Epidemiology of methicillin-susceptible Staphylococcus aureus in the neonatal intensive care unit.
OBJECTIVE
When the incidence of methicillin-susceptible Staphylococcus aureus (MSSA) infection or colonization increased in our neonatal intensive care unit (NICU), we sought to further our understanding of the relationship among colonization with MSSA, endemic infection, and clonal spread.


METHODS
A retrospective cohort study was used to determine risk factors for acquisition of a predominant clone of MSSA (clone "B").


METHODS
A 45-bed, university-affiliated, level III-IV NICU.


METHODS
Infants hospitalized in the NICU from October 1999 to September 2000.


METHODS
Infection control strategies included surveillance cultures of infants, cohorting infected or colonized infants, contact precautions, universal glove use, mupirocin treatment of the anterior nares of all infants in the NICU, and a hexachlorophene bath for infants weighing 1,500 g or more.


RESULTS
During the 1-year study period, three periods of increased incidence of MSSA colonization or infection, ranging from 6.4 to 13.5 cases per 1,000 patient-days per month, were observed. Molecular typing using pulsed-field gel electrophoresis demonstrated two predominant clones, clone "B" and clone "G," corresponding to two periods of increased incidence. Multivariate analysis demonstrated that length of stay (OR, 1.035; 95% confidence interval [CI95], 1.008 to 1.062; P = .010) increased risk per day) and the use of H2-blockers (OR, 20.44; CI95, 2.48 to 168.26; P = .005) were risk factors for either colonization or infection with clone "B," and that the use of peripheral catheters was protective (OR, 0.06; CI95, 0.01 to 0.43; P= .005).


CONCLUSIONS
Control of MSSA represents unique challenges as colonization is expected, endemic infections are tolerated, and surveillance efforts generally focus on multidrug-resistant pathogens. Future studies should address cost-effective surveillance strategies for endemic infections.
Graham
Philip L
PL
Department of Pediatrics, Columbia University, New York, NY 10032, USA.
Morel
Anne-Sophie
AS
Zhou
Juyan
J
Wu
Fann
F
Della-Latta
Phyllis
P
Rubenstein
David
D
Saiman
Lisa
L
D015331:Cohort Studies; D003428:Cross Infection / Q000453:epidemiology* / Q000382:microbiology; D015180:Electrophoresis, Gel, Two-Dimensional; D006801:Humans; D015994:Incidence; D007231:Infant, Newborn; D007363:Intensive Care Units, Neonatal; D016106:Methicillin Resistance / Q000235:genetics; D017720:Molecular Epidemiology; D009519:New York City / Q000453:epidemiology; D012189:Retrospective Studies; D012307:Risk Factors; D018571:Sentinel Surveillance; D013203:Staphylococcal Infections / Q000453:epidemiology* / Q000382:microbiology; D013211:Staphylococcus aureus / Q000235:genetics / Q000302:isolation & purification*