Community-associated methicillin-resistant Staphylococcus aureus (MRSA) in Australia

A series of epidemics of community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) have occurred in Australia, starting in Western Australia in the early 1990s, in the Northern Territory soon thereafter and in eastern states in the mid 1990s. The Western Australian epidemic has been due mainly to Panton–Valentine leukocidin (PVL)-negative clones, whilst PVL-positive clones have predominated in the east. More recently, the major epidemic clones have spread throughout the country, whilst multiple new minor clones have emerged, mainly in Western Australia. A total of 45 clones of CA-MRSA have been detected in Australia to date: 30 of these carry SCCmec IV, 6 carry SCCmec V and 9 carry novel SCCmec types. Overall, CA-MRSA clones have been associated predominantly with skin and soft-tissue infections. PVL-positive clones have been associated with furunculosis, necrotising pneumonia and osteomyelitis and have caused fatalities in otherwise healthy children and young adults. Initial treatment of these infections remains problematic, as it is frequently inappropriate. Of particular concern, healthcare-associated acquisition of CA-MRSA clones is now increasing, although major hospital outbreaks have not occurred yet.     

Meticillin-resistant Staphylococcus aureus (MRSA): screening and decolonisation

Meticillin-resistant Staphylococcus aureus (MRSA) infections are of increasing importance to clinicians, public health agencies and governments. Prevention and control strategies must address sources in healthcare settings, the community and livestock. This document presents the conclusions of a European Consensus Conference on the role of screening and decolonisation in the control of MRSA infection. The conference was held in Rome on 5-6 March 2010 and was organised jointly by the European Society of Clinical Microbiology and Infectious Diseases (ESCMID) and the International Society of Chemotherapy (ISC). In an environment where MRSA is endemic, universal or targeted screening of patients to detect colonisation was considered to be an essential pillar of any MRSA control programme, along with the option of decolonising carriers dependent on relative risk of infection, either to self or others, in a specific setting. Staff screening may be useful but is problematic as it needs to distinguish between transient carriage and longer-term colonisation. The consequences of identification of MRSA-positive staff may have important effects on morale and the ability to maintain staffing levels. The role of environmental contamination in MRSA infection is unclear, but screening may be helpful as an audit of hygiene procedures. In all situations, screening procedures and decolonisation carry a significant cost burden, the clinical value of which requires careful evaluation. European initiatives designed to provide further information on the cost/benefit value of particular strategies in the control of infection, including those involving MRSA, are in progress.     

Reduced glycopeptide susceptibility in methicillin-resistant Staphylococcus aureus (MRSA)

Vancomycin and other glycopeptide antibiotics are the current mainstay of therapy for infections caused by methicillin-resistant Staphylococcus aureus (MRSA). However, the high prevalence of MRSA has led to increased use of vancomycin in chronic and seriously ill patients and has resulted in the emergence of MRSA with reduced susceptibility to glycopeptides. Multiple MRSA phenotypes demonstrate reduced susceptibility to glycopeptides. According to the Clinical and Laboratory Standards Institute, vancomycin-intermediate S. aureus (VISA) are now those isolates with minimum inhibitory concentrations (MICs) between 4 microg/mL and 8 microg/mL, whilst heterogeneous VISA (hVISA) strains appear to be susceptible to vancomycin but contain a subpopulation of cells with reduced susceptibility to vancomycin (MICs > or = 4 microg/mL). At this time, MICs for these strains are reported to range between 1 microg/mL and 2 microg/mL. Vancomycin-resistant S. aureus (VRSA) are defined as those having MICs > or = 16 microg/mL. The detection of reduced susceptibility to vancomycin by routine susceptibility testing is unreliable and vancomycin non-susceptibility is most probably being underreported. Reports of reduced clinical efficacy associated with vancomycin MICs between 1 microg/mL and 2 microg/mL have been published. Patients most at risk of infection by hVISA, VISA and VRSA appear to be those with previous exposure to vancomycin. VRSA appears in the elderly and those with chronic leg or decubitus ulcers mainly containing vancomycin-resistant enterococci, which were probably the donor organism of the vanA gene to S. aureus. All MRSA strains recovered from patients whose infections do not respond to vancomycin treatment should be tested accurately for vancomycin susceptibility if these phenotypes are not to be missed. Treatment options for infections due to MRSA with reduced susceptibility to vancomycin are limited. Rapid identification of patients harbouring VRSA, VISA or hVISA as well as prompt isolation and adherence to infection control protocols are paramount in controlling the dissemination of these pathogens.     

Synergistic effects of berberines with antibiotics on clinical multi-drug resistant isolates of methicillin-resistant Staphylococcus aureus (MRSA)

N-Methyl-dihydroberberine (M-Ber) was synthesized, and antibacterial activities of Berberine (Ber) and M-Ber alone and combined with antibiotics were studied against ten clinical MRSA isolates. MICs/MBCs (μg/ml, alone) ranges were 32–128/64–256 (Ber) and 64–128/256–1,024 (M-Ber) by a broth microdilution method. Significant synergies of Ber (M-Ber)/Azithromycin and Ber (M-Ber)/Levofloxacin combinations were observed by the chequerboard test. The Ber (M-Ber)/Ampicillin and Ber (M-Ber)/Cefazolin combinations showed indifference. These results demonstrated that Ber and M-Ber enhanced the in vitro inhibitory efficacy of Azithromycin and Levofloxacin, which had potential for combinatory therapy of patients infected with MRSA.     

Phytochemical constituents from Cassia alata with inhibition against methicillin-resistant Staphylococcus aureus (MRSA)

The methanolic extract of the leaves of CASSIA ALATA was sequentially partitioned in increasing polarity to afford the hexane, chloroform, butanol and residual extract. Crude extracts were evaluated against MRSA using the agar well diffusion assay. The butanol and chloroform extracts both exhibited inhibition against MRSA with inhibition indexes of 1.03 +/- 0.16 and 0.78 +/- 0.07 at the concentration of 50 mg/mL. The butanol extracts were further purified using silica gel and reverse phase chromatography to afford kaempferol ( 1), kaempferol 3- O-beta-glucopyranoside ( 2), kaempferol 3- O-gentiobioside ( 3) and aloe emodin ( 4). The four constituents showed varying degrees of inhibition against MRSA. Both 1 and 4 exhibited MIC (50) values of 13.0 +/- 1.5 microg/mL and 12.0 +/- 1.5 microg/mL, respectively. The kaempferol glycosides 2 and 3 were less active with MIC (50) values of 83.0 +/- 0.9 microg/mL and 560.0 +/- 1.2 microg/mL, respectively. A free hydroxyl group at C-3 of the flavonol structure is a structural requirement for the inhibition of MRSA.     

Epileptogenic activity of methicillin-resistant Staphylococcus aureus (MRSA) antibiotics in rats

The present study was undertaken to clarify the epileptogenic activity induced by intracerebroventricular injection (i.c.v.) of antibiotics effective in methicillin-resistant Staphylococcus aureus (MRSA) in chronically electrode implanted rats. Teicoplanin (10-100 microg, i.c.v.) caused dose-related electroencephalographic (EEG) seizure characterized by an uninterrupted high voltage and wave complex. At the same time, the rats showed forelimb clonus, head nodding, jumping and severe convulsion. At a high dose (100 microg, i.c.v.), the drug caused a severe twisting immediately after the intracerebroventricular injection (i.c.v.) followed by jumping and violent convulsion with a continuous rhythmic spike and wave complex in EEG. On the other hand, vancomycin (30-1000 microg, i.c.v.) caused no or almost no epileptogenic activity in terms of behavior and in EEG. However, at a high dose (1000 microg, i.c.v.), the drug caused an occasional spike from the hippocampus without showing any behavioral changes in the rats. Fosfomycin (30-1000 microg, i.c.v.), cefazolin (10-100 microg, i.c.v.) and penicillin G (30-300 microg, i.c.v.), used as reference drugs, caused dose-dependent epileptogenic activity in both EEG. From these findings, it was found that teicoplanin caused a potent epileptogenic activity, different to vancomycin. Therefore, it can be concluded that vancomycin may be safety on epileptogenic activity used for the clinical purpose of infections caused by MRSA.     

Costs of hospital-acquired methicillin-resistant Staphylococcus aureus (MRSA) and its control

For most countries badly affected by methicillin-resistant Staphylococcus aureus (MRSA) there have been many years of debate about its relative virulence compared with methicillin-susceptible S. aureus (MSSA) and whether it could be controlled. Now that it is endemic in the majority of hospitals around the world, it is clear that it is at least as virulent as MSSA and is an additional burden of healthcare-acquired infection. There is increasing evidence that, despite this endemicity, control efforts can be successful, although they are often perceived as expensive. In reality, there is a large body of consistent evidence that control is highly cost effective, particularly in the context of the huge societal costs of MRSA and the future ever-greater threats that it poses.     

Infective endocarditis caused by USA300 methicillin-resistant Staphylococcus aureus (MRSA)

We report seven cases of infective endocarditis caused by USA300 methicillin-resistant Staphylococcus aureus (MRSA) at an urban, tertiary care, academic institution. Five strains were community associated and two were healthcare associated. All patients were injection drug users. Staphylococcus aureus isolates were characterised as USA300-type MRSA using pulsed-field gel electrophoresis. Five cases were right-sided endocarditis and two cases were left-sided. The mean length of in-hospital antimicrobial therapy was 23 days and the mean length of total antibiotic therapy was 55 days. Complications included heart failure resulting in valve replacement in one patient as well as death in that patient. As USA300 strains of MRSA continue to increase in prevalence, clinicians must be aware of the increasing spectrum of illness in considering management and prevention strategies.     

Anti-methicillin-resistant Staphylococcus aureus (MRSA) substance from the marine bacterium Pseudomonas sp. UJ-6

A multivalent approach to discover a novel antibiotic substance against methicillin-resistant Staphylococcus aureus (MRSA), a marine bacterium, UJ-6, exhibiting an antibacterial activity against MRSA was isolated from seawater. The isolated strain was identified to be Pseudomonas sp. by the morphology, biochemical, and genetical analyses. The ethyl acetate extract of Pseudomonas sp. UJ-6 culture showed significant ant-MRSA activity. Bioassay-guided isolation of the extract using a growth inhibitory assay led to the isolation and identification of an active compound exhibiting anti-MRSA activity. Based on the analyses of the physicochemical and spectroscopic data including nuclear magnetic resonance and mass, the compound was identified to be 1-acetyl-beta-carboline. The minimum inhibitory concentration (MIC) of the compound was determined to be in a range of 32–128 μg/ml against MRSA strains. The MIC values against MRSA were superior or equal to those of other natural compounds such as catechins, suggesting that 1-acetyl-beta-carboline would be a good candidate in applications of the treatment of MRSA infection.     

耐甲氧西林金葡菌到万古霉素高度耐药金葡菌的发展及其感染的药物治疗

随着万古霉素用量增加,耐甲氧西林金葡菌(MRSA)对万古霉素敏感性逐渐下降.依据其对万古霉素敏感性的差异可分成异质性万古霉素中度耐药金葡菌(hVISA)、万古霉素中度耐药金葡菌(VISA)和万古霉素高度耐药金葡菌(VRSA)等3类.本文简要综述卜述3类金葡菌的发展、相关耐药机制及其感染的药物治疗现状.     

Update on screening and clinical diagnosis of meticillin-resistant Staphylococcus aureus (MRSA)

Based on the failure of conventional control strategies, some experts and public health officials have promoted active screening to detect asymptomatic carriers of meticillin-resistant Staphylococcus aureus (MRSA) as an effective prevention strategy. Data regarding the (cost-) effectiveness of MRSA screening have recently grown and have produced mixed results. Several clinical studies have not only provided conflicting findings but have also raised numerous issues about the appropriate populations for universal versus targeted screening, screening method(s) and intervention(s). It must also be emphasised that screening alone is not effective. Results should be followed by appropriate interventions to reduce the risk of MRSA transmission and infection. We believe a reasonable approach in most European hospitals with an MRSA on-admission prevalence of <5% is to use targeted rather than universal screening (predominantly with chromogenic media, except for high-risk units and critically ill patients for whom molecular tests could be cost effective), after carefully considering the local MRSA epidemiology, infection control practices and vulnerability of the patient population. This strategy is likely to be cost effective if linked to prompt institution of control measures.     

Relationship between arbekacin-susceptibility and aminoglycoside-resistant gene of methicillin-resistant Staphylococcus aureus (MRSA)

The susceptibility to arbekacin (ABK) of methicillin-resistant Staphylococcus aureus (MRSA) was investigated to find out how it related to aac(6')/aph(2") gene. In 49 isolates of MRSA for which MIC of ABK ranged from 0.125 to 64 micrograms/ml, the MICs of ABK for 38 strains carrying aac(6')/aph(2") gene were widely distributed from 0.25 to 64, whereas those for 11 strains without that gene were all < or = 0.5 microgram/ml. Residual rate of ABK activity was higher than that of gentamicin after the reaction with each crude enzyme preparation extracted from 3 isolates of MRSA, carrying aac(6')/aph(2") and aad(4',4") genes. Furthermore, 97 strains of MRSA isolated at Kanagawa prefecture in Japan in 1999 were all sensitive to ABK, although 28 strains of them carried aac(6')/aph(2") gene. These results showed that ABK resistance was not necessarily related to carrying aac(6')/aph(2") gene in clinical isolates of MRSA.     

Community-acquired methicillin-resistant Staphylococcus aureus (MRSA): new issues for infection control

The emergence and clonal expansion of strains of community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) have created new challenges with their entrance to hospitals. The increased virulence of CA-MRSA in concert with the depressed immunity of inpatients may cause added morbidity and mortality expected from healthcare-associated infections. Questions about changing prophylactic and empirical therapy as well as the use of intravenous immunoglobulin for life-threatening infections are addressed.     

Prevalence,Enterotoxigenic Potential and Antimicrobial Resistance of Staphylococcus aureus and Methicillin-Resistant Staphylococcus aureus (MRSA) Isolated from Algerian Ready to Eat Foods

Staphylococcus aureus causes a foodborne intoxication due to the production of enterotoxins and shows antimicrobial resistance, as in the case of methicillin-resistant strains (MRSA). Herein, we analyzed 207 ready-to-eat foods collected in Algeria, reporting a S. aureus prevalence of 23.2% (48/207) and respective loads of coagulase positive staphylococci (CPS) ranging from 1.00 ± 0.5 to 5.11 ± 0.24 Log CFU/g. The 48 S. aureus isolates were widely characterized by staphylococcal enterotoxin gene (SEg)-typing and 16S-23S rDNA intergenic spacer region (ISR)-PCR, as well as by detecting tst and mecA genes, genetic determinants of toxic shock syndrome toxin-1 and methicillin resistance, respectively. We found that the S. aureus isolates belonged to seven different SEg-types harboring the following combinations of genes: (1) selW, selX; (2) egc (seG, seI, seM, seN, seO), selW, selX; (3) seA, seH, seK, seQ, selW, selX; (4) seB, selW, selX; (5) seD, selJ, seR, selW, selX; (6) seH, selW, selX, selY; and (7) seA, egc, selW, selX, while among these, 2.1% and 4.2% were tst- and mecA- (staphylococcal chromosomal cassette mec-type IV) positive, respectively. Selected strains belonging to the 12 detected ISR-types were resistant towards antimicrobials including benzylpenicillin, ofloxacin, erythromycin, lincomycin, tetracyclin, kanamycin, oxacillin, and cefoxitin; 8.3% (1/12) were confirmed as MRSA and 16.7% (2/12) were multidrug resistant. The present study shows the heterogeneity of the S. aureus population in Algerian ready-to-eat foods as for their toxigenic potential and antimicrobial resistance, shedding the light on the quality and safety related to the consume of ready-to-eat foods in Algeria.     

Methicillin-resistant Staphylococcus aureus (MRSA) isolated at Fukuoka University Hospital and hospitals and clinics in the Fukuoka city area

Bacteriological and epidemiological studies were carried out on 106 isolates of methicillin-resistant Staphylococcus aureus (MRSA) isolated at our hospital (56 isolates) and from 15 other hospitals and clinics (50 isolates) in the Fukuoka city area. Strains were studied regarding coagulase-type, beta-lactamase production, and antimicrobial susceptibility; genotype studies used pulsed-field gel electrophoresis (PFGE) with cluster analysis. The majority of isolates produced coagulase type II (75.5%) and beta-lactamase (72. 6%); there was high susceptibility to arbekacin (84.9%) but no resistance to vancomycin. Dendrogram analysis of PFGE patterns identified five major clusters that generally correlated with coagulase-type and beta-lactamase production. Though isolates of two clusters were both coagulase type II and beta-lactamase producing, which was the most common circulating strain both in our hospital and other hospitals and clinics, dendrogram analysis of PFGE patterns showed that they were heterogeneous. Four genetically identical isolates from the same hospital suggested the existence of hospital-specific strains. Nine genetically identical isolates from intensive care units (ICU) in our hospital suggested that a unique strain of MRSA was found there. It had not been transmitted from another area. PFGE with cluster analysis seemed to be an essential tool to detect area-specific or hospital-specific strains undifferentiated by phenotyping. These findings confirmed that a combination of PFGE, including cluster analysis along with coagulase-type and beta-lactamase production may provide more detailed information for the epidemiological study of MRSA.     

耐甲氧西林金黄色葡萄球菌肺炎小鼠感染模型的建立与评估

目的 本研究采用临床分离鉴定的ST239型耐甲氧西林金黄葡萄球菌(MRSA)感染BALB/c小鼠,建立小鼠肺炎模型,对小鼠的临床症状、肺载菌量与组织病理学变化进行时相性监测,并用该模型验证万古霉素对小鼠的治疗效果.方法 取35只小鼠随机分成MRSA感染组、药物组和对照组,通过滴鼻方式分别滴入50μL细菌(前两组)与PBS(对照组);感染一天后对药物组用同样的方式滴入万古霉素,CT检测肺部的变化,并对肺载菌量和组织病理学变化进行观察.结果 与对照组比较,CT和细菌计数等结果表明MRSA感染组和药物组的肺组织有明显的炎症反应,载菌量较高;与感染组相比,药物组小鼠肺部的载菌量明显降低,气管和肺部的组织病理学症状明显减轻.结论 本实验结果表明小鼠MRSA肺炎模型成功建立,并可用于药物疗效的比较评估.该模型的建立,将为进一步研究临床分离的MRSA的病原特性、发病机理、治疗方法等,提供可靠的小动物模型.