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Presence of Panton-Valentine Leukocidin in MSSA Not Only Factor in Assessing Disease Severity: Presented at ICC
By Louise Gagnon
TORONTO -- June 23, 2009 -- Factors other than the presence of Panton-Valentine leukocidin (PVL) in methicillin-susceptible Staphylococcus aureus (MSSA) need to be explored to assess disease severity, according to a retrospective chart review presented here at the 26th International Congress of Chemotherapy and Infection (ICC).
Although the toxin has been well studied in methicillin-resistant S aureus (MRSA), it has not been as well examined in MSSA, explained principal investigator Toylin Musewe, McMaster University, Hamilton, Ontario, on June 20..
"There is an ongoing debate about the role of PVL," said Musewe. "It appears that PVL is likely not the best indicator of how severe MMSA can be. It's not a black-and-white issue. There appear to be other things that come into play."
Musewe and colleagues retrospectively studied 181 isolates from wound infections and 82 isolates from blood infections, all coming from patients aged >=18 years who had no history of MRSA colonisation.
The prevalence of PVL genes in MSSA isolates was fairly low at 2.7%, with 7 isolates being positive for PVL.
"The rate is not a cause for huge concern," said Musewe.
All positive isolates originated from wound infections. Of the 7 patients, 5 had abscesses, 1 had osteomyelitis, and 1 had a percutaneous endoscopic gastrostomy tube-site infection.
No patients had systemic signs or symptoms of infection, but 1 patient died secondary to a pulmonary embolism.
Interestingly, in this analysis, a proportion of MSSA strains were community associated rather than hospital associated.
Investigators also found that PVL-positive organisms were susceptible to cefazolin, ciprofloxacin, clindamycin, erythromycin, rifampin, tetracycline, and trimethoprim-sulfamethoxazole by VITEK-2 testing. Three of the isolates were resistant to fluoroquinolones (43%), and 1 was resistant to both clindamycin and erythromycin (14%).
"This study is retrospective," explained Musewe. "A prospective study would allow us to track many more variables. We would also like to follow patients for a longer period."
[Presentation title: A Retrospective Study of the Prevalence of Panton-Valentine Leukocidin (PVL) Genes in Methicillin-Susceptible Staphylococcus Aureus and the Impact of PVL on Clinical Disease Severity. Abstract P303]
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