Distribution and Transmission of Colistin Resistance Genes mcr-1 and mcr-3 among Nontyphoidal Salmonella Isolates in China from 2011 to 2020.

Mobile colistin resistance (mcr) genes are present mainly in plasmids and can disseminate clonally or horizontally via either plasmids or insertion sequences in different genomic locations among the Enterobacteriaceae. A nationwide large-scale study on mcr prevalence and transmission in nontyphoidal Salmonella isolates is still lacking. Here, we identified 140 mcr-positive Salmonella isolates out of 7,106 isolates from 29 provinces in China from 2011 to 2020. We aligned short reads to putative plasmids from long-read hybrid assemblies and predicted the plasmid backbones of non-long-read sequencing isolates to elucidate mcr transmission patterns. The mcr-1 and mcr-3 genes are transmitted on similar high-risk clones (sequence type 34 [ST34]) but through plasmids of various replicon types. Furthermore, the ban on colistin use in food animals can lead to a decrease in the mcr-positive Salmonella prevalence among diarrheal patients, related mainly to IncHI2A_IncHI2 plasmids. We provide a framework for plasmid data incorporation into genomic surveillance systems, contributing to a better understanding of mcr spread and transmission. IMPORTANCE Nontyphoidal Salmonella is one of four major causative agents of diarrheal diseases globally, with most cases of salmonellosis being mild. Antimicrobial treatments are required for cases of life-threatening infections, and colistin is one of the last-line antibiotics for the treatment of multidrug-resistant Salmonella infections. However, the efficacy of colistin has been compromised by the emergence of various mcr genes. To elucidate the transmission of mcr genes in Salmonella isolates, our study analyzed 7,106 Salmonella strains from 29 provinces in China from 2011 to 2020. The results showed that mcr genes are transmitted on similar high-risk clones (ST34) but through plasmids of various replicon types. In addition, our data illustrated that the ban on the use of colistin in food animals led to a significant decrease in mcr-positive isolates. Our findings offer an essential step toward a more comprehensive understanding of the spread and transmission of mcr genes.

Estimating the burden of foodborne gastroenteritis due to nontyphoidal Salmonella enterica, Shigella and Vibrio parahaemolyticus in China.

To estimate the incidence of foodborne gastroenteritis caused by nontyphoidal Salmonella enterica, Shigella, and Vibrio parahaemolyticus in China, population surveys and sentinel hospital surveillance were implemented in six provinces from July 2010 to July 2011, and a multiplier calculation model for the burden of disease was constructed. The multiplier for salmonellosis and V. parahaemolyticus gastroenteritis was estimated at 4,137 [95% confidence interval (CI) 2,320-5,663], and for shigellosis at 4,356 (95% CI 2,443-5,963). Annual incidence per 100,000 population was estimated as 245 (95% CI 138-336), 67 (95% CI 38-92), and 806 (95% CI 452-1,103) for foodborne salmonellosis, shigellosis, and V. parahaemolyticus gastroenteritis, respectively, indicating that foodborne infection caused by these three pathogens constitutes an important burden to the Chinese healthcare system. Continuous implementation of active surveillance of foodborne diseases, combined with multiplier models to estimate disease burden, makes it possible for us to better understand food safety status in China.

New Variant of Vibrio parahaemolyticus, Sequence Type 3, Serotype O10:K4, China, 2020.

In 2020, a new serotype of Vibrio parahaemolyticus O10:K4 emerged and caused several outbreaks and sporadic cases in Guangxi, China. Phylogenetic analysis indicated that those strains are new variants of the sequence type 3 pandemic clone. The new serotype may become dominant, warranting enhanced investigations and surveillance.

Effect of Y Chromosome Microdeletions on the Pregnancy Outcome of Assisted Reproduction Technology: a Meta-analysis.

This systematic analysis aimed to summarize the effects of Y chromosome microdeletions (YCMs) on pregnancy outcomes of assisted reproductive technology (ART). This retrospective controlled meta-analysis evaluated the effect of YCMs on pregnancy outcomes of ART. Full-text retrieval was conducted in the PubMed, CBM, Web of Science, CNKI, VIP, and WANFANG databases. The pregnancy outcomes included fertilization rate, good embryo rate, clinical pregnancy rate, early miscarriage rate, miscarriage rate, live birth rate, and baby boy rate. The quality of these studies was evaluated using the Newcastle-Ottawa scale. Statistical software Review Manager 5.3 and STATA 14.0 were used. Twelve high-quality studies were included in the analysis. Compared with that in the normal group, the fertilization rate in the YCMs group decreased significantly (odds ratio [OR] = 0.75, 95% confidence interval [CI] [0.63, 0.88], P = 0.0006). However, there was no significant difference (P > 0.05) between groups in the good embryo rate (OR = 0.88, 95% CI [0.72, 1.07]), clinical pregnancy rate (OR = 0.94, 95% CI [0.78, 1.11]), early miscarriage rate (OR = 1.70, 95% CI [0.93, 3.10]), miscarriage rate (OR = 1.3, 95% CI [0.93, 1.91]), live birth rate (OR = 0.90, 95% CI [0.74, 1.08]), and baby boy rate (OR = 1.15, 95% CI [0.85, 1.56]). YCMs are associated with a reduced fertilization rate of ART, but they do not decrease the good embryo rate, clinical pregnancy rate, early miscarriage rate, miscarriage rate, live birth rate, or baby boy rate.

Circular RNA has_circ_0000527 participates in proliferation, invasion and migration of retinoblastoma cells via miR-646/BCL-2 axis.

Retinoblastoma (RB) is one of the most common primary intraocular malignancies in children. Emerging researches have shown that circular RNAs (circRNAs) play critical roles in a variety of cancers. As a novel circRNA, the function of circ_0000527 in RB remains unknown. In this work, expression level of circ_0000527 and miR-646 in RB tissues and cell lines were detected by quantitative real-time polymerase chain reaction (qRT-PCR). RB cell lines (SO-Rb50 and WERI-Rb-1) were used as cell models in functional experiments. CCK-8 assay, TUNEL assay and transwell assay were employed to detect the biological influence of circ_0000527 and miR-646 on cancer cells in vitro. qRT-PCR, luciferase reporter assay, RIP assay and western blot were used for exploring the interactions among circ_0000527, miR-646 and BCL-2. It was demonstrated that expression level of circ_0000527 in RB samples was significantly up-regulated compared to normal tissues, while miR-646 was markedly down-regulated. Overexpression of circ_0000527 promoted the viability, migration and invasion of RB cells, while miR-646 transfection had the opposite effects. Circ_0000527 sponged miR-646 to regulate the expression of BCL-2. In conclusion, circ_0000527 could promote the development of RB by indirectly modulating BCL-2 via absorbing miR-646. SIGNIFICANCE OF THE STUDY: Expression level of circ_0000527 in RB samples was significantly up-regulated compared to normal tissues, while miR-646 was markedly down-regulated. Overexpression of circ_0000527 promoted the viability, migration and invasion of RB cells, while miR-646 transfection had the opposite effects. Circ_0000527 sponged miR-646 to regulate the expression of BCL-2.

Occurrence and Characterization of Cronobacter spp. in Dehydrated Rice Powder from Chinese Supermarket.

Cronobacter spp. are emerging food-borne pathogens and have been identified as causative agents of meningitis and necrotizing enterocolitis in infants. Dehydrated rice is popular with a wide range of people and it is frequently used as a substitute for infant milk powder to baby older than four months. The occurrence of Cronobacter spp. was investigated in 1,012 samples of dehydrated rice powder collected from 14 manufacturers in China during 2010 to 2012. The isolates were identified using fusA allele sequencing and subtyped using pulsed-field gel electrophoresis. Seventy-six samples (7.5%) contained Cronobacter spp. The prevalence among manufacturers ranged from 0-28.8%. The 76 isolates included 4 species [Cronobacter sakazakii (52 isolates) Cronobacter malonaticus (14 isolates), Cronobacter dublinensis (7 isolates), and Cronobacter muytjensii (3 isolates)]. Twenty-three unique fusA alleles and sixty-six PFGE-patterns were detected. All isolated strains were observed to be sensitive or to show intermediate susceptibility to eight tested antimicrobial agents. The study revealed serious contamination of dehydrated rice powder by Cronobacter spp., with prevalence varying among manufacturers in China. Identified Cronobacter species, fusA alleles, and subtypes were diverse.

Temporal and Spatial Variation in the Abundance of Total and Pathogenic Vibrio parahaemolyticus in Shellfish in China.

We investigated the abundance of total and pathogenic Vibrio parahaemolyticus in shellfish sampled from four provinces in China during May 2013 and March 2014 using the most probable number-polymerase chain reaction (MPN-PCR) method. Total V. parahaemolyticus was detected in 67.7% of 496 samples. A total of 38.1% and 10.1% of samples exceeded 1,000 MPN g(-1) and 10,000 MPN g(-1), respectively. V. parahaemolyticus densities followed a seasonal and geographical trend, with Guangxi and Sichuan shellfish possessing total V. parahaemolyticus levels that were 100-fold higher than those of the Liaoning and Shandong regions. Moreover, the levels of V. parahaemolyticus were at least 10-fold higher in the summer and autumn than in the cooler seasons. Pathogenic V. parahaemolyticus levels were generally lower than total V. parahaemolyticus levels by several log units and tended to be high in samples contaminated with high total V. parahaemolyticus levels. The aqua farms had a lower prevalence but higher abundance of total V. parahaemolyticus compared to retail markets. The catering markets showed the lowest levels of total V. parahaemolyticus, but 20.0% of samples exceeded 1,000 MPN g(-1). The levels of both total and pathogenic V. parahaemolyticus in oysters were higher than in clams. The log-transformed abundance of V. parahaemolyticus was significantly correlated with both water temperature and air temperature but not water salinity. These results provide baseline contamination data of V. parahaemolyticus in shellfish in China, which can be applied to local risk assessments to prioritize risk control to key sectors and evaluate the effectiveness of future control measures.

High prevalence and genetic diversity of noroviruses among children with sporadic acute gastroenteritis in Nanning City, China, 2010-2011.

A molecular epidemiological study of Norovirus (NoV) infections in children aged <5 years was conducted in the outpatient department of a hospital between January 2010 and December 2011 in Nanning City, Guangxi Zhuang Autonomous Region of China. Fecal samples were collected from 354 pediatric patients with acute gastroenteritis, and were screened for the presence of NoV with one-step real-time reverse-transcription polymerase chain reaction (RT-PCR). NoV genogroup II (GII) was detected in 28.5% (101/342) of samples, but no NoV GI was found. Eighty-four of the NoV GII strains were successfully sequenced, and they were clustered into seven genotypes: GII.4 (77.4%), GII.2 (8.3%), GII.14 (4.8%), GII.7 (3.6%), GII.3 (2.4%), GII.6 (2.4%), and GII.12 (1.2%). The predominant GII.4 variant in circulation was variant 2006b (92.3%). Importantly, the emergence of variant GII.4 2010 was detected. NoV was detected throughout the year, but mainly during the cold months. The highest prevalence of NoV was detected in young children aged <2 years. The NoV detection rates did not differ significantly in males and females. This is the first report to demonstrate the high prevalence and genetic diversity of NoVs in children with sporadic acute gastroenteritis in Nanning. Our study findings indicate the need for continual surveillance to monitor epidemiological changes and potential new variants of these viruses.

[Analysis of molecular features of clinical Vibrio parahaemolyticus strains in China].

OBJECTIVE: To explore the phenetic and genetic features of clinical Vibrio parahaemolyticus strains from 2007-2009 in China. METHODS: A total of 135 clinical Vibrio parahaemolyticus strains, isolated from Zhejiang, Jiangsu, Sichuan, Guangxi, Liaoning Provinces during 2007 to 2009, were selected for the research. The occurrence of virulence genes thermostable direct hemolysin (tdh) and TDH-related hemolysin (trh), species-specific genes thermolabile hemolysin (tlh), toxR, VPM and gyrB, the pandemic clone gene markers(GS-PCR, PGS-PCR, orf8 and HU-α) in 135 Vibrio parahaemolyticus strains was detected by PCR. The antimicrobial susceptibilities to eight antimicrobial agents of the experimental strains were determined by the broth microdilution method. All strains were serotyped and underwent the cluster analysis with pulsed-field gel electrophoreses. RESULTS: The results of PCR methods claim that all experiment strains carry species-specific genes such as tlh, toxR, gyrB, VPM. Among clinical strains, 85.9% (116/135) carry tdh and/or trh. 85.2% (115/135) were positive for tdh, and 3.0% (4/135) were positive for trh; while 3 strains carried both.66.7% (90/135) , 80.7% (109/135) , 65.2% (88/135) , 66.7% (90/135) clinical strains carried the genes of GS-PCR, PGS-PCR, orf8, HU-α, respectively. The results of antibiotics susceptibility test showed that 8.1% (11/135) strains were resistant to at least one agent, including 9 strains were resistant to ampicillin, 2 strains were resistant to trimethoprim and sulphamethoxazole, and 1 strain were resistant to tetracycline. All clinical strains were sensitive to cefotaxime, ceftazidime, gentamicin, ciprofloxacin and chloromycetin.Serological analysis of the O and K antigens claimed that a total of 29 serotypes were identified for clinical strains, predominantly O3, O4 and O1 groups, accounting for 89.6% (121/135). O3: K6 was dominant serotype, accounting for 56.3% (76/135). The pandemic flora in China included O3: K6, O4: K68, O1: K36, O1: K25, O1: K5 and O3: K29 serotypes.Genomic DNAs of 135 clinical strains were digested with SfiI and NotI, the molecular size of PFGE restriction fragments used for analysis mainly ranged from 30-700 kb.When subjected to UPGMA clustering, 6 and 9 clusters were grouped by SfiI and NotI, and the minimal similarity was 52.6% and 58.7%, and pandemic flora were located in C groups and D group, respectively. CONCLUSION: Most of Vibrio parahaemolyticus strains isolated from clinical sources in China were pathogenic. The pandemic clone, especially O3: K6 was prevalent. The GS-PCR and HU-α genes were reliable markers to identify the pandemic flora. The serotype by PFGE was reliable to distinguish the pandemic flora and the sporadic strains.

Foodborne pathogens in retail oysters in south China.

OBJECTIVE: To investigate the occurrence of important foodborne pathogens in shellstock Pacific oysters in the food markets in South China. METHODS: From July 2007 to June 2008, retail oysters were collected in different seasons from South China and analyzed for the prevalence and levels of Listeria monocytogenes, Vibrio vulnificus and Vibrio parahaemolyticus. RESULTS: None of L. monocytogenes could be detected in any of the 202 oyster samples tested, while E vulnificus and V. parahaemolyticus could be detected in 67 (54.9%) and 109 (89.3%) of the 122 oyster samples analyzed, respectively, with an MPN (most probable number) value greater than or equal to 3. V. vulnificus and V. parahaemolyticus with a more than 102 MPN/g were found in 36 (29.5%) and 59 (48.4%) of the 122 oyster samples, respectively. The tdh and trh genes were detected in 4 (0.3%) and 8 (0.6%) of the 1 349 V parahaemolyticus isolates, respectively. Of the 122 samples, 4 (3.3%) was positive for either tdh or trh. The levels of V. vulnificus and total V. parahaemolyticus in oysters in South China varied in different seasons. CONCLUSION: V. vulnificus and pathogenic V. parahaemolyticus are frequently found in oysters in south China, which may pose a potential threat to public health. Data presented here will be useful for the microbiological risk assessment in oysters in China.