Spreading of Pandemic Vibrio parahaemolyticus O3:K6 and Its Serovariants: A Re-analysis of Strains Isolated from Multiple Studies

Abstract

In China, V. parahaemolyticus has been a leading cause of foodborne outbreaks and bacterial infectious diarrhea since the 1990s, and most infections have been associated with the pandemic V. parahaemolyticus O3:K6 and its serovariants. However, a comprehensive overview of the sero-prevalence and genetic diversity of the pandemic V. parahaemolyticus clone in China is lacking. To compensate for this deficiency, pandemic isolates in both clinical and environmental Chinese samples collected from multiple studies were analyzed in this study. Surprisingly, as many as 27 clinical pandemic serovariants were identified and were widely distributed across nine coastal provinces and two inland provinces (Beijing and Sichuan). O3:K6, O4:K68, and O1:KUT represented the predominant clinical serovars. Only four environmental pandemic serovariants had previously been reported, and they were spread throughout Shanghai (O1:KUT, O3:K6), Jiangsu (O3:K6, O4:K48), Zhejiang (O3:K6), and Guangdong (O4:K9). Notably, 24 pandemic serovariants were detected within a short time frame (from 2006 to 2012). The pandemic isolates were divided into 15 sequence types (STs), 10 of which fell within clonal complex (CC) 3. Only three STs (ST3, ST192, and ST305) were identified in environmental isolates. Substantial serotypic diversity was mainly observed among isolates within pandemic ST3, which comprised 21 combinations of O/K antigens. The pandemic O3:K6 serotype showed a high level of sequence diversity, which was shared by eight different STs (ST3, ST227, ST431, ST435, ST487, ST489, ST526, and ST672). Antimicrobial susceptibility testing revealed that most isolates shared similar antibiotic susceptibility profiles. They were resistant to ampicillin but sensitive to most other drugs that were tested. In conclusion, the high levels of serotypic and genetic diversity of the pandemic clone suggest that the involved regions are becoming important reservoirs for the emergence of novel pandemic strains. We underscore the need for routine monitoring to prevent pandemic V. parahaemolyticus infection, which includes monitoring antimicrobial responses to avoid excessive misuse of antibiotics. Further investigations are also needed to delineate the specific mechanisms underlying the possible seroconversion of pandemic isolates.

De Novo Sequencing Provides Insights Into the Pathogenicity of Foodborne Vibrio parahaemolyticus

“…The antibiotic tests showed different results from those reported in previous studies. The resistance of V. parahaemolyticus environmental isolates to AMP was fully confirmed and is consistent with findings of previous studies (Han et al, 2017;Jiang et al, 2019). However, the resistance of V. parahaemolyticus environmental isolates to quinolones and cephalosporins, especially to CAZ and CIP, which was confirmed by Lopatek et al (Lopatek et al, 2018), could not be established by this method.…”

Insight Into the Origin and Evolution of the Vibrio parahaemolyticus Pandemic Strain

“…From 1996 to 2007, up to 22 pandemic serovariants were identified around the world ( Nair et al, 2007 ). The latest report increased this number to 27 ( Han et al, 2017 ), suggesting that the pandemic isolates could easily adopt new serotypes to survive in new environments. Whole-genome sequence analysis of three pandemic isolates, including one with a different serotype (O4:K68) ( Chen et al, 2011 ), showed high similarity along the whole genome in this clonal complex except in the O- and K-antigen-encoding gene clusters, which contained 94% of the SNVs.…”

“…In general, these analyses together with eBurst ( Feil et al, 2004 ) showed that most pandemic strain isolates cluster within a single clonal complex (CC3), with most showing the founder single sequence ST3 and multiple single and double locus variants (SLV and DSV). Recent MLST analysis of isolates from China showed 15 sequence types, revealing increasing genetic diversity among pandemic isolates, 10 of which fell within CC3 ( Han et al, 2017 ). The isolates also showed frequent recombination among the genes or loci included in the MLST.…”

Simultaneous Identification of Clinically Common Vibrio parahaemolyticus Serotypes Using Probe Melting Curve Analysis

“…Therefore, the current assay presents a simple and pragmatic scheme for the rapid and accurate identification of V. parahaemolyticus serotypes, which is especially suited for real-time applications such as outbreak situations involving large number of samples be processed quickly in a short period of time. In developing this assay, we chose 11 V. parahaemolyticus serotypes that represented 90% of all serotypes isolated from human infections over a 10-year period (2007–2017) in Shenzhen, China; many of which are also commonly reported among infections domestically (Han et al, 2017) and worldwide (Velazquez-Roman et al, 2014; Han et al, 2016). Given its clinical relevance, the current assay could serve as an invaluable tool for clinical and public health laboratories.…”

“…To date, the pandemic clone and its serovariants are known to represent 49 serotypes, which are widely distributed among 22 countries in Asia, Europe, America and Africa (Han et al, 2016). In China, up to 27 pandemic serovariants have been found amongst clinical samples, in which O3:K6, O4:K68, and O1:KUT predominated (Han et al, 2017). Hence, the serotyping of V. parahaemolyticus has played a pivotal role in significantly advancing our understanding of its epidemiology.…”