Polysaccharide Encapuslated Organisms

• Babesia Microti (see Babesiosis, [[Babesiosis]])
• Haemophilus Influenzae-Type B (see Haemophilus Influenzae, [[Haemophilus Influenzae]])
• Klebsiella Pneumoniae (see Klebsiella Pneumoniae, [[Klebsiella Pneumoniae]])
• Neisseria Meningitidis (see Neisseria Meningitidis, [[Neisseria Meningitidis]])
• Salmonella Typhi (see Salmonella Typhi, [[Salmonella Typhi]])
• Streptococcus Agalactiae (Group B Strep) (see Streptococcus Agalactiae, [[Streptococcus Agalactiae]])
• Streptococcus Pneumoniae (see Streptococcus Pneumoniae, [[Streptococcus Pneumoniae]])

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Organism Metabolic Characteristics

• Lactose Fermenting Gram-Negative Rod
  • Klebsiella (see Klebsiella, [[Klebsiella]])
  • Citrobacter (see Citrobacter, [[Citrobacter]])
  • Enterobacter (see Enterobacter, [[Enterobacter]])
  • E Coli (see E Coli, [[E Coli]])
• Non-Lactose Fermenting Gram-Negative Rod
  • Proteus (see Proteus, [[Proteus]])
  • Serratia (see Serratia, [[Serratia]])
  • Salmonella (see Salmonella, [[Salmonella]])
  • Shigella (see Shigella, [[Shigella]])
• Non-Fermenting Gram-Negative Rod
  • Pseudomonas (see Pseudomonas, [[Pseudomonas]])
  • Acinetobacter (see Acinetobacter, [[Acinetobacter]])
  • Stenotrophomonas (see Stenotrophomonas, [[Stenotrophomonas]])

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Moraxella Catarrhalis (see Moraxella Catarrhalis, [[Moraxella Catarrhalis]])

• Path: Gram-negative intracellular cocci

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Propionibacterium

• Anaerobe

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Peptostreptococcus

• Anaerobe

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Rhodococcus Equi (see Rhodococcus Equi, [[Rhodococcus Equi]])

• Path: Gram-positive coccus or bacillus
  • May stain weakly acid-fast

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Bacillus Anthracis/Listeria Monocytogenes

• Path: Gram-positive rod

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Nocardia

• Path: long, branching, Gram-positive filamentous rods (0.5 to 1.5 µm in diameter)
  • May stain weakly acid-fast

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Actinomyces

• Path: Gram-positive diphtheroidal or filamentous branching rods

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Mucor (Zygomycetes)

• Path: large (10-15 µm) broad 90° angle branching non-septate hyphae
  • Only rare side branches
  • No pseudohyphae or budding yeasts
  • Stain better with H+E than with fungal stains
• Rx: Posaconazole (not FDA released yet) or Ampho

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Fusarium

• Rx: Vori or Ampho

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Scedosporium

• Rx: Vori

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Aspergillus (see Aspergillus, [[Aspergillus]])

• Monomophic fungus
• Path: 45 degree angle branching
• Rx: Vori (superior to Ampho for invasive aspergillus)

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Candida

• 50% of infections are due to non-albicans species
• Rx-Candida albicans: Caspo or Mica
• Rx-Candida krusei: as many as 95% of Candida krusei isolates are Flucon-resistant, so Ampho B is indicated

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Histoplasma

• Dimorphic fungus (mycelial phase at RT and yeast phase at body temperature)
• Path: no characteristic morphologic features

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Coccidioides Immitis (see Coccidioidomycosis, [[Coccidioidomycosis]])

• Dimorphic fungus (mycelial phase at RT and yeast phase at body temperature)
• Path: spherules

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Paracocci

• Dimorphic fungus (mycelial phase at RT and yeast phase at body temperature)
• Path:

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Blastomyces

• Path: large organism (8-20 µm) with thick double-refractile cell wall/single-budding with broad base of attachment (”broad-based buds”)/multiple nuclei
  • 10% KOH exam: easiest technique to identify organism
  • Other fungal stains (PAS, calcofluor white, silver stain): more sensitive, especially when used in combination
  • PAP Stain: also sensitive (In one study, sputum were 78% positive by PAP, compared to 37% positive by KOH + PAS)

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Cryptococcus

• Monomophic fungus
• Path: forms vary in size, ranging from 2 to 15 µm with average diameters of 4 to 7 µm.
  • Yeast organisms have a thick mucinous capsule, which appears as clear halo in Grocott-Gomori methenamine silver staining