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Abstract Cronobacter had been detected in the powdered infant formula (PIF) in China more frequently in comparison with other developed countries. However, the persistence, dissemination and transmission routes of Cronobacter are not clearly known. As part of the national surveillance program, 6111 samples were collected and tested for the presence of Cronobacter from eight powdered infant formula production facilities in China between 2013 and 2014. The isolates were further characterized by pulsed-field gel electrophoresis (PFGE), as well as multilocus sequence typing (MLST). From the 6111 samples, Cronobacter was only isolated in 35 samples, 21 samples from dry-mix processes and 14 samples from combined processes. The prevalence in final products was 2.27% (4/176) and 0.00% (0/89) in samples from dry-mix processes and samples from combined processes, respectively. The 35 Cronobacter isolates were differentiated into 22 pulsotypes, and eight groups of isolates demonstrated the same clonality, suggesting a potential epidemiological link. MLST analysis on 35 isolates revealed that C. sakazakii was the most prevalent species (71.43%), followed by C. malonaticus (25.71%). The most common typeable isolates belonged to sequence type (ST) 7 (18.18%) and ST1 (15.15%). The results of this study showed the Cronobacter contamination along the PIF production process. PIF manufactured with dry-mix processes was frequently contaminated with Cronobacter potentially due to noncompliant materials and/or lack of a sterilization step. Highlights • 0.52% (35/6111) of the samples was contaminated with Cronobacter. • C. sakazakii was the most prevalent species identified (71.43%). • The most common isolates belonged to ST7 (18.18%) and ST1 (15.15%). • PFGE was a more effective method to identify sources and transmission routes. [ABSTRACT FROM AUTHOR]

Abstract The purpose of this survey was to investigate the distribution of major pathogenic Vibrio spp. (Vibrio parahaemolyticus , Vibrio alginolyticus , Vibrio vulnificus and Vibiro cholerae) in Chinese freshwater fish farms. In total, 4064 samples of freshwater fish, water and sediment were collected from 12 provinces covering every quarter in 2016. The occurrence of Vibrios was as follows: V. cholerae (10.33%), V. parahaemolyticus (3.89%), V. alginolyticu s (1.24%) and V. vulnificus (0.76%). Among 158 confirmed V. parahaemolyticus isolates, 44 isolates (27.85%) had virulence genes (trh/tdh). Among 420 confirmed V. cholerae isolates, 4 were the O1 stains and 4 were the O139 strains. Out of 112 freshwater farms, 58.93% had Vibrios- positive samples. The rates of Vibrios -positive samples from May to October (12.45%–35.20%) were higher than those in other months (0.00%–8.07%). Compared the environment factors of Vibrios positive and negative water samples, there was a significantly difference in temperature (P ＜0.01), while no significant difference in salinity and pH value (P ＞0.05). In summary, the study presents comprehensive contamination data on the occurrence of four major pathogenic Vibrios in freshwater aquaculture of China for the first time, and the results indicate that Vibrio s are widely distributed in aquaculture environment and a further risk assessment is needed to conduct. Highlights • Acquire the occurrence of four Vibrios in Chinese freshwater fish farms. • Out of 112 freshwater farms, 58.93% had Vibrios -positive samples. • The rates of Vibrios -positive samples from May to October were higher. • Temperature had a positive correlation with occurrence rate of Vibrios. • Vibrio s are widely distributed in aquaculture environment. [ABSTRACT FROM AUTHOR]

Salmonellosis is a challenge to public health globally, and many infections have been principally linked to the consumption of contaminated eggs. The objective of this study is to estimate the prevalence of Salmonella in commercial eggs and susceptibilities of isolates to a panel of 14 antimicrobial agents which were determined according to Clinical and Laboratory Standards Institute (CSLI) procedures. A total of 33,288 eggs (5548 pooled samples of six eggs) were collected across China in 2016 and the prevalence of Salmonella was 0.5% (27/5548). The most predominant serotype was S. enteritidis. No significant differences were observed on the basis of the egg component tested, shell condition, packaging type, sampling site or sampling season. However, there were significant differences among provincial regions. About 64.3% (n = 18) isolates were resistant to nalidixic acid, followed by ampicillin (39.3%) and ampicillin/sulbactam (39.3%). All isolates were susceptible to ceftazidime, cefalothin, ciprofloxacin, cefepime, cefotaxime, imipenem and meropenem. Three Salmonella isolates exhibited resistance to multiple antibiotics. This study provides valuable baseline data of the occurrence of Salmonella in eggs, which will be used for risk assessments of possible human foodborne infections associated with the consumption of contaminated eggs. • 0.5% (27/5548) of pooled egg samples were contaminated with Salmonella. • The most predominant serotype was S. Enteritidis , followed by S. Typhimurium. • Most isolates were resistant to nalidixic acid. • No isolates were resistant to ceftazidime, cefalothin, ciprofloxacin, cefepime, cefotaxime, imipenem or meropenem. [ABSTRACT FROM AUTHOR]

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.