Chapter 15: Pulmonary Infections Flashcards
What is the most common cause of death in viral influenza epidemics?
Superimposed bacterial pneumonia
What are 2 acute phase markers made in the liver that are specific for bacterial infection and can be useful in pneumonia diagnosis?
- CRP
- Procalcitonin
Which serotype of the encapsulated H. influenzae is most virulent?
Type B
What will the sputum culture of a patient with community-acquired bacterial pneumonia caused by Streptococcus pneumoniae show morphologically?
Lancet-shaped gram (+) diplococci in pairs and chains
Which patient population is at a high risk for development of invasive infection by H. influenzae?
Neonates and children w/ comorbidities
What is the 1st and 2nd most common bacterial cause of acute exacerbation of COPD?
- Most common = H. influenzae
- 2nd = M. catarrhalis
Pneumonia caused by what bacteria is a pediatric emergency due risk of acute epiglottitis w/ high mortality rate?
H. influenzae
What is the pulmonary consolidation associated w/ H. influenzae typically like?
Lobular and Patchy
Which patient population is especially susceptible to bacterial pneumonia by Moraxella Catarrhalis?
Elderly
S. aureus pneumonia is associated with a high incidence of which 2 complications?
- Lung abscess
- Empyema (aka pus in the pleural space)
What is the most frequent cause of gram-negative bacterial pneumonia and who does it most commonly afflict?
- Klebsiella pneumoniae
- Debilitated and malnourished people, particularly chronic alcoholics
What type of sputum is characteristic of Klebsiella pneumoniae?
Thick, mucoid (blood-tinged) –> “currant jelly”
Pseudomonas aeruginosa is a common cause of pneumonia in whom and in what setting?
- Hospital acquired
- Cystic Fibrosis and Immunocompromised
Which bacteria cause of pneumonia flourished in warm freshwater (i.e., AC units, misters, hot tubs); what does it live inside?
- Legionella pneumophila
- Lives in amoebas
What are the 2 common modes of transmission for Legionella pneumophilia?
- Inhalation of aerosolized organisms
- Aspiration of contaminated drinking water
What is the gram stain and morphology of Legionella pneumophila?
Gram NEGATIVE bacillus
Pt’s with what predisposing conditions are most at risk for Legionella pneumonia?
- Pt’s w/ cardiac, renal, immunologic, or hematologic diseases
- Organ transplant recipients****
- Elderly smokers
How is rapid diagnosis of Legionella pneumophila done and what is the gold standard?
- Legionella Ags in the urine
- (+) fluorescent Ab test on sputum samples
- CULTURE = gold standard
Which bacterial cause of pneumonia is associated with hypokalemia, elevated CPK, and lobar infiltrates?
Legionella pneumophila
What is the gram stain, shape, and O2 dependency of Pseudomonas aeruginosa?
AEROBIC Gram NEGATIVE; bacillus
Mycoplasma pneumoniae infections are common in which age groups and occur most often how?
- Children and young adults
- Sporadically or as local epidemics (i.e., schools, military camps, prisons)
Patchy consolidation of the lung is the dominant characteristic of what type of bacterial pneumonia?
Bronchopneumonia
Air-fluid level within cystic space seen on CXR associated with pneumonia suggests what?
Lung abscess
What are the 4 stages of the inflammatory response which have been classically described for lobar pneumonia?
1) Congestion: vascular engorgement; intra-alveolar fluid
2) Red hepatization: massive exudation of alveolar spaces w/ lots of neutrophils; red, firm, airless lobe; liver-like consistency
3) Gray hepatization: disintegration of red cells w/ fibrinosuppurative exudate
4) Resolution: fibrosis and macrophage clean-up
Congested septal capillaries due to massive confluent exudation w/ numerous intra-alveolar neutrophils is characteristic of what stage of lobar pneumonia?
Red Hepatization
Which inflammatory stage of lobar pneumonia is characterized by progressive disintegration of red cells and the persistence of a fibrinosuppurative exudate?
Grey Hepatization
Exudates within alveolar spaces converted into fibromyxoid masses rich in macrophages is characteristic of which inflammatory stage of lobar pneumonia?
Resolution/Organization
Which pattern of bacterial pneumonia is often multilobular and frequently bilateral and basal?
Bronchopneumonia
Which cause of bacterial pneumonia is classically seen in military recruits or college student i.e., those living in close quarters?
Mycoplasma pneumonia
Histologically, the rxn associated with bronchopneumonia shows areas of acute suppurative inflammation rich in what type of immune cell?
Neutrophilic exudate filling bronchi, bronchioles, and adjacent alveolar spaces
Tissue destruction and abscess formation as a complication of pneumonia are most common associated w/ what 3 organisms?
- Type 3 pneumococci
- Klebsiella
- S. aureus
Bacteremic dissemination as a complication of pneumonia can spread where and cause what?
- Heart valves, pericardium, brain, kidneys, spleen, or joints
- Metastatic abscesses, endocarditis, meningitis, or suppurative arthritis
What are the major sx’s of acute bacterial pneumonia?
- Abrupt onset of high fever + shaking chills + cough
- Mucopurulent sputum and occasionally hemoptysis
What are the 2 most important components in term of virulence for Influenza virus allowing it to cause infections; function of each?
- Hemagglutinin: allows for attachment to cells; via sialic acid residues
- Neuraminidase: allows release of replicated virus from cells; cleaves sialic acid residues
What is antigenic drift in regards to Influenza virus and what changes occur; leads to what type of outbreak?
- Spontaneous mutation that alter antigenic epitopes on the vial Hemagglutinin and Neuraminidase proteins
- Result in new viral strains, leading to epidemics
What is antigenic shift in regards to Influenza virus and what changes occur; leads to what type of outbreak?
- Both hemagglutinin and neuraminidase genes are replaced through recombination w/ animal influenza viruses
- Leads to pandemics
If influenza virus gains entry into pneumocytes what are the cytopathic changes that it can elicit which contribute to its pathogenesis?
- Inhibits Na+ channels –> electrolyte + H2O shifts = fluid accumulation in alveolar lumen
- Inhibits host cells mRNA translation and activates caspases –> cell death via apoptosis
What complications may arise with viral pneumonia as a result of activation of the nearby pulmonary endothelium causing lung injury?
- ARDS
- Fatal pulmonary disease from superimposed bacterial infection
Which bacteria is most commonly found as cause of superimposed bacterial infection on a viral pneumonia?
Staphylococcus aureus
Which family of viruses does Human Metapneumovirus (MPV) belong to?
Paramyxovirus
What is the only antiviral tx that is currently available for human MPV infections and is most commonly used for immunocompromised pt’s w/ severe disease?
Ribavirin
Which family of viruses does SARS belong to?
Coronavirus
Why is SARS a distinct coronavirus in terms of infection?
- Many upper respiratory infections are caused by coronavirus
- SARS differs in that it can infect the lower respiratory tract and spread throughout the body
Respiratory syncytial virus (RSV) belongs to what family of viruses?
Paramyxovirus
How does respiratory syncytial virus (RSV) spread from the nasopharynx to lower respiratory tract; what is the effect of viral replication on this process?
- Attaches to and infects host epithelial cells in nasopharynx
- Cells are sloughed and aspirated, carrying RSV to lower respiratory tract cells
- Viral replication leads to abnormal sloughing of epithelial cells, inflammatory cell infiltration, ↑ mucus secretion and impaired ciliary action
Which virus is associated w/ sx’s of rhinorrhea, cough, wheezing, dyspnea, tachypnea, and cyanosis in an infant?
RSV
What are the 3 major bacterial causes of pneumonia in neonates?
- Group B strep
- Gram negative bacilli
- Listeria
What are 5 major viral causes of pneumonia in children >1 month?
- RSV**
- Parainfluenza virus, Influenza A and B, Adenovirus, Rhinovirus
What are 4 major bacterial causes of pneumonia in children >1 month?
- S. pneumoniae
- M. catarrhalis
- H. influenzae
- S. aureus
Viral-induced tonsillitis causing hyperplasia of the lymphoid tissue within what is common in children?
Waldeyer ring
What are the 3 major morphological changes seen in upper respiratory viral infections?
- Mucosal hyperemia
- Lymphomonocytic and plasmacytic infiltration of submucosa
- Overproduction of mucus secretions
How does the inflammatory rxn (location and immune cells) differ between bacterial vs. viral causes of pneumonia?
- Bacterial = INTRA-alveolar neutrophilic inflammation
- Viral = INTERSTITIAL lymphocytic inflammatory rxn; walls of alveoli
When viral pneumonia is complicated by ARDS what is seen lining the alveolar walls?
Pink hyaline membranes
Which 3 viruses may be associated with necrosis of bronchial and alveolar epithelium and acute inflammation?
- Herpes simplex
- Varicella
- Adenovirus
What is the onset, fever, and infiltration seen on CXR like for bacterial vs. viral causes of pneumonia?
- Bacterial has abrupt onset w/ high fever; and lobar/consolidated appearance
- Viral has gradual onset w/ absent or low-grade fever; and diffuse infiltrates on CXR
Bacterial causes of pneumonia are not typically associated w/ epidemics, except those caused by what 2 types?
- Legionella
- Pertussis
A red, flat to slightly bumpy (maculopapular) rash that starts on the forehead and spreads to the face, neck, torso, and finally the feet is associated with what virus?
Measles (paramyxovirus)
What is the gram stain and shape of Bordatella pertussis?
Gram negative bacillus
What are the 4 major virulence factors of Bordetella pertussis?
- Pertussis toxin: activates G proteins –> ↑cAMP
- Extracytoplasmic adenylate cyclase: “weakens” immune cells
- Filamentous hemagglutinin: binding to ciliated epithelial cells
- Tracheal cytotoxin: kills ciliated epithelial cells
While working the pediatric ED, you see a child with a sore throat and fever. There is a dark exudate on the child’s pharynx, which appears darker and thicker than that of strep throat; which bacteria is most likely responsible and what its gram stain/shape?
- -* Corynebacterium diptheriae
- Gram positive rods - very pleomorphic and club-shaped
If Corynebacterium diptheriae is suspected why must you NOT scrape the pseudomembranes formed on the pharynx; may lead to what?
- May bleed and systemic absorption of lethal EXOTOXIN will be enhanced
- Can cause: myocarditis and neural involvement (peripheral nerve palsies, Guillan Barre-like syndrome, and palatal paralysis/cranial neuropathies
What is the gram stain and shape of Listeria monocytogenes?
Gram POSITIVE rod
What are the 2 most common organisms isolated in association with Health Care-Associated Pneumonia?
- P. aeruginosa
- MRSA
How is health care-associated pneumonia different from hospital-acquired pneumonia?
- Health care = recent hospitalization, presenting from nursing/long-term care facility; attending hospital or hemodialysis clinic; recent IV abx, chemotherapy, or wound care
- Hospital-acquired = acquired while in the hospital
Patients on what are at particularly high-risk of hospital-acquired pneumonia?
Mechanical ventilation
What are the most common gram positive and gram negative organisms responsible for hospital-acquired pneumonia?
- Gram (+) cocci –> S. aureus and S. pneumonia
- Gram (-) rods –> Enterobacteriaceae (i.e., Klebsiella spp., Serratia, and E. coli) and Pseudomonas species
Which bacteria is a common cause of bacteria in pt’s with CF, burn victims, and those with neutropenia?
P. aerugionosa (Gram negative rod)
Which bacterial cause of pneumonia is especially common in organ transplant recipients?
Legionella pneumophila
What are the 4 anaerobic oral bacteria commonly recovered in the culture of pt with aspiration pneumonia?
- Bacteroides
- Prevotella
- Fusobacterium
- Peptostreptococcus
What are 3 atypical (aka not detectable on gram stain or with culture) bacteria associated with pneumonia?
- Mycoplasma pneumoniae
- Chlamydophila pneumoniae
- Coxiella burnetii
Aspiration pneumonia occurs most frequently in whom; what are the risk factors?
- Markedly debilitated pt’s + pt’s who aspirate gastric contents while unconcious or during repeated vomiting
- Acute/chronic alcoholism, COMA, stroke, anesthesia, sinusitis, gingivodental sepsis
What type of damage is seen with aspiration pneumonia and what is its typical course?
- Often necrotizing and pursues fulminant clinical course
- Frequent cause of death
In those who survive aspiration pneumonia what is a frequent complication that arises?
Lung abscesses
Microaspiration is commonly seen in pt’s with what condition?
What type of immune rxn/damage does it result in?
- Pts w/ GERD
- Results in small, poorly formed NON-caseating granulomas w/ multinucleated foreign body giant cell rxn
What is a common cause of postobstructive pneumonia which may lead to abscess formation?
Neoplasia causing obstruction
What is a cause of lung abscess which may originate in systemic venous circulation or the right side of the heart?
Septic embolism
When all the causes have been exluded and in which there is no discernible basis for lung abscess formation, what is this referred to as?
Primary cryptogenic lung abscesses
Lung abscesses due to aspiration are more common on which side of the lung and are most often (single/mutliple)?
Right side of lung; most often single
What is the cardinal histologic change in all lung abscesses?
Suppurative destruction of the lung parenchyma within the central area of cavitation
Clinical signs/sx’s of lung abscess?
- Cough + fever + copious amounts of foul-smelling purulent or bloody sputum
- Fever + chest pain + weight loss = common
- Clubbing of digits may appear within a few weeks
If a lung abscess is discovered in an elderly pt, what must be ruled out?
Underlying carcinoma
Complications which may arise from a lung abscess?
- Extension into pleural cavity
- Hemorrhage
- Brain abscesses or meningitis from septic emboli
- Rarely, secondary amyloidosis (AA)
What type of pneumonia is most often a localized lesion in the immunocompetent pt, with or without LN involvement; typically featuring a granulomatous inflammatory rxn?
Chronic pneumonia
Which chronic lung disease puts people at a particularly high risk for tuberculosis?
Silicosis
Which critical mediator released from TH1 cells both in LN’s and the lung enables macrophages to contain M. tuberculosis infection?
IFN-γ
Which immune cells orchestrate the formation of granulomas and caseous necrosis seen in M. tuberculosis infection?
TH1
Macrophages activated by IFN-γ in M. tuberculosis infection differentiate into what?
“Epithelioid histiocytes” that aggregate to form granulomas; some may aggregate to form giant cells
Pt’s with RA treated with what type of drugs are at an increased risk for tuberculosis reactivation?
TNF antagonist
Which pattern of tuberculosis arises in a nonimmune host vs. previously sensitized host?
- Non-immune = primary TB
- Previously sensitized = secondary TB
Secondary pulmonary tuberculosis classically involves which area of the lungs?
APEX of one or both lungs
What are the systemic and pulmonary signs/sx’s associated with secondary tuberculosis?
- Remittent/low-grade FEVER + WEIGHT LOSS + Night sweats
- Fever appears late each afternoon and then subsides
- Sputum that at first is mucoid and later purulent; variable degree of hemoptysis
Which laboratory diagnostic test allows for more rapid diagnosis of M. tuberculosis?
PCR amplification of M. tuberculosis DNA
What remains the gold standard for confirming diagnosis of M. tuberculosis?
Culture
What is a risk factor in HIV infected pt’s before starting HAART which increases risk for developing tuberculosis?
Low CD4 count
Primary tuberculosis almost always begins in which organ and what is seen morphologically as sensitization develops?
- Lungs –> bacilli implant in the distal airspaces of lower part of upper lobe or upper part of lower lobe
- Gray-white inflammation w/ consolidation, know as Ghon focus –> center of focus undergoes caseous necrosis
Ghon complex seen in primary TB is a combination of what?
Parenchymal lung lesion (Ghon focus)+LN involvement
Cell-mediated immunity typically controls the primary TB infection leading to what morphological change in the Ghon complex, which is often followed by what radiologically detectable change?
Ghon complex undergoes progressive fibrosis, followed by radiologically detectable calcification (Ranke complex)
Which subset of pt’s do NOT form the characteristic granulomas associated with primary TB and instead have macrophages loaded with many bacilli?
Immunocompromised
With progressive pulmonary tuberculosis, the pleural cavity is almost invariably involved, and what 3 complications may be seen here?
- Pleural effusions
- Tuberculous empyema
- Obliterative fibrous pleuritis
Systemic miliary tuberculosis is most prominent in which organs/structures?
- Liver
- Bone marrow (osteomyelitis)
- Spleen
- Adrenals (Addison diseas)
- Meninges (tuberculous meningitis)
- Kidneys (renal tuberculosis)
- Fallopian tubes (salpingitis) and Epididymis
When the vertebrae are affected by isolated tuberculosis this is known as what?
Parapsinal “cold” abscesses in these pt’s may track along tissue planes and present how clinically?
- Pott disease
- Present as abdominal or pelvic mass
What is the most frequent presentation of extra-pulmonary tuberculosis (aka what is most often affected)?
Lymphadenitis
How does lymphadenitis and the presentation differ in HIV-negative vs. HIV-positive pt’s with active tuberculosis?
- HIV-negative = lymphadenitis tends to be unifocal and localized
- HIV-positive = tends to be multifocal disease w/ systemic sx’s, and either pulmonary or other organ involvement
Granulomatous inflammation leading to ulceration of the overlying mucosa and eventually healing strictures associated with intestinal tuberculosis is most often seen in which segment of the intestine?
Ileum
Histoplasma capsulatum infection is acquired via inhalation of what?
Dust particles from soil contaminated with bird or bat droppings containing small spores (microconidia)
Histoplasma capsulatum is endemic where; where else is it seen?
- Endemic –> Ohio and Mississippi rivers and Caribbean
- Also found in Mexico, Central and S.A., parts of Europe, Africa, east Asia, and Australia
Histoplasma capsulatum typically causes what type of infection with what type of immune response; what is seen on CXR?
- Subclinical infection with granulomas, which usually undergo caseation necrosis and coalesce to produce large areas of consolidation
- Calcifications (“tree-bark appearance) or coin lesions on CXR
What is the morphology (aka shape) of the yeast forms seen with Histoplasma capsulatum?
Thin-walled yeast w/ “pumpkin seed” morphology
How is the diagnosis of Histoplasma capsulatum established; when are serological tests for Abs and Ags most useful?
- Via culture or identification of fungus in tissue lesions
- Ag detection most useful in the early stages
Granulomas in the lungs associated with Histoplasma capsulatum may liquefy and form cavities in pt’s with what underlying disease?
COPD
What are the 4 clinical presentations/morphological lesions which may be associated with Histoplasma capsulatum?
- Self-limited and often latent primary pulmoanry involvement; coin-lesions on CXR
- Chronic, progressive lung disease, localized to apices and causes cough, fever, and night sweats
- Extrapulmonary spread –> mediastinum, adrenals, liver, or meninges
- Widely disseminated disease in immunocompromised
How is the morphology of the disease caused by Histoplasma capsulatum different in immunosuppressed individuals?
- Causes fulminant disseminated histoplasmosis
- Granulomas do NOT form
- Instead there are focal accumulations of mononuclear phagocytes FILLED w/ fungal yeasts throughout the body
Blastomyces dermatitidis is a soil-inhabiting dimorphic fungi that is endemic where in the US and also seen in what other countries?
- Central (Ohio and Mississippi river valleys) and SE United States
- Also seen in Canada, Mexico, the Middle East, Africa, and India
How does pulmonary Blastomyces dermatitidis infection typically present clinically (signs/sx’s)?
- ABRUPT onset w/ productive cough + HA + chest pain
- Weight loss + fever + night sweats + chills
How do the lung lesions of Blastomyces dermatitidis appear morphologically in a normal host?
Which immune cells are seen in high numbers?
- Suppurative granulomas
- Macrophages have limited ability to ingest and kill this organism; persistence of this yeast leads to ↑↑ neutrophils
What is the characteristic morphology of Blastomyces dermatitidis that distinguishes it from other fungi?
- Round w/ BROAD-BASED BUDDING
- THICK, double-contoured cell-wall
Involvement of the skin and larynx by Blastomyces Dermatitidis caused what change to epithelial cells and may be mistaken for what?
- Marked epithelial hyperplasia
- May be mistaken for SCC
Where is Coccidioides immitis endemic and in the lungs what does the infection cause?
- Endemic in SW United States and Mexico
- Causes granulomatous response w/ eosinophils
What are the signs/sx’s of pulmonary and cutaneous infection with Coccidioides immitis?
- Fever + cough + pleuritic chest pain
- Erythema nodosum or erythema multiforme (the San Joaquin Valley fever complex)
Which pt population and ethnic groups are at the highest risk for the rare disseminated infection caused by Coccidioides immitis?
What type of lesions dominate in the disseminated disease?
- Filipino and African Americans
- Immunosuppressed
- Purulent lesions dominate
What is the characterisitc morphology of Coccidioides immitis that distinguishes it from other fungi?
- THICK-walled, NON-budding SPHERULES
- Often filled w/ small endospores
A pt with known lung disease presents with recurrent hemoptysis, a tissue sample from the lungs shows this; what is the diagnosis and how do you know?
- Aspergillosis
- Septate hyphae w/ acute-angle branching (40 degrees)
A tissue biopsy of a pt with granulomatous lung disease shows this; what oganism is this most consistent with?
Coccidioides immitis
