Predictive value of methicillin-resistant staphylococcus aureus nasal swab in patients with COVID-19 pneumonia and secondary bacterial pneumonia

OBJECTIVE

To determine the performance measures of admission methicillin-resistant Staphylococcus aureus (MRSA) nasal swabs for MRSA bacterial pneumonia in patients co-infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2).

METHODS

The study included patients admitted with SARS-CoV-2-positive nasopharyngeal specimens, MRSA nasal screens, and bacterial cultures to assess secondary MRSA pneumonia.

RESULTS

293 patients and 662 microbiological cultures evaluated. Overall, the specificity (91.8% [95% CI 88.6% to 95%]) and negative predictive value (NPV 97.4% [95% CI 95.4% - 99.3%]) of MRSA nasal swabs was high. However, the sensitivity (46.2%; 95% CI 19.1% to 73.3%) and positive predictive value (PPV 20.7%; 95% CI 59.5 - 35.4%) were low. Those patients in the MRSA nasal swab negative group had a shorter median duration of linezolid therapy.

CONCLUSIONS

SARS-CoV-2 infection doesn't reduce the specificity or negative predictive value of MRSA nasal swabs for secondary MRSA pneumonia.

The efficacy of telavancin in comparison with linezolid on endotracheal tube biofilm in pigs with methicillin-resistant Staphylococcus aureus pneumonia

BACKGROUND

The effect of systemic treatment of ventilator-associated pneumonia (VAP) with telavancin, a semisynthetic lipoglycopeptide with good penetration in vitro biofilms, has not been tested in vivo during mechanical ventilation. This study examined the efficacy of telavancin compared with linezolid against endotracheal tube (ETT) biofilms in a porcine model of methicillin-resistant Staphylococcus aureus (MRSA) VAP.

METHODS

VAP was induced in 18 pigs by instilling 107 colony-forming units (CFU/mL) of an MRSA strain susceptible to telavancin and linezolid into each pulmonary lobe. Randomization into three groups was done at pneumonia diagnosis: control (IV glucose 0.5% solution q24); linezolid (10 mg/kg q12) and telavancin groups (22.5 mg/kg q24). After 72 h of MV, data regarding bronchoalveolar lavage (BAL), tracheal aspirate (TA), ETT MRSA biofilm load and thickness measured by scanning electron microscopy were obtained.

RESULTS

All 18 pigs completed the study. MRSA was isolated in 100% of ETTs from the control and linezolid groups and in 67% from the telavancin group. Telavancin treatment presented a lower MRSA load compared to the control and linezolid treatments (telavancin median [interquartile range (IQR)] = 1.94 [0.00-5.45], linezolid 3.99 [3.22-4.68] and control 4.93 [4.41-5.15], P = 0.236). Telavancin treatment also resulted in the lowest biofilm thickness according to the SEM (4.04 [2.09-6.00], P < 0.001). We found a positive correlation between ETT and BAL load (rho = 0.511, P = 0.045).

CONCLUSIONS

In our VAP model, systemic telavancin treatment reduced ETT MRSA occurrence, load, and biofilm thickness. Our findings may have a bearing on ICU patients' clinical outcomes.

IL-9 promotes methicillin-resistant Staphylococcus aureus pneumonia by regulating the polarization and phagocytosis of macrophages

In this study, we examined the effect of Il9 deletion on macrophages in methicillin-resistant Staphylococcus aureus (MRSA) infection. MRSA-infected mice were employed for the in vivo experiments, and RAW264.7 cells were stimulated with MRSA for the in vitro experiments. Macrophage polarization was determined by flow cytometry and quantitative real-time PCR; macrophage phagocytosis was assessed by flow cytometry and laser scanning confocal microscopy; cell apoptosis was assessed by flow cytometry and western blotting. Il9 deletion markedly elevated macrophage phagocytosis and M2 macrophages in MRSA infection, which was accompanied by elevated expression of Il10 and Arg1 and reduced expression of Inos, tumor necrosis factor-α (Tnfα), and Il6. Il9 deletion also inhibited macrophage apoptosis in MRSA infection, which was manifested by elevated B-cell lymphoma 2 (BCL-2) protein level and reduced protein levels of cleaved cysteine protease 3 (CASPASE-3) and BCL2-Associated X (BAX). Both the in vivo and in vitro experiments further showed the activation of phosphoinositide 3-kinase (PI3K)/AKT (also known as protein kinase B, PKB) signaling pathway in MRSA infection and that the regulation of Il9 expression may be dependent on Toll-like receptor (TLR) 2/PI3K pathway. The above results showed that Il9 deletion exhibited a protective role against MRSA infection by promoting M2 polarization and phagocytosis of macrophages and the regulation of Il9 partly owing to the activation of TLR2/PI3K pathway, proposing a novel therapeutic strategy for MRSA-infected pneumonia.

Ventilator-Associated Methicillin-Resistant Staphylococcus aureus (MRSA) Pneumonia in a Patient with a Negative MRSA Nasal Swab

BACKGROUND Methicillin-resistant Staphylococcus aureus (MRSA) pneumonia is associated with high morbidity and mortality. Recently, MRSA testing by nasal swab has been utilized to "exclude" pneumonia caused by MRSA, given its high negative-predictive value (NPV). We present, however, a case of MRSA pneumonia diagnosed by endotracheal aspirate culture (EAC) in a patient with a negative MRSA nasal swab. CASE REPORT A 58-year-old woman presented with septic shock and respiratory failure. Chest X-ray (CXR) on admission was unrevealing; however, computed tomography (CT) revealed multifocal pneumonia. Intensive Care Unit (ICU)-level care was required for mechanical ventilation and vasopressors. She initially improved with treatment of community-acquired pneumonia (CAP) and was extubated on hospital day 6; however, she then developed a fever, tachycardia, and respiratory distress necessitating re-intubation later that day. Repeat CXR demonstrated a new left lower lobe infiltrate. Blood cultures were drawn and vancomycin and cefepime were started to cover for ventilator-associated pathogens. An EAC and nasal swab were collected to test for MRSA. The next day (day 7), the MRSA nasal swab returned negative, and vancomycin was discontinued. Our patient continued to experience fevers, worsening leukocytosis, and ongoing vasopressor need. On hospital day 9, the EAC results were obtained, and were positive for MRSA. Vancomycin was restarted and our patient recovered. CONCLUSIONS Negative MRSA nasal screening may be considered grounds to de-escalate empiric MRSA antibiotics if MRSA prevalence is low. However, in critically ill patients with high risk and suspicion for MRSA pneumonia, discontinuing empiric MRSA coverage should be done with caution or clinicians should wait until respiratory culture results are obtained before de-escalating antibiotics.

Machine Learning To Stratify Methicillin-Resistant Staphylococcus aureus Risk among Hospitalized Patients with Community-Acquired Pneumonia

Methicillin-resistant Staphylococcus aureus (MRSA) is an uncommon but serious cause of community-acquired pneumonia (CAP). A lack of validated MRSA CAP risk factors can result in overuse of empirical broad-spectrum antibiotics. We sought to develop robust models predicting the risk of MRSA CAP using machine learning using a population-based sample of hospitalized patients with CAP admitted to either a tertiary academic center or a community teaching hospital. Data were evaluated using a machine learning approach. Cases were CAP patients with MRSA isolated from blood or respiratory cultures within 72 h of admission; controls did not have MRSA CAP. The Classification Tree Analysis algorithm was used for model development. Model predictions were evaluated in sensitivity analyses. A total of 21 of 1,823 patients (1.2%) developed MRSA within 72 h of admission. MRSA risk was higher among patients admitted to the intensive care unit (ICU) in the first 24 h who required mechanical ventilation than among ICU patients who did not require ventilatory support (odds ratio [OR], 8.3; 95% confidence interval [CI], 2.4 to 32). MRSA risk was lower among patients admitted to ward units than among those admitted to the ICU (OR, 0.21; 95% CI, 0.07 to 0.56) and lower among ICU patients without a history of antibiotic use in the last 90 days than among ICU patients with antibiotic use in the last 90 days (OR, 0.03; 95% CI, 0.002 to 0.59). The final machine learning model was highly accurate (receiver operating characteristic [ROC] area = 0.775) in training and jackknife validity analyses. We identified a relatively simple machine learning model that predicted MRSA risk in hospitalized patients with CAP within 72 h postadmission.

Methicillin-Resistant Staphylococcus aureus Hospital-Acquired Pneumonia/Ventilator-Associated Pneumonia

Methicillin-resistant Staphylococcus aureus (MRSA) is a common cause of hospital-acquired pneumonia (HAP) and ventilator-associated pneumonia (VAP). MRSA pneumonia is associated with significant morbidity and mortality. Several virulence factors allow S. aureus to become an effective pathogen. The polysaccharide intracellular adhesin allows for the production of biofilms, some strains can produce capsular polysaccharides that protect against phagocytosis, microbial surface components recognizing adhesive matrix molecules (MSCRAMMs) allow for colonization of epithelial surfaces, and S. aureus secretes several exotoxins that aid in tissue destruction. The α-hemolysin exotoxin secreted by S. aureus is one of the most important virulence factors for the bacteria. The diagnosis of MRSA pneumonia can be challenging; the infection may present as a mild respiratory infection or severe respiratory failure and septic shock. Many individuals are colonized with MRSA and thus a positive nasopharyngeal swab does not confirm infection in the lower respiratory tract. The management of MRSA pneumonia has evolved. Historically, vancomycin has been the primary antibiotic used to treat MRSA pneumonia. Over the past decade, prospective studies have shown that linezolid leads to higher rates of clinical cure. Monoclonal antibodies are being studied as potential therapeutic options. MRSA is an important cause of HAP/VAP; novel diagnostics may facilitate rapid diagnosis of this infection and the available literature should be used to make informed decisions on management.

Dehydrocostus Lactone Attenuates Methicillin-Resistant Staphylococcus aureus-Induced Inflammation and Acute Lung Injury via Modulating Macrophage Polarization

Dehydrocostus lactone (DHL), a natural sesquiterpene lactone isolated from the traditional Chinese herbs Saussurea lappa and Inula helenium L., has important anti-inflammatory properties used for treating colitis, fibrosis, and Gram-negative bacteria-induced acute lung injury (ALI). However, the effects of DHL on Gram-positive bacteria-induced macrophage activation and ALI remains unclear. In this study, we found that DHL inhibited the phosphorylation of p38 MAPK, the degradation of IκBα, and the activation and nuclear translocation of NF-κB p65, but enhanced the phosphorylation of AMP-activated protein kinase (AMPK) and the expression of Nrf2 and HO-1 in lipoteichoic acid (LTA)-stimulated RAW264.7 cells and primary bone-marrow-derived macrophages (BMDMs). Given the critical role of the p38 MAPK/NF-κB and AMPK/Nrf2 signaling pathways in the balance of M1/M2 macrophage polarization and inflammation, we speculated that DHL would also have an effect on macrophage polarization. Further studies verified that DHL promoted M2 macrophage polarization and reduced M1 polarization, then resulted in a decreased inflammatory response. An in vivo study also revealed that DHL exhibited anti-inflammatory effects and ameliorated methicillin-resistant Staphylococcus aureus (MRSA)-induced ALI. In addition, DHL treatment significantly inhibited the p38 MAPK/NF-κB pathway and activated AMPK/Nrf2 signaling, leading to accelerated switching of macrophages from M1 to M2 in the MRSA-induced murine ALI model. Collectively, these data demonstrated that DHL can promote macrophage polarization to an anti-inflammatory M2 phenotype via interfering in p38 MAPK/NF-κB signaling, as well as activating the AMPK/Nrf2 pathway in vitro and in vivo. Our results suggested that DHL might be a novel candidate for treating inflammatory diseases caused by Gram-positive bacteria.

Antimicrobial activity of dalbavancin and comparators against Staphylococcus aureus causing pneumonia in patients with and without cystic fibrosis

The activities of dalbavancin and comparator agents were evaluated against Staphylococcus aureus isolated from the lower respiratory tract of cystic fibrosis (CF) and non-CF patients with pneumonia. Bacterial isolates (n = 357) were collected from CF patients in 36 medical centers worldwide (2018-2019) and susceptibility tested using reference broth microdilution. Susceptibility results from these isolates were compared with those for 725 S. aureus isolates consecutively collected from non-CF patients with pneumonia from the same medical centers over the same period. Only isolates determined to be the probable cause of pneumonia were included in the study. Susceptibility profiles were very similar among isolates from CF and non-CF patients. Dalbavancin exhibited potent activity (MIC50/90, 0.03/0.03 mg/L) and complete coverage (100.0% susceptibility) against isolates from CF and non-CF patients. Ceftaroline (MIC50/90, 0.25/1 mg/L) was active against 97.8% and 98.1% of isolates from CF and non-CF patients, respectively. Oxacillin resistance (MRSA) rates were 27.7% among CF and 28.7% among non-CF patients. Among MRSA isolates from CF/non-CF patients (n = 99/208), susceptibility to ceftaroline, clindamycin, levofloxacin, and tetracycline were 91.9%/93.3%, 58.6%/64.4%, 40.4%/29.3%, and 83.8%/89.4%, respectively. Dalbavancin demonstrated high potency against S. aureus from CF and non-CF patients and may represent a valuable treatment option for CF patients with MRSA pulmonary infection.

Anti-inflammatory and antibacterial activities of P. petiolosa (Christ) Ching ethyl acetate extract against S. aureus in mice

P. petiolosa as a typical Chinese herbal medicine has been generally utilized as Chinese native medicine formulation for treatment of chronic bronchitis, bronchial asthma and pneumoconiosis. The objective of this study was to evaluate the anti-inflammatory and antibacterial activities of P. petiolosa ethyl acetate extract (PPEAE) against S. aureus in mice. The air-dried leaves were extracted with ethyl acetate, mice were infected pneumonia by S. aureus. Colonization of S. aureus in lung tissue was calculated by plate colony count. The number of white blood cells (WBC) in blood was measured by blood cell automatic analyzer. The histopathological analysis of hematoxylin-eosin staining (H&E) of lung tissue was observed under microscope. Real-time PCR assay was employed to determine the relative mRNA expression of HO-1, iNOS and TNF-α. The results showed that, compared with control, after treated with PPEAE the wet/dry (W/D) weight ratio of mice lung tissue (decreased from 5.371 to 4.9) and the number of white blood cells (WBC) (decreased by 3.13×10⁹/mL) decreased dramatically. The number of S. aureus was significantly reduced (from 1.93×105 CFU/mL to 26×103 CFU/mL) in lung tissue after treated with PPEAE. Furthermore, H&E staining showed that PPEAE obviously relieved the inflammation of lung tissue of infected mice. Meanwhile, real-time PCR results indicated that PPEAE down regulated the expression of inflammatory iNOS, TNF-α mRNA and up regulated the expression of anti-inflammatory HO-1 mRNA. In summary, this study revealed that application of crude product PPEAE had prominent antibacterial activity against S. aureus. PPEAE significantly reduced the biomass of S. aureus in lung tissue and effectively relieved the inflammation of S. aureus-induced pneumonia.

Diagnosis and Treatment of Adults with Community-acquired Pneumonia. An Official Clinical Practice Guideline of the American Thoracic Society and Infectious Diseases Society of America

Background: This document provides evidence-based clinical practice guidelines on the management of adult patients with community-acquired pneumonia.

Methods: A multidisciplinary panel conducted pragmatic systematic reviews of the relevant research and applied Grading of Recommendations, Assessment, Development, and Evaluation methodology for clinical recommendations.

Results: The panel addressed 16 specific areas for recommendations spanning questions of diagnostic testing, determination of site of care, selection of initial empiric antibiotic therapy, and subsequent management decisions. Although some recommendations remain unchanged from the 2007 guideline, the availability of results from new therapeutic trials and epidemiological investigations led to revised recommendations for empiric treatment strategies and additional management decisions.

Conclusions: The panel formulated and provided the rationale for recommendations on selected diagnostic and treatment strategies for adult patients with community-acquired pneumonia.

Ceftaroline fosamil as a potential treatment option for Staphylococcus aureus community-acquired pneumonia in adults

Staphylococcus aureus (S. aureus), including methicillin-resistant S. aureus (MRSA), is an important aetiological cause of community-acquired pneumonia (CAP) and associated with significant morbidity and mortality. Empiric therapy for CAP frequently consists of β-lactam monotherapy or β-lactam/macrolide combination therapy. However, such agents are often ineffective against S. aureus and do not reflect the emergence and increasing prevalence of MRSA in the community setting. Ceftaroline fosamil is a fifth-generation parenteral cephalosporin with broad-spectrum activity against Gram-positive pathogens - such as S. aureus (including MRSA), Streptococcus pneumoniae and Streptococcus pyogenes - and typical Gram-negative pathogens, including Haemophilus influenzae and Moraxella catarrhalis. The approval of ceftaroline fosamil in the United States and Europe for the treatment of adults with moderate-to-severe CAP was based on two phase 3 trials (FOCUS 1 and 2), which demonstrated that ceftaroline fosamil was non-inferior to ceftriaxone, a standard empiric treatment for CAP, while exhibiting a comparable safety profile. Although head-to-head trials of ceftaroline fosamil versus comparators against MRSA CAP are lacking, the effectiveness of ceftaroline fosamil in subpopulations of patients not covered by phase 3 trials (e.g. those with MRSA CAP or severe renal impairment) has been demonstrated in the Clinical Assessment Program and Teflaro Utilization Registry (CAPTURE) study. As ineffective empiric therapy is associated with adverse outcomes, including mortality and increased costs, ceftaroline fosamil, with its extended spectrum of activity, is an attractive alternative to standard antibiotic CAP regimens.

Clinical cure with ceftriaxone versus ceftaroline or ceftobiprole in the treatment of staphylococcal pneumonia: a systematic review and meta-analysis

Ceftriaxone is an empirical antibiotic commonly used to treat pneumonia. However, its use to treat infections caused by methicillin-susceptible Staphylococcus aureus (MSSA) is controversial given limited evidence of its clinical efficacy. The objective of this study was to compare the clinical efficacy of ceftriaxone with either ceftaroline or ceftobiprole in the treatment of pneumonia caused by MSSA. A systematic review and meta-analysis of randomised controlled trials (RCTs) comparing clinical cure in patients with pneumonia who received ceftriaxone versus those who received either ceftaroline or ceftobiprole was conducted. Patients who received ceftriaxone plus vancomycin were excluded. The PubMed, Embase and Cochrane Library databases as well as clinical trial registries were searched up to 8 June 2018. Risk differences (RDs) with 95% confidence intervals (CIs) were estimated using a random-effects model and assessing for heterogeneity (I2). A total of five RCTs met the inclusion criteria; four used ceftaroline and one used ceftobiprole. Four studies included adults and one included paediatric patients. The adult studies included non-intensive care unit patients with mild-to-moderate community-acquired pneumonia. Clinical cure was statistically lower with ceftriaxone (RD, -28.5%, 95% CI -53.5% to -3.4%; P = 0.026; I2 = 16.321%) than with ceftaroline or ceftobiprole. In conclusion, ceftriaxone use was associated with higher clinical failure of MSSA pneumonia compared with ceftaroline or ceftobiprole. This supports the notion that ceftriaxone is not an ideal agent for the treatment of MSSA infections and adds new evidence against its use for MSSA pneumonia.

Rapidly Progressive Multiple Cavity Formation in Necrotizing Pneumonia Caused by Community-acquired Methicillin-resistant Staphylococcus aureus Positive for the Panton-Valentine Leucocidin Gene

A 66-year-old man was transferred to our hospital for pneumonia that was resistant to sulbactam/ampicillin and levofloxacin therapy. Chest computed tomography showed the rapidly progressive formation of multiple cavities. Methicillin-resistant Staphylococcus aureus (MRSA) was isolated, and the patient was diagnosed with necrotizing pneumonia caused by community-acquired MRSA (CA-MRSA). The MRSA strain had type IV staphylococcus cassette chromosome mec and genes encoding Panton-Valentine leucocidin (PVL). CA-MRSA necrotizing pneumonia with the PVL gene is rare; only three cases have been previously reported in Japan. We administered anti-MRSA antibiotics and the patient achieved complete clinical and radiological improvement.

Pharmacokinetics of Ceftaroline in a Preterm Infant With Methicillin-Resistant Staphylococcus Aureus Pneumonia

We report here the first pharmacokinetic-pharmacodynamic relationship for ceftaroline in a preterm infant born at <28 weeks' gestational age who was given ceftaroline (8.5 mg/kg every 8 hours) for pneumonia attributable to methicillin-resistant Staphyloccocus aureus. This dose of ceftaroline was adequate to achieve the pharmacodynamic endpoint associated with efficacy for methicillin-resistant Staphyloccocus aureus.

Prevalence of Staphylococcus aureus and Use of Antistaphylococcal Therapy in Children Hospitalized with Pneumonia

Within a cohort of >2,000 children hospitalized with community-acquired pneumonia, staphylococcal pneumonia was rare (1%) but associated with adverse in-hospital outcomes. Despite this low prevalence, use of antistaphylococcal antibiotics was common (24%). Efforts are needed to minimize overuse of antistaphylococcal antibiotics while also ensuring adequate treatment for pathogen-specific diseases.

Pharmacokinetics of single-dose ceftaroline fosamil in children with cystic fibrosis

BACKGROUND

Single-dose pharmacokinetics (PK) and safety of ceftaroline fosamil with population pharmacokinetic/pharmacodynamic (PK/PD) modeling for staphylococcal pneumonia was performed in children with CF.

METHODS

Subjects between 6 and 18 years old were evaluated in this phase 1, open-label, single-dose, prospective study using 10 mg/kg (up to 600 mg). Non-compartmental analysis and population-based PK analyses with Monte Carlo simulation (for doses 8-20 mg/kg every 8 h, infused over 1-4 h) were conducted.

RESULTS

A total of 20 subjects were enrolled. The median age and weight were 12 yr (range 6.3-17.4) and 38.7 kg (range 17.8-94.3), respectively. A 3-compartment linear model incorporating age and weight provided the best fit for the data. Comparing children 6 to <12 years to those 12 to <18 years, the mean posthoc Bayesian parameter estimates for total volume of distribution (VT ) were 0.32 ± 0.05 L/kg versus 0.32 ± 0.04 L/kg, P = 0.7; and total Clearance (CLT ), 0.50 ± 0.10 L/h/kg versus 0.30 ± 0.07 L/h/kg, P = 0.001. Using susceptibility data from pediatric MRSA lower respiratory tract isolates, 8 mg/kg (maximum of 1000 mg per dose) infused over 1 h every 8 h achieved free-drug plasma concentrations above the minimum inhibitory concentration for ≥60% of the dosing interval in at least 95% of virtual subjects.

CONCLUSIONS

Since children with CF have increased ceftaroline CL compared with published data from non-CF children; greater dosages may be required in children with CF to achieve adequate exposure in the treatment of MRSA pneumonia. Pharmacodynamic-based dosing predicts that dosing should also be based on the patient's MRSA MIC.

Effects of Tedizolid Phosphate on Survival Outcomes and Suppression of Production of Staphylococcal Toxins in a Rabbit Model of Methicillin-Resistant Staphylococcus aureus Necrotizing Pneumonia

The protective efficacy of tedizolid phosphate, a novel oxazolidinone that potently inhibits bacterial protein synthesis, was compared to those of linezolid, vancomycin, and saline in a rabbit model of Staphylococcus aureus necrotizing pneumonia. Tedizolid phosphate was administered to rabbits at 6 mg/kg of body weight intravenously twice daily, which yielded values of the 24-h area under the concentration-time curve approximating those found in humans. The overall survival rate was 83% for rabbits treated with 6 mg/kg tedizolid phosphate twice daily and 83% for those treated with 50 mg/kg linezolid thrice daily (P = 0.66 by the log-rank test versus the results obtained with tedizolid phosphate). These survival rates were significantly greater than the survival rates of 17% for rabbits treated with 30 mg/kg vancomycin twice daily (P = 0.003) and 17% for rabbits treated with saline (P = 0.002). The bacterial count in the lungs of rabbits treated with tedizolid phosphate was significantly decreased compared to that in the lungs of rabbits treated with saline, although it was not significantly different from that in the lungs of rabbits treated with vancomycin or linezolid. The in vivo bacterial production of alpha-toxin and Panton-Valentine leukocidin, two key S. aureus-secreted toxins that play critical roles in the pathogenesis of necrotizing pneumonia, in the lungs of rabbits treated with tedizolid phosphate and linezolid was significantly inhibited compared to that in the lungs of rabbits treated with vancomycin or saline. Taken together, these results indicate that tedizolid phosphate is superior to vancomycin for the treatment of S. aureus necrotizing pneumonia because it inhibits the bacterial production of lung-damaging toxins at the site of infection.

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.

Antimicrobial and immunomodulatory effects of tedizolid against methicillin-resistant Staphylococcus aureus in a murine model of hematogenous pulmonary infection

Tedizolid (TZD) is a second-generation oxazolidinone and demonstrates potent in-vitro activity against multidrug-resistant Gram-positive bacteria. Phase III studies in patients with acute bacterial skin and skin structure infections (ABSSSI) have demonstrated the non-inferiority of TZD to linezolid (LZD). However, there are only a few studies that show the effect of TZD in pulmonary infections. In this study, we investigated the effect of TZD in a murine model of hematogenous pulmonary infection caused by methicillin-resistant Staphylococcus aureus (MRSA). The mice were treated either twice daily with saline (control), 25mg/kg of vancomycin (low-VAN), 110mg/kg of vancomycin (high-VAN), 120mg/kg of LZD or once daily with 20mg/kg of TZD. As compared to the control, the low- and high-VAN treatment groups, LZD and TZD significantly improved the survival rate, reduced the bacterial count in the lungs. Furthermore, TZD decreased the area of central bacterial colony zone (CBCZ) at 36h post-inoculation, compared with the control. In addition, we investigated the immunomodulatory effect of TZD by evaluating the plasma concentrations of the inflammatory cytokines. Although there were no significant differences in the bacterial count in the lungs amongst the drugs at 26h post-inoculation, TZD and LZD significantly improved the plasma concentrations of TNF-alpha, IL-6 and MIP-2, in comparison with the control. In this study, both TZD and LZD demonstrated antimicrobial and immunomodulatory efficacy in a murine model of hematogenous pulmonary infection caused by MRSA.

Lack of Sphingosine Causes Susceptibility to Pulmonary Staphylococcus Aureus Infections in Cystic Fibrosis

BACKGROUND

Pulmonary Staphylococcus aureus (S. aureus) infections occur early in a high percentage of cystic fibrosis (CF) patients and it is believed that these infections facilitate further colonization of CF lungs with Pseudomonas aeruginosa (P. aeruginosa). Previous studies demonstrated a marked reduction of sphingosine in tracheal and bronchial epithelial cells in CF compared to wild type mice, while ceramide is massively increased in CF mice.

METHODS

We investigated the effect of C18-sphingosine and C16-ceramide on S. aureus in vitro. Based on our results we performed pulmonary infections with S. aureus and tested the influence of sphingosine inhalation.

RESULTS

In vitro incubation of S. aureus with C18-sphingosine rapidly killed S. aureus, while C16-ceramide did not affect bacterial survival, but abrogated the effect of C18-sphingosine when applied together. The in vivo infection experiments revealed a high susceptibility of CF mice to pulmonary infection with S. aureus. Inhalation of C18-sphingosine rescued CF mice from pulmonary infections with different clinical S. aureus isolates, including a methicillin-resistant S. aureus (MRSA) strain.

CONCLUSIONS

Our data indicate that the imbalance between ceramide and sphingosine in the CF respiratory tract prevents killing of S. aureus and causes the high susceptibility of CF mice to pulmonary S. aureus infections.

[Community-acquired pneumonia in the elderly]

We report the case of a 88 years old patient with cough and new onset confusion. Delirium was caused by a necrotizing Methicillin-sensible staphylococcus aureus pneumonia with bacteremia. Despite antibiotic therapy for several weeks and fall of inflammatory markers the patient died from consequences of delirium.

Linezolid Versus Vancomycin in the Empiric Treatment of Nosocomial Pneumonia: A Cost-Utility Analysis Incorporating Results from the ZEPHyR Trial

OBJECTIVE

To examine the cost-effectiveness of vancomycin versus linezolid in the empiric treatment of nosocomial pneumonias incorporating results from a recent prospective, double-blind, multicenter, controlled trial in adults with suspected methicillin-resistant Staphylococcus aureus (MRSA) nosocomial pneumonia.

METHODS

A decision-analytic model examining the cost-effectiveness of linezolid versus vancomycin for the empiric treatment of nosocomial pneumonia was created. Publicly available cost, efficacy, and utility data populated relevant model variables. A probabilistic sensitivity analysis varied parameters in 10,000 Monte-Carlo simulations, and univariate sensitivity analyses assessed the impact of model uncertainties and the robustness of our conclusions.

RESULTS

Results indicated that the cost per quality-adjusted life-year (QALY) increased 6% ($22,594 vs. $23,860) by using linezolid versus vancomycin for nosocomial pneumonia. The incremental cost per QALY gained by using linezolid over vancomycin was $6,089, and the incremental cost per life saved was $68,615 with the use of linezolid. Vancomycin dominated linezolid in the subset of patients with documented MRSA. The incremental cost per QALY gained using linezolid if no mortality benefit exists between agents or a 60-day time horizon was analyzed was $19,608,688 and $443,662, respectively.

CONCLUSIONS

Linezolid may be a cost-effective alternative to vancomycin in the empiric treatment of patients with suspected MRSA nosocomial pneumonia; however, results of our model were highly variable on a number of important variables and assumptions including mortality differences and time frame analyzed.

Methicillin-resistant Staphylococcus aureus nosocomial pneumonia patients treated with ceftaroline: retrospective case series of 10 patients

BACKGROUND

Methicillin-resistant Staphylococcus aureus (MRSA) is a common nosocomial pneumonia (NP) pathogen in US ICUs. Ceftaroline fosamil is a novel cephalosporin with activity against MRSA.

METHODS

We retrospectively reviewed patients (pts) who received ceftaroline therapy for MRSA NP.

RESULTS

A total of 10 pts received ceftaroline from September 2011 to September 2012 for MRSA NP. Nine pts received prior anti-MRSA therapy before initiation of ceftaroline. Ceftaroline duration of therapy ranged from 4 to 28 days. Three pts pursued palliative care prior to completion of therapy and expired off antibiotics. Of the remaining seven pts, six pts were considered to have clinical cure or improvement either at the end of therapy with ceftaroline or total antibiotic treatment. One pt had a relapse 1 week after ceftaroline treatment.

CONCLUSIONS

This case series suggests the potential of ceftaroline as an alternative agent for the treatment of MRSA NP and warrants further investigation.

[Analysis of serum vancomycin concentration after administration of different doses in children with Staphylococcus aureus pneumonia]

OBJECTIVE

To analyze serum vancomycin concentration after administration of different therapeutic doses in children with Staphylococcus aureus pneumonia (SAP) in order to determine the appropriate dose of vancomycin in clinical administration.

METHODS

The clinical data of 35 children who were diagnosed with SAP and treated with vancomycin from January 2008 to December 2013 were retrospectively analyzed.

RESULTS

Among the 35 SAP cases with vancomycin therapy, 22 cases (63%) had serum vancomycin trough concentration monitored. The numbers of cases with vancomycin at 10, 12.5, and 15 mg/(kg·dose) × every 6 hours (q6h) were 11, 4 and 7, respectively. The mean serum trough concentration of vancomycin in the 15 mg/(kg·dose) group was 14.98 mg/L, which was significantly higher than in the 10 mg/(kg·dose) and 12.5 mg/(kg·dose) groups (4.97 and 8.00 mg/L respectively; P<0.05). The percentage of cases that reached the expected trough concentration in the 15 mg/(kg·dose) group (71%) was significantly higher than that in the 10 mg/(kg·dose) group (9%), but there was no significant difference in this percentage between the 15 mg/(kg·dose) and 12.5 mg/(kg·dose) groups (71% vs 25%).

CONCLUSIONS

The reasonable dosage of vancomycin for the treatment of pediatric SAP is 15 mg/(kg·dose) × q6h or 60 mg/(kg·d).

[Clinical features of inhaled and blood-borne Staphylococcus aureus pneumonia and analysis of antibiotic resistance of the pathogen in children]

OBJECTIVE

To compare the clinical manifestations between inhaled and blood-borne Staphylococcus aureus pneumonia (SAP) and the antibiotic resistance between the isolates of inhaled and blood-borne Staphylococcus aureus.

METHODS

The clinical data of 44 pediatric SAP cases in the Children&prime;s Hospital, Chongqing Medical University from January 2008 to December 2013 were retrospectively analyzed. Twenty-four cases were identified as inhaled SAP, and 20 cases as blood-borne SAP.

RESULTS

Inhaled SAP was more common in children younger than 3 years of age, while blood-borne SAP was more prevalent in children older than 6 years of age. Patients with inhaled SAP had significantly higher incidence rates of cough, wheeze, moist rales, dyspnea and empyema than those with blood-borne SAP (P&lt;0.05). The patients with blood-borne SAP were more vulnerable to severe fever, unconsciousness, dysfunction of liver and kidney, pyogenic osteomyelitis, septic arthritis, sepsis, and abscess of skin and soft tissues (P&lt;0.05). Inhaled SAP isolates had significantly higher rates of resistance to amoxicillin/clavulanic acid, oxacillin, and cefoxitin than blood-borne SAP isolates (P&lt;0.05), while the latter had a higher rate of resistance to cotrimoxazole (P&lt;0.05).

CONCLUSIONS

Inhaled SAP often occurs in children younger than 3 years of age, and the respiratory manifestations are commonly seen. Blood-borne SAP often occurs in children older than 6 years of age, with the infectious-toxic symptoms that result in multiple organ infection and dysfunction. The isolates of inhaled and blood-borne SAP have different antibiograms.

[Antibiotics for treatment of infections by methicillin-resistant Staphylococcus aureus (MRSA)]

Over the last 50 years methicillin-resistant S. aureus (MRSA) spread globally. Vancomycin is still the most recommended antibiotic for MRSA-infections. Teicoplanin is an alternative glycopeptide with longer elimination half-life. Telavancin is a more recently developed derivative of vancomycin with similar clinical efficacy as vancomycin. It is not recommended for treatment of patients with renal insufficiency. Nephrotoxicity limits the therapeutic use of glycopeptide antibiotics. The oxazolidinone linezolid exhibits similar to superior therapeutic efficacy. Hematologic controls are necessary during treatment with this antibacterial agent. Neurotoxic effects have been observed mainly in patients who received prolonged linezolid treatment. Attention must be paid to possible interactions with concomitantly given drugs acting on the serotonergic system. New therapeutic options arise with ceftaroline, the first β-lactam antibiotic with activity against MRSA. However, controlled clinical trials with pulmonary MRSA infections have not been conducted with ceftaroline. Daptomycin, a lipopeptide, and tigecycline, a glycylcyclin are active in vitro against MRSA as well, but are also not indicated in pulmonary MRSA infections. These antibiotics show in an exemplary manner that antibacterial activity in vitro is an important prerequisite, but relevant data for a therapeutic decision should be derived from randomized controlled clinical double-blind trials.

A novel treatment option for MRSA pneumonia: ceftaroline fosamil-yielding new hope in the fight against a persistent infection

Methicillin-resistant Staphylococcus aureus (MRSA) hospital-acquired pneumonia (HAP) and healthcare-associated pneumonia (HCAP) patients treated with current antibiotic therapies have exhibited poor outcomes, increased hospital length of stay, and higher costs of care. The optimal management of these infections is undetermined; thus, it is critical to look at ways to improve outcomes in these patients. There is insufficient data on clinical efficacy in patients with MRSA HAP or HCAP infection treated with ceftaroline-fosamil. In a recent pilot study, nearly 90% of patients treated with ceftaroline-fosamil survived, despite the difficulties associated with administrating bactericidal antimicrobial therapy for this increasingly resistant pathogen. These data suggest a possible benefit in the use of ceftaroline-fosamil for MRSA pneumonia. Presently, we have identified cases over a two-year period treated with ceftaroline-fosamil, and will conduct a comparative analysis to controls (those treated with vancomycin and/or cefepime, and linezolid) to determine optimal therapeutic agents; these findings will have important implications for control of further spread of infection, recurrence, readmission, and mortality attributable to MRSA HAP and HCAP.

Kineret®/IL-1ra blocks the IL-1/IL-8 inflammatory cascade during recombinant Panton Valentine Leukocidin-triggered pneumonia but not during S. aureus infection

OBJECTIVES

Community-acquired Staphylococcus aureus necrotizing pneumonia is a life-threatening disease. Panton Valentine Leukocidin (PVL) has been associated with necrotizing pneumonia. PVL triggers inflammasome activation in human macrophages leading to IL-1β release. IL-1β activates lung epithelial cells to release IL-8. This study aimed to assess the relevance of this inflammatory cascade in vivo and to test the potential of an IL-1 receptor antagonist (IL-1Ra/Kineret) to decrease inflammation-mediated lung injury.

METHODS

We used the sequential instillation of Heat-killed S. aureus and PVL or S. aureus infection to trigger necrotizing pneumonia in rabbits. In these models, we investigated inflammation in the presence or absence of IL-1Ra/Kineret.

RESULTS

We demonstrated that the presence of PVL was associated with IL-1β and IL-8 release in the lung. During PVL-mediated sterile pneumonia, Kineret/IL-1Ra reduced IL-8 production indicating the relevance of the PVL/IL-1/IL-8 cascade in vivo and the potential of Kineret/IL-1Ra to reduce lung inflammation. However, Kineret/IL-1Ra was ineffective in blocking IL-8 production during infection with S. aureus. Furthermore, treatment with Kineret increased the bacterial burden in the lung.

CONCLUSIONS

Our data demonstrate PVL-dependent inflammasome activation during S.aureus pneumonia, indicate that IL-1 signaling controls bacterial burden in the lung and suggest that therapy aimed at targeting this pathway might be deleterious during pneumonia.

Severe hospital acquired pneumonia and septicemia due TO methicillin resistant Staphylococcus lugdunensis in a newborn in Northwestern Ethiopia

Staphylococcus lugdunensis can cause virulent infections in immunosuppressed individuals. This report describes the first known case of hospital acquired pneumonia and septicemia due to methicillin-resistant Staphylococcus lugdunensis in a newborn at Felege Hiwot Referral Hospital, North Western Ethiopia. The strain was simultaneously resistant to trimethoprim-sulfamethoxazole, tetracycline (30 ug), chloramphenicol (30 ug), gentamycin (10ug) and ciprofloxacin (5ug) but sensitive to erythromycin (15ug) and clindamycin (10ug).

[Ceftaroline fosamil in community-acquired and nosocomial pneumonia]

Community-acquired pneumonia (CAP) is a common infection in developed countries and causes a large number of hospital admissions and deaths. In recent years, the incidence of this disease has increased, caused by progressive population aging. Following the introduction of the conjugate vaccine against Streptococcus pneumoniae, there have been significant epidemiological changes that require close monitoring because of the possible emergence of new patterns of resistance. This article aims to review the role of ceftaroline fosamil, a new parenteral cephalosporin with antibacterial activity against Gram-negative and Gram-positive pathogens, in the treatment of pneumonia. Several in vitro and in vivo studies have shown the efficacy of ceftaroline fosamil against penicillin-resistant S. pneumoniae and methicillin-resistant Staphylococcus aureus (MRSA). Additionally, ceftaroline has shown similar efficacy and safety to ceftriaxone in the treatment of community-acquired pneumonia with severe prognosis (prognostic severity index III and IV) in two phase III clinical trials. Although a non-inferiority design was used for these clinical trials, some data suggest a superior efficacy of ceftaroline, with earlier clinical response and higher cure rate in infections caused by S. pneumoniae, making this drug particularly interesting for critically-ill patients admitted to the intensive care unit. Ceftaroline may also be considered for empirical and directed treatment of MRSA pneumonia.

Whole genome analysis of a community-associated methicillin-resistant Staphylococcus aureus ST59 isolate from a case of human sepsis and severe pneumonia in China

We report a case of necrotizing pneumonia in a young patient caused by community acquired-methicillin resistant Staphylococcus aureus (CA-MRSA) in a teaching hospital in the People's Republic of China. The patient had a typical clinical presentation and was successfully treated with antibiotics and intravenous immunoglobulin. A CA-MRSA strain, named SA268, was isolated from the blood of the patient. The isolate was susceptible to most antimicrobial agents, except cephalosporins, penicillins, and β-lactamase inhibitor combinations. Multi-locus sequence typing (MLST) assigned SA268 to ST59, a clone widely spread in eastern Asia. The strain was positive for Panton Valentine Leukocidin (PVL)-encoding genes and SCCmec type V. We sequenced the complete genome of the SA268 isolate. The genome of SA268 was almost identical to that of the Taiwanese ST59 CA-MRSA strains M013 and SA957. However, we observed several differences in gene composition, which included differences in the SCCmec element and several lipoprotein genes that were present in the Taiwanese strains but absent from SA268.

Linezolid Exerts Greater Bacterial Clearance but No Modification of Host Lung Gene Expression Profiling: A Mouse MRSA Pneumonia Model

Background

Linezolid (LZD) is beneficial to patients with MRSA pneumonia, but whether and how LZD influences global host lung immune responses at the mRNA level during MRSA-mediated pneumonia is still unknown.

Methods

A lethal mouse model of MRSA pneumonia mediated by USA300 was employed to study the influence of LZD on survival, while the sublethal mouse model was used to examine the effect of LZD on bacterial clearance and lung gene expression during MRSA pneumonia. LZD (100mg/kg/day, IP) was given to C57Bl6 mice for three days. On Day 1 and Day 3 post infection, bronchoalveolar lavage fluid (BALF) protein concentration and levels of cytokines including IL6, TNFα, IL1β, Interferon-γ and IL17 were measured. In the sublethal model, left lungs were used to determine bacterial clearance and right lungs for whole-genome transcriptional profiling of lung immune responses.

Results

LZD therapy significantly improved survival and bacterial clearance. It also significantly decreased BALF protein concentration and levels of cytokines including IL6, IL1β, Interferon-γ and IL17. No significant gene expression changes in the mouse lungs were associated with LZD therapy.

Conclusion

LZD is beneficial to MRSA pneumonia, but it does not modulate host lung immune responses at the transcriptional level.

Risk factors for methicillin-resistant Staphylococcus aureus in patients with community-onset and hospital-onset pneumonia

OBJECTIVES

The risk factors for methicillin-resistant Staphylococcus aureus (MRSA) pneumonia have not been fully characterized and are likely to be different depending on whether infection is acquired in the community or the hospital.

METHODS

We conducted a case-control study of 619 adults hospitalized between 2005 and 2010 with either MRSA or methicillin-sensitive S. aureus (MSSA) pneumonia. Patients with a respiratory culture within 48 h of hospitalization had community-onset pneumonia whereas patients with a culture collected after this time point had hospital-onset pneumonia.

RESULTS

Among patients with community-onset disease, the risk for MRSA was increased by tobacco use (OR 2.31, CI 1.23-4.31), chronic obstructive pulmonary disease (OR 3.76, CI 1.74-8.08), and recent antibiotic exposure (OR 4.87, CI 2.35-10.1) in multivariate analysis while patients with hospital-onset disease had an increased MRSA risk with tobacco use (OR 2.66, CI 1.38-5.14), illicit drug use (OR 3.52, CI 2.21-5.59), and recent antibiotic exposure (OR 2.04, CI 3.54-13.01). Hospitalization within the prior three months was associated with decreased risk (OR 0.64, CI 0.46-0.89) in multivariate analysis.

CONCLUSIONS

This study suggests there are common and distinct risk factors for MRSA pneumonia based on location of onset. The decreased risk for MRSA pneumonia associated with recent hospitalization is unexpected and warrants further investigation.

SUMMARY

This case-control study showed that there are common and distinct risk factors associated with MRSA pneumonia depending on whether the infection onset is in the hospital or in the community. Recent hospitalization was unexpectedly shown to be associated with decreased risk for MRSA pneumonia and warrants further investigation.

Engineering a soluble high-affinity receptor domain that neutralizes staphylococcal enterotoxin C in rabbit models of disease

Superantigens (SAgs) are a class of immunostimulatory exotoxins that activate large numbers of T cells, leading to overproduction of cytokines and subsequent inflammatory reactions and systemic toxicity. Staphylococcal enterotoxin C (SEC), a SAg secreted by Staphylococcus aureus, has been implicated in various illnesses including non-menstrual toxic shock syndrome (TSS) and necrotizing pneumonia. SEC has been shown to cause TSS illness in rabbits and the toxin contributes to lethality associated with methicillin-resistant S.aureus (MRSA) in a rabbit model of pneumonia. With the goal of reducing morbidity and mortality associated with SEC, a high-affinity variant of the extracellular variable domain of the T-cell receptor beta-chain for SEC (~14 kDa) was generated by directed evolution using yeast display. This protein was characterized biochemically and shown to cross-react with the homologous (65% identical) SAg staphylococcal enterotoxin B (SEB). The soluble, high-affinity T-cell receptor protein neutralized SEC and SEB in vitro and also significantly reduced the bacterial burden of an SEC-positive strain of MRSA (USA400 MW2) in an infective endocarditis model. The neutralizing agent also prevented lethality due to MW2 in a necrotizing pneumonia rabbit model. These studies characterize a soluble high-affinity neutralizing agent against SEC, which is cross-reactive with SEB, and that has potential to be used intravenously with antibiotics to manage staphylococcal diseases that involve these SAgs.

The use of ceftaroline fosamil in methicillin-resistant Staphylococcus aureus endocarditis and deep-seated MRSA infections: a retrospective case series of 10 patients

There are many limitations to the current antibiotics used for the treatment of severe methicillin-resistant Staphylococcus aureus (MRSA) infections. Ceftaroline is a new fifth-generation cephalosporin approved for the treatment of skin and soft tissue infections caused by MRSA and community-acquired pneumonia. We propose that ceftaroline can also be used successfully in more severe MRSA infections, including endocarditis. We conducted a retrospective chart review in a university-affiliated Department of Veterans Affairs hospital in San Diego, California (USA) of ten inpatients treated with ceftaroline for severe MRSA infection, including five cases of probable endocarditis (including two endocardial pacemaker infections), one case of pyomyositis with possible endocarditis, two cases of pneumonia (including one case of empyema), two cases of septic arthritis (including one case of prosthetic joint infection), and two cases of osteomyelitis. Seven of the 10 patients achieved microbiological cure. Six of the 10 patients achieved clinical cure. Seven patients were discharged from the hospital. Three patients were placed on comfort care and expired in the hospital; one achieved microbiological cure before death, and two remained bacteremic at time of death. In most patients, ceftaroline was effective for treatment of MRSA bacteremia and other severe MRSA infections. Adverse effects seen included rash, eosinophilia, pruritus, and Clostridium difficile infection. Ceftaroline can be a safe and effective drug for treatment of severe MRSA infections, and further comparative studies are warranted.

Silibinin in vitro protects A549 cells from Staphylococcus aureus-mediated injury and in vivo alleviates the lung injury of staphylococcal pneumonia

In this study, hemolysis, Western blot, and real-time RT-PCR assays were performed to evaluate silibinin's activity against S. aureus α-toxin secretion. In addition, live/dead cell staining and lactate dehydrogenase activity assays were introduced to examine the influence of silibinin on α-toxin-induced cell injury in human alveolar epithelial cells. Furthermore, we tested the influence of silibinin on S. aureus pneumonia in a mouse model. We show that silibinin inhibits the expression of α-toxin in a dose-dependent manner and alleviates α-toxin-induced lung cell injury. The IC50 of silibinin that inhibits the hemolytic activity of S. aureus was 14.33 µg/mL for strain 8325-4. Moreover, this compound provides effective protection on the lung injury of staphylococcal pneumonia.

Efficacy of ceftaroline fosamil in a staphylococcal murine pneumonia model

Ceftaroline fosamil is a cephalosporin with activity against Gram-positive pathogens, including methicillin-resistant Staphylococcus aureus (MRSA). The objective of this study was to characterize the dose-response relationship of ceftaroline fosamil against S. aureus in an immunocompromised murine pneumonia model, as well as to evaluate the efficacy of the humanized regimen of 600 mg intravenously (i.v.) every 12 h. Seventeen S. aureus (2 methicillin-susceptible Staphylococcus aureus [MSSA], 15 MRSA) isolates with ceftaroline MICs of 0.5 to 4 μg/ml were utilized. The pharmacokinetics of ceftaroline in serum and epithelial lining fluid (ELF) were evaluated to determine bronchopulmonary exposure profiles in infected and uninfected animals, using single and human-simulated doses. Serum fT>MIC (the percentage of time that free drug concentrations remain above the MIC) of 17% to 43% was required to produce a 1-log(10) kill in the dose-ranging studies. These targets were readily achieved with the humanized exposure profile, where decreases of 0.64 to 1.95 log(10) CFU were observed against 13 MRSA and both MSSA isolates tested. When taken as a composite, the fT>MICs required for stasis and a 1-log(10) kill were 16% and 41%, respectively. ELF concentrations were similar to serum concentrations across the dosing interval in infected and uninfected animals. The serum fT>MIC targets required in this lung infection model were similar to those observed with ceftaroline against S. aureus in a murine thigh infection model. Exposures simulating the human dose of 600 mg i.v. every 12 h achieved pharmacodynamic targets against MRSA and MSSA considered susceptible by current U.S. FDA breakpoints.

[Clinical investigation of arbekacin sulfate based on Cmax/MIC]

We examined the peck concentration (Cmax)/minimal inhibitory concentration (MIC) and the clinical efficacy in methicillin-resistant Staphylococcus aureus (MRSA) pneumonia and Gram-positive cocci bacteremia. We evaluated arbekacin (ABK) on 22 cases of pneumonia and 10 cases of bacteremia in Aichi Medical University Hospital between August 2008 and July 2011, retrospectively. In pneumonia cases, Cmax/MIC was 16.4 +/- 2.8 in the effective group, and was 17.6 +/- 4.5 in the not effective group, the significant differences were not accepted (p = 0.8). The dosage of ABK was 4.7 +/- 1.4 mg/kg/dose in the effective group and was 4.3 +/- 0.7 mg/kg/dose in the not effective group. In bacteremia cases, Cmax/MIC was 24.2 +/- 13.9 in the effective group and 12.9 +/- 3.9 in the not effective group about clinical efficacy, and the high tendency was accepted by the effective group (p < 0.05). The dosage of ABK was 3.4 +/- 1.1 mg/kg/dose in the effective group, and 3.0 +/- 0.6 mg/kg/dose in the not effective group. In this examination, the significant difference was not observed in clinical efficacy and Cmax/MIC in the pneumonia cases. Although it was reported that clinical efficacy of ABK was given Cmax/MIC at eight or more, in this examination, all cases was eight or more at Cmax/MIC, and the clinical effect was 40.9%. On Cmax/MIC of ABK, clinical effective group was higher than not effective group in bacteremia cases, it was suggested that the administration design should make that Cmax/MIC at least about 14 or more would be necessary.

Comparative in vivo efficacies of epithelial lining fluid exposures of tedizolid, linezolid, and vancomycin for methicillin-resistant Staphylococcus aureus in a mouse pneumonia model

The antibacterial efficacies of tedizolid phosphate (TZD), linezolid, and vancomycin regimens simulating human exposures at the infection site against methicillin-resistant Staphylococcus aureus (MRSA) were compared in an in vivo mouse pneumonia model. Immunocompetent BALB/c mice were orally inoculated with one of three strains of MRSA and subsequently administered 20 mg/kg TZD every 24 hours (q24h), 120 mg/kg linezolid q12h, or 25 mg/kg vancomycin q12h over 24 h. These regimens produced epithelial lining fluid exposures comparable to human exposures observed following intravenous regimens of 200 mg TZD q24h, 600 mg linezolid q12h, and 1 g vancomycin q12h. The differences in CFU after 24 h of treatment were compared between control and treatment groups. Vehicle-dosed control groups increased in bacterial density an average of 1.1 logs. All treatments reduced the bacterial density at 24 h with an average of 1.2, 1.6, and 0.1 logs for TZD, linezolid, and vancomycin, respectively. The efficacy of TZD versus linezolid regimens against the three MRSA isolates was not statistically different (P > 0.05), although both treatments were significantly different from controls. In contrast, the vancomycin regimen was significantly different from TZD against one MRSA isolate and from linezolid against all isolates. The vancomycin regimen was less protective than either the TZD or linezolid regimens, with overall survival of 61.1% versus 94.7% or 89.5%, respectively. At human simulated exposures to epithelial lining fluid, vancomycin resulted in minimal reductions in bacterial counts and higher mortality compared to those of either TZD or linezolid. TZD and linezolid showed similar efficacies in this MRSA pneumonia model.

Do we understand the impact of altered physiology, consequent interventions and resultant clinical scenarios in the intensive care unit? The antibiotic story

Early, appropriate antibacterial therapy is a key factor in effectively managing septic critically ill patients1. The prescriber must not only employ an agent of appropriate spectrum, but also in an adequate dose to achieve bacterial eradication at the site of infection. However, the relationship between drug administration and therapeutic success is complex in the critically ill, such that a patient's physiology heavily influences the way drugs distribute into tissue and are eliminated. This represents a significant challenge to the emergency or intensive care physician, and in this manner, personalising therapy, through a greater understanding of how a drug will behave in an individual patient, is likely to lead to improved outcomes.