Molecular investigation of two clusters of hospital-acquired bacteraemia caused by multi-resistant Klebsiella pneumoniae using pulsed-field gel electrophoresis and infrequent restriction site PCR

Two molecular typing methods, DNA macrorestriction analysis with XbaI resol ved by pulsed-field gel electrophoresis (PFGE) and infrequent restriction s ite PCR (IRS-PCR) assay with adapters designed for XbaI and HhaI restrictio n sites, were used to investigate two clusters of hospital-acquired bactera emia associated with multi-resistant Klebsiella pneumoniae which occurred i n a paediatric intensive care unit (PICU). A total of 56 K. pneumoniae isol ates were analysed. These included 10 bacteraemic isolates from eight patie nts, 26 isolates obtained during an epidemiological survey and 20 epidemiol ogically non-related isolates incorporated as controls. One major pattern i s as demonstrated in 22 of the 56 isolates analysed. These included nine of the 10 bacteraemic isolates, a single rectal isolate, two hand culture iso lates and 10 sink isolates. All of these 22 isolates illustrated identical antibiograms, whilst; the other 34 isolates shared six antibiograms and 31 unique patterns by either PFGE or IRS-PCR assay The two clusters of bactera emia appeared to be outbreaks induced by the same strain of K. pneumoniae w hich may have utilized sinks as reservoirs and been transmitted through the hands of medical personnel to patients. IRS-PCR demonstrates concordant re sults with PFGE analysis in studying the genetic relationships among K. pne umoniae isolates, and serves as an excellent epidemiological tool for this bacterium. (C) 2000 The Hospital Infection Society.