Actinomyces and Norcardia Flashcards
Actinomyces
- Gram +
- branching
- anaerobic
- yellow orange
- Actinomyces are normal inhabitants of some areas of the gastrointestinal tract of humans and animals from the oropharynx to the lower bowel. These species are highly adapted to mucosal surfaces and do not produce disease unless they transgress the epithelial barrier under conditions that produce a sufficiently low oxygen tension for their multiplication.
-Such conditions usually involve mechanical disruption of the mucosa with necrosis of deeper, normally sterile tissues (eg, following tooth extraction).
Actinomyces Pathogenesis
- Bacteria grow in microcolonies deep in tissues – Sulfur granule
- Eventually burrow to some surface
- Virulence or immune mechanisms unknown
Actinomyces Manifestations
Actinomyces Diagnosis
- Primarily clinical
- Demonstration of sulfur granule or isolation of Actinomyces species is extremely difficult
Actinomyces Treatment
• Penicillin – wait 4 to 6 weeks for response
Norcardia
- Related to mycobacteria
- Growth in 2-4 days
- Beaded appearance on Gram stain (weakly staining)
- Gram +
- aerobes
Norcardia Epidemiology
- Common in environment, particularly soil
- Pulmonary form
– inhaled dust
– Often immunocompromised
• Cutaneous form
– traumatic injection (gardening, thorns, cactus, etc.)
• No human-to-human transmission
Norcardia Pathogenesis
• Acute inflammation
– phagocytic resistance
• Mechanisms, virulence factors unknown
Norcardia Manifestations
• Bronchopneumonia
– cough, dyspnea
– Pleural extension, cavities
– Pneumonia brain abscess
• Cutaneous
– pustule, regional lymphadenitis
Norcardia Diagnosis
- Gram —> Acid-fast (modified)
- Culture – slow (2-3 days)
Norcardia Treatment
- Penicillin resistant
- Trimethoprim-sulfamethoxazole, imipenem, cefotaxime
