Abstract
Acinetobacter baumannii is an opportunistic pathogen of intensive care unit (ICU) patients. A. baumannii colonizes many parts of the body including the gastrointestinal tract. Endemic and epidemic strains are polyclonal. There is no clarity on the origin of polyclonality of A. baumannii. The objective of the study was to define the genetic relatedness of serial isolates and the origin of polyclonality. Serial rectal isolates from ICU patients whose rectum was colonized on ≥5 sampling occasions were selected. From a total of 32 eligible colonized patients, isolates from a subgroup of 13 patients (a total of 108 isolates) showing different patterns of colonization as revealed by pulsed-field gel electrophoresis (PFGE) were studied. The isolates were analyzed by PFGE pulsotypes, sequence types (STs) by multi-locus sequence typing (MLST) and clonal complex (CC) by eBURST analysis. Serial isolates constituted a mixture of identical, related and unrelated pulsotypes. Analysis by STs and CCs were less discriminatory. The data suggest a combination of an initial colonizing isolate undergoing mutation as well as colonization by independent isolates. Further clarity on the origin of diversity should be better obtained by whole-genome sequencing.
Highlights
Acinetobacter baumannii causes severe nosocomial infections in critically ill patients and is involved in many hospital outbreaks world-wide
The results of the analysis on 12 patients are shown in S1 Table and sample DiversiLab dendrograms in S1 Fig. Studies of three different colonies from five patients showing a single morphotype revealed that all three colonies were identical by DiversiLab
Single colonies representing each morphotype were studied from the patients from whom serial rectal samples were analyzed
Summary
Acinetobacter baumannii causes severe nosocomial infections in critically ill patients and is involved in many hospital outbreaks world-wide. It colonizes skin and mucous membranes including the gastrointestinal tract [1,2]. This organism has the propensity for acquiring multiple resistance genes with phenotypic expression of multidrug-resistant (MDR) characteristics. Choosing appropriate molecular typing methods is vital for investigating epidemiological lineages of the isolates and for infection control. PFGE is used as a common method for typing A. baumannii isolates [11].
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