Actinomyces and Nocardia Flashcards
1
Q
What are the characteristics of Actinomyces?
A
- gram positive - filamentous
- elongated rods that branch at acute angles (branching bacilli)
- slow growers (4-10 days)
- microaerophilic (v. low levels of o2 needed to survive)/strictly anaerobic
- commensal microbe found in GI tract
- often form complexes in tissue/pus called sulfur granules any of the small yellow bodies found in the pus of actinomycotic abscesses and consisting of clumps of the causative actinomycete.)
2
Q
What are some species that causes actinomycosis?
A
- A. Israelli (most common)
- A. naeslundii (early colonizer during dental plaque formation)
- A. viscosus (involved in dental caries formation)
- A. odontolyticus
- A. meyeri
3
Q
What is actinomycosis?
A
- a relatively rare infection
- is a chronic inflammatory condition
- originates in tissues near mucosal surfaces
- disease progresses slowly
- characterized by a local hardening of tissue
- possibly draining sinus tracts
4
Q
What is the immune response to actinomyces?
A
- very poor immune response
- Ab can be detected
- infections are typically chronic and only resolve with antibiotics
5
Q
What is cervicofacial actinomycosis?
A
- it’s the most common site for actinomycosis
- it’s related too:
- poor dental hygeien
- tooth extraction
- trauma to mouth/jaw
6
Q
When and why does thoracic and abdominal actinomycosis happen?
A
- it’s rare
- happens due to aspiration or trauma
- diagnosis can be delayed due to vague symptoms
- often mistaken for malignancy
- intrauterine contraceptive devices can lead to chronic endometritis
7
Q
What is the diagnosis of actinomycosis?
A
- patient history
- type of lesion
- slow progression of lesion
- history of trauma to the area
- immunocompromised
- presence of organism in pus
- often can be contaminated with gram -negatives
- sulfur granules
- anaerobic culture for at least 10 days
- must use biochemical tests to distinguish it from propionibacteria (anaerobic, similar morphology)
8
Q
What’s the treatment of actinomycosis?
A
- treatment of choice: penicillin G
- also effective: ampicillin, doxycycline, erythromycin, clindamycine
- treatment course:
- high dose penicillin for up to 6 weeks
- followed by 6-12 months oral penicillin
- patients are often treated empirically if Actinomyces is suspected
9
Q
What is Nocardia and it’s characteristics?
A
- its natural found in soil
- it’s aerobic, gram positive, filamentous bacilli
- cell wall is composed of mycolic acids
- morphology is similar to actinomyces (branching bacilli)
- it is gram stained poorly
- it can appear beaded
- it can also appear as both Gm +/Gm -
- are strict aerobes
- can observe colonies after 2-3 days on blood agar or BHI
- it smells like mud
- it’s weak acid-fastness
10
Q
What’s the epidemiology of nocardiosis (how/where can it be found?)
A
- can be found in gingiva and respiratory tract of healthy individuals
- NOT A COMMENSAL ORGANISM
- 2 forms of disease:
- pulmonary (can be systemic)
- cutaneous
- disease is not spread by person-to-person contact
11
Q
What’s the pathogenesis of nocardia?
A
- disease process is poorly understood
- virulence factors (what makes it harmful): unknown
- resistant to microbicidal actions of phagocytes
- can survive in phagocytes
12
Q
What’s pulmonary nocardiosis?
A
- usually caused by:
- N. asteroides
- N. farcinica
- acute neutrophilic inflammation
- suppuration (pus formation) and destruction of parenchyma
- multiple abscesses may form
- dissemination (spreading) to other sites, such as the brain, is possible
13
Q
What’s cutaneous nocardiosis?
A
- result from direct inoculation of nocardia
- usually N. brasiliensis
- infection can range from superficial (pustule) to more similar to actinomycosis (draining sinuses and sulfur granules with prolonged infection)
14
Q
What’s the immunity to Nocardia?
A
- cell-mediated immune response (an immune response that does not involve antibodies, but rather involves the activation of phagocytes, antigen-specific cytotoxic T-lymphocytes, and the release of various cytokines in response to an antigen) because can survive inside phagocytes
- Th1 response
- little to no evidence for an effective humoral response
- why is this the preferred immune response?
- b/c the Ab created can’t get inside the macrophage/phagocyte
15
Q
How do you diagnose nocardia?
A
- diagnosis not as difficult as actinomycosis
- there’s usually more nocardia at site, so you can see a lot of it.
- can see the morphology, gram stain, and acid-fastness
- culture only takes a few days
- when plating, it may be necessary to use selective media (b/c this isn’t going to be the only caterer present, so need to use selective media to only plate this) like:
- buffered charcoal yeast extract
- thayer-martin agar
- culture requires 3-5 day
