北京分离株金黄色葡萄球菌基因型分析

目的对2000-2005年北京分离株金黄色葡萄球菌进行基因分型研究,了解其型别构成特征。方法分别对48株耐甲氧西林金黄色葡萄球菌（methicillin-resistant S．aureus,MRSA）和3株甲氧西林敏感金黄色葡萄球菌（methicillin-sensitive S．aureus,MSSA）进行spa基因序列分析及脉冲场凝胶电泳（pulsed field gel electrophoresis,PFGE）分析,并与多位点序列分析（multi locus sequencing typing,MLST）进行比较。结果在MRSA中,t030和t037为主要spa型别,分别占47．92％（23／48）和37．50％（18／48）;t002只在2005年菌株中出现,占14．58％（7／48）。3株MSSA型别分别为t377和t304。PFGE按带型差异及相似度分析,将所有菌株分为5组11型。结论t030和t037是MRSA临床分离株中的spa优势型别,A组和D组为PFGE优势型别。合理使用MLST、PFGE和spa分型方法对我国MRSA防治具有重要意义。     

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.     

Breaking down antibiotic resistance in methicillin-resistant Staphylococcus aureus: Combining antimicrobial photodynamic and antibiotic treatments

The widespread use of antibiotics drives the evolution of antimicrobial-resistant bacteria (ARB), threatening patients and healthcare professionals. Therefore, the development of novel strategies to combat resistance is recognized as a global healthcare priority. The two methods to combat ARB are development of new antibiotics or reduction in existing resistances. Development of novel antibiotics is a laborious and slow-progressing task that is no longer a safe reserve against looming risks. In this research, we suggest a method for reducing resistance to extend the efficacious lifetime of current antibiotics. Antimicrobial photodynamic therapy (aPDT) is used to generate reactive oxygen species (ROS) via the photoactivation of a photosensitizer. ROS then nonspecifically damage cellular components, leading to general impairment and cell death. Here, we test the hypothesis that concurrent treatment of bacteria with antibiotics and aPDT achieves an additive effect in the elimination of ARB. Performing aPDT with the photosensitizer methylene blue in combination with antibiotics chloramphenicol and tetracycline results in significant reductions in resistance for two methicillin-resistant Staphylococcus aureus (MRSA) strains, USA300 and RN4220. Additional resistant S. aureus strain and antibiotic combinations reveal similar results. Taken together, these results suggest that concurrent aPDT consistently decreases S. aureus resistance by improving susceptibility to antibiotic treatment. In turn, this development exhibits an alternative to overcome some of the growing MRSA challenge.

Antimicrobial-resistant bacteria (ARB) have raised public health concerns since the beginning of industrial antibiotic production in the 1940s (1). Healthcare-associated infections with ARB have caused significant morbidity, mortality, and economic burdens (2). In fact, according to the Centers for Disease Control and Prevention, over 2.8 million ARB infections occur every year, resulting in more than 35,000 deaths in total (3). Although many bacterial pathogens are successfully treated with antibiotic therapies, the treatment itself is the leading source of increasing antimicrobial resistance (4). The treatment methods for ARB most commonly involve the use of combination antibiotic therapies or treatment with adjuvants that target bacterial resistance mechanisms, including efflux pumps (5). These treatments are primarily beneficial due to their specific effectiveness against antimicrobial-resistant organisms but include moderate to severe undesired side effects such as neurotoxicity, kidney damage, and myelosuppression (6–8). Those who acquire ARB infections are much more likely to develop severe symptoms leading to poorer outcomes than those who acquire non-ARB infections (9). Some levels of prevalence and transmission dynamics are understood and being explored by improved monitoring, such as the World Health Organization global antimicrobial resistance and use surveillance system, which aid proper type and deployment of preventative measures. Nonetheless, a long-term solution to infection with diverse ARB has yet to be identified and serves as the ultimate goal.Antimicrobial photodynamic therapy (aPDT) is a technique by which pathogens are inactivated by reactive oxygen species (ROS) generated from the coincidence of molecular oxygen, a photosensitizer, and characteristic light of a particular wavelength (10). The resulting ROS may cause nonspecific biological oxidative stress (11). Additionally, noncytotoxic photosensitizers have been shown to influence specific drug localization and photoactivation wavelengths, corresponding to control of aPDT activation depth in tissues (12). The absorption spectrum of methylene blue, with a maximum molar absorptivity of 85,000 M⁻¹ cm⁻¹ at 664 nm, is concentration-dependent to dimerization and proportional to ionic strength at interfaces. The quantum yield of methylene blue fluorescence is dependent on the solvent used, and its interactions display a low quantum yield (0.04) in water. However, the fluorescence signal of methylene blue is concentration- and aggregation-dependent, and reductions are observed when the molecule interacts with membranes, proteins, and other biological substrates that favor electron transfer reactions. Methylene blue can act in both type I and type II mechanisms depending on its aggregation state. Methylene blue undergoes reduction reactions after electronic excitation, generating semireduced radicals and promoting mitochondrial NAD(P)H oxidation. Leuco-methylene blue generates high proton potentials, resulting in the generation of half of the 1O² radical species. The type II mechanism is favored in biological systems with higher oxygen concentrations in membranes than in water. The highest affinity of the molecule is for negatively charged interfaces, and melanin has been described in studies that illustrate methylene blue applications in dermatology. However, its quantum efficiency is reduced in tumors when administered intravenously (13).aPDT treatments have demonstrated efficacy against numerous microorganisms in experimental animal models. Although many photosensitizers are FDA approved for other photodynamic applications such as cancer therapy, they have not been approved for aPDT applications against ARBs (14). Methylene blue biocompatibility is exploited for the treatment of methemoglobinemia. Membranes of diseased tissues have redox properties that facilitate methylene blue reduction or oxidation. Methylene blue can also easily permeate membranes through lipid bilayers (15).Nevertheless, the promise of the approach has been demonstrated. For example, reports have shown that moderate aPDT doses eliminated most methicillin-resistant Staphylococcus aureus (MRSA) (16). Despite these advances, whether aPDT can offer potential benefits by reducing the doses required to combat ARB infection remains unresolved. If this were the case, the benefits associated with reduced antibiotic-associated side effects would be substantial. The radiation wavelength is normally chosen as the absorption peak of the molecule; this is the wavelength region of the most significant conversion of light energy into electronic energy of the molecule. Being electronically excited, the molecules are able, by collisional energy transfer, to produce the maximum number of ROS, thus maximizing the reactive effect of the photodynamic action. During clinical applications of aPDT, photosensitizers are usually administered systemically or topically. They are then activated by penetrating light greater than 600 nm in the therapeutic window of 600 to 800 nm (17). Wavelengths shorter than 600 nm are absorbed by hemoglobin, and wavelengths longer than 950 nm are absorbed by biological molecules that exhibit water vibration.In this study, we tested the hypothesis that aPDT improves antibiotic treatment effectiveness against MRSA. We found that aPDT did indeed improve the efficacy of antibiotic treatment against clinical isolates of MRSA. Taken together, these data set the stage for further development of aPDT as a strategy for combatting ARB infections.     

金黄色葡萄球菌肠毒素SEC3抑制剂的筛选及活性鉴定

目的从噬菌体随机12肽库中筛选出金黄色葡萄球菌SEC3抑制剂并鉴定其活性。方法用纯化的重组的金黄色葡萄球菌SEC3包被酶标板,按吸附-洗脱-扩增的淘洗过程对噬菌体随机12肽库进行3轮筛选;用竞争ELISA法观察单个噬菌体克隆的竞争抑制效应,评价其活性。结果噬菌体3轮筛选的投入产出比逐轮升高,回收率从4.5×10-6升高至6.3×10-4,升高140倍,提示具有良好的富集效果;与阴性对照（未加噬菌体）相比,随机挑选的8个噬菌体克隆（A1~A8）竞争抑制率为10.6%~38.3%,差异有统计学意义（t值为9.0~23.5,P〈0.05）,其中A1平均竞争抑制率最高,为（30.5±7.4）%,A5的平均竞争抑制率最小,为（16.4±4.7）%。以噬菌体滴度对数值为x轴,以克隆噬菌体各滴度对应的平均竞争抑制率为y轴,绘制竞争抑制曲线,其回归方程为Y=2.7943X-4.7733,相关系数r=0.935,决定系数R2=0.8727。在噬菌体滴度在108~1012pfu范围内,随着噬菌体滴度的增高,其抑制率也增高,且克隆噬菌体滴度在1011pf或1012pfu的竞争抑制率最高。结论用纯化的SEC3从噬菌体随机12肽库中筛选的SEC3抑制剂具有一定的竞争抑制活性,而且竞争抑制活性随着噬菌体滴度的增高而增强。     

Treatments and limitations for methicillin-resistant Staphylococcus aureus: A review of current literature

Methicillin-resistant Staphylococcus aureus (MRSA) has remained a major threat to healthcare; in both hospital and community settings over the past five decades. With the current use of antibiotics for a variety of infections, including MRSA, emerging resistance is a major concern. Currently available treatments have restrictions limiting their use. These issues include, but are not limited to, side effects, cross-resistance, lack of understanding of pharmacokinetics and clinical pharmacodynamics, gradual increment in minimal inhibitory concentration over the period (MIC creep) and ineffectiveness in dealing with bacterial biofilms. Despite availability of various therapeutic options for MRSA, the clinical cure rates remain low with high morbidity and mortality. Given these challenges with existing treatments, there is a need for development of novel agents for MRSA. Along with prompt infection control strategies and strict implementation of antibiotic stewardship, cautious use of newer anti-MRSA agents will be of utmost importance. This article reviews the treatments and limitations of MRSA management and highlights the future path.     

产杀白细胞素金黄色葡萄球菌感染的研究现状

国外多数回顾性研究发现产杀白细胞素(PVL)金黄色葡萄球菌感染有着特有的临床表现,特别是产PVL金黄色葡萄球菌相关性坏死性肺炎可能为一新现的临床疾病,由此PVL在金黄色葡萄球菌感染中的致病研究日益受到重视.本文就目前对产PVL金黄色葡萄球菌感染的致病机制、流行病学、检测和防治等问题研究作一综述.     

耐甲氧西林金黄色葡萄球菌的耐药状况及治疗进展

革兰阳性菌的耐药状况日趋严重和复杂,给临床治疗带来很大困难.研究革兰阳性菌的耐药机制、寻求对革兰阳性耐药菌有效的药物成为近年来国内外研究关注的热点.耐甲氧西林金黄色葡萄球菌是目前研究较为集中和深入的革兰阳性耐药致病菌之一,本文简要对其感染状况、耐药趋势、耐药机制及抗耐甲氧西林金黄色葡萄球菌感染药物研究等方面的进展作一综述.     

Usefulness of previous methicillin-resistant Staphylococcus aureus screening results in guiding empirical therapy for S aureus bacteremia

BACKGROUND:

Staphylococcus aureus bacteremia (SAB) is an important infection. Methicillin-resistant S aureus (MRSA) screening is performed on hospitalized patients for infection control purposes.

OBJECTIVE:

To assess the usefulness of past MRSA screening for guiding empirical antibiotic therapy for SAB.

METHODS:

A retrospective cohort study examined consecutive patients with confirmed SAB and previous MRSA screening swab from six academic and community hospitals between 2007 and 2010. Diagnostic test properties were calculated for MRSA screening swab for predicting methicillin resistance of SAB.

RESULTS:

A total of 799 patients underwent MRSA screening swabs before SAB. Of the 799 patients, 95 (12%) had a positive and 704 (88%) had a negative previous MRSA screening swab. There were 150 (19%) patients with MRSA bacteremia. Overall, previous MRSA screening swabs had a positive likelihood ratio of 33 (95% CI 18 to 60) and a negative likelihood ratio of 0.45 (95% CI 0.37 to 0.54). Diagnostic accuracy differed depending on mode of acquisition (ie, community-acquired, nosocomial or health care-associated infection) (P<0.0001) and hospital (P=0.0002). At best, for health care-associated infection, prior MRSA screening swab had a positive likelihood ratio of 16 (95% CI 9 to 28) and a negative likelihood ratio of 0.27 (95% CI 0.17 to 0.41).

CONCLUSIONS:

A negative prior MRSA screening swab cannot reliably rule out MRSA bacteremia and should not be used to guide empirical antibiotic therapy for SAB. A positive prior MRSA screening swab greatly increases likelihood of MRSA, necessitating MRSA coverage in empirical antibiotic therapy for SAB.     

Role of echocardiography in uncomplicated Staphylococcus aureus catheter-related bloodstream infections

Uncomplicated bacteremia and catheter-related bloodstream infection (CRBSI) are frequently suggested as factors associated with low risk of infective endocarditis in Staphylococcus aureus bacteremia (SAB). Nevertheless, guidelines recommend that echocardiography in all patients with SAB. We evaluated the effects of echocardiography on patient outcomes. Patients with uncomplicated S. aureus CRBSI were retrospectively identified between January 2013 and June 2018 at a 1950-bed, tertiary-care university hospital. Treatment failure was defined as any case of relapse or all-cause death within 90 days. Of 890 SAB patients, 95 with uncomplicated S. aureus CRBSI were included. Thirty-two patients underwent echocardiography within 30 days of their first positive blood culture. Two patients who underwent echocardiography revealed right-sided infective endocarditis. One patient who did not undergo echocardiography experienced recurrent SAB (peripheral CRBSI) 85 days after his first positive blood culture. There were no SAB-related deaths. The Kaplan–Meier curves of treatment failure showed no significant differences between patients who did and did not undergo echocardiography (P = .77). In multivariable analysis, risk factors for treatment failure were liver cirrhosis (hazard ratio: 9.60; 95% confidence interval: 2.13–43.33; P = .003) and other prostheses (hazard ratio: 63.79; 95% confidence interval: 5.05–805.40; P = .001). This study did not verify the putative association between treatment failure and implementation of echocardiography in patients with uncomplicated S. aureus CRBSI. Given the low observed rates of adverse outcomes, routine echocardiography might not be obligatory and could be performed on an individual basis.     

金黄色葡萄球菌Agr群体感应系统及其抗毒力治疗研究进展

辅助基因调控(Auxiliary gene regulation,Agr)群体感应系统广泛存在于金黄色葡萄球菌中,是研究最广泛的细菌双组分调节系统之一,在金黄色葡萄球菌定植、感染过程中通过调控大量毒力因子、生物膜形成等起着至关重要的作用;抗毒力治疗是一种通过降低或阻断病原体感染后的毒力表达但不影响细菌生存能力,使其易被宿主的免疫防御系统杀死的治疗方法。本文通过对金黄色葡萄球菌Agr群体感应的表达调控与阻断Agr表达抑制其毒力产生的抗毒力治疗等两个方面进行阐述,以期为金黄色葡萄球菌的治疗提供新的研究思路。     

耐甲氧西林金黄色葡萄球菌（MRSA）感染机制研究进展

耐甲氧西林金黄色葡萄球菌（MRSA）是一种新型金黄色葡萄球菌,它会造成严重感染性疾病。MRSA对p内酰胺类抗生素耐药性的产生及毒力的加强使得它成为了临床治疗的-大痼疾。一些虽然低效但较少产生耐药的抗生素的出现使得MRSA治疗有了新的选择。同时,研究者正在逐渐阐明MRSA基因突变和病原学特征（耐药性、毒力等）的相关性。这些成果都将为今后MRSA的临床治疗以及新药和疫苗的开发提供宝贵的理论支持与指导。     

感染耐甲氧西林金黄色葡萄球菌的糖尿病足溃疡患者的临床特点及分析

目的研究感染耐甲氧西林金黄色葡萄球菌（MRSA）的糖尿病足（DF）溃疡患者的临床特点,探讨MRSA对DF溃疡预后的影响。方法分析2005年6月-2008年5月102例DF感染（DFI）患者入院48h内及抗感染治疗后创面棉拭子和组织细菌培养结果,将其分为4组：A组16例,入院后48h内MRSA阳性;B组25例,入院后48h内甲氧西林敏感金黄色葡萄球菌（MSSA）阳性;C组27例,入院后48h内革兰氏阴性菌阳性,经抗感染治疗后MRSA阳性;D组34例,入院后48h内革兰氏阴性菌阳性,住院期间始终未分离出MRSA菌株。将A组与B组、C组与D组分别进行比较,研究感染MRSA的高危因素以及其对患者住院时间、住院费用及预后的影响。结果A、B组间WBC、RBC、白蛋白（ALB）和DF溃疡面积差异均有统计学意义（P均〈0．05）,而DM病程、DF溃疡病程、住院时间、日住院费、高敏C-反应蛋白（hsC—RP）差异均无统计学意义;C、D组间DM病程差异有统计学意义（P〈0．05）,而其余指标差异均无统计学意义。43株MRSA对庆大霉素／环丙沙星／红霉素／四环素耐药率均为100％。结论与MSSA阳性DFI患者比较,MRSA阳性DFI患者全身炎症反应更明显。骨髓炎、复发性溃疡、频繁住院、交叉感染及溃疡面积〉4cm^2可能是DFI患者感染MRSA的高危因素,而DF溃疡病程与其无关。DFI分离的MRSA多重耐药现象普遍存在。对DF患者及时发现MRSA菌株并清创处理,将不影响患者住院时间、住院费用及预后,避免盲目应用万古霉素等新一代抗生素,以延缓新型耐药菌的产生。     

急诊重症监护病房金黄色葡萄球菌耐药性分析

目的:研究急诊重症监护病房(ICU)2009—2010年临床分离的金黄色葡萄球菌(金葡菌)对各类抗菌药物的耐药性分析。方法:按统一的材料、方法和判断标准[美国临床实验室标准化协会(CLSI)2009年版]对急诊ICU2009年1月至2010年12月分离的117株金葡菌行耐药性监测,并对下呼吸道感染者的临床资料行回顾性分析。结果:117株金葡菌中耐甲氧西林金葡菌(MRSA)占85.5%,甲氧西林敏感金葡菌(MSSA)为14.5%;随着年龄的增加,MRSA感染者增多;MRSA对喹诺酮、红霉素、四环素的耐药率较高,对万古霉素、替考拉宁、利奈唑胺和达福普汀-奎奴普丁的敏感率仍保持100%;未发现万古霉素中介株(VISA)和耐药株(VRSA);急性生理学及慢性健康状况评分Ⅱ(APACHⅡ)评分、高龄(>70岁)、住院天数>20 d、清蛋白水平、慢性肺病、机械通气、意识障碍、长期住护理院是下呼吸道感染MRSA的危险因素,清蛋白、高龄和住护理院是其独立危险因素。结论:MRSA的耐药性高,应加强其耐药性监测,并根据分离株的耐药特点规范抗菌药物的应用。     

金黄色葡萄球菌检测方法的进展

金黄色葡萄球菌尤其是耐甲氧西林金黄色葡萄球菌的感染日益增多,对人类健康造成巨大威胁.传统检测方法存在局限性,本文从分子生物学和免疫学方法两方面对目前金黄色葡萄球菌检测方法的进展进行综述,分析比较了各类方法的优缺点.     

2011年医院金黄色葡萄球菌临床分布及耐药性研究

目的调查金黄色葡萄球菌(SA)和耐甲氧西林金黄色葡萄球菌(MRSA)临床分布情况及其对常用抗菌药物的耐药率。方法对我院2011年检出的SA和MRSA药敏结果分析。结果 2011年共检出SA 146株(其中MRSA 29株),菌株主要来源为痰液49株(33.56%),脓液37株(25.34%),泌尿生殖道分泌物11株(7.53%);菌株分布前三位的科室是神经外科36株(24.66%)、创伤外科24株(16.44%)、呼吸消化科17株(11.64%);其中MRSA 29株(19.8%)。分离的146株SA对万古霉素、利奈唑胺全部敏感,其中MRSA对红霉素、克林霉素、四环素和环丙沙星呈现较高的耐药率,达70%以上;MRSA对各种抗生素的耐药率均明显高于MSSA,并呈现多重耐药。结论通过对SA临床分布和耐药率的分析,有利于采取措施控制医院内MR-SA的感染及流行并能指导临床合理用药。     

Investigation of a cluster of Staphylococcus aureus invasive infection in the Top End of the Northern Territory

Introduction: Staphylococcus aureus invasive infection remains a serious condition associated with considerable morbidity and mortality. Following notification of five cases at Royal Darwin Hospital (RDH), we searched for related cases, determined their epidemiological characteristics and attempted to identify the source of this apparent cluster. Methods: We reviewed RDH microbiology records between June 1996 and April 1997 for S. aureus isolates with similar antibiograms to notified cases. We used antibiotic resistance patterns, bacteriophage typing and two molecular typing techniques to subtype implicated isolates. Hospital records were reviewed for admission details and associated costs were estimated. Results: Fifty-four cluster-related isolates occurred in 47 separate presentations. The peak incidence was in the wet season. The most important risk factor for staphylococcal invasive infection was the presence of skin sores/scabies in 17/54 cases (31%), followed by intravascular line use in 14/54 (26%), open trauma in 11/54 (20%), underlying end stage renal failure and alcoholism each in ten of 54 (18%). The mean admission length was 30 days and antibiotics were given for an average of 23 days. Death due to S. aureus infection occurred in eight of 47 (17%) presentations. S. aureus pneumonia was community acquired in 12/13 patients (92%) and six of 13 (46%) died. Ten of 13 (80%) pneumonia patients had at least one other focus of S. aureus infection. The cost of antibiotics and hospital bed per presentation was approximately $16,000. Presentations with skin sores/scabies cost considerably more ($31,000). No common epidemiologic features were found for community or hospital acquired cases. Conclusion: Considerable mortality and cost was attributable to cases of S. aureus invasive infection during this cluster; particularly those with community acquired pneumonia or skin sores/scabies. Staphylococcal antibiotic cover should be considered early for unwell patients presenting to hospital with pneumonia and other signs of potential S. aureus infection. It is appropriate to target public health efforts to prevent skin sores and to provide adequate treatment when they occur.