title: Neonatal intensive care unit outbreak caused by a strain of Klebsiella oxytoca resistant to aztreonam due to overproduction of chromosomal beta-lactamase.
abstract: 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 Kl beta-lactamase. It was determined that an isolate (K. oxytoca H1) contained a high enzyme concentration (27microg/100microg 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 bla(OXY-2)leading to enzyme overproduction. Outbreaks caused by K1 hyperproducers have not previously been described.
authors.affiliation: Department of Clinical Pathology, Kosin University College of Medicine, Pusan, Korea. kscpjsh@ns.kosinmed.or.kr
authors.forename: S H
authors.initials: SH
authors.lastname: Jeong
authors.forename: W M
authors.initials: WM
authors.lastname: Kim
authors.forename: C L
authors.initials: CL
authors.lastname: Chang
authors.forename: J M
authors.initials: JM
authors.lastname: Kim
authors.forename: K
authors.initials: K
authors.lastname: Lee
authors.forename: Y
authors.initials: Y
authors.lastname: Chong
authors.forename: H Y
authors.initials: HY
authors.lastname: Hwang
authors.forename: Y W
authors.initials: YW
authors.lastname: Baek
authors.forename: H K
authors.initials: HK
authors.lastname: Chung
authors.forename: I G
authors.initials: IG
authors.lastname: Woo
authors.forename: J Y
authors.initials: JY
authors.lastname: Ku
mesh_terms: D001398:Aztreonam / Q000494:pharmacology*; D001426:Bacterial Proteins; D002443:Ceftriaxone / Q000494:pharmacology; D003428:Cross Infection / Q000453:epidemiology*; D016521:Electrophoresis, Gel, Pulsed-Field; D006801:Humans; D007231:Infant, Newborn; D007363:Intensive Care Units, Neonatal; D007709:Klebsiella / Q000187:drug effects* / Q000201:enzymology / Q000235:genetics*; D007710:Klebsiella Infections / Q000453:epidemiology*; D008826:Microbial Sensitivity Tests; D017354:Point Mutation; D016133:Polymerase Chain Reaction; D018440:beta-Lactam Resistance / Q000235:genetics; D001618:beta-Lactamases / Q000235:genetics / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D002443:Ceftriaxone; C121000:TEM24 beta-lactamase; D001618:beta-Lactamases; D001398:Aztreonam