Genomic Features ofVibrio parahaemolyticusfrom Lebanon and Comparison to Globally Diverse Strains by Whole-Genome Sequencing

Spotlight on the epidemiology and antimicrobial susceptibility profiles of Vibrio species in the MENA region, 2000-2023

Recent cholera outbreaks in many countries in the Middle East and North Africa (MENA) region have raised public health concerns and focused attention on the genus Vibrio. However, the epidemiology of Vibrio species in humans, water, and seafood is often anecdotal in this region. In this review, we screened the literature and provided a comprehensive assessment of the distribution and antibiotic resistance properties of Vibrio species in different clinical and environmental samples in the region. This review will contribute to understanding closely the real burden of Vibrio species and the spread of antibiotic-resistant strains in the MENA region. The overall objective is to engage epidemiologists, sanitarians and public health stakeholders to address this problem under the One-health ethos.

Adaptations of Vibrio parahaemolyticus to Stress During Environmental Survival, Host Colonization, and Infection

Vibrio parahaemolyticus (Vp) is an aquatic Gram-negative bacterium that may infect humans and cause gastroenteritis and wound infections. The first pandemic of Vp associated infection was caused by the serovar O3:K6 and epidemics caused by the other serovars are increasingly reported. The two major virulence factors, thermostable direct hemolysin (TDH) and/or TDH-related hemolysin (TRH), are associated with hemolysis and cytotoxicity. Vp strains lacking tdh and/or trh are avirulent and able to colonize in the human gut and cause infection using other unknown factors. This pathogen is well adapted to survive in the environment and human host using several genetic mechanisms. The presence of prophages in Vp contributes to the emergence of pathogenic strains from the marine environment. Vp has two putative type-III and type-VI secretion systems (T3SS and T6SS, respectively) located on both the chromosomes. T3SS play a crucial role during the infection process by causing cytotoxicity and enterotoxicity. T6SS contribute to adhesion, virulence associated with interbacterial competition in the gut milieu. Due to differential expression, type III secretion system 2 (encoded on chromosome-2, T3SS2) and other genes are activated and transcribed by interaction with bile salts within the host. Chromosome-1 encoded T6SS1 has been predominantly identified in clinical isolates. Acquisition of genomic islands by horizontal gene transfer provides enhanced tolerance of Vp toward several antibiotics and heavy metals. Vp consists of evolutionarily conserved targets of GTPases and kinases. Expression of these genes is responsible for the survival of Vp in the host and biochemical changes during its survival. Advanced genomic analysis has revealed that various genes are encoded in Vp pathogenicity island that control and expression of virulence in the host. In the environment, the biofilm gene expression has been positively correlated to tolerance toward aerobic, anaerobic, and micro-aerobic conditions. The genetic similarity analysis of toxin/antitoxin systems of Escherichia coli with VP genome has shown a function that could induce a viable non-culturable state by preventing cell division. A better interpretation of the Vp virulence and other mechanisms that support its environmental fitness are important for diagnosis, treatment, prevention and spread of infections. This review identifies some of the common regulatory pathways of Vp in response to different stresses that influence its survival, gut colonization and virulence.

Identification of Pathogenic Variations in Seafood Vibrio parahaemolyticus Isolates by Comparing Genome Sequences

ABSTRACT

An investigation of the pathogenic characteristics of isolates of Vibrio parahaemolyticus was conducted by identifying the pathogenic tdh gene and then performing adherence and cytotoxicity assays. Genome sequences of the seafood isolates were analyzed using the Illumina HiSeq 2500 platform. The isolated strains were then mapped by comparing the genomes to the reference genome, and variations in the nucleotide sequences and amino acids were identified with the CLC Genomics Workbench program. The tdh gene was identified in four isolates of V. parahaemolyticus, of which three-SMFM201809-CPC7-3, SMFM201809-CF8-2, and SMFM201809-CF8-3-showed high cytotoxicity and differences in cell adhesion. These isolates were selected to identify virulence factors and genomic variations. All three isolates had the same virulence factors, such as adherence, secretion system, and toxin. In addition, amino acid variants were identified in the regions of type IV pilus, T3SS1 and T3SS1 secreted effectors, and thermolabile hemolysin. These results indicate that variations in amino acids found in regions related to adherence and cytotoxicity result in differences in adhesion efficiency and cytotoxicity; therefore, the isolates with these variations may cause more serious foodborne illness compared with other strains.

HIGHLIGHTS

Food-Borne Vibrio parahaemolyticus in China: Prevalence, Antibiotic Susceptibility, and Genetic Characterization

Vibrio parahaemolyticus is a marine and estuarine bacterium that leads to damage of aquatic industry by foodborne outbreaks and possesses an enormous threat to food safety as well as human health worldwide. In the current study, we investigated 905 food samples (ready-to-eat foods, fish, and shrimp) from 15 provinces in China, and aimed to determine prevalence, biological characteristics and genetic diversity of presumptive V. parahaemolyticus isolates. Firstly, 14.17% of 240 fish samples, 15.34% of 365 shrimp samples and 3.67% of 300 RTE food samples were positive for potential V. parahaemolyticus. Secondly, 69 food samples (14.87%) collected in summer were positive for target isolates, while the rate of positive sample of 441 food samples in winter reached 7.26%. Thirdly, we purified 202 V. parahaemolyticus strains for further research. And antimicrobial susceptibility results of strains tested revealed that the highest resistance rate was observed for ampicillin (79.20%). At the same time, 148 (73.27%) of all isolates were classified and defined as multi-drug resistant foodborne bacteria. The results of PCR assay showed that the isolates being positive for the tdh, trh or both genes, were up to 9.90%, 19.80% or 3.96%. Besides, multiplex PCR test showed that the isolates carrying O2 serogroup were the most prevalent. Furthermore, sequence types (STs) of 108 isolates were obtained via multi-locus sequence typing. Not only 82 STs were detected, but also 41 of which were updated in the MLST database. Thus, our findings significantly demonstrated the high contamination rates of V. parahaemolyticus in fish and shrimp and it may possess potential threat for consumer health. We also provided up-to-date dissemination of antibiotic-resistant V. parahaemolyticus which is important to ensure the high efficacy in the treatment of human and aquatic products infections. Lastly, with the identification of 82 STs including 41 novel STs, this study significantly revealed the high genetic diversity among V. parahaemolyticus. All of our research improved our understanding on microbiological risk assessment in ready-to-eat foods, fish, and shrimp.