Effect of vancomycin and rifampicin on meticillin-resistant Staphylococcus aureus biofilms

Decolonisation of patients with urinary catheter colonisation by meticillin-resistant Staphylococcus aureus (MRSA) is often difficult. Replacement of the catheter after prophylactic vancomycin administration has been one approach that is often unsuccessful in clinical practice. We suspected that formation of MRSA biofilms might account for the persistence of infection, and our study confirms this, also showing that MRSA is able to colonise a silastic rubber surface even in the presence of prophylactic vancomycin or rifampicin.     

Successful treatment of Staphylococcus epidermidis prosthetic valve endocarditis with linezolid after failure of treatment with oxacillin, gentamicin, rifampicin, vancomycin, and fusidic acid regimens

We present a 49-y-old male, with a history of Marfan's disease and aortic and mitral valve replacement surgery, who was operated for a type III thoracoabdominal aneurysm. The postoperative course was compromised by a Staphylococcus epidermidis mitral valve endocarditis, which was successfully treated only after intravenous linezolid was included in the therapy.     

Efficacy of vancomycin plus rifampin in experimental aortic-valve endocarditis due to methicillin-resistant Staphylococcus aureus: in vitro-in vivo correlations

Studies of in vitro and in vivo bactericidal interactions of vancomycin plus rifampin against Staphylococcus aureus have yielded conflicting results. In this study the efficacy of this drug combination in experimental endocarditis due to a methicillin-resistant strain of S. aureus was investigated. Left-sided endocarditis was induced in 84 rabbits by an infecting strain that had been found to be synergistically killed by vancomycin plus rifampin in vitro when tested by the timed-kill curve technique; in contrast, the checkerboard technique had indicated that the two drugs were antagonistic against this strain. Infected animals received no therapy, vancomycin alone (30 mg/kg per day), rifampin alone (20 mg/kg per day), or both drugs (in the same doses). The combination was significantly more effective than the single-drug regimens in terms of (1) reduction of mean methicillin-resistant S. aureus vegetation titers (P less than .05-.0005), (2) rate and incidence of sterilization of vegetations (P less than .0005), and (3) rate of "radical" cure of endocarditis (P less than .005). Vancomycin alone and vancomycin plus rifampin were equally effective in reducing mortality and sterilizing renal abscesses. The use of vancomycin prevented the in vivo development of resistance to rifampin. No evidence that rifampin exerted an antagonistic effect on the in vivo bactericidal activity of vancomycin was found.     

Clonal spread among Swedish children of a Staphylococcus aureus strain resistant to fusidic acid

An increased incidence of fusidic acid-resistant Staphylococcus aureus strains causing superficial infections among children in Sweden has been noted since the mid-1990s. Based on routine susceptibility testing data from 10 laboratories representing 8/21 Swedish counties during 1990-2001, the increase was first demonstrated in southern Sweden and subsequently became apparent throughout the country. Epidemiological typing using pulsed-field gel electrophoresis of recent isolates of fusidic acid-resistant S. aureus from 11 laboratories representing 8/21 Swedish counties revealed a high degree of similarity of band patterns, indicating a clonal relationship. Data from 1 of the laboratories demonstrated a close connection between this clone and impetigo. Sales statistics showed a pronounced increase in the use of fusidic acid ointments in the 0-12 y age group from 1998 onwards. There was, however, no statistically significant correlation between sales of fusidic acid ointments and resistance among S. aureus strains to fusidic acid.     

Recent advances in the treatment of infections due to resistant Staphylococcus aureus

PURPOSE OF REVIEW: This paper reviews recent data on the treatment of infections caused by drug-resistant Staphylococcus aureus, particularly methicillin-resistant S. aureus (MRSA). This review will focus on new findings reported in the English-language medical literature from June 2003 to September 2004. RECENT FINDINGS: Despite the emergence of resistant and multidrug-resistant S. aureus, we have three effective drugs in clinical use for which little resistance has been observed: quinupristin-dalfopristin, linezolid, and daptomycin. Linezolid looks particularly promising in the treatment of MRSA pneumonia. Daptomycin displays rapid bactericidal activity in vitro, but, so far, clinical trials have only been conducted for the treatment of skin and soft-tissue infections. There are three drugs with broad-spectrum activity against Gram-positive organisms at an advanced stage of testing: two new glycopeptides with potent bacteriocidal activity and long half-lives (oritavancin and dalbavancin), and tigecycline, a minocycline derivative. These drugs have also shown efficacy in the treatment of skin and soft-tissue infections. SUMMARY: The promising data that have emerged in the last year indicate that we may have six available drugs to treat resistant S. aureus infections within the next few years. The next goal is to determine the appropriate indications and cost-effectiveness of each of these drugs in our treatment strategy against S. aureus and other Gram-positive pathogens.     

耐甲氧西林金黄色葡萄球菌对万古霉素敏感性的变迁

目的　通过对近年来耐甲氧西林金黄色葡萄球菌 (MRSA)临床分离株对万古霉素抑菌圈直径的分析 ,研究MRSA对万古霉素敏感性的变化。方法　药敏试验采用纸片扩散法 (K B法 ) ,抑菌圈直径的比较采用t检验。结果　 1994～ 2 0 0 0年每年收集的临床分离的MRSA菌株数分别为 2 18、187、2 92、2 37、35 1、886和 6 5 2 ,各年菌株对万古霉素抑菌圈的平均直径 (mm)分别为 19 9、19 1、18 6、17 4、18 4、18 2和 17 8。 2 0 0 0年的 6 5 2株MRSA对万古霉素抑菌圈的平均直径 (17 8mm)明显小于1994年 2 18株MRSA的平均直径 (19 9mm) ,差异有显著性 (P <0 0 0 1)。 2 0 0 0年分离的MRSA对氯霉素、环丙沙星、红霉素、庆大霉素、四环素和复方新诺明等常用抗生素的耐药率均很高 ,其耐药百分率分别为 44 0 %、73 7%、89 1%、6 5 7%、6 1 0 %和 6 7 0 %。结论　 1994年到 2 0 0 0年MRSA对万古霉素的敏感性在逐年降低 ,加强金黄色葡萄球菌对万古霉素敏感性的监测非常必要。     

Interaction between human monocytes and penicillin G in relation to the antibacterial effect on Staphylococcus aureus

The influence of the presence of monocytes on the effect of penicillin G on Staphylococcus aureus was studied. Conditions were varied in such a way that phagocytosis and intracellular killing of S. aureus by monocytes did not occur, was short lasting and limited, or long lasting and extensive. Synergism between penicillin G and monocytes was observed in the absence of and during limited phagocytosis and intracellular killing by the monocytes. When phagocytosis and intracellular killing were optimal, addition or antagonism between penicillin G and monocytes was observed. Enhancement of the antibacterial effect of penicillin G was also obtained in the presence of monocyte supernatant (the cell-free medium in which monocytes had been incubated for 3 hr). This indicates that monocytes secrete a factor that enhances the antibacterial activity of penicillin G. Serum inhibits the activity of this factor.     

Persistent bacteraemia due to methicillin-resistant Staphylococcus aureus with reduced susceptibility to vancomycin in a patient with erythrodermic psoriasis

A 49-y-old male with erythrodermic psoriasis developed persistent bacteraemia for 3 months due to methicillin-resistant Staphylococcus aureus despite antimicrobial therapy. The skin was the likely focus. Three consecutive isolates from the blood and 1 from the nose were identical and had vancomycin MIC of 4 mg/l.     

In vitro susceptibility of methicillin-resistant Staphylococcus aureus isolates from skin and soft tissue infections to vancomycin,daptomycin, linezolid and tedizolid

Introduction

Treatment of multidrug-resistant Gram-positive infections caused by Staphylococcus aureus remains as a clinical challenge due to emergence of new resistance mechanisms. Tedizolid is a next-generation oxazolidinone, recently approved for skin and soft tissues infections. We conducted a study to determine in vitro susceptibility to vancomycin, daptomycin, linezolid and tedizolid in MRSA clinical isolates from adult patients with skin and soft tissue infections.

Approaches to serious methicillin-resistant Staphylococcus aureus infections with decreased susceptibility to vancomycin: clinical significance and options for management

PURPOSE OF REVIEW: This review addresses therapeutic approaches to Staphylococcus aureus infections with diminished susceptibility to vancomycin, focusing on recently published data in English language medical literature between June 2006 and July 2007. RECENT FINDINGS: Knowledge regarding the potential limitations of vancomycin therapy for S. aureus infections continues to emerge. Recent changes include alteration of the Clinical Laboratory and Standards Institute vancomycin breakpoint for S. aureus and questions regarding the utility of the lower breakpoint of 2.0 mg/l. Interest continues in the accessory gene regulator (agr) locus and its impact on the activity of vancomycin. Newer options for drug therapy progress, with strengths and limitations becoming more apparent for each. SUMMARY: Newer antimicrobial agents active against methicillin-resistant S. aureus such as daptomycin and linezolid continue to show value. Older antimicrobial agents may play an important therapeutic role and warrant further examination. Work is needed to evaluate current agents against methicillin-resistant S. aureus in the setting of elevated vancomycin minimum inhibitory concentrations or clinical failure. Antimicrobial selection for methicillin-resistant S. aureus infections with reduced susceptibility to vancomycin should be governed by disease severity, susceptibility patterns, knowledge of the limitations of current susceptibility testing, and strengths and weaknesses of the agents being considered.