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。

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。

Epidemiology,surveillance and control of methicillin-resistant Staphylococcus aureus:an Overview

Staphylococcus aureus(S.aureus) is one of the most common human pathogens,causing a wide range of afflictions from minor infections of the skin to serious wound infections,bacteraemia,pneumonia and endocarditis. Methicillin,the first semisynthetic derivative of penicillin,was a new hope to treat penicillin resistant 5.aureus in the early 1960s.Nevertheless,only one year after its introduction,the first methicillin-resistant 5.aureus (MRSA) strains were detected.There is no golden rule in the control of MRSA.Nevertheless,using surveillance cultures of patients and healthcare personnel,strictly enforced contact precautions,and judicious use of broad-spectrum antibiotics have helped several countries,including Finland,Denmark,and the Netherlands to keep MRSA at a very low level.Conversely,countries including China,Japan,US,Italy,Greece,UK, where stringent counter-measure were not able to be installed,MRSA have become hyper-endemic.Control of MRSA in those countries were obliged to concentrate available resources to prevent MRSA infections only at patients at high risk of serious morbidity and mortality.

Detection and Characterization of Methicillin Resistant Staphylococcus aureus from Toilet and Classroom Door Handles in Selected Secondary Schools in Nairobi County

Background: Staphylococcus aureus is found on all surfaces especially in public areas like hospitals and schools and on frequently touched areas like toilet and classroom door handles. Methicillin resistant Staphylococcus aureus (MRSA) is a strain of Staphylococcus aureus which is resistant to methicillin. There are two types of MRSA: Community acquired methicillin resistant Staphylococcus aureus (CA-MRSA) and hospital acquired methicillin resistant Staphylococcus aureus (HA-MRSA). MRSA in the community presents a significant reservoir that could enter into healthcare facilities and spread among patients and also a risk for immune compromised persons in the community. Methodology: The study aimed at determining the prevalence of MRSA isolated from toilet and classroom door handles as a potential source of infection to the students and the workers in selected schools in Nairobi, Kenya. The study also compared the prevalence of MRSA between boarding and non-boarding girls, boys and mixed (both girls and boys in the same school) secondary schools. Twelve secondary schools in Nairobi County were randomly selected and 306 samples from both the toilet and classroom door handles were collected using sterile swabs and transported to the laboratory. Isolation of Staphylococcus aureus was done by the use of selective media Mannitol salt agar, antibiotic susceptibility of isolates was done by disk diffusion method, and molecular detection of mecA and PVL genes were done by polymerase chain reaction (PCR). Results: The prevalence of S. aureus was 20% and 15% were MRSA positive by both Antimicrobial Susceptibility Test and PCR detection. 20% showed the presence of PVL genes, 8% showed the presence of both genes and 56% of isolates with mecA gene had PVL genes. Conclusion: The presence of MRSA in this study emphasizes the need to formulate hygiene measures to prevent possible spread of MRSA and other transmissible pathogens to students and workers in the schools.

Genotypic Characterization of Methicillin-resistant Staphylococcus aureus Isolated from Pigs and Retail Foods in China

Objective To investigate the genotypic diversity of Methicillin-resistant Staphylococcus aureus （MRSA） isolated from pigs and retail foods from different geographical areas in China and further to study the routes and rates of transmission of this pathogen from animals to food. Methods Seventy-one MRSA isolates were obtained from pigs and retail foods and then characterized by multi-locus sequencing typing （MLST）, spa typing, multiple-locus variable number of tandem repeat analysis （MLVA）, pulsed-field gel electrophoresis （PFGE）, and antimicrobial susceptibility testing. Results All isolated MRSA exhibited multi-drug resistance （MDR）. Greater diversity was found in food-associated MRSA （7 STs, 8 spa types, and 10 MLVA patterns） compared to pig-associated MRSA （3 STs, 1 spa type, and 6 MLVA patterns）. PFGE patterns were more diverse for pig-associated MRSA than those of food-associated isolates （40 vs. 11 pulse types）. Among the pig-associated isolates, CC9-ST9-t899-MC2236 was the most prevalent clone （96.4%）, and CC9-ST9-t437-MC621 （20.0%） was the predominant clone among the food-associated isolates. The CC9-ST9 isolates showed significantly higher antimicrobial resistance than other clones. Interestingly, CC398-ST398-t034 clone was identified from both pig- and food-associated isolates. Of note, some community- and hospital-associated MRSA strains （t030, t172, t1244, and t4549） were also identified as food-associated isolates. Conclusion CC9-ST9-t899-MC2236-MDR was the most predominant clone in pigs, but significant genetic diversity was observed in food-associated MRSA. Our results demonstrate the great need for improved surveillance of MRSA in livestock and food and effective prevention strategies to limit MDR-MRSA infections in China.

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.

Implantable cardioverter defibrillator lead-related methicillin resistant Staphylococcus aureus endocarditis:Importance of heightened awareness

Methicillin resistant Staphylococcus aureus(MRSA) septicemia is associated with high morbidity and mortality especially in patients with immunosuppression,diabetes,renal disease and endocarditis.There has been an increase in implantation of cardiac implantable electronic devices(CIED) with more cases of devicelead associated endocarditis been seen.A high index of suspicion is required to ensure patient outcomes are optimized.The excimer laser has been very efficient in helping to ensure successful lead extractions in patients with CIED infections.We present an unusual case report and literature review of MRSA septicemia from device-lead endocarditis and the importance of early recognition and prompt treatment.

Postoperation of preauricular fistula cellulitis caused by methicillin-resistant staphylococcus aureus infection

A one-year-old baby girl with one-month history of recurrent pus fluid exuding from her left preauricular sinus orifice, who failed multiple courses of surgical drainage of the abscess and persistent debridement for the wound, presented with MRSA infection. The patient was treated with linezolid for three days. Her pain and paresthesia resolved, and C-reactive protein decreased to normal.

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。

Potentiating activity of luteolin on membrane permeabilizing agent and ATPase inhibitor against methicillin-resistant Staphylococcus aureus

Objective:To investigate the mechanism of antibacterial activity of luteoiin(LUT) against methicillin-resistant Staphylococcus aureus(MRSA).Methods:The mechanism of anti-MRSA activity of LUT was analyzed by the viability assay in membrane permeabilizing agent ATPase inhibitors,and peptidoglycan(PGN) derived from Staphylococcus aureus(S.aureus).Also,transmission electron microscopy was used to monitor survival characteristics and changes in S.aureus morphology.Results:Compared to the LUT alone,the optical density of suspensions treated with the combination of 125 μg/mL Tris and 230 μg/mL DCCD were reduced to 60%and 46%,respectively.PGN(15.6 μg/mL) gradually impeded the activity of LUT,and PGN(62.5 μg/mL) completely blocked the activity of LUT on S.aureus.Conclusions:Increased susceptibility to LUT with me Tris and DCCD combinations is evident in all tested MRSA isolates.The results indicate LUT synergy in increasing cytoplasmic membrane permeability and inhibiting ATPase.S.aureus PGN directly blocks the antibacterial activity of LUT,suggesting the direct binding of LUT with PGN.These findings may be validated for the development of antibacterial agent for low MRSA resistance.

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.

Treatment of methicillin-resistant Staphylococcus aureus infections:Importance of high vancomycin minumum inhibitory concentrations

Staphylococcus aureus(SA) infections remain a major cause of morbidity and mortality despite the availability of numerous effective anti-staphylococcal antibiotics.This organism is responsible for both nosocomial and community-acquired infections ranging from relatively minor skin and soft tissue infections to life-threateningsystemic infections.The increasing incidence of methicillin-resistant strains has granted an increasing use of vancomycin causing a covert progressive increase of its minimum inhibitory concentration(MIC)(dubbed the MIC "creep").In this way,the emergence of vancomycinintermediate SA(VISA) strains and heteroresistantVISA has raised concern for the scarcity of alternative treatment options.Equally alarming,though fortunately less frequent,is the emergence of vancomycin-resistant SA.These strains show different mechanisms of resistance but have similar problems in terms of therapeutic approach.Ultimately,various debate issues have arisen regarding the emergence of SA strains with a minimum inhibitory concentration sitting on the superior limit of the sensitivity range(i.e.,MIC = 2 μg/mL).These strains have shown certain resilience to vancomycin and a different clinical behaviour regardless of vancomycin use,both in methicillin-resistant SA and in methicillin-sensitive SA.The aim of this text is to revise the clinical impact and consequences of the emergence of reduced vancomycin susceptibility SA strains,and the different optimal treatment options known.

万古霉素联合骨搬移术治疗MRSA感染胫骨创伤性骨髓炎的效果及对血清TLR4、TNF-α和PCT水平的影响

目的:探讨万古霉素联合骨搬移术治疗耐甲氧西林金黄色葡萄球菌(MRSA)感染胫骨创伤性骨髓炎的效果及对血清Toll样受体4(TLR4)、肿瘤坏死因子α(TNF-α)和降钙素原(PCT)水平的影响。方法:选取2020年4月至2022年4月中南大学湘雅医学院附属海口市人民医院收治的MRSA感染胫骨创伤性骨髓炎患者120例,利用计算机生成的随机数列分为对照组、观察一组和观察二组,每组40例。对照组患者采用常规手术治疗,观察一组患者采用骨搬移术治疗,观察二组患者采用万古霉素联合骨搬移术治疗。比较三组患者血清TLR4、TNF-α和PCT水平,观察两组患者的临床疗效、MRSA清除率、炎症指标[白细胞计数(WBC)、血清C反应蛋白(CRP)和白细胞介素6(IL-6)]及血液流变学指标(血浆黏度、全血黏度、纤维蛋白原、红细胞压积、红细胞沉降率和红细胞聚集指数)水平。结果:治疗2周后,观察二组患者TLR4、TNF-α和PCT水平低于对照组、观察一组,差异均有统计学意义(P<0.05)。治疗2周后,观察二组患者的总有效率、MRSA清除率分别为92.50%(37/40)、90.00%(36/40),高于对照组[80.00%(32/40)、75.00%(30/40)]和观察一组[85.00%(34/40)、80.00%(32/40)],差异均有统计学意义(P<0.05)。治疗2周后,观察二组患者WBC、CRP和IL-6水平,血浆黏度、全血黏度、纤维蛋白原、红细胞压积和红细胞沉降率低于对照组和观察一组,红细胞聚集指数高于对照组和观察一组,差异均有统计学意义(P<0.05)。结论:万古霉素联合骨搬移术治疗MRSA感染胫骨创伤性骨髓炎的疗效较好,能有效抑制患者血清TLR4、TNF-α和PCT水平的升高。

The prevalence of methicillin-resistant Staphylococcus aureus colonization in emergency department fast track patients

BACKGROUND:Over the past two decades,methicillin-resistant Staphylococcus aureus(MRSA) has evolved from a hospital-associated infection to a significant public health threat in the community,causing outbreaks of soft tissue infections in otherwise healthy individuals.The goal of this study was to determine the prevalence of nasal MRSA colonization in low acuity Emergency Department(ED) Fast Track patients in order to better characterize the epidemiology of this pathogen.METHODS:We conducted a cross-sectional study of a convenience sample of adult patients from our ED Fast Track.Nasal swabs were analyzed for MRSA using a polymerase chain reaction assay.Study participants completed a survey assessing traditional risk factors for CA-MRSA colonization.RESULTS:A total of 106 ED Fast Track patients were tested.Four(3.8%,95%CI 1.5%-9.3%)were MRSA positive.Three traditional CA-MRSA risk factors(personal history of abscess,family history of abscess,and participation in contact sports) were examined.In patients with a positive MRSA nasal swab,only a personal prior history of abscess retained significance(OR 33,95%C11.7-676,P=0.02).CONCLUSION:This study found a higher prevalence of nasal MRSA colonization in low acuity ED Fast Track patients compared with historical community surveillance studies.A personal history of prior abscess was a significant risk for CA-MRSA carriage.

Synergistic Effect between Fucoidan and Antibiotics against Clinic Methicillin-Resistant <i>Staphylococcus aureus</i>

Fucoidan is a sulfated polysaccharide that is primarily extracted from brown seaweeds which has been broadly studied in recent years due to its numerous biological properties, including anticoagulant, antithrombotic, antitumor, and antiviral activities. In this study, fucoidan was evaluated against clinic isolated methicillin-resistant Staphylococcus aureus (MRSA) 1 - 20, either alone or with antibiotics, via broth dilution method and checkerboard and time kill assay. Minimum inhibitory concentrations (MICs)/Minimum bactericidal concentrations (MBCs) values for the fucoidan against all the tested bacteria ranged between 64 - 512/256 - 2048 microg/mL, for ampicillin 32 - 1024/64 - 1024 microg/mL and for oxacillin 8 - 64/16 - 256 microg/mL respectively. Furthermore, the MIC and MBC were reduced to one half-eighth as a result of the combination of the fucoidan with antibiotics. 2 - 6 hours of treatment with 1/2 MIC of fucoidan with 1/2 MIC of antibiotics resulted from an increase of the rate of killing in units of CFU/mL to a greater degree than was observed with alone. These results suggest that fucoidan could be employed as a natural antibacterial agent against multi-drug bacteria.

Intestinal carriage of methicillin resistant Staphylococcus aureus and extended-spectrum β-Lactamase-producing Enterobacteriacae in hospitalized and nonhospitalized patients and their clinical implications

Objective:To determine the clinical implication of and intestinal carriage with methicillin resistant Staphylococcus aureus(MRSA) and extended spectrumβ-lactamase(ESBL)-producing Enterobacteriacae.Methods: A total of 180 stool specimens were screened for MRSA and ESBL-producing enterobacteria.Identification of ESBL- producing Enterobacteriacae was done by MicroScan Walk Away 96 system(Dade Behring Inc.,West Sacramento,CA 95691,USA ) and confirmation by double-disc synergy test.MRSA was identified by disc diffusion using 30μg cefoxitin disc and the MicroScan.Results:The rate of fecal MRSA carriage was 7.8% (14/180),35.7%(5 /14) were recovered from surgical wards.Three patients(21,4%) had MRSA recovered from other body sites,and 2(14.2%) had in addition ESBL -producing Escherichia coli(E.coli) and Klebsiella pneumoniae(K.pneumoniae) respectively.Four(28.5%) patients with MRSA fical carriage died. MRSA fecal carriage was recovered from both inpatients and outpatients.Four(2.2%) cases carried ESBL-producing Enterobacteriacae in feces.Three(75%) were from intensive care unit(ICU).One patient had both ESBL-producing E.coli and K.pneumoniae from stool as well as E.coli from tracheal aspirate.Two ICU patients with fecal ESBL died.Conclusion:Fecal screening for MRSA and ESBL of all patients at high risk admitted to different hospital wards and ICUs and implementing infection control measures were recommended.

Combination of Acacetin with Antibiotics against Methicillin Resistant <i>Staphylococcus aureus</i>Isolated from Clinical Specimens

Methicillin-restitant Staphylococcus aureus (MRSA) is very dangerous bacteria and one of the most feared nosocomial germs. In this study, acacetin was evaluated against 20 clinical isolates of MRSA, either alone or in combination with antibiotics. The acacetin exhibited a good activity against isolates MRSA with MICs/MBCs ranged between 10-80/20-160 μg/mL, for ampicillin 64-1024/128-2048 μg/mL, and for oxacillin 8-32/16-64 μg/mL. The combination of acacetin plus oxacillin or ampicillin was reduced by ≥4-fold against isolates MRSA tested, evidencing a synergistic effect as defined by a FICI of ≤0.5. Furthermore, a time-kill study evaluating the growth of the tested bacteria was completely attenuated after 2-5 h of treatment with the 1/2 MIC of acacetin, regardless of whether it was administered alone or with oxacillin (1/2 MIC) or ampicillin (1/2 MIC). In conclusion, acacetin exerted synergistic effects when administered with oxacillin or ampicillin and the antibacterial activity and resistant regulation of acacetin against clinical isolates of MRSA might be useful in controlling MRSA infections.

巴西苏木素通过抑制SarA以PIA依赖性方式减少MRSA生物膜形成的研究

目的 探究巴西苏木素(brazilin,BN)抑制耐甲氧西林金黄色葡萄球菌(methicillin-resistant Staphylococcus aureus,MRSA)生物膜形成的机制,为开展中医药防治MRSA感染提供新思路。方法 建立MRSA ATCC43300菌株生物膜模型,试验分为BN 8、16和32μg/mL组及对照组;通过结晶紫法测定BN对MRSA生物膜的抑制作用;刚果红平板法、硫酸-苯酚法检测BN对细胞间多糖黏附素(polysaccharide intercellular adhesion,PIA)合成的影响;使用real-time PCR(qRT-PCR)方法验证胞间黏附素操纵子icaA和icaD转录水平;分析高通量转录组测序可能存在的生物膜抑制基因;通过qRT-PCR、Western blot方法对相关基因及蛋白加以验证;通过皮下埋植静脉导管建立MRSA生物膜感染小鼠模型进一步验证BN疗效。结果 与对照组相比,不同浓度的BN组均能显著减少MRSA生物膜及PIA生成,其中在最低剂量8μg/mL BN作用下,MRSA生物膜形成量下降40.17%(P<0.01)、PIA减少55.56%(P<0.01);通过qRT-PCR验证不同浓度的BN组均能显著抑制icaA和icaD基因的表达,其中在8μg/mL浓度下,icaA和icaD基因的表达量分别比对照组降低了59.03%(P<0.01)、48.33%(P<0.05);高通量测序显示sarA下调-1.458 log2;qRTPCR、Western blot结果显示,BN能显著抑制sarA转录及其蛋白表达;通过体内实验显示,BN能有效抑制小鼠体内MRSA生物膜的形成。结论 BN通过抑制SarA的表达,减少PIA的合成,进而干预生物膜的形成。

Emergence of staphylococcal cassette chromosome mec type Ⅰ with high-level mupirocin resistance among methicillin-resistant Staphylococcus aureus

Objective: To investigate the molecular epidemiology and antimicrobial resistance patterns of methicillin-resistant Staphylococcus aureus(MRSA) among healthcare workers and patients.Methods: MRSA isolates were recovered from nasal swabs collected at a tertiary care hospital of Nepal and confirmed on the basis of Gram staining, conventional biochemical tests, and PCR amplification of mec A gene. PCRs were also used for detection of the different resistance genes and staphylococcal cassette chromosome(SCC) mec types.Antibiotic susceptibility patterns of isolates were assessed by disc diffusion method and minimum inhibitory concentrations were determined by E-test.Results: A total of 29 MRSA were isolated from 536 nasal swabs(5.4%) of health care workers and patients at a tertiary care hospital in Nepal. All isolates were susceptible to amikacin, gentamicin, vancomycin(minimal inhibitory concentrations < 2 mg/m L), tigecycline, tetracycline, nitrofurantoin, rifampicin, quinupristin-dalfopristin, and linezolid. Among the 29 MRSA isolates, resistance to erythromycin(72%), ciprofloxacin(75%), co-trimoxazole(62%), clindamycin(10%), and chloramphenicol(10%) was found, and fifteen isolates(51%)exhibited high-level mupirocin resistance(minimal inhibitory concentrations > 1 024 mg/m L).Fourteen isolates were found harboring the mup A gene and one isolate was found carrying the novel mup B gene. High prevalence(68%) of SCCmec I type was found, followed by SCCmec V(13%) and SCCmec III(3%) among all the MRSA isolates.Conclusions: We found the emergence of SCCmec type I with high-level mupirocin resistance among MRSA in Nepal. Data also suggest that MRSA SCCmec type V strain has spread from the community to the hospital.

Identification of Panton-Valentine leukocidin virulence gene in methicillin-resistant Staphylococcus aureus isolated from clinical specimens of burn patients in Zare Hospitals of Sari, Iran

Objective:To identify the pathogenic gene of Panton-Valentine leukocidin in methicillin-resistant Staphylococcus aureus strain isolated from clinical specimens of burn patients in Shaheed Zare Burn Hospital.Methods:A total of 104 samples of Staphylococcus were collected and 78 aureus samples were isolated from Zare Hospital patients from November 2016 to July 2017.All isolates were identified using a standard biochemical and laboratory methodology in accordance with CLSI principles,and disk agar diffusion antibiogram were performed to identify methicillin resistant colonies.Then the presence of the Panton-Valentine leukocidin gene was tested by PCR.Results:Of the methicillin-resistant Staphylococcus aureus samples,80%were negative for the Panton-Valentine leukocidin gene,and only 20%of the samples had Panton-Valentine leukocidin gene.Male and female patients showed no significant difference in the positivity rate of Panton-Valentine leukocidin gene(16.12%vs.33.33%)(P=0.25).Besides,there was no significant difference in bacterial resistance or susceptibility to antibiotics between samples with or without the Panton-Valentine leukocidin gene.Conclusions:In recent years,increased resistance has been a serious threat.The resistance or susceptibility of Staphylococcus aureus strains to different antibiotics is different in different geographical locations.