Genomic Characterization of Arcobacter butzleri Isolated From Shellfish: Novel Insight Into Antibiotic Resistance and Virulence Determinants

Abstract

Arcobacter (A.) butzleri is an emerging pathogenic microorganism, whose taxonomy has been recently suggested to be emended to the Aliarcobacter (Al.) butzleri comb. nov. Despite extensive taxonomic analysis, only few fragmented studies have investigated the occurrence and the prevalence of virulence and antibiotic resistance determinants of this species in strains isolated from shellfish. Herein we report for the first time the whole genome sequencing and genomic characterization of two A. butzleri strains isolated from shellfish, with particular reference to the antibiotic, heavy metals and virulence determinants. This study supported the taxonomic assignment of these strains to the Al. butzleri species, and allowed us to identify antibiotic and metal resistance along with virulence determinants, also additional to those previously reported for the only two A. butzleri strains from different environments genomically characterized. Moreover, both strains showed resistance to β-lactams, vanocomycin, tetracycline and erythromycin and susceptibility to aminoglycosides and ciprofloxacin. Beside enlarging the availability of genomic data to perform comparative studies aimed at correlating phenotypic differences associated with ecological niche and geographic distribution with the genetic diversity of A. butzleri spp., this study reports the endowment of antibiotic and heavy metal resistance and virulence determinants of these shellfish-isolated strains. This leads to hypothesize a relatively high virulence of A. butzleri isolated from shellfish and prompt the need for a wider genomic analysis and for in vitro and in vivo studies of more strains isolated from this and other ecological niches, to unravel the mechanism of pathogenicity of this species, and the potential risk associated to their consumption.

Prevalence and antimicrobial susceptibility of Arcobacter species in human stool samples derived from out- and inpatients: the prospective German Arcobacter prevalence study Arcopath

“…Further analyses are needed to determine the genomic background being responsible for the divergent MIC distributions observed by us for Arcobacter spp. As mentioned before, 86% of the investigated Arcobacter isolates showed low MICs for ciprofloxacin ranging from 0.032-0.50 µg/ml, which is further supported by a recent study reporting ciprofloxacin susceptibility for all tested Arcobacter butzleri isolates [36]. In contrast, clinical Campylobacter isolates displayed high resistance rates (MICs ≥ 4 µg/ml) ranging from 45 to 71.4% [39,40].…”

“…Similar to our results, other studies on antimicrobial susceptibility revealed also low MICs for Arcobacter spp. to erythromycin whereas some studies reported resistance rates up to 62% [5,36,37]. In contrast to our study, those studies used disc diffusion assays with 15 µg/disc and applied resistance criteria for Enterobacteriaceae according to CLSI 2010.…”

“…In accordance with our data, only low resistance rates from 0-4% of Arcobacter spp. to gentamicin have been reported before [36]. Similarly, susceptibility to tetracycline might be common, although one recent study from retail food in Portugal demonstrated high resistance (95%) in A. butzleri [5,41].…”

Prevalence and antimicrobial susceptibility of Arcobacter species in human stool samples derived from out- and inpatients: the prospective German Arcobacter prevalence study Arcopath

“…As mentioned before, 86% of the investigated Arcobacter isolates showed low MICs for ciprofloxacin ranging from 0.032-0.50 µg/ml, which is further supported by a recent study reporting ciprofloxacin susceptibility for all tested Arcobacter butzleri isolates (36). In contrast, clinical Campylobacter isolates displayed high resistance rates (MICs ≥ 4 µg/ml) ranging from 45 to 71.4% (39,40).…”

“…Similar to our results, other studies on antimicrobial susceptibility revealed also low MICs for Arcobacter spp. to erythromycin whereas some studies reported resistance rates up to 62% (5,36,37). In contrast to our study, those studies used disc diffusion assays with 15µg/disc and applied resistance criteria for Enterobacteriaceae according to CLSI 2010.…”