Therapeutic applications of gut microbes in cardiometabolic diseases: current state and perspectives.

Cardiometabolic disease (CMD) encompasses a range of diseases such as hypertension, atherosclerosis, heart failure, obesity, and type 2 diabetes. Recent findings about CMD's interaction with gut microbiota have broadened our understanding of how diet and nutrition drive microbes to influence CMD. However, the translation of basic research into the clinic has not been smooth, and dietary nutrition and probiotic supplementation have yet to show significant evidence of the therapeutic benefits of CMD. In addition, the published reviews do not suggest the core microbiota or metabolite classes that influence CMD, and systematically elucidate the causal relationship between host disease phenotypes-microbiome. The aim of this review is to highlight the complex interaction of the gut microbiota and their metabolites with CMD progression and to further centralize and conceptualize the mechanisms of action between microbial and host disease phenotypes. We also discuss the potential of targeting modulations of gut microbes and metabolites as new targets for prevention and treatment of CMD, including the use of emerging technologies such as fecal microbiota transplantation and nanomedicine. KEY POINTS: • To highlight the complex interaction of the gut microbiota and their metabolites with CMD progression and to further centralize and conceptualize the mechanisms of action between microbial and host disease phenotypes. • We also discuss the potential of targeting modulations of gut microbes and metabolites as new targets for prevention and treatment of CMD, including the use of emerging technologies such as FMT and nanomedicine. • Our study provides insight into identification-specific microbiomes and metabolites involved in CMD, and microbial-host changes and physiological factors as disease phenotypes develop, which will help to map the microbiome individually and capture pathogenic mechanisms as a whole.

Research progress on carotenoid production by Rhodosporidium toruloides.

Carotenoids are natural lipophilic pigments, which have been proven to provide significant health benefits to humans, relying on their capacity to efficiently scavenge singlet oxygen and peroxyl radicals as antioxidants. Strains belonging to the genus Rhodosporidium represent a heterogeneous group known for a number of phenotypic traits including accumulation of carotenoids and lipids and tolerance to heavy metals and oxidative stress. As a representative of these yeasts, Rhodosporidium toruloides naturally produces carotenoids with high antioxidant activity and grows on a wide variety of carbon sources. As a result, R. toruloides is a promising host for the efficient production of more value-added lipophilic compound carotenoids, e.g., torulene and torularhodin. This review provides a comprehensive summary of the research progress on carotenoid biosynthesis in R. toruloides, focusing on the understanding of biosynthetic pathways and the regulation of key enzymes and genes involved in the process. Moreover, the relationship between the accumulation of carotenoids and lipid biosynthesis, as well as the stress from diverse abiotic factors, has also been discussed for the first time. Finally, several feasible strategies have been proposed to promote carotenoid production by R. toruloides. It is possible that R. toruloides may become a critical strain in the production of carotenoids or high-value terpenoids by genetic technologies and optimal fermentation processes. KEY POINTS: • Biosynthetic pathway and its regulation of carotenoids in Rhodosporidium toruloides were concluded • Stimulation of abiotic factors for carotenoid biosynthesis in R. toruloides was summarized • Feasible strategies for increasing carotenoid production by R. toruloides were proposed.

The potential of lactose to inhibit cereulide biosynthesis of emetic Bacillus cereus in milk.

This study aims to investigate the potential role of lactose on cereulide biosynthesis by emetic Bacillus cereus in dairy matrices. The cereulide yields in whole milk and lactose-free milk were investigated using the emetic reference strain F4810/72. To eliminate the influence of complex food substrates, the LB medium model was further used to characterize the effect of lactose on cereulide produced by F4810/72 and five other emetic B. cereus strains. Results showed that the lactose-free milk displayed a 13-fold higher amount of cereulide than whole milk, but the cereulide level could be reduced by 91 % when the lactose content was restored. The significant inhibition of lactose on cereulide yields of all tested B. cereus strains was observed in LB medium, showing a dose-dependent manner with inhibition rates ranging of 89-98 %. The growth curves and lactose utilization patterns of all strains demonstrated that B. cereus cannot utilize lactose as a carbon source and lactose might act as a signal molecule to regulate cereulide production. Moreover, lactose strongly repressed the expression of cereulide synthetase genes (ces), possibly by inhibiting the key regulator Spo0A at the transcriptional level. Our findings highlight the potential of lactose as an effective strategy to control cereulide production in food.

Washed microbiota transplantation improves renal function in patients with renal dysfunction: a retrospective cohort study.

BACKGROUND: Changes in the gut microbiota composition is a hallmark of chronic kidney disease (CKD), and interventions targeting the gut microbiota present a potent approach for CKD treatment. This study aimed to evaluate the efficacy and safety of washed microbiota transplantation (WMT), a modified faecal microbiota transplantation method, on the renal activity of patients with renal dysfunction. METHODS: A comparative analysis of gut microbiota profiles was conducted in patients with renal dysfunction and healthy controls. Furthermore, the efficacy of WMT on renal parameters in patients with renal dysfunction was evaluated, and the changes in gut microbiota and urinary metabolites after WMT treatment were analysed. RESULTS: Principal coordinate analysis revealed a significant difference in microbial community structure between patients with renal dysfunction and healthy controls (P = 0.01). Patients with renal dysfunction who underwent WMT exhibited significant improvement in serum creatinine, estimated glomerular filtration rate, and blood urea nitrogen (all P < 0.05) compared with those who did not undergo WMT. The incidence of adverse events associated with WMT treatment was low (2.91%). After WMT, the Shannon index of gut microbiota and the abundance of several probiotic bacteria significantly increased in patients with renal dysfunction, aligning their gut microbiome profiles more closely with those of healthy donors (all P < 0.05). Additionally, the urine of patients after WMT demonstrated relatively higher levels of three toxic metabolites, namely hippuric acid, cinnamoylglycine, and indole (all P < 0.05). CONCLUSIONS: WMT is a safe and effective method for improving renal function in patients with renal dysfunction by modulating the gut microbiota and promoting toxic metabolite excretion.

Impacts of selenium enrichment on nutritive value and obesity prevention of Cordyceps militaris: A nutritional, secondary metabolite, and network pharmacological analysis.

This study aimed to compare the nutritive value and obesity prevention of ordinary Cordyceps militaris (CM) and selenium-enriched CM (SeCM). The results indicated that Se enrichment significantly increased the total carbohydrate and soluble dietary fiber content, while the protein and insoluble dietary fiber content decreased. Although the fat content was not affected, the medium and long-chain fatty acids content significantly changed. Moreover, Se enrichment significantly elevated the secondary metabolites belonging to terpenoids and alkaloids, which are linked with the enhanced biosynthesis of secondary metabolites. Both CM and SeCM reduced body weight, adipose accumulation, impaired glucose tolerance, and lipid levels in high-fat diet (HFD)-fed mice, and there was no significant difference between them. Network pharmacological analysis revealed that dietary CM and SeCM prevented HFD-induced obesity and associated metabolic diseases with multi-ingredients acting on multi-targets. Overall, Se enrichment improved the nutritive value of CM without altering its role in preventing obesity.

Characterization of quinolone resistance in Salmonella enterica serovar Typhimurium and its monophasic variants from food and patients in China.

OBJECTIVES: The study aimed to characterize the quinolone resistance of Salmonella enterica serovar Typhimurium and its monophasic variant (Salmonella enterica serovar 1,4,[5],12:i:-) isolated from food and patients in China. METHODS: All of the isolates were assessed for quinolone susceptibility via the broth microdilution method. Then, the isolates were checked for mutations within quinolone resistance-determining regions of gyrA, gyrB, parC, and parE and were examined for plasmid-mediated quinolone resistance genes. RESULTS: High rates of resistance to nalidixic acid in the S. Typhimurium (70.7%) and S. 1,4,[5],12:i:- (41.9%) isolates were observed, and a considerable proportion of isolates with reduced susceptibility to ciprofloxacin and levofloxacin were also detected. The high frequency of mutations in GyrA (60.8%) and a variety of genes (aac[6']-Ib-cr [23.2%], oqxAB [19.2%], qnrS [13.6%], and qnrA [3.2%]) conferring quinolone resistance in these Salmonella isolates were noteworthy. Lastly, the isolates carrying qnrS for transferability and transmission of the quinolone resistance were analysed by conjugation. Multiple locus variable-number tandem repeat analysis profiles indicated that some qnrS-positive isolates were clonally related, whilst the other isolates were genetically divergent. This suggested that both clonal spread of resistant strains and horizontal transmission of the plasmid-mediated resistance genes contributed to the dissemination of qnrS-positive Salmonella isolates. CONCLUSION: This study highlights the prevalence of quinolone-resistant S. Typhimurium and S. 1,4,[5],12:i:- in China, posing a threat to public health.

Occurrence, molecular characterization and antibiotic resistance of Cronobacter spp. isolated from wet rice and flour products in Guangdong, China.

This study explored the prevalence of Cronobacter spp. in wet rice and flour products from Guangdong province, China, the molecular characteristics and antimicrobial susceptibility profiles of the isolates were identified. Among 249 samples, 100 (40.16%) were positive for Cronobacter spp., including 77 wet rice and 23 wet flour products. Eleven serotypes were characterized among 136 isolates with C. sakazakii O2 (n = 32) predominating. Forty-nine MLST patterns were assigned, 15 of which were new. C. sakazakii ST4 (n = 17) was the dominant ST, which is previously reported to have caused three deaths; followed by C. malonaticus ST7 (n = 15), which is connected to adult infections. All strains presented susceptibility to ampicillin/sulbactam, imipenem, aztreonam and trimethoprim/sulfamethoxazole. The isolates showed maximum resistance to cephalothin, and the resistance and intermediate rates were 91.91% and 3.68%, each. Two strains, croM234A1 and croM283-1, displayed resistance to three antibiotics. High contamination level and predominant number of pathogenic STs of Cronobacter in wet rice and flour products implied a potential risk to public healthiness. This survey could provide comprehensive information for establishing more targeted control methods for Cronobacter spp.

Engineered lytic phage of Bacillus cereus and its application in milk.

Phages have been approved for use in the food industry to control bacterial contamination in some countries. However, their broader adoption is hindered by some limitations. For instance, the persistence of infectious phages in the food industry can lead to the emergence of resistant bacteria, which negatively impacts the long-term effectiveness of phages. Additionally, the narrow host range of phages limits their effectiveness against various strains. To address these deficiencies, phage engineering has been proposed as a rational approach for modifying phages. In this study, we developed a simple and efficient engineering method for Bacillus cereus phage, using DK1 as an example, to reduce the number of residual phages and expand its range of hosts. Specifically, we knocked out the appendage gene, which codes for the receptor-binding protein, to produce phage progeny with structural defects in their appendages, resulting in the loss of infectivity after host elimination. Furthermore, we used plasmid-mediated means to express different appendage proteins during phage preparation, which allowed altering the host spectrum of the engineered phages without gene insertion. In practical applications, our engineered phages effectively reduced the number of B. cereus in milk and prevented the amplification of active progeny. Our strategy transformed phages from active viruses into more controllable antibacterial agents, making them safer and more efficient for the prevention and control of B. cereus. Moreover, we believe this strategy will help drive the use of engineered phages in the food industry.

Gut microbiota: Candidates for a novel strategy for ameliorating sleep disorders.

The aim of this review was to evaluate the feasibility of treating sleep disorders using novel gut microbiota intervention strategies. Multiple factors can cause sleep disorders, including an imbalance in the gut microbiota. Studies of the microbiome-gut-brain axis have revealed bidirectional communication between the central nervous system and gut microbes, providing a more comprehensive understanding of mood and behavioral regulatory patterns. Changes in the gut microbiota and its metabolites can stimulate the endocrine, nervous, and immune systems, which regulate the release of neurotransmitters and alter the activity of the central nervous system, ultimately leading to sleep disorders. Here, we review the main factors affecting sleep, discuss possible pathways and molecular mechanisms of the interaction between sleep and the gut microbiota, and compare common gut microbiota intervention strategies aimed at improving sleep physiology.

Genome Characterization of the Novel Lytic Enterobacter cloacae Phage vB_EclM_Q7622.

Enterobacter cloacae is a widespread opportunistic pathogen that causes urinary tract infection. The abuse of antibiotics enabled multidrug-resistant strains to spread. Bacteriophage therapy is a naturally, safe, and efficient alternative treatment technology against multi-resistant bacteria. In this study, a virulent phage vB_EclM_Q7622 (Q7622) was isolated from the sewage of Jiangcun poultry market in Guangzhou city. Transmission electron microscopy indicated that Q7622 had an icosahedral head (97.8 ± 5.6 nm in diameter) and a short, contractile tail (113.7 ± 4.5 nm). Its double-stranded DNA genome is composed of 173,871 bp with a GC content of 40.02%. It possesses 297 open reading frames and 9 tRNAs. No known virulence and resistance genes were detected, indicated that phage Q7622 could be used for pathogens prevention and control safely. Comparative genomic and phylogenetic analysis showed that Q7622 was highly similar to the phages vB_EclM_CIP9 and vB_EhoM-IME523. The highest nucleotide similarity between Q7622 and the similar phages in NCBI calculated by pyANI and VIRIDIC were 94.9% and 89.1% with vB_EhoM-IME523 respectively, below 95%. Thus, according to the result of nucleotide similarity calculation results, Q7622 was a novel virulent Enterobacter cloacae phage strain of the genus Kanagawavirus.

Brij-58 supplementation enhances menaquinone-7 biosynthesis and secretion in Bacillus natto.

Menaquinone-7 is a form of vitamin K2 that has been shown to have numerous healthy benefits. In this study, several surfactants were investigated to enhance the production of menaquinone-7 in Bacillus natto. Results showed that Brij-58 supplementation influenced the cell membrane via adsorption, and changed the interfacial tension of fermentation broth, while the changes in the state and the composition of the cell membrane enhanced the secretion and biosynthesis of menaquinone-7. The total production and secretion rate of menaquinone-7 increased by 48.0% and 56.2% respectively. During fermentation, the integrity of the cell membrane decreased by 82.9% while the permeability increased by 158% when the maximum secretory rate was reached. Furthermore, Brij-58 supplementation induced the stress response in bacteria, resulting in hyperpolarization of the membrane, and increased membrane ATPase activity. Finally, changes in fatty acid composition increased membrane fluidity by 30.1%. This study provided an effective strategy to enhance menaquinone-7 yield in Bacillus natto and revealed the mechanism of Brij-58 supplementation in menaquinone-7 production. KEY POINTS: • MK-7 yield in Bacillus natto was significantly increased by Brij-58 supplementation. • Brij-58 could be adsorbed on cell surface and change fermentation environment. • Brij-58 supplementation could affect the state and composition of the cell membrane.

Semiquantitative Fingerprinting Based on Pseudotargeted Metabolomics and Deep Learning for the Identification of Listeria monocytogenes and Its Major Serotypes.

The rapid identification of pathogenic microorganism serotypes is still a bottleneck problem to be solved urgently. Compared with proteomics technology, metabolomics technology is directly related to phenotypes and has higher specificity in identifying pathogenic microorganism serotypes. Our study combines pseudotargeted metabolomics with deep learning techniques to obtain a new deep semiquantitative fingerprinting method for Listeria monocytogenes identification at the serotype levels. We prescreened 396 features with orthogonal partial least-squares discrimination analysis (OPLS-DA), and 200 features were selected for deep learning model building. A residual learning framework for L. monocytogenes identification was established. There were 256 convolutional filters in the initial convolution layer, and each hidden layer contained 128 filters. The total depth included seven layers, consisting of an initial convolution layer, a residual layer, and two final fully connected classification layers, with each residual layer containing four convolutional layers. In addition, transfer learning was used to predict new isolates that did not participate in model training to verify the method's feasibility. Finally, we achieved prediction accuracies of L. monocytogenes at the serotype level exceeding 99%. The prediction accuracy of the new strain validation set was greater than 97%, further demonstrating the feasibility of this method. Therefore, this technology will be a powerful tool for the rapid and accurate identification of pathogens.

Proteomic analysis reveals the non-coding small RNA Qrr5 influences autoaggregation and growth competition in Vibrio parahaemolyticus.

Vibrio parahaemolyticus, a sea-born bacterial pathogen, is a primary inducement of food-borne gastroenteritis. Previous studies have shown that non-coding small RNA plays a vital role in the regulation of multiple biological processes in pathogenic bacteria, especially autoaggregation and growth competition. However, the inherent mechanisms have not yet to be fully understood. As important regulators in Vibrios, the involvement of Qrr sRNAs in V. parahaemolyticus is largely unknown. Here, we carried out the Qrr5 deletion mutant and utilized a proteomic method to describe global proteomic alterations in response to Qrr5 deletion. A total of 297 significantly expressed proteins were determined between the Qrr5 deletion mutant and wild-type strain, among which 137 proteins were upregulated and 160 proteins were downregulated. The upregulated proteins principally participated in membrane transporters and signal transcription, while the downregulated proteins participated in the two-component system and transcription factor binding. Notably, transcriptional regulator LysR, outer membrane protein OmpA, and conjugal transfer protein TraA-related proteins were upregulated, causing the promotion of autoaggregation ability and growth competition ability against E. coli. This study provides insights into the regulatory network of sRNA in this bacterium, which will facilitate further explorations of important biological processes in pathogenic bacteria. SIGNIFICANCE: sRNA Qrr5 is an important regulator involved in bacterial multiple physiological processes, including auto-aggregation and growth competition among food-borne pathogens Vibrio parahaemolyticus. Here, utilizing a TMT-labeling proteomic approach, we identified 137 proteins were upregulated and 160 proteins were downregulated between the Qrr5 deletion mutant and wild-type strain. The upregulated proteins were involved in membrane transporters and signal transcription, while downregulated proteins were involved in the two-component system and transcription factor binding. Moreover, the LysR, OmpA, and TraA proteins were significantly upregulated, causing the promotion of autoaggregation and commensal growth competition ability. The mechanism of how Qrr5 regulates the targeted genes remains unclarified and need great efforts to explore.

Structure, chemical stability and antioxidant activity of melanoidins extracted from dark beer by acetone precipitation and macroporous resin adsorption.

Melanoidins contribute to the sensory and functional properties of dark beers. The structure, stability, and antioxidant activity of acetone precipitation extracted melanoidins (APE-M) and macroporous resin adsorption extracted melanoidins (MAE-M) from dark beer were investigated. The structural properties of melanoidins were characterized using Fourier transform infrared spectroscopy (FTIR), circular dichroism (CD), scanning electron microscopy (SEM), and the solution storage stability, thermal behavior and antioxidant activity of melanoidins in dark beers were evaluated. MAE-M revealed more sophisticated structures than APE-M, including more concrete characteristics of Maillard reaction (MR) products in FTIR (1550-1500 cm-1), more ordered secondary structure in CD spectra, and thinner slices as well as more microspheres in SEM. The solution storage stability assay showed that certain factors, including 55 °C, 5 % v/v ethanol, UV light, and H2O2 solution, accelerated the degradation of melanoidins. The moderate extraction process of MAE-M performed a minor enthalpy change (-92.28 Jg-1) in the DSC-TG test than that of APE-M (-319.41 Jg-1). Furthermore, the ABTS and DPPH radical scavenging activities and the FRAP assay demonstrated that the antioxidant activity of MAE-M was almost twice that of APE-M. In general, MAE was more effective in extracting beer melanoidins while maintaining its accurate structure and profitable antioxidant activity than APE.

Effects of probiotics on hypertension.

Emerging data have suggested that probiotics had good potential in regulating intestinal flora and preventing hypertension. Some studies in human and animal models have demonstrated probiotic intervention could attenuate hypertension, regulate intestinal flora to increase the abundance of beneficial bacteria, and regulate intestinal microbial metabolites such as trimethylamine oxide, short-chain fatty acids, and polyphenols. However, there is still some debate as to whether probiotics exert effective benefits. These recently published reviews did not systematically expound on the heterogeneity between the effect and mechanism of probiotics with different types, doses, and carriers to exert antihypertensive effects, as well as the possible application of probiotics in the prevention and treatment of hypertension in food and clinic. Here we try to systematically review the association between hypertension and intestinal microflora, the effect of probiotics and their metabolites on hypertension, and the recent research progress on the specific mechanism of probiotics on hypertension. In addition, we also summarized the potential application of probiotics in antihypertension. Future challenges include elucidating the functions of metabolites produced by microorganisms and their downstream pathway or molecules, identifying specific strains, not just microbial communities, and developing therapeutic interventions that target hypertension by modulation of gut microbes and metabolites.

Metabolism of resistant starch RS3 administered in combination with Lactiplantibacillus plantarum strain 84-3 by human gut microbiota in simulated fermentation experiments in vitro and in a rat model.

This study aimed to investigate the metabolic and population responses of gut microbiota to resistant starch (RS3) in the presence of exogenous Lactiplantibacillus plantarum strain 84-3 (Lp84-3) in vitro and in vivo. Lp84-3 promoted acetate, propionate, and butyrate production from RS3 by gut microbiota and increased Lactobacillus and Blautia contents in vitro. Furthermore, in the presence of Lp84-3, starch granules presented a "dot-by-hole" fermentation pattern. Administration of Lp84-3 with RS3 increased the level of SCFA-producing Faecalibaculum, Parabacteroides, Alistipes, and Anaeroplasma in the faeces of rates, with Lactobacillus and Akkermansia representing the key genera that significantly promoted SCFAs, especially propionate and butyrate. Lp84-3 with RS3 promoted genes related to tryptophan synthase (EC 4.2.1.20) and beta-glucosidase (EC 3.2.1.21) in faecal bacteria. Our findings highlight the ability of Lp84-3 to enhance RS3 degradation, possibly by promoting SCFA-producing bacteria, and indicate that Lp84-3 could be a potential probiotic with a beneficial effect on gut microbiota.

Sensitive and Selective Detection of Enterococcus faecalis Using a New Turn-on Fluorogenic ß-glucosidase Substrate Combined with a Modified Selective Broth.

A new, simple-to-synthesize and sensitive turn-on fluorogenic substrate (CFMU-Glu) for ß-glucosidase activity was developed. This probe was based on a 7-hydroxycoumarin derivative (CFMU) that could emit green fluorescence and had the low pKa value of 5.61 ± 0.01. CFMU-Glu could be used for sensitive monitoring of the almond ßGLU and Enterococcus faecalis (E. faecalis) at the optimal pHs of 6.50 and 7.00, respectively. Moreover, a new sensitive and selective fluorogenic broth (PBF-B) for E. faecalis, utilizing CFMU-Glu and polymyxin B, was also developed. Polymyxin B was discovered to can significantly improve the detection selectivity and signal intensity. The proposed 4-four method using PBF-B and a microcentrifuge tube could provide fluorogenic detection limits of 5.01 × 104 and 1.0 × 105 CFU mL-1 by fluorescence microplate reader and naked eye, respectively; it could also provide a turn-on chromogenic detection limit of 1.0 × 106 CFU mL-1 by naked eye. The proposed method could detect 8 CFU mL-1 of E. faecalis in drinking water, Liangcha (herbal tea) and milk samples within 10 h, without pre-enrichment.

GII.17[P17] and GII.8[P8] noroviruses showed different RdRp activities associated with their epidemic characteristics.

Norovirus is the primary foodborne pathogenic agent causing viral acute gastroenteritis. It possesses broad genetic diversity and the prevalence of different genotypes varies substantially. However, the differences in RNA-dependent RNA polymerase (RdRp) activity among different genotypes of noroviruses remain unclear. In this study, the molecular mechanism of RdRp activity difference between the epidemic strain GII.17[P17] and the non-epidemic strain GII.8[P8] was characterized. By evaluating the evolutionary history of RdRp sequences with Markov Chain Monte Carlo method, the evolution rate of GII.17[P17] variants was higher than that of GII.8[P8] variants (1.22 × 10-3 nucleotide substitutions/site/year to 9.31 × 10-4 nucleotide substitutions/site/year, respectively). The enzyme catalytic reaction demonstrated that the Vmax value of GII.17[P17] RdRp was 2.5 times than that of GII.8[P8] RdRp. And the Km of GII.17[P17] and GII.8[P8] RdRp were 0.01 and 0.15 mmol/L, respectively. Then, GII.8[P8] RdRp fragment mutants (A-F) were designed, among which GII.8[P8]-A/B containing the conserved motif G/F were found to have significant effects on improving RdRp activity. The Km values of GII.8[P8]-A/B reached 0.07 and 0.06 mmol/L, respectively. And their Vmax values were 1.34 times than that of GII.8[P8] RdRp. In summary, our results suggested that RdRp activities were correlated with their epidemic characteristics. These findings will ultimately provide a better understanding in replication mechanism of noroviruses and development of antiviral drugs.

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.

Evaluation of the pathogenesis of non-typical strain with α-hemolysin, Vibrio parahaemolyticus 353, isolated from Chinese seafood through comparative genome and transcriptome analysis.

Vibrio parahaemolyticus outbreaks frequently occur, causing gastrointestinal sickness owing to the consumption of aquatic foods by various virulence factors; however, the mechanism of pathogenesis is still unknown. In this study, a non-typical strain of V. parahaemolyticus, named VP353, was isolated from shrimp in China. Its comparative genome and transcriptome after infection with Caco-2 cells were examined to illustrate the mechanisms of its pathogenesis. VP353 was a tdh-trh- strain but uncommonly manifested robust cytotoxicity towards Caco-2 cells. Compared with the standard strain RIMD2210633, VP353 harbored alpha-hemolysins (hlyA, hlyB, hlyC, and hlyD) was first reported in V. parahaemolyticus and showed high diversity in the T3SS2 gene cluster. Moreover, the expression of flagella, T2SS, quorum sensing-related genes, hlyA, hlyC were up-regulated, and hlyB, hlyD were down-regulated. In summary, our results demonstrate that some novel virulence factors contribute to the pathogenesis of V. parahaemolyticus infection.