Staph Pneumonia Appears More Common

(March 20, 2008) - Staph infections may be getting more and more common. Preliminary research from the Centers for Disease Control and Prevention (CDC) suggests that community acquired pneumonia (Read about "Pneumonia") caused by the Staphylococcus aureus bacterium may be more common than originally suspected, including that caused by antibiotic resistant strains. (Read about "Staph & MRSA")

"Over the last few years we have been receiving reports of a severe community acquired pneumonia (CAP) caused by S. aureus. There are a lot of questions about this disease, but until now there have primarily been case studies which tend to highlight the severest of cases and may present a biased picture," says Alexander Kallen, a lead researcher on the study.

"No one really knows what the true incidence of S. aureus CAP is. People suspect that S. aureus causes 3 percent-5 percent of all CAP cases, but the number of cases per month we found suggest that these rates of S. aureus CAP might be higher than previously estimated," says Kallen.

In addition, the data also suggest that the case-fatality rate may be lower than the rate reported in recent case series which have been between 30 percent and 50 percent. Kallen's study reports a case-fatality rate of about 13 percent, which is much lower than previous estimates.

"One thing that concerns us is methicillin-resistant S. aureus (MRSA) increasing in the community," says Kallen.

As with mortality, they found while the proportion of S. aureus CAP cases caused by MRSA was lower than the case series, it was still significant. Approximately half of the S. aureus CAP cases were caused by MRSA, compared to 70 percent-80 percent suggested by recent case series.

"Our study found about half the patients had MRSA, which is not unexpected but quite concerning," says Kallen.

Even more concerning to Kallen was the fact that close to 40 percent of the children with MRSA CAP were not given antibiotics that covered the resistant strain.

"The fact that a lot of these kids who had MRSA were not treated with antibiotics that have activitity against MRSA suggests that clinicians are not recognizing this organism as a cause of CAP during influenza season," says Kallen. (Read about "Flu Season")