Molecular Epidemiology, Virulence Traits and Antimicrobial Resistance Signatures of Aeromonas spp. in the Critically Endangered Iberochondrostoma lusitanicum Follow Geographical and Seasonal Patterns.

Miguel L Grilo,Tiago A Marques,Lélia Chambel,Carla Sousa-Santos,Joana I Robalo,Sara Isidoro,Manuela Oliveira,Carolina S Marques

doi:10.3390/antibiotics10070759

Abstract

Despite the fact that freshwater fish populations are experiencing severe declines worldwide, our knowledge on the interaction between endangered populations and pathogenic agents remains scarce. In this study, we investigated the prevalence and structure of Aeromonas communities isolated from the critically endangered Iberochondrostoma lusitanicum, a model species for threatened Iberian leuciscids, as well as health parameters in this species. Additionally, we evaluated the virulence profiles, antimicrobial resistance signatures and genomic relationships of the Aeromonas isolates. Lesion prevalence, extension and body condition were deeply affected by location and seasonality, with poorer performances in the dry season. Aeromonas composition shifted among seasons and was also different across river streams. The pathogenic potential of the isolates significantly increased during the dry season. Additionally, isolates displaying clinically relevant antimicrobial resistance phenotypes (carbapenem and fluroquinolone resistance) were detected. As it inhabits intermittent rivers, often reduced to disconnected pools during the summer, the dry season is a critical period for I. lusitanicum, with lower general health status and a higher potential of infection by Aeromonas spp. Habitat quality seems a determining factor on the sustainable development of this fish species. Also, these individuals act as reservoirs of important antimicrobial resistant bacteria with potential implications for public health.

Highlights

Among sampled locations, when compared to the Laje location, significantly lower levels of lesion prevalence were observed in individuals originating from Lizandro (p = 0.002) and significantly higher levels of lesion prevalence in individuals originating from Samarra (p < 0.001)
Skin lesions in fishes can have a multifactorial origin, with several possible different agents involved and contribution of Aeromonas spp. to the lesions observed in I. lusitanicum cannot be concluded, the methodology applied in this study can access dynamics of bacterial pathogens with relevance for conservation medicine and, at the same time, serve as an opportunistic basis for the study of antimicrobial resistance and virulence prevalence and temporal shifts with a particular relevance for public health
We show that distinct populations of the critically endangered leuciscid fish I. lusitanicum display differential levels of general health with shifts according to seasons and locations, and that those modifications are accompanied by changes in the Aeromonas structure associated with them

Summary

Introduction

Past geological events that shaped freshwater landscapes in the Iberian Peninsula and promoted its geographical isolation greatly contributed to the high level of endemism currently observed in native leuciscid fishes (Teleostei: Leuciscidae) [1]. In spite of this biotic richness, leuciscids’ populations are following the decreasing trends observed in freshwater species worldwide [2], and around 70% of the known species in the region belonging to this taxonomic group present some level of threat to their conservation [3]. Different factors play a key role as potential threats for the sustainability of leuciscid species. Leuciscids that occur in intermittent streams of the southern part of the Iberian Peninsula are typically subjected to cyclical shifts between winter floods and extremely low water levels during the summer

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