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。

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.

MRSA血流感染患者万古霉素相关肾毒性预测模型构建

目的构建耐甲氧西林金黄色葡萄球菌(MRSA)血流感染患者万古霉素相关肾毒性预测模型。方法回顾性分析2019年1月至2023年1月天津医科大学总医院收治的128例接受万古霉素治疗的MRSA血流感染患者临床资料。其中男66例,女62例;年龄(61.47±10.25)岁。根据患者是否发生万古霉素相关急性肾损伤(AKI)分为AKI组(32例)和非AKI组(96例),比较两组患者性别、年龄、体质量指数(BMI)、休克、白细胞计数(WBC)、降钙素原、超敏C反应蛋白(hs-CRP)、序贯器官功能衰竭评估(SOFA)评分、急性生理学与慢性健康状况评分系统Ⅱ(APACHEⅡ)评分、合并基础病(糖尿病、高血压、冠心病)、血肌酐、使用非甾体抗炎药、使用氨基糖苷类药物、使用血管活性药物、使用肾毒性药物数量、肾小球率滤过率(GFR)、治疗剂量、给药间隔、治疗时间、累积剂量、万古霉素曲线下面积(AUC)等资料。采用logistic回归方程分析MRSA血流感染患者万古霉素相关肾毒性的危险因素。基于危险因素构建万古霉素相关肾毒性的风险列线图模型,并对构建的模型进行验证及预测效能评估。采用独立样本t检验、Mann-Whitney U检验、χ^(2)检验、Hosmer-Lemeshow检验。结果AKI组年龄、血肌酐水平、万古霉素AUC及使用肾毒性药物数量≥2个、GFR≤60 ml/min占比均高于非AKI组(均P<0.05)。logistic回归分析结果显示,年龄≥60岁、血肌酐≥95.42µmol/L、使用肾毒性药物数量≥2个、GFR≤60 ml/min、万古霉素AUC≥30 g/L均是影响接受万古霉素治疗的MRSA血流感染患者发生AKI的独立危险因素(均P<0.05)。Hosmer-Lemeshow拟合优度检验结果显示,列线图模型预测接受万古霉素治疗的MRSA血流感染患者发生AKI风险的一致性良好(χ^(2)=3.571,P=0.672)。Bootstrap法内部验证结果显示,列线图预测模型C指数为0.785(95%CI 0.678~0.889),表明该模型具有较好的区分度。受试者操作特征曲线(ROC)结果显示,列线图风险模型预测接受万古霉素治疗的MRSA血流感染患者发生AKI的AUC(95%CI)、灵敏度、特异度分别为0.859(0.618~0.979)、94.50%、78.30%(均P<0.001)。结论年龄≥60岁、血肌酐≥95.42µmol/L、使用肾毒性药物数量≥2个、GFR≤60 ml/min、万古霉素AUC≥30 g/L均是影响接受万古霉素治疗的MRSA血流感染患者发生AKI的独立危险因素。基于上述危险因素构建的风险列线图模型对接受万古霉素治疗的MRSA血流感染患者发生AKI具有较高的预测价值。

Prevalence and antibiogram study of Salmonella and Staphylococcus aureus in poultry meat

Objective:To evaluate the presence and antibiogram pattern of Salmonella and Staphylococcus aureus(S.aureus)in retail poultry meat products.Methods:Foodborne pathogens(Salmonella and S.aureus)were isolated from poultry meat and confirmed with the help of biochemical and immunological test.Antibiogram of the isolates were examined by following CLS1 methods.Results:A total number of 209 poultry meat samples were collected and studied in this study.Out of which,5.26%were found contaminated with Salmonella while 18.18%were found contaminated with S.aureus.All the Salmonella and S.aureus isolates were found resistant to at least one antibiotic.About 72.72%of the Salmonella isolates showed resistance to tetracycline,while S.aureus isolates were also found highly resistant to tetracycline equal to 44.73%.One of the Salmonella isolates showed multi-drug resistance to almost six antibiotics out of nine antibiotics used in the study.Multidrug resistant S.aureus isolates were also found in the study.Conclusions:The study confirmed the presence of Salmonella and S.aureus in retail poultry meat.It is a potential threat to consumer health.To reduce the risk of contamination,good hygiene practices are necessary from processing to storage.

呼吸道与非呼吸道标本分离MRSA临床株耐药性比较及其分子流行病学特征

目的:探讨呼吸道与非呼吸道标本分离耐甲氧西林金黄色葡萄球菌(MRSA)的耐药性、分子分型和生物膜形成能力的差异。方法:选取住院患者送检标本中分离出的100株MRSA,其中50株MRSA分离自呼吸道标本,50株MRSA分离自非呼吸道标本。对100株MRSA进行14种抗菌药物的体外药敏试验,采用多位点序列分型(MLST)和金黄色葡萄球菌A蛋白(Spa)分型方法进行分子分型,结晶紫染色实验检测MRSA菌株生物膜形成能力。结果:体外药敏试验,100株MRSA对青霉素、红霉素、克林霉素、左氧氟沙星、环丙沙星、莫西沙星和四环素的总体耐药率较高,均大于60.0%,对复方新诺明耐药率仅为9.0%,且所有菌株均对万古霉素、利奈唑胺、替加环素和奎奴普丁/达福普汀敏感。呼吸道标本分离的MRSA对莫西沙星、左氧氟沙星、环丙沙星、四环素和庆大霉素的耐药率明显高于非呼吸道标本分离株(P<0.05)。100株MRSA中共检出17种基因型,其中优势型别为ST5-t2460型(26.0%)、ST239-t030型(23.0%)和ST59-t437型(20.0%)。呼吸道标本分离MRSA中优势型别为ST5-t2460型(20.0%)和ST239-t030型(13.0%),其次为ST59-t437型(7.0%);非呼吸道标本分离MRSA中共检出13种基因型,优势型别为ST59-t437型(13.0%)和ST239-t030型(10.0%)。100株MRSA全部为产膜菌株,强产膜菌株、中产膜菌株和弱产膜菌株比例分别为2.0%(2/100)、24.0%(24/100)和74.0%(74/100)。ST59-t437型克隆株整体产膜能力较强,60.0%(12/20)为中产膜株和强产膜株。结论:呼吸道标本分离MRSA菌株整体耐药率明显高于非呼吸道标本分离MRSA株。ST59-t437基因型和ST239-t030基因型为2类标本共有优势克隆株,ST59-t437型菌株呈现较强的生物膜形成能力,而ST239-t030型菌株整体耐药性最强。

Detection of Staphylococcus aureus in Dairy Products by Polymerase Chain Reaction Assay

A polymerase chain reaction （PCR） assay was employed for direct detection of Staphylococcus aureus without enrichment in dairy products. A solvent extraction procedure was successfully modified for the extraction of Staphylococcus aureus DNA from artificially contaminated whole milk, skim milk, and cheese. A primer targeting the thermostable nuclease gene （nuc） was used in the PCR. A DNA fragment of 279 bp was amplified. The PCR product was confirmed by DNA sequencing. In this study, the PCR, GB-4789.10-94, Perifilm RSA.Count Plate, and Baird-Parker ＋ RPF Agar were compared. The sensitivity of the PCR was 10 CFU mL^-1 of whole milk, skim milk, and 55 CFU g^-1 of cheese. The developed methodology allowed for detection of Staphylococcus aureus in dairy products in less than 6 h. The time taken for the development of this PCR assay was 12-24 h, less than the time taken by the general PCR assay using the enrichment method, and the coincidence rate of this developed PCR was 94.3%, the sensitivity was 100%. It was a rapid, sensitive, and effective method for PCR to detect Staphylococcus aureus in milk and milk products.

Antimicrobial activity and synergism of Sami-Hyanglyun-Hwan with ciprofloxacin against methicillin-resistant Staphylococcus aureus

Objective: To investigate the antibacterial activity of SHHextracted with either water or ethanol against methicillin-resistant Staphylococcus aureus(MRSA) and combinatory antimicrobial effect with ciprofloxacin(CIP) by time kill assay and checkerboard dilution test. Methods: The antibacterial activity determined by broth dilution method indicated that the antibacterial activity of Sami-Hyanglyun-Hwan(SHH) water extract(SHHW) and SHH ethanol extract(SHHE) ranged from 250 to 2000 μg/m L and 125 to 1000 μg/m L against MRSA, respectively. Results: In the checkerboard method, the combinations of SHHE with CIP had a partial synergistic or synergistic effect against MRSA. The time-kill curves showed that a combined SHHE and CIP treatment reduced the bacterial counts dramatically after 24 h. Conclusions: The present study demonstrates the therapeutic ability of SHHE against MRSA infections.

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.

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.

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.

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.

水飞蓟素对S.aureus ATCC25923生物膜及其毒力因子的影响

目的:探究水飞蓟素对S.aureus ATCC25923生物膜及其毒力因子的影响。方法:采用结晶紫染色法检测水飞蓟素对S.aureus ATCC25923生物膜形成的抑制及清除作用,MTT染色法探究水飞蓟素对其生物膜代谢的影响,冻干血浆和无菌脱纤维羊血探究水飞蓟素对其凝固酶表达和溶血活性的影响,同时用光学显微镜观察不同浓度水飞蓟素对其生物膜影响及傅里叶红外分析细菌成分变化。结果:水飞蓟素对S.aureus ATCC25923的最小抑菌质量浓度(MIC)为0.5 mg/mL,MIC浓度下的水飞蓟素对S.aureus ATCC25923生物膜的抑制率达到90%,清除率达到89.2%,且低剂量的水飞蓟素能够显著抑制其溶血活性和凝固酶的表达。结论:水飞蓟素对金黄色葡萄球菌的生物膜形成具有很好的抑制以及清除作用,同时能够显著抑制其毒力因子的表达。

Surface-engineered liposomes for dual-drug delivery targeting strategy against methicillin-resistant Staphylococcus aureus(MRSA)

This study focused on the encapsulation of vancomycin(VAN) into liposomes coated with a red blood cell membrane with a targeting ligand, daptomycin–polyethylene glycol–1,2-distearoyl-sn-glycero-3-phosphoethanolamine, formed by conjugation of DAPT and Nhydroxysuccinimidyl-polyethylene glycol-1,2-distearoyl-sn-glycero-3-phosphoethanolamine.This formulation is capable of providing controlled and targeted drug delivery to the bacterial cytoplasm. We performed MALDI-TOF, NMR and FTIR analyses to confirm the conjugation of the targeting ligand via the formation of amide bonds. Approximately 45% of VAN could be loaded into the aqueous cores, whereas 90% DAPT was detected using UV–vis spectrophotometry. In comparison to free drugs, the formulations controlled the release of drugs for > 72 h. Additionally, as demonstrated using CLSM and flow cytometry, the resulting formulation was capable of evading detection by macrophage cells. In comparison to free drugs, red blood cell membrane–DAPT–VAN liposomes, DAPT liposomes, and VAN liposomes reduced the MIC and significantly increased bacterial permeability, resulting in > 80% bacterial death within 4 h. Cytotoxicity tests were performed in vitro and in vivo on mammalian cells,in addition to hemolytic activity tests in human erythrocytes, wherein drugs loaded into the liposomes and RBCDVL exhibited low toxicity. Thus, the findings of this study provide insight about a dual antibiotic targeting strategy that utilizes liposomes and red blood cell membranes to deliver targeted drugs against MRSA.

Detection of Pathogenic Bacteria <i>Staphylococcus aureus</i>and <i>Salmonella</i>sp. from Raw Milk Samples of Different Cities of Pakistan

Food-borne diseases are the main public health problem throughout the world. Milk is important component of human diet including fats, proteins, vitamins and minerals. It is a best source of calcium and phosphorus. Different types of pathogenic bacteria like S. aureus and Salmonella enter in milk and then multiply, after multiplication they become active in causing diseases. These bacteria create serious problems for human health. This study aimed to isolate and identify pathogenic bacteria Staphylococcus aureus and Salmonella from raw milk samples of different cities of Pakistan. Primary screening of raw milk samples was done on the basis of morphological, cultural and biochemical techniques. The final identification was made using 16SrRNA sequence analysis. A total of 200 raw milk samples were collected from different cities of Pakistan. Selective medium xylose lysine deoxycholate agar (XLD) and Mannitol salt agar were used for the identification of Salmonella sp. and S. aureus. Staphylococcus aureus produced yellow colonies with yellow zones on Mannitol salt agar. Staphylococcus aureus exhibited gram-positive character with purple coloration and it was detected as cocci-shaped. Biochemically 91 (45%) samples enhibited Catalase, Coagulase, DNase, Urease, Citrate, fermentation tests positive and indole, oxidase and H2S tests negative with nonmotile character, indicating the presence of Staphylococcus aureus. Salmonella sp. was detected as gram negative rods with pink coloration on gram staining. Biochemically 87 (43%) samples revealed catalase, citrate, H2S and fermentation tests positive while oxidase, DNase, Indole and urease tests negative, indicating the presence of Salmonella sp. in these samples. Of the 200 samples tested, 43% were positive for Salmonella, while 45% samples were contaminated with S. aureus. The 16SrRNA sequence analysis confirmed the results of biochemical and cultural characterization by depicting 99% identity of samples with S. aureus and 98% identity with Salmonella spp. The occurrence of high percentage of these pathogenic bacteria in raw milk may be linked to its contamination at the time of collection, processing, strorage and distribution. This quantitative data could be utilized to better establish the appropriate levels of protection for raw milk, dairy products and processing technologies.

基于真实世界研究骨髓炎MRSA感染率的Meta分析

目的:通过Meta分析研究骨髓炎患者中耐甲氧西林金黄色葡萄球菌(MRSA)的感染率。方法:检索PubMed、Web of Science、中国知网、维普、万方和中国生物医学文献数据库(CBM)关于骨髓炎患者MRSA感染率的研究,检索时限为建库至2023年8月。由2位研究人员按照纳入与排除标准对所获文献独立进行筛选、提取,采用纽卡斯尔-渥太华量表评分(NOS)进行文献质量评价。以感染率为结局指标合并数据,采用R(4.3.1)进行Meta分析,并根据骨髓炎类型、患者年龄、研究地区进行亚组分析。结果:共纳入26篇文献,共包含20860名骨髓炎患者。Meta分析结果显示,骨髓炎患者MRSA感染率为0.240(95%CI:0.183~0.297)。亚组分析结果显示,椎体骨髓炎(VO)患者、18~60岁、北美地区骨髓炎患者的MRSA感染率更高。结论:骨髓炎患者中MRSA的感染率较高,需采取有效的预防和控制措施减少MRSA的传播。

Assessment of the inhibitory effects of sodium nitrite, nisin, potassium sorbate, and sodium lactate on Staphylococcus aureus growth and staphylococcal enterotoxin A production in cooked pork sausage using a predictive growth model

This study was conducted to analyze the effects of sodium nitrite,nisin,potassium sorbate,and sodium lactate against Staphylococcus aureus(S.aureus)growth and staphylococcal enterotoxins(SEs)production in cooked pork sausage by inoculating sausage samples containing preservative with an S.aureus strain producing staphylococcal enterotoxin A(SEA)and then storing them at 37℃ for 36 h.Samples were analyzed every 3 h to count the S.aureus colonies and to detect SEA.The modified Gompertz model was used to describe S.aureus growth in the samples under various conditions,and the preservatives with a significant antimicrobial effect were selected.In addition,the antimicrobial effects of the selected preservatives under various concentrations were tested.Results showed that sodium nitrite,nisin,and potassium sorbate had a weak effect against S.aureus growth and had no effect against SEA production,whereas sodium lactate could significantly inhibit S.aureus growth and SEA production.Moreover,the antimicrobial effect of sodium lactate was concentration-dependent,wherein sodium lactate concentration<12 g/kg showed no inhibitory effect,but when the concentration was increased to 24 g/kg,sodium lactate could effectively inhibit S.aureus growth and SEA production,and at 48 g/kg,sodium lactate had a significant inhibitory effect.