甘草提取物对Staphylococcus aureus的抑菌活性及作用机理

食源性病菌为食品安全带来了巨大挑战,甘草提取物作为食品添加剂对金黄色葡萄球菌(Staphylococcus aureus)具有良好的抑菌作用,可作为天然食品防腐剂的候选原料,但目前对其抑菌机理的研究还不深入,影响了其应用。为探究甘草提取物对S.aureus的抑菌机理,该研究通过生长曲线、氧化损伤实验、细胞膜壁分析、蛋白质分析和DNA分析,评价了甘草提取物对S.aureus的抑菌作用机制。结果表明,甘草提取物导致S.aureus核酸渗漏,说明其膜完整性被破坏;同时,甘草提取物降低了几种能量代谢酶:琥珀酸脱氢酶(succinate dehydrogenase,SDH)和总ATP酶的活力;此外,光谱和竞争分析表明,甘草提取物与DNA发生了静电结合和凹槽结合。总之,甘草提取物主要是通过对S.aureus细胞壁膜、蛋白质合成、细菌代谢活力和遗传物质发挥作用,从而抑制其生长。该研究为甘草提取物在食品防腐方面的应用提供了理论基础。

Staphylococcus aureus and biofilms:transmission, threats, and promising strategies in animal husbandry

Staphylococcus aureus(S. aureus) is a common pathogenic bacterium in animal husbandry that can cause diseases such as mastitis, skin infections, arthritis, and other ailments. The formation of biofilms threatens and exacerbates S. aureus infection by allowing the bacteria to adhere to pathological areas and livestock product surfaces, thus triggering animal health crises and safety issues with livestock products. To solve this problem, in this review, we provide a brief overview of the harm caused by S. aureus and its biofilms on livestock and animal byproducts(meat and dairy products). We also describe the ways in which S. aureus spreads in animals and the threats it poses to the livestock industry. The processes and molecular mechanisms involved in biofilm formation are then explained. Finally, we discuss strategies for the removal and eradication of S. aureus and biofilms in animal husbandry, including the use of antimicrobial peptides, plant extracts, nanoparticles, phages, and antibodies. These strategies to reduce the spread of S. aureus in animal husbandry help maintain livestock health and improve productivity to ensure the ecologically sustainable development of animal husbandry and the safety of livestock products.

Elimination of methicillin‑resistant Staphylococcus aureus biofilms on titanium implants via photothermally‑triggered nitric oxide and immunotherapy for enhanced osseointegration

Background:Treatment of methicillin-resistant Staphylococcus aureus(MRSA)biofilm infections in implant placement surgery is limited by the lack of antimicrobial activity of titanium(Ti)implants.There is a need to explore more effective approaches for the treatment of MRSA biofilm infections.Methods:Herein,an interfacial functionalization strategy is proposed by the integration of mesoporous polydopamine nanoparticles(PDA),nitric oxide(NO)release donor sodium nitroprusside(SNP)and osteogenic growth peptide(OGP)onto Ti implants,denoted as Ti-PDA@SNP-OGP.The physical and chemical properties of Ti-PDA@SNP-OGP were assessed by scanning electron microscopy,X-ray photoelectron spectroscope,water contact angle,photothermal property and NO release behavior.The synergistic antibacterial effect and elimination of the MRSA biofilms were evaluated by 2′,7′-dichlorofluorescein diacetate probe,1-N-phenylnaphthylamine assay,adenosine triphosphate intensity,O-nitrophenyl-β-D-galactopyranoside hydrolysis activity,bicinchoninic acid leakage.Fluorescence staining,assays for alkaline phosphatase activity,collagen secretion and extracellular matrix mineralization,quantitative real‑time reverse transcription‑polymerase chain reaction,and enzyme-linked immunosorbent assay(ELISA)were used to evaluate the inflammatory response and osteogenic ability in bone marrow stromal cells(MSCs),RAW264.7 cells and their co-culture system.Giemsa staining,ELISA,micro-CT,hematoxylin and eosin,Masson's trichrome and immunohistochemistry staining were used to evaluate the eradication of MRSA biofilms,inhibition of inflammatory response,and promotion of osseointegration of Ti-PDA@SNP-OGP in vivo.Results:Ti-PDA@SNP-OGP displayed a synergistic photothermal and NO-dependent antibacterial effect against MRSA following near-infrared light(NIR)irradiation,and effectively eliminated the formed MRSA biofilms by inducing reactive oxygen species(ROS)-mediated oxidative stress,destroying bacterial membrane integrity and causing leakage of intracellular components(P<0.01).In vitro experiments revealed that Ti-PDA@SNP-OGP not only facilitated osteogenic differentiation of MSCs,but also promoted the polarization of pro-inflammatory M1 macrophages to the anti-inflammatory M2-phenotype(P<0.05 or P<0.01).The favorable osteo-immune microenvironment further facilitated osteogenesis of MSCs and the anti-inflammation of RAW264.7 cells via multiple paracrine signaling pathways(P<0.01).In vivo evaluation confirmed the aforementioned results and revealed that Ti-PDA@SNP-OGP induced ameliorative osseointegration in an MRSA-infected femoral defect implantation model(P<0.01).Conclusions:Ti-PDA@SNP-OGP is a promising multi-functional material for the high-efficient treatment of MRSA infections in implant replacement surgeries.

Structural insights on anti-biofilm mechanism of heated slightly acidic electrolyzed water technology against multi-resistant Staphylococcus aureus biofilm on food contact surface

Slightly acidic electrolyzed water(SAEW)has proven to be an efficient and novel sanitizer in food and agriculture field.This study assessed the efficacy of SAEW(30 mg/L)at 40℃on the inactivation of foodbome pathogens and detachment of multi-resistant Staphylococcus aureus(MRSA)biofilm.Furthermore.the underlying mechanism of MRS A biofilm under heated SAEW at 40℃treatment on metabolic profiles was investigated.The results showed that the heated SAEW at 40℃significantly effectively against foodbome pathogens of 1.96-7.56(lg(CFU/g))reduction in pork,chicken,spinach,and lettuce.The heated SAEW at 40℃treatment significantly reduced MRS A biofilm cells by 2.41(lg(CFU/cm^(2))).The synergistic effect of SAEW treatment showed intense anti-biofilm activity in decreasing cell density and impairing biofilm cell membranes.Global metabolic response of MRSA biofilms,treated by SAEW at 40℃,revealed the alterations of intracellular metabolites,including amino acids,organic acid,fatty acid,and lipid.Moreover,signaling pathways involved in amino acid metabolism,energy metabolism,nucleotide synthesis,carbohydrate metabolites,and lipid biosynthesis were functionally disrupted by the SAEW at 40℃treatment.As per our knowledge,this is the first research to uncover the potential mechanism of heated SAEW treatment against MRSA biofilm on food contact surface.

Eugenol targeting CrtM inhibits the biosynthesis of staphyloxanthin in Staphylococcus aureus

Staphylococcus aureus is a serious foodborne pathogen threatening food safety and public health.Especially the emergence of methicillin-resistant Staphylococcus aureus(MRSA)increased the difficulty of S.aureus treatment.Staphyloxanthin is a crucial virulence factor of S.aureus.Blocking staphyloxanthin production could help the host immune system counteract the invading S.aureus cells.In this study,we first screened for staphyloxanthin inhibitors using a virtual screening method.The outcome of the virtual screening method resulted in the identification of eugenol(300μg/mL),which significantly inhibits the staphyloxanthin production in S.aureus ATCC 29213,S.aureus Newman,MRSA ATCC 43300 and MRSA ATCC BAA1717by 84.2%,63.5%,68.1%,and 79.5%,respectively.The outcome of the growth curve assay,field-emission scanning electron,and confocal laser scanning microscopy analyses confirmed that eugenol at the test concentration did not affect the morphology and growth of S.aureus.Moreover,the survival rate of S.aureus ATCC 29213 and MRSA ATCC 43300 under H_(2)O_(2) pressure decreased to 51.9%and 45.5%in the presence of eugenol,respectively.The quantitative RT-PCR and molecular simulation studies revealed that eugenol targets staphyloxanthin biosynthesis by downregulating the transcription of the crtM gene and inhibiting the activity of the CrtM enzyme.Taken together,we first determined that eugenol was a prominent compound for staphyloxanthin inhibitor to combat S.aureus especially MRSA infections.

Electrochemical and colorimetric dual-signal detection of Staphylococcus aureus enterotoxin B based on AuPt bimetallic nanoparticles loaded Fe-N-C single atom nanocomposite

Sensitive detection of Staphylococcus aureus enterotoxin B(SEB)is of importance for preventing food poisoning from threatening human health.In this work,an electrochemical and colorimetric dual-signal detection assay of SEB was developed.The probe(Ab2/AuPt@Fe-N-C)was bound to SEB captured by Ab1,where the Ab2/AuPt@Fe-N-C triggered methylene blue degradation and resulted in the decrease of electrochemical signal.Furthermore,the probe catalyzed the oxidation of 3,3’,5,5’-tetramethyl biphenyl to generate a colorimetric absorbance at 652 nm.Once the target was captured and formed a sandwich-like complex,the color changed from colorless to blue.SEB detection by colorimetric and electrochemical methods showed a linear relationship in the concentration ranges of 0.0002-10.0000 and 0.0005-10.0000 ng/mL,with limits of detection of 0.0667 and 0.1670 pg/mL,respectively.The dual-signal biosensor was successfully used to detect SEB in milk and water samples,which has great potential in toxin detection in food and the environment.

The ever-changing microenvironment of Staphylococcus aureus in cutaneous infections

Background:Staphylococcus aureus is responsible for the majority of skin and soft tissue infections,which are often diagnosed at a late stage,thereby impacting treatment efficacy.Our study was designed to reveal the physiological changes at different stages of infection by S.aureus through the combined analysis of variations in the skin microenvironment,providing insights for the diagnosis and treatment of S.aureus infections.Methods:We established a murine model of skin and soft tissue infection with S.aureus as the infectious agent to investigate the differences in the microenvironment at different stages of infection.By combining analysis of the host immune status and histological observations,we elucidate the progression of S.aureus infection in mice.Results:The results indicate that the infection process in mice can be divided into at least two stages:early infection(1–3 days post-i nfection)and late infection(5–7 days post-i nfection).During the early stage of infection,notable symptoms such as erythema and abundant exudate at the infection site were observed.Histological examination revealed infiltration of numerous neutrophils and bacterial clusters,accompanied by elevated levels of cytokines(IL-6,IL-10).There was a decrease in microbial alpha diversity within the microenvironment(Shannon,Faith's PD,Chao1,Observed species,Simpson,Pielou's E).In contrast,during the late stage of infection,a reduction or even absence of exudate was observed at the infected site,accompanied by the formation of scabs.Additionally,there was evidence of fibroblast proliferation and neovascularization.The levels of cytokines and microbial composition gradually returned to a healthy state.Conclusion:This study reveals synchrony between microbial composition and histological/immunological changes during S.aureus-i nduced SSTIs.

Antimicrobial and synergistic effects of lemongrass and geranium essential oils against Streptococcus mutans,Staphylococcus aureus,and Candida spp.

BACKGROUND The oral cavity harbors more than 700 species of bacteria,which play crucial roles in the development of various oral diseases including caries,endodontic infection,periodontal infection,and diverse oral diseases.AIM To investigate the antimicrobial action of Cymbopogon Schoenanthus and Pelargonium graveolens essential oils against Streptococcus mutans,Staphylococcus aureus,Candida albicans,Ca.dubliniensis,and Ca.krusei.METHODS Minimum microbicidal concentration was determined following Clinical and Laboratory Standards Institute documents.The synergistic antimicrobial activity was evaluated using the Broth microdilution checkerboard method,and the antibiofilm activity was evaluated with the 3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide assay.Data were analyzed by one-way analysis of variance followed by the Tukey post-hoc test(P≤0.05).RESULTS C.schoenanthus and P.graveolens essential oils were as effective as 0.12%chlorhexidine against S.mutans and St.aureus monotypic biofilms after 24 h.After 24 h P.graveolens essential oil at 0.25%was more effective than the nystatin group,and C.schoenanthus essential oil at 0.25%was as effective as the nystatin group.CONCLUSION C.schoenanthus and P.graveolens essential oils are effective against S.mutans,St.aureus,Ca.albicans,Ca.dubliniensis,and Ca.krusei at different concentrations after 5 min and 24 h.

金黄色葡萄球菌(Staphylococcus aureus)液体增菌培养基的优化

为研发一种金黄色葡萄球菌(Staphylococcus aureus)选择性增菌液,选用针对革兰氏阴性菌及非葡萄球菌属菌株具有选择抑制作用的7.5%氯化钠肉汤作为基础培养基,探索氨基酸、丙酮酸钠、甘露醇对金黄色葡萄球菌的促生长能力,通过正交试验确定培养基的最优配方,并使用优化后的培养基与原始培养基作用于来源不同的四株金黄色葡萄球菌标准菌株,对其增菌效果和抑制大肠杆菌(Escherichia coli)的效果进行对比。结果表明,最佳培养基配方为在基础培养基上添加L-丙氨酸1.0 g/L、甘露醇6.0 g/L、丙酮酸钠1.2 g/L。菌株在优化后培养基上增菌浊度及转接至Baird-Parker的菌落数上均有促进效果,最终菌株的OD550 nm值有0.28~0.34的增长,转接Baird-Parker后的菌落数也有10~100倍的增长,且在促进目标菌生长的同时对大肠杆菌的抑制性也没有受到影响,表明该增菌培养基选择性良好。

Antibiotic resistance and molecular typing of clinical Staphylococcus aureus isolates from Malaysian military hospital

Objective:To determine the antibiotic resistance profile(ARP)of Staphylococcus(S.)aureus isolates and molecular typing of the methicillin-resistant S.aureus(MRSA)isolates from Tuanku Mizan Armed Forces Hospital(TMAFH),Kuala Lumpur.Methods:The ARP and presence of the pvl gene were determined for 209 S.aureus isolates from clinical specimens.Of these,123 were methicillin-susceptible S.aureus(MSSA)isolates and 86 were MRSA isolates.All MRSA isolates were characterized using SCCmec typing and spa typing.Descriptive analysis was performed to compare the demographic data with the phenotypic and genotypic variables of the S.aureus isolates.Results:No vancomycin-intermediate and-resistant S.aureus(VISA and VRSA,respectively)were detected among the study isolates.The MSSA isolates showed low resistance rates to all tested antibiotics,were commonly invasive(28/42,66.7%),and mostly harboured pvl(35/42,83.3%).Meanwhile,MRSA isolates showed high resistance to penicillin(86/86,100%),ampicillin(86/86,100%),sulbactam/ampicillin(86/86,100%),cefuroxime(81/86,94.19%),cefoperazone(76/86,88.37%),azithromycin(56/86,65.12%),and erythromycin(54/86,62.79%).The majority of MRSA isolates were of SCCmec type IVh(65/86,75.58%),spa type t032(55/85,63.95%),and grouped into spaCC-t022(66/85,77.65%).The t032 type was found to be associated with resistance traits to azithromycin and erythromycin(P<0.05).We also found several spa types that are typically associated with hospital-,community-,and livestock-associated MRSA co-existing in our MRSA population.Conclusions:This study reflected the consistent absence of VISA and VRSA and corroborated the clonal shifting of MRSA isolates in the Malaysian MRSA isolates.

生物胺降解菌Staphylococcus xylosus JCM 2418的特性研究及应用

从鱼露中筛选获得一株具有生物胺降解能力的木糖葡萄球菌——Staphylococcus xylosus JCM 2418,对其安全性、发酵性能进行评价同时对生物胺降解相关酶展开分析,并将其接种至发酵食品中进行应用,监测发酵食品生物胺降解率以及风味的变化情况。结果表明,S.xylosus JCM 2418表现出弱耐药性,不具有溶血性,不产生生物膜;具有良好的耐盐性、蛋白酶和脂肪酶活性;生物胺降解相关酶为细胞膜上的胺氧化酶;应用在发酵食品中,可以有效控制生物胺的积累,同时改善发酵产品的风味,为提升发酵产品品质提供优良菌种。

Characterization of genetic humanized mice with transgenic HLA DP401 or DRA but deficient in endogenous murine MHC classⅡgenes upon Staphylococcus aureus pneumonia

Background:Staphylococcus aureus can cause serious infections by secreting many superantigen exotoxins in“carrier”or“pathogenic”states.HLA DQ and HLA DR humanized mice have been used as a small animal model to study the role of two molecules during S.aureus infection.However,the contribution of HLA DP to S.aureus infection is unknown yet.Methods:In this study,we have produced HLA DP401 and HLA DRA0101 humanized mice by microinjection of C57BL/6J zygotes.Neo-floxed IAβ+/-mice were crossbred with Ella-Cre and further crossbred with HLA DP401 or HLA-DRA0101 humanized mice.After several rounds of traditional crossbreeding,we finally obtained HLA DP401-IAβ-/-and HLA DRA-IAβ-/-humanized mice,in which human DP401 or DRA0101 molecule was introduced into IAβ-/-mice deficient in endogenous murine MHC classⅡmolecules.A transnasal infection murine model of S.aureus pneumonia was induced in the humanized mice by administering 2×108CFU of S.aureus Newman dropwise into the nasal cavity.The immune responses and histopathology changes were further assessed in lungs in these infected mice.Results:We evaluated the local and systemic effects of S.aureus delivered intranasally in HLA DP401-IAβ-/-and HLA DRA-IAβ-/-transgenic mice.S.aureus Newman infection significantly increased the m RNA level of IL 12p40 in lungs in humanized mice.An increase in IFN-γand IL-6 protein was observed in HLA DRA-IAβ-/-mice.We observed a declining trend in the percentage of F4/80+macrophages in lungs in HLA DP401-IAβ-/-mice and a decreasing ratio of CD4+to CD8+T cells in lungs in IAβ-/-mice and HLA DP401-IAβ-/-mice.A decreasing ratio of Vβ3+to Vβ8+T cells was also found in the lymph node of IAβ-/-mice and HLA DP401-IAβ-/-mice.S.aureus Newman infection resulted in a weaker pathological injury in lungs in IAβ-/-genetic background mice.Conclusion:These humanized mice will be an invaluable mouse model to resolve the pathological mechanism of S.aureus pneumonia and study what role DP molecule plays in S.aureus infection.

Healthcare-associated Staphylococcus aureus infections in children in Turkey:A six-year retrospective,single-center study

Objective:To describe clinical and epidemiological characteristics,antimicrobial susceptibility and mortality-associated factors of healthcare-associated infections(HCAIs)caused by Staphylococcus(S.)aureus in children.Methods:We conducted a retrospective,single-centre study of pediatric HCAIs caused by S.aureus from a tertiary care hospital in Turkey between February 2014 and December 2019.The clinical and epidemiological characteristics and antimicrobial susceptibility of the methicillin-susceptible and methicillin-resistant S.aureus(MSSA and MRSA)isolates was evaluated.Results:A total of 310 pediatric patients were examined.Overall,225(72.6%)isolates were MSSA and 85(27.4%)were MRSA.All S.aureus isolates were susceptible to teicoplanin,vancomycin,linezolid,tigecycline,mupirocin,and daptomycin.Penicillin resistance rates were high(89.0%),while fosfomycin,gentamicin,and clindamycin resistance rates were low(1.3%,1.0%,and 2.3%,respectively).Except susceptibility to fosfomycin,which was significantly lower in 2014 compared to 2018 and 2019,no significant difference was found in the antimicrobial susceptibility of S.aureus isolates between the years.Baseline characteristics and mortality rate were similar comparing MRSA and MSSA causing HCAIs.The mortality rate of HCAIs caused by S.aureus was 6.5%(20 patients).Malignancy was an independent risk factor associated with mortality in the multivariate analysis(OR 5.446,95%CI 1.573-18.849).Conclusions:Our findings demonstrate that MSSA remained the most causative agent of HCAIs caused by S.aureus.The mortality rate was 6.5%,the antibiotic resistance rate was quite high for penicillin and diagnosis of malignancy was the main risk factor for increasing mortality in children.These findings could help improve the management of HCAIs caused by S.aureus in children.

Discovery of Kaempferol,a Novel ADAM10 Inhibitor,as a Potential Treatment for Staphylococcus aureus Infection

Host-directed therapy(HDT)is an emerging novel approach for treating multidrug-resistant Staphylococcus aureus(S.aureus)infection.Functioning as the indispensable specific cellular receptor for a-toxin(Hla),a-disintegrin and metalloproteinase 10(ADAM10)is exploited to accelerate S.aureus infection through diverse mechanisms.The extraordinary contribution of ADAM10 to S.aureus pathogenesis renders it an attractive HDT target for combating S.aureus infection.Our study is the first to demonstrate the indispensable role of ADAM10 in S.aureus-induced necroptosis,and it enhances our knowledge of the role of ADAM10 in S.aureus infection.Using a fluorogenic substrate assay,we further identified kaempferol as a potent ADAM10 inhibitor that effectively protected mice from S.aureus infection by suppressing Hla-mediated barrier disruption and necroptosis.Collectively,our work presents a novel hostdirected therapeutic strategy for using the promising candidate kaempferol to treat S.aureus infection and other diseases relevant to the disordered upregulation of ADAM10.

Two cases of refractory methicillin-susceptible staphylococcus aureus endocarditis responsive to ertapenem

Persistent methicillin-sensitive staphylococcus aureus(MSSA)bacteremia is usually defined as persistent bacteremia despite 7 days of appropriate antibiotic therapy.While nafcillin,cefazolin,or oxacillin are excellent antimicrobial options,persistent MSSA is a commonly encountered phenomenon in clinical practice for which further guidelines on appropriate management are necessitated.Here we highlight two cases of MSSA bacteremia requiring salvage therapy with ertapenem.

Subacute osteomyelitis due to Staphylococcus caprae in a teenager:A case report and review of the literature

BACKGROUND Staphylococcus caprae(S.caprae)is a human commensal bacterium which can be detected in the nose,nails,and skin.It can be responsible for heterogeneous infections such as bacteremia,endocarditis,pneumonia,acute otitis externa,peritonitis,and urinary tract infections.Bone and joint infections due to S.caprae have also been reported,but most of them resulted from the infection of orthopedic devices,especially joint prostheses and internal osteosynthesis devices.Rare cases of primary osteoarticular infections caused by S.caprae have been described,including osteitis,arthritis,or spondylodiscitis.CASE SUMMARY We report an unusual case of subacute osteomyelitis in a toe phalanx caused by S.caprae in a 14.5-year-old girl.CONCLUSION Subacute S.caprae osteomyelitis is a little-known and probably underestimated community-acquired infectious disease.This microorganism’s pathogenicity should be seen as more than a classic nosocomial orthopedic device infection.

Neonatal methicillin-resistant Staphylococcus aureus pneumonia-related recurrent fatal pyopneumothorax: A case report and review of literature

BACKGROUND Although neonatal Staphylococcus aureus pneumonia is common and usually curable,it can also be refractory and life-threatening.Herein,we report a case of severe neonatal community-acquired methicillin-resistant Staphylococcus aureus(CA-MRSA)necrotizing pneumonia with bilateral recurrent pyopneumothorax,respiratory failure,heart failure,and cardiac arrest.We hope our report will add to the understanding of this disease.CASE SUMMARY An 18-d-old boy presented with cough for five days,fever for three days,and dyspnea for two days.Preadmission chest radiograph revealed high-density shadows in both lungs.On admission,his oxygen saturation fluctuated around 90%under synchronized intermittent mandatory ventilation.He was unconscious,with dyspnea,weak heart sounds and hepatomegaly.Moist crackles were present throughout his left lung,while the breath sounds in the right lung were decreased.After high-frequency oscillatory ventilation,empiric antimicrobials(meropenem and vancomycin),improved circulation,and right pleural cavity drainage for right pneumothorax(approximately 90%compression),his oxygen saturation level stayed above 95%,and recruitment of the right lung was observed.His condition did not deteriorate until the 5th day of hospitalization(DOH 5).On the morning of DOH 5,his oxygen saturation decreased.Subsequent chest radiograph showed bilateral pneumothorax with nearly 100%compression of the left lung.Desaturation was not relieved after urgent left pleural cavity drainage,and cardiac arrest occurred soon thereafter.Although his spontaneous heartbeat returned through emergency resuscitation and salvage antibacterial therapy(linezolid and levofloxacin)was administered given the detection and antimicrobial susceptibility of MRSA,he showed no improvement,with recurrent pyopneumothorax and continued drainage of purulent fluid and necrotic lung tissue fragments from the pleural cavity.Eventually,his parents refused extracorporeal membrane oxygenation(ECMO)and gave up all the treatments,and the newborn passed away soon after withdrawal on DOH 13.CONCLUSION Neonatal MRSA pneumonia can be refractory and lethal,especially in cases where necrotizing pneumonia leads to extensive lung necrosis and recurrent pneumothorax.Despite treatment with linezolid and other medical measures,it may still be ineffective.Currently,ECMO has been a remedial therapy,but if the lung tissue is too severely eroded to be repaired,it may be useless unless the infection can be controlled and lung transplantation can be performed.Regardless of whether ECMO is initiated,the key to successful treatment is to achieve control over the pneumonia caused by MRSA as soon as possible and to reverse lung injury as much as possible.

Investigation on the Epidemiology and Pathogenesis Characteristics of Staphylococcus pseudintermedius-Associated Veterinary Hospital Infections

A retrospective analysis of the diagnostic laboratory submissions from 2016 to 2020 was performed to assess the antibiotic resistance of Staphylococcus pseudintermedius and determine locations in the hospital which might be acting as environmental source(s). Previous studies have identified a significant increase in infections with S. pseudintermedius. Samples were taken from the hospital environment by swabbing areas in the intensive care unit and anesthesia preparation room and bacterial species identified. Isolates obtained from patients were then examined regarding the ability to form biofilm, an important phenotype on hospital-related infection. In addition, veterinary hospital associated strains of S. pseudintermedius were used to determine the bactericidal effect of the used disinfectant, applying the hospital current protocol, by comparing the efficacy against S. pseudintermediius and a strain of Staphylococcus aureus from a dog. The isolates identified were resistant to commonly used antibiotics such as enrofloxacin and cephalosporins, and 45% percent of those were methicillin resistant. The environmental survey in the hospital identified S. pseudintermedius in the pre-anesthesia area, although the isolate was killed by the current used disinfection protocol. A few disease associated bacteria were evaluated for biofilm formation in comparison to a dog isolate of Staphylococcus aureus, demonstrating strong ability to form biofilms.

Therapeutic Effect of Daphnetin on Mastitis Induced by Staphylococcus aureus in Mice

[Objectives]To observe the effects of daphnetin on mastitis induced by Staphylococcus aureus in mice.[Methods]18 postpartum ICR female mice were used to establish mastitis animal model,and were randomly divided into three groups(A,B,and C)with 6 mice in each group.Group A:blank control group;group B:S.Aureus model group;group C:S.Aureus model+daphnetin group.The experimental groups were injected 1 mL of 1.0×104 CFU/100μL of S.aureus of along the nipple catheter.The suspension was placed in the 3 rd and 4 th pairs of mammary glands,and the control group was injected with the same dose of normal saline.On the second day after infection,the rats in group A,B and C were given drugs by gavage,while the rats in group A and B were given normal saline and the rats in group C were given daphnetin once a day for 6 consecutive days.Blood samples were collected from living eyeballs,and blood cells were analyzed by automatic flow cytometer after anticoagulation.[Results]The NLR and Systemie Immune Inflammati-on Index(SII)in the blood of mastitis mice induced by S.aureus were significantly higher than those in the control group(P<0.01),suggesting that neutrophil to lymphocyte ratio(NLR)and SII can be used as diagnostic indicators of mastitis,and the levels of NLR and SII decreased significantly after daphnetin intervention.[Conclusions]NLR and SII showed high levels in mastitis mice,which are valuable for the diagnosis of mastitis and the evaluation of its prognosis.After the intervention of daphnetin,both of them decreased significantly,indicating that daphnetin has a good prognosis trend in mastitis mice induced by S.aureus.

高产硝酸盐还原酶Staphylococcus simulans ZSJ6的复合诱变选育及其酶学性质研究

硝酸盐还原酶可以将天然肉制品中的硝酸盐还原为亚硝酸盐,避免了直接添加亚硝酸盐导致其含量骤增,降低产生亚硝胺的概率,对天然肉制品的品质和安全非常重要。以腊肠中筛选出的模仿葡萄球菌(Staphylococcus simulans D14)为出发菌株,探究了单一诱变条件包括紫外、微波、氯化锂诱变,以及紫外-微波-氯化锂联合诱变的两种复合诱变方式对菌株的不同影响,以期获得硝酸盐还原酶高产菌株,并通过摇瓶发酵初步探究其酶学性质,以期为天然肉制品的发酵剂提供菌株选择。确定了紫外、微波和氯化锂诱变的最佳条件:紫外照射60 s,微波辐照80 s,氯化锂浓度1.5%。筛选出诱变菌株Staphylococcus simulans ZSJ6,菌株酶活力可达603.29 U/mg蛋白,是出发菌株酶活力的3.59倍,且突变菌株连续传代8次后,其酶活力并无显著变化(P>0.05),表明其遗传稳定性较好。酶学性质结果显示,其最适作用温度为30℃,最适作用pH为7.5,且稳定性良好,在pH 7.5下孵育2 h,酶活力仍保留90%以上。Mg^(2+)、Ca^(2+)、K^+均能促进酶活力,其中Ca^(2+)对酶活力的促进作用最大,相对于空白组酶活力提升了1.63倍。Cu^(2+)、Fe^(2+)、Hg^(2+)、Mn^(2+)均能抑制酶活,其中Cu^(2+)和Hg^(2+)对酶活力的抑制作用最大,酶活力均被抑制到30%以下。研究结果为天然肉制品中硝酸盐的转化,以及生产初期使用亚硝酸盐带来的亚硝酸盐浓度过高等问题提供了解决思路,具有研究价值和应用潜力。