MRSA in intensive care nursery showed potential for interinstitutional spread

October 2007

Interinstitutional transfer of neonates with unrecognized methicillin-resistant Staphylococcus aureus may play a role in the introduction of new outbreaks in intensive care nurseries, according to researchers.

Jay R. McDonald, MD, assistant professor of medicine, division of infectious diseases, Washington University School of Medicine in St. Louis, and colleagues conducted a prospective, epidemiologic study of an MRSA outbreak that occurred at Duke University Medical Center in 2005.

“The burden of MRSA in area nurseries and the rate of transfers affect the potential for inter-hospital spread of MRSA and may justify changes in policy regarding surveillance for MRSA and communication between hospitals,” the researchers wrote.

Study results were published in The Pediatric Infectious Disease Journal.

Defining the infection

The study population included any patient admitted to either the intensive care nursery or the transitional-care nursery at Duke University Medical Center during the seven-month outbreak period.

Data from the patients’ charts — including age, sex, race, comorbid conditions and microbiology test results — were collected by an infection control practitioner for epidemiologic investigation. Unit personnel also collected daily census data to determine MRSA prevalence rates among the neonates.

Patients were defined as having nosocomial infection if their colonization or infection was discovered 48 hours or more after admission to the hospital.

The first patient to present with MRSA was a neonate with conjunctivitis whose ocular exudate culture grew MRSA; a second case was confirmed positive five days later in the form of a bloodstream infection. During the seven-month period, 25 cases of MRSA colonization or infection were confirmed.

Fourteen of the 25 cases were in boys, 23 cases were acquired through nosocomial transmission, and two cases were identified through active surveillance cultures at the time of admission.

“During the seven months of the outbreak, two of 94 surveillance cultures obtained upon transfer from another institution were positive. Ten cases (all nosocomial) had clinical illness caused by MRSA,” the researchers wrote.

Six patients had bloodstream infections, two had urinary tract infections, one had both a bloodstream infection and a urinary tract infection, and one had conjunctivitis; 15 patients who were asymptomatically colonized were identified through surveillance cultures.

For patients with nosocomial MRSA, the median length of hospital stay before the first positive culture was found was 15 days.

Controlling the outbreak

The medical center began a series of preventive measures by the second week of the outbreak to prohibit the spread of MRSA.

Surveillance cultures for MRSA were taken on a weekly basis from all of the infants in the intensive care nursery and the transitional-care nursery. Additionally, similar cultures were obtained from infants transferred from other hospitals upon their admission to the medical center, as well as from infants who were to be transferred from that medical center to other hospitals.

Leadership within the nursery and infection control professionals formed a partnership to offer a staff education program dubbed “Back to Basics,” which reinforced proper technique and both hand hygiene and barrier precaution compliance.

“Infection control professionals spent extra time on the unit observing staff practices, performing environmental rounds and monitoring and ensuring compliance with hand hygiene and contact precaution protocols,” the researchers wrote.

Neonates were separated into rooms designated as either MRSA-positive or MRSA-negative, and health care workers were separated as much as possible to care for one group or the other, not both. By the 16th week of the outbreak, the prevalence of MRSA had notably declined, according to the researchers.

Area hospital survey

The researchers designed a survey to determine the prevalence of MRSA in intensive care nurseries at local hospitals and to analyze the policies in place regarding MRSA surveillance at these hospitals. Hospitals were chosen for participation based on whether they had transferred infants to or received infants from Duke University Medical Center during a nine-month period between 2004 and 2005.

Respondents from participating hospitals (n=30) were questioned on whether they were aware of any cases of MRSA infection or colonization that had occurred during the past year in infants in their nursery, and whether they conducted routine MRSA screening of neonates at their institutions.

Twelve hospitals (40%) reported MRSA activity in their neonatal units during the past year, and six (20%) reported that an MRSA outbreak had occurred during the past year.

Nine hospitals reported using active surveillance in their nurseries, according to the researchers. Seven performed active surveillance only at the time of admission for neonates transferred from another hospital, one performed active surveillance during outbreak situations, and one performed active surveillance for all new patient admissions. Eight of the 12 hospitals that reported MRSA activity used some method of active surveillance.

“Our findings suggest that methods for MRSA surveillance and control be developed and implemented in newborn nurseries, especially intensive care nurseries with high rates of interinstitutional patient transfer,” the researchers wrote.

“Nurseries that have endemic or epidemic cases of MRSA colonization or infection should share this information when neonates are transferred to other institutions, and nurseries should seek information about MRSA rates when they accept transfers from other institutions.”

For more information:

• McDonald JR, Carriker CM, Pien BC, et al. Methicillin-resistant Staphylococcus aureus outbreak in an intensive care nursery: Potential for interinstitutional spread. Pediatr Infect Dis J. 2007;26:678-683.