Neonatal intensive care unit outbreak caused by a strain of Klebsiella oxytoca resistant to aztreonam due to overproduction of chromosomal beta-lactamase
Sh. Jeong et al., Neonatal intensive care unit outbreak caused by a strain of Klebsiella oxytoca resistant to aztreonam due to overproduction of chromosomal beta-lactamase, J HOSP INF, 48(4), 2001, pp. 281-288
Klebsiella oxytoca strains resistant to both aztreonam and ceftriaxone were
isolated from six neonates in a neonatal intensive care unit and water res
ervoirs of two humidifiers attached to the neonatal incubators. These isola
tes 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 ov
erproduction of chromosomally encoded K1 beta -lactamase. It was determined
that an isolate (K. oxytoca H1) contained a high enzyme concentration (27
mug/100 tg of protein in enzyme extracts), at least 27 times higher than th
e 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) l
eading to enzyme overproduction. Outbreaks caused by K1 hyperproducers have
not previously been described. (C) 2001 The Hospital Infection Society.