Abstract
Vibrio parahaemolyticus is the leading cause of seafood-borne bacterial poisoning in China and is a threat to human health worldwide. The aim of this study was to assess the antibiotic resistance profiles and distribution of heavy metal resistance of V. parahaemolyticus isolates from Penaeus vannamei from freshwater farms, seawater farms, and their corresponding markets in Zhejiang, China and to assess the relationship between multidrug resistance (MDR) and multi-heavy metal resistance (MHMR). Of the 360 P. vannamei samples that we tested, 90 (25.00%) were V. parahaemolyticus positive, but the occurrence of pathogenic isolates carrying the toxin genes tdh (4.44%) and trh (3.33%) was low. None of the tested isolates harbored both the tdh and trh genes. However, antibiotic resistance profiles varied among different sampling locations, levels of resistance to the antibiotics ampicillin (76.67%) and streptomycin (74.44%) were high overall, and MDR isolates were common (40.00% of all isolates). Heavy metal resistance patterns were similar among the different sampling locations. Overall, the majority of V. parahaemolyticus isolates displayed tolerance to Cd2+ (60.00%), and fewer were resistant to Cu2+ (40.00%), Zn2+ (38.89%), Ni2+ (24.44%), Cr3+ (14.44%), and Co2+ (8.89%). In addition, 34.44% (31/90) of isolates tested in this study were found to be MHMR. Using Pearson’s correlation analysis, MDR and MHMR were found to be positively correlated (P = 0.004; R = 0.759). The 18 V. parahaemolyticus isolates that were both MDR and MHMR represented 18 sequence types, of which 12 were novel to the PubMLST database, and displayed a high level of genetic diversity, suggesting that dissemination may be affected by mobile genetic elements via horizontal gene transfer. However, a low percentage of class 1 integrons without gene cassettes and no class 2 or 3 integrons were detected in the 18 MDR and MHMR isolates or in the 90 V. parahaemolyticus isolates overall. Thus, we suggest that future research focus on elucidating the mechanisms that lead to a high prevalence of resistance determinants in V. parahaemolyticus. The results of this study provide data that will support aquatic animal health management and food safety risk assessments in the aquaculture industry.
Highlights
Vibrio parahaemolyticus, which was first identified in 1950 in Osaka, Japan, is a gram-negative, halophilic, mesophilic, aerobic bacterium that is found naturally in warm marine and estuarine habitats and causes outbreaks worldwide (Baker-Austin et al, 2008; Xie et al, 2017; Yang et al, 2017; He et al, 2019)
A total of 360 P. vannamei samples were collected from a freshwater farm, a seawater farm, a market where P. vannamei cultured at farm A is sold and a market where P. vannamei cultured at farm B is sold in Zhejiang Province, China between 2017 and 2019
Only 3 V. parahaemolyticus isolates were detected from 90 samples of freshwater P. vannamei cultured at farm A, where the water salinity was as low as 1.75 ± 0.03 ppt
Summary
Vibrio parahaemolyticus, which was first identified in 1950 in Osaka, Japan, is a gram-negative, halophilic, mesophilic, aerobic bacterium that is found naturally in warm marine and estuarine habitats and causes outbreaks worldwide (Baker-Austin et al, 2008; Xie et al, 2017; Yang et al, 2017; He et al, 2019). Some V. parahaemolyticus isolates are pathogenic to humans and are responsible for many seafood-related human illnesses, such as gastrointestinal illnesses, diarrheal diseases, wound infections, and even septicemia (Devi et al, 2009; Hu and Chen, 2016; Yu et al, 2016). According to the official surveillance statistics of the national foodborne disease surveillance system in China, V. parahaemolyticus is one of the leading causes of foodborne bacterial poisoning in China (Jiang et al, 2019). TDH is a pore-forming, heat-stable protein that remains intact even when heated to 100◦C for 10 min. Unlike the thermostable TDH, TRH is heat labile and can be inactivated by heating at 60◦C for 10 min (Tan et al, 2017)
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