ABSTRACT
We compared recovery of Staphylococcus aureus and methicillin-resistant S. aureus (MRSA) from nasal and groin swab specimens of 600 HIV-infected outpatients by selective and nonselective direct plating and broth enrichment. Swabs were collected at baseline, 6-month, and 12-month visits and cultured by direct plating to mannitol salt agar (MSA) and CHROMagar MRSA (CM) and overnight broth enrichment with subculture to MSA (broth). MRSA isolates were characterized by pulsed-field gel electrophoresis (PFGE), staphylococcal cassette chromosome mec (SCCmec) typing, and PCR for the Panton-Valentine leukocidin. At each visit, 13 to 15% of patients were colonized with MRSA and 30 to 33% were colonized with methicillin-susceptible S. aureus (MSSA). Broth, CM, and MSA detected 95%, 82%, and 76% of MRSA-positive specimens, respectively. MRSA recovery was significantly higher from broth than CM (P ≤ 0.001) or MSA (P ≤ 0.001); there was no significant difference in recovery between MSA and CM. MSSA recovery also increased significantly when using broth than when using MSA (P ≤ 0.001). Among specimens collected from the groin, broth, CM, and MSA detected 88%, 54%, and 49% of the MRSA-positive isolates, respectively. Broth enrichment had a greater impact on recovery of MRSA from the groin than from the nose compared to both CM (P ≤ 0.001) and MSA (P ≤ 0.001). Overall, 19% of MRSA-colonized patients would have been missed with nasal swab specimen culture only. USA500/Iberian and USA300 were the most common MRSA strains recovered, and USA300 was more likely than other strain types to be recovered from the groin than from the nose (P = 0.05).
Subject(s)
Bacteriological Techniques/methods , HIV Infections/complications , Methicillin-Resistant Staphylococcus aureus/isolation & purification , Staphylococcal Infections/diagnosis , Staphylococcal Infections/microbiology , Bacterial Toxins/genetics , DNA, Bacterial/genetics , Electrophoresis, Gel, Pulsed-Field , Exotoxins/genetics , Genotype , Groin/microbiology , Humans , Leukocidins/genetics , Methicillin-Resistant Staphylococcus aureus/classification , Methicillin-Resistant Staphylococcus aureus/genetics , Molecular Typing , Nose/microbiology , Outpatients , Polymerase Chain Reaction , Sensitivity and SpecificityABSTRACT
We describe a real-time PCR assay for the detection of methicillin-resistant Staphylococcus aureus and genes encoding toxic shock syndrome toxin 1 and Panton-Valentine leukocidin. Rapid screening and detection of toxins is a useful tool for surveillance studies and outbreak investigations involving large numbers of isolates.
Subject(s)
Bacterial Toxins/analysis , Bacteriological Techniques/methods , Enterotoxins/analysis , Exotoxins/analysis , Leukocidins/analysis , Methicillin-Resistant Staphylococcus aureus/isolation & purification , Multiplex Polymerase Chain Reaction/methods , Real-Time Polymerase Chain Reaction/methods , Staphylococcal Infections/microbiology , Superantigens/analysis , Bacterial Toxins/genetics , DNA, Bacterial/genetics , Enterotoxins/genetics , Exotoxins/genetics , Genes, Bacterial , Humans , Leukocidins/genetics , Mass Screening/methods , Methicillin-Resistant Staphylococcus aureus/genetics , Superantigens/geneticsABSTRACT
AdvanDx VRE EVIGENE, a commercial vanA/vanB DNA hybridization assay to identify vancomycin-resistant enterococci (VRE), was evaluated for the detection of vanA in Staphylococcus aureus. Performance was assessed using S. aureus, VRE, and vancomycin-intermediate and -susceptible isolates. The assay demonstrated 100% sensitivity and specificity when analyzed visually and by optical density.
