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Fingernails longer than the very tip of a pencil are a reservoir for nosocomial pathogens and could pose a risk to vulnerable patients, according to a study presented recently in San Francisco at the annual meeting of the Infectious Diseases Society of America (IDSA).
"In previous research, we found that health care workers wearing artificial fingernails are more likely to carry harmful bacteria and other pathogens under their nails, potentially putting patients at risk for infections," says Shelly A. McNeil, MD, assistant professor of medicine and infectious diseases consultant at Dalhousie University in Halifax, Nova Scotia, Canada. "Now we find that harmful bacteria and yeast also cling to natural nails that extend past the tip of the finger, perhaps because the larger surface area can harbor the germs."
The pathogens most commonly found under the nails were Klebsiella bacteria, which can cause pneumonia and blood stream infections (BSIs), and Candida parapsilosis, a yeast, which can cause BSIs and wound infections.
"We need to study this further to be sure that long nails truly are a problem, but our preliminary research certainly is suggestive," McNeil says. "I wouldn’t be overly concerned if I saw an X-ray tech with long nails, but if I saw an ICU nurse with long nails, I would be."
Tips of natural nails longer than 3 mm (measured underneath the nail, from where it meets the skin) — about the length of the graphite tip of a pencil — were more than five times as likely to harbor harmful germs than those shorter than 3 mm, according to the study conducted by McNeil in Halifax and colleagues at the University of Michigan in Ann Arbor. In the study, all seven workers studies with longer nails harbored pathogens beneath them. However, only two of 11 (18%) health care workers with shorter nails carried pathogens beneath their nails.
Hand washing with antimicrobial soap or alcohol-based gel was equally effective at ridding long and short nails of pathogens. "But they were washing their hands under study conditions, while we watched. In real life, hand washing may not be as effective at ridding nails of the germs." Longer nails may contribute to glove tears, McNeil adds. Patients at risk of infection include those with surgical wounds, catheters, or IV lines that provide direct entry to the bloodstream.
To protect patients, nails should be trimmed to 3 mm or less, she advises. Frequent, thorough hand washing appears to rid long natural nails of the microbes. However, other research by McNeil has shown thorough hand washing is not as effective at ridding artificial nails of the germs.