Outbreak of Extended-Spectrum Beta-Lactamase–Producing Klebsiella Pneumoniae in a Neonatal Intensive Care Unit Linked to Artificial Nails

Background: From April to June 2001, an outbreak of extended-spectrum beta-lactamase (ESBL)–producing Klebsiella pneumoniae infections was investigated in our neonatal intensive care unit. Methods: Cultures of the gastrointestinal tracts of patients, the hands of healthcare workers (HCWs), and the environment were performed to detect potential reservoirs for ESBL-producing K. pneumoniae . Strains of K. pneumoniae were typed by pulsed-field gel electrophoresis using Xbal. A case–control study was performed to determine risk factors for acquisition of the outbreak clone (clone A); cases were infants infected or colonized with clone A and controls (3 per case) were infants with negative surveillance cultures. Results: During the study period, 19 case-infants, of whom 13 were detected by surveillance cultures, harbored clone A. The overall attack rate for the outbreak strain was 45%; 9 of 19 infants presented with invasive disease (n = 6) or developed invasive disease (n = 3) after colonization was detected. Clone A was found on the hands of 2 HCWs, 1 of whom wore artificial nails, and on the designated stethoscope of a case-infant. Multiple logistic regression analysis revealed that length of stay per day (odds ratio [OR], 1.05; 95% confidence interval [CI 95 ], 1.02 to 1.09) and exposure to the HCW wearing artificial fingernails (OR, 7.87; CI 95 , 1.75 to 35.36) were associated with infection or colonization with clone A. Conclusion: Short, well-groomed, natural nails should be mandatory for HCWs with direct patient contact.