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Organisms That Can Cause Pneumonia (Bacteria)

Type of Organism 
Disease 
Most Common Mode of Transmission
Classic Features
Bacteria 
Gram positive cocci
Streptococcus pneumoniae
*most common cause of community acquired pneumonia in adults
*Typical pneumonia inhalation of droplets rusty sputum
Streptococcus pyogenes Typical pneumonia inhalation of droplets Group A Streptococcus, pneumonia that killed Jim Hensen (The Muppets creator)
Streptococcus agalactiae
common cause of pneumonia in 0-2 month old patients
Typical pneumonia inhalation of organisms as neonate passes down birth canal Group B Streptococcus, usually causes pneumonia in neonates.
Staphylococcus aureus Typical pneumonia IV drug use, inhalation of droplets, post-influenza  Multiple bilateral nodular infiltrates with central cavitation. In children one can see ill-defined, thin walled cavities ("pneumatoceles"), bronchopleural fistulas, and empyema. Common cause of pneumonia in cystic fibrosis patients
Peptostreptococcus sp. 
anaerobe
**Aspiration pneumonia Aspiration fluid-air levels, and abscess formation oftentimes seen on radiographs, foul breath, infiltrates in dependant lung segments
Bacteria
Gram positive rods
Bacillus anthracis Typical pneumonia, Anthrax, Wool-Sorters disease inhalation Associated with wool sorting,  with animal handlers, and veterinarians.
Nocardia sp.  ***Chronic pneumonia inhalation; immunocompromised hosts beaded  filamentous appearance of the  rod shaped bacteria, Pleura and chest wall involvment
Actinomyces sp. 
anaerobe
Chronic pneumonia Aspiration sulfur granules and a beaded appearance of the branched filamentous rod shaped bacteria, Rib destruction, Cutaneous sinuses, cavitation, spreads to pleura and chest wall
Bacteria
Gram negative cocci
Neisseria meningitidis Typical pneumonia inhalation  epidemics in military recruits
Moraxella catarrhalis Typical pneumonia inhalation
Bacteria
Gram negative Rods
Klebsiella pneumoniae Typical pneumonia aspiration Current Jelly sputum, more commonly seen in patients with COPD, alcoholics, and the elderly, Bulging fissure sign of chest radiograph, lung necrosis 
Escherichia coli
common cause of pneumonia in 0-2 month old patients
Typical pneumonia aspiration usually seen in neonates, lung necrosis
Pseudomonas aeruginosa Typical pneumonia aspiration or inhalation green sputum, abscess formation, Common cause of pneumonia in cystic fibrosis patients and those with 
severely compromised respiratory defenses.
Acinetobacter sp. Typical pneumonia aspiration or inhalation , often found on  respiratory therapy equipment and on human skin very difficult to treat due to multiple drug resistance.
Burkholderia pseudomallei Typical pneumonia inhalation exposure with contaminated soil
Burkholderia mallei Typical pneumonia inhalation exposure with contaminated soil
Yersinia pestis Typical pneumonia, Pneumonic plague Inhalation, or by hematogenous spread to lungs Initial plague patients acquire this disease via flea bites
Francisella tularensis Typical pneumonia, Tularemia Infection is via tick bite or contact with contaminated rabbits.
Hemophilus influenzae  Typical pneumonia inhalation more commonly seen in patients with COPD, alcoholics, and the 
elderly. 
Bordetella pertussis  Whooping cough inhalation bronchopneumonia
Bacteroides melaninogenicus
anaerobe
Aspiration pneumonia Aspiration fluid-air levels, and abscess formation oftentimes seen on radiographs, foul breath, infiltrates in dependant lung segments
Fusobacterium sp. 
anaerobe
Aspiration pneumonia Aspiration fluid-air levels, and abscess formation oftentimes seen on radiographs, foul breath, infiltrates in dependant lung segments
Porphyromonas sp. 
anaerobe
Aspiration pneumonia Aspiration fluid-air levels, and abscess formation oftentimes seen on radiographs, foul breath, infiltrates in dependant lung segments
Prevotella sp. 
anaerobe
Aspiration pneumonia Aspiration fluid-air levels, and abscess formation oftentimes seen on radiographs, foul breath, infiltrates in dependant lung segments
Proteus sp. Typical pneumonia inhalation, aspiration lung necrosis
Serratia sp. Typical pneumonia inhalation, aspiration usually seen in immunocompromised hosts
Bacteria that do not gram stain or gram stain poorly
Mycobacterium tuberculosis Chronic pneumonia inhalation ghon complexes, coin lesions, cavitation.
Other Mycobacterium sp.  Chronic pneumonia inhalation, usually seen in immunocompromised host
Legionella pneumophila ****Atypical pneumonia inhalation, usually the elderly or immunocompromised host Relative bradycardia, abdominal pain, Vomiting and diarrhea, hematuria, mental confusion, abnormal liver and renal function tests, increased CPK 
Mycoplasma pneumoniae - colonies
Most common cause of Atypical pneumonia in adults.
Atypical pneumonia inhalation bullous myringitis, cold agglutinin positive, cobweb like infiltrates of lungs
Chlamydia trachomatis Atypical pneumonia inhalation an afebrile pneumonia, usually seen in 2 wk to 6 months of age
Chlamydia psittaci Atypical pneumonia inhalation acquired from certain birds (ex. parrots), normal or low leukocyte count
Chlamydia pneumoniae
TWAR agent
Atypical pneumonia inhalation
Coxiella burnetii (Q-fever)  Atypical pneumonia ingestion of comtaminated milk, or inhalation of contaminated aerosols from barnyard animals abnormal liver function tests
*Typical pneumonia
**Aspiration pneumonia
***Chronic pneumonia
****Atypical pneumonia

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Last revised 8/9/13