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90 Cards in this Set
- Front
- Back
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what are most respiratory infections |
upper respiratory infections caused by viruses
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pneumonia
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defined broadly as any infection of the lung parenchyma
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defects in innate and humoral immunities lead to an increase of what lung infections
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pyogenic bacteria
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cell-mediated immune defects lead to increase of what infections
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intracellular microbes like mycobacteria and herpes-viruses and microorganisms with low virulence (pneumocystis jiroveci)
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most common cause of death in viral influenza
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superimposed bacterial pneumonia
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how are pneumonias classified
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by specific etiologic agent or clinical setting in which infection occurs
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pneumonia syndromes (classification by clinical setting)
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1) community aquired acute 2) community aquired atypical 3) hospital-aquired 4) aspiration 5) chronic 6) necrotizing and lung abscess 7) immunocompromised
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community aquired acute pneumonias
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bacterial or viral - bacterial often follows viral
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what does bacterial infection of the lung parenchyma cause
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alveoli to be filled with inflammatory exudate and causing consolidation of pulmonary tissue
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streptococcus pneumonia (pneumococcus)
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most common cause of community aquired acute pneumonia; gram-pos lancet-shaped diplococci
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common reason for false positive with streptococcus pneumonia
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endogenous flora in 20% of adults
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Haemophilus influenzae specs
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pleomorphic, gram-neg organism
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Haemophilus influenzae causes what
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life-threatening acute lower respiratory tract infections and meningitis in young children; common community-aquired acute pneumonia
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where does H. influenzae generally colonize
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pharynx in encapsulated (5%) and unencapsulated (95%) forms
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encapsulated can dominate unencapsulated H. influenzae how
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secreting an antibiotic called haemocin that kills the unencapsulated forms
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serotypes of encapsulated H. influenzae
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6 serotypes - type b used to be the most frequent cause of severe invasive disease
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type b serotype of encapsulated H. influenzae
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polyribosephosphate capsule
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what has caused a decline in type b encapsulated H. influenzae
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routine use of conjugate vaccines
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nonencapsulated infections of H. influenzae (aka nontypeable forms)
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spread along surfce of upper respiratory tract and produce otitis media, sinusitis, and bronchopneumonia
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what mediates adherence of H. influenzae to repiratory epithelium
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pili on the surface and secreting a factor that disorganized ciliary beating along with a protease that degrades IgA
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why is H. influenzae pneumonia a pediatric emergency
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descedning laryngotracheobronchitis results in airway obstruction as smaller bronchi and plugged by dense, fibrin-rich exudate of polymorphonuclear cells
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most common bacterial cause of acute exacerbation of COPD
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H. influenzae
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Moraxella catarrhalis causes
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second monst common bacterial cause of acute exacerbation of COPD
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3 most common causes of otitis media in children
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S. pneumoniae, H. influenzae, and Moraxella catarrhalis
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important cause of secondary bacterial pneumonia in children and healthy adults following viral respiratory illness
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staphlococcus aureus
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complications with staph aureus
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lung abscess and empyema
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Klebsiella pneumonia
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most frequent gram-neg bacterial pneumonia
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who does Klebsiella pneumonia generally affect
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debilitated and malnourished ppl (especially alcoholics)
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characteristics of klebsiella pneumonia
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thick and gelatinous sputum - organism produces abundant viscid capsular polysaccaride
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pseudomonas aeruginosa occurs in what patient subset
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cystic fibrosis; neutropenic patients
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legionella pneumophila (legionnaires' disease) flourishes where
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artificial aquatic environments
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who is legionella pneumophilia pneumonia common in
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cardiac, renal, immunologic, or hematologic disease; organ transplant recipients
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two patterns of bacterial pneumonia
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lobular bronchopneumonia and lobar pneumonia
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4 stages of inflammatory response in lobar pneumonia
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congestion, red hepatization, gray hepatization, and resolution
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congestion stage
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lung is heavy, boggy, and red; vascular engorgement, intra-alveolar fluid with few neutrophils, numerous bacteria
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red hepatization stage
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massive confluent exudation with neutrophils, red cells, and fibrin filling alveolar spaces; red, firm, and airless with liver-like consistency
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gray hepatization stage
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progressive disintegration of red cells and persistence of fibrosuppurative exudate; grayish brown, dry surface
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resolution stage
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consolidation exudate within alveolar spaces undergoes progressive enzymatic digestion to produce granular, semifluid debris that is resorbed, ingested by macrophages, expectorated, or organized by fibroblasts growing into it
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bronchopneumonia locations
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may be patchy through one lobe, but usually multilobular and frequently bilateral and basal since secretions gravitate into lower lobes
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complication of pneumonia
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1) tissue distruction and necrosis (abscess formation) 2) spread of infection to pleural cavity (empyema) 3) bacteremic dissemination to heart valves, pericardium, brain, kidneys, spleen, joints
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major symptoms of community aquired acute pneumonia
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abrupt onset fever, shaking, chills, cough productive of mucopurulent sputum, some have hemoptysis
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Primary atypical pneumonia defined
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acute febrile respiratory disease characterized by patchy inflammatory changes in the lungs, largely confined to alveolar septa and pulmonary interstitum
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what does the term atypical refer to
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moderate amount of sputum, no physical findings of consolidation, moderate WBC elevation, lack of alveolar exudate
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most common cause of Primary atypical pneumonia
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mycoplasm pneumoniae; then viruses like influenza type A and B, many other viruses
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predominat characteristic of Primary atypical pneumonia
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interstitial nature of inflammatory response - virtually localized within walls of the alveoli; septa widened and edematous and usually have mononuclear inflammatory infiltrate
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what do many cases of Primary atypical pneumonia masquerade as
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severe upper respiratory tract infection or chest colds
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genome of influenza virus
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8 helices of single stranded RNA - each has single gene and nucleoprotein bound to
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envelope of influenza virus
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contains viral hemagglutinin and neuraminidase (determine subtype of virus)
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what accounts for clearance of primary influenza virus infection
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cytotoxic T cells and intracellular anti-influenza protein induced in macrophages by cytokines IFN-a and IFN-b
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major influenza causing pandemic and epidemic infections
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type A
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type B and C
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show no antigenic drift and infect mostly children
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what causes the severity of the H5N1 influenza (bird/avian flu)
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ability of virus to cause widespread infection in body and isn't limited to lungs; 60% mortality
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why isn't H5N1 limited to lungs
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hemagglutinin can be cleaved by ubiquitous proteases instead of proteases only found in certain organs
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viral upper respiratory infections morphology
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mucosal hyperemia and swelling; lymphomonocytic and plasmacytic infiltration of submucosa accompanied by overproduction of mucus secretions
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lymphoid hyperplasia in virus vs staph/strep infections
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not usually associated with suppuration or abscess formation like staph/strep
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human metapneumovirus (MPV)
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paramyxovirus; upper and lower respiratory tract infections
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What is MPV clinically indistinguishable from
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indistinguishable from human respiratory syncytial virus
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Severe acute respiratory syndrome (SARS) specs
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incubation 2-10 days; dry mouth, malaise, fever, chills, myalgias; 1/3 improve, rest severe respiratory disease with SOB, tachypnea, pleurisy
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cause of SARS
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coronavirus (cause 1/3 upper respiratory infections) - RNA virus
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hospital-aquired pneumonia causes
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gram neg rods (enterobacteriaceae and psudomonas) and S. aureus
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aspiration pneumonia specs
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aerobes more common than anaerobes; often necrotizing, pursues a fulminant clinical course, and is a frequent cause of death; lung abscess common complication
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Lung abscess defined
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local suppurative process wihtin lung characterized by necrosis of lung tissue
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most common pathogen in lung abscesses
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aerobic and anaerobic strep (S. aureus), and gram negative organisms
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anaerobic organisms normally found in the oral cavity
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bacteroides, fusobacterium, and peptococcus (exclusive isolates in 60% cases of abscess)
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post-pneumonic abscess formations are common with
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S. aureus, K. pneumoniae, and type 3 pneumococcus
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primary cryptogenic lung abscesses
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all other causes ruled out
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pulmonary abscesses due to aspiration morphology
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more often right; usually single
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pneumonia or bronchiectasis morphology of abscesses
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usually multiple; basal; and diffusely scattered
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cardinal histologic chage in all lung abscesses
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suppurative destruction of the lung parenchyma within the central area of cavitation
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what should be ruled out in an older individual with a lung abscess
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underlying carcinoma (10-15% of cases)
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chronic pneumonia general characteristics
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usually a localized lesion in immunocompetent patient with or without regional lymph node involvement; typically granulomatous and caused by bacteria (TB) or fungi
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what are granulomatous diseases of the lungs that may resemble TB
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histoplasmosis, blastomycosis, coccidioidomycosis; all fungi
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how do the fungi grow in lung tissue
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as yeast at body temp - thermally dimorphic; all are geographic
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Histoplasmosis infection
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inhalation of dust particles from contaminated soil; intracellular parasite of macrophages; opportunistic infection
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what controls histoplasmosis infection
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helper T cells - secrete IFN-g which activates macrophages
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morphology of histoplasmosis infection
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epitheliodid cell granulomas - caseation necrosis and coalesce to produce large areas of consolidation
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what occurs to lesions in histoplasmosis infections with spontaneous or drug control
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undergo fibrosis and concentric calcification (tree-bark appearance)
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what must be IDed in histoplasmosis infections to differentiate from TB and other fungal infections
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3-5 um thin-walled yeast forms (may persist in tissues for years)
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fulminant disseminated histoplasmosis infection
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focal accumulations of mononuclear phagocytes filled with fungal yeasts throughout tissues and organs of body (immunosuppresses individuals)
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blastomycosis specs
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soil-inhabiting; central/SE US; 3 clinical forms
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blastomycosis infection
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abrupt illness with productive cough, headache, etc; lobar consolidation, multilobular infiltrates, perihilar infiltrates, multiple nodules, miliary infiltrates; upper lobes
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blastomycosis infection morphology
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suppurative granulomas; continued recruitment of neutrolphils; round 5-15 um yeast with broad-based budding
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what can cutaneous blastomycosis infections be mistaken for
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squamous cell carcinoma due to marked epithelial hyperplasia
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coccidioidomycosis specs
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almost everyone who inhales dvlps delayed hypersensitivity to fungus; most asymptomatic
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cause of high infectivity of coccidioidomycosis
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infective arthroconidia - when ingested by alveolar macrophages, it blocks fusion of phagosome and lysosome (resist intracellular killing)
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histology of coccidioidomycosis
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thick-walled, non-budding spherules 20-60 um diameter; filled with small endospores
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bacterial lung infections in HIV patients
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more common, more severe, and more associated with bacteremia
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more common pneumonia agents in HIV patients with CD4+ counts >200
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bacterial and tubercular
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more common pneumonia agents in HIV patients with CD4+ counts <200
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pneumocystis
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more common pneumonia agents in HIV patients with CD4+ counts <50
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cytomegalovirus and mycobacterium avium
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