Superbug MRSA shows seasonality

BALTIMORE, Feb. 28 (UPI) —

Strains of antibiotic-resistant Staphylococcus aureus bacteria show seasonal preferences, putting U.S. children at greater risk in summer, researchers say.

Lead author Eili Klein of The Johns Hopkins Center for Advanced Modeling in the Social, Behavioral and Health Sciences; said the study also found seniors were at greater risk in winter.

"It’s unclear why these seasonal and age preferences for infection with methicillin-resistant Staph aureus occurred," Klein said in a statement.

However, increased use of antibiotics in the winter might be one of the reasons. The winter strain that infected seniors at a greater rate was generally acquired in the hospital and resistant to more antibiotics, Klein said. On the other hand, the summer strain of MRSA, seen frequency in children, was largely a community-transmitted strain resistant to fewer antibiotics, the study said.

"Overprescribing antibiotics is not harmless," Klein added. "Inappropriate use of these drugs to treat influenza and other respiratory infections is driving resistance throughout the community, increasing the probability that children will contract untreatable infections."

The study, published online in the American Journal of Epidemiology, found hospitalizations from infections tied to MRSA doubled in the United States from 1999 to 2005. However, ballooning infection numbers were propelled by MRSA acquired in community settings, not hospital or other healthcare settings, as had been the case prior to 1999, Klein said.