Bacterial Pneumonia

Question 1

Streptococcus pneumoniae
• Stucture
• Type of Pneumonia
• Transmission
• Replication Cycle
• Disease Presentation
• Pathogenic Mechanism
• Epidemiology
• Treatment
• Mortality
• Key findings/Diagnosis

Answer 1

Stucture
Gram positive, lancet shaped, ENCAPSULATED diplococcus, the produces ALPHA (green/partial) hemolysis

Type of Pneumonia
TYPICAL CAP - often post-viral

Transmission
Not mentioned

Replication Cycle
Not mentioned

Disease Presentation
Cough with rusty sputum. Fever, dyspnea, pleuritic pain. May also cause Meningitis, Otitis media, Sinusitis

Pathogenic Mechanism
¹Polysaccharide capsule (85 serotypes), interferes with phagocytosis​. ²IgA protease is important for preventing Ab binding in the Upper Respiratory Tract. ³Lipoteichoic acid activates complement and induces cytokine production.

Epidemiology
In any given area 5-50% of healthy people are colonized with this bug. Most healthy people are resistant (non-communicable). Predisposing factors to infection: EtOH/Drugs, Viral infection, pulmonary congestion, splenectomy (sickle cell)

Treatment
Empirical Vancomycin, Ceftriaxone, Penicillin, Fluroquinolones, Azithromycin (for less severe disease)
Prophylaxis: 23 valent vaccine (65 and up or 19 and up with risk factors). 13 valent (children)

Mortality
High in immunocompromised and elderly

Key findings/Diagnosis
OPTOCHIN sensitive, Catalase Negative, Quellung reaction
CXR: LOBAR consolidation
Dx: Gram stain and culture (negative most of the time), Rapid urinary antigen test

Question 2

Staphylococcus aureus
• Stucture
• Type of Pneumonia
• Transmission
• Replication Cycle
• Disease Presentation
• Pathogenic Mechanism
• Epidemiology
• Treatment
• Mortality
• Key findings/Diagnosis

Answer 2

Stucture
Gram positive cocci in clusters, Beta Hemolytic

Type of Pneumonia
Typical CAP, HAP, HCAP - often post-viral

Transmission
normal flora

Replication Cycle
not mentioned

Disease Presentation
Presents as typical pneumonia with rapid onset, high, fever. Complications include necrotizing pneumonia and lung abscess (coughing up foul smelling sputum).

Pathogenic Mechanism
Lots of invasive methods for this bug

Epidemiology
not mentioned

Treatment
not mentioned

Mortality
not mentioned

Key findings/Diagnosis
CXR: Patchy infiltrate, Typically a bronchopneumonia (makes sense b/c lobar is typically associated with capsule)

Question 3

Pseudomonas aeruginosa
• Stucture
• Type of Pneumonia
• Transmission
• Replication Cycle
• Disease Presentation
• Pathogenic Mechanism
• Epidemiology
• Treatment
• Mortality
• Key findings/Diagnosis

Answer 3

Stucture
AEROBIC gram-negative bacilli

Type of Pneumonia
Typical HCAP, HAP, VAP

Transmission
not mentioned

Replication Cycle
Grows well in Water souces

Disease Presentation
Like a typical pneumonia. May also cause burn wound infections, sepsis, EXTERNAL Otitis ESPECIALLY IN DIABETICS, UTIs, Hot tub folliculitis

Pathogenic Mechanism
Exotoxin A shuts down protein synthesis by inactivating EF-2 by ADP ribosylation (similar to diptheria). Endotoxin elicits the inflammatory response (FEVER, SHOCK). Factors that allow it to cause extensive vasculitis with thrombosis and hemorrhage - elastase, leucocidin, hemolysins, proteases.

Epidemiology
Cystic Fibrosis patients

Treatment
Highly Resistant, Cefepime, Meropenum, Ciprofloxacin, Pip/Tazo, Genatmicin.

Mortality
not mentioned

Key findings/Diagnosis
Culture: Aerobic, DOES NOT ferment LACTOSE, OXIDASE +, Grape odor

Question 4

Klebsiella pneumoniae
• Stucture
• Type of Pneumonia
• Transmission
• Replication Cycle
• Disease Presentation
• Pathogenic Mechanism
• Epidemiology
• Treatment
• Mortality
• Key findings/Diagnosis

Answer 4

Stucture
Encapsulated, Gram negative bacillus, Ferments lactose

Type of Pneumonia
Often lobular but both are certainly possible

Transmission
Not mentioned

Replication Cycle
Not mentioned

Disease Presentation
Typical pneumonia

Pathogenic Mechanism
Capsule of K. pneumoniae is one of its key virulence factors. Often infections are the result of aspiration as this is a normal bacteria of the GI tract.

Epidemiology
Typically seen in alcholics (aspiration) and malnourished.

Treatment
Resistance is common

Mortality
High potential for abscess and necrotizing pneumonia

Key findings/Diagnosis
Key: Indole negative (unlike P. aeruginosia), Incapable of growth at 10 Celcius, CURRANT JELLY (from mucoid polysaccharide capsule).

Question 5

Haemophilus influenzae
• Stucture
• Type of Pneumonia
• Transmission
• Replication Cycle
• Disease Presentation
• Pathogenic Mechanism
• Epidemiology
• Treatment
• Mortality
• Key findings/Diagnosis

Answer 5

Stucture
Encapsulated/non-encapsulated gram-negative (coccobacillary) ROD; pleomorphic; non-motile

Type of Pneumonia
CAP typical pneumonia

Transmission
Replication Cycle

Disease Presentation
Typical pneumonia. Often causes Epiglotitis, otitis media and meinigitis too (if encasulated). Most common cause of Acute exacerbations of COPD.

Pathogenic Mechanism
Capsule is the most important virulence factor with capsular type B beingthe most invasive.

Epidemiology
Patients with COPD

Treatment
Amoxicillin if mild. Ceftriaxone for more serious infection.

Mortality
Not mentioned

Key findings/Diagnosis
Key: Facultative anaerobe, REQUIRES CHOCOLATE AGAR factors V (NAD+) and X (hematin) for growth

Question 6

Moraxella catarrhalis
• Stucture
• Type of Pneumonia
• Transmission
• Replication Cycle
• Disease Presentation
• Pathogenic Mechanism
• Epidemiology
• Treatment
• Mortality
• Key findings/Diagnosis

Answer 6

Stucture
Gram negative coccobacillary rods

Type of Pneumonia
Typical CAP

Transmission
not mentioned

Replication Cycle
Not mentioned

Disease Presentation
Typical pneumonia. Increasingly recognized as a cause of bacterial pneumonia, especially in the elderly. 2nd most common bacterial cause of acute COPD exacerbation

Pathogenic Mechanism
Not mentioned

Epidemiology
Old People

Treatment
not mentioned

Mortality
not mentioned

Key findings/Diagnosis
Not mentioed

Question 7

Acinetobacter baumanii
• Stucture
• Type of Pneumonia
• Transmission
• Replication Cycle
• Disease Presentation
• Pathogenic Mechanism
• Epidemiology
• Treatment
• Mortality
• Key findings/Diagnosis

Answer 7

Stucture
Gram-negative coccobacillary rods (typically opportunistic)

Type of Pneumonia
(V)HAP (often associated with respiratory equipment)

Transmission
Commonly found in the soil and water (like pseudomonas) and can be a part of the normal flora.

Replication Cycle
Not mentioned

Disease Presentation
May also cause sepsis, line infections, and UTIs

Pathogenic Mechanism
Not mentioned

Epidemiology
IMMUNOCOMPROMISED

Treatment
HIGHLY RESISTANT to many abx.

Mortality
Not mentioned

Key findings/Diagnosis
Not mentioned

Question 8

Mycoplasma pneumoniae
• Stucture
• Type of Pneumonia
• Transmission
• Replication Cycle
• Disease Presentation
• Pathogenic Mechanism
• Epidemiology
• Treatment
• Mortality
• Key findings/Diagnosis

Answer 8

Stucture
No Cell wall

Type of Pneumonia
Atypical ‘walking’ pneumonia

Transmission
Occure most often with young people in close quarters

Replication Cycle
Not stated

Disease Presentation
Insideous onset of dry cough, headache, low-grade fever, myalgias, sore throat. Patients may also have CNS ENVOLEMENT, Rash, Hemolysis, Cardiac involvment (myocarditis etc.) .

Pathogenic Mechanism
Adhesin bind to ciliated epithelial cells and causes reduced ciliary clearance - adhesin is a key virulence factor

Epidemiology
Prison people, Military Recruits, School-aged kids

_Treatment_ 
Macrolide (azithromycin), doxycycline, or flouroquinolone 

Mortality
Not mentioned

Key findings/Diagnosis
• Cold Agglutinins are IgM antibodies
Dx: EATON AGAR or PCR on respiratory secretions, Serology is not great

Question 9

Chlamydophila pneumoniae
• Stucture
• Type of Pneumonia
• Transmission
• Replication Cycle
• Disease Presentation
• Pathogenic Mechanism
• Epidemiology
• Treatment
• Mortality
• Key findings/Diagnosis

Answer 9

Stucture
OBLIGATE intracellular, gram negative rod (note you won’t see it on the gram stain because its obligate intracellular)

Type of Pneumonia
Aytpical pneumonia

Transmission
Nursing Homes etc.

Replication Cycle
Not mentioned

Disease Presentation
Insideous onset of dry cough, headache, low-grade fever, myalgias, sore throat.

Pathogenic Mechanism
Intracellular so protected from antibodies and complement

Epidemiology
Affects older adults

Treatment
Doxycycline

Mortality
Key findings/Diagnosis

Question 10

Legionella pneumophila
• Stucture
• Type of Pneumonia
• Transmission
• Replication Cycle
• Disease Presentation
• Pathogenic Mechanism
• Epidemiology
• Treatment
• Mortality
• Key findings/Diagnosis

Answer 10

Stucture
Gram negative rod, facultative intracellular

Type of Pneumonia
Atypical

Transmission
Aerosol transmission from environmental source habitat (air conditioning systems)

Replication Cycle
Not mentioned

Disease Presentation
Legionnaire’s: dry cough, DIARRHEA, fever, confusion
Pontiac fever: mild flu-like symptoms

Pathogenic Mechanism
Avoids PHAGOLYSOSOME fusion and replicates within alveolar macrophages resulting in decreased clearance. Most important virulence factors = endotoxin.

Epidemiology
Seen most often in OLD PEOPLE, smokers, alcoholics, and comorbidities

Treatment
Macrolide or Fluroquinolone

Mortality
Not mentioned

Key findings/Diagnosis
• CXR: diffuse infiltrates, consolidation, pleural effusion

• Gram stain: Macophages, neutrophils, but no bug
SILVER STAIN required.

• Must be grown on **Charcoal yeast extract culture with iron and cysteine
• HYPONATREMIA**

• Clinicaly Urinary antigen is most commonly used in Dx.