David J. Feola

Polymyxin B Sulfate and Colistin: Old Antibiotics for Emerging Multiresistant Gram-Negative Bacteria

BACKGROUND: Polymyxin B sulfate and colistin, also known as colistimethate, have not been used for many years because less toxic antimicrobials are available. Gram-negative bacteria that are resistant to the aminoglycosides, β-lactams, and fluoroquinolones are becoming more common. These bacteria are often susceptible to the polymyxins. OBJECTIVE: To present a review of the chemistry, antibacterial spectrum, dosing, pharmacokinetics, toxicity, and indications for polymyxin B sulfate and colistin. DATA SOURCE: A MEDLINE search (1966–1998) of the English-language literature was performed to identify primary literature on the polymyxins. Older citations (1949–1965) were identified through the bibliographies of these articles. STUDY SELECTION: All available reports of in vitro antibacterial activity, animal and clinical trials, and case reports were reviewed. DATA SYNTHESIS: The polymyxins are amphipathic molecules that interact with lipopolysaccharide in the bacterial outer membrane. They have potent antiendotoxic properties and antibacterial activity against Pseudomonas aeruginosa and many of the Enterobacteriaceae. Polymyxin B and colistin are usually given at a dose of 1.5–2.5 and 5 mg/kg/d, respectively, in two divided doses. Dosing must be altered in renal failure since the kidney is the primary route of elimination. Distribution into pleural fluid, joints, and cerebrospinal fluid is poor. Toxic effects involve the kidney and central nervous system. The polymyxins are recommended for serious systemic infections caused by gram-negative bacteria that are resistant to other agents. CONCLUSIONS: Polymyxin B sulfate and colistin have a role in the therapy of multidrug-resistant gram-negative bacterial infections.

Azithromycin alters macrophage phenotype

OBJECTIVES To investigate the in vitro effects of azithromycin on macrophage phenotype. Utilizing a mouse macrophage cell line (J774), we examined the effect of azithromycin on the properties that define classical macrophage activation (M1) and alternative macrophage activation (M2). METHODS J774 cells were cultured in the presence of azithromycin and stimulated with classical activation [interferon-gamma (IFNgamma)] and alternative activation [interleukin (IL)-4 and IL-13] cytokines along with lipopolysaccharide (LPS). Macrophages were analysed for inflammatory cytokine production, surface receptor expression, inducible nitric oxide synthase (iNOS) protein expression and arginase activity. RESULTS Azithromycin altered the overall macrophage phenotype. Azithromycin-treated J774 macrophages demonstrated a significantly reduced production of the pro-inflammatory cytokines IL-12 and IL-6, increased production of the anti-inflammatory cytokine IL-10 and decreased the ratio of IL-12 to IL-10 by 60%. Receptor expression indicative of the M2 phenotype (mannose receptor and CD23) was increased, and receptor expression typically up-regulated in M1 cells (CCR7) was inhibited. The presence of azithromycin increased arginase (M2 effector molecule) activity 10-fold in cells stimulated with IFNgamma and LPS, and iNOS protein (M1 effector molecule) concentrations were attenuated by the drug. CONCLUSIONS These data provide evidence that azithromycin affects the inflammatory process at the level of the macrophage and shifts macrophage polarization towards the alternatively activated phenotype. This recently defined M2 phenotype has been described in conditions in which pulmonary inflammation and fibrosis are major determinants of clinical outcome, but the concept of antibiotics altering macrophage phenotype has not yet been critically evaluated.

Azithromycin Alters Macrophage Phenotype and Pulmonary Compartmentalization during Lung Infection with Pseudomonas

ABSTRACT Infection with mucoid strains of Pseudomonas aeruginosa in chronic inflammatory diseases of the airway is difficult to eradicate and can cause excessive inflammation. The roles of alternatively activated and regulatory subsets of macrophages in this pathophysiological process are not well characterized. We previously demonstrated that azithromycin induces an alternatively activated macrophage-like phenotype in vitro. In the present study, we tested whether azithromycin affects the macrophage activation status and migration in the lungs of P. aeruginosa-infected mice. C57BL/6 mice received daily doses of oral azithromycin and were infected intratracheally with a mucoid strain of P. aeruginosa. The properties of macrophage activation, immune cell infiltration, and markers of pulmonary inflammation in the lung interstitial and alveolar compartments were evaluated postinfection. Markers of alternative macrophage activation were induced by azithromycin treatment, including the surface expression of the mannose receptor, the upregulation of arginase 1, and a decrease in the production of proinflammatory cytokines. Additionally, azithromycin increased the number of CD11b+ monocytes and CD4+ T cells that infiltrated the alveolar compartment. A predominant subset of CD11b+ cells was Gr-1 positive (Gr-1+), indicative of a subset of cells that has been shown to be immunoregulatory. These differences corresponded to decreases in neutrophil influx into the lung parenchyma and alteration of the characteristics of peribronchiolar inflammation without any change in the clearance of the organism. These results suggest that the immunomodulatory effects of azithromycin are associated with the induction of alternative and regulatory macrophage activation characteristics and alteration of cellular compartmentalization during infection.

Pathogenesis of Bronchopulmonary Dysplasia

Bronchopulmonary dysplasia (BPD) refers to a heterogeneous group of lung disorders in infants that is commonly associated with prematurity and surfactant deficiency. BPD results from the complex interplay between impairments in the premature lung such as surfactant deficiency, perinatal insults such as infection, and damage resulting from supportive care of the infant due to barotrauma or volutrauma from mechanical ventilation and oxygen toxicity from supplemental oxygen administration. These factors result in chronic inflammation in the infant lung with recurring cycles of lung damage and repair that may impair alveolarization and vascularization in the developing lungs. As our insight in how to treat BPD improves along with the ability to do so with developing technology and therapies, the underlying pathogenesis will also change. The term ‘new’ BPD is now commonly used, to describe the changes seen in the post-surfactant era. This discussion reviews the pathogenesis of BPD according to the current medical literature.

Phytosterols differentially influence ABC transporter expression, cholesterol efflux and inflammatory cytokine secretion in macrophage foam cells

Phytosterol supplements lower low-density lipoprotein (LDL) cholesterol, but accumulate in vascular lesions of patients and limit the anti-atherosclerotic effects of LDL lowering in apolipoprotein E (Apo E)-deficient mice, suggesting that the cholesterol-lowering benefit of phytosterol supplementation may not be fully realized. Individual phytosterols have cell-type specific effects that may be either beneficial or deleterious with respect to atherosclerosis, but little is known concerning their effects on macrophage function. The effects of phytosterols on ABCA1 and ABCG1 abundance, cholesterol efflux and inflammatory cytokine secretion were determined in cultured macrophage foam cells. Among the commonly consumed phytosterols, stigmasterol increased expression of ABCA1 and ABCG1 and increased efflux of cholesterol to apolipoprotein (Apo) AI and high-density lipoprotein (HDL). Campesterol and sitosterol had no effect on ABCA1 or ABCG1 levels. Sitosterol had no effect on cholesterol efflux to Apo AI or HDL, whereas campesterol had a modest but significant reduction in cholesterol efflux to HDL in THP-1 macrophages. Whereas stigmasterol blunted aggregated LDL (agLDL) induced increases in tumor necrosis factor (TNF)-α, interleukin (IL)-6 and IL-1β secretion, sitosterol exacerbated these effects. The presence of campesterol had no effect on agLDL-induced inflammatory cytokine secretion from THP-1 macrophages. In conclusion, the presence of stigmasterol in modified lipoproteins promoted cholesterol efflux and suppressed inflammatory cytokine secretion in response to lipid loading in macrophage foam cells. While campesterol was largely inert, the presence of sitosterol increased the proinflammatory cytokine secretion.

Characterization of macrophage activation states in patients with cystic fibrosis

BACKGROUND Chronic airway inflammation characterizes patients with cystic fibrosis (CF). The role of alternative macrophage activation in this disease course is unknown. OBJECTIVE We evaluated markers of alternative and classical macrophage activation in the lungs of patients with CF and evaluated these characteristics in the context of Pseudomonas aeruginosa (PA) infection, immunomodulatory drug therapy and pulmonary function. METHODS Bronchoalveolar lavage or spontaneously expectorated sputum samples were collected from 48 CF patients. Clinical data were related to macrophage surface expression of mannose receptor (MR) (up-regulated in alternatively activated macrophages) and TLR4 (up-regulated in classically activated macrophages). Also, the activity of the alternatively activated macrophage effector molecule arginase was compared among patient groups, and pro- and anti-inflammatory cytokines produced by alternatively and classically activated macrophages were measured. RESULTS There were significant differences between PA-infected and -uninfected patients in several clinical measurements. PA-infected patients exhibited increased use of azithromycin, up-regulation of MR on CD11b+ cells and increased arginase activity in their lung samples, and had a strong inverse relationship between MR and arginase activity to FEV(1). Upon further analysis, PA-infected patients who were treated with azithromycin had the highest arginase activity and the highest number of macrophages that were MR+TLR4-, and both of these markers were inversely related to the FEV(1). CONCLUSIONS Our findings suggest an increase in both MR and arginase expression as pulmonary function declines in PA-infected patients with CF. These markers of an alternatively activated macrophage phenotype give cause for future study to define the function of macrophage activation states in the CF lung.

Aerosolized amphotericin for the treatment of allergic bronchopulmonary aspergillosis.

Allergic bronchopulmonary aspergillosis (ABPA) is a complex hypersensitivity reaction to Aspergillus fumigatus that occur frequently in patients with cystic fibrosis (CF). Recurrent episodes of bronchial obstruction, inflammation, and mucoid impaction occur in ABPA and results in bronchiectasis, fibrosis, and respiratory failure. The treatment of ABPA includes corticosteroids to reduce the acute inflammation and intraconazole to reduce the fungal colonization load in order to reduce lung injury. This case discusses the successful use of aerosolized amphotericin B for the treatment of ABPA in a 14‐year‐old patient with CF listed for lung transplant. The patient required fewer hospitalizations, and both oral corticosteroids and anti‐fungal therapy were eventually stopped. Pediatr Pulmonol. 2010;45:1145–1148.

IMPACT OF AZITHROMYCIN TREATMENT ON MACROPHAGE GENE EXPRESSION IN SUBJECTS WITH CYSTIC FIBROSIS

BACKGROUND Azithromycin treatment improves clinical parameters in patients with CF, and alters macrophage activation from a pro-inflammatory (M1) phenotype to a pro-fibrotic, alternatively activated (M2) phenotype. The transcriptional profile of cells from patients receiving azithromycin is unknown. METHODS Gene expression in association with macrophage polarization, inflammation, and tissue remodeling was assessed from sputum samples collected from patients with CF. Transcriptional profiles and clinical characteristics, including azithromycin therapy, were compared. RESULTS Expression of NOS2 and TNFα was decreased in subjects receiving azithromycin, whereas expression of M2-associated genes was unaffected. Principal component analysis revealed gene expression profiles consistent with M1- (MMP9, NOS2, and TLR4) or M2-polarization (CCL18, fibronectin, and MR1) in select subject groups. These expression signatures did not significantly correlate with clinical characteristics. CONCLUSIONS Pro-inflammatory gene expression was low in subjects receiving AZM. Genes were stratified into groupings characteristic of M1- or M2-polarization, suggesting that overall polarization status is distinct among patient groups.

Metronidazole-induced pancreatitis in a patient with recurrent vaginal trichomoniasis.

Recurrent acute pancreatitis associated with metronidazole developed in a 49‐year‐old woman who was taking the drug as treatment for vaginal trichomoniasis. The lack of alternative effective therapies for trichomoniasis governed the decision to rechallenge the patient with metronidazole despite a vague history of this reaction on a previous occasion. Six reports of this reaction are found in the literature. The patient was admitted to the hospital 12 hours after taking a single dose of metronidazole. Severe epigastric pain and elevated amylase and lipase concentrations led to the diagnosis of acute pancreatitis, although results of an abdominal ultrasound were unremarkable. The patient made a full recovery. Although this reaction occurs infrequently, this case report illustrates the need to develop additional therapies for treatment of trichomoniasis.

B Lymphocytes Are Required during the Early Priming of CD4+ T Cells for Clearance of Pneumocystis Infection in Mice

B cells play a critical role in the clearance of Pneumocystis. In addition to production of Pneumocystis-specific Abs, B cells are required during the priming phase for CD4+ T cells to expand normally and generate memory. Clearance of Pneumocystis was found to be dependent on Ag specific B cells and on the ability of B cells to secrete Pneumocystis-specific Ab, as mice with B cells defective in these functions or with a restricted BCR were unable to control Pneumocystis infection. Because Pneumocystis-specific antiserum was only able to partially protect B cell–deficient mice from infection, we hypothesized that optimal T cell priming requires fully functional B cells. Using adoptive transfer and B cell depletion strategies, we determined that optimal priming of CD4+ T cells requires B cells during the first 2–3 d of infection and that this was independent of the production of Ab. T cells that were removed from Pneumocystis-infected mice during the priming phase were fully functional and able to clear Pneumocystis infection upon adoptive transfer into Rag1−/− hosts, but this effect was ablated in mice that lacked fully functional B cells. Our results indicate that T cell priming requires a complete environment of Ag presentation and activation signals to become fully functional in this model of Pneumocystis infection.