Trends in incidence of late-onset methicillin-resistant Staphylococcus aureus infection in neonatal intensive care units: data from the National Nosocomial Infections Surveillance System, 1995-2004.
BACKGROUND
Methicillin-resistant Staphylococcus aureus (MRSA) is increasingly being reported to cause outbreaks in neonatal intensive care units (NICUs). We assessed the scope and magnitude of MRSA infections with disease onset after 3 days of age (late-onset MRSA infections) in NICUs.


METHODS
We analyzed data reported by NICUs participating in the National Nosocomial Infections Surveillance system from 1995 through 2004. For each surveillance month, all healthcare-associated infections as defined by National Nosocomial Infections Surveillance criteria were reported, along with antimicrobial susceptibility patterns of the isolates. We pooled the data from all NICUs by birth weight category and calendar year. Poisson regression was used to assess changes in incidence of late-onset MRSA infections per 10,000 patient-days.


RESULTS
Overall, 149 NICUs reported 4831 S. aureus infections and 5,878,139 patient-days. Methicillin testing data were available for 4302 S. aureus isolates, of which 975 (23%) were MRSA. Incidence of late-onset MRSA infection per 10,000 patient-days, combining all birthweight categories, increased 308% from 0.7 in 1995 to 3.1 in 2004 (P < 0.001). A significant increase in incidence of MRSA infections was observed among all 4 birthweight categories analyzed separately (<or=1000 g, 1001-1500 g, 1501-2500 g, and >2500 g). The distribution of MRSA infection by type of infection did not vary during the study period; 299 (31%) of MRSA infections were bloodstream infections, 174 (18%) were pneumonia, and 161 (17%) were conjunctivitis.


CONCLUSIONS
The incidence of late-onset MRSA infections increased substantially between 1995 and 2004, indicating a need to reinforce infection control recommendations and to explore potential sources and routes of transmission.
Lessa
Fernanda C
FC
Division of Healthcare Quality Promotion, National Center for Preparedness, Detection, and Control of Infectious Diseases, Centers for Disease Control and Prevention, Atlanta, GA, USA. flessa@cdc.gov
Edwards
Jonathan R
JR
Fridkin
Scott K
SK
Tenover
Fred C
FC
Horan
Teresa C
TC
Gorwitz
Rachel J
RJ
D016470:Bacteremia / Q000453:epidemiology / Q000382:microbiology; D003231:Conjunctivitis / Q000453:epidemiology / Q000382:microbiology; D003428:Cross Infection / Q000453:epidemiology* / Q000382:microbiology*; D005260:Female; D006801:Humans; D015994:Incidence; D007223:Infant; D007231:Infant, Newborn; D007363:Intensive Care Units, Neonatal; D055624:Methicillin-Resistant Staphylococcus aureus / Q000302:isolation & purification*; D011023:Pneumonia, Staphylococcal / Q000453:epidemiology / Q000382:microbiology; D013203:Staphylococcal Infections / Q000453:epidemiology* / Q000382:microbiology*; D014481:United States / Q000453:epidemiology