A longitudinal analysis of methicillin-resistant and sensitive Staphylococcus aureus incidence in respect to specimen source, patient location, and temperature variation

Objective: Seasonal variations in temperature exert strong selective pressure on microorganism population dynamics and should be taken into account in epidemiological studies. The objective of the present study was to characterize the seasonal variation of staphylococcal infections in respect to patient location, specimen source, month of year, and temperature variation. Methods: A retrospective longitudinal time-series analysis of methicillin-resistant and methicillin-sensitive Staphylococcus aureus (MRSA and MSSA) was conducted in northeastern Ohio over a 5-year period. Multivariable time-series analyses were performed to detect the variations in the monthly incidence based on location of patients (inpatient, outpatient, and nursing homes), source of specimen (wound, respiratory tract, and urine), time of year (January–December), and temperature variation (average monthly over 5 years). Results: The results indicated a gradual increase in both MRSA and MSSA infections, with outpatient cases representing the majority of cases. If present, the seasonal nature of MRSA infections varied based on specimen source and patient location, with wound infections from outpatients more prevalent in warmer months, and respiratory infections among inpatients more prevalent during colder months. Conclusions: The current report provides a longitudinal analysis of staphylococcal epidemiology, and in the process, identifies the seasonal nature of infections to be multifactorial, depending on such variables as specimen source and patient location. The seasonal nature of staphylococcal infections appears to be the product of a complex interaction among host, pathogen, and environment