Endemic and epidemic Acinetobacter baumannii clones: a twelve-year study in a tertiary care hospital.

Montserrat Ortega,María J Medina-Pascual,Pilar Villalón,Ana Vindel,Teresa Cabezas,Juan A Saez-Nieto,Sylvia Valdezate,Noelia Garrido

doi:10.1186/s12866-015-0383-y

Abstract

BackgroundNosocomial outbreaks of multidrug-resistant Acinetobacter baumannii are of worldwide concern. Using pulsed-field gel electrophoresis (PFGE), multilocus sequence typing (MLST), and multiple locus variable number tandem repeat sequence (VNTR) analysis (MLVA), the present work examines the genetic diversity of the endemic and epidemic A. baumannii clones isolated in a single hospital over a twelve-year period.ResultsPFGE analysis of 405 A. baumannii-calcoaceticus complex isolates detected 15 A. baumannii endemic/epidemic PFGE types (EE1 to EE15) that grouped into five clusters: EE1-EE8, EE9, EE10, EE11 and EE12-EE15. The MLST sequence type (ST) distributions were: international clone II (ST-2) 60%, international clone III (ST-3) 26.7%, ST-15 6.7%, and ST-80 6.7%. MLVA-8Orsay returned 17 allelic profiles. The large (L) VNTR marker profiles were fully concordant with the detected STs, and concordant with 14 up to 15 PFGE types. Imipenem resistance was detected in five PFGE types; the prevalence of the blaOXA-58-like and blaOXA-40-like genes was 60% and 40% respectively.ConclusionsPFGE proved to be a vital tool for analysis of the temporal and spatial distribution of the clones. MLST and the VNTR L-markers grouped the isolates into clonal clusters. The wide diversity of MLVA small (S)-markers, however, did not permit clustering. The present results demonstrate the persistence of several endemic PFGE types in the hospital, the involvement of some of them in outbreaks, and the inter hospital transmission of extensively drug-resistant ST-15 and ST-80.

Highlights

Nosocomial outbreaks of multidrug-resistant Acinetobacter baumannii are of worldwide concern
The comparison of the three genotyping methods shows that multilocus sequence typing (MLST) is very useful in global A. baumannii clonal studies, clustering the isolates into big clones
MLVA8Orsay L markers provide similar information than MLST, but it has the drawback that no consensus has been reached regarding the interpretation of S markers

Summary

Introduction

Nosocomial outbreaks of multidrug-resistant Acinetobacter baumannii are of worldwide concern. The bacterium Acinetobacter baumannii is very tolerant to desiccation and has developed resistance against many of the antimicrobial agents in common use [1]. Both these features render it ideally suited to survive in the hospital environment, and invest it with the power to cause important nosocomial outbreaks [2]. Multidrug-resistant (MDR) A. baumannii infection is a worldwide health problem that has a negative impact on the morbidity and the mortality of the affected patients [3,4]. A previous study of A. baumannii isolates from Spanish hospitals [13] showed the predominance of international clone II (sequence type 2 [ST-2]). The minor clones detected included international clone III (ST-3), ST-15 and ST-32

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