Infectious Diseases: Pharmacologic Treatment Options for Nosocomial Pneumonia Involving Methicillin-Resistant Staphylococcus aureus

Objective:

To discuss current and potential treatment options for nosocomial pneumonia due to methicillin-resistant Staphylococcus aureus (MRSA).

Data Sources:

A MEDLINE search (1966–January 2007) was conducted to identify English-language literature on pharmacotherapy of nosocomial pneumonia and the bibliographies of pertinent articles. Programs and abstracts from infectious disease meetings were also searched. Search terms included MRSA, nosocomial pneumonia, pulmonary infections, vancomycin, quinupristin/dalfopristin, linezolid, daptomycin, tigecycline, dalbavancin, oritavancin, and ceftobiprole.

Data Selection and Data Extraction:

All articles were critically evaluated and all pertinent information was included in this review.

Data Synthesis:

Vancomycin has been the drug of choice for MRSA infections for many years. Recent data suggest that linezolid may be superior to vancomycin in the treatment of MRSA nosocomial pneumonia. However, there are limitations to the available data. Therefore, prospective, randomized studies are needed before linezolid is recommended as the preferred first-line therapy. Other approved agents for nosocomial MRSA infections, such as quinupristin/dalfopristin and daptomycin, should not be used in the treatment of MRSA pneumonia, as they were inferior in clinical trials. Tigecycline has excellent activity against MRSA in vitro, but should not be routinely used for the treatment of MRSA pneumonia, as clinical data are lacking. In a Phase III clinical trial, an anti-MRSA cephalosporin, ceftobiprole, is being evaluated for effectiveness against nosocomial pneumonia. Investigational glycopeptides may eventually have a role in the treatment of nosocomial pneumonia, but data are currently lacking.

Conclusions:

Vancomycin is still the drug of choice for treatment of MRSA pneumonia, and linezolid should be used as an alternative agent. Linezolid should carry strong consideration for patients with vancomycin-induced nephrotoxicity or a documented lack of response to vancomycin. Tigecycline and investigational agents with activity against MRSA may be future options for nosocomial pneumonia due to MRSA.

Rifaximin for treatment of hepatic encephalopathy

OBJECTIVE

To review the effectiveness and safety of rifaximin in the treatment of hepatic encephalopathy (HE).

DATA SOURCES

MEDLINE (1990-October 2008) was searched using the terms rifaximin, rifamycins, hepatic encephalopathy, liver cirrhosis, and acute liver failure. Other sources included the bibliographies of pertinent articles as well as programs and abstracts from infectious diseases and gastrointestinal diseases meetings.

STUDY SELECTION AND DATA EXTRACTION

All English-language articles identified from the search were evaluated. All primary literature that addressed the efficacy and safety of rifaximin in the treatment of HE was included in this review.

DATA SYNTHESIS

HE is a complex neuropsychiatric syndrome seen in patients with liver failure. It is characterized by disturbances in consciousness and behavior, personality changes, fluctuating neurologic signs, asterixis, and electroencephalographic changes. Although the etiology of HE is unknown, the accumulation of several gut-derived toxins such as mercaptans, ammonia, and benzodiazepine has been implicated. Current treatment options for HE include agents that reduce the concentration of these toxins, such as nonabsorbable disaccharides and antibiotics. Several studies have evaluated the use of rifaximin in the treatment of HE. They include a dose-finding study, 9 open-label studies, and 4 double-blind studies comparing rifaximin with either nonabsorbable disaccharides or antibiotics. Commonly used outcomes in most of these studies were changes in portal systemic encephalopathy index and the improvement in HE grade. Despite various limitations of the studies, rifaximin showed superior efficacy compared with lactulose for the treatment of HE, similar efficacy to paromomycin, and similar or greater efficacy than neomycin. Rifaximin was found to be associated with fewer hospitalizations, fewer days of hospitalization, and lower hospitalization charges than were seen with lactulose. Rifaximin also had a better tolerance profile than the comparative agents.

CONCLUSIONS

Rifaximin appears to be an effective and safe treatment option for HE. Better-designed studies are needed to characterize its efficacy in the treatment of HE.

Case-control study of the relationship between MRSA bacteremia with a vancomycin MIC of 2 microg/mL and risk factors, costs, and outcomes in inpatients undergoing hemodialysis

BACKGROUND

An increased prevalence of bacteremia caused by methicillin-resistant Staphylococcus aureus (MRSA) with a vancomycin hydrochloride MIC of 2 microg/mL was noted in a population of inpatients undergoing hemodialysis at Baptist Memorial Health Care, Memphis, Tennessee.

OBJECTIVES

The aims of this study were to determine risk factors for infection with MRSA and to assess the differences in clinical and economic outcomes in patients undergoing hemodialysis with MRSA bacteremia with vancomycin MIC 2 microg/mL versus those with MRSA bacteremia with vancomycin MIC < or =0.5 microg/mL and uninfected controls.

METHODS

This retrospective case-control study was conducted at Baptist Memorial Health Care. The study population (inpatients undergoing hemodialysis for MRSA bacteremia with vancomycin MIC 2 microg/mL [high-MIC group], MIC < or = 0.5 microg/mL [low-MIC group], and uninfected controls) was identified. Risk factors and clinical and economic outcomes (costs of hospitalization, nursing, and pharmacy) were determined and compared using univariate and multivariate statistics.

RESULTS

Fifty patients with MRSA bacteremia undergoing hemodialysis were identified during the study period (high-MIC group, 17 [11 women, 6 men; mean (SD) age, 60 (17) years]; low-MIC group, 33 [23 women, 10 men; mean (SD) age, 62 (14) years]) and matched with 100 uninfected controls (57 men, 43 women; mean [SD] age, 63 [15] years). Risk factors for MRSA bacteremia found to be associated with high MIC included female sex, higher body mass index (1-point increments), recent surgery, and a history of cardiovascular disease (P < 0.05, P < 0.046, P = 0.04, and P = 0.028, respectively) (multivariate analysis). In the outcomes analysis, mortality was significantly higher in the high-MIC group compared with those in the low-MIC and control groups (35% vs 24% and 15%, respectively; P = 0.022). Total mean (SD) hospitalization costs were significantly higher in the high-MIC group compared with those in the low-MIC group and controls (US $47,624 [$80,534] vs $26,792 [$25,167] and $13,185 [$15,568], respectively; P < 0.001). Nursing costs were almost 6-fold higher in both infected groups compared with those in controls. Pharmacy costs in the low- and high-MIC groups were 3- to 6-fold higher, respectively, compared with those in controls.

CONCLUSIONS

Surgery within the previous 6 months and intensive care unit admission were identified as significant risk factors for patients with MRSA bacteremia with a vancomycin MIC 2 microg/mL undergoing hemodialysis. These patients experienced a longer mean hospital length of stay and increased hospital costs compared with patients with MRSA bacteremia with a vancomycin MIC < or =0.5 microg/mL and uninfected controls.