Risk factors for colonization and infection in a hospital outbreak caused by a strain of Klebsiella pneumoniae with reduced susceptibility to expanded-spectrum cephalosporins

Between February 2001 and January 2002, an increase in the number of Klebsiella pneumoniae isolates with reduced susceptibility to expanded-spectrum cephalosporins (RSKp) was detected in the neonatal unit of the Juan Canalejo Hospital, and 21 patients were either colonized or infected by the bacterial isolates. The current "gold standard" method for typing K. pneumoniae isolates is pulsed-field gel electrophoresis. However, this technique is expensive and time-consuming. In a search for faster and accurate alternatives to this method, we investigated PCR-based fingerprinting techniques (enterobacterial repetitive intergenic consensus sequence PCR [ERIC-PCR], repetitive extragenic palindromic sequence-based PCR [REP-PCR], and RAPD [randomly amplified polymorphic DNA]) for their ability to characterize K. pneumoniae isolates. The causal agent of the nosocomial outbreak was characterized by these techniques and was found to be a single epidemic strain (RSKp). A multiple regression logistic model was developed to identify potential independent factors associated with colonization and/or infection by RSKp. Logistic regression analysis was applied to all significant variables (P < 0.05) in the univariate analysis, and it was revealed that intubation (odds ratio [OR], 27.0; 95% confidence interval [95%CI], 5.39 to 135.14) and prematurity (OR, 4.4; 95%CI, 0.89 to 21.89) were such independent factors. Moreover, oxime cephalosporins did not appear to be statistically significant. Overall, the results showed that PCR-based techniques are expeditious and useful methods for typing K. pneumoniae isolates. Of the techniques studied, ERIC-PCR showed the highest discriminatory index (D = 0.828), followed by RAPD (D = 0.826) and REP-PCR (D = 0.773)

Molecular investigation of two clusters of hospital-acquired bacteraemia caused by multi-resistant Klebsiella pneumoniae using pulsed-field gel electrophoresis and in frequent restriction site PCR. Infection Control Group

Two molecular typing methods, DNA macrorestriction analysis with XbaI resolved by pulsed-field gel electrophoresis (PFGE) and infrequent restriction site PCR (IRS-PCR) assay with adapters designed for XbaI and HhaI restriction sites, were used to investigate two clusters of hospital-acquired bacteraemia associated with multi-resistant Klebsiella pneumoniae which occurred in a paediatric intensive care unit (PICU). A total of 56 K. pneumoniae isolates were analysed. These included 10 bacteraemic isolates from eight patients, 26 isolates obtained during an epidemiological survey, and 20 epidemiologically non-related isolates incorporated as controls. One major pattern was demonstrated in 22 of the 56 isolates analysed. These included nine of the 10 bacteraemic isolates, a single rectal isolate, two hand culture isolates 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 bacteraemia appeared to be outbreaks induced by the same strain of K. pneumoniae which may have utilized sinks as reservoirs and been transmitted through the hands of medical personnel to patients. IRS-PCR demonstrates concordant results with PFGE analysis in studying the genetic relationships among K. pneumoniae isolates, and serves as an excellent epidemiological tool for this bacterium.