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Nailing’ Down a Pseudomonas Outbreak in Cardiac Surgery
Abstract & Commentary
Synopsis: An outbreak of Pseudomonas surgical-site infections was traced to the infected thumbnail of a cardiac surgeon. The outbreak stopped after the infected nail was removed.
Source: Mermel LA, et al. Pseudomonas surgical-site infections linked to a healthcare worker with onychomycosis. Infect Control Hosp Epidemiol. 2003;24:749-752.
During an 8-month period in 2001, 5 surgical-site infections due to P aeruginosa occurred in a university hospital. Three were sternotomy infections, and 2 were infections of a saphenous vein harvest site. Infection control records showed that no P aeruginosa SSIs had occurred on the cardiac surgery service for the preceding 2 years. Mermel and colleagues identified 5 health care workers (HCWs), including 2 cardiac surgeons, who had been involved in at least 2 of the cases. The one surgeon involved in all 5 infected cases had marked onychomycosis of the thumbnail; none of the other HCWs had infected nails. Culture of the surgeon’s nail yielded P aeruginosa. Two isolates from sternotomy infections and one from a leg wound infection were available for molecular subtyping. The 2 sternotomy isolates were identical to the surgeon’s nail isolate by pulse-field gel electrophoresis; the leg wound isolate was distinct.
Specimens from multiple environmental sites were taken, including intra-operative fluids, povidone iodine solution, instruments, potable water, ice machines, hand lotion, autoclaves, and hemotherm units. None of these cultures yielded P aeruginosa.
The surgeon underwent removal of the infected nail; the nailbed culture was also positive for P aeruginosa. When the nail grew back, it was without any sign of onychomycosis, and follow-up culture was negative.
Comment by Robert Muder, MD
Sternal wound infection following cardiac surgery is most commonly due to staphylococci. Pseudomonas sternal infections are uncommon, typically causing approximately 1% of such infections. Thus, the occurrence of multiple Pseudomonas wound infections on the cardiac surgery service in this hospital was an appropriate stimulus to a detailed investigation.
It is highly likely that the ultimate source of the sternal wound infections in this outbreak was the surgeon’s infected thumbnail. This is supported by the observation that he participated in all infected cases and that the Pseudomonas isolate from his nail was genetically indistinguishable from the 2 sternal isolates that were tested. The surgeon’s link to the leg wound infections is unclear, as the available isolate did not match the nail isolate. It should be noted that P aeruginosa is a much more common infecting pathogen of saphenous vein harvest sites than of sternotomy wounds. It’s possible that the leg wound infections were independent of the sternal wound infections, particularly since the surgeon in question had limited involvement in vein harvesting procedures.
This report illustrates that the hands of HCWs can serve not only as the means of transmission of infectious agents between patients, but also as the reservoir as well. Contaminated fingernails have been implicated in a number of nosocomial outbreaks; P aeruginosa and Candida species are the most common organisms implicated.1-3 Artificial nails are more likely to be the culprits than native nails, as the former are much more likely to be colonized with Gram-negative bacilli and fungi than are the latter.4 As a consequence, the most recent CDC hand hygiene guidelines appropriately call for restriction of the wearing of artificial nails in patient care settings.5 It should be noted that the outbreak reported by Mermel et al confirms previous observations that surgical gloves are not adequate to prevent wound contamination in the operative suite when real or artificial nails are heavily colonized with pathogens.
Dr. Muder is Hospital Epidemiologist Pittsburgh VA Medical Center Pittsburgh Section Editor, Hospital Epidemiology
1. Parry MF, et al. Candida osteomyelitis and diskitis after spinal surgery: An outbreak that implicates artificial nail use. Clin Infect Dis. 2001;32:352-357.
2. McNeil SA, et al. Outbreak of sternal surgical site infection due to Pseudomonas aeruginosa traced to a scrub nurse with onychomycosis. Clin Infect Dis. 2001;33:317-323.
3. Foca M, et al. Endemic Pseudomonas aeruginosa infection in a neonatal intensive care unit. N Engl J Med. 2000;343:695-700.
4. Hedderwick SA, et al. Pathogenic organisms associated with artificial fingernails worn by healthcare workers. Infect Control Hosp Epidemiol. 2000;21:505-509.
5. Boyce JM, et al. Guidelines for hand hygiene in health-care settings. Am J Infect Control. 2002;30:S1-S46.