Term
| what are 2 patterns of acute bacterial pneumonia? |
|
Definition
| lobar pneumonia: fibrinosuppurative consolidation of a large portion of a lobe or an *entire lobe* and bronchopneumonia: patchy consolidation *around the bronchi* (eventually these foci may coalesce and give more of a lobar picture). often times there is an overlap/combination of the two patterns. |
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Term
| what is the first stage of lobar pneumonia? |
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Definition
| congestion, vasculature of the lungs become engorged, there may be intra-alveolar fluid w/few neutrophils and bacteria. the lungs in the first stage of lobar pneumonia are heavy and may weigh over 1000 g (normal: 300-350 g) due to infection/congestion/edema |
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Term
| what is the second stage of lobar pneumonia? |
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Definition
| red hepatization: massive confluent exudation w/RBCs, the lung takes on the gross appearance of the liver (loses its spongy structure and becomes firm) and neutrophils/fibring fill the alveolar spaces |
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Term
| what is the third stage of lobar pneumonia? |
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Definition
| gray hepatization: the lungs begin to lose RBCs (via disintegration) which are replaced by a fibrinosuppurative/fibrinopurulant exudate, producing a grayish brown cut surface |
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Term
| what is the fourth stage of lobar pneumonia? |
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Definition
| there is resolution of the consolidated exudate in the alveolar spaces, which undergoes progressive enzymatic digestion. this produces a granular semifluid debris which is resorbed, ingested by macrophages, coughed up, or organized by fibroblasts (this assumes the pt survives) |
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Term
| what characterizes bronchopneumonia? |
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Definition
| bronchopneumonia is consolidated areas of acute suppurative inflammation around the bronchi and tends to be more multifocal, multilobar, bilateral, and basal. it can involve one or both lobes of one lung or lobes of both lungs (often seen in lower lobes due to gravity). the classic lesions are 3-4 cm in diameter and have a dry granular gray to red yellow surface - often poorly delimited from the normal parenchyma. there may also be neutrophils filling the bronchi, bronchioles and alveolar spaces. |
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Term
| what are some of the complications associated with pneumonia? |
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Definition
| abscess formation (infection is localized, walled off and sequestered to certain section of the lung - can give rise to recurring infections), empyema (localized pleural infection), organization (fibrotic response if injury is severe enough - may impair the long term respiratory functions) and bacteremic dissemination (transfer of bacteria to peripheral circulation: septicemia, which can go to the heart valves, produce septic emboli, etc.) |
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Term
| what is the classic histological presentation of pneumonia? |
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Definition
| neutrophils in the alveoli (alveoli should be free of debris and neutrophils) |
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Term
| how does the lung tissue appear microscopically if affected by pneumonia? |
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Definition
| the alveoli are beginning to organize, fibrotic material accumulates, neutrophils accumulate |
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Term
| what is the most common *community acquired bacterial pneumoniae? |
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Definition
| strep pneumoniae - affects young, old, CHF, COPD, and DM pts |
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Term
| why do many people get false strep pneumoniae positives? |
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Definition
| strep pneumoniae is part of endogenous flora in 20% of people. blood cxs are more specific, but less sensitive. |
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Term
| what kind of pneumonia does strep pneumoniae cause? |
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Definition
|
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Term
| how do strep pneumoniae appear? |
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Definition
| gram positive, lancet-shaped diplococci |
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Term
| how do pts infected with strep pneumoniae in their lungs present? |
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Definition
| fever, chills, cough, and CP |
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Term
| what do pneumococcal vaccines contain? |
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Definition
|
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Term
| what kind of bacteria are haemophilus influenzae? where do they like to colonize? |
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Definition
| gram negative coccobacillus that likes to colonize the pharynx |
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Term
| what forms does haemophilus influenzae come in? |
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Definition
| encapsulated and non-encapsulated. the encapsulated form of haemophilus influenzae can survive in the blood b/c of decreased efficacy of opsonization/phagocytosis |
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Term
| what is the basis of the haemophilus influenzae vaccine? |
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Definition
| creation of antibodies against the capsule |
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Term
| what are some virulence factors of haemophilus influenzae? |
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Definition
| haemophilus influenzae has pili on its surface, allowing it to adhere to the respiratory epithelium. haemophilus influenzae also has a factor which disorganizes the ciliary beating and degrades IgA |
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Term
| how does an infection of the lung by haemophilus influenzae present? what predisposing factors is it associated with? |
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Definition
| bronchopneumonia - and is associated with chronic lung disease, CF, and bronchiectasis |
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Term
| what is the major cause of life threatening infections in children? |
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Definition
| haemophilus influenzae (prior to vaccine in the US - but still applies internationally) |
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Term
| how can a haemophilus influenzae infection lead to airway obstruction? |
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Definition
| haemophilus influenzae can cause a descending laryngotracheobronchitis which can become an obstruction to the airway as the smaller bronchi are filled with PMNs and neutrophils |
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Term
| what other kinds of infections can haemophilus influenzae cause? |
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Definition
| epiglottitis (becomes big and beefy red - referred to as the thumb sign on lat neck x-ray DO NOT use tongue depressor), otitis media, pericarditis |
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Term
| what is the most common bacterial cause of *acute exacerbation of COPD*? |
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Definition
| haemophilus influenzae, followed by moraxella catarrhalis |
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Term
| who are more likely to become infected by moraxella catarrhalis? |
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Definition
| elderly pts and those with COPD are more likely to contract pneumonia due to moraxella catarrhalis while it more commonly causes otitis media in children |
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Term
| how is staph aureus pneumonia generally contracted? how does it present? |
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Definition
| staph aureus pneumonia is often nosocomial and presents as bronchopneumonia. it can form abscesses and empyemas. |
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Term
| who is likely to get a pneumonia due to staph aureus? |
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Definition
| staph pneumonia is an important cause of bacterial pneumonia secondary to viral pnemonia in children and healthy adults. it is also commonly nosocomial and associated with IVDAs |
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Term
| what kind of bacteria is klebsiella pneumoniae? |
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Definition
| gram negative - klebsiella pneumoniae is the most common cause of gram-negative pneumonia |
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Term
| what part of the pt population is associated with pneumonia due to klebsiella pneumoniae? |
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Definition
| malnourished people, alcoholics |
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Term
| how does the sputum of lungs infected with klebsiella pneumoniae appear? |
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Definition
| gelatinous/viscous (currant jelly) due to viscid capsular polysaccarides |
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Term
| what kind of pneumonia does klebsiella pneumoniae cause? how does it appear on a CXR? |
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Definition
| lobar pneumonia - associated with a *bulging lobe* seen on CXRs |
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Term
| why is there a greater mortality in pts w/pneumonia due to klebsiella pneumoniae? |
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Definition
| usually klebsiella pneumoniae infects pts who are already debilitated and malnourished |
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Term
| what kind of bacteria is legionella pneumonia? |
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Definition
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Term
| what are legionella pneumonia infections associated with? how is it contracted? |
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Definition
| pneumonia due to legionella pneumonia is usually contracted due to inhalation of aerosolized organisms or aspiration of contaminated drinking water. therefore, legionella pneumonia is associated with A/C and other artificial aquatic environments |
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Term
| what part of the pt population is commonly affected by legionella pneumoniae? |
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Definition
| pts with heart, renal, immunologic or hematologic disease are more commonly affected by legionella pneumonia - essentially people w/other disease processes including transplant pts |
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Term
| is legionella pneumonia treatable? |
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Definition
|
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Term
| how are legionella pneumonia diagnosed? |
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Definition
| cxs are the gold standard, though antigens can be detected in the urine |
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Term
| what is the mortality rate for pts whose lungs are infected with pseudomonas aerugninosa? |
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Definition
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Term
| what part of the pt population is often affected by pseudomonas aerugninosa pneumonia? how is it often contracted? |
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Definition
| pseudomonas aerugninosa pneumonia often affects *burn pts*, those w/CF, on chemo, those w/neutropenia & other immune-debilitated pts, and transmission is often nosocomial |
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Term
| what does nonbacteremic pseudomonas aerugninosa pneumonia typically result in? |
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Definition
| *diffuse bronchopneumonia* |
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Term
| what does bacteremic pseudomonas aerugninosa pneumonia typically result in? |
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Definition
| necrosis and invasion of the blood vessels, leading to spread outside the respiratory tree and to other organs/portions of the body = high mortality |
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Term
| who does aspiration bronchopneumonia generally affect? |
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Definition
| aspiration bronchopneumonia generally affects debilitated pts with an abnormal gag reflex |
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Term
| why is aspiration bronchopneumonia particularly bad? what kind of damage is specifically associated with it? |
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Definition
| aspiration bronchopneumonia is particularly bad b/c it involves a chemical (HCl) and infectious process (oral flora) - often resulting in necrosis along with abscess formation |
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Term
| how can aspiration bronchopneumonia occur to alcoholics? |
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Definition
| if they become intoxicated, vomit, and inhale their own vomit |
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Term
| what causes severe acute respiratory syndrome (SARS)? what characterizes the disease? |
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Definition
| SARs is due to a *coronavirus* and is characterized by an incubation period of 2-10 days followed by malaise, dry cough, fever, chills and myalgias. 1/3 of pts recover, the rest progress to severe resp disease. 10% of pts will die |
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Term
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Definition
| IDing the antibodies or the virus itself |
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Term
| what kind of histologic changes might SARS incur? |
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Definition
| multinucleated giant cells |
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Term
| what kind of damage does SARS specifically cause? |
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Definition
| DAD: diffuse alveolar damage, consisting of hyalinization of epithelial/endothelial membranes that impair respiration |
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Term
| what characterizes a "typical pneumonia"? |
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Definition
| usually: bacterial pneumonias, fever, productive cough, green sputum (a more typical clinical response) |
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Term
| what characterizes an "atypical pneumonia"? |
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Definition
| not as much of a cough/moderate level of sputum, *no consolidation* (no firmness/edema), lack of alveolar exudate, moderate WBC levels, and "do not feel as bad" |
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Term
| what are the common community-acquired causes of atypical pneumonia? |
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Definition
| mycoplasma (most common), influenza type A & B, RSV, adenoviruses and rhinoviruses |
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Term
| what is the lung morphology produced by all community-acquired atypical pneumonia? |
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Definition
| the lung involvement may be patchy, involve whole lobes bilaterally/unilaterally, the lung is red-blue, congested and subcrepitant, and the pleura is smooth (abscesses/empyemas/pleuritis/pleural effusions are infrequent) |
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Term
| what is the histologic pattern of community acquired atypical pneumonia? |
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Definition
| this first depends on the severity of the disease, but the histologic pattern of community acquired atypical pneumonia consists of *interstitial inflammation* w/involvement of the alveolar walls. the alveolar septae are widened and edematous w/an infiltrate of lymphocytes, plasma cells and histiocytes. there may be some degree of alveolar damage w/hyaline membranes similar to those seen in DAD. there may also be a superimposed bacterial infection which alters the morphology. |
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Term
| what is the clinical course for community-acquired pneumonia? |
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Definition
| the clinical course is varied, a cough may be absent, but the mortality rate is generally under 1% w/the ordinary sporatic type. severe interstitial pneumonia however can be associated with an epidemic such as influenza. |
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Term
| what does the influenza virus consist of? |
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Definition
| 8 helices of single stranded RNA, each encoding a single gene and each bound by a nucleoprotein that determines the type of influenza A, B, or C. a lipid bilayer or envelope then contains the RNA and is composed of hemaglutinin and neuraminidase (which determines the subtype, H1-3, N1-2 etc) |
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Term
| how are influenza infections typically cleared by the body? |
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Definition
| cytotoxic T cells - lymphocytes are the main immune response to viral infections. intracellular anti-influenza proteins are also activated in macrophages |
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Term
| can a single subset of influenza A predominate the world at a given time? |
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Definition
| yes, and influenza A can infect humans/pigs/horses/birds |
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Term
| what is antigenic drift? when does it usually occur? |
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Definition
| a series of mutations in influenza hemagglutinin and neuroaminidase that allow the virus to *escape host antibodies. this usually happens in *epidemics |
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Term
| what is antigenic shift? when does it usually occur? |
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Definition
| hemagglutinin and neuroaminidase are *replaced through recombination of RNA segments with animal viruses -> making all individuals with previous immunity re-susceptible. this usually happens in *pandemics |
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Term
| how do pts with influenza infections present? |
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Definition
| mucosal hyperemia and swelling w/a lymphocytic and plasmacytic infiltration of the submucosa and increase in mucus secretions. bronchociliary function is impaired and plugging of the airways by cell debris, fibrin, and inflammatory exudate may cause organization and fibrosis. pts w/influenza are more susceptible to secondary bacterial infections. |
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Term
| who does mycoplasma pneumonia affect? |
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Definition
| young adults and children (these people aggregated in large groups are more at risk) |
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Term
| is mycoplasma pneumonia atypical? what are the clinical symptoms? |
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Definition
| yes - there is fever, malaise and minimum sputum production. the alveolar spaces are typically free of exudate and *cold agglutinins* are elevated. this used to be called "walking pneumonia" b/c pts with this are not as sick |
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|
Term
|
Definition
| localized accumulations of pus, lymphocytes and necrosis - not seen in every type of pneumonia/pt. |
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|
Term
| what is a common cause of lung abscesses? |
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Definition
| aspiration, where you can get a chemical injury (stomach HCl) producing necrosis and introduction of a variety of different flora |
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Term
| are some bacterial pneumonias more prone to abscess formation? |
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Definition
| yes, staph aureus in particular |
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Term
| can septic emboli lead to lung abscesses? |
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Definition
| yes, infections may embolize and localize in the lungs |
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Term
| can CA cause lung abscesses? |
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Definition
| yes, neoplasms can impair blood supply which results in some necrosis, as well as impair ventilation to some parts of the lung |
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Term
| what are general characteristics of lung abscesses? |
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Definition
| they may be small/large/single/multiple, full of suppurative debris and can destroy the lung parenchyma w/a central area of cavitation (TB) |
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Term
| can actinomycosis be associated with abscess formation? |
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Definition
| yes, actinomycosis form sulfur granules which appear as yellow colonies. they can also form sinus tracts between portions of the lung or into the pleura/bronchial tree. actinomycosis-related abscesses tend to be associated with a vigorous fibroblastic reaction - if the person survives - they often heal with a significant amount of fibroblasts |
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Term
| what characterizes chronic pneumonia? |
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Definition
| lung infections by organisms (bacteria/fungi) that are not easily dissipated/difficult to treat. these infections may remain localized if the pt is immunocompetent, but if immunocompromised, the infections tend to be much more widespread and damaging. chronic pneumonia is often characterized by granulomatous inflammation. common types include: TB, histoplasmosis, blastomycosis, and coccidiomycosis |
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Term
|
Definition
| a self-limited primary infection by histoplasma capsulatum due to inhalation of dust particles from bat/bird dropppings |
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Term
| how does histoplasmosis present? does it affect other organs besides the lungs? |
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Definition
| chronic progressive secondary lung disease with fever, cough, and night sweats. localized extrapulmonary sites include the liver, adrenals and meninges |
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Term
| what are the major targets of infection with histoplasmosis? how does the body protect against this? |
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Definition
| macrophages, where histoplasma capsulatum multiply and eventually lyse. T cells secrete IFN which activates the macrophages to kill the intracellular yeasts and the macrophages themselves secrete TNF which recruits other macrophages to kill the histoplasma capsulatum. thus, immunocompetent pts can usually clear this infection over time |
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Term
| what kinds of lesions can be formed in histoplasmosis? |
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Definition
| histoplasma capsulatum produces granulomas w/coagulative necrosis that often coalesce to form larger areas of consolidation. these lesions can undergo fibrosis and calcification and appear as chronic lesions: gray white granulomas in the apices of the lungs w/thickening of the pleura and in the hilar nodes. immunocompromised pts may form fulminant disseminated histoplasmosis, which is an absence of granulomas and a presence of focal yeast deposits throughout tissues and organs |
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Term
|
Definition
| pulmonary blastomycosis is an abrupt illness w/couch, weight loss, fever, and chills (resembles TB) due to a soil-inhabiting fungus native to the central/SE US - blastomyces (yeast with a double contoured cell wall and multiple nuclei) |
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Term
| what parts of the lung are usually affected by pulmonary blastomycosis? how does the disease progress? |
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Definition
| blastomycosis usually affects the upper lobes and may resolve spontaneously or persist to a more chronic type of lesion, such as suppurative granulomas. |
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Term
| what is coccidiomycosis? what its virulence factor? |
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Definition
| a fungal infection similar to histoplasmosis seen in the SW/W US, featuring multiple granulomas. when ingested by macrophages coccidiomyces blocks the fusion of the phagosome w/the lysosome - and therefore resists intracellular killing |
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Term
| can CMV affect the lungs? who is this most commonly seen in |
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Definition
| yes, and it is associated with herpes, features *enlarged cell nuclei and intranuclear inclusion bodies. this is almost always seen in immunocompromised pts - who it is worse in |
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|
Term
| what is pneumocystis pneumonia? |
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Definition
| an opportunistic agent related to fungi seen primarily infecting immunocompromised pts (often an early presentation of AIDS pts). |
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Term
| how does pneumocystis pneumonia appear? |
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Definition
| the alveoli are filled with organisms, forming cup-like cysts best seen on silver stain (on regular H+E they appear as pinkish exudates w/in the alveoli) |
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