Neonatal intensive care unit outbreak caused by a strain of Klebsiella oxytoca resistant to aztreonam due to overproduction of chromosomal β-lactamase

Seokhoon Jeong, W. M. Kim, C. L. Chang, J. M. Kim, Kyungwon Lee, Y. Chong, H. Y. Hwang, Y. W. Baek, H. K. Chung, I. G. Woo, J. Y. Ku

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Klebsiella oxytoca strains resistant to both aztreonam and ceftriaxone were isolated from six neonates in a neonatal intensive care unit and water reservoirs of two humidifiers attached to the neonatal incubators. These isolates were assumed to be of the same clone because they were characterized by the same antimicrobial susceptibility and pulsed field gel electrophoresis patterns. It was established that the drug resistance was attributed to overproduction of chromosomally encoded K1 β-lactamase. It was determined that an isolate (K. oxytoca H1) contained a high enzyme concentration (27 μg/100 μg of protein in enzyme extracts), at least 27 times higher than the control K. oxytoca N1. It was also demonstrated that isolates had a point mutation in the - 35 concensus region of the promotor gene of blaOXY-2 leading to enzyme overproduction. Outbreaks caused by K1 hyperproducers have not previously been described.

Original languageEnglish
Pages (from-to)281-288
Number of pages8
JournalJournal of Hospital Infection
Issue number4
Publication statusPublished - 2001 Jan 1


All Science Journal Classification (ASJC) codes

  • Microbiology (medical)
  • Infectious Diseases

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