BIOS441 exam 3: Actinomyces, Nocardia, Rhodococcus

phylum Actinomycetota

diverse phylum of Gram-positive bacteria with high GC content

genus Actinomyces

-Gram-positive

-non-motile

-facultative anaerobe--leans more anaerobic

-indole negative

-presence of "sulfur" granules in infections

fimbriae, mycolic acids, collagenase

Actinomyces virulence factors

site of infection

five major clinical forms of actinomycoses are classified by _________ _______ __________

oral-cervicofacial, thoracic, abdominal, pelvic, cerebral

five major clinical forms of actinomycoses

oral-cervicofacial actinomycosis

most common form of actinomycosis associated with poor oral hygiene, an invasive dental procedure or oral trauma that is characterized by tissue swelling with fibrosis and draining sinus tracts along the jawline

thoracic actinomycosis

actinomycosis associated with aspiration into the lungs and dissemination of the organisms into surrounding tissues

abdominal actinomycosis

actinomycosis associated with abdominal surgery or intestinal trauma

pelvic actinomycosis

actinomycosis whose primary infection is associated with IUDs in women, secondary infection is associated with spread from abdominal actinomycosis

cerebral actinomycosis

actinomycosis associated with secondary spread from another infected site and most commonly characterized by a single brain abscess

treatment and prevention for actinomycoses

-surgical debridement and long-term antibiotic therapy

-maintain good oral hygiene

-prophylactic antibiotics prior to invasive oral or abdominal surgical procedures

actinomycosis

chronic infection of the face and neck that produces abscesses and open draining sinuses

-usually caused by Actinomyces israelli, a common organism found in the nose and throat

hemoptysis

coughing of blood (or blood-stained sputum), common symptom of thoracic actinomycosis

cytology of pelvic actinomycosis

appears as filamentous balls of organisms during Pap smear

mycetoma

slowly progressing, destructive infections of the cutaneous and subcutaneous tissues, fascia, and bone caused by certain actinomycetes or fungi

-usually involves the foot or leg

-lesion consists of one or more lump-like enlargements containing granulomas and abscesses interconnected by sinus tracts and the presence of sulfur granules

Actinomyces bovis

Actinomyces species causing "lumpy jaw" of cattle

sulfur granules

mass of Actinomyces filaments solidifed with tissue exudates are characteristically found in pus from lesions and are diagnostic

genus Nocardia

-Gram positive

-non-motile

-aerobic

-aerial hyphae

-conidia/conidiospores (asexual, non-motile spores typically of a fungus)

nocardiosis

infection usually caused by N. asteroides or N. brasiliensis

-takes form of acute or chronic suppurative infection with abscess formation, usually of the lungs, but with marked tendency to spread to any organ

casein agar, starch agar, xanthine agar, tyrosine agar

identification methods for Nocardia spp.

negative

Nocardia spp. test results for identification methods are typically ___________ for all methods

Bovine farcy

first reported clinical disease (Edmond Nocard) caused by Nocardia farcinica characterized as a chronic form of glanders that affects the skin and superficial lymph vessels, formally named as N. asteroides in 1896

Nocardia infection process

1. entry: breach in skin or respiratory tract

2. attach to "suitable" surface: neutrophil

3. evade host immune response: produce superoxide dismutase and mycolic acid that inhibit fusion of lysosomes with phagosome in phagocytosis

4. acquire nutrients

5. multiple: grows slowly

depolarization

Nocardia spp. cause _____________ of the mitochondria, leading to apoptosis

pulmonary nocardiosis

most common infection of nocardiosis

brain abscess

most common CNS nocardiosis manifestation

treatments for nocardiosis infections

-sulfonamides

-trimethoprim-sulfamethoxazole

-12 months antibiotic therapy required to prevent relapse

-surgical drainage for abscesses

biopsy

diagnosis for nocardiosis

25%

overall mortality for nocardiosis

genus Rhodococcus

-Gram positive

-non-motile

-aerobic

-hyphae

-causes pneumonia (most common in foals)

virulence-associated protein A (VapA)

Rhodococcus virulence factor, highly immunogenic 15-18 kDa protein of unknown function

R. equi

Rhodococcus spp. causing the most common lung abscesses in foals between 1 and 6 months of age

R. equi

Rhodococcus spp., facultative intracellular bacterium that survives and grows in macrophages to establish its specific niche in the host cell

immunocompromised hosts

Rhodococcus equi primarily infects ______________ ___________ and is generally acquired through the lungs

treatments for R. equi

-macrolides and rifampin synergistic combination

-vancomycin

-aminoglycosides