Classification of Bacteria

Gram Positive Bacteria

  • Gram Positive Cocci

Staphylococci, they grow in clusters:
a Coagulase Positive: Staph Aureus.
b Coagulase Negative: Staph Epidermidis and Staph Saprophyticus.
Streptococci, they grow in pairs or chains:
a Alpha Hemolytic: Strep Pneumoniae and Viridans Strep.
b Beta Hemolytic: Strep Pyogenes (Group A) and Strep Agalactiae (Group B).
c Gamma Hemolytic: Strep Bovis (Group D).
Enterococci, they grow in pairs or chains:
a Enterococcus Faecalis: It causes the majority of enterococcal infections and is less resistant to Ampicillin, Vancomycin, and Aminoglycosides.
b Enterococcus Faecium: It is more resistant to Ampicillin, Vancomycin, and Aminoglycosides.

  • Gram Positive Rods

Corynebacterium Diphtheriae and Corynebacterium Jeikeium.
Bacillus Anthracis and Bacillus Cereus.
Nocardia.

  • Gram Positive Coccobacilli

Listeria Monocytogenes.
Note: Gram positive cocci tend to cause infection of the skin, soft tissue, hardware, indwelling lines, bone, joints, heart, and lung.

Gram Negative Bacteria

  • Gram Negative Cocci

Neisseria Meningitides and Neisseria Gonorrhoeae.

  • Gram Negative Rods

Pseudomonas Aeruginosa.
Enterobacteriaceae (enteric gram negative rods), they include E. coli, Klebsiella, Proteus, Salmonella, Shigella, Yersinia, Citrobacter, Serratia, and Enterobacter.
Brucella.
Francisella Tularensis.
Bartonella Henselae.
Helicobacter Pylori.
Stenotrophomonas.
Acinetobacter.

  • Gram Negative Coccobacilli

Moraxella Catarrhalis.
Haemophilus Influenzae (H. flu).
Bordetella Pertussis.
Note: Gram negative rods tend to cause infection of the lung (HCAP, HAP, and VAP), any intraabdominal organ, and genitourinary tract.

Anaerobes

  • Gram Positive Cocci

Peptostreptococci.

  • Gram Positive Rods

Clostridium spp.
Actinomyces Israelii.

  • Gram Negative Rods

Bacteroides and Fusobacterium.
Note: Anaerobes tend to cause infection of the oral cavity, lung (abscess), and any intraabdominal organ.

Atypical Bacteria

  • Legionella

Legionella Pneumophila causes atypical pneumonia.

  • Rickettsia

They require arthropod vectors and are obligate intracellular parasites.
Rickettsia Rickettsii causes RMSF.

  • Chlamydia

They are obligate intracellular parasites.
Chlamydia Trachomatis causes trachoma, PID, prostatitis, and urethritis.

  • Chlamydophila

They are obligate intracellular parasites.
Chlamydophila Pneumoniae causes atypical pneumonia.
Chlamydophila Psittaci causes psittacosis.

  • Mycoplasma

They lack a cell wall.
Mycoplasma Pneumoniae causes atypical pneumonia.
Mycoplasma Genitalium.
Note: Atypical Bacteria tend to cause infection of the lung (CAP).