ABSTRACT
Five of the seven cases of vancomycin-resistant Staphylococcus aureus (VRSA) infection identified to date have occurred in southeastern Michigan. VRSA isolates from the four most recent cases (all from Michigan) were characterized. The vanA gene was localized to a single plasmid in each VRSA isolate. The pulsed-field gel electrophoresis patterns of chromosomal DNA and the restriction profile of the plasmid demonstrated that the four isolates were unique and differed from the first three VRSA isolates. Vancomycin-resistant Enterococcus (VRE) isolates, all of which were Enterococcus faecalis, were recovered from case patients 4 to 6. Each VRE isolate transferred vancomycin resistance to E. faecalis JH2-2 by conjugation. PCRs for vanA and the Inc18-like plasmid genes traA and repR confirmed the presence of an Inc18-like vanA plasmid in all VRE isolates and transconjugants. An Inc18-like vanA plasmid was identified in the VRSA isolate from case patient 7. These findings suggest a role of Inc18-like plasmids as vanA donors.
Subject(s)
Bacterial Proteins/genetics , Carbon-Oxygen Ligases/genetics , Plasmids/genetics , Staphylococcus aureus/drug effects , Vancomycin Resistance/genetics , Anti-Bacterial Agents/pharmacology , Conjugation, Genetic , DNA Transposable Elements , DNA, Bacterial/analysis , Electrophoresis, Gel, Pulsed-Field , Enterococcus faecalis/drug effects , Enterococcus faecalis/genetics , Enterococcus faecalis/isolation & purification , Humans , Michigan/epidemiology , Microbial Sensitivity Tests , Polymerase Chain Reaction , Restriction Mapping , Staphylococcal Infections/epidemiology , Staphylococcal Infections/microbiology , Staphylococcus aureus/genetics , Staphylococcus aureus/isolation & purificationABSTRACT
Individuals undergoing hemodialysis may be at increased risk for emerging antimicrobial resistance from vancomycin-intermediate Staphylococcus aureus (VISA) and vancomycin-resistant S. aureus (VRSA). The laboratory detection of VISA and VRSA is challenging and requires the use of well-thought-out algorithms. Newly available antimicrobials such as quinipristin/dalfopristin, linezolid, and daptomycin, as well as older drugs such as trimethoprim-sulfamethoxazole appear to be active against recent strains of VISA and VRSA. Prevention of VISA and VRSA necessitates determining the appropriateness of vancomycin use in renal patients and giving priority to infection control precautions in both inpatient and outpatient settings. Because most VISA and all VRSA to date have arisen from endemic methicillin-resistant S. aureus (MRSA), and in the case of VRSA have acquired genes from vancomycin-resistant enterococci (VRE), the emergence of VISA and VRSA should provide renewed motivation for the containment of MRSA and VRE transmission in the hemodialysis population.
