Survival during influenza-associated bacterial superinfection improves following viral- and bacterial-specific monoclonal antibody treatment.

Postinfluenza bacterial superinfections cause increased morbidity and mortality compared with singular infection with influenza during both pandemics and seasonal epidemics. Vaccines and current treatments provide limited benefit, a rationale to conduct studies utilizing alternative therapies. FY1 and an optimized version, MEDI8852, anti-influenza HA mAbs, have been shown to neutralize influenza virus during singular influenza infection. MEDI4893*, an anti-Staphylococcus aureus α-toxin mAb, has been shown to improve survival when administered prophylactically prior to S. aureus pneumonia. Our objective was to determine if mAbs can improve survival during postinfluenza bacterial pneumonia. We administered FY1 in a murine model of postinfluenza methicillin-resistant S. aureus (MRSA) pneumonia and observed improved survival rates when given early during the course of influenza infection. Our findings indicate decreased lung injury and increased uptake and binding of bacteria by macrophages in the mice that received FY1 earlier in the course of influenza infection, corresponding to decreased bacterial burden. We also observed improved survival when mice were treated with a combination of FY1 and MEDI4893* late during the course of postinfluenza MRSA pneumonia. In conclusion, both FY1 and MEDI4893* prolong survival when used in a murine model of postinfluenza MRSA pneumonia, suggesting pathogen-specific mAbs as a possible therapeutic in the context of bacterial superinfection.

Preventing lung pathology and mortality in rabbit Staphylococcus aureus pneumonia models with cytotoxin-neutralizing monoclonal IgGs penetrating the epithelial lining fluid.

Staphylococcus aureus pneumonia is associated with high mortality irrespective of antibiotic susceptibility. Both MRSA and MSSA strains produce powerful cytotoxins: alpha-hemolysin(Hla) and up to five leukocidins - LukSF-PV, HlgAB, HlgCB, LukED and LukGH (LukAB) - to evade host innate defense mechanisms. Neutralizing cytotoxins has been shown to provide survival benefit in rabbit S. aureus pneumonia models. We studied the mechanisms of protection of ASN100, a combination of two human monoclonal antibodies (mAbs), ASN-1 and ASN-2, that together neutralize Hla and the five leukocidins, in rabbit MRSA and MSSA pneumonia models. Upon prophylactic passive immunization, ASN100 displayed dose-dependent increase in survival and was fully protective against all S. aureus strains tested at 5 or 20 mg/kg doses. Macroscopic and microscopic lung pathology, edema rate, and bacterial burden were evaluated 12 hours post infection and reduced by ASN100. Pharmacokinetic analysis of ASN100 in bronchoalveolar-lavage fluid from uninfected animals detected efficient penetration to lung epithelial lining fluid reaching peak levels between 24 and 48 hours post dosing that were comparable to the mAb concentration measured in serum. These data confirm that the ASN100 mAbs neutralize the powerful cytotoxins of S. aureus in the lung and prevent damage to the mucosal barrier and innate immune cells.

STAT2 Signaling Regulates Macrophage Phenotype During Influenza and Bacterial Super-Infection.

Influenza is a common respiratory virus that infects between 5 and 20% of the US population and results in 30,000 deaths annually. A primary cause of influenza-associated death is secondary bacterial pneumonia. We have previously shown that influenza induces type I interferon (IFN)-mediated inhibition of Type 17 immune responses, resulting in exacerbation of bacterial burden during influenza and Staphylococcus aureus super-infection. In this study, we investigated the role of STAT2 signaling during influenza and influenza-bacterial super-infection in mice. Influenza-infected STAT2-/- mice had increased morbidity, viral burden, and inflammation when compared to wild-type mice. Despite an exaggerated inflammatory response to influenza infection, we found increased bacterial control and survival in STAT2 deficient mice during influenza-MRSA super-infection compared to controls. Further, we found that increased bacterial clearance during influenza-MRSA super-infection is not due to rescue of Type 17 immunity. Absence of STAT2 was associated with increased accumulation of M1, M2 and M1/M2 co-expressing macrophages during influenza-bacterial super-infection. Neutralization of IFNγ (M1) and/or Arginase 1 (M2) impaired bacterial clearance in Stat2-/- mice during super-infection, demonstrating that pulmonary macrophages expressing a mixed M1/M2 phenotype promote bacterial control during influenza-bacterial super-infection. Together, these results suggest that the STAT2 signaling is involved in suppressing macrophage activation and bacterial control during influenza-bacterial super-infection. Further, these studies reveal novel mechanistic insight into the roles of macrophage subpopulations in pulmonary host defense.

Immunogene therapy with fusogenic nanoparticles modulates macrophage response to Staphylococcus aureus.

The incidence of adverse effects and pathogen resistance encountered with small molecule antibiotics is increasing. As such, there is mounting focus on immunogene therapy to augment the immune system's response to infection and accelerate healing. A major obstacle to in vivo gene delivery is that the primary uptake pathway, cellular endocytosis, results in extracellular excretion and lysosomal degradation of genetic material. Here we show a nanosystem that bypasses endocytosis and achieves potent gene knockdown efficacy. Porous silicon nanoparticles containing an outer sheath of homing peptides and fusogenic liposome selectively target macrophages and directly introduce an oligonucleotide payload into the cytosol. Highly effective knockdown of the proinflammatory macrophage marker IRF5 enhances the clearance capability of macrophages and improves survival in a mouse model of Staphyloccocus aureus pneumonia.

Severe Pneumonia Caused by Coinfection With Influenza Virus Followed by Methicillin-Resistant Staphylococcus aureus Induces Higher Mortality in Mice.

Background: Coinfection with influenza virus and bacteria is a major cause of high mortality during flu pandemics. Understanding the mechanisms behind such coinfections is of utmost importance both for the clinical treatment of influenza and the prevention and control of epidemics. Methods: To investigate the cause of high mortality during flu pandemics, we performed coinfection experiments with H1N1 influenza virus and Staphylococcus aureus in which mice were infected with bacteria at time points ranging from 0 to 7 days after infection with influenza virus. Results: The mortality rates of mice infected with bacteria were highest 0-3 days after infection with influenza virus; lung tissues extracted from these co-infected mice showed higher infiltrating cells and thicker lung parenchyma than lung samples from coinfected mice in which influenza virus was introduced at other times and sequences. The levels of interferon (IFN)-γ, tumor necrosis factor (TNF)-α, interleukin (IL)-8, and IL-6 in the 0-3 day coinfected group were significantly higher than those in the other groups (p < 0.01), as were the mRNA levels of IFN-γ, IL-6, and TNF-α. Coinfection with influenza virus and S. aureus led to high mortality rates that are directly dependent on the sequence and timing of infection by both pathogens. Moreover, coinfection following this particular schedule induced severe pneumonia, leading to increased mortality. Conclusions: Our data suggest that prevention of bacterial co-infection in the early stage of influenza virus infection is critical to reducing the risk of clinical mortality.

Washing older blood units before transfusion reduces plasma iron and improves outcomes in experimental canine pneumonia.

In a randomized controlled blinded trial, 2-year-old purpose-bred beagles (n = 24), with Staphylococcus aureus pneumonia, were exchanged-transfused with either 7- or 42-day-old washed or unwashed canine universal donor blood (80 mL/kg in 4 divided doses). Washing red cells (RBC) before transfusion had a significantly different effect on canine survival, multiple organ injury, plasma iron, and cell-free hemoglobin (CFH) levels depending on the age of stored blood (all, P < .05 for interactions). Washing older units of blood improved survival rates, shock score, lung injury, cardiac performance and liver function, and reduced levels of non-transferrin bound iron and plasma labile iron. In contrast, washing fresh blood worsened all these same clinical parameters and increased CFH levels. Our data indicate that transfusion of fresh blood, which results in less hemolysis, CFH, and iron release, is less toxic than transfusion of older blood in critically ill infected subjects. However, washing older blood prevented elevations in plasma circulating iron and improved survival and multiple organ injury in animals with an established pulmonary infection. Our data suggest that fresh blood should not be washed routinely because, in a setting of established infection, washed RBC are prone to release CFH and result in worsened clinical outcomes.

Improved outcome of ventilator-associated pneumonia caused by methicillin-resistant Staphylococcus aureus in a trauma population.

BACKGROUND: The treatment of ventilator-associated pneumonia (VAP) secondary to methicillin-resistant Staphylococcus aureus (MRSA) remains controversial. METHODS: We performed a review of all blunt trauma patients diagnosed with MRSA VAP from June 2005 to June 2011. VAP for the first 3 years was diagnosed by sputum aspiration and treated with vancomycin. For the last 3 years of the study period, VAP was diagnosed with bronchoalveolar lavage and treated with linezolid. RESULTS: MRSA VAP patients treated with vancomycin had an average hospital length of stay (LOS) of 49 days (range 9-99 days), an average intensive care unit (ICU) LOS of 43 days (range 6-98 days), and average ventilator days of 34.4 (range 3-76 days). Seventeen MRSA VAP patients treated with linezolid had an average hospital LOS of 27 days (range 11-61), an average ICU LOS of 22 days (range 10-42) days, and average ventilator days of 16.6 (range 2-42). CONCLUSIONS: Trauma patients who develop MRSA VAP appear to have fewer ventilator days and shorter ICU and hospital LOS when treated with linezolid.

Ventilator-associated pneumonia due to meticillin-resistant Staphylococcus aureus: risk factors and outcome in a large general hospital.

BACKGROUND: Data about risk factors and impact on outcome of methicillin-resistant S. aureus (MRSA) in unselected patients with ventilator-associated pneumonia (VAP) are limited. AIM: To assess predisposing factors and outcome of VAP due to MRSA in a large teaching institution. METHODS: Prospective study carried out over four years in the three adult ICUs of our hospital. Patients with MRSA-VAP were compared with those with bacterial VAP due to other microorganisms. FINDINGS: Overall, 474 episodes of bacterial VAP were collected. Significant differences between MRSA-VAP (111) and VAP due to other microorganisms (363) were found for median age (68 vs. 62 years), median APACHE II score (12 vs. 11), neurosurgery (5.4% vs. 13.8%), abdominal surgery (35% vs. 19%), prior treatment with any antibiotic (82.9% vs. 64.5%) and with imipenem (24% vs. 11%) at present admission before VAP, and pleural effusion (12% vs. 5%). Multivariate analysis adjusted for confounding factors showed that higher APACHE II score, prior treatment with any antibiotic and pleural effusion were independent risk factors for MRSA. As for treatment and outcome, the differences between MRSA-VAP and other VAP were inadequate empiric treatment (70% vs. 53%), median cost of antibiotics per episode (€974 vs. €726), and in-hospital mortality (60% vs. 47%). At multivariate analysis, however, MRSA was not found to be an independent risk factor for mortality. CONCLUSION: MRSA is a common cause of VAP. Underlying conditions predispose to its high mortality.

Clinical factors affecting the efficacy of vancomycin in methicillin-resistant Staphylococcus aureus pneumonia.

OBJECTIVE: Methicillin-resistant Staphylococcus aureus (MRSA) is a major nosocomial pathogen. Patients with risk factors such as long hospital admission and compromised hosts are prone to MRSA infection, particularly MRSA pneumonia that is not resolved effectively and causes significant mortality. To identify the factors affecting the efficacy of vancomycin (VCM) therapy on MRSA pneumonia, a retrospective investigation was carried out. METHODS: Severity rating of pneumonia, pharmacokinetic parameters of VCM, clinical improvement following VCM therapy, clinical data and patient's background were investigated in 40 patients from January 2003 to March 2008. The outcome was evaluated 30 days after the initiation of VCM therapy, and multivariate logistic regression analysis was performed. RESULTS: The 30 day mortality rate was 15.0% (6 patients). As a result of multivariate logistic regression analysis, underlying malignancy and parenteral nutrition as the route of feeding during VCM therapy (odds ratio (OR) = 22.3, 95% confidence interval (CI) = 1.55-322; OR = 12.6, 95% CI = 1.15-139, respectively) were found to be significant factors affecting the survival. No pharmacokinetic parameters of VCM and severity of pneumonia were significant. CONCLUSION: Underlying malignancy and parenteral nutrition, which were associated with nutrition and the immune system, were found to affect the survival after 30 days of VCM therapy.

Effect of linezolid compared with glycopeptides in methicillin-resistant Staphylococcus aureus severe pneumonia in piglets.

OBJECTIVES: To investigate if compared with glycopeptides, antimicrobial therapy (AMT) with linezolid (LZD) improves the outcome in methicillin-resistant Staphylococcus aureus (MRSA) experimental pneumonia in mechanically ventilated piglets. METHODS: The MRSA minimal inhibitory concentration (MIC) was 0.5 for vancomycin (VAN), 0.25 for teicoplanin (TEI), and 2.0 microg/mL for LZD was inoculated in Largewhite-Landrace piglets divided into five groups. One group (n = 6) did not receive mechanical ventilation (MV) or AMT. Those in the remaining groups received MV and VAN (n = 9), TEI (n = 7), LZD (n = 9), or no AMT (n = 7). Plasma and BAL tumor necrosis factor-alpha, interleukin-6, and C-reactive protein (CRP) concentrations, postmortem lung pathology, cultures (lung, blood, and BAL) and plasma, epithelial lining fluid (ELF), and lung antibiotic concentrations were evaluated. MEASUREMENTS AND MAIN RESULTS: All piglets developed severe pneumonia; lung pathology score was lower in those receiving LZD vs those receiving glycopeptides (p = 0.049) or no AMT (p = 0.037). Serum CRP and serum and BAL cytokines increased; there were no differences between the groups. Fourteen died spontaneously at 44.4 +/- 16.8 h; the remaining 24 were killed after 72 to 96 h. The concentrations of the antimicrobial agents tested in 15 piglets were higher than the MIC for the three antimicrobial agents in peak and trough plasma, ELF, and lung specimens. Survival at 72 h was higher in the LZD comparing with the no-AMT group. CONCLUSIONS: Inoculation produced severe MRSA pneumonia. LZD AMT was associated with lower pathology score, better survival, and a trend to better clearance of MRSA, not attributable exclusively to pharmacokinetic or pharmacodynamic reasons.

Risk factors and evolution of Ventilator-associated pneumonia by Staphylococcus aureus sensitive or resistant to oxacillin in patients at the intensive care unit of a Brazilian University Hospital

This study investigated the participation and risk factors of VAP by resistant (ORSA) or sensitive (OSSA) S. aureus to oxacillin and evaluated the implications of adequate or inadequate empirical antimicrobial therapeutics in its evolution in patients interned in a mixing ICU of adults. A patient control-case study with PAVs by ORSA and OSSA was carried out from May 2005 to April 2007 involving 993 patients. VAP was defined based on clinical, radiological, and microbiological (> 106 CFU/mL count in the tracheal aspirate) criteria. Four hundred and seventy four (47.7 percent) patients were submitted to mechanical ventilation with 141 (29.7 percent) VAPs, with S. aureus as the most frequent agent (41.2 percent). The phenotype ORSA accounted for 47.5 percent and OSSA for 52.5 percent, predominant in late-onset VAPs with frequencies of 93.1 percent and 68.7 percent, respectively. Age > 60, use of corticoid and previous antibiotic therapy were related (p<0.05) with the development of VAP by ORSA. Mortality rate was higher (p>0.05) in the group with VAP by ORSA (37.9 percent). S. aureus was the main agent of VAPs, around half by ORSA, associated with age, late-onset VAP development and previous use of antibiotics and corticoids, but with no significant difference in mortality compared with VAP by OSSA.

Impact of methicillin resistance on outcome of Staphylococcus aureus ventilator-associated pneumonia.

The impact of methicillin resistance on morbidity and mortality of patients suffering from severe Staphylococcus aureus infections remains highly controversial. We analyzed a retrospective cohort of 97 patients with methicillin-susceptible and 74 patients with methicillin-resistant Staphylococcus aureus ventilator-associated pneumonia (VAP). Initial empiric antibiotic therapy was appropriate for every patient. Patients with methicillin-resistant Staphylococcus aureus VAP were older, had higher disease-severity scores, and had been on mechanical ventilation longer at onset of VAP. Factors associated with 28-day mortality retained by multivariate logistic regression analysis were: age (odds ratio [OR] = 1.05, 95% confidence interval [CI], 1.02-1.08, p = 0.001) and Day 1 organ dysfunctions or infection (ODIN) score (OR = 1.90, 95% CI, 1.31-2.78, p = 0.001), but not methicillin resistance (OR = 1.72, 95% CI, 0.73-4.05, p = 0.22). The percentages of infection relapse or superinfection did not differ significantly between the two patient groups. In conclusion, after controlling for clinical and physiologic heterogeneity between groups, methicillin resistance did not significantly affect 28-day mortality of patients with Staphylococcus aureus VAP receiving appropriate antibiotics.

Staphylococcus aureus bacteremic pneumonia: differences between community and nosocomial acquisition.

OBJECTIVE: The aim of the study was to ascertain the clinical and epidemiologic characteristics of patients with nosocomial or community-acquired Staphylococcus aureus bacteremic pneumonia. METHODS: A prospective study of 134 cases diagnosed between January 1990 and December 1995 was performed. RESULTS: Fifty cases involved primary bacteremic pneumonias, of which 80% were nosocomial (the majority, 72%, in intensive care unit patients, of whom 57% were post-surgery). Of the 84 cases of secondary pneumonia, 36 were non-intravenous drug users (78% nosocomial, of whom 43% were in the intensive care unit), and 48 cases were intravenous drug users (98% community-acquired). CONCLUSIONS: Nosocomial S. aureus bacteremic pneumonia was especially frequent in intensive care unit patients (68.1%), and community-acquired pneumonia in intravenous drug users (72.3%). In non-intravenous drug users, clinical outcome and mortality were similar for nosocomial and community-acquired pneumonia.

Pulmonary infiltrates in patients receiving long-term glucocorticoid treatment: etiology, prognostic factors, and associated inflammatory response.

BACKGROUND: Glucocorticoid treatment alters immunoregulatory defense mechanisms and may therefore favor the development of different pulmonary infections. METHODS: The etiology, prognostic factors, and associated inflammatory response of pulmonary infiltrates in 33 patients receiving long-term glucocorticoid treatment (LTGCT) were prospectively evaluated. RESULTS: Aspergillus spp (n = 9, 31%) and Staphylococcus spp (n = 6, 21%) were the most common causative agents. Using different diagnostic techniques, we obtained a specific diagnosis in 28 of 33 episodes (85%) of pulmonary infiltrates. Bronchoscopic techniques provided the diagnosis in 64% of the cases. Crude mortality was 45%. Variables associated with mortality were as follows: age > 64 years, bilateral radiographic involvement, delay in diagnosis, inappropriate empirical treatment, Simplified Acute Physiology Score (SAPS) II > or = 25, and requirement for mechanical ventilation (MV). SAPS II > or = 25 (odds ratio [OR], 16; 95% confidence interval, 1 to 260) and MV requirement (OR, 50; 95% confidence interval, 2 to 360) were also significant on multivariate analysis. Pulmonary infections were associated with an increase in the concentration of relevant inflammatory cytokines such as tumor necrosis factor-alpha and interleukin-6 both in serum and BAL. This local and systemic inflammatory response was attenuated when compared with the response observed in patients with pulmonary infections but without glucocorticoid treatment or receiving glucocorticoids for a short period of time (< 9 days). CONCLUSIONS: Pulmonary infiltrates in patients receiving LTGCT are often caused by fungi and Gram-positive cocci, and are associated with attenuated local and systemic inflammatory response. Although in most cases, sputum cultures and bronchoscopic techniques are diagnostic, the associated mortality is high, particularly in those requiring MV.

Lower respiratory tract infections following cardiac arrest and cardiopulmonary resuscitation.

All episodes of lower respiratory tract infection that developed among 96 patients surviving for > 24 hours after cardiac arrest were prospectively studied over an 18-month period. Pneumonia developed in 23 (24.0%) of patients after a mean of 7 days (SD, +/- 6.2 days). The development of four superinfections raised the cumulative incidence to 28.1%. Purulent tracheobronchitis was diagnosed in three instances. The causative agent of pneumonia was identified in 18 episodes, three of which were polymicrobial. Gram-positive cocci represented 57.1% of isolates, and Staphylococcus aureus--the most frequently isolated microorganism in this population--accounted for two-thirds of all gram-positive cocci. Pseudomonas aeruginosa was isolated in six episodes, five of which were associated with previous antibiotic use. Nine (39.1%) of the 23 patients in the group with pneumonia died, but only one of these deaths was considered to be directly related to pneumonia. In conclusion, pneumonia is a common complication of patients surviving cardiac arrest, but, with adequate treatment, its influence on outcome is marginal. Gram-positive cocci are the predominant pathogens, although infection with P. aeruginosa should be considered among patients receiving antibiotics.

Ventilator-associated pneumonia by Staphylococcus aureus. Comparison of methicillin-resistant and methicillin-sensitive episodes.

All episodes of ventilator-associated pneumonia (VAP) caused by Staphylococcus aureus were prospectively analyzed for a 30-mo period. Methicillin-sensitive S. aureus (MSSA) was isolated in 38 episodes and methicillin-resistant S. aureus (MRSA) in 11 others. The two groups were similar regarding sex, severity of underlying diseases, prior surgery, and presence of renal failure, diabetes, cardiopathy, and coma. MRSA-infected persons were more likely to have received steroids before developing infection (relative risk [RR] = 3.45, 95% confidence interval [CI] = 1.38-8.59), to have been ventilated > 6 d (RR = 2.03, 95% CI = 1.36-3.03), to have been older than 25 yr (RR = 1.50, 95% CI = 1.09-2.06), and to have had preceding chronic obstructive pulmonary disease (RR = 2.76, 95% CI = 0.89-8.56) than MSSA-infected patients. MSSA-infected persons were more likely than MRSA-infected patients to have cranioencephalic trauma (RR = 1.94, 95% CI = 1.22-3.09). All patients with MRSA VAP had previously received antibiotics, compared with only 21.1% of those with MSSA infection (p < 0.000001). The incidence of empyema was similar in both groups; nevertheless, the presence of bacteremia and septic shock was more frequent in the MRSA group. Finally, mortality directly related to pneumonia was significantly higher among patients with MRSA episodes (RR = 20.72, 95% CI = 2.78-154.35). This analysis was repeated for monomicrobial episodes, and the difference remained statistically significant. We conclude that MRSA and MSSA strains infect patients with different demographic profiles; previous antibiotic therapy is the most important risk factor for developing MRSA infection.(ABSTRACT TRUNCATED AT 250 WORDS)

Emergency pulmonary resection for pneumonia. High morbidity and mortality.

Emergency pulmonary resection was performed because of complicated pneumonia in eight patients (5 pneumonectomies, 2 lobectomies, 1 bilobectomy) over a 2-year period. The patients' age range was 5 months to 43 years. The indications were rapid aggravation of respiratory insufficiency in children with staphylococcal pneumonia and enlarging pneumatoceles, and massive hemoptysis in patients with chronic destructive pneumonia. Two patients died after pneumonectomy, one from contralateral aspiration and one from cardiogenic shock. Postoperative complications occurred in four cases--bronchopleural fistula and pyopneumothorax in three and thoracic empyema with massive chest-wall infection in one. Only two patients had an uneventful postoperative course. Complications of pulmonary necrosis in pneumonia may dictate urgent pulmonary resection, often pneumonectomy. Surgery will be life-saving in most cases, but high morbidity is to be expected.

[The incidence of lung infection in patients with mucoviscidosis and the disease course with various pathogen spectra]. / Zur Häufigkeit der Lungeninfektion bei Patienten mit Mukoviszidose und zum Krankheitsverlauf bei unterschiedlichem Erregerspektrum.

A retrospective review on the frequency of lung infections by the most important organisms Staphylococcus aureus and Pseudomonas aeruginosa in patients with cystic fibrosis in the GDR during the period from 1981 to 1985 revealed an average infectious rate of 58.6 per cent by Staphylococcus and of 26.9 per cent by Pseudomonas respectively. A distinct increase of the infections by Pseudomonas could only be documented from 1981 to 1982, later on the infectious rate remained nearly equal and showed only a peak value of 35.6 per cent in 1983. Thus the frequency of infections by Pseudomonas is significantly lower in the GDR than in most other countries. The comparison of the course of the disease in patients with permanent lung infection during 4 or 5 years established a mortality rate of a double amount in the group of patients with Pseudomonas colonisation versus the group with Staphylococcus colonisation. Otherwise no significant difference could be stated in the mean age of the beginning of lung infection (Staphylococcus = 9.7 years of age - Pseudomonas = 10.1 years of age). Analysing the pulmonary x-ray findings we found a significantly more rapid deterioriation during the follow-up period in patients with permanent Pseudomonas infection than in patients with permanent Staphylococcus infection, whereas the evolution of body height and weight did not take different course.