Competence for Natural Transformation Is Common among Clinical Strains of Resistant Acinetobacter spp.

Ângela Cândido,Gabriela Da Silva,Sara Domingues,Daniela Neto,Natasha Rosário,Kaare Nielsen

doi:10.3390/microorganisms7020030

Ângela Cândido, Gabriela Da Silva + Show 4 more

Open Access

https://doi.org/10.3390/microorganisms7020030

Copy DOI

Abstract

Horizontal gene transfer events provide the basis for extensive dissemination of antimicrobial resistance traits between bacterial populations. Conjugation is considered to be the most frequent mechanism behind new resistance acquisitions in clinical pathogens but does not fully explain the resistance patterns seen in some bacterial genera. Gene transfer by natural transformation has been described for numerous clinical isolates, including some Acinetobacter species. The main aim of this study was to determine to what extent clinical, resistant Acinetobacter spp. isolates, express competence for natural transformation. Twenty-two clinical Acinetobacter spp. isolates collected over a 16-year time period, from five different geographical separated and/or distinct Portuguese Hospitals were tested for natural transformability. Fourteen isolates, including 11 A. baumannii, 2 A. nosocomialis and 1 Acinetobacter sp., were identified as competent on semisolid media facilitating surface-motility. Competent Acinetobacter isolates were found in all the hospitals tested. Furthermore, osmolarity was shown to influence the uptake of exogenous DNA by competent A. baumannii A118. Our study demonstrates that natural competence is common among clinical isolates of Acinetobacter spp., and hence likely an important trait for resistance acquisition.

Highlights

Antimicrobial resistance is considered a major threat to public health [1]
A. baumannii has emerged as an important nosocomial pathogen, and nowadays some strains are only susceptible to carbapenems and colistin [4]
The majority were identified as A. baumannii (n = 11), the most relevant nosocomial species, while two were A. nosocomialis and one isolate could not be identified to the species level

Summary

Introduction

Antimicrobial resistance is considered a major threat to public health [1]. Most pathogenic microorganisms have acquired some resistance to many of the commonly used antibiotics. Among these are the so-called ESKAPE pathogens, which include Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa and Enterobacter spp. These are highly important nosocomial pathogens that are becoming resistant to the majority of the available antibiotics. A. baumannii has emerged as an important nosocomial pathogen, and nowadays some strains are only susceptible to carbapenems and colistin [4]. Due to the lack of therapeutic options, this species has been classified as critical in the priority pathogens list released by the World Health Organization in 2017 [5]

Objectives

Methods

Results