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

A Retrospective Analysis of the Effect of Tigecycline on Coagulation Function

A number of clinical trials demonstrated that tigecycline was effective and well tolerated in the treatment of patients with various bacterial infections, but few literatures had shown the coagulopathy induced by tigecycline. To address this concern, we performed a retrospective analysis to assess the impact of tigecycline treatment on coagulation parameters in 50 patients with bacterial infections in our hospital (Shandong Provincial Hospital, China). These patients were treated with tigecycline at Shandong Provincial Hospital in 2015-2016 at either a recommended (50 mg q12h) or a higher dose (100 mg q12h). Coagulation parameters, including Fibrinogen (FIB) levels, prothrombin time (PT), activated partial thromboplastin time (aPTT), platelet count (PLT) and D-dimer, were evaluated in order to assess the impact of tigecycline treatment in these severely infected patients. What we found was that the plasma fibrinogen (FIB) level was 4.63 ± 1.56 g/L before tigecycline treatment, and decreased to 2.92 ± 1.23 g/L during treatment, which was statistically significant (p < 0.001). The mean values of aPTT and PT were significantly increased from 39.58 ± 8.72 to 44.05 ± 10.45 s (p = 0.002), and from 15.37 ± 1.53 to 16.37 ± 2.64 s (p = 0.004), respectively. This study demonstrates that treatment of tigecycline could reduce FIB, prolong aPTT and PT. In conclusion, we advise that it is necessary for practitioners routinely monitor coagulation level in at-rick patient populations treated with tigecycline.

Infectious pleural effusion status and treatment progress

Pleural cavity infection continuously seriously threatens human health with continuous medical progress. From the perspective of pathophysiology, it can be divided into three stages: exudative stage, fibrin exudation and pus formation stage, and organization stage. Due to the pathogenic bacteria difference of pleural cavity infection and pulmonary infection, it is very important for disease treatment to analyze the bacteria and biochemical characteristics of the infectious pleural effusion. Most prognoses of patients have been relatively good, while for some patients, the complicated parapneumonic effusion or empyema could be evolved. Antibiotic treatment and sufficient drainage are the foundation for this treatment. No evidence can support the routine use of a fibrin agent. However, it has been reported that the plasminogen activator and deoxyribonuclease can be recommended to be applied in the pleural cavity. In case of failure on conservative medical treatment, operative treatment can be applied such as thoracoscopy and pleural decortication. According to the clinical characteristics of these patients, it is a key to research prognosis, as well as early evaluation and stratification, in the future.

Methicillin-resistant Staphylococcus aureus pneumonia in adults

Methicillin-resistant Staphylococcus aureus (MRSA) has become one of the leading etiologies of nosocomial pneumonia as a result of an increase in staphylococcal infections caused by methicillin-resistant strains paired with extended ventilatory support of critically, and often, chronically ill patients. The prevalence of community-acquired MRSA pneumonia, which historically affects younger patients and is often preceded by an influenza-like illness, is also increasing. A high index of suspicion and early initiation of appropriate antibiotics are key factors for the successful treatment of this disease. Even with early diagnosis and appropriate treatment, MRSA pneumonia still carries an unacceptably high mortality rate. This article will review historical differences between hospital-acquired and community-acquired MRSA pneumonia, as well as, clinical features of, diagnosis and treatment of MRSA pneumonia.

Vancomycin and nephrotoxicity: just another myth?

BACKGROUND

Vancomycin is considered the drug of choice for methicillin-resistant Staphylococcus aureus infection; however, it has also been linked with nephrotoxicity in the past, sometimes leading to its substitution with linezolid. We hypothesized that patients treated with vancomycin for gram-positive (GP) infections would have an increased incidence of rise in creatinine and need for hemodialysis (HD) compared with patients receiving linezolid.

METHODS

This was a retrospective cohort study of a prospectively maintained database of all surgical patients treated with either vancomycin or linezolid for GP infections in a single intensive care unit from 2001 to 2008 and managed under a cycling antibiotic protocol. Patients were followed up until hospital discharge. Categorical and continuous variables were evaluated. Multivariable logistic regression was performed.

RESULTS

A total of 545 patients were treated for 1,046 GP infections (571 with vancomycin, 475 with linezolid) over 7 years. Patient demographics were similar between groups; however, the vancomycin group was associated with a longer treatment course (16.2 [0.5] days vs. 14.3 [0.5] days; p = 0.022). Unadjusted outcomes were similar between groups. Multivariable analysis revealed that Acute Physiology and Chronic Health Evaluation II score predicted an increase in creatinine levels greater than 1.0 following antibiotic therapy (relative risk [RR], 3.01; 95% confidence interval [CI], 1.22-7.42) and subsequent need for HD (RR, 3.07; 95% CI, 1.23-7.62). In addition, initial creatinine level predicted an increase in creatinine levels greater than 1.0 following antibiotic therapy (RR, 4.36; 95% CI, 1.46-12.99) and subsequent need for HD (RR, 10.83; 95% CI, 3.19-36.77). Linezolid was found to be protective regarding rise in creatinine levels greater than 1.0 following antibiotic therapy; however, this was only experienced when vancomycin trough levels greater than 20 were encountered (RR, 5.4;95% CI, 1.19-24.51).

CONCLUSION

These data suggest that vancomycin is minimally nephrotoxic and has a similar nephrotoxic profile as compared with linezolid when appropriate dosing is used, even among critically ill patients with complex infections.

LEVEL OF EVIDENCE

Therapeutic/care management, level II.

Daptomycin Failure for Treatment of Pulmonary Septic Emboli in Native Tricuspid and Mitral Valve Methicillin-Resistant Staphylococcus aureus Endocarditis

Daptomycin has been used with success for the treatment of right-sided methicillin-resistant Staphylococcus aureus (MRSA) endocarditis. However, its efficacy has not been completely assessed for the treatment of MRSA endocarditis when it is associated with pulmonary septic emboli. Hereby, we present a case of MRSA mitral and tricuspid native valve endocarditis with pulmonary septic emboli, which was treated with daptomycin as a sole agent, resulting in worsening pulmonary infiltrates and treatment failure.

Successful treatment of right-sided native valve methicillin-resistant Staphylococcus aureus endocarditis and septicaemia with teicoplanin and rifampicin: a case report

Vancomycin is the drug of choice in the treatment of methicillin-resistant Staphylococcus aureus (MRSA) infection. However, the presence of certain clinical complications like renal failure alters vancomycin pharmacokinetics, leading to drug accumulation and toxicity. This highlights the need to identify an effective substitute for treating MRSA infections when vancomycin cannot be used. We report the case of a 57-y-old Indian male diagnosed with tricuspid valve endocarditis with septicaemia and a right upper lobe cavity caused by MRSA. The patient also presented with renal failure, which precluded the use of vancomycin for treatment. A 6-week regimen of teicoplanin and rifampicin was used instead, and the infection was successfully treated. This case report provides evidence of the effectiveness of teicoplanin and rifampicin in the treatment of MRSA bacteraemia in situations where the use of vancomycin is contraindicated.

New approaches for treating staphylococcal biofilm infections

Bacteria of the genus Staphylococcus are a prominent cause of acute and chronic infections. The ability of the staphylococci to establish biofilms has been linked to the persistence of chronic infections, which has drawn considerable interest from researchers over the past decade. Biofilms can be defined as sessile communities of surface-attached cells encased in an extracellular matrix, and treatment of bacteria in this mode of growth is challenging due to the resistance of biofilm structures to both antimicrobials and host defenses. In this review of the literature, we introduce Staphylococcus aureus and Staphylococcus epidermidis biofilms and summarize current antibiotic treatment approaches for staphylococcal biofilm infections. We also review recent studies on alternative strategies for preventing biofilm formation and dispersing established biofilms, including matrix-degrading enzymes, small-molecule approaches, and manipulation of natural staphylococcal disassembly mechanisms. While research on staphylococcal biofilm development is still in its early stages, new discoveries in the field hold promise for improved therapies that target staphylococcal biofilm infections.

Cochrane meta-analysis: teicoplanin versus vancomycin for proven or suspected infection

ABSTRACT Objective: To compare efficacy and safety of vancomycin versus teicoplanin in patients with proven or suspected infection. Methods: Data Sources: Cochrane Renal Group's Specialized Register, CENTRAL, MEDLINE, EMBASE, nephrology textbooks and review articles. Inclusion criteria: Randomized controlled trials in any language comparing teicoplanin to vancomycin for patients with proven or suspected infection. Data extraction: Two authors independently evaluated methodological quality and extracted data. Study investigators were contacted for unpublished information. A random effect model was used to estimate the pooled risk ratio (RR) with 95% confidence interval (CI). Results: A total of 24 studies (2,610 patients) were included. The drugs had similar rates of clinical cure (RR: 1.03; 95%CI: 0.98-1.08), microbiological cure (RR: 0.98; 95%CI: 0.93-1.03) and mortality (RR: 1.02; 95%CI: 0.79-1.30). Teicoplanin had lower rates of skin rash (RR: 0.57; 95%CI: 0.35-0.92), red man syndrome (RR: 0.21; 95%CI: 0.08-0.59) and total adverse events (RR: 0.73; 95%CI: 0.53-1.00). Teicoplanin reduced the risk of nephrotoxicity (RR: 0.66; 95%CI: 0.48-0.90). This effect was consistent for patients receiving aminoglycosides (RR: 0.51; 95%CI: 0.30-0.88) or having vancomycin doses corrected by serum levels (RR: 0.22; 95%CI: 0.10-0.52). There were no cases of acute kidney injury needing dialysis. Limitations: Studies lacked a standardized definition for nephrotoxicity. Conclusions: Teicoplanin and vancomycin are equally effective; however the incidence of nephrotoxicity and other adverse events was lower with teicoplanin. It may be reasonable to consider teicoplanin for patients at higher risk for acute kidney injury.

PEGylated liposome encapsulation increases the lung tissue concentration of vancomycin

Pneumonia due to methicillin-resistant Staphylococcus aureus (MRSA) often cannot be cured by vancomycin treatment. Poor lung tissue and intracellular penetration limits the ability to achieve effective bactericidal levels, particularly in alveolar macrophages, where MRSA can evade phagocytic killing. Compared to standard formulations, liposome encapsulation has been shown to enhance vancomycin intracellular killing of MRSA. In this murine pharmacokinetic and biodistribution study, PEGylated liposomal vancomycin, compared to standard and non-PEGylated formulations, significantly prolonged blood circulation time and increased deposition in lung, liver, and spleen and yet reduced accumulation in kidney tissue. As a result of optimizing antimicrobial targeting of infected lung tissue and limiting renal parenchymal exposure, administration of PEGylated liposomal vancomycin may improve the efficacy of treatment of MRSA pneumonia and reduce the risk of nephrotoxicity.

Efficacy and safety of tigecycline for the treatment of infectious diseases: a meta-analysis

BACKGROUND

Multidrug resistance among bacteria increases the need for new antimicrobial drugs with high potency and stability. Tigecycline is one candidate drug, and a previous meta-analysis of only published randomised controlled trials suggested that it might as effective as comparator treatments; we did a meta-analysis to include new and unpublished trials to assess its efficacy for the treatment of adult patients with serious bacterial infection.

METHODS

We searched PubMed, Cochrane Central Register, and Embase up to March 30, 2011, to identify published studies, and we searched clinical trial registries to identify completed unpublished studies, the results of which were obtained through the manufacturer. Eligible studies were randomised trials assessing the clinical efficacy, safety, and eradication efficiency of tigecycline versus other antimicrobial agents for any bacterial infection. The primary outcome was treatment success in patients who received at least one dose of the study drug, had clinical evidence of disease, and had complete follow-up (the clinically assessable population). Meta-analysis was done with random-effects models because of heterogeneity across the trials.

FINDINGS

14 randomised trials, comprising about 7400 patients, were included. Treatment success was lower with tigecycline than with control antibiotic agents, but the difference was not significant (odds ratio 0·87, 95% CI 0·74-1·02). Adverse events were more frequent in the tigecycline group than in the control groups (1·45, 1·11-1·88), with significantly more vomiting and nausea. All-cause mortality was higher in the tigecycline group than in the comparator groups, but the difference was not significant (1·28, 0·97-1·69). Eradication efficiency did not differ between tigecycline and control regimens, but the sample size for these comparisons was small.

INTERPRETATION

Tigecycline is not better than standard antimicrobial agents for the treatment of serious infections. Our findings show that assessment with unpublished studies is needed to make appropriate decisions about new agents.

FUNDING

None.

Whole genome sequencing and complete genetic analysis reveals novel pathways to glycopeptide resistance in Staphylococcus aureus

The precise mechanisms leading to the emergence of low-level glycopeptide resistance in Staphylococcus aureus are poorly understood. In this study, we used whole genome deep sequencing to detect differences between two isogenic strains: a parental strain and a stable derivative selected stepwise for survival on 4 µg/ml teicoplanin, but which grows at higher drug concentrations (MIC 8 µg/ml). We uncovered only three single nucleotide changes in the selected strain. Nonsense mutations occurred in stp1, encoding a serine/threonine phosphatase, and in yjbH, encoding a post-transcriptional negative regulator of the redox/thiol stress sensor and global transcriptional regulator, Spx. A missense mutation (G45R) occurred in the histidine kinase sensor of cell wall stress, VraS. Using genetic methods, all single, pairwise combinations, and a fully reconstructed triple mutant were evaluated for their contribution to low-level glycopeptide resistance. We found a synergistic cooperation between dual phospho-signalling systems and a subtle contribution from YjbH, suggesting the activation of oxidative stress defences via Spx. To our knowledge, this is the first genetic demonstration of multiple sensor and stress pathways contributing simultaneously to glycopeptide resistance development. The multifactorial nature of glycopeptide resistance in this strain suggests a complex reprogramming of cell physiology to survive in the face of drug challenge.

Comparison of tigecycline with imipenem/cilastatin for the treatment of hospital-acquired pneumonia

To compare efficacy and safety of a tigecycline regimen with an imipenem/cilastatin regimen in hospital-acquired pneumonia patients, a phase 3, multicenter, randomized, double-blind, study evaluated 945 patients. Coprimary end points were clinical response in clinically evaluable (CE) and clinical modified intent-to-treat (c-mITT) populations at test-of-cure. Cure rates were 67.9% for tigecycline and 78.2% for imipenem (CE patients) and 62.7% and 67.6% (c-mITT patients), respectively. A statistical interaction occurred between ventilator-associated pneumonia (VAP) and non-VAP subgroups, with significantly lower cure rates in tigecycline VAP patients compared to imipenem; in non-VAP patients, tigecycline was noninferior to imipenem. Overall mortality did not differ between the tigecycline (14.1%) and imipenem regimens (12.2%), although more deaths occurred in VAP patients treated with tigecycline than imipenem. Overall, the tigecycline regimen was noninferior to the imipenem/cilastatin regimen for the c-mITT but not the CE population; this difference appears to have been driven by results in VAP patients.

Ceftobiprole: A novel, broad-spectrum cephalosporin with activity against methicillin-resistant Staphylococcus aureus

PURPOSE

The pharmacology, antimicrobial activity, pharmacokinetics, pharmacodynamics, clinical efficacy, safety, and place in therapy of ceftobiprole are reviewed.

SUMMARY

Ceftobiprole, a novel, broad-spectrum, parenteral cephalosporin, inhibits the cell-wall synthesis of penicillin-binding proteins (PBPs) PBP2a and PBP2x, responsible for the resistance in staphylococci and pneumococci, respectively. Ceftobiprole has good activity against gram-positive aerobes and anaerobes, and its activity against gram-negative aerobes and anaerobes is species dependent. Ceftobiprole is relatively inactive against Acinetobacter species. Its ability to bind relevant PBPs of resistant gram-positive and gram-negative bacteria indicates its potential use in the treatment of hospital-acquired pneumonia and complicated skin and skin-structure infections (cSSSIs). Ceftobiprole is primarily excreted unchanged by the kidneys and exhibits linear pharmacokinetics. The half-life of the drug is approximately 3-4 hours. It exhibits minimal plasma protein binding (16%). Ceftobiprole does not inhibit the cytochrome P-450 isoenzyme system, so the possibility of drug-drug interactions is low. The drug has not been approved for use in the United States but has been approved in Canada and elsewhere. Ceftobiprole is currently undergoing Phase III clinical trials and has demonstrated activity against methicillin-resistant Staphylococcus aureus, penicillin-resistant Streptococcus pneumoniae, and Pseudomonas aeruginosa. Completed Phase III trials used i.v. dosages of 500 mg every 8-12 hours. The most commonly observed adverse effects of ceftobiprole included headache and gastrointestinal upset.

CONCLUSION

Ceftobiprole is a novel, broad-spectrum, parenteral cephalosporin undergoing Phase III clinical trials. Its broad spectrum of activity makes it a candidate for monotherapy of cSSSIs and pneumonias that have required combination therapy in the past.

Teicoplanin versus vancomycin for proven or suspected infection

BACKGROUND

Vancomycin and teicoplanin are commonly used to treat gram-positive infections, particularly those caused by methicillin-resistant Staphylococcus aureus (MRSA). There is uncertainty regarding the effects of teicoplanin compared to vancomycin on kidney function with some previous studies suggesting teicoplanin is less nephrotoxic than vancomycin.

OBJECTIVES

To investigate the efficacy and safety of vancomycin versus teicoplanin in patients with proven or suspected infection.

SEARCH STRATEGY

We searched the Cochrane Renal Group's Specialised Register, CENTRAL, MEDLINE, EMBASE, reference lists of nephrology textbooks, review articles with relevant studies and sent letters seeking information about unpublished or incomplete studies to investigators involved in previous studies.

SELECTION CRITERIA

We searched for randomised controlled trials (RCTs) in any language comparing teicoplanin to vancomycin for patients with proven or suspected infection.

DATA COLLECTION AND ANALYSIS

Two authors independently evaluated methodological quality and extracted data using standardised data extraction forms. Study investigators were contacted for information not available in the original manuscripts. Random effects model was used to estimate the pooled risk ratio (RR) with 95% confidence interval (CI).

MAIN RESULTS

We included 24 studies (2,610 patients) in this review. Teicoplanin reduced the risk of nephrotoxicity compared to vancomycin (RR 0.66, 95% CI 0.48 to 0.90).The effects of teicoplanin or vancomycin were similar for clinical cure (RR 1.03, 95% CI 0.98 to 1.08), microbiological cure (RR 0.98, 95% CI 0.93 to 1.03) and mortality (RR 1.02, 95% CI 0.79 to1.30). Six studies reported no cases of acute kidney injury (AKI) needing dialysis. Adverse events were less frequent with teicoplanin including cutaneous rash (RR 0.57, 95% CI 0.35 to 0.92), red man syndrome (RR 0.21, 95% CI 0.08 to 0.59) and total adverse events (RR 0.73, 95% CI 0.53 to 1.00). A lower risk of nephrotoxicity with teicoplanin was observed in patients either with (RR 0.51, 95% CI 0.30 to 0.88) or without aminoglycosides (RR 0.31, 95% 0.07 to 1.50), and also when vancomycin dosing was guided by serum levels (RR 0.22, 95% CI 0.10 to 0.52).

AUTHORS' CONCLUSIONS

Teicoplanin and vancomycin are both effective in treating those with proven or suspected infection; however the incidence of adverse effects including nephrotoxicity was lower with teicoplanin. There were no cases of AKI needing dialysis. It remains unclear whether the differential effect on kidney function should influence which antibiotic be prescribed, although it may be reasonable to consider teicoplanin for patients at higher risk for AKI needing dialysis.

Management of methicillin-resistant Staphylococcus aureus pneumonia

PURPOSE OF REVIEW

Staphylococcus aureus, and particularly methicillin-resistant Staphylococcus aureus (MRSA) has become an increasingly important etiology of pneumonia, both in healthcare and community settings. Associated with highest morbidity, mortality and costs in public health, it represents a major challenge for the management of this group of patients.

RECENT FINDINGS

MRSA is one of the most common pathogens of ventilator associated pneumonia, whereas its estimated incidence for hospital acquired pneumonia, healthcare associated pneumonia and community acquired pneumonia has risen in the past decades. Although vancomycin at standard doses remains as the mainstay for its treatment, the increasing rate of treatment failure has prompted other strategies of use (more frequent administration, continuous infusion, combination therapy), and the use of newer antimicrobials, particularly linezolid, with pharmacokinetic and pharmacodynamic profiles which produce promisingly improved clinical results.

SUMMARY

Overall, MRSA is an important cause of pneumonia; optimal management strategies for improving morbidity and mortality are still under development.

The pathogen of ventilator-associated pneumonia does not influence the mortality rate of surgical intensive care unit patients treated with a rotational antibiotic system

BACKGROUND

Ventilator-associated pneumonia (VAP) is one of the leading causes of morbidity in critically ill surgical patients. Certain pathogens (e.g., methicillin-resistant Staphylococcus aureus, Pseudomonas aeruginosa) have been associated with an excess mortality rate from sepsis in several studies, but not in the surgical setting specifically or when protocol-driven antibiotic therapy is administered.

PURPOSE

We sought to determine which factors and, in particular, whether the individual pathogen affected the mortality rate in our surgical intensive care unit (ICU), where a rotational antibiotic system has been employed continuously since 1997. We hypothesized that the type of pathogen and illness severity were the primary influences on the mortality rate of patients with VAP.

METHODS

A total of 198 consecutive patients from a university surgical ICU, with clinical signs of VAP confirmed by quantified isolation of significant numbers of a pathogen (> or =10(4) colony-forming units [cfu]/mL) from bronchoalveolar (BAL) fluid obtained by fiberoptic bronchoscopy, were identified prospectively from January 2001 to November 2004. The data collected were age, sex, Acute Physiology and Chronic Health Evaluation (APACHE) III score, multiple organ dysfunction score, unit day of diagnosis, time (h) to antibiotic administration (TTA), appropriateness of initial therapy (AIT), unit and hospital length of stay, and mortality rate. Pathogens were classified as non-lactose-fermenting gram-negative bacilli (NGNB), lactose-fermenting gram-negative bacilli (LGNB), methicillin-sensitive Staphylococcus aureus, methicillin-resistant S. aureus, yeast, community-acquired pneumonia (e.g., Streptococcus pneumoniae), or other pathogens. Patients with a polymicrobial isolate were placed in the "other" category.

RESULTS

The overall mortality rate was 32.3% vs. 55% as predicted by APACHE III normative data. The overall AIT was 92%. The mortality rate for NGNB infections was 35.6% vs. 29.4% for LGNB infections (p = NS). By logistic regression, neither TTA, AIT, nor pathogen influenced the mortality rate.

CONCLUSIONS

The type of pathogen does not influence death in surgical ICU patients with VAP diagnosed rigorously and treated by a rotational antibiotic system. The high proportion of AIT as a result of the rotational antibiotic administration system optimizes bacterial killing and negates the impact of bacterial resistance, contributing to better outcomes.

New therapeutic choices for infections caused by methicillin-resistant Staphylococcus aureus

In recent years, a marked increase in the incidence of infections caused by methicillin-resistant Staphylococcus aureus (MRSA) has occurred in many countries. This review addresses the effectiveness and limitations of drugs classically used for the treatment of MRSA, e.g. vancomycin, and also newer anti-MRSA antimicrobials, e.g. second-generation glycolipopeptides, tigecycline, and beta-lactams.

Vancomycin-associated nephrotoxicity: grave concern or death by character assassination?

Vancomycin-associated nephrotoxicity was reported in 0% to 5% of patients in the 1980s. This has been confirmed by numerous clinical trials comparing novel anti-methicillin-resistant Staphylococcus aureus agents with vancomycin at the Food and Drug Administration-approved dosage of 1 g every 12 hours. Treatment failures of vancomycin in patients with methicillin-resistant S. aureus infections have been reported despite in vitro susceptibility. These failures have led to the use of vancomycin doses higher than those approved by the Food and Drug Administration. Higher doses are being administered to achieve goal vancomycin trough concentrations of 10 to 20 microg/mL recommended by several clinical practice guidelines endorsed by the Infectious Diseases Society of America. Recent studies suggest that increased rates of nephrotoxicity are associated with aggressive vancomycin dosing. These increased rates are confounded by concomitant nephrotoxins, renal insufficiency, or changing hemodynamics. These studies also have demonstrated that vancomycin's nephrotoxicity risk is minimal in patients without risk factors for nephrotoxicity. Clinicians unwilling to dose vancomycin in accordance with clinical practice guidelines should use an alternative agent because inadequate dosing increases the likelihood of selecting heteroresistant methicillin-resistant S. aureus isolates.

Pneumonia

Hospital-acquired pneumonia (HAP) is usually caused by bacterial, viral, or fungal pathogens that occur ≥48 h after hospital admission.^1,2 Overall, more than 80% of HAP episodes are related to invasive airway management (in patients with endotracheal intubation or tracheostomy) with mechanical ventilation, which is known as ventilator-associated pneumonia (VAP).³ VAP is defined as pneumonia developing more than 48 h after intubation and mechanical ventilation. Healthcare-associated pneumonia (HCAP) is part of the continuum of pneumonia, which includes patients who were hospitalized in an acute-care hospital for ≥2 days within 90 days of the infection; resided in a long-term care facility; received recent intravenous antibiotic therapy, chemotherapy, or wound care within the past 30 days of the current infection; or attended a hospital or hemodialysis clinic.^1,2 Although this document focuses more on HAP and VAP, many of the principles are also relevant to the management of HCAP. HAP, VAP, and HCAP are the second most common nosocomial infections after urinary tract infection, but are the leading causes of mortality due to hospital-acquired infections.^4,5

An investigation into the effects of silver nanoparticles on antibiotic resistance of naturally occurring bacteria in an estuarine sediment

The aim of this study was to test whether silver nanoparticles (Ag-NPs) released into estuarine environments result in increased antibiotic resistance amongst the natural bacterial population in estuarine sediments. A 50-day microcosm exposure experiment was carried out to investigate the effects of Ag-NPs (50 nm average diameter) on the antibiotic resistance of bacteria in sediments from an estuary in southwest England. Experimental microcosms were constructed using 3.5 kg sediment cores with 20 l of overlaying seawater treated with (final) Ag-NPs concentrations of 0, 50 or 2000 microg l(-1) (n=3). Sediment samples were screened at the end of the exposure period for the presence of bacteria resistant to eight different antibiotics. Multivariate statistical analyses showed that there was no increase in antibiotic resistance amongst the bacterial population in the sediment due to the dosing of the microcosms with Ag-NPs. This study indicates that, under the tested conditions, Ag-NPs released into the coastal marine environment do not increase antibiotic resistance among naturally occurring bacteria in estuarine sediments. These results contrast previous findings where antimicrobial effects of Ag-NPs on key bacterial species in laboratory experiments have been demonstrated, and reasons for this are discussed. The negligible effects demonstrated on bacterial populations under the selected estuarine conditions, provide important information on no observed effect concentrations (NOECs) for environmental regulation.

Pneumonia due to methicillin-resistant Staphylococcus aureus: clinical features, diagnosis and management

PURPOSE OF REVIEW

The review highlights the clinical findings and the management of community-acquired, health-care associated and nosocomial pneumonia due to methicillin-resistant Staphylococcus aureus (MRSA).

RECENT FINDINGS

Although previously considered as a purely nosocomial event, community-acquired MRSA pneumonia is underestimated and is spreading worldwide. A retrospective study showed that almost half of patients with nonnosocomial MRSA pneumonia admitted to a large teaching hospital did not present established criteria for healthcare-associated infections. Recent data show that MRSA ventilator-associated pneumonia is associated with significantly higher mortality than ventilator-associated pneumonia caused by methicillin-susceptible Staphylococcus aureus. Therefore, prompt and appropriate therapy is essential. The optimal therapy for MRSA pneumonia has not been fully elucidated. Although vancomycin has been considered the gold standard for the treatment of MRSA infections, clinical failures have also been reported in the presence of in-vitro susceptibility. Linezolid may provide improved outcomes compared with vancomycin in patients with MRSA pneumonia, but validation in a prospective trial is currently lacking. Recently licensed tigecycline and dalbavancin, a drug in phase III trial, look promising. Animal models showed that immunization against a cytolytic toxin secreted by most Staphylococcus aureus strains protects against lethal pneumonia.

SUMMARY

Rapid recognition of possible staphylococcal infection in patients with severe pneumonia is essential. The treatment of MRSA pneumonia must be prompt and effective in order to allow a fast microbiological clearance and to successfully manage the infection.

Treatment strategies for methicillin-resistant Staphylococcus aureus infections in pediatrics

Staphylococcus aureus is an important pathogen that frequently causes clinical disease in children. A wide array of illnesses can be caused by this common pathogen ranging from non-invasive skin infections to severe, life-threatening sepsis. Additionally, as antibacterials have been used to eradicate S. aureus, it has developed resistance to these important therapeutic agents. Methicillin-resistant S. aureus (MRSA) has become an increasing problem in pediatric patients over the past decade. In this review, we discuss the epidemiology, pathogenesis, and treatment options available in treating MRSA infections in children. Specifically, we address the importance of abscess drainage in the treatment of skin and soft tissue infections, the most common clinical manifestation of MRSA infections, and highlight the various agents that are available for treating this common infection. In severe, life-threatening invasive MRSA infections the primary therapeutic option is vancomycin. In cases of MRSA toxic shock syndrome the addition of clindamycin is necessary. In other invasive MRSA infections, such as pneumonia and musculoskeletal infections, the empiric treatment of choice is clindamycin. Finally, newer agents and additional treatment options are discussed.

The effect of antimicrobial resistance on patient outcomes: importance of proper evaluation of appropriate therapy

The impact of antimicrobial resistance on patient outcomes can be effectively measured only if the appropriateness of the antimicrobial therapy received is properly measured. Definition of appropriate therapy should include not only in vitro susceptibility but also the clinical adequacy of the antibiotic used, taking into account the pathogen isolated, the site of infection, known pharmacokinetic and pharmacodynamic properties of the drug, and dosing. In the absence of these data, the effect of delay or absence of appropriate therapy in patients infected with resistant bacterial pathogens is subject to confounding, and the true effect of resistance on outcomes may be obscured.

Pneumonia caused by methicillin-resistant Staphylococcus aureus

A recent increase in staphylococcal infections caused by methicillin-resistant Staphylococcus aureus (MRSA), combined with frequent, prolonged ventilatory support of an aging, often chronically ill population, has resulted in a large increase in cases of MRSA pneumonia in the health care setting. In addition, community-acquired MRSA pneumonia has become more prevalent. This type of pneumonia historically affects younger patients, follows infection with influenza virus, and is often severe, requiring hospitalization and causing the death of a significant proportion of those affected. Ultimately, hospital-acquired MRSA and community-acquired MRSA are important causes of pneumonia and present diagnostic and therapeutic challenges. Rapid institution of appropriate antibiotic therapy, including linezolid as an alternative to vancomycin, is crucial. Respiratory infection-control measures and de-escalation of initial broad-spectrum antibiotic regimens to avoid emergence of resistant organisms are also important. This article reviews the clinical features of, diagnosis of, and therapies for MRSA pneumonia.

Healthcare-associated pneumonia: principles and emerging concepts on management

Healthcare-associated pneumonia (HCAP) is a relatively new entity that includes pneumonia occurring in healthcare settings other than acute-care hospitals. Many patients with HCAP are at greater risk for colonization and infection with multi-drug resistant (MDR) bacteria such as Pseudomonas aeruginosa, Gram-negative bacilli-producing extended-spectrum beta-lactamases and methicillin-resistant Staphylococcus aureus. Infections with these MDR pathogens require different empiric antibiotic therapy. To avoid initiation of inappropriate antibiotic therapy that may result in poorer patient outcomes, new principles for HCAP management were outlined in the 2005 American Thoracic Society and Infectious Diseases Society of America guidelines. These guidelines were suggested for patients assessed in acute-care hospitals and clinics, and may not be applicable for all patients with suspected HCAP in nursing homes and other long-term care settings. This review article addresses HCAP management strategies in both clinical settings.

Managing community-acquired pneumonia: A European perspective

Community-acquired pneumonia (CAP) is a common disease and a frequent cause of morbidity and mortality worldwide. It puts an enormous burden on medical and economic resources, particularly if hospitalization is required. Initial antibacterial therapy for CAP is usually empirical, as culture and antibacterial sensitivity test results are rarely available at initial diagnosis. Any agent selected for empirical therapy should have good activity against the pathogens commonly associated with CAP, a favorable tolerability profile, and be administered in a simple dosage regimen for good compliance. Streptococcus pneumoniae remains the most common causative pathogen, although the incidence of this organism varies widely. Streptococcus pneumoniae strains with decreased susceptibility to penicillin have become increasingly prevalent over the past 30 years and are now a serious problem worldwide. In addition, an increase in the prevalence of pneumococci resistant to macrolides has been observed in Europe over recent years. Mycoplasma pneumoniae and Chlamydia pneumoniae are among the most common atypical pathogens isolated from patients with CAP. Haemophilus influenzae, Staphylococcus aureus and Moraxella catarrhalis are less commonly identified as causative organisms. The emergence and spread of resistance to commonly used antibiotics has challenged the management of CAP. Multiple sets of CAP guidelines have been published to address the continued changes in this complex disease.