Role of CRISPR-Cas system on antibiotic resistance patterns of Enterococcus faecalis

Pourya Gholizadeh,Hadi Feizi,Longzhu Cui,Reza Ghotaslou,Mohammad Ahangarzadeh Rezaee,Hossein Samadi Kafil,Shinya Watanabe,Mohammad Aghazadeh,Hiva Kadkhoda,Tahereh Pirzadeh

doi:10.1186/s12941-021-00455-6

Abstract

Clustered regularly interspaced short palindromic repeat (CRISPR)-Cas systems are one of the factors which can contribute to limiting the development and evolution of antibiotic resistance in bacteria. There are three genomic loci of CRISPR-Cas in Enterococcus faecalis. In this study, we aimed to assess correlation of the CRISPR-Cas system distribution with the acquisition of antibiotic resistance among E. faecalis isolates. A total of 151 isolates of E. faecalis were collected from urinary tract infections (UTI) and dental-root canal (DRC). All isolates were screened for phenotypic antibiotic resistance. In addition, antibiotic resistance genes and CRISPR loci were screened by using polymerase chain reaction. Genomic background of the isolates was identified by random amplified polymorphic DNA (RAPD)-PCR. The number of multidrug-resistant E. faecalis strains were higher in UTI isolates than in DRC isolates. RAPD-PCR confirmed that genomic background was diverse in UTI and DRC isolates used in this study. CRISPR loci were highly accumulated in gentamycin-, teicoplanin-, erythromycin-, and tetracycline-susceptible strains. In concordance with drug susceptibility, smaller number of CRISPR loci were identified in vanA, tetM, ermB, aac6’-aph(2”), aadE, and ant(6) positive strains. These data indicate a negative correlation between CRISPR-cas loci and antibiotic resistance, as well as, carriage of antibiotic resistant genes in both of UTI and DRC isolates.

Highlights

Over the past decades, commensal bacteria and opportunistic pathogens including Enterococcus spp. have been considered as serious public health threats, and the therapeutic options have become limited
A total of 144 isolates of E. faecalis were collected: 75 isolates were from urinary tract infections (UTIs) and 69 isolates were from dental-root canal (DRC) infections
A total of 144 isolates of E. faecalis were included in the study, 75 isolates were from urinary tract infections (UTIs) and 69 isolates were from dental-root canal (DRC) infections

Summary

Introduction

Commensal bacteria and opportunistic pathogens including Enterococcus spp. have been considered as serious public health threats, and the therapeutic options have become limited. Enterococcus spp. are gram-positive, facultative anaerobes, catalasenegative cocci, which are found in a variety environments such as nature, water, soil, food, avian, mammalian, and human gastrointestinal tracts [1]. The important species within the genus Enterococcus are E. faecalis and E. faecium, which have been reported to be opportunistic pathogens for up to 90 % of human enterococcal infections [2]. Antibiotic resistance in enterococci is a challenge in the clinical setting, and reduces the efficacy of treatment of Enterococcal infectious diseases [6]. Enterococci can transfer antibiotic resistance to other bacteria through mobile genetic elements such as transposons and plasmids [6]. Owing to highly efficient mechanisms of enterococci for the distribution and acquisition of antibiotic resistance

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