SHEA Conference: NICU outbreaks linked two MRSA staff carriers

SHEA Conference

NICU outbreaks linked two MRSA staff carriers

One cleared, other leaves patient care duties

Two separate outbreaks among frail infants in neonatal intensive care units (NICUs) were linked to workers who were chronic carriers of methicillin-resistant Staphylococcus aureus.

MRSA is well recognized as a nosocomial pathogen in NICUs, but the unit at Sunnybrook and Women’s College in Toronto previously had not reported MRSA transmission, said Anne K. Augustin, MLT, CIC, an infection control professional at the facility. The chain of events began when an eye swab taken May 23, 2004, from a 29-day-old infant was positive for MRSA.

"At that time, we had no other MRSA-positive infants in our NICU," she told SHEA attendees. "The index case was a twin, and the case and the twin were both placed on MRSA precautions."

All of the infants in the index case’s room were immediately cultured, but no new cases were found. "Not having identified any cases, we expanded our screening to include all of the infants in the NICU," she said. "Through this, we identified two cases."

All health care workers on the unit were cultured by nasal swab and had their hands inspected for skin breakdown. Any hands that had skin breakdown were cultured. Weekly prevalence screening for all cultures of infants continued, and four more infants with MRSA were discovered. A total of eight infants were identified as infected or colonized with the outbreak strain between the end of May and the end of August 2004.

"All of our health care workers of all disciplines rotate their assignments through all three of the NICU rooms," Augustin said. "This outbreak was extremely unusual for us. Although we have had a couple of introductions of MRSA identified in our unit, we had never, ever had any transmission of MRSA within our NICU."

The source had to be identified if further transmission of MRSA was to be prevented. Staffing assignments for MRSA-positive infants were reviewed. All MRSA-positive infants were put on MRSA precautions; infants and staff were cohorted by MRSA status of the infants.

The five colonized and three infected infants, were located in all three areas of the NICU. All parent cultures were negative, but two health care worker nasal swabs were positive. One worker was decolonized successfully, but "HCW 2" was to prove more of a problem. That worker was epidemiologically linked to six of the eight MRSA-positive infants. Moreover, transmission of MRSA ceased when HCW 2 was on vacation but there were new cases when the worker returned.

"HCW 2 was furloughed and decolonized and repeat nasal cultures were negative," Augustin said. "When [the worker] returned to work after a summer vacation, we had a new infant case."

HCW 2 was reassessed and found to have infected skin lesions on the back. MRSA was isolated only from broth-enhanced culture of these lesions. HCW 2 was furloughed from work and retreated. The worker was referred to a dermatologist and has remained MRSA-negative for six months.

"When health care workers are epidemiologically linked to transmission of MRSA, thorough assessment, including inspection of the entire skin surface, is necessary," Augustin warned. "One should consider use of enhanced culture techniques as we did with the broth enrichment to increase the culture sensitivity, particularly in high-risk settings like NICUs."

The ear has it

Another health care worker with chronic ear infections was found to be the source of an MRSA outbreak in an NICU in the Cleveland Clinic Foundations, reported Mary Bertin, RN, BSN, CIC, an ICP at the facility.

Three neonates in a 17-bassinet NICU were identified with MRSA bloodstream infections on a single day in April 2004 prompting an investigation. The strain was phenotypically unique: negative by slide and Staphaurex test but positive for the tube coagulase test and resistant to gentamicin and tetracycline. A point prevalence survey identified six additional colonized neonates.

Bertin and colleagues cohorted infected/colonized neonates, implemented contact precautions, and applied mupirocin to neonate nares and umbilicus. Workers were retrained on cleaning/disinfection procedures and renewed emphasis was placed on hand hygiene.

Surveillance cultures of nares and umbilicus were instituted three times a week for noncolonized neonates and new admissions.

But despite the interventions, two new colonized neonates were identified one month later. It was found that a health care worker was undergoing antibiotic therapy for chronic otitis infection. MRSA was isolated from the worker’s ear canal and nares. This worker clearly was linked to the outbreak, having direct contact with eight of the 11 infected/colonized neonates. The worker had a history of chronic otitis infections and had began employment in the NICU in June 2003. A retrospective review of microbiologic isolates from the NICU revealed the strain initially was cultured from a neonate two months after the worker began working in the NICU. After removing the worker from patient care duties, the epidemic strain was eradicated from the NICU.

Routine surveillance for MRSA among neonates may have provided a mechanism of earlier recognition of the outbreak and now is standard practice, she added. "We had achieved control with enhanced infection control practices, but we were not able to eradicate [this] until we actually removed [the] health care worker. This worker is still working in our institution, but not in a high-risk setting."

ICPs pull out all stops for mystery outbreak

In another NICU outbreak reported at SHEA, a combination of rigorous infection control measures, active surveillance, and environmental cleaning vanquished an MRSA cluster.

"Our next step would have been screening health care workers and [culturing] the environment," said Wendy Gornick, MS, CIC, infection control professional at Children’s Hospital of Orange County, CA. "But our babies did well and were discharged, and we had no other cases."

The outbreak began last year with detection of a single case on the NICU. "This was unusual for our unit," she said. "This neonate was about 5 weeks old, and we were very concerned about transmission having occurred. We initiated point prevalence cultures just a couple of days later."

One additional patient case of MRSA colonization was discovered after all 26 babies on the unit were cultured. But two weeks later, another case appeared and a point prevalence survey was again conducted. Of 27 patients screened, four (27%) were MRSA-positive. Gornick and colleagues mobilized a rigorous and multifaceted response to stamp out the MRSA in the unit. Prevention and control measures included cohorting infected and colonized infants. Staff and parents entering the cohort had to follow contact precautions requiring gowns, gloves and masks.

"Anything brought out of the cohort was cleaned with a quaternary disinfectant. Nursing and respiratory staff were also cohorted, and compliance was monitored. Parent education was very important. Their baby was in an area where everybody was gowning and gloving. It was somewhat alarming to some of the them," Gornick said. One strategy to allay parental anxiety was having an infectious disease physician hold an evening question-and-answer session with family members.

Meanwhile, a heavy emphasis was being put on environmental cleaning, including adoption of a "terminal cleaning" checklist for discharged infant areas. (See form.) "We requested additional environmental support during the time period," she said. "That [request] was not always able to be accommodated, but when they could, they cleaned twice a day in this unit. Also with the environmental services department, we developed a terminal-cleaning checklist. There are many details in cleaning a room."

In using the form, the housekeeper initials areas in the center column when they have been completed. A unit manager must then sign and date the completed form, documenting that the room was cleaned appropriately.

As a final measure to keep MRSA at bay in the unit, active surveillance cultures were initiated and continued over the next six months. All NICU patients were screened on admission for MRSA. Of 287 cultures, only one was positive for MRSA, she said. "Based on our findings, we modified our admission screening to focus on transfers hospitalized elsewhere for more than two weeks and babies born to MRSA-positive mothers. We’re back down to baseline. We were very fortunate without this cluster."

In all, seven neonates had been infected or colonized during the original outbreak of unknown origin. Molecular epidemiology indicated five of the isolates were identical and another was closely related. "All patients did well and were discharged home," Gornick said.