A prolonged outbreak of Pseudomonas aeruginosa in a neonatal intensive care unit: did staff fingernails play a role in disease transmission?

Infect Control Hosp Epidemiol. 2000 Feb;21(2):80-5. doi: 10.1086/501739.


Objectives: To describe an outbreak of Pseudomonas aeruginosa bloodstream infection (BSI) and endotracheal tube (ETT) colonization in a neonatal intensive care unit (NICU), determine risk factors for infection, and make preventive recommendations.

Design: A 15-month cohort study followed by a case-control study with an environmental survey and molecular typing of available isolates using pulsed-field gel electrophoresis.

Setting and patients: Neonates in the NICU of a university-affiliated children's hospital.

Interventions: Improved hand washing and restriction of use of long or artificial fingernails.

Results: Of 439 neonates admitted during the study period, 46 (10.5%) acquired P aeruginosa; 16 (35%) of those died. Fifteen (75%) of 20 patients for whom isolates were genotyped had genotype A, and 3 (15%) had genotype B. Of 104 healthcare workers (HCWs) from whom hand cultures were obtained, P aeruginosa was isolated from three nurses. Cultures from nurses A-1 and A-2 grew genotype A, and cultures from nurse B grew genotype B. Nurse A-1 had long natural fingernails, nurse B had long artificial fingernails, and nurse A-2 had short natural fingernails. On multivariate logistic regression analysis, exposure to nurse A-1 and exposure to nurse B were each independently associated with acquiring a BSI or ETT colonization with P aeruginosa, but other variables, including exposure to nurse A-2, were not.

Conclusion: Epidemiological evidence demonstrated an association between acquiring P aeruginosa and exposure to two nurses. Genetic and environmental evidence supported that association and suggested, but did not prove, a possible role for long or artificial fingernails in the colonization of HCWs' hands with P aeruginosa. Requiring short natural fingernails in NICUs is a reasonable policy that might reduce the incidence of hospital-acquired infections.

MeSH terms

  • Cross Infection / epidemiology
  • Cross Infection / microbiology
  • Cross Infection / transmission*
  • DNA, Bacterial / analysis
  • DNA, Bacterial / genetics
  • Disease Outbreaks / statistics & numerical data*
  • Equipment Contamination / statistics & numerical data
  • Female
  • Genotype
  • Humans
  • Infant, Newborn
  • Infection Control
  • Infectious Disease Transmission, Professional-to-Patient / statistics & numerical data*
  • Intensive Care Units, Neonatal / statistics & numerical data*
  • Intubation, Intratracheal / adverse effects
  • Intubation, Intratracheal / instrumentation
  • Logistic Models
  • Male
  • Nails / microbiology*
  • Nursing Staff, Hospital / statistics & numerical data*
  • Oklahoma / epidemiology
  • Pseudomonas Infections / epidemiology
  • Pseudomonas Infections / microbiology
  • Pseudomonas Infections / transmission*
  • Pseudomonas aeruginosa / classification
  • Pseudomonas aeruginosa / genetics
  • Retrospective Studies
  • Risk Factors
  • Serotyping
  • Workforce


  • DNA, Bacterial