First Experimental Evidence for the Presence of Potentially Toxic Vibrio cholerae in Snails, and Virulence, Cross-Resistance and Genetic Diversity of the Bacterium in 36 Species of Aquatic Food Animals.

Dailing Chen,Yingwei Xu,Xiangyi Li,Ling Ni,Lanming Chen,Yong Ding,Dingxiang Xu,Lu Xie

doi:10.3390/antibiotics10040412

Abstract

Vibrio cholerae is the most common waterborne pathogen that can cause pandemic cholera in humans. Continuous monitoring of V. cholerae contamination in aquatic products is crucial for assuring food safety. In this study, we determined the virulence, cross-resistance between antibiotics and heavy metals, and genetic diversity of V. cholerae isolates from 36 species of aquatic food animals, nearly two-thirds of which have not been previously detected. None of the V. cholerae isolates (n = 203) harbored the cholera toxin genes ctxAB (0.0%). However, isolates carrying virulence genes tcpA (0.98%), ace (0.5%), and zot (0.5%) were discovered, which originated from the snail Cipangopaludina chinensis. High occurrences were observed for virulence-associated genes, including hapA (73.4%), rtxCABD (68.0–41.9%), tlh (54.2%), and hlyA (37.9%). Resistance to moxfloxacin (74.9%) was most predominant resistance among the isolates, followed by ampicillin (59.1%) and rifampicin (32.5%). Approximately 58.6% of the isolates displayed multidrug resistant phenotypes. Meanwhile, high percentages of the isolates tolerated the heavy metals Hg2+ (67.0%), Pb2+ (57.6%), and Zn2+ (57.6%). Distinct virulence and cross-resistance profiles were discovered among the V. cholerae isolates in 13 species of aquatic food animals. The ERIC-PCR-based genome fingerprinting of the 203 V. cholerae isolates revealed 170 ERIC-genotypes, which demonstrated considerable genomic variation among the isolates. Overall, the results of this study provide useful data to fill gaps for policy and research related to the risk assessment of V. cholerae contamination in aquatic products.

Highlights

The results revealed that V. cholerae was present in only 13 species of aquatic animals, including six species of fish (Aristichthys nobilis, Carassius auratus, Lateolabrax japonicas, M. anguillicaudatus, Mylopharyngodon piceus, and Parabramis pekinensis), three species of shellfish (G. scallop, Ostrea gigas Thunberg, and Solen strictus), three species of snails
Our results provided additional evidence to demonstrate high detection frequencies of V. cholerae in fish species such as A. nobilis, C. auratus, and P. pekinensis, consistent with results of our prior research [6,9]
The results indicated that the V. cholerae isolates originating from the 4 types and 13 species of aquatic food animals had different heavy metal tolerance profiles

Summary

Introduction

Vibrio cholerae is the causative agent of cholera, a life-threatening diarrheal disease that is typically transmitted via contaminated water and person-to-person contact [1]. The bacterium has caused seven cholera pandemics since 1817 [2]. The seventh pandemic, which erupted in 1961, has lasted for over 50 years [3]. It is estimated that around 2.86 million cholera cases occur globally every year, claiming 120,000 lives. About 1.3 billion people are currently at risk of infection from cholera [4]. According to World Health Organization (WHO) reports, cholera has remained endemic in developing countries in recent years (https://www.who.int/, accessed on 26 July 2020), where sanitation conditions are poor and drinking water unsafe

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