Disease Information for Staphylococcus aureus/CA-MRSA virulent PVL gene: Definition

. Recently, a growing number of cases of MRSA infection acquired in the community (CA-MRSA infection) have been reported. Naimi and colleagues (2003) conducted a study based on an MRSA sentinel surveillance network in Minnesota, characterizing the demographic and clinical features of CA-MRSA and nosocomial MRSA infection and comparing the microbiological and molecular features of the two types of infection; Minnesota has 12 laboratory facilities that are surveillance sites for MRSA; 6 of these sites are in the 7-county Minneapolis-St. Paul metropolitan area. In 2000, all patients with MRSA isolates were identified, and infection-control practitioners reviewed their medical records.

In 2000, 4612 unique patients with S. aureus infections were identified, about one-quarter of whom had MRSA isolated; Of those patients, 85% had HA-MRSA infection, 12% had CA-MRSA infection, and 3% had unclassified infection; Patients with CA-MRSA infection were more likely to be nonwhite, were younger, and had a lower median household income than patients with HA-MRSA infection. Most cases of CA-MRSA infection involved skin and soft tissue; CA-MRSA infections were less likely to be respiratory or urinary tract infections than were HA-MRSA infections; Almost one-quarter of patients with CA-MRSA were hospitalized, and 5% required intensive care. More than 60% of CA-MRSA cases were first treated with a -lactam drug that was ineffective; CA-MRSA was more likely than HA-MRSA to be susceptible to other antimicrobial agents, particularly to all 4 of the following drugs: ciprofloxacin, clindamycin, gentamicin, and trimethoprim-sulfamethoxazole.

Of 16 exotoxin genes present in the MRSA isolates, 6 were significantly more likely to occur in CA-MRSA, including SCCmec IV (a gene that is probably more mobile than other SCCmec alleles), and 7 were significantly more likely to be found among HA-MRSA isolates; Panton Valentine leukocidin genes [PVL Genes] were found in 20 CA-MRSA isolates tested (77%) but in only 1 HA-MRSA isolate.

This report identifies important characteristics of CA-MRSA infections and compares those characteristics with those of HA-MRSA infections; Patients with CA-MRSA are more likely to be nonwhite, to be young, and to have skin and soft tissue infections; These bacterial strains are genetically distinct from HA-MRSA strains and probably arose independently; CA-MRSA strains are more likely to be susceptible to many agents, a characteristic suggesting that their emergence may be due to insertion of a mecA gene into a methicillin-susceptible strain of S aureus; Merck Medicus/harrison on line 7/05

suggested rx: trimethaprim-sulfasoxazole, cleocin, zyvox or vancomycin

very often after influenza or flu like illness then necrotizing pneumonia with low wbc but high bands with left shift. [pvl gene toxin lyses polys]

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