microbiota, although an increase in the butyrate production was seen (29 to 39%). Results from this in vitro study suggest that L. fermentum KC5b is a candidate probiotic which may affect cholesterol metabolism. The short-chain fatty acid concentrations, specifically the molar proportion of propionate and/or bile salt deconjugation, are probably the major mechanism involved in the purported cholesterol-lowering properties of this strain.

Automated ribotyping of vancomycin-resistant Enterococcus faecium isolates

Vancomycin-resistant Enterococcus faecium (VREF) strains represent an important threat in hospital infections in the United States and are found at high frequencies in both the community and farm animals in Europe. We evaluated automated ribotyping for interlaboratory reproducibility by using the restriction enzymes EcoRI and BamHI and compared ribotyping to both amplification of fragment length polymorphism (AFLP) analysis and multilocus sequence typing (MLST) to assess its discriminatory power and capacity for the identification of epidemiologically important strains. Of 19 (EcoRI) and 16 (BamHI) isolates tested in duplicate in two laboratories, 18 (95%) and 16 (100%), respectively, showed reproducible ribotypes. These high reproducibility rates were obtained only after manual refinement of the automated fingerprint analysis. A group of 49 VREF strains initially selected to represent 32 distinct AFLP types were separated into 28 EcoRI ribotypes, 25 BamHI ribotypes, and 28 sequence types. Ribotyping with EcoRI and BamHI was able to discern the host-specific genogroups recently disclosed by AFLP typing and MLST and to distinguish most strains containing the esp gene, a marker specific for strains causing hospital outbreaks. An expandable ribotype identification library was created. We recommend EcoRI as the enzyme of choice for automated ribotyping of VREF strains. Given the high level of discrimination of VREF strains, the high rate of interlaboratory reproducibility, and the potential for the identification of epidemiologically important genotypes, automated ribotyping appears to be a very valuable approach for characterizing VREF strains.

Stool colonization with vancomycin-resistant enterococci in healthcare workers and their households

OBJECTIVE

To determine the prevalence of stool colonization with vancomycin-resistant enterococci (VRE) among healthcare workers (HCWs) and their families.

DESIGN

Prospective assessment of fecal colonization with VRE.

SETTING

A 603-bed, tertiary-care teaching hospital.

PARTICIPANTS

Healthy volunteers recruited from hospital employees and their households were screened to exclude pregnancy, diabetes mellitus, immunosuppressive disorders, and recent use of antimicrobials.

INTERVENTION

Self-obtained stool swabs were used to obtain cultures. Isolated enterococci were screened for vancomycin resistance and species were identified. Intra-household isolates were genotyped using pulsed-field gel electrophoresis (PFGE).

RESULTS

The participants (n = 228; age range, 28 days to 80 years) were from 137 households with and 91 without employees who had contact with patients. Enterococcus species were isolated from 127 stool specimens (55.7%). VRE were detected in 12 individuals, representing 6 E. casseliflavus, 5 E. faecium, and 1 E. gallinarum. VRE were more commonly isolated in employees who had contact with patients (5 of 52 vs 0 of 40; relative risk [RR], 1.9; 95% confidence interval [CI95], 1.5 to 2.2; P = .07) and their household members (10 of 137 vs 2 of 91; RR, 3.3; CI95, 0.7 to 14.8; P = .13). In 2 households (2 adults in a physician's household and an adult plus a child in a nurse's household) PFGE analysis demonstrated identical intra-household strains of vancomycin-resistant E. faecium.

CONCLUSIONS

VRE colonization was found in 5.3% of screened stools and was more prevalent in HCWs who had contact with patients and their households. Identical PFGE patterns between 2 employees who had contact with patients and their household members demonstrated probable intra-household spread. Although the mode of acquisition was uncertain, the association with employees who had contact with patients suggests possible occupational sources. These findings demonstrate the spread of VRE within the household and implicate occupational risk for its acquisition.

Is it time for brushless scrubbing with an alcohol-based agent?

The practice of surgical scrubbing in perioperative settings is changing rapidly. This article presents information about eliminating the traditional scrub brush technique and using an alcohol formulation for surgical hand scrubs. Also covered are antimicrobial agents, relevant US Food and Drug Administration classifications, skin and fingernail care, and implementation of changes. The article challenges surgical team members to evaluate a new and different approach to surgical hand scrubbing.

Vancomycin-resistant Enterococcus spp. isolated from wastewater and chicken feces in the United States

Vancomycin-resistant Enterococcus spp. (VRE) were isolated from sewage and chicken feces but not from other animal fecal sources (dog, cow, and pig) or from surface waters tested. VRE from hospital wastewater were resistant to > or =20 microg of vancomycin/ml and possessed the vanA gene. VRE from residential wastewater and chicken feces were resistant to 3 to 5 microg of vancomycin/ml and possessed the vanC gene.

Risk factors for colonization with vancomycin-resistant enterococci in a Melbourne hospital

OBJECTIVE

To determine risk factors for colonization with vancomycin-resistant enterococci (VRE) in a hospital outbreak.

DESIGN

Outbreak investigation and case-control study.

SETTING

A referral teaching hospital in Melbourne, Australia.

PARTICIPANTS

Cases were inpatients colonized (with or without clinical disease) with VRE between July 26 and November 28, 1998; controls were hospitalized patients without VRE.

METHODS

Five cases of VRE were identified between July 26 and November 8, 1998, by growth of VRE from various sites. Active case finding by cultures of rectal swabs from patients surveyed in wards was commenced on July 26, after the first isolate of VRE.

RESULTS

There were 19 cases and 66 controls. All the VRE identified were vanB, and all were Enterococcus faecium. One molecular type predominated (18/19 cases). In a logistic-regression model, being on the same ward as a VRE case was the highest risk factor (odds ratio [OR], 82; 95% confidence interval [CI95], 5.7-1,176; P=.001). Having more than five antibiotics (OR, 11.9; CI95 1.1-129.6; P<.05), use of metronidazole (OR, 10.9; CI95, 1.7-69.8; P=.01), and being a medical patient (OR, 8.1; CI95, 1.4-47.6; P<.05) also were significant. Intensive care unit admission was associated with decreased risk (OR, 0.1; CI95, 0.01-0.8; P<.05).

CONCLUSION

Our findings are consistent with an acute hospital outbreak. Monitoring and control of antibiotic use, particularly metronidazole, may reduce VRE in our hospital. Ongoing surveillance and staff education also are necessary.