The viable but nonculturable state induction and genomic analyses of Lactobacillus casei BM-LC14617, a beer-spoilage bacterium

Comparative analysis of the transcriptional responses of Acetilactobacillus jinshanensis BJ01 to organic acids

As the important functional microorganism in the brewing process of Chinese Baijiu, lactic acid bacteria influences the microbial community and production of flavor substances in the Baijiu brewing process. In this study, we first isolated an Acetilactobacillus jinshanensis strain from baijiu fermented grains and named it A. jinshanensis BJ01. Its optimal growth conditions are 30 °C and pH 3.5. In particular, A. jinshanensis BJ01 cannot utilize inorganic acids and most organic acids, except for lactic acid (HL) and acetic acid (HAc). The observed phenotypes showed good growth with HL. When the mixed acid of HL-HAc (V:V = 1:1) was used, the growth rate of A. jinshanensis BJ01 greatly accelerated. Transcriptomic sequencing revealed the specific responses of the strain to the acidulants used. The number of upregulated genes in HL-HAc medium was more than that in single acid medium (HL or HAc). KEGG enrichment analyses indicated that the glycometabolism level of HAc regulation was relatively downregulated. The gene expression of quorum sensing and ABC transporter pathways were remarkably upregulated under HL-HAc regulation. Pyruvate metabolic pathway may be an important reason for the difference in A. jinshanensis BJ01 response to different organic acids. Our study reported a new organic acid-inducible growth type of bacteria mainly depending on the presence of HL and HAc, and was beneficial to the improvement of fermentation technology of Baijiu.

Methods for detection and identification of beer-spoilage microbes

It is critical that breweries of all sizes routinely monitor the microbiome of their process to limit financial losses due to microbial contamination. Contamination by beer-spoiling microbes (BSMs) at any point during the brewing process may lead to significant losses for breweries if gone undetected and allowed to spread. Testing and detection of BSMs must be routine and rapid, and because even small breweries need the capability of BSM detection and identification, the method also needs to be affordable. Lactic acid bacteria (LAB) are responsible for most spoilage incidents, many of which have been shown to enter the viable but nonculturable (VBNC) state under conditions present in beer such as cold or oxidative stress. These bacteria are invisible to traditional methods of detection using selective media. This article describes several methods of BSM detection and identification that may be useful in the majority of craft breweries. While there are several genomic methods that meet some or many qualifications of being useful in craft breweries, real-time quantitative polymerase chain reaction (qPCR) currently best meets the desired method characteristics and holds the most utility in this industry, specifically SYBR Green qPCR. qPCR is a targeted method of detection and identification of microbes that is affordable, rapid, specific, sensitive, quantitative, and reliable, and when paired with valid DNA extraction techniques can be used to detect BSMs, including those in the VBNC state.

Comparative Analysis Using Raman Spectroscopy of the Cellular Constituents of Lacticaseibacillus paracasei Zhang in a Normal and Viable but Nonculturable State

This study aimed to investigate the molecular composition of a viable but nonculturable (VBNC) state of a probiotic strain, Lacticaseibacillus paracasei Zhang (L. paracasei Zhang), using single-cell Raman spectroscopy (SCRS). Fluorescent microcopy with live/dead cell staining (propidium iodide and SYTO 9), plate counting, and scanning electron microscopy were used in combination to observe bacteria in an induced VBNC state. We induced the VBNC state by incubating the cells in de Man, Rogosa, and Sharpe broth (MRS) at 4 °C. Cells were sampled for subsequent analyses before VBNC induction, during it, and up to 220 days afterwards. We found that, after cold incubation for 220 days, the viable plate count was zero, but active cells could still be observed (as green fluorescent cells) under a fluorescence microscope, indicating that Lacticaseibacillus paracasei Zhang entered the VBNC state under these conditions. Scanning electron microscopy revealed the altered ultra-morphology of the VBNC cells, characterized by a shortened cell length and a wrinkled cell surface. Principal component analysis of the Raman spectra profiles revealed obvious differences in the intracellular biochemical constituents between normal and VBNC cells. Comparative analysis of the Raman spectra identified 12 main differential peaks between normal and VBNC cells, corresponding to carbohydrates, lipids, nucleic acids, and proteins. Our results suggested that there were obvious cellular structural intracellular macromolecular differences between normal and VBNC cells. During the induction of the VBNC state, the relative contents of carbohydrates (such as fructose), saturated fatty acids (such as palmitic acid), nucleic acid constituents, and some amino acids changed obviously, which could constitute a bacterial adaptive mechanism against adverse environmental conditions. Our study provides a theoretical basis for revealing the formation mechanism of a VBNC state in lactic acid bacteria.

Biofilm formation of two genetically diverse Staphylococcus aureus isolates under beta-lactam antibiotics

PURPOSE

Our aim was to evaluate the biofilm formation of 2 genetically diverse Staphylococcus aureus isolates, 10379 and 121940, under different concentrations of beta-lactam antibiotics on biomass content and biofilm viability.

METHODS

Biofilm formation and methicillin resistance genes were tested using PCR and multiplex PCR. PCR was combined with bioinformatics analysis to detect multilocal sequence typing (MLST) and SCCmec types, to study the genetical correlation between the tested strains. Then, the crystal violet (CV) test and XTT were used to detect biomass content and biofilm activity. Antibiotic susceptibility was tested using a broth dilution method. According to their specific MIC, different concentrations of beta-lactam antibiotics were used to study its effect on biomass content and biofilm viability.

RESULTS

Strain 10379 carried the icaD, icaBC, and MRSA genes, not the icaA, atl, app, and agr genes, and MLST and SCCmec typing was ST45 and IV, respectively. Strain 121940 carried the icaA, icaD, icaBC, atl, and agr genes, not the aap gene, and MLST and SCCmec typed as ST546 and IV, respectively. This suggested that strains 10379 and 121940 were genotypically very different. Two S. aureus isolates, 10379 and 121940, showed resistance to beta-lactam antibiotics, penicillin, ampicillin, meropenem, streptomycin and kanamycin, some of which promoted the formation of biofilm and biofilm viability at low concentrations.

CONCLUSION

Despite the large differences in the genetic background of S. aureus 10379 and 121940, some sub-inhibitory concentrations of beta-lactam antibiotics are able to promote biomass and biofilm viability of both two isolates.

Formic acid, an organic acid food preservative, induces viable-but-non-culturable state, and triggers new Antimicrobial Resistance traits in Acinetobacter baumannii and Klebsiella pneumoniae

Numerous human pathogens, especially Gram-negative bacteria, are able to enter the viable-but-non-culturable (VBNC) state when they are exposed to environmental stressors and pose the risk of being resuscitated and causing infection after the removal of the trigger. Widely used food preservatives like weak organic acids are potential VBNC inducers in food processing and packaging facilities but have only been reported for food-borne pathogens. In the present study, it is demonstrated for the first time that one such agent, formic acid (FA), can induce a VBNC state at food processing, storage, and distribution temperatures (4, 25, and 37°C) with a varied time of treatment (days 4-10) in pathogenic Gram-negative bacteria Acinetobacter baumannii and Klebsiella pneumoniae. The use of hospital-associated pathogens is critical based on the earlier reports that demonstrated the presence of these bacteria in hospital kitchens and commonly consumed foods. VBNC induction was validated by multiple parameters, e.g., non-culturability, metabolic activity as energy production, respiratory markers, and membrane integrity. Furthermore, it was demonstrated that the removal of FA was able to resuscitate VBNC with an increased expression of multiple virulence and Antimicrobial Resistance (AMR) genes in both pathogens. Since food additives/preservatives are significantly used in most food manufacturing facilities supplying to hospitals, contamination of these packaged foods with pathogenic bacteria and the consequence of exposure to food additives emerge as pertinent issues for infection control, and control of antimicrobial resistance in the hospital setting.

From the Raw Materials to the Bottled Product: Influence of the Entire Production Process on the Organoleptic Profile of Industrial Beers

In the past few years, there has been a growing demand by consumers for more complex beers with distinctive organoleptic profiles. The yeast, raw material (barley or other cereals), hops, and water used add to the major processing stages involved in the brewing process, including malting, mashing, boiling, fermentation, and aging, to significantly determine the sensory profile of the final product. Recent literature on this subject has paid special attention to the impact attributable to the processing conditions and to the fermentation yeast strains used on the aromatic compounds that are found in consumer-ready beers. However, no review papers are available on the specific influence of each of the factors that may affect beer organoleptic characteristics. This review, therefore, focuses on the effect that raw material, as well as the rest of the processes other than alcoholic fermentation, have on the organoleptic profile of beers. Such effect may alter beer aromatic compounds, foaming head, taste, or mouthfeel, among other things. Moreover, the presence of spoilage microorganisms that might lead to consumers’ rejection because of their impact on the beers’ sensory properties has also been investigated.

In vitro antimicrobial effect and mechanism of action of plasma-activated liquid on planktonic Neisseria gonorrhoeae

Neisseria gonorrhoeae (Ng) is highly resistant to treatment, and there is an urgent need for new treatments to alleviate gonococcal resistance caused by antibiotic monotherapy. The antimicrobial effect and mechanism of plasma-activated liquid (PAL) on Ng were evaluated in this study. Upon PAL treatment, extensively analyses on cell culturability, metabolic capacity, intracellular reactive oxygen species (ROS),membrane integrity and nucleic acids for Ng were carried out and significant antimicrobial effects observed.PAL exerted antibacterial effect on Ng and induced bacterial death (6.71-log) following immersion for 30 min and treatment for 120 s. However, bacterial viability test revealed that after immersion in the same PAL, 10.17% of bacteria retained their metabolic capacity. This indicates that bacteria enter a physiological viable but non-culturable state to protect themselves from environmental stress. Confocal fluorescence microscopy and transmission electron microscopy demonstrated that PAL exerts bactericidal effect on Ng and disrupts its morphological structure. PAL may upregulate inflammatory factors and genes to modulate the resistance of Ng and affect the immune status of the host during infection.

Pathogenic and Virulence Factor Detection on Viable but Non-culturable Methicillin-Resistant Staphylococcus aureus

Food safety and foodborne infections and diseases have been a leading hotspot in public health, and methicillin-resistant Staphylococcus aureus (MRSA) has been recently documented to be an important foodborne pathogen, in addition to its recognition to be a leading clinical pathogen for some decades. Standard identification for MRSA has been commonly performed in both clinical settings and food routine detection; however, most of such so-called "standards," "guidelines," or "gold standards" are incapable of detecting viable but non-culturable (VBNC) cells. In this study, two major types of staphylococcal food poisoning (SFP), staphylococcal enterotoxins A (sea) and staphylococcal enterotoxins B (seb), as well as the panton-valentine leucocidin (pvl) genes, were selected to develop a cross-priming amplification (CPA) method. Limit of detection (LOD) of CPA for sea, seb, and pvl was 75, 107.5, and 85 ng/μl, indicating that the analytical sensitivity of CPA is significantly higher than that of conventional PCR. In addition, a rapid VBNC cells detection method, designated as PMA-CPA, was developed and further applied. PMA-CPA showed significant advantages when compared with PCR assays, in terms of rapidity, sensitivity, specificity, and accuracy. Compared with conventional VBNC confirmation methods, the PMA-CPA showed 100% accordance, which had demonstrated that the PMA-CPA assays were capable of detecting different toxins in MRSA in VBNC state. In conclusion, three CPA assays were developed on three important toxins for MRSA, and in combination with PMA, the PMA-CPA assay was capable of detecting virulent gene expression in MRSA in the VBNC state. Also, the above assays were further applied to real samples. As concluded, the PMA-CPA assay developed in this study was capable of detecting MRSA toxins in the VBNC state, representing first time the detection of toxins in the VBNC state.

Spoilage Lactic Acid Bacteria in the Brewing Industry

Lactic acid bacteria (LAB) have caused many microbiological incidents in the brewing industry, resulting in severe economic loss. Meanwhile, traditional culturing method for detecting LAB are time-consuming for brewers. The present review introduces LAB as spoilage microbes in daily life, with focus on LAB in the brewing industry, targeting at the spoilage mechanism of LAB in brewing industry including the special metabolisms, the exist of the viable but nonculturable (VBNC) state and the hop resistance. At the same time, this review compares the traditional and novel rapid detection methods for these microorganisms which may provide innovative control and detection strategies for preventing alcoholic beverage spoilage, such as improvement of microbiological quality control using advanced culture media or different isothermal amplification methods.

Inactivation kinetics of beer spoilage bacteria (Lactobacillus brevis, Lactobacillus casei, and Pediococcus damnosus) during acid washing of brewing yeast

This work aimed to estimate the inactivation kinetic parameters of four potential beer spoilage bacteria (Lactobacillus brevis DSM 6235, Lactobacillus casei ATCC 334, Pediococcus damnosus DSM 20289 and Pediococcus damnosus ATCC 29358) inoculated in brewing yeast submitted to acid washing with purposes of yeast recycle. The experiments were conducted at 4 °C in solutions with pH 1.5, pH 2, and pH 3 adjusted employing 85% phosphoric acid. The acid washing treatment of brewing yeasts in the most common pH used (pH 2.0) demanded almost 50 min for the first decimal reduction (δ) of L. brevis DSM 6235. Sensible strains to acid washing such as P. damnosus DSM 20289 demanded almost 70 min for 4 log reductions to be achieved. On the other hand, pH reduction of the acid washing from 2.0 to 1.5 allowed 4 log reduction of L. brevis DSM 6235) to be obtained in less than 50 min, without ruining brewer's yeast viability. Acid washing in pH 1.5 is a viable method for the inactivation of bacterial contaminants of brewing yeasts. Recycling of brewing yeasts through this approach may contribute to a more sustainable and environmental-friendly industry.

Microbiome characterization and re-design by biologic agents for inflammatory bowel disease insights

The therapeutic effect of inflammatory bowel disease has improved in the past decades, but most of patients cannot tolerate, do not respond to drugs, or relapse after treating with conventional therapy. Therefore, new and more effective treatment methods are still needed in treatment of IBD. In this review, we will discuss the relevant mechanisms and the latest research progress of biologics (anti-TNF treatments, interleukin inhibitors, integrin inhibitors, antisense oligonucleotide, and JAK inhibitors) for IBD, focus on the efficacy and safety of drugs for moderate-to-severe IBD, and summarize the clinical status and future development direction of biologics in IBD.

Characterization on gut microbiome of PCOS rats and its further design by shifts in high-fat diet and dihydrotestosterone induction in PCOS rats

Polycystic ovary syndrome (PCOS) is associated with gut microbiota disturbance. Emerging evidence has shown that gut microbiota plays a major role in the development of PCOS. To better understand how the gut microbiota contributes to the development of PCOS, we investigated the influences of high-fat diet and hyperandrogenism, independently or synergistically, have on the gut microbiota in rats. Furthermore, we explored the associations between gut microbiota and hyperandrogenism or other hallmarks of PCOS. Twenty female SD rats were randomized at aged 3 weeks into 4 groups (n = 5, each); HA: PCOS rats fed with ordinary diet; HF: rats with high-fat diet (HFD); HA-HF: PCOS rats fed with HFD; and C: control rats with ordinary diet. PCOS rat model was induced by 5α-dihydrotestosterone (DHT) injection for 6 weeks. The fasting blood glucose (FBG), plasma insulin, testosterone, free testosterone, TNF-α, MDA, SOD, LPS, TLR4, TG, TC, HDL-C, and LDL-C levels were measured. The molecular ecology of the fecal gut microbiota was analyzed by 16S rDNA high-throughput sequencing. The results showed that rats in the HA and HA-HF group displayed abnormal estrous cycles with increasing androgen level and exhibited multiple large cysts with diminished granulosa layers in ovarian tissues. Compare with the C group, relative abundance of the Bacteroidetes phylum decreased significantly in the other groups (P < 0.05). The Chao1 was the highest in the group C and significantly higher than the HA-HF group (P < 0.05). T, FT, insulin, MDA, LPS, and TNF-α levels had the negative correlation with the richness of community (Chao1 index) in the gut. The rats in the HF and HA-HF groups tended to have lower Shannon and Simpson indices than the C group (P < 0.01, respectively). However, there were no significant differences between C group and the HA group in the Shannon and Simpson values. Beta diversity analysis was then performed based on a weighted UniFrac analysis. The PCoA plots showed a clear separation of the C group from the other groups. ANOSIM analysis of variance confirmed that there were statistically significant separations between the C group and the HA, HA-HF, and HF groups (P < 0.01, respectively). These results showed that DHT with HFD could lower diversity of the gut microbial community. Both HFD and DHT could shift the overall gut microbial composition and change the composition of the microbial community in gut. Furthermore, our analyses demonstrated that the levels of TG, MDA, TNF-α, LPS, TLR4, T, FT, FINS, and HDL-C were correlated with the changes of in the gut microbiome. HFD and DHT were associated with the development and pathology of PCOS by shaping gut microbial communities.

First Report on the Rapid Detection and Identification of Methicillin-Resistant Staphylococcus aureus (MRSA) in Viable but Non-culturable (VBNC) Under Food Storage Conditions

Formation of viable but non-culturable (VBNC) status in methicillin-resistant Staphylococcus aureus (MRSA) has never been reported, and it poses a significant concern for food safety. Thus, this study aimed to firstly develop a rapid, cost-effective, and efficient testing method to detect and differentiate MRSA strains in the VBNC state and further apply this in real food samples. Two targets were selected for detection of MRSA and toxin, and rapid isothermal amplification detection assays were developed based on cross-priming amplification methodology. VBNC formation was performed for MRSA strain in both pure culture and in artificially contaminated samples, then propidium monoazide (PMA) treatment was further conducted. Development, optimization, and evaluation of PMA-crossing priming amplification (CPA) were further performed on detection of MRSA in the VBNC state. Finally, application of PMA-CPA was further applied for detection on MRSA in the VBNC state in contaminated food samples. As concluded in this study, formation of the VBNC state in MRSA strains has been verified, then two PMA-CPA assays have been developed and applied to detect MRSA in the VBNC state from pure culture and food samples.

Induction and Recovery of the Viable but Nonculturable State of Hop-Resistance Lactobacillus brevis

Lactobacillus brevis is a major hop-resistance bacterium which poses significant challenge for the brewing industry, mainly due to the difficulty or incapability in detection by routine culturing methodology and its beer spoilage ability.This study aimed at investigating the VBNC state of a hop-resistance strain, L. brevis BM-LB13908. The culturable, total and viable numbers of L. brevis cells were calculated by MRS agar plate counting, acridine orange direct count (AODC) method and Live/Dead BacLight bacterial viability kit with fluorescence microscope. VBNC formation was induced by 189 ± 5.7 days under low-temperature storage or 27 ± 1.2 subcultures by continuous passage in beer, and VBNC cells induced by both strategies were recovered by adding catalase. In addition, insignificant difference in beer-spoilage ability was found in 3 states of L. brevis, including logarithmic growing, VBNC and recovered cells. This is the first study on the formation of VBNC state for L. brevis and beer-spoilage ability of both VBNC and recovered cells, which indicate L. brevis strain could cause beer spoilage without being detected by routine methodologies. The results derived from this study may support further study on L. brevis and other hop-resistance bacteria, and guidance on beer spoilage prevention and control, such as improvement for brewers on the microbiological quality control by using the improved culture method with catalase supplementation.

Discovery and control of culturable and viable but non-culturable cells of a distinctive Lactobacillus harbinensis strain from spoiled beer

Occasional beer spoilage incidents caused by false-negative isolation of lactic acid bacteria (LAB) in the viable but non-culturable (VBNC) state, result in significant profit loss and pose a major concern in the brewing industry. In this study, both culturable and VBNC cells of an individual Lactobacillus harbinensis strain BM-LH14723 were identified in one spoiled beer sample by genome sequencing, with the induction and resuscitation of VBNC state for this strain further investigated. Formation of the VBNC state was triggered by low-temperature storage in beer (175 ± 1.4 days) and beer subculturing (25 ± 0.8 subcultures), respectively, and identified by both traditional staining method and PMA-PCR. Resuscitated cells from the VBNC state were obtained by addition of catalase rather than temperature upshift, changing medium concentration, and adding other chemicals, and both VBNC and resuscitated cells retained similar beer-spoilage capability as exponentially growing cells. In addition to the first identification of both culturable and VBNC cells of an individual L. harbinensis strain from spoiled beer, this study also for the first time reported the VBNC induction and resuscitation, as well as verification of beer-spoilage capability of VBNC and resuscitated cells for the L. harbinensis strain. Genes in association with VBNC state were also identified by the first genome sequencing of beer spoilage L. harbinensis. The results derived from this study suggested the contamination and spoilage of beer products by VBNC and resuscitated L. harbinensis strain BM-LH14723.

High flux isothermal assays on the pathogenic features of Mycoplasma pneumoniae

As one of the most important pathogens, M. pneumoniae is a causative agent responsible for atypical and other respiratory tract infections, even its extra-pulmonary complications. This study aims to use the high and rapid flux sequencing assays on the M. pneumoniae and further bioinformatic analysis, for the investigation of their clinical features and pathogenic characteristics. The results in this study on the clinical features and pathogenic characteristics of M. pneumoniae may further aid in the control and surveillance and better understanding of this pathogen.

Complete genomic analysis of multidrug-resistance Pseudomonas aeruginosa Guangzhou-Pae617, the host of megaplasmid pBM413

OBJECTIVES

We previously described the novel qnrVC6 and bla_IMP-45 carrying megaplasmid pBM413. This study aimed to investigate the complete genome of multidrug-resistance P. aeruginosa Guangzhou-Pae617, a clinical isolate from the sputum of a patient who was suffering from respiratory disease in Guangzhou, China.

METHODS

The genome was sequenced using Illumina Hiseq 2500 and PacBio RS II sequencers and assembled de novo using HGAP. The genome was automatically and manually annotated.

RESULTS

The genome of P. aeruginosa Guangzhou-Pae617 is 6,430,493 bp containing 5881 predicted genes with an average G + C content of 66.43%. The genome showed high similarity to two new sequenced P. aeruginosa strains isolated from New York, USA. From the whole genome sequence, we identified a type IV pilin, two large prophages, 15 antibiotic resistant genes, 5 genes involved in the "Infectious diseases" pathways, and 335 virulence factors.

CONCLUSIONS

The antibiotic resistance and virulence factors in the genome of P. aeruginosa strain Guangzhou-Pae617 were identified by complete genomic analysis. It contributes to further study on antibiotic resistance mechanism and clinical control of P. aeruginosa.

Physical relation and mechanism of ultrasonic bactericidal activity on pathogenic E. coli with WPI

OBJECTIVE

This study aimed to investigate the physical relation and mechanism of bactericidal activity on pathogenic E. coli by ultrasonic field with whey protein isolate (WPI).

METHODS

Ultrasound treatment was performed under the conditions of intensity at 65 W/cm², pulse duty ratio at 0.5 for 0-15 min with WPI concentration ranged from 0 to 10%. Viscosity, granularity, surface hydrophobicity, free radical scavenging activity, and thermal denaturation were assessed by rotational viscometer, Malvern Mastersizer 2000 particle size analyzer, fluorescent probe ANS method, DPPH method, and differential scanning calorimetry, respectively.

RESULTS

The thermal denaturation of WPI was not altered by ultrasound field, but the viscosity of WPI was increased upon 10 min treatment. Additionally, its ability to scavenge free radicals and hydrophobicity were increased. The result also showed that the bacteria viability was improved by WPI during ultrasound treatment. However, the WPI protection was decreased by the prolonged treatment.

CONCLUSION

Ultrasound treatment resulted in the increasing of the viscosity, free radicals scavenging activity and hydrophobicity of WPI which led to reduced bactericidal activity on E. coil, while WPI protection was disintegrated by prolonged treatment.

High flux isothermal assays on pathogenic, virulent and toxic genetics from various pathogens

Toxins, encoding by virulence factors, are significant cause of food-borne illnesses and death in the worldwide. Loop-mediated isothermal amplification (LAMP) is one of the widely used methodologies because of the high sensitivity, specificity and rapidity. Nowadays, LAMP has been regarded as an innovative gene amplification technology and emerged as an alternative to PCR-based methodologies in identification of the pathogenic virulent and toxic genetics. The high sensitivity of LAMP enables detection of the pathogens in sample materials even without time consuming and sample preparation. Therefore, we review the typical characteristics of LAMP assay, recent advance in detection of virulence factors and the application of LAMP assay on detection of four commonly virulence factors. As concluded, with the advantages of rapidity, simplicity, sensitivity, specificity and robustness, LAMP is capable of identification the virulence factors. Moreover, the main purpose of this review is to provide theory support for the application of LAMP assay on the virulence factors identification.

Correlation and in vitro mechanism of bactericidal activity on E. coli with whey protein isolate during ultrasonic treatment

OBJECTIVE

This study aimed to investigate correlation and in vitro mechanism of bactericidal activity on E. coli with whey protein isolate (WPI) during ultrasonic treatment.

METHODS

The structural changes of WPI under ultrasonic field were studied by amino-acid analyzer, circular dichroism, SDS-PAGE, and spectrophotometer.

RESULTS

With the increasing of WPI concentration added during ultrasonic treatment, the survival rate of E. coli increased. The influence of WPI on bactericidal activity under ultrasonic treatment might due to the change of tertiary and higher level structures, not by the primary structure, and had little relation with secondary structure.

CONCLUSION

The influence of WPI on bactericidal activity during ultrasonic treatment might due to the change of the tertiary structure and higher level structures.

Study on the excision and integration mediated by class 1 integron in Streptococcus pneumoniae

As a novel antibiotic resistance mobile element, integron was recognized as a primary source of antibiotic genes among Gram-positive organisms for its excision and integration of exogenous genes. In this study, Streptococcus pneumoniae was subjected to investigate the excision and integration of class 1 integron with eight different plasmids. As the results indicated, excision in both att site and gene cassettes were successfully observed, which was further confirmed by integration assays and PCR amplification. The observation of class 1 integron mediated excision and integration of various exogenous antibiotics resistance genes may raise the attention of integrons as novel antibiotic resistance determinant in Gram-positive bacteria, especially in Streptococcus.

Microbial pathogenicity and virulence mediated by integrons on Gram-positive microorganisms

Gram-positive microorganisms are one of leading pathogenic microorganisms in public health, including several typical "Super Bugs" as methicillin-resistant Staphylococcus aureus, Klebsiella pneumoniae carbapenemase and vancomycin-resistant enterococci, which caused a increasement of infections, clinical failures and expenses. Regarded as a common genetic element responsible for horizontal gene transfer, integrons are widely distributed in various pathogens considered as a determinant in the acquisition and evolution of antibiotic resistance. Current investigations mainly focus on the distribution of integrons in Gram-negative microorganisms, while the role of integron in antibiotic resistance among Gram-positive microorganisms remains unclear and need investigation. To date, the surveillances of integrons in Gram-positive microorganism have been widely conducted in clinic, community even husbandry. China remains one of the worst country in antibiotics abuse worldwide and considered as a potential area for the prevalence of antimicrobial microorganisms and the occurrence of various 'Super Bugs'. Recently, the surveillance of the occurrence of integron and resistance gene cassettes was conducted in South China during the first 10 years of the 21st century. Referred to the surveillance in South China and other investigation in Asian countries, this review aims to summarize the occurrence, pathogenicity and virulence mediated by integrons in typical Gram-positive microorganisms (Staphylococcus, Enterococcus, Corynebacterium and Streptococcus) and the role of integrons in antibiotic resistance.

Effect of aminoglycosides on the pathogenic characteristics of microbiology

Infections caused by pathogen remain to be one of the most important global health issues, and scientists are devoting themselves to seeking effective treatments. Aminoglycoside antibiotics are one kind of widely used antibiotics because of the good efficiency and broad antimicrobial-spectrum. However, it causes some unexpected effects on the pathogenic characteristics of microbiology during the treatment, such as drug resistance and biofilm promotion. Drug resistance is partly due to antibiotics abuse. Simultaneously, aminoglycoside is documented to make divergent effects on biofilm based on their concentrations. Here, we review the mechanism of drug resistance caused by long-term use of aminoglycoside antibiotics, the effects of antibiotic concentration on biofilm formation and the negative effects on intestinal flora to provide theoretical supports for rational use of antibiotics.

Pathogenic features and characteristics of food borne pathogens biofilm: Biomass, viability and matrix

Biofilm is a ubiquitous growth pattern of bacterial species survival but is notorious for its threat on public health and food contamination. Extensive studies of the biofilm structure, formation, quantification, quorum sensing system and underlying control strategies have been reported during the past decades. Insightful elucidation of the pathogenic features and characteristic of bacterial biofilm can facilitate in devising appropriate control strategies for biofilm eradication. Therefore, this review mainly summarized the pathogenic features of biofilms from food borne microorganisms, including the biomass (which could be quantified using crystal violet and fluorogenic dye Syto9 assays), viability (which could be determined by tetrazolium salts, fluorescein diacetate, resazurin staining and alamar blue assays) and matrix (which are commonly detected by dimethyl methylene blue and wheat germ agglutinin assays). In addition, three features were further compared with its particular benefits in specific application.

The viable but nonculturable state induction and genomic analyses of Lactobacillus casei BM-LC14617, a beer-spoilage bacterium

This study aimed to investigate the viable but nonculturable (VBNC) state and genomic features of a beer‐spoilage strain, Lactobacillus caseiBM‐LC14617. Induction on the VBNC state of L. casei strain BM‐LC14617 was conducted by both low‐temperature storage and continuous passage in beer, and formation of VBNC state was detected after 196 ± 3.3 days and 32 ± 1.6 subcultures, respectively. Resuscitation of VBNC cells was successfully induced by addition of catalase, and culturable, VBNC, and resuscitated cells shared similar beer‐spoilage capability. Whole genome sequencing was performed, and out of a total of 3,964 predicted genes, several potential VBNC and beer‐spoilage‐associated genes were identified. L. casei is capable of entering into and resuscitating from the VBNC state and possesses beer‐spoilage capability. The genomic characterization yield insightful elucidation of VBNC state for L. casei. This study represents the first evidence on VBNC state induction of L. casei and beer‐spoilage capability of VBNC and resuscitated cells. Also, this is the first genomic characterization of L. casei as a beer‐spoilage bacterium. The current study may aid in further study on L. casei and other beer‐spoilage bacteria, and guide the prevention and control of beer spoilage.