Macrolide–lincosamide–streptogramin B resistance phenotypes and genotypes among Staphylococcus aureus clinical isolates in Japan

In total, 269 methicillin-resistant Staphylococcus aureus (MRSA) and 434 methicillin-susceptible S. aureus (MSSA) isolates were investigated to determine their macrolide-lincosamide-streptogramin B (MLS(B)) resistance phenotypes and genotypes. The constitutive phenotype (61.3% in MRSA, 1.3% in MSSA) and erm(A) gene predominated among the 261 erythromycin-resistant MRSA isolates, while the inducible phenotype (38.7% in MRSA, 94.0% in MSSA) and erm(C) gene were more prevalent among the 150 erythromycin-resistant MSSA isolates. There was a higher incidence of the MLS(B) inducible phenotype compared with other countries, perhaps because MLS(B) antibiotics are not recommended as first-line agents against S. aureus in Japan.     

A new multiplex PCR for easy screening of methicillin-resistant Staphylococcus aureus SCCmec types I–V

A multiplex PCR with four primer-pairs was designed to identify the five main known SCCmec types. A clear and easily discriminated band pattern was obtained for all five types. The SCCmec type was identified for 98% of 312 clinical isolates of methicillin-resistant Staphylococcus aureus (MRSA). SCCmec type IV was by far the most common SCCmec type among both hospital- and community-acquired MRSA isolates in Denmark.     

Nosocomial vs. community-acquired infective endocarditis in Greece: changing epidemiological profile and mortality risk

Current epidemiological trends of infective endocarditis (IE) in Greece were investigated via a prospective cohort study of all cases of IE that fulfilled the Duke criteria during 2000-2004 in 14 tertiary and six general hospitals in the metropolitan area of Athens. Demographics, clinical data and outcome were compared for nosocomial IE (NIE) and community-acquired IE (CIE). NIE accounted for 42 (21.5%) and CIE for 153 (78.5%) of 195 cases. Intravenous drug use was associated exclusively with CIE, while co-morbidities (cardiovascular disease, diabetes mellitus, chronic renal failure requiring haemodialysis and malignancies) were more frequent in the NIE group (p <0.05). Prosthetic valve endocarditis (PVE) predominated in the NIE group (p 0.006), and >50% of NIE cases had a history of vascular intervention. Coagulase-negative staphylococci and enterococci were more frequent in cases of NIE than in cases of CIE (26.2% vs. 5.2%, p <0.01, and 30.9% vs. 16.3%, p 0.05, respectively). Enterococci accounted for 19.5% of total IE cases and were the leading cause of NIE. Staphylococcus aureus IE was hospital-acquired in only 11.9% of cases. In-hospital mortality was higher for NIE than for CIE (39.5% vs. 18.6%, p 0.02). Cardiac failure (New York Heart Association grade III-IV; OR 13.3, 95% CI 4.9-36.1, p <0.001) and prosthetic valve endocarditis (OR 3.7, 95% CI 1.3-10.6, p 0.01) were the most important predictors of mortality.     

Genetic diversity of community-associated methicillin-resistant Staphylococcus aureus in southern Stockholm, 2000–2005

This study investigated the molecular epidemiology of 104 community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) isolates from southern Stockholm during the period 2000–2005. The isolates were analysed by pulsed-field gel electrophoresis (PFGE), multilocus sequence typing, staphylococcal chromosomal cassette (SCC) mec typing and detection of genes encoding Panton–Valentine leukocidin (PVL). Overall, 28 distinct PFGE patterns and 13 sequence types (STs) were identified. ST80, ST8, ST88 and ST150 were the major CA-MRSA clones in the area, and these accounted for 75% (78/104) of all CA-MRSA isolates. ST150 isolates, which have, to date, been found only in Sweden, were isolated exclusively from a group of homeless individuals. Eighty-six (83%) of the 104 isolates in the study possessed SCC mec IV, found in ten different STs, while 16 isolates possessed SCC mec V. The PVL genes were detected in 56% (58/104) of the isolates. Strain ST80-MRSA-IV carrying PVL genes predominated over the 6-year period and accounted for 38% of all isolates. However, a polyclonal tendency was observed among the CA-MRSA isolates recovered in recent years.     

Prevalence of methicillin-resistant Staphylococcus aureus and factors associated with colonization among residents in community long-term-care facilities in Spain

Hospital-acquired methicillin-resistant Staphylococcus aureus (MRSA) strains are no longer limited to acute-care hospitals but have now spread to other healthcare settings such as long-term-care facilities (LTCFs), in most of which they are endemic. In Europe, few studies have addressed the MRSA situation in LTCFs. A cross-sectional study to determine MRSA prevalence and factors associated with S. aureus carriage in community LTCF residents is reported here. Nasal and decubitus ulcer cultures were performed for residents of nine community LTCFs. Residents were classified as MRSA carriers, methicillin-susceptible S. aureus carriers and non-carriers. Overall, 1377 nasal swabs and 82 decubitus ulcer cultures were performed. MRSA was isolated from 15.5% and 59.0% of the former and latter, respectively. The prevalence of MRSA colonization was 16.8% (95% CI  14.9–18.8), varying from 6.7% to 35.8% (p <0.001) among LTCFs. Several independent variables were related to MRSA colonization. It is noteworthy that residents in an LTCF with fewer than 150 beds had at least a two-fold higher probability of being MRSA carriers. Modifiable factors were medical devices, decubitus ulcers and previous antibiotic treatment. An age of 85 years or older, a Charlson index ≥2 and transfer from an acute-care facility were non-modifiable factors also related to MRSA colonization. A high MRSA prevalence among residents in community LTCFs in Spain, with great variability among facilities, was found. The factors identified as being associated with MRSA colonization could be prevented by the implementation of several measures. Control strategies need to be coordinated between LTCFs and acute-care hospitals.     

耐甲氧西林金黄色葡萄球菌IsdB活性片段的克隆、表达及抗原免疫保护性初步研究

目的探讨耐甲氧西林金黄色葡萄球菌(MRSA)抗原IsdB活性片段(IsdB2)免疫保护作用。方法利用生物信息学技术预测分析出IsdB活性片段(IsdB2),PCR扩增编码IsdB2的基因片段,亚克隆至GST标签融合表达的原核表达载体pGEX-6P-2中,将载体转化入大肠杆菌XL-1 blue,通过IPTG诱导表达IsdB2/GST融合蛋白,利用GST亲和层析初步纯化获取IsdB2蛋白。用IsdB2蛋白抗原辅以氢氧化铝佐剂对小鼠进行免疫实验,统计小鼠存活率对IsdB2抗原的免疫性进行初步研究。结果重组质粒经过BamHⅠ和NotⅠ双酶切鉴定、核酸序列测定和IPTG诱导表达IsdB2/GST及酶切获取IsdB2蛋白的SDS-PAGE分析表明,IsdB2蛋白相对分子质量大小约72 000,GST标签相对分子质量大小约26 000,与预期相符合。用IsdB2蛋白对小鼠进行3次疫苗免疫实验,IsdB2对小鼠的保护率分别为84.6%、50%和60%。结论成功构建重组表达载体pGEX-6P-2-IsdB2,利用大肠杆菌表达系统、GST亲和层析和酶切方法获得IsdB2蛋白抗原,通过3次动物疫苗免疫实验结果表明IsdB2具有免疫保护性,为研制新型有效的MRSA疫苗奠定实验基础。     

NF-κB信号通路蛋白和细胞因子在金黄色葡萄球菌PV杀白细胞素相关肺炎症性损伤中的作用

目的 探讨NF-κB信号通路蛋白和细胞因子在金黄色葡萄球菌PV杀白细胞毒素(PVL)介导的肺炎症性损伤中的变化和作用.方法 取30只新西兰大白兔随机分为2组,每组各15只.rPVL组用重组PVL灌入,正常对照组使用PBS灌人.造模后,于3、6、9h处死兔,每个时间段5只,取肺组织做病理学检查;ELISA方法检测肺组织匀浆IL-6、IL-8、IL-10、TNF-α蛋白含量;免疫组织化学染色检测肺组织中NF-κB p65蛋白.结果 rPVL组兔肺组织病理检查显示有弥漫性炎性细胞浸润、出血、水肿等肺损伤表现;肺组织匀浆中IL-6、IL-8、TNF-α含量随感染时间延长逐渐升高,IL-10含量于9h开始升高;NF-κB p65蛋白活化强度随感染时间延长逐渐增强.结论 NF-κB信号通路蛋白激活及细胞因子大量释放是PVL相关肺损伤重要的发病机制之一,下调肺内NF-κB激活细胞数量有望成为治疗PVL相关肺损伤的途径.     

Apolipoprotein B100 is a suppressor of Staphylococcus aureus‐induced innate immune responses in humans and mice

Plasma lipoproteins such as LDL (low‐density lipoprotein) are important therapeutic targets as they play a crucial role in macrophage biology and metabolic disorders. The impact of lipoprotein profiles on host defense pathways against Gram‐positive bacteria is poorly understood. In this report, we discovered that human serum lipoproteins bind to lipoteichoic acid (LTA) from Staphylococcus aureus and thereby alter the immune response to these bacteria. Size‐exclusion chromatography and solid‐phase‐binding analysis of serum revealed the direct interaction of LTA with apolipoproteins (Apo) B100, ApoA1, and ApoA2. Only ApoB100 and the corresponding LDL exerted biological effects as this binding significantly inhibited LTA‐induced cytokine releases from human and murine immune cells. Serum from hypercholesterolemic mice or humans significantly diminished cytokine induction in response to S. aureus or its LTA. Sera taken from the patients with familial hypercholesterolemia before and after ApoB100‐directed immuno‐apheresis confirmed that ApoB100 inhibited LTA‐induced inflammation in humans. In addition, mice in which LDL secretion was pharmacologically inhibited, displayed significantly increased serum cytokine levels upon infection with S. aureus in vivo. The present study identifies ApoB100 as an important suppressor of innate immune activation in response to S. aureus and its LTA.     

Be alert to the alterations in the biological characteristics in heterogeneous vancomycin-intermediate Staphylococcus aureus

The development of reduced vancomycin susceptibility in Staphylococcus aureus in many cases appears to be associated with characteristic changes. These changes may have pitfall of identifying S. aureus by automated testing methods like Vitek 32. In this study, we retested 24 heterogeneous vancomycin-intermediate Staphylococcus haemolyticus (h-VISH) collected in 2008–2010 at the Department of Clinical Microbiology by conventional biochemical tests and polymerase chain reaction (PCR). The heterogeneous vancomycin-intermediate S. aureus (hVISA) reversion test and electron microscopic examination were also used. Six isolates of 24 h-VISH possessed nuc, coa, and 16S rRNA genes, and could be reversed into S. aureus. It suggested that biochemical and morphological changes in hVISA and vancomycin-intermediate S. aureus (VISA) should be considered, and the detection of S. aureus, especially reduced vancomycin susceptibility isolates, requires more attention and different techniques.