Contaminated soap fuels NICU serratia outbreak
Contaminated hands through washing
Hand washing -- a cardinal principle of infection control -- may have actually fanned the flames of a deadly Serratia marcescens outbreak due to contaminated soap solutions used by health care workers, an investigator reported recently in Atlanta at the annual conference of the Association for Professionals in Infection Control and Epidemiology, based in Mundelein, IL.
From August 1994 through October 1995, S. marcesens can colonization or infection occurred in 32 infants in a neonatal intensive care unit at Baystate Medical Center in Springfield, MA, reported Lenox Archibald, MBBS, an epidemiologist in the hospital infections program at the Centers for Disease Control and Prevention in Atlanta.
A gram-negative rod that flourishes in moist environments, S. marcesens can cause severe nosocomial infections, he reminded, noting that hand-transmission by health care workers has been implicated in past outbreaks.
In the outbreak reported at APIC, CDC investigators linked the cases to a change in hand washing and soap delivery systems in the NICU, where wall-mounted soap dispensers were replaced by four ounce bottle solutions carried by individual workers.
The culprit -- Individual bottles
From January to July 1995, NICU HCWs carried their own bottles of soap, which were often left standing inverted near NICU sink areas. Sixteen (31%) of 52 samples of soap and bottles of soap carried by health care workers grew S. marcesens. In addition, one of the NICU's 15 sinks yielded the pathogen on cultures. DNA banding patterns of case infants, soap bottles, and sink isolates were identical. Unopened bottles of the soap, a phenolic solution, yielded no growth.
"The organism was probably introduced into the NICU by an infant or health care worker in 1994, with subsequent direct or indirect transmission through the environment," Archibald told APIC attendees. "Prevailing infection control measures were just sufficient to prevent a large-scale outbreak."
However, the presence of the pathogen was then amplified by the switch to personal soap bottles, which were often left standing upside down in sink areas to ease use as the liquid level lowered inside. This practice -- much as people do with shampoo bottles -- probably allowed serratia from sinks to gain entry and colonize the bottles, he speculated. Flip lids may not have been completely closed, allowing the bottles to become contaminated, he said.
'All it takes is a simple pool of water'
"It didn't matter how good a nurse or doctor you were in a busy unit," he said. "All it takes is a simple pool of water [and] one bug. The bug goes up into the bottle, and it becomes contaminated. Because of that and because two babies died, I personally don't like four-ounce bottles."
Indeed, no cases have occurred since the practice was abandoned, he reported.
Measures recommended by the CDC included enhanced environmental cleaning and a switch back to wall-mounted soap dispensers.
"If feasible, all soap dispensers in the NICU should be operated via foot pumps," he advised.
Cases were spread out throughout the unit, and more sink areas were likely colonized than just the one that cultured positive, he added.
"Please bear in mind that cultures were taken at the time when environmental cleaning and cohorting of case infants had been ongoing for almost a month," he said. *
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