Pneumonias & Respiratory Infections Flashcards
Organisms responsible for typical bacterial pneumoniae
S.pneumoniae H.influenzae M.catarrhalis S.aureus K.pneumoniae P.aeruginosa C.burnetti
Organisms responsible for atypical bacterial pneumoniae
Mycoplasma pneumoniae Chlamydia pneumoniae Chlamydia psittaci Legionella pneumophilia Burkholderia cepacia
Viruses that can cause pneumonia
Orthomyxoviridae (influenzavirus)
Coronaviridae (SARS, MERS)
Bunyaviridae (hantavirus)
Fungi that can cause pneumonia
Aspergillus spp.
Histoplasma capsulatum
Coccidioides immitis
Blastomycoses dermatides
Morphology of S.pneumoniae
Gram-positive diplococci (lancet shaped)
Encapsulated
Alpha-hemolytic
Optochin sensitive, bile-soluble
Urinary antigen
Most common cause of community acquired pneumonia (CAP)
S.pneumoniae
[S.pneumo is also most common cause of meningitis, otitis media, and sinusitis]
Presentation of CAP caused by S.pneumoniae
Fever, chills, cough, dyspnea, weakness
RUST COLORED SPUTUM
Treatment for S.pneumoniae
Macrolides
Ceftriaxone
Describe S.pneumoniae vaccine given to kids vs. adults
Give kids <2 the protein conjugated vaccine [elicits IgG (T cell) response]
Give adults pure polysaccharide vaccine [elicits IgM (B cell) response]
Morphology of H.influenzae
Gram-negative coccobacilli
Encapsulated or no capsule
Media on which H.influenzae can be grown
Chocolate agar (H.influenzae requires factors V and X)
What patient populations are at increased risk of H.influenzae infection?
Sickle cell Asplenic Smokers COPD Immunocompromised
What type of vaccine is the H.influenzae (Hib) vaccine?
Polysaccharide vaccine — given to infants
Treatment for H.influenzae prophylaxis vs. infection
Rifampin = prophylaxis for kids w/ close contacts
Ceftriaxone
Morphology of M.catarrhalis
Gram-negative coccobacillus
Fastidious, aerobic
Patient populations at higher risk of infection with M.catarrhalis
Smokers
COPD
Asthmatics
Malignancies
Generally exacerbates predisposing conditions then forms pneumonia
Morphology of S.aureus
Gram positive cocci
Catalase positive
Coagulase positive
Beta-hemolytic
Protein A — binds IgG, inhibiting complement acitvation and phagocytosis
Mannitol fermenting; gold/yellow in culture
Presentation of pneumoniae caused by S.aureus
Patchy infiltrates on CXR, most commonly following a URI (especially influenza virus!)
SALMON COLORED SPUTUM
Treatment for pneumoniae caused by S.aureus
Vancomycin (MRSA)
Nafcillin (non-MRSA)
Morphology of K.pneumoniae
Gram-negative bacillus
Immotile; surrounding by polysaccharide capsule
Urease positive
Lactose fermenting
Anaerobic
Agar on which K.pneumoniae can be grown
Forms pink mucoid colonies on MacConkey agar
Pt populations at increased risk of K.pneumoniae
Alcoholics (aspiration PNA!)
Asplenic
Immunocompromised
[K.pneumoniae is often nosocomial and multi-drug resistant]
Presentation of pneumonia caused by K.pneumoniae
Presents with CURRANT JELLY SPUTUM
May see cavitary lesions similar to TB (or bulging fissure)
Can be lobar or necrotizing
Morphology of P.aeruginosa
Gram negative bacillus
Motile (swarming)
Catalase positive
Obligate aerobe
Forms biofilms
Produce characteristic blue-green pigment (pyocyanin and pyoverdin); grape-smelling
Thrives in aquatic environments
P.aeruginosa is a common cause of nosocomial infections, and a major cause of lung infection and respiratory failure in _______ and ______ patients
Cystic fibrosis
Bronchiectasis
Treatment options for P.aeruginosa infection
Piperacillin
Ticarcillin
Fluoroquinolones
Aminoglycosides + Beta-lactams
Morphology of Coxiella burnetti
Gram-negative
Obligate intracellular
Endospores
Animal reservoirs — risk in farmers, shepherds, cattle birthers, vets at risk
Describe infection caused by Coxiella burnetti
Q fever — abrupt high unremitting fever, myalgias, headache, dry cough, granulomatous hepatitis (no jaundice)
May have mild pneumonia, or rapidly progress to respiratory distress
Leukocytosis and thrombocytopenia
Can also cause endocarditis and/or maculopapular rash
Morphology of mycoplasma pneumoniae
No cell wall; cell membrane w/ cholesterol
Obligate intracellular
IgM cold agglutinins
Agar on which mycoplasma pnuemoniae can be grown
Eaton’s agar
Presentation of infection with mycoplasma pneumoniae
Presents with dry cough; CXR shows reticulonodular or “patchy” infiltrate, often appearing more severe than pt symptoms
Generally self-limiting, usually follows URI
Also may see bullous myringitis
Common in military recruits living in close quarters; commonly in adults <30 y/o
Treatment for infection with M.pneumoniae
Macrolides
Morphology of Chlamydia pneumoniae
Gram negative
Obligate intracellular; no cell wall
Elementary bodies = extracellular infectious form (vs. reticulate bodies, the intracellular replicating form seen as intracytoplasmic inclusions on microscopy — Giemsa stain)
Preferred method for detection of Chlamydia bacteria
Nucleic acid amplification test (NAAT)
Presentation of infection with Chlamydia pneumoniae
Often follows URI, similar presentation to mycoplasma, but presents with HOARSENESS
Treatment for infection with chlamydia pneumoniae
Macrolides (particularly azithromycin)
Tetracyclines (particularly doxycycline)
Morphology of Legionella pneumophilia
Gram negative bacillus
Oxidase positive
Silver stain required for visualization
Agar on which Legionella can be grown
Buffered Charcoal Yeast Extract (BCYE) agar with cysteine and iron
Describe infection caused by Legionella including CXR and presenting sx/lab findings
Pontiac fever — acute, self-limiting respiratory disease with mild flu-like symptoms
CXR often shows patchy unilobar infiltrates that progress to consolidation
May present with HYPONATREMIA, headache, confusion, diarrhea, high fever (>39)
diagnosed using urine Ag test
Major risk factor for Legionella infection
Smoking
Treatment for infection with Legionella pneumophilia
Macrolides
Fluoroquinolones
Morphology of Chlamydia psittaci, and its reservoir
Gram-negative
Obligate intracellular, no cell wall
Reservoir = birds — transmitted via bird droppings (can see in pet shop owners, vets, ducks, turkeys)
Presentation of Chlamydia psittaci infection
Abrupt headache, dry cough, myalgias, dyspnea
Can have EPISTAXIS and SPLENOMEGALY
CXR indistinguishable from many bacterial and viral pneumonias
Tx of Chlamydia psittaci
Macrolides (particularly azithromycin)
Tetracyclines (particularly doxycycline)
Morphology of Burkholderia cepacia
Gram-negative bacillus
Catalase positive
Non-lactose fermenter
Agar on which Burkholderia cepacia can be grown
BC agar (has crystal violet and bile salts - colonies are pearly gray)
Pt populations at increased risk of Burkholderia cepacia
Cystic fibrosis
Bronchiectasis
Found on hospital equipment and irrigation systems
Very hard to tx, multi-drug resistant
Morphology of orthomyxoviridae (influenzavirus)
Negative-sense ssRNA virus
Enveloped
Orthomyxoviridae includes influenzavirus A, B, and C. It replicates inside the _____ of host cells and has genomes comprised of ____________.
The ________ of influenza A regulates H+ concentration around the virus, producing the proper pH for viral uncoating
Nucleus; 8 RNA segments
M2 proton channel
Describe HA and NA associated with orthomyxoviridae
HA promotes viral entry — binds sialic acid residues on host cells
NA cleaves sialic acid residues —> release of virus from host cells
Antigenic drift vs. antigenic shift
Antigenic drift is d/t point mutations in the viral genome —> changes in HA and NA glycoproteins —> epidemics
Antigenic shift — when segments of genomes from different strains combine to form novel genome —> pandemics
Presentation of orthomyxoviridae infection
Fever, chills, myalgias, nasal congestion, coryza, nonproductive cough, fever (>38), LAD, diffuse pneumonitis, hypoxemia, leukopenia
After a viral infection with influenzavirus, there is increased susceptibility to a superinfection, particularly with _____ or _____
S.aureus
S.pneumoniae
Types of flu vaccine
Killed injectable
Live intranasal
[associated with small risk of GBS — ascending paralysis]
The rapid flu test is suboptimal, and diagnosis by _____ is preferred
PCR
Treatment options for influenzavirus infection
Amantadine/rimantadine inhibit M2 proton channel of influenza A virus, impeding viral uncoating
Oseltamivir/zanamivir can inhibit NA, preventing release from host cells
______ in contraindicated in children with a viral infection
Aspirin [risk of Reye’s syndrome — encephalopathy, fatty liver, hepatic failure]
Morphology of coronaviridae
Positive-sense ssRNA virus
Enveloped - helical capsule
What is MERS?
Middle Eastern Respiratory Syndrome — caused by infection with coronaviridae
Fever, cough, dyspnea, diarrhea, abd pain, SEVERE ARDS presentation
Fecal-oral transmission
Hx of travel to middle east, especially Saudi Arabia
What is SARS?
Severe Acute Respiratory Syndrome — caused by infection with coronaviridae
Initial flu-like symptoms — cough, dyspnea, severe hypoxia; can progress rapidly to ARDS
Hx of travel to China, Hong Kong, Taiwan
Morphology and transmission of Hantavirus (bunyaviridae)
Negative-sense RNA virus
Obtain envelope from golgi body membrane of host cells
Genomes comprised of 3 circular RNA segments
Zoonotic — transmitted via feces, urine, and saliva of rodents
Presentation of infection with Hantavirus
Prodromal phase mimics many flu-like syndromes; rapidly progresses to cardiopulmonary syndrome with respiratory distress
Thrombocytopenia, leukocytosis, elevated LDH, bilateral pulmonary infiltrates
May cause pulmonary edema d/t increased capillary permeability
May cause hypotension leading to prerenal azotemia or ARF
May cause hemorrhagic fever
Morphology and transmission of aspergillus spp
Catalase positive
Septate hyphae that form 45-degree angle branches
Transmitted via spore inhalation
Signs/symptoms of aspergillus colonization in the lung
May cause fever, hemoptysis, and cough
Aspergillomas (“fungus balls”) typically develop in old pulmonary cavities (from TB, sarcoid, emphysema, etc.)
What is ABPA?
Allergic Bronchopulmonary Aspergillosis
Type I HSR
Presents with migratory pulmonary infiltrates, wheezing, and increased serum IgE
Most commonly CF and asthma pts
Invasive pulmonary aspergillosis typically occurs in _____ and _____ patients; it can spread hematogenously to kidneys, endocardium, brain, skin, and paranasal sinuses, causing infection and infarction
Immunosuppressed; neutropenic
Treatment of aspergillus spp infection
Voriconazole
Amphotericin B
Morphology of Histoplasma capsulatum
Microconidia
Dimorphic fungus (yeast in body, mold in natural environment)
Narrow-based budding
Transmission of Histoplasma capsulatum; where is it endemic?
Bat and bird droppings (caves, chicken coops, etc.) - transmitted via inhalation of mold spores
Endemic to midwestern and east central US, near Ohio and Mississippi River valleys
Detection of Histoplasma capsulatum
Macrophages phagocytize the yeast form in the lungs — these small oval yeast forms can be seen within macrophages on microscopy
Can also be detected in body fluids such as serum or urine
Clinical manifestations of Histoplasma capsulatum infection
Presents as mild cough, fatigue, weight loss, upper lung lobe cavitations (coin lesion); clinically resembles secondary TB
Can cause variety of calcific deposits in the lungs (i.e., calcified mediastinal/hilar LNs)
Associated with ERYTHEMA NODOSUM
May also see HSM — seen with disseminated infection (primarily in immunocompromised)
Treatment of Histoplasma capsulatum
Azoles
Amphotericin B
Morphology, transmission, and endemic regions of coccidioides immitis
Dimorphic fungus
Transmitted via inhalation of mold spores found in soil
Endemic to southwest US (California, New Mexico, Arizona) and Northern Mexico
Coccidioides immitis can be seen in tissue samples as large, yeast-like spherules containing ______
Endospores
Clinical manifestations of coccidioides immitis infection
Causes San Joaquin Valley fever and community acquired PNA
Chest pain, cough, fever, arthralgia
CXR may be unremarkable, or show unilateral infiltrates, ipsilateral hilar LAD, or pulmonary nodule formation
Associated with ERYTHEMA NODOSUM
Disseminated infection in immunocompromised — skin, bones, meningitis
Treatment of coccidioides immitis infection
Azoles (particularly itraconazole and fluconazole)
Amphotericin B
Morphology, transmission, and endemic regions of Blastomycoses dermatides
Dimorphic fungus
Broad-based budding
Transmitted via inhalation of mold spores
Endemic to eastern and central US near Ohio and Mississippi River Valleys and Great Lakes region
Clinical manifestations of blastomycoses dermatides
CXR findings vary, most commonly patchy opacities or densities
Can lead to pulmonary granuloma formation
Disseminated infection in immunocompromised — skin, bone, GU involvement
Detection of blastomycoses dermatidis
Detected in body fluids such as urine
Tx of blastomycoses dermatides
Azoles (particularly itraconazole and fluconazole)
Amphotericin B
Primary location of infection, CXR/CT pattern, US pattern, and organisms associated most often with Lobar PNA
Location: alveoli
CXR/CT: Dense consolidation; air bronchograms
US: Consolidation (often extensive); dynamic air bronchograms
Organisms: S.pneumoniae, K.pneumoniae, Legionella
Primary location of infection, CXR/CT pattern, US pattern, and organisms associated most often with bronchopneumonia
Location: bronchi
CXR/CT: Patchy opacities
US: patchy B-lines, may have some consolidation
Organisms: WIDE variety of bacteria — mycoplasma, chlamydia, staph, pseudomonas
Primary location of infection, CXR/CT pattern, US pattern, and organisms associated most often with interstitial PNA
Location: interstitium
CXR/CT: diffuse hazy opacities; septal thickening
US: patchy B-lines; may have some consolidation
Organisms: viruses, PJP, mycoplasma
Which pneumonia-causing organism has “fried-egg” appearance on microscopy?
Mycoplasma pneumoniae
What 2 bacterial species are grown on chocolate agar?
Haemophilus influenzae
Neisseria meningitidis
Empiric abx regimen for community acquired pneumonia
- Ambulatory — macrolide (if pt can’t tolerate, go with doxycycline)
- Possible drug-resistance — Fluoroquinolone or Macrolide + Beta-lactam
- Hospitalized pts — Fluoroquinolone
- ICU — fluoroquinolone + antipneumococcal beta-lactam (3rd gen cephalosporin or ampicillin sulbactam); add piperacillin-tazobactam, cefepime, or a “penem” for pseudomonal coverage
What lab can be ordered to aid in differentiating between viral and bacterial PNA?
Procalcitonin
[calcitonin precursor that becomes elevated in proinflammatory stimuli, especially those bacterial in origin]
What criteria are used to determine whether pt with PNA needs to be admitted?
CURB-65 Severity Score: Confusion = 1 pt BUN >20 = 1 pt RR >30 = 1 pt BP <90syst or <60diast = 1 pt Age >65 = 1 pt
0-1 pts = low risk; outpatient tx
2 pts = short inpatient hospitalization or closely supervised outpatient tx
3-5 = severe; hospitalization required. Consider ICU admission
What are the lactose fermenting bacteria?
Fast fermenters: Klebsiella, E.coli, Enterobacter
Slow fermenters: Citrobacter, Serratia
Non-enveloped, icosahedral dsDNA virus that causes the common cold, viral keratoconjunctivitis, pharyngitis; dx by viral culture, direct assay, or enzyme immunoassay
Adenovirus
What bacteria can be detected by urinary antigens?
S.pneumoniae
Legionella
Bacteria to consider in neutropenic and CF pts
Pseudomonas
Bacteria to consider in asplenic pts
Klebsiella
S.pneumoniae
H.influenzae
Neisseria spp
[susceptible to encapsulated organisms]
Bacteria to consider in smokers, COPD
Moraxella catarrhalis
Haemophilus influenzae
Bacteria to consider in alcoholics
Klebsiella
Bacteria to consider in bird handlers
C.psittaci
Criteria for hospital acquired PNA (HAP)
Infection acquired during hospital stay (>48 hrs)
Criteria for healthcare associated PNA (HCAP)
Hospitalized for at least 2 days within the last 90 days
OR
In the last 30 days: nursing home, infusions, dialysis pts, wound care
OR
Family member with multidrug resistant organism
Criteria for ventilator associated PNA (VAP)
ET intubation with 2 of the following: Fever, Leukocytosis, Purulent sputum
New or progressive opacity on CXR
