Prevalence of Vibrio parahaemolyticus in seafood products from hypermarkets in Shanghai

Aptamers: A Cutting-Edge Approach for Gram-Negative Bacterial Pathogen Identification

Early and accurate diagnoses of pathogenic microorganisms is essential to correctly identify diseases, treating infections, and tracking disease outbreaks associated with microbial infections, to develop precautionary measures that allow a fast and effective response in epidemics and pandemics, thus improving public health. Aptamers are a class of synthetic nucleic acid molecules with the potential to be used for medical purposes, since they can be directed towards any target molecule. Currently, the use of aptamers has increased because they are a useful tool in the detection of specific targets. We present a brief review of the use of aptamers to detect and identify bacteria or even some toxins with clinical importance. This work describes the advances in the technology of aptamers, with the purpose of providing knowledge to develop new aptamers for diagnoses and treatment of different diseases caused by infectious microorganisms.

Antibiotic Resistance and Genetic Profiles of Vibrio parahaemolyticus Isolated from Farmed Pacific White Shrimp (Litopenaeus vannamei) in Ningde Regions

To better understand the antibiotic resistance, virulence genes, and some related drug-resistance genes of Vibrio parahaemolyticus in farmed pacific white shrimp (Litopenaeus vannamei) in Ningde regions, Fujian province, we collected and isolated a total of 102 strains of V. parahaemolyticus from farmed pacific white shrimp in three different areas of Ningde in 2022. The Kirby-Bauer disk method was used to detect V. parahaemolyticus resistance to 22 antibiotics, and resistant genes (such as quinolones (qnrVC136, qnrVC457, qnrA), tetracyclines (tet A, tetM, tetB), sulfonamides (sulI, sulII, sulIII), aminoglycosides (strA, strB), phenicols (cat, optrA, floR, cfr), β-lactams (carB), and macrolides (erm)) were detected by using PCR. The findings in this study revealed that V. parahaemolyticus was most resistant to sulfamoxazole, rifampicin, and erythromycin, with resistance rates of 56.9%, 36.3%, and 33.3%, respectively. Flufenicol, chloramphenicol, and ofloxacin susceptibility rates were 97.1%, 94.1%, and 92.2%, respectively. In all, 46% of the bacteria tested positive for multi-drug resistance. The virulence gene test revealed that all bacteria lacked the tdh and trh genes. Furthermore, 91.84% and 52.04% of the isolates were largely mediated by cat and sulII, respectively, with less than 5% resistance to aminoglycosides and macrolides. There was a clear mismatch between the antimicrobial resistance phenotypes and genotypes, indicating the complexities of V. parahaemolyticus resistance.

Prevalence, virulence characteristics, and antimicrobial resistance of Vibrio parahaemolyticus isolates from raw seafood in a province in Northern Thailand

Vibrio parahaemolyticus (V. parahaemolyticus) is commonly found in seawater and seafood products, but evidence is limited of its presence in seafood marketed in locations very distant from coastal sources. This study determined the prevalence and characterization of V. parahaemolyticus in seafood from markets in landlocked Phayao province, Northern Thailand. Among 120 samples, 26 (21.7%) were positive for V. parahaemolyticus, being highest in shrimp (43.3%), followed by shellfish (36.7%), and squid (6.7%), but was not found in fish. V. parahaemolyticus comprised 33 isolates that were non-pathogenic and non-pandemic. Almost all isolates from shrimp and shellfish samples were positive for T3SS1. Only five isolates (15.2%) showed two antimicrobial resistance patterns, namely, kanamycin-streptomycin (1) carrying sul2 and ampicillin-kanamycin-streptomycin (4) that carried tetA (2), tetA-sul2 (1), as well as one negative. Antimicrobial susceptible V. parahaemolyticus isolates possessing tetA (67.9%) and sul2 (3.5%) were also found. Six isolates positive for integron class 1 and/or class 2 were detected in 4 antimicrobial susceptible and 2 resistant isolates. While pathogenic V. parahaemolyticus was not detected, contamination of antimicrobial resistance V. parahaemolyticus in seafood in locations distant from coastal areas requires ongoing monitoring to improve food safety in the seafood supply chain.

Rapid visual detection of Vibrio parahaemolyticus by combining LAMP-CRISPR/Cas12b with heat-labile uracil-DNA glycosylase to eliminate carry-over contamination

Vibrio parahaemolyticus is a major pathogen frequently found in seafood. Rapid and accurate detection of this pathogen is important for the control of bacterial foodborne diseases and to ensure food safety. In this study, we established a one-pot system that combines uracil-DNA glycosylase (UDG), loop-mediated isothermal amplification (LAMP), and clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 12b (Cas12b) for detecting V. parahaemolyticus in seafood. This detection system can effectively perform identification using a single tube and avoid the risk of carry-over contamination.

Presence, Seasonal Distribution, and Biomolecular Characterization of Vibrio parahaemolyticus and Vibrio vulnificus in Shellfish Harvested and Marketed in Sardinia (Italy) between 2017 and 2018

ABSTRACT

In the present study, we investigated the presence, seasonal distribution, and biomolecular characteristics of Vibrio parahaemolyticus and Vibrio vulnificus in samples of bivalve mollusks (Mytilus galloprovincialis, Crassostrea gigas, and Ruditapes decussatus) harvested and marketed in Sardinia (Italy) between 2017 and 2018. A total of 435 samples were submitted for qualitative determination of Vibrio spp., V. parahaemolyticus, and V. vulnificus. Potentially enteropathogenic isolates were detected with biomolecular methods. The overall prevalence of Vibrio spp. was 7.6%. The highest Vibrio prevalence was found in R. decussatus (8.3%). The prevalences of V. parahaemolyticus and V. vulnificus were 2.7 and 4.8%, respectively. Higher prevalences of V. parahaemolyticus and V. vulnificus were found in R. decussatus (4.2%) and C. gigas (6.2%), respectively. Only two pathogenic V. parahaemolyticus strains were recovered (genotypes: tdh- and trh+; tdh+ and trh-), both from M. galloprovincialis. None of the isolates were tdh+ and trh+. Pathogenic Vibrio infections are often underestimated, and human infections are increasing in Europe. European data on the true distribution of Vibrionaceae are scarce, and the results of the present study highlight the need of constant monitoring to update the distribution of pathogenic vibrios.

HIGHLIGHTS

Virulence, resistance, and genetic diversity of Vibrio parahaemolyticus recovered from commonly consumed aquatic products in Shanghai, China

Vibrio parahaemolyticus can cause severe gastroenteritis, septicaemia and even death in humans. Continuous monitoring of V. parahaemolyticus contamination in aquatic products is imperative for ensuring food safety. In this study, we isolated and characterized 561 V. parahaemolyticus strains recovered from 23 species of commonly consumed shellfish, crustaceans, and fish collected in July and August of 2017 in Shanghai, China. The bacterium was not isolated from two fish species Carassius auratus and Parabramis pekinensis. The results revealed a very low occurrence of pathogenic V. parahaemolyticus carrying the toxin genes trh (0.2%) and tdh (0.0%). However, high percentages of resistance to the antimicrobial agents ampicillin (93.0%), rifampin (82.9%), streptomycin (75.4%) and kanamycin (50.1%) were found. A high incidence of tolerance to the heavy metals Hg²⁺ (74.7%) and Zn²⁺ (56.2%) was also observed in the isolates. ERIC-PCR-based fingerprinting of MDR isolates (77.5%) revealed 428 ERIC-genotypes, demonstrating remarkable genetic variation among the isolates. The results of this study support the urgent need for food safety risk assessment of aquatic products.

Microevolution of Vibrio parahaemolyticus Isolated from Clinical, Acute Hepatopancreatic Necrosis Disease Infecting Shrimps, and Aquatic Production in China

Vibrio parahaemolyticus is the leading cause of bacteria-associated foodborne diarrheal diseases and specifically causes early mortality syndrome (EMS), which is technically known as acute hepatopancreatic necrosis disease (AHPND), a serious threat to shrimp aquaculture. To investigate the genetic and evolutionary relationships of V. parahaemolyticus in China, 184 isolates from clinical samples (VPC, n=40), AHPND-infected shrimp (VPE, n=10), and various aquatic production sources (VPF, n=134) were collected and evaluated by a multilocus sequence analysis (MLST). Furthermore, the presence of potential virulence factors (tlh, tdh, and trh) and single nucleotide polymorphisms (SNPs) in V. parahaemolyticus isolates was assessed using genomic sequencing. Analyses of virulence factors revealed that the majority of VPC isolates (97.5%) possessed the tdh and/or trh genes, while most of the VPF isolates (83.58%) did not encode hemolysin genes. Therefore, we hypothesized that the environment is a potential reservoir that promotes horizontal DNA transfer, which drives evolutionary change that, in turn, leads to the emergence of novel, potentially pathogenic strains. Phylogenetic analyses identified VPF-112 as a non-pathogenic maternal strain isolated from aquatic products and showed that it had a relatively high evolutionary status. All VPE strains and some VPC strains were grouped into several small subgroups and evenly distributed on phylogenetic trees. Anthropogenic activities and environmental selective pressure may be important factors influencing the process of transforming strains from non-pathogenic to pathogenic bacteria.

Simple Colorimetric Assay for Vibrio parahaemolyticus Detection Using Aptamer-Functionalized Nanoparticles

Simple, rapid, and sensitive screening methods are the key to prevent and control the spread of foodborne diseases. In this study, a simple visual colorimetric assay using magnetic nanoparticles (MNPs) and gold nanoparticles (AuNPs) was developed for the detection of Vibrio parahaemolyticus. First, the aptamer responding to V. parahaemolyticus was conjugated onto the surface of MNPs and used as a specific magnetic separator. In addition, the aptamer was also immobilized on the surface of AuNPs and used as a colorimetric detector. In the presence of V. parahaemolyticus, a sandwich structure of MNP-aptamer-bacteria-aptamer-AuNPs is formed through specific recognition of the aptamer and V. parahaemolyticus. The magnetic separation technique was then applied to generate a detection signal. Owing to the optical properties of AuNPs, a visual signal could be observed, resulting in an instrument-free colorimetric detection. Under optimal conditions, this assay shows a linear response toward V. parahaemolyticus concentration through the range of 10-106 cfu/mL, with a limit of detection of 2.4 cfu/mL. This method was also successfully applied for V. parahaemolyticus detection in spiked raw shrimp samples.

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.

Prevalence and genetic diversity of Vibrio parahaemolyticus strains from salmon in Chinese markets

Consumption of contaminated salmon in China has led to pathogenic Vibrio parahaemolyticus infections in humans. In this study, 420 salmon samples were collected from supermarkets and restaurants in China that showed a contamination rate of 9.05 and 15.24%, respectively. Eighteen antibiotics were used to test the antibiotic susceptibility of all 51 isolates. The most common resistance was observed to β-lactam antibiotics and aminoglycosides, including ampicillin (92.16%), streptomycin (88.24%), kanamycin (45.10%) and cephazolin (45.10%). Meanwhile, many strains were resistant to more than two antibiotics (48/51, 94.12%). Only two and five isolates were positive for tdh and trh, respectively. Serotyping results demonstrated that O2 was most prevalence serotype (15/51, 29.41%). Molecular typing (enterobacterial repetitive intergenic consensus sequence polymerase chain reaction and multilocus sequence typing) allowed classification of all the isolates into 5 clusters and 44 sequence types, highlighting genetic variation and relatedness. In general, the high antibiotic resistance is alarming and raises public health concerns. Frequent monitoring of salmon for V. parahaemolyticus contamination, genetic diversity and antibiotic susceptibility is essential to improve seafood safety.

Rapid identification and detection of Vibrio parahaemolyticus via different types of modus operandi with LAMP method in vivo

Purpose

Vibrio parahaemolyticus, an easy-ignored food-borne pathogen, can cause bacterial outbreaks and human disease during early-stage infection. In this study, we aimed to evaluate the detection efficiency of loop-mediated isothermal amplification (LAMP) as an emerging technique to directly detect V. parahaemolyticus infection in mammalian hosts and assess its potential in clinical applications.

Methods

A LAMP assay was used for rapid identification of V. parahaemolyticus in a variety of mouse models in which animals were infected via the digestive tract, wounds, or through general infection, and the results were compared with routine analytical methods.

Results

Our results confirmed that the LAMP assay was capable of detecting V. parahaemolyticus in different mouse organs independent of the source of bacteria, although its sensitivity depended on the route of infection and the organ affected. Foodborne-derived V. parahaemolyticus was the most sensitive route, with the small intestine being the most sensitive organ. The LAMP assay indicated that V. parahaemolyticus that spread through the blood stream had the most serious consequences during early-stage infection. Positive LAMP results were identified in all blood samples from i.v. injected mice. Furthermore, the LAMP method could directly detect trace quantities of V. parahaemolyticus in fresh peripheral blood while conventional methods failed to do so, thereby shortening the time-to-result from days to minutes.

Conclusions

In this study, we demonstrated that the LAMP assay was effective in speeding up the detection of V. parahaemolyticus. Instead of being a secondary method to assist in the clinic, the LAMP assay has potential for use as the primary technique for rapid detection of V. parahaemolyticus in the future.

An improved recombinase polymerase amplification assay for visual detection of Vibrio parahaemolyticus with lateral flow strips

Vibrio parahaemolyticus is an important pathogenic bacterium in both food safety management and mariculture. Rapid and accurate detection technologies are critical for effective control of its outbreak and spreading. Conventional technologies and polymerase chain reaction (PCR)-based approaches have limited usage because of the requirement of laboratory instruments and trained personnel. Using the isothermal recombinase polymerase amplification (RPA) technology, several detection assays have been developed with added convenience. Combining the lateral flow strip (LFS) test with RPA can further simplify the detection. In this study, an improved RPA assay using LFS for visual detection of V. parahaemolyticus was developed. Primers were designed targeting the virulence genes and screened for amplification efficiency, nonspecific amplification, and primer-dimer formation. Probes were designed for the best primer pairs, and the weakness of LFS tests, being easily affected by primer-dependent artifacts, was overcome by sequence modifications on primers and probe. The RPA-LFS assay took 25 min at 35 to 45 °C, and showed excellent specificity. It detected as low as one colony forming unit (CFU) of V. parahaemolyticus per reaction without DNA purification, or 10 CFU/10 g spiked food samples with 2 hr of enrichment. The detection limit was better than the currently available RPA-based detection methods. Application of the RPA-LFS assay for simulated samples or real clinical samples showed accurate and consistent detection results compared to bioassay and quantitative PCR. The RPA-LFS assay provided a rapid, accurate, and convenient V. parahaemolyticus detection method suitable for on-site detection in resource-limited conditions. PRACTICAL APPLICATION: This research developed a rapid and visual detection technology for Vibrio parahaemolyticus that is not dependent on complicated equipment. The detection process takes 25 min and the result is read with the naked eye. A detection kit can be developed based on this technology for on-site detection of V. parahaemolyticus in resource-limited regions for food safety management and mariculture.

Rapid visualized isothermal nucleic acid testing of Vibrio parahaemolyticus by polymerase spiral reaction

The aim of this study was to develop an effective and specific visual method to rapidly detect and identify Vibrio parahaemolyticus (V. parahaemolyticus) based on the polymerase spiral reaction (PSR). The method utilized only two pairs of primers designed specifically to target the conserved tlh gene sequence of V. parahaemolyticus. Nucleic acid amplification can be achieved under isothermal conditions using DNA polymerase. The reaction could be accomplished in < 40 min with high specificity and sensitivity. The limits of detection of V. parahaemolyticus in purified genomic DNA and pure culture were 300 fg/μL and 2.4 CFU/mL per reaction, respectively, which were 100-fold more sensitive than with conventional PCR. The model food samples showed consistent specificity and sensitivity to the pure bacterial culture. With these encouraging results, it is expected that the novel, effortless and reliable isothermal nucleic acid testing assay developed in this study has potential to be applied to screening for V. parahaemolyticus in seafood samples.

Exposure Assessment and Sensitivity Analysis for Chilled Shrimp During Distribution: A Case Study of Home Delivery Services in Taiwan

In this study, we evaluated the temperature requirements for home delivery in Taiwan by considering food safety risks of chilled shrimp that may be contaminated with Vibrio parahaemolyticus. Pathogenic V. parahaemolyticus was chosen because it was the main cause of foodborne outbreaks originating from contaminated seafood in Taiwan. The risk of becoming ill due to consumption of raw shrimp was estimated to be 7.3 × 10^-3 per serving, estimated based on the real-time temperature profile. Lowering the maximum temperature to 7 °C during transit and cooking shrimps at 100 °C for 5 min could reduce the risk by more than 94%. These interventions, therefore, were suggested to be used as an integral part of temperature management control in the home delivery cold chain. These findings can help food authorities to institute temperature management policies and regulations to prevent broken cold chains and reduce food safety risks. PRACTICAL APPLICATION: This research may be applicable to home delivery services that deliver low-temperature food products, such as seafood products.

Reduction of infection risk mediated by co-culturing Vibrio parahaemolyticus and Listeria monocytogenes in refrigerated cooked shrimp

BACKGROUND

Vibrio parahaemolyticus and Listeria monocytogenes are seafood pathogens of public health significance, and predictive models are effective tools for quantitative microbial risk assessment of these pathogens. However, most current predictive models are based on growth of single strains in broth cultures, and interactions of two or more bacteria in a food matrix can skew the outcomes of the predictions. Therefore, the impact of V. parahaemolyticus and L. monocytogenes when co-cultured and in monoculture on cooked shrimp in cold storage was investigated.

RESULTS

The results indicated that L. monocytogenes co-cultured with V. parahaemolyticus exhibited reduced growth and longer lag phase at 4 °C and 10 °C. V. parahaemolyticus exhibited similar behavior when co-cultured with L. monocytogenes at 4 °C (death rate K =  - 0.67 log₁₀ CFU g^-1 day . The death rate K at 10 °C when V. parahaemolyticus co-cultured with L. monocytogenes was -1.62 log₁₀ CFU g^-1 day^-1 . There was no significant reduction of growth in monoculture experiments.

CONCLUSION

This study has revealed that interaction of V. parahaemolyticus and L. monocytogenes should be considered when quantifying risks posed by these pathogens during consumption of seafood products. © 2018 Society of Chemical Industry.

A Novel qPCR Method for Simultaneous Detection and Quantification of Viable Pathogenic and Non-pathogenic Vibrio parahaemolyticus (tlh+ , tdh+ , and ureR + )

Pathogenic and non-pathogenic Vibrio parahaemolyticus strains were simultaneously detected and quantified using a novel viable multiplex real-time PCR (novel qPCR). We used a new PCR primer and probe, ureR, as a surrogate for detection of the toxin trh gene as the primer was better at identifying variant V. parahaemolyticus trh strains. The specificity of all primers and probes used in this study were validated on three standard strains of V. parahaemolyticus, 42 clinical strains, 12 wild strains, 4 strains of Vibrio spp., and 4 strains of other bacteria. Then, propidium monoazide (PMA) was applied to inhibit DNA of dead cell, and the results of PMA optimized treatments were 15 μM concentration, 5 min incubation periods, 15 min light exposure periods and 30 RPM rotational speed, which resulted in time and cost savings. Pathogenic and non-pathogenic strains were quantified using a two-reaction tube method where the tlh, tdh, and ureR genes were amplified. Additionally, standard curves with a 7-log dynamic range were generated for quantifying viable V. parahaemolyticus and the amplification efficiencies were 108.68, 105.17, and 115.61% for tlh⁺, tdh⁺, and ureR⁺. This novel qPCR accurately monitored V. parahaemolyticus contamination rates in shrimps (Penaeus vannamei) and clams (Ruditapes philippinarum) sampled from retail stores located in a major district in Shanghai. In conclusion, our assay can prioritize the detection and quantification of viable pathogenic V. parahaemolyticus and can prove to be a more effective tool for reducing infection risks from consumption of seafood in Shanghai.

Isolation, identification and phenotypic and molecular characterization of pathogenic Vibrio vulnificus isolated from Litopenaeus vannamei

The morphology and the drug sensitivity of the strain GYX2014-1 isolated from the hepatic pancreatic tissue of moribund Litopenaeus vannamei were evaluated by conventional culture characteristics, physical and chemical characteristics, and molecular biology methods. Detection of extracellulase and hemolysin activity shows that the isolated GYX2014-1 has protease, lipase, gelatinase activity, but none of amylase, or lecithinase activity. The 16S rRNA gene (GenBank accession number: KT781675) was analyzed, and a phylogenetic tree analysis showed that the isolated pathogen was most closely related to V. vulnificus (GenBank accession number: NR 118570)—a match of more than 99%. The phenotypic traits and molecular biology of isolated bacteria, determined their identity as Vibrio vulnificus (V. vulnificus). In addition, artificially infected L. vannamei with Vibrio vulnificus appeared with the same disease symptoms as those of naturally infected shrimp. Drug sensitivity tests showed that V. vulnificus is highly sensitive to fosfomycin, cefradine and sinomin, and was resistant to penicillin, amikacin and kanamycin. This experiment is the first to separate V. vulnificus from L. vannamei, and the findings of this study can be used as a reference for disease control and health management.

A Comprehensive Epidemiological Research for Clinical Vibrio parahaemolyticus in Shanghai

Vibrio parahaemolyticus is one of the most important pathogen for seafood-borne gastroenteritis in Shanghai and the rest of the world. A total of 42 V. parahaemolyticus strains were isolated from 1900 fecal specimens collected from patients in Shanghai hospital presenting from January 2014 to December 2015. All isolates were evaluated for potential virulence factors [tdh, trh, and type three secretion system (T3SS) genes], typed using multilocus sequence typing (MLST) and screened for antimicrobial resistance phenotype and genotype. And for the first time, the relationship between virulence, genetic diversity and antimicrobial resistance of these isolates were identified. The results showed that 37 isolates carried the tdh gene (88.1%) and only seven isolates were positive for the trh gene. The T3SS1 and T3SS2 genes were detected in all strains and only trh-positive isolates are also containing the T3SS2β genes. MLST analysis of the 42 Shanghai isolates identified 20 sequence types (STs) with 16 novel STs and that these clinical V. parahaemolyticus strains showed high degrees of genetic diversity. All isolates expressed high levels of resistance against Ampicillin (100.0%), Streptomycin (100.0%), Cephazolin (92.9%), Kanamycin (92.8%) and Amikacin (90.5%), and eight out of 38 resistance genes (SHV, tet(B), strA, qnrA, gryA, qnrB, sulI, sulII) were detected in at least two isolates. This study confirms that antimicrobial resistance of clinical V. parahaemolyticus isolates is greater than those of environmental isolates. Furthermore, no clear correlation between antimicrobial resistance and virulence or genetic diversity was found in this study. These results add to epidemiological data of clinical V. parahaemolyticus isolates in Shanghai and highlight the need for additional mechanistic studies, especially antimicrobial resistance, to reduce the burden of disease caused by this pathogen in China.