Pathogenesis Of Bacterial Pneumonia Research Articles

Co-infections with respiratory viruses in dogs with bacterial pneumonia.

BackgroundBacterial pneumonia (BP) is an inflammation of the lower airways and lung parenchyma secondary to bacterial infection. The pathogenesis of BP in dogs is complex and the role of canine respiratory viruses has not been fully evaluated.ObjectivesThe aim of this study was to investigate the occurrence of viral co‐infections in dogs with BP and to assess demographic or clinical variables as well as disease severity associated with viral co‐infections.AnimalsTwenty household dogs with BP caused by opportunistic bacteria and 13 dogs with chronic (>30 days) tracheobronchitis caused by Bordetella bronchiseptica (BBTB).MethodsProspective cross‐sectional observational study. Diagnosis was confirmed by clinical and laboratory findings, diagnostic imaging, and cytologic and microbiologic analysis of bronchoalveolar lavage or transtracheal wash fluid. Canine parainfluenza virus (CPIV), canine adenovirus, canine herpes virus, canine influenzavirus, canine distemper virus, canine respiratory coronavirus (CRCoV) and canine pneumovirus, as well as B. bronchiseptica and Mycoplasma spp. were analyzed in respiratory samples using PCR assays.Results CPIV was detected in 7/20 and CRCoV in 1/20 dogs with BP. Respiratory viruses were not detected in dogs with BBTB. There were no significant differences in clinical variables between BP dogs with and without a viral co‐infection.Conclusion and Clinical ImportanceRespiratory viruses were found frequently in dogs with BP and may therefore play an important role in the etiology and pathogenesis of BP. Clinical variables and disease severity did not differ between BP dogs with and without viral co‐infection.

Influenza A Virus Exacerbates Staphylococcus aureus Pneumonia in Mice by Attenuating Antimicrobial Peptide Production

Influenza A represents a significant cause of morbidity and mortality worldwide. Bacterial complications of influenza A confer the greatest risk to patients. TH17 pathway inhibition has been implicated as a mechanism by which influenza A alters bacterial host defense. Here we show that preceding influenza causes persistent Staphylococcus aureus infection and suppression of TH17 pathway activation in mice. Influenza does not inhibit S. aureus binding and uptake by phagocytic cells but instead attenuates S. aureus induced TH17 related antimicrobial peptides necessary for bacterial clearance in the lung. Importantly, exogenous lipocalin 2 rescued viral exacerbation of S. aureus infection and decreased free iron levels in the bronchoalveolar lavage from mice coinfected with S. aureus and influenza. These findings indicate a novel mechanism by which influenza A inhibits TH17 immunity and increases susceptibility to secondary bacterial pneumonia. Identification of new mechanisms in the pathogenesis of bacterial pneumonia could lead to future therapeutic targets.

Nouveautés et perspectives thérapeutiques des pneumonies acquises sous ventilation mécanique à Pseudomonas aeruginosa

Pseudomonas aeruginosa is frequently responsible for hospital-acquired pneumonia, especially in intensive care unit (ICU) patients. A foreseeable increase in antibiotic resistance, evolving faster than development of new antibiotics, favors the high morbidity and mortality of these infections. While former molecules are reemerging due to their sustained efficacy like colistin, new antibiotics, new inhibitors of resistance as well as topical antibiotics by aerosol are currently developed to improve the available therapeutic options. Innovative research has emerged to develop alternatives for prevention and treatment of P. aeruginosa pneumonia. Antimicrobial peptides, carbon monoxidereleasing molecules, and pyocins should widen the field of antimicrobial molecules. New treatments aim to modulate P. aeruginosa phenotype by inhibiting bacterial adhesion and communication including macrolides to inhibit the quorum-sensing. Moreover, rediscovery of lytic bacteriophages, which are specific viruses inducing bacterial lysis, is recent in Western countries despite large-scale use in Eastern Europe following the Second World War. Bacteriophages may be suitable for the treatment of ventilator-associated pneumonia, especially if related to multidrug resistant P. aeruginosa. Finally, epidemiological and experimental data may lead us to focus on the role played by fungal colonization in the pathogenesis of bacterial pneumonia.

Herpetic tracheitis and polybacterial pneumonia in an immunocompetent young man: Is herpes tracheitis involved in the pathogenesis of bacterial pneumonia?

We report a 28-year-old immunocompetent man that after a course of corticoids developed a severe pneumonia in right lower lobe. A fiber-optic bronchoscopy showed a white membrane easily bloody on contact with bronchoscopy tube at trachea level. The tracheal biopsy showed typical cytopathological lesions of herpes simplex virus (HSV) and polymerase chain reaction was positive for type 1 HSV. Streptococcus viridans and Fusobacterium necrophorum grew in right bronchial secretion cultures. Clinical improvement was achieved after prolonged antibiotic therapy and before initiating treatment with acyclovir. Herpetic tracheitis could have been involved in the aspiration of oropharyngeal material that leaded to the development of this bacterial pneumonia.

Role of interleukin-8 in community-acquired pneumonia: relation to microbial load and pulmonary function.

SummaryIn pneumonia local phagocyte activation is crucial for clearing of pathogenic microorganisms. In this context alveolar macrophage interleukin-8 secretion, phagocyte oxidative response and concentrations of lavage proteins were quantified, including interleukin-8, in 31 patients with pneumonia, 13 age matched patients with peripheral lung consolidation and six healthy volunteers; these findings were related to the impairment of gas exchange and the bacterial load in the alveolar space. Increased interleukin-8 levels were found in bronchoalveolar lavage fluid (BALF) and in alveolar macrophage supernatants from patients with pneumonia (214 ng/105 AM±121 vs 71 ng/105 AM±35 and 66 ng/105 AM±30, p<0.05). Interleukin-8 release from alveolar macrophages correlated with the upregulated spontaneous luminol enhanced oxidative response of pulmonary phagocytes but not with the neutrophil count in BALF. In pneumonia patients a significant difference was found between patients with 104 or more colony forming units (CFU)/ml BALF of one pathogen and patients with less CFU or nonspecific microbiological results (261 ng/105 AM±89 vs 179 ng/105 AM±81 and 7.5 ng/ml BALF±17 vs 0.44 ng/ml BALF±1, p<0.05). Further, a negative correlation between interleukin-8 release of alveolar macrophages and the arterial pO2 at the time of BALF could be demonstrated (r=−0.47, p<0.05). The results demonstrate local cellular activation in community-acquired pneumonia, which is related to the bacterial load in the alveolar space and to impairment of gas exchange. This is consistent with the hypothesis that pulmonary phagocytes play a central role in the pathogenesis of bacterial pneumonia, contributing not only to bacterial clearing but also to local tissue damage.

Overwhelming pneumonia

Overwhelming pneumonias remain an important cause of morbidity and mortality. These illnesses may be rapidly fatal; thus, many patients are treated empirically. Although the various etiologic agents cannot be differentiated on the basis of radiographic appearance, epidemiologic information may give a clue to the cause. Community-acquired overwhelming pneumonias are usually due to pyogenic bacteria (especially Streptococcus pneumoniae), mycoplasma, mycobacteria, and fungi. Hospital-acquired pneumonias are usually due to aerobic gram-negative bacilli. If the patient is immunocompromised, Pneumocystis carinii, Candida, and Aspergillus must be considered. Choice of optimal antimicrobial therapy requires that a specific etiology be identified. Gram's stain of sputum is often helpful in the diagnosis of community-acquired pneumonia. Invasive diagnostic techniques such as bronchoscopy and open lung biopsy are often required in nosocomial pneumonias and pneumonias in immunocompromised patients.

Infections in the Elderly

This is a multiauthored book with a group of distinguished contributors. The topics begin with host defenses in the aged. There are chapters on antimicrobial agents and their pharmacology in the aged, the pathogenesis of bacterial pneumonia, community-acquired and nosocomial pneumonias, and immunization. There is a separate chapter on fever of unknown origin. Chapters on infectious diarrhea, abdominal infections, community-acquired bacteremia, infective endocarditis, bacterial meningitis, community-acquired urosepsis, nosocomial urinary tract infections, and pressure sores round out this book. The book is well set up. The type is pleasing to the eye and readable. The chapters are arranged in logical sequence. Important specific factual statements are well referenced, and all of the chapters have complete lists of references. The book is not profusely illustrated, but there is a moderate number of tables, which are very clearly laid out and easy to read and which make salient points. In the chapter on

Interrelationships of viral, mycoplasmal, and bacterial agents in uncomplicated pneumonia.

Minor viral respiratory infections have long been thought to play a role in the pathogenesis of bacterial pneumonia. Heffron (1) noted that the major evidence supporting this concept was supplied by the many studies in which a large proportion of patients reported symptoms of upper respiratory infection during the period preceding the onset of pneumonia. He concluded his consideration of this issue, however, with the statement that it was not clear that a virus infection is an essential prerequisite for the development of pneumonia in every instance or indeed possibly in any instance. Wood (2), on the other hand, stressed the importance of viral upper respiratory tract infections and the aspiration of infected secretions in the pathogenesis of pneumococcal pneumonia. Influenza is generally held to predispose to pulmonary bacterial infections, particularly with Diplococcus pneumoniae and Staphylococcus aureus (3). Rubeola is also known to be associated

MEDICAL NEWS

<h3>CALIFORNIA</h3><h3>Herzstein Medical Lectures.</h3> —These lectures were recently delivered at Stanford University School of Medicine, San Francisco, by Dr. William Barry Wood Jr., Busch professor of medicine, Washington University School of Medicine, St. Louis, whose theme, "Cellular Immunology of Acute Bacterial Infections," included "Pathogenesis of Bacterial Pneumonia," "Surface Phagocytosis," and "Cytodynamics of Bacteremia." <h3>Dr. Ada Hatcher Honored.</h3> —Dr. Ada L. Hatcher was unanimously chosen Inglewood's outstanding citizen for 1952. At the Armistice Day dinner, sponsored by the local American Legion post, she was presented with the Civic award for her contributions to civic betterment. Dr. Hatcher serves in the Southwest Community Health Clinic and was instrumental in establishing the Inglewood Branch of the American Cancer Society. <h3>COLORADO</h3><h3>Society News.</h3> —The Colorado Radiological Society has elected Dr. Wendell P. Stampfli, Denver, president; Dr. Thomas K. Mahan, Grand Junction, vice-president; Dr. William S. Curtis, Denver, secretary; and Dr. Vernon L. Bolton, Colorado