原料奶贮存和运输过程中S.aureus的暴露评估

以哈尔滨市地区为例,运用概率评估方法研究原料奶中金黄色葡萄球菌(S.aureus)的暴露程度,进而推断其肠毒素产生的可能性。整个暴露评估模型的建模方法采用概率评估法。模型采用Monte Carlo模拟技术,通过风险分析软件@RISK4.5对榨乳后不同冷却方式、贮存方式、运输方式等可能对乳中S.aureus造成生物性危害的可能性进行了评估。结果表明,个体奶户采用冷水降温方式贮存的牛乳中S.aureus可能引发的安全性风险最大,需严格控制贮存温度和时间,防止S.aureus在原料乳中的迅速生长繁殖及产毒,进而从源头上为乳及其制品的安全生产提供保障。

CpG-ODN对S.aureus诱导的山羊实验性乳腺炎乳腺的保护作用研究

选择同处于泌乳初期的睢宁白山羊6头,于右乳区经过乳导管灌注10μg/kgCpG-ODN,左乳区则灌入等体积的灭菌100μL0.01mol/LpH7.2磷酸盐缓冲液(PBS)作为对照,灌注后第3d按同等剂量进行二次灌注,二次灌注后第2d,分别于左右乳区经乳导管灌注3mL(2×109CFU/mL)金黄色葡萄球菌(S.aureus),于灌注细菌前(0h),灌注后8h,16h,24h,48h和72h分别收集左右乳区乳汁进行检测。临床症状观察显示,乳腺内灌注3mL(2×109CFU/mL)的S.aureus能迅速诱导山羊典型的急性乳腺炎症状。组织学观察显示感染S.aureus后72h乳腺腺泡内仍有嗜中性粒细胞(PMN)浸润,但实验乳区明显减少。乳汁S.aureus数同在感染后24h上升至最高,CpG-ODN能显著降低各个时间点乳汁细菌数。乳汁白细胞介素-6(IL-6)水平同在感染后24h上升至最高,CpG-ODN能显著提高感染后24h乳汁IL-6水平。对照和CpG-ODN处理乳区乳汁肿瘤坏死因子-α(TNF-α)水平分别在感染后24h和16h上升至最高,其中在感染后24h实验乳区比对照下降40.63%(P<0.05)。乳汁N-乙酰-β-D-氨基葡萄糖苷酶(NAGase)水平同在感染后16h达最高(P<0.01),CpG-ODN能显著提高感染后8h乳汁NAGase水平。上述结果表明CpG-ODN可通过提高乳汁IL-6水平、加速并促进乳汁TNF-α的释放,从而减少了乳汁中S.aureus数量,减轻了炎症介质对细胞的损伤,对缩短炎症过程也有一定的作用,实验结果证实了CpG-ODN对S.aureus感染诱发的山羊乳腺炎的乳腺有保护作用。

Effect of Ciprofloxacin on S.aureus and E.coli Growth in Presence of Vitamin C Using Cup Cut Diffusion Method

Ciprofloxacin is a second-generation of fluoroquinolone,broad-spectrum antibiotic with bactericidal activity against Gram-positive and Gram-negative organisms.It is one of the most widely used antibiotics,because of its efficacy,safety,and relatively low cost.Ascorbic acid(vitamin C)is water-soluble monosaccharide antioxidant;it is essentially required by the body for its various biochemical and physiological processes.S.aureus is Gram-positive cocci;widely distributed in the environment,it is a member of the normal flora of the body.S.aureus is not always pathogenic;it is a common cause of skin infections including abscesses,respiratory infections such as sinusitis,and food poisoning.E.coli is Gram-negative bacteria,found in the environment,foods,and intestines.Most E.coli strains are harmless;it is part of the normal microbiota of the gut.However,some serotypes of E.coli cause serious food poisoning in their hosts;it can cause diarrhea,while others cause urinary tract infections,respiratory illness and pneumonia,and other illnesses.Method:Cup cut diffusion method was applied.Experiment I:is carried out to choose the concentration of vitamin C to be used in experiment II.The negative control is normal saline,added in cup in each plate,vitamin C(100 mg/mL,200 mg/mL,400 mg/mL)was added,the volume in each cup was 100μL.Experiment II:Eight groups of treatments were applied.The first is the negative control(1%normal saline),the second group is the positive control of vitamin C(200 mg/mL).The third,fourth and fifth groups are ciprofloxacin with different concentrations(10 mg/mL,20 mg/mL,40 mg/mL);the sixth,seventh and eighth are the combination of vitamin C with each concentration of ciprofloxacin(10 mg/mL,20 mg/mL,40 mg/mL).Each group includes six petri dishes.Bacterial plates were incubated at 37 oC for 24 h and 48 h.Zone of inhibition is measured in mm.Results and conclusion:Ciprofloxacin produces dose dependent increase in zone of inhibition of S.aureus and E.coli growth,after 24 and 48 hours incubation.While vitamin C in the concentration used produced inhibitory effect on the growth of S.aureus and E.coli,after 24 hours incubation,vitamin C effect was not changed after 48 hours incubation.After 24 hours incubation,vitamin C potentiated the effect of ciprofloxacin at low concentration(10 mg/mL);while vitamin C antagonized the effect of ciprofloxacin at higher concentrations(20 and 40 mg/mL)on S.aureus growth.In the same time,ciprofloxacin antagonized the inhibitory effect of vitamin C on S.aureus growth.After 48 hours incubation,S.aureus produced resistance against ciprofloxacin alone,and that combined with vitamin C compared to zone of inhibition after 24 hours.Ciprofloxacin produced dose dependent inhibition of E.coli growth after incubation for 24 and 48 hours.Vitamin C potentiated the inhibitory effect induced by ciprofloxacin(additive effect).The inhibitory effect of ciprofloxacin,vitamin C and the combination was not changed after 48 hours compared to 24 hours.

Evaluation of the Antibacterial and Antifungal Capacity of Nanoemulsions Loaded with Synthetic Chalcone Derivatives Di-Benzyl Cinnamaldehyde and Benzyl 4-Aminochalcone

With the increase in antimicrobial resistance,it has become necessary to explore alternative approaches for combating and preventing diseases.DB-cinnamaldehyde(CNM)and Benzyl4-amino(B4AM)are bioactive compounds derived from chalcones but with restricted solubility in aqueous media.Nanoemulsions can enhance the solubility of compounds and can be a promising alternative in the development of novel antimicrobials,with reduced side effects and prolonged release.The objective of this study was to evaluate the stability of oil-in-water nanoemulsions loaded with two distinct types of chalcones at two different dosages,to propose a stable formulation with antimicrobial properties.Results showed that nanoemulsions presented high encapsulation efficiency,low polydispersity index(PDI)and particle size below 200 nm,indicating that emulsification was a suitable method for nanoemulsion preparation.Nanoemulsions with higher dosages exhibited significant antimicrobial effects when compared to free chalcones and positive controls.Notably,B4AM nanoemulsions at higher dosages showed expressive activity against Salmonella minnesota,with a 420%greater inhibitory response compared to the free form and showing equivalence to the positive control.CNM nanoemulsions showed excellent inhibitory activity at the highest dosage,equivalent to the positive control against S.minnesota and Staphylococcus aureus.The greater number of conjugated bonds in CNM increased the antimicrobial activity in comparison with B4AM,and the formation of nanometric domains enhanced the bioavailability,being a promising alternative for antimicrobial applications.

黄鳝骨基碳量子点的制备及抑菌性能研究

本研究以黄鳝加工副产物鱼骨为碳源,通过一步水热法绿色合成黄鳝骨基碳量子点(Mab-CQDs),分析骨粉添加量、反应温度和时间对荧光强度的影响,优化Mab-CQDs的制备工艺。采用透射电子显微镜(TEM)、傅里叶红外光谱(FT-IR)和X射线衍射(XRD)等表征Mab-CQDs的形貌结构和光学性质,并选取金黄葡萄球菌(Staphylococcus aureus)和大肠杆菌(Escherichia coli)作为受试菌株,探究Mab-CQDs的抗菌性能。优化的Mab-CQDs制备工艺为:黄鳝骨粉与超纯水比例为1∶30、反应温度为180℃、反应时间为8 h,该条件下制备的Mab-CQDs具有良好的荧光性能;TEM成像显示Mab-CQDs为分散良好的类球形结构,粒径范围为2.05 nm~5.94 nm;FT-IR结果表明Mab-CQDs表面含有大量氨基、羧基等极性官能团,具有良好的亲水性;抑菌实验表明Mab-CQDs对S.aureus和E.coli具有良好的抑制效果,最小抑菌质量浓度分别为5 mg/mL和10 mg/mL。本研究制备的Mab-CQDs粒径均匀,水溶性好,荧光性能优良,且具备明显的抑菌性能,可为淡水鱼加工副产物基CQDs的制备及其应用提供理论指导。

Low-Level Antibiotic Resistance among Staphylococcus aureus and Gram-Negative Pathogens from Infected Skin and Soft Tissues in Rural Kenya

Introduction: Bacterial skin and soft tissue infections (SSTIs) are a cause of frequent inpatient and outpatient care visits whose causative agents are associated with a high antimicrobial resistance burden. For insights on antimicrobial susceptibilities in a rural setting, we examined specimens from suspected SSTIs from two public health facilities in Kenya. We additionally assessed antibiotic use, appropriateness of empiric therapy and risk factors for SSTI. Methodology: Between 2021 and 2023, 265 patients at Kisii and Nyamira County Referral hospitals were enrolled. Wound swabs/aspirates were collected and processed following standard microbiological procedures. Identification and antimicrobial susceptibility were performed using the VITEK 2 Compact platform. Demographic, clinical, and microbiological data were analyzed with R Statistical software. Results: S. aureus was isolated in 16.2% (43/265) of patients with a methicillin resistance (MRSA) proportion of 14% (6/43). While 13/15 drugs elicited susceptibilities ranging from 84% - 100%, penicillin (16%) and trimethoprim-sulfamethoxazole [TMP-SXT] (23%) yielded the lowest susceptibilities. Escherichia coli (n = 33), Klebsiella pneumoniae (n = 8), Pseudomonas aeruginosa (n = 8), and Citrobacter species (n = 4) were the most commonly isolated gram-negative species. Gram-negative strains showed high susceptibilities to most of the tested drugs (71% - 100%) with the exception of ampicillin (18%), TMP-SXT (33%), and first and second generation cephalosporins. Conclusions: The low MRSA prevalence and generally high antibiotic susceptibilities for S. aureus and gram-negative bacteria present opportunities for antibiotic stewardship in the study setting. Diminished susceptibilities against penicillin/ampicillin and TMP-SXT accord with prevailing local data and add a layer of evidence for their cautious empiric use.

Insight into microbiologically induced corrosion performance of magnesium in tryptic soy broth with S.aureus and E.coli

In this research,microbiologically induced corrosion(MIC)performance of magnesium in tryptic soy broth with S.aureus or E.coli were systematically explored.The results showed that magnesium in biotic solution presented higher mass loss,thicker degradation product layer and more severe pitting corrosion compared to abiotic solution after 24 h of immersion.Electrochemical measurements including EIS spectra and polarization curve further suggested that the corrosion rate of Mg in biotic solution increased during the early stage owing to the decrease of p H,which was originated from the consumption of glucose and the resulting accumulation of acidic metabolites.However,corrosion rate subsequently decreased because of the reduction of acidic metabolites and production of alkaline compound as well as the corrosion protection provided by the corrosion product and biofilm.Moreover,the corrosion rate of magnesium in high concentration of S.aureus and E.coli solution was larger than that in low concentration of S.aureus and E.coli solution,respectively during the initial stage,but subsequently presented a reverse variation.In addition,more severe corrosion of magnesium was observed in S.aureus solution in comparison with E.coli solution.These results suggested that the MIC performance of magnesium was closely related to the concentration and species of bacteria.

Antibacterial potential of some plants of traditional use in India against pathogenic strains of S.aureus

Objective:To evaluate antibacterial sensitivity of 43 ethnomedicinally important plants belonging to 25 different families from Western Uttar Pradesh,a northern province in India,against hospital isolated pathogenic strains of Staphylococcus aureus(S.aureus).Methods:Methanol(MeOH)and aqueous extracts of plants were subjected to sensitivity test against S.aureus ATCC 25953 and two hospital isolated virulent strains of S.aureus SA1 and SA2 following disc diffusion assay to determine sensitivity and agar dilution method to test minimum inhibition concentration using Mueller-Hinton agar.Results:Potential antibacterial activity was recorded for MeOH extracts against test pathogens,while moderate antibacterial activity was observed in case of aqueous extracts.Out of 43 plant species,39 species were found sensitive to tested strains.Minimum inhibition concentration values of MeOH extracts were demonstrated at low concentration ranging from 15.5 mg/mL up to 45.5 mg/mL compared to aqueous extracts which were observed ranging from 30.0 mg/mL up to 95.0 mg/mL.Conclusions:The present findings strongly support traditional uses of these plants in the treatment of infectious maladies and further urge of phytochemical and pharmacological research to develop safer and cheaper drugs for the benefit of ailing humanity.

Electrochemical Biosensor for Detection of Staphylococcus aureus Based on Nucleic Acid Aptamers

Staphylococcus aureus is a gram-staining positive cocci bacillus baterium and also one of the foodborne pathogens, which is a serious potential hazard to human health and food safety. We constructed an electrochemical biosensor for the detection of S. aureus based on nucleic acid aptamers to achieve highly specific detection of S. aureus. The detection of S. aureus was realized by using Aptamer (Apt) to capture S. aureus, which resulted in a change in the spatial conformation of Apt and a decrease in the electrochemical signal. Under the optimized experimental conditions, the detected electrochemical signals were positively correlated with the concentration of S. aureus with a linear range of 1 × 101 - 1 × 105 CFU/mL, a detection limit of 4.76 CFU/mL, and an experimental recovery of 97.43% - 99.37%. Therefore, we successfully constructed an electrochemical biosensor for the specific detection of S. aureus, which has the advantages of high specificity, sensitive detection and convenient operation.

g-C_3N_4纳米片的制备及光催化抗菌性能研究

采用液相超声法成功地将体相g-C_3N_4剥离为g-C_3N_4纳米片。通过XRD、FT-IR、TEM、BET和瞬态光电流对样品的性质进行表征,并研究g-C_3N_4纳米片光催化杀灭大肠杆菌(E.coli)和金黄色葡萄球菌(S.aureus)的活性。结果表明,将体相g-C_3N_4剥离为g-C_3N_4纳米片并没有改变分子结构,但g-C_3N_4纳米片光催化杀灭E.coli和S.aureus的活性均优于体相gC_3N_4。g-C_3N_4纳米片的超薄二维结构具有大的比表面积,是体相g-C_3N_4的6.97倍,同时有效地促进了光生电子和空穴的分离,两方面的协同作用下,g-C_3N_4纳米片表现出优异的光催化抗菌活性。

Meso-substituted cationic 3-and 4-N-Pyridylporphyrins and their Zn(II)derivatives for antibacterial photodynamic therapy

Photodynamic inactivation of microorganisms known as antibacterial photodynamic therapy(APDT)is one of the most promising and innovative approaches for the destruction of pathogenic microorganisms.Among the photosensitizers(PSs),compounds based on cationic porphyrins/metalloporphyrins are most successfully used to inactivate microorganisms.Series of meso-substituted cationic pyridylporphyrins and metalloporphyrins with various peripheral groups in the third and fourth positions of the pyrrole ring have been synthesized in Armenia.The aim of this work was to determine and test the most e®ective cationic porphyrins and metalloporphyrins with high photoactivity against Gram negative and Gram positive microorganisms.It was shown that the synthesized cationic pyridylporphyrins/metalloporphyrins exhibit a high degree of phototoxicity towards both types of bacteria,including the methicillinresistant S.aureus strain.Zinc complexes of porphyrins are more phototoxic than metal-free porphyrin analogs.The e®ectiveness of these Zn–metalloporphyrins on bacteria is consistent with the level of singlet oxygen generation.It was found that the high antibacterial activity of the studied cationic porphyrins/metalloporphyrins depends on four factors:the presence in the porphyrin macrocycle of a positive charge(+4),a central metal atom(Zn2þÞand hydrophobic peripheral functional groups as well as high values of quantum yields of singlet oxygen.The results indicate that meso-substituted cationic pyridylporphyrins/metalloporphyrins cannd wider application in photoinactivation of bacteria than anionic or neutral PSs usually used in APDT.

Cross Sectional Study of Skin Carriage and Enterotoxigenicity of Staphylococcus aureus among Food Handlers

The prevalence of enterotoxigenic Staphylococcus aureus was investigated among 200 participants working in three different food processing plants in Egypt. Using skin swabs, 75 (38%) of the 200 tested persons were positive for the presence of S. aureus. Of the S. aureus positive persons, 28 (14%) harboured S. aureus produced staphylococcal enterotoxins. The serotypes of these enterotoxins were enterotoxin A (68%), enterotoxin B (36%), enterotoxin C (46%) and enterotoxin D (18%). Some of these isolates produced more than one type of enterotoxins namely AB, AC, BC, BD, ABC and ACD. Analysis of risk factors implicated in skin carriage of S. aureus as age, gender, marital status, education, duration in employment, frequency and method of hand wash and incidence of chronic skin infection revealed insignificant association with staphylococcal skin carriage. The obtained results put forth the risk of food contracting contamination with enterotoxigenic strains of S. aureus owing to skin colonization of S. aureus among food handlers.

Study on Antibacterial Effects of Purple, Yellow and White-skinned Onions

Onion(Allium cepa L.)is a common biennial herb,and contains allicin compounds which can kill harmful microorganism.The antibacterial effects of raw and mature onion juice of purple,yellow and white-skinned onions at different concentrations on Escherichia coli(E.coli)and Staphylococcus aureus(S.aureus)were studied.There were differences among the antibacterial effects of raw and mature onion juice of purple,yellow and white-skinned onions at different concentrations.What was more,the antibacterial effects of raw onion juice were better than those of the mature one.The antibacterial effects of high concentration onion juice were better than those of the low one.The content of the total flavonoids in raw purple onion was higher than that in mature onion,and reached extremely significant levels in 50%,75%and 100%,respectively.Through comparison,it was found that onion juice of purple-skinned had the best suppression effects on S.aureus(gram-positive bacterium)and E.coli(gram-negative bacterium),and gram-positive bacterium had better suppression effects than gram-negative bacterium.It wound provide the basis about bioactive function and antibacterial drugs.

Testing the Association Between TRPM6 rs2274924 Gene, Metabolic Syndrome and Staphylococcus Aureus in Patients With Type 2 Diabetes Mellitus

The TRPM6 gene is associated with multifactorial diseases:diabetes mellitus,obesity,hypertension,components of the metabolic syndrome.The aim of this study is to test the association between TRPM6 rs2274924 gene,metabolic syndrome and S.aureus based on clinical data and biochemical,haematological,microbiological and genetic laboratory investigations in patients with type 2 diabetes mellitus.The TRPM6 gene sequencing was performed by the Advanced NGx assay based on clinical and laboratory data,on 152 subjects from Giurgiu County Emergency Hospital.The results were processed by the graph Pad prism 7 program,VMD.In conclusion,the TRPM6 rs2274924 gene is associated with metabolic syndrome and S.aureus.

Epidemiology and Antibiotic Susceptibility Profile of Methicillin Sensitive Staphylococcus aureus among Livestock and Pet Animals

Staphylococcus aureus is an important zoonotic pathogen that is responsible for a variety of infectious diseases in humans and animals.The present study was designed to check the prevalence and antimicrobial resistance of MSSA from three different animal origins(bovine,caprine and pet).A total of n=450 samples(150 each source)were collected from bovine,caprine and pets.Collected samples were subjected to S.aureus identification by microbiological examination and confirmed S.aureus isolates were put to oxacillin disk diffusion test to declare them MSSA.The MSSA confirmed isolates were subjected to various antibiotics for susceptibility profiling using Kirby Bauer Disk Diffusion test.The present study found higher prevalence of MSSA from caprine origin(goat 83.33%)as compared to pet(cat 69.33%;dog 65.33%)and bovine origin(buffalo 26.66%;cattle 31.66%).The in-vitro findings of current study revealed oxytetracycline and gentamicin presented 100%efficacy against MSSA of all origins while the vancomycin presented>35%,>40%and>65%resistance against MSSA isolated from bovine,caprine and pet origin respectively.However,ciprofloxacin was equally effective(50%)against MSSA from buffalo and cattle while>80%efficacy was noted against MSSA from cat and dogs.Linezolid and amoxicillin+clavulanic acid were 77.78%and 66.67%sensitive to MSSA isolates from caprine milk.The present study found higher prevalence of MSSA from bovine,caprine and pet isolates with diversified pattern of susceptibility of different antibiotics from all sources.

Virulence Markers in Staphylococcus aureus Strains Isolated from Hemodialysis Catheters of Mexican Patients

Methicillin-resistant Staphylococcus aureus is an increasingly important cause of nosocomial bacterial infections worldwide. S. aureus is responsible for several pathologies, including skin infections, endocarditis, meningitis, deep-tissue ulcers, and sepsis. S. aureus biofilm formation on catheters and other medical devices is a major post-operative concern, because biofilms are often the source of persistent and difficult to treat bacterial infections. While catheter-related S. aureus infections have been reported, the strains responsible for these infections have not been genetically characterized. We genetically characterized S. aureus strains isolated from hemodialysis catheters in Mexican patients. The frequency of 35 genes coding for adhesins, toxins, and other virulence-associated products in the 55 isolated S. aureus strains was determined using PCR, while real-time PCR was used to examine the level of gene expression. Of the 55 S. aureus strains isolated from 109 patients, 45 (81.8%) were determined to be methicillin-resistant. The icaA, rbf, sarA, and agr genes are involved in biofilm formation and bacterial dispersion and were detected in 96.3%, 40.0%, 74.5%, and 100% of S. aureus strains, respectively, and 70.9% of the strains formed a detectable biofilm. Interestingly, 67.2% of the strains contained the icaA, agr, spa, clfA, sdrC, sdrD, sdrE, seg, seh, and sei genes, suggesting that this gene combination is important for successful catheter colonization. The results of this study provide significant insight into the virulence gene make-up of catheter-colonizing S. aureus strains, and will assist in developing a more targeted treatment approach for persistent S. aureus biofilm contamination of medical devices.

Phage therapy: An alternative to antibiotics in the age of multi-drug resistance

The practice of phage therapy, which uses bacterial viruses(phages) to treat bacterial infections, has been around for almost a century. The universal decline in the effectiveness of antibiotics has generated renewed interest in revisiting this practice. Conventionally, phage therapy relies on the use of naturally-occurring phages to infect and lyse bacteria at the site of infection. Biotechnological advances have further expanded the repertoire of potential phage therapeutics to include novel strategies using bioengineered phages and purified phage lytic proteins. Current research on the use of phages and their lytic proteins against multidrug-resistant bacterial infections, suggests phage therapy has the potential to be used as either an alternative or a supplement to antibiotic treatments. Antibacterial therapies, whether phage-or antibiotic-based, each have relative advantages and disadvantages; accordingly, many considerations must be taken into account when designing novel therapeutic approaches for preventing and treating bacterial infection. Although much about phages and human health is still being discovered, the time to take phage therapy serious again seems to be rapidly approaching.

Development of a Multiplex PCR for Diagnosis of Staphylococcus aureus, Escherichia coli and Bacillus cereus from Cows with Endometritis

Staphylococcus aureus, Escherichia coli and Bacillus cereus are the major agents of cow endometritis in dairy cows. A multiplex PCR （SEB-mPCR） was established based on the conserved genes of S. aureus, E. coli and B. cereus, and the detection limits were 103, 102 and 103 CFU mL-1, respectively. SEB-mPCR could not amplify genomic DNA of pathogenic bacteria of other common bovine diseases. A total of 309 vaginal discharge samples from cows with endometritis were tested by SEB-mPCR. Of the samples, 23.95% had the three kinds of bacteria detected, 17.15% had S. aureu and E. coli, 9.39% had E. coli and B. cereus, and 9.71% had S. aureus and B. cereus. The rates of infections with S. aureus, E. coli and B. cereus were 11.35, 16.18 and 9.06%, respectively. Therefore, SEB-mPCR has a potential as a diagnosis tool for endometritis in dairy cows.

MLKL对金黄色葡萄球菌感染所致小鼠肝脏和肾脏损伤的调控作用

运用ELISA、免疫荧光法、苏木素-伊红染色法以及流式细胞术分析了金黄色葡萄球菌(Staphylococcus aureus,S.aureus)分别感染MLKL基因敲除(MLKL^(-/-))和C57BL/6J小鼠后肝脏和肾脏中促炎性细胞因子(TNF-α和IL-1β)和抗炎因子(IL-10)的分泌、组织脏器的损伤水平、血液中中性粒细胞募集和小鼠存活情况。结果显示,在S.aureus感染MLKL^(-/-)小鼠肝脏和肾脏中TNF-α的分泌水平显著高于C57BL/6J小鼠肝脏和肾脏中TNF-α的分泌水平(P<0.001)。此外,S.aureus感染C57BL/6J小鼠肝脏和肾脏中,IL-10的分泌水平显著高于MLKL^(-/-)小鼠(P<0.05)。免疫荧光检测结果显示,与C57BL/6J小鼠相比,S.aureus感染MLKL^(-/-)小鼠后肝脏和肾脏中组织损伤标志物HMGB1蛋白表达处于较高水平(P<0.01)。病理切片结果显示,使用S.aureus感染后,MLKL^(-/-)小鼠肝脏和肾脏损伤程度显著高于C57BL/6J小鼠。S.aureus感染后,MLKL^(-/-)小鼠血液中CD11b和Gr-1双阳性的比例显著高于C57BL/6J小鼠血液中的比例(P<0.01)。使用高低剂量S.aureus分别感染小鼠后,发现MLKL^(-/-)小鼠的生存率低于C57BL/6J小鼠。结果表明,MLKL对S.aureus感染诱导的宿主细胞因子分泌具有一定的下调作用,进而发挥对宿主脏器损伤的保护作用,降低小鼠的病死率。

Studies on Enterotoxins and Antimicrobial Resistance in Staphylococcus aureus Isolated from Various Sources

Staphylococcus aureus represents a public health challenge all over the world. Therefore, this study aims to analyze the prevalence of five genes (sea, seb, sec, see and seg) encoding the staphylococcal enterotoxins in S. aureus isolated from different sources and to evaluate the association of these toxins in comparison to susceptibility towards 12 antimicrobials;antimicrobial susceptibility was conducted by disc diffusion method. Detection of staphylococcal enterotoxins was performed by PCR and the ability to express these genes was assessed among isolates by RT-PCR. The most common enterotoxin gene was sea gene (66%), followed by seb, sec, see and seg (38%, 23%, 19% and 5%) respectively. Expression of sea, seb and seg genes was variable. However, sec and see genes were not expressed by any of the tested isolates. No statistically significant association exists between (seb, sec and see) and isolation sources, while the sea was significantly associated with clinical isolates. High significant correlation was found between elevated sea expression and multidrug-resistance. Our findings indicate that the pathogenic potential of S. aureus may be greater than previously thought. This emphasizes the utmost need to implement proactive measures and more emphasis will be placed on the application of hygiene practices in hospitals to control S. aureus infection and enterotoxins production.