A systematic review and meta-analysis indicates a high risk of human noroviruses contamination in vegetable worldwide, with GI being the predominant genogroup.

Human noroviruses (HuNoVs) are the most predominant viral agents of acute gastroenteritis. Vegetables are important vehicles of HuNoVs transmission. This study aimed to assess the HuNoVs prevalence in vegetables. We searched the Web of Science, Excerpta Medica Database, PubMed, and Cochrane databases until June 1, 2023. A total of 27 studies were included for the meta-analysis. Statistical analysis was conducted using Stata 14.0 software. This analysis showed that the pooled HuNoVs prevalence in vegetables was 7 % (95 % confidence interval (CI): 3-13) worldwide. The continent with largest number of studies was Europe, and the highest number of samples was lettuce. As revealed by the results of the subgroup meta-analysis, the prevalence of GI genogroup was the highest (3 %, 95 % CI: 1-7). A higher prevalence was seen in vegetables from farms (18 %, 95 % CI: 5-37), while only 4 % (95 % CI: 1-8) in retail. The HuNoVs prevalence of ready-to-eat vegetables and non-ready-to-eat vegetables was 2 % (95 % CI: 0-8) and 9 % (95 % CI: 3-16), respectively. The prevalence by quantitative real time RT-PCR was 8 % (95 % CI: 3-15) compared to 3 % (95 % CI: 0-13) by conventional RT-PCR. Furthermore, the HuNoVs prevalence in vegetables was 6 % (95 % CI: 1-14) in ISO pretreatment method and 8 % (95 % CI: 1-19) in non-ISO method, respectively. This study is helpful in comprehensively understanding the prevalence of HuNoVs contamination in vegetables worldwide.

Prevalence and characterization of Staphylococcus aureus and Staphylococcus argenteus isolated from rice and flour products in Guangdong, China.

Staphylococcus aureus and Staphylococcus argenteus have been implicated in food poisoning outbreaks, and have been found in various types of food products according to our previous study. Rice and flour products are popular and widely consumed around the world. However, limited data are available on the microbial safety of S. aureus in rice and flour products, and S. argenteus has never been reported. Thus, this study aimed to investigate the contamination of S. aureus and S. argenteus in 250 fresh rice and flour product samples from five cities in Guangdong, China. According to qualitative and quantitative analyses, 68 (27.2 %) and 11 (4.4 %) samples were positive for S. aureus and S. argenteus, including 9 samples that exceeded 100 MPN/g. For antibiotics susceptibility tests in 16 antibiotics, the S. aureus isolates exhibited higher rates of resistance and multidrug resistance than S. argenteus. The S. aureus and S. argenteus isolates were mainly resistant to penicillin (70.21 %; 79.17 %), tetracycline (20.21 %; 58.33 %) and azithromycin (19.68 %, 8.33 %). However, the other antibiotic resistance rates were <10 %. Furthermore, the genetic background of the isolates was analyzed by whole-genome sequencing (WGS). As a result, the S. aureus isolates were divided into 18 known sequence types (STs) and 4 novel STs (ST7675, ST7679, ST7680 and ST7682), which mainly belonged to ST188 (20.6 %) and ST6 (14.7 %). The S. argenteus isolates mainly belonged to ST2250 (90.9 %), with a novel type (ST7683). In total, 36 and 16 antibiotic resistance genes (ARGs) were found in S. aureus and S. argenteus isolates, respectively. In addition, 91 virulence genes (VFs) were detected in S. aureus isolates as well as 90 % of core VFs were similar to S. argenteus. More than 20 % of the S. aureus isolates carried the classic enterotoxin gene (sea-sec), but chp, cna and map were free in all S. argenteus isolates. Importantly, 33.8 % of S. aureus isolates belonged to the immune evasion cluster (IEC) type B, whereas most of S. argenteus isolates (90.9 %) belong to IEC type E. According to the phylogenetic analysis, the S. aureus and S. argenteus isolates in fresh rice and flour products may indicate loss or acquisition of ARGs and VFs to survive and adapt to the environment. Our study confirmed the presence of S. argenteus in rice and flour products at first and focused on the multi-dimensional systematic comparative analysis of S. aureus and S. argenteus to reveal their ubiquity and similarities or differences, and provide more accurate and effective basic information for follow-up monitoring and tracking.

Occurrence, Antibiotic Susceptibility, Biofilm Formation and Molecular Characterization of Staphylococcus aureus Isolated from Raw Shrimp in China.

The aim of this study was to determine the prevalence and characterization of Staphylococcus aureus isolated from 145 shrimp samples from 39 cities in China. The results show that 41 samples (28%) from 24 cities were positive, and most of the positive samples (39/41, 95.1%) were less than 110 MPN/g. Antimicrobial susceptibility testing showed that only seven isolates were susceptible to all 24 antibiotics, whereas 65.1% were multidrug-resistant. Antibiotic resistance genes that confer resistance to ß-lactams, aminoglycosides, tetracycline, macrolides, lincosamides and streptogramin B (MLSB), trimethoprim, fosfomycin and streptothricin antibiotics were detected. All S. aureus isolates had the ability to produce biofilm and harbored most of the biofilm-related genes. Genes encoding one or more of the important virulence factors staphylococcal enterotoxins (sea, seb and sec), toxic shock syndrome toxin 1 (tsst-1) and Panton-Valentine leukocidin (PVL) were detected in 47.6% (30/63) of the S. aureus isolates. Molecular typing showed that ST15-t085 (27.0%, 17/63), ST1-t127 (14.3%, 9/63) and ST188-t189 (11.1%, 7/63) were the dominant genetic types. The finding of this study provides the first comprehensive surveillance on the incidence of S. aureus in raw shrimp in China. Some retained genotypes found in this food have been linked to human infections around the world.

The emergence of novel macrolide resistance island in Macrococcus caseolyticus and Staphylococcus aureus of food origin.

Food-derived Staphylococcaceae species with severe antimicrobial resistance, especially Staphylococcus aureus, is a major threat to public health. Macrococcus caseolyticus (M. caseolyticus) is a member of the Staphylococcaceae family which plays a vital role in fermented products and disease causation in animals. In our previous study, several Staphylococcus aureus antibiotic-resistant island msr (SaRImsr) were found in multidrug-resistant S. aureus. In this study, novel SaRImsr, SaRImsr-III emerged from S. aureus. Another novel SaRImsr-like further emerged in M. caseolyticus from food. These isolates' prevalence and genetic environment were investigated and characterized to understand the distribution and transmission of these novel SaRImsr strains. All SaRImsr-positive S. aureus isolates exhibited a multidrug resistance (MDR) phenotype, within which a series of antimicrobial resistance genes (ARGs) and virulence factor genes (VFs) were identified. In addition, three SaRImsr types, SaRImsr-I (15.1 kb), SaRImsr-II (16-17 kb), and SaRImsr-III (18 kb) carrying mef(D)-msr(F), were identified in these isolates' chromosomes. SaRImsr-(I-III) contains a site-specific integrase gene int and operon mef(D)-msr(F). SaRImsr-III has an additional orf3-orf4-IS30 arrangement downstream of mef(D) and msr(F). Moreover, the SaRImsr-like and macrolide-resistant transposon Tn6776 forming a novel mosaic structure coexisted in one M. caseolyticus isolate. Within this mosaic structure, the macrolide-resistant genes mef(D)-msr(F) were absent in SaRImsr-like, whereas an operon, mef(F)-msr(G), was identified in Tn6776. The SaRImsr-(I-III) and SaRImsr-like structure were inserted into the rpsI gene encoding the 30S ribosomal protein S9 in the chromosome. Excision and cyclisation of SaRImsr-III, SaRImsr-like, operon mef(D)-msr(F), and orf3-orf4-IS30 arrangements were confirmed using two-step PCR. This study is the first to report MDR S. aureus harbouring novel SaRImsr-III and M. caseolyticus containing novel mosaic structures isolated from retail foods. Similar SaRImsr-type resistant islands' occurrence and propagation in Staphylococcaceae species require continuous monitoring and investigation.

Emergence of extensive multidrug-resistant Staphylococcus aureus carrying novel Sa-MRRlsa(E) in retail food.

OBJECTIVES: The aim of this study was to investigate the prevalence and genetic environment of the multidrug resistance gene lsa(E) in food-related Staphyloccocus aureus in China. METHODS: 1463 S. aureus from retail food products in 39 Chinese cities were investigated to determine the prevalence of lsa(E). Furthermore, antimicrobial susceptibility testing, whole-genome sequencing (WGS), and complete genetic analysis were performed in lsa(E)-positive isolates. RESULTS: Thirty-five isolates (2.4%) were positive for the lsa(E) gene, which had an extensive multidrug-resistance phenotype. ST9-t899 and ST1-t4792 were the common sequence types in positive strains. The lsa(E) genes were located in two different types of novel multidrug resistance region (MRRlsa[E]) on the chromosome. The Sa-MRRlsa(E)-I were inserted into the lctP gene. The Sa-MRRlsa(E)-II were inserted into the crtP gene, and were comprised of seven antibiotic resistance genes (ARGs) interspersed with varieties of insertion sequences (ISs), transposons, and DNA invertase genes, showing a novel arrangement harboring lsa(E). Part of transposon Tn1546 was inserted downstream of lnu(B) in the novel Sa-MRRlsa(E)-II. Both types of Sa-MRRlsa(E) could be excised from the chromosome, indicating that Sa-MRRlsa(E) may be transferable. CONCLUSION: Our study is the first systematical investigation of lsa(E)-positive S. aureus in retail foods in China. It indicated that the origin of most food-related lsa(E)-positive S. aureus in China might be associated with livestock or poultry breeding farms, and these strains may be transmitted between animals and food. S. aureus carrying novel Sa-MRRlsa(E), especially, serve as reservoirs of antibiotic resistance traits, and warrant further attention.

Presence and characterization of methicillin-resistant Staphylococcus aureus co-carrying the multidrug resistance genes cfr and lsa(E) in retail food in China.

Staphylococcus aureus is an important food-related pathogen associated with bacterial poisoning that is difficult to treat due to its multidrug resistance. The cfr and lsa(E) genes both cause multiple drug resistance and have been identified in numerous Staphylococcus species, respectively. In this study, we found that a methicillin-resistant S. aureus (MRSA) strain, 2868B2, which was isolated from a sample of frozen dumplings in Hangzhou in 2015, co-carried these two different multidrug resistance genes. Further analysis showed that this strain was resistant to more than 18 antibiotics and expressed high-level resistance to florfenicol, chloramphenicol, clindamycin, tiamulin, erythromycin, ampicillin, cefepime, ceftazidime, kanamycin, streptomycin, tetracycline, trimethoprim-sulfamethoxazole and linezolid (MIC = 8 µg/mL). Whole genome sequencing was performed to characterize the genetic environment of these resistance genes and other genomic features. The cfr gene was located on the single plasmid p2868B2 (39,159 bp), which demonstrated considerable similarity to many plasmids previously identified in humans and animals. p2868B2 contained the insertion sequence (IS) element IS21-558, which allowed the insertion of cfr into Tn558 and played an important role in the mobility of cfr. Additionally, a novel multidrug resistance region (36.9 kb) harbouring lsa(E) along with nine additional antibiotic resistance genes (ARGs) (aadD, aadE, aacA-aphD, spc, lnu(B), lsa(E), tetL, ermC and blaZ) was identified. The multidrug resistance region harboured four copies of IS257 that were active and can mediate the formation of four circular structures containing ARGs and ISs. In addition, genes encoding various virulence factors and affecting multiple cell adhesion properties were identified in the genome of MRSA 2868B2. This study confirmed that the cfr and lsa(E) genes coexist in one MRSA strain and the presence of plasmid and IS257 in the multi-ARG cluster can promote both ARG transfer and dissemination. Furthermore, the presence of so many ARGs and virulence genes in food-related pathogens may seriously compromise the effectiveness of clinical therapy and threaten public health, its occurrence should pay public attention and the traceability of these genes in food-related samples needs further surveillance.

Molecular Characterization of Rifampicin-Resistant Staphylococcus aureus Isolates from Retail Foods in China.

This study investigated the molecular characteristics of rifampin-resistant (RIF-R) Staphylococcus aureus isolates recovered from 4300 retail food samples covering most provincial capitals in China, from 2011 to 2016. Of the 1463 S. aureus enrolled, 149 isolates (142 MSSA and 7 MRSA) were identified as rifampicin-resistant, including 20 high-level (MICs ≥ 8 µg/mL) and 129 low-level (MICs between 2 and 4 µg/mL) rifampicin-resistant strains. Most of the RIF-R S. aureus isolates were resistant to more than three antibiotics. The mutations in the rifampicin resistance-determining region of the rpoB gene were studied in all RIF-R strains. All of the strains presented the mutational change 481 His/Asn and five isolates presented an additional mutation, including 477 Asp/Tyr, 527 Ile/Met, and 466 Leu/Ser, respectively. Thirteen STs and twenty-one spa types were represented, in which five MRSA showed non-type SCCmec and the remaining MRSA belonged to SCCmec type IV-where, ST1-t127 was the predominant type from all of the isolates, while ST398-t034 was the predominant type for the MRSA isolates. In this study, we found that the food-related RIF-R S. aureus may have a unique genetic background selection. However, the scenario regarding the presence of RIF-R S. aureus, especially MRSA, in retail food in China is not favorable and warrants public attention.

Staphylococcus argenteus isolated from retail foods in China: Incidence, antibiotic resistance, biofilm formation and toxin gene profile.

Staphylococcus argenteus is a novel species of coagulase-positive staphylococci which was separated from Staphylococcus aureus in 2014. It can threaten human health like S. aureus but can not identify with conventional biochemical or other phenotypic testing. From 2011 to 2016, 1581 S. aureus strains were isolated from 4300 samples from retail foods covering most provincial capitals in China. According to multilocus sequence typing (MLST) and PCR confirmation, 7.2% of isolates (114/1581) were confirmed as S. argenteus. The pathogen was distributed in 22 of 39 sampled cities and all food types. Interestingly, most S. argenteus positive samples were collected from coastal cities in South China. MLST detected 8 different sequence types (STs), including five new STs. CC2250 was the predominant lineage of S. argenteus, followed by CC1223. To further characterize the isolates, their antibiotic resistance, virulence genes, biofilm formation and biofilm-related genes were examined. The pvl gene was not detected in S. argenteus, and only 1 isolate (0.9%) was positive for the tsst-1 gene. For 18 enterotoxin genes, 16.7% (19/114) of isolates harboured more than three genes, whereas 70.2% (80/114) of isolates had none of the investigated genes. Penicillin and ampicillin were the major antibiotics to which the S. argenteus isolates were resistant, followed by tetracycline, kanamycin and fusidic acid. A total of 94.7% of isolates had the ability to produce biofilms and all isolates harboured icaA, fnbA, and fib genes. Other biofilm-related genes, such as eno, clfB, fnbB, and icaC, were also found in 99.1%, 92.1%, 88.6%, and 74.6% of isolates, respectively. This study is the first systematic investigation of the prevalence of S. argenteus in retail foods in China and shows their ubiquity in food. We also provide comprehensive surveillance of the incidence of S. argenteus in retail foods and information to enable more accurate and effective treatment of infections of this new species.

Presence and Characterization of a Novel cfr-Carrying Tn558 Transposon Derivative in Staphylococcus delphini Isolated From Retail Food.

Antimicrobial resistance has become a major public health threat. Food-related Staphylococcus species have received much attention due to their multidrug resistance. The cfr gene associated with multidrug resistance has been consistently detected in food-derived Staphylococcus species. In this retrospective study, we examined the prevalence of cfr-positive Staphylococcus strains isolated from poultry meat in different geographical areas of China from 2011 to 2016. Two cfr-positive Staphylococcus delphini strains were identified from poultry meat in China. Comparative and whole-genome analyses were performed to characterize the genetic features and overall antimicrobial resistance genes in the two S. delphini isolates 245-1 and 2794-1. Whole-genome sequencing showed that they both harbored a novel 20,258-bp cfr-carrying Tn558 transposon derivative on their chromosomes. The Tn558 derivative harbors multiple antimicrobial resistance genes, including the transferable multiresistance gene cfr, chloramphenicol resistance gene fexA, aminoglycoside resistance genes aacA-aphD and aadD, and bleomycin resistance gene ble. Surprisingly, within the Tn558 derivative, an active unconventional circularizable structure containing various resistance genes and a copy of a direct repeat sequence was identified by two-step PCR. Furthermore, core genome phylogenetic analysis revealed that the cfr-positive S. delphini strains were most closely related to S. delphini 14S03313-1 isolated from Japan in 2017 and 14S03319-1 isolated from Switzerland in 2017. This study is the first report of S. delphini harboring a novel cfr-carrying Tn558 derivative isolated from retail food. This finding raises further concerns regarding the potential threat to food safety and public health safety. The occurrence and dissemination of similar cfr-carrying transposons from diverse Staphylococcus species need further surveillance.

Phenotypic and genotypic characterization of PVL-positive Staphylococcus aureus isolated from retail foods in China.

Staphylococcus aureus encodes numerous toxins that are known or strongly suspected to cause specific diseases or symptoms. Panton-Valentine leukocidin (PVL) is one of these important toxins that is associated with high mortality rates. In our previous study, 1581 S. aureus strains were isolated from 4300 samples of retail foods obtained from most of the provincial capitals in China from 2011 to 2016. This study aimed to investigate the prevalence of PVL-positive S. aureus isolates from retail foods in China and characterize these isolates by antibiotic resistance testing, spa typing, multilocus sequence typing (MLST) and enterotoxin gene analyses. In total, seventy-two isolates (72/1581, 4.6%) possessed pvl genes, including 24.1% MRSA isolates (26/108) and 3.1% MSSA isolates (46/1473), covering different types of food. The strains were divided into seventeen sequence types (STs) and twenty-seven spa types, and 43.1% (31/72) of the PVL-positive S. aureus isolates belonged to CC59-t437. These isolates contained at least one of the following enterotoxin genes: sei (97.2%), sem (86.1%), seq (80.6%), seg (68.1%), sek (68.1%), seb (62.5%), sel (52.8%), sej (50.0%), seh (48.6%), sep (45.8%), sea (38.9%), ser (37.5%), sen (27.8%), sec (16.7%), see (16.7%), sed (6.9%), seo (6.9%) and seu (6.7%). A total of 87.5% of the S. aureus isolates (63/72) harboured the classic SE genes (sea, seb, sec, sed, and see), whereas all the S. aureus isolates harboured the genes of the egc cluster (seg, sei, sem, sen, seo, and seu). In antimicrobial susceptibility tests, 98.6% of the isolates (71/72) exhibited resistance to at least one antibiotic, including 47 multi-drug-resistant isolates. Resistance to penicillin (94.4%), erythromycin (83.4%), clindamycin (63.9%), kanamycin (61.1%), telithromycin (58.3%), streptomycin (51.4%), tetracycline (47.2%), chloramphenicol (27.8%), fusidic acid (27.8%) and other antibiotics (<20%) was observed. All the PVL-positive MRSA isolates belonged to CC59-t437, which is the predominant type of community-associated (CA)-MRSA in China. The presence of these isolates in food represents a potential health risk for consumers and warrants further attention.

Prevalence and Characterization of Staphylococcus aureus Isolated From Pasteurized Milk in China.

Staphylococcus aureus is one of the most important food-borne pathogens globally. It produces various toxins and invasive enzymes and can be found in numerous food products. Milk is an important source of staphylococcal food poisoning. After pasteurization, this microorganism or its enterotoxins might still remain in pasteurized milk. Therefore, this study was to investigate the contamination of S. aureus in 258 pasteurized milk from 39 cities of China. The prevalence and levels of S. aureus in these samples as well as antibiotic susceptibility profiles, virulence genes, biofilm formation, and biofilm related genes, spa typing and MLST were used to determine the characterization among the isolates. It was found 3.9% of samples were detected S. aureus in 8 of 39 cities in China. The contaminated level were not very excessive which showed the MPN values of the most positive samples (9/10) were less than 1 MPN/g. All pasteurized milk-related S. aureus isolates have ability to produce biofilm and harbored icaA, icaD, eno, clfA, clfB, fnbA, fnbB, fib genes, other biofilm related genes icaC were showed in 91.7% of isolates and cna gene were showed in 50%, except bap gene which were free in all isolates. The antibiotic susceptibility test showed that all isolates were resistant or intermediate-resistant to different concentrations of the antibiotics. Furthermore, 75.0% of the isolates were resistant to three or more antibiotic classes, which indicated multidrug resistance. The isolates had virulence potential, which showed 66.7% (8/12) of the isolates carried one or more virulence-associated genes. Molecular typing by MLST and spa typing enabled classification of these isolates into a total of 11 sequence types (STs) and spa types, which indicated high genetic diversity. Most of these types were related to various clinical S. aureus infections. Thus, the findings of this study reflect the potential risk of S. aureus infection in China. Our study also provides comprehensive analysis of the prevalence of S. aureus in pasteurized milk and helps ensure more accurate treatment of human infection with effective antibiotics.

Prevalence and Characterization of Food-Related Methicillin-Resistant Staphylococcus aureus (MRSA) in China.

Methicillin-resistant Staphylococcus aureus (MRSA) is an emerging pathogen that is difficult to treat due to the multiresistance of the bacteria upon infection. From 2011 to 2016, 1581 S. aureus strains were isolated from 4300 samples from retail foods covering most provincial capitals in China. To determine the prevalence of food-related MRSA and its genetic background in China, antibiotic resistance, staphylococcal toxin genes, staphylococcal cassette chromosome mec (SCCmec) typing, spa-typing and MLST were carried out in this study. In total, 108 (7.4%) isolates were confirmed for MRSA by phenotyping (cefoxitin) and genotyping (mecA/mecC gene). A total of 52.8% (57/108) of the MRSA isolates belonged to clonal complex 59 (CC59) (ST59, ST338, and ST3355), which was the predominant clone in this study. These CC59 isolates carried SCCmec elements of type IV, V, or III and exhibited spa type t437, t441, t543, t163, t1785, or t3485, and half of them carried major virulence genes, such as the Panton-Valentine leucocidin (PVL) gene. The secondary clones belonged to ST9 (15.7%, 17/108) with a type of t899-SCCmec III and showed a broader range of antimicrobial resistance. The remaining MRSA isolates (31.5%, 34/108) were distributed in 12 different STs and 18 different spa types. All isolates harbored at least one of the enterotoxin genes, whereas only 4 isolates (3.70%) were positive for the toxic shock syndrome toxin tsst alleles. For antibiotic susceptibility testing, all isolates were resistant to more than three antibiotics, and 79.6% of the isolates were resistant to more than 10 antibiotics. Amoxycillin/clavulanic acid, ampicillin, cefoxitin, penicillin, ceftazidime, kanamycin, streptomycin, clindamycin, and telithromycin was the most common antibiotic resistance profile (55.6%, 60/108) in the study. In summary, the results of this study implied that the major food-related MRSA isolate in China was closer to community-associated MRSA, and some of the remaining isolates (ST9-t899-SCCmec III) were supposed to livestock-associated MRSA. In addition, most MRSA isolates showed resistance to multiple drugs and harbored staphylococcal toxin genes. Thus, the pathogenic potential of these isolates cannot be ignored. In addition, further studies are needed to elucidate the transmission routes of MRSA in relation to retail foods and to determine how to prevent the spread of MRSA.