Management of methicillin-resistant Staphylococcus aureus pneumonia

Control of Methicillin-Resistant Staphylococcus aureus Pneumonia Utilizing TLR2 Agonist Pam3CSK4

The spread of methicillin-resistant Staphylococcus aureus (MRSA) is a critical health issue that has drawn greater attention to the potential use of immunotherapy. Toll-like receptor 2 (TLR2), a pattern recognition receptor, is an essential component in host innate defense system against S. aureus infection. However, little is known about the innate immune response, specifically TLR2 activation, against MRSA infection. Here, we evaluate the protective effect and the mechanism of MRSA murine pneumonia after pretreatment with Pam3CSK4, a TLR2 agonist. We found that the MRSA-pneumonia mouse model, pretreated with Pam3CSK4, had reduced bacteria and mortality in comparison to control mice. As well, lower protein and mRNA levels of TNF-α, IL-1β and IL-6 were observed in lungs and bronchus of the Pam3CSK4 pretreatment group. Conversely, expression of anti-inflammatory cytokine IL-10, but not TGF-β, increased in Pam3CSK4-pretreated mice. Our additional studies showed that CXCL-2 and CXCL1, which are necessary for neutrophil recruitment, were less evident in the Pam3CSK4-pretreated group compared to control group, whereas the expression of Fcγ receptors (FcγⅠ/Ⅲ) and complement receptors (CR1/3) increased in murine lungs. Furthermore, we found that increased survival and improved bacterial clearance were not a result of higher levels of neutrophil infiltration, but rather a result of enhanced phagocytosis and bactericidal activity of neutrophils in vitro and in vivo as well as increased robust oxidative activity and release of lactoferrin. Our cumulative findings suggest that Pam3CSK4 could be a novel immunotherapeutic candidate against MRSA pneumonia.

Staphylococcus aureus screening and decolonization in orthopaedic surgery and reduction of surgical site infections

BACKGROUND

Staphylococcus aureus is the most common organism responsible for orthopaedic surgical site infections (SSIs). Patients who are carriers for methicillin-sensitive S. aureus or methicillin-resistant S. aureus (MRSA) have a higher likelihood of having invasive S. aureus infections. Although some have advocated screening for S. aureus and decolonizing it is unclear whether these efforts reduce SSIs.

QUESTIONS/PURPOSES

The purposes of this study were to determine (1) whether S. aureus screening and decolonization reduce SSIs in orthopaedic patients and (2) if implementing this protocol is cost-effective.

METHODS

Studies for this systematic review were identified by searching PubMed, which includes MEDLINE (1946-present), EMBASE.com (1974-present), and the Cochrane Library's (John Wiley & Sons) Cochrane Database of Systematic Reviews (CDSR), Cochrane Central Register of Controlled Trials (CENTRAL), Database of Abstracts of Reviews of Effects (DARE), Health Technology Assessment Database (HTAD), and the NHS Economic Evaluation Database (NHSEED). Comprehensive literature searches were developed using EMTREE, MeSH, and keywords for each of the search concepts of decolonization, MRSA, and orthopedics/orthopedic surgery. Studies published before 1968 were excluded. We analyzed 19 studies examining the ability of the decolonization protocol to reduce SSIs and 10 studies detailing the cost-effectiveness of S. aureus screening and decolonization.

RESULTS

All 19 studies showed a reduction in SSIs or wound complications by instituting a S. aureus screening and decolonization protocol in elective orthopaedic (total joints, spine, and sports) and trauma patients. The S. aureus screening and decolonization protocol also saved costs in orthopaedic patients when comparing the costs of screening and decolonization with the reduction of SSIs.

CONCLUSIONS

Preoperative screening and decolonization of S. aureus in orthopaedic patients is a cost-effective means to reduce SSIs.

LEVEL OF EVIDENCE

Level IV, systematic review of Level I-IV studies. See the Guidelines for Authors for a complete description of levels of evidence.

Differences in hospital- and ventilator-associated pneumonia due to Staphylococcus aureus (methicillin-susceptible and methicillin-resistant) between Europe and Latin America: a comparison of the EUVAP and LATINVAP study cohorts

PURPOSE

A comparison is made of epidemiological variables (demographic and clinical characteristics) and outcomes in patients with hospital-acquired pneumonia (HAP) or ventilator-associated pneumonia (VAP) caused by methicillin-susceptible and methicillin-resistant Staphylococcus aureus (MSSA and MRSA) in the Latin American VAP (LATINVAP) vs. the European Union VAP (EUVAP) cohorts of patients admitted to intensive care units (ICUs).

METHODS

The EUVAP project was a prospective, multicenter observational study reporting 827 patients with HAP/VAP in 27 ICUs from 9 European countries. The LATINVAP project was a multicenter prospective observational study, with an identical design, performed in 17 ICUs from 4 Latin American countries involving 99 patients who developed HAP/VAP. Episodes of VAP/HAP caused by S. aureus, MSSA, and MRSA were compared in both cohorts.

RESULTS

Forty-five patients had S. aureus HAP/VAP in the EUVAP cohort vs. 11 patients in the LATINVAP cohort. More patients had MRSA in the LATINVAP study than in the EUVAP (45% vs. 33%). ICU mortality among patients with MSSA HAP/VAP in EUVAP was 10% vs. 50% for LATINVAP (OR=9.75, p=0.01). Fifteen patients in the EUVAP cohort developed MRSA HAP/VAP as opposed to 5 in LATINVAP. In the EUVAP study there was an ICU mortality rate of 33.3%. In the LATINVAP cohort, the ICU mortality rate was 60% (OR for death=3.0; 95%CI 0.24-44.7).

CONCLUSION

MRSA pneumonia was associated with poorer outcomes in comparison with MSSA. Our study suggests significant variability among European and Latin American ICU practices that may influence clinical outcomes. Furthermore, patients with pneumonia in Latin America have different outcomes.

Retracted publications in the drug literature

Recent studies have suggested an increase in the number of retracted scientific publications. It is unclear how broadly the issue of misleading and fraudulent publications pertains to retractions of drug therapy studies. Therefore, we sought to determine the trends and factors associated with retracted publications in drug therapy literature. A PubMed search was conducted to identify retracted drug therapy articles published from 2000-2011. Articles were grouped according to reason for retraction, which was classified as scientific misconduct or error. Scientific misconduct was further divided into data fabrication, data falsification, questions of data veracity, unethical author conduct, and plagiarism. Error was defined as duplicate publication, scientific mistake, journal error, or unstated reasons. Additional data were extracted from the retracted articles, including type of article, funding source, author information, therapeutic area, and retraction issue. A total of 742 retractions were identified from 2000-2011 in the general biomedical literature, and 102 drug studies met our inclusion criteria. Of these, 73 articles (72%) were retracted for a reason classified as scientific misconduct, whereas 29 articles (28%) were retracted for error. Among the 73 articles classified as scientific misconduct, those classified as unethical author conduct (32 articles [44%]) and data fabrication (24 articles [33%]) constituted the majority. The median time from publication of the original article to retraction was 31 months (range 1-130). Fifty percent of retracted articles did not state a funding source, whereas pharmaceutical manufacturer funding accounted for only 13 articles (13%) analyzed. Many retractions were due to repeat offenses by a small number of authors, with nearly 40% of the retracted studies associated with two individuals. We found that a greater proportion of drug therapy articles were retracted for reasons of misconduct and fraud compared with other biomedical studies. It is important for health care practitioners to monitor the literature for retractions so that recommendations for drug therapy and patient management may be modified accordingly.

ROS-mediated killing efficiency with visible light of bacteria carrying different red fluorochrome proteins

Red fluorescent proteins can generate reactive oxygen species (ROS) if their fluorochrome is stimulated e.g. by visible light illumination. ROS compounds have very reactive, highly toxic properties leading to cell damage which results in cell killing. In this context, the toxicity of the various red fluorochromes KillerRed, DsRed2, mCherry, and mRFP expressed in Escherichia coli bacteria was tested after illumination with white light. The toxic effect was determined by measurement of the colony forming ability 24h after transfection and illumination. KillerRed was found to be the most harmful, followed by mRFP and DsRed2 while bacteria expressing mCherry and controls without fluorescent proteins survived after application of identical illumination doses. Their application and a possible bactericide role is discussed.

Usefulness of linezolid in the treatment of hospital-acquired pneumonia caused by MRSA: a prospective observational study

Clinical results for linezolid (LZD) treatment of hospital-acquired pneumonia (HAP) caused by methicillin-resistant Staphylococcus aureus (MRSA), particularly microbiologically evaluable or severe cases, are limited in Japan. A prospective observational study was conducted in order to assess the usefulness of LZD in Japanese patients with MRSA pneumonia. The study tracked fifteen participants treated with LZD for pneumonia who met the criteria of the HAP guidelines and were confirmed to have pneumonia caused by MRSA. Of these, six were severe and 13 had received antibiotic treatment before treatment with LZD. Of the 13 participants assessed for their clinical responses, seven were rated as cures, three were rated as failures, and three were indeterminate. The overall cure rate (cure/cure + failure) was 70.0% (7/10), and the cure rate by severity was 33.3% (1/3) for severe cases and 85.5% (6/7) for moderate cases. The one severe case with a clinical response rating of cure had failed to respond to vancomycin. Among the seven participants with a clinical response rating of cure, the microbiological response was eradication in three, presumed eradication in three, and indeterminate in one. Three serious adverse events occurred in two of the 15 participants, but none were considered to be causally related to LZD. The results suggest that LZD has high potential for severe and multidrug-resistant cases. A higher cure rate was achieved in moderate cases. In cases of pneumonia that are most likely MRSA infections with poor prognosis, it was suggested to be important for patient outcome to implement the most effective therapy before the patient's condition becomes serious.

Controlling the Evolution of Resistance

Evolution has long been understood as the driving force for many problems of medical interest. The evolution of drug resistance in HIV and bacterial infections is recognized as one of the most significant emerging problems in medicine. In cancer therapy, the evolution of resistance to chemotherapeutic agents is often the differentiating factor between effective therapy and disease progression or death. Interventions to manage the evolution of resistance have, up to this point, been based on steady-state analysis of mutation and selection models. In this paper, we review the mathematical methods applied to studying evolution of resistance in disease. We present a broad review of several classical applications of mathematical modeling of evolution, and review in depth two recent problems which demonstrate the potential for interventions which exploit the dynamic behavior of resistance evolution models. The first problem addresses the problem of sequential treatment failures in HIV; we present a review of our recent publications addressing this problem. The second problem addresses a novel approach to gene therapy for pancreatic cancer treatment, where selection is used to encourage optimal spread of susceptibility genes through a target tumor, which is then eradicated during a second treatment phase. We review the recent in Vitro laboratory work on this topic, present a new mathematical model to describe the treatment process, and show why model-based approaches will be necessary to successfully implement this novel and promising approach.