BMI10 - Nocardia, Fusobacterium, Actinomyces

What is canaliculitis?

Canaliculitis is an infection of the lacrimal canaliculus that commonly presents with unilateral tearing or discharge, red eye, and mild tenderness near the nasal aspect of the eyelid.

What are the common symptoms of canaliculitis?

Symptoms include unilateral tearing, ocular discharge, red eye, and mild tenderness near the medial canthus where the eyelids meet near the nose.

What is the most common bacterial cause of canaliculitis?

Actinomyces israelii is the most common bacterial cause of canaliculitis.

Which bacterial genera besides Actinomyces can cause canaliculitis?

Nocardia and Fusobacterium species can also cause canaliculitis.

Which fungal organisms can cause canaliculitis?

Candida, Fusarium, and Aspergillus species can cause canaliculitis.

Which viral pathogens can cause canaliculitis?

Herpes simplex virus (HSV) and varicella-zoster virus (VZV) can cause canaliculitis.

What is the Gram stain morphology of Actinomyces?

Actinomyces are Gram-positive rods.

What is the oxygen requirement of Actinomyces?

Actinomyces are facultative anaerobes.

Where are Actinomyces normally found?

Actinomyces are part of the normal oral microbiota.

Why are Actinomyces often confused with fungi?

Actinomyces develop filamentous forms or hyphae-like structures that resemble fungi.

When do Actinomyces typically cause disease?

Actinomyces cause disease when mucosal barriers are disrupted by trauma, surgery, or infection.

Are most Actinomyces infections endogenous or exogenous?

Most Actinomyces infections are endogenous, arising from the patient's own microbiota after barrier disruption.

What localized infections can Actinomyces cause?

Actinomyces can cause localized oral infections.

What is actinomycosis?

Actinomycosis is a chronic infection caused by Actinomyces that produces abscesses surrounded by dense, bumpy tissue.

What are sulfur granules in actinomycosis?

Sulfur granules are macroscopic bacterial colonies found in abscesses that appear orange-yellow in color.

What ocular infections can be caused by Actinomyces?

Actinomyces can cause canaliculitis and orbital actinomycosis.

What is the usual antibiotic susceptibility pattern of Actinomyces?

Actinomyces are susceptible to penicillin and most antibiotics.

Which Actinomyces species is most commonly associated with ocular disease?

Actinomyces israelii is the species most commonly associated with ocular infections.

What ocular diseases have been documented to be caused by Actinomyces israelii?

Endophthalmitis, keratitis, canaliculitis, and orbital actinomycosis.

What percentage of chronic lacrimal canaliculitis cases are caused by Actinomyces israelii?

Approximately 13–25% of chronic lacrimal canaliculitis cases are caused by Actinomyces israelii.

What percentage of all actinomycosis cases present as cervicofacial infections?

About 50% of actinomycosis cases present as cervicofacial infections.

How does orbital actinomycosis typically present?

It presents as a slowly progressive, chronic, nontender, indurated mass that may progress to abscesses, fistulae, and draining sinus tracts.

What are risk factors for orbital actinomycosis?

Immunosuppression, HIV/AIDS, poor dental hygiene, dental caries, dental extractions, gingivitis, gingival trauma, diabetes, irradiation, and malnutrition.

What symptoms were reported in the Actinomyces canaliculitis case study?

Severe itching, burning sensation, watering, and pain in one eye lasting six months.

What ocular finding was present in the Actinomyces canaliculitis case study?

A small white lesion was present in the medial canthus.

What organism was isolated from the canaliculitis case study?

Actinomyces israelii.

What skin changes may occur in orbital actinomycosis?

Lesions may have blue or red discoloration and can be mistaken for cellulitis.

What type of exudate is characteristic of orbital actinomycosis?

Yellow exudate containing sulfur granules.

What extraocular muscle finding may occur in orbital actinomycosis?

Ophthalmoplegia, which is paralysis or weakness of the eye muscles.

Why can orbital actinomycosis cause pain?

Pain may occur due to compression of adjacent structures.

What respiratory and swallowing symptoms may occur in orbital actinomycosis?

Dyspnea and dysphagia.

What constitutional symptoms may occur in orbital actinomycosis?

Fever, fatigue, and malaise.

When does lymphadenopathy usually appear in orbital actinomycosis?

Lymphadenopathy is usually a later finding in the disease course.

What visual symptom may occur in orbital actinomycosis?

Diplopia (double vision).

Why is orbital actinomycosis often difficult to diagnose?

It can mimic many other conditions, including malignancies.

How does orbital actinomycosis typically respond to treatment?

It usually responds to an initial course of broad-spectrum antibiotics.

How many accepted species are in the Nocardia genus according to the lecture?

There are 12 accepted species in the Nocardia genus.

Which Nocardia species is prominent in temperate regions?

Nocardia asteroides.

Which Nocardia species is common in tropical and subtropical regions?

Nocardia brasiliensis.

How does Nocardia stain?

Nocardia is weakly acid-fast and stains poorly with the Gram stain.

Why is Nocardia considered weakly acid-fast?

Because its cell wall contains mycolic acids similar to those found in Mycobacteria.

What type of cell wall does Nocardia possess?

Nocardia has a Gram-positive cell wall containing mycolic acids.

How can Nocardia be distinguished from Actinomyces?

Nocardia is weakly acid-fast, whereas Actinomyces is not acid-fast.

What is the oxygen requirement of Nocardia?

Nocardia are strict aerobes.

Where is Nocardia commonly found in nature?

Soil, dust, and decaying vegetation.

What microscopic structure does Nocardia form?

Branched filaments that resemble fungal hyphae.

How does Nocardia resist phagocytic killing?

It produces catalase and superoxide dismutase that neutralize toxic oxygen metabolites such as hydrogen peroxide.

What enzyme produced by Nocardia breaks down hydrogen peroxide?

Catalase.

What enzyme produced by Nocardia neutralizes superoxide radicals?

Superoxide dismutase.

What ocular infections can Nocardia cause?

Keratitis, canaliculitis, conjunctivitis, scleritis, dacryocystitis, orbital cellulitis, and endophthalmitis.

What pulmonary disease can Nocardia cause?

Bronchopulmonary disease.

What skin disease can Nocardia cause?

Cutaneous infections that may spread into deeper tissues.

What central nervous system infection can Nocardia cause?

Brain abscesses.

Are ocular Nocardia infections common or rare?

Ocular infections caused by Nocardia are rare.

What is the most common ocular infection caused by Nocardia?

Corneal infection (keratitis).

What percentage of bacterial keratitis cases in temperate climates are caused by Nocardia?

Fewer than 2% of bacterial keratitis cases.

In what climates is Nocardia keratitis seen more frequently?

Tropical and subtropical regions.

Why is Nocardia diagnosis often delayed?

Its clinical appearance resembles infections caused by other organisms.

Why is Nocardia keratitis clinically important regarding treatment?

It does not respond well to commonly used first-line bacterial keratitis medications such as fluoroquinolones.

What are the major risk factors for Nocardia ocular infections?

Trauma, surgery, corticosteroid use, and contact lens wear.

What types of trauma have been associated with Nocardia ocular infections?

Injury involving vegetative material, dirt, stone, flying insects, nails, and fish line sinkers.

What is the Gram stain morphology of Fusobacterium?

Fusobacterium are Gram-negative elongated rods.

What is the oxygen requirement of Fusobacterium?

Fusobacterium are strict anaerobes.

Where is Fusobacterium normally found?

The oral cavity and oropharynx as part of the normal microbiota.

What are the major diseases caused by Fusobacterium?

Eye infections, dental infections, and chronic infections of the sinuses and ears.

What ocular infections are associated with Fusobacterium?

Orbital cellulitis and orbital abscesses.

Are Fusobacterium eye infections common?

No, they are rare but often severe.

What are the most common ocular manifestations of Fusobacterium infection?

Orbital cellulitis and orbital abscesses.

What type of eye pain is characteristic of Fusobacterium orbital infection?

Severe, constant pain that worsens with attempted eye movement.

What orbital sign is commonly seen in Fusobacterium infection?

Proptosis (bulging of the eyeball).

What eyelid findings occur in Fusobacterium orbital infections?

Swollen, red, and tender eyelids.

What vision changes may occur with Fusobacterium orbital infection?

Blurred vision, double vision, partial vision loss, or complete vision loss.

What systemic symptoms may accompany Fusobacterium orbital infection?

Fever, headache, and malaise.

How can Fusobacterium rarely affect the lacrimal system?

It can cause lacrimal canaliculitis with recurrent swelling, discharge, and tearing near the inner corner of the eye.

What symptoms were present in the Fusobacterium necrophorum orbital cellulitis case?

Progressive proptosis, pain with eye movements, binocular diplopia, mucopurulent nasal discharge, and sinus congestion.

What organism was isolated from the sinus culture in the orbital cellulitis case?

Fusobacterium necrophorum.

What fungal organism was also isolated in the orbital cellulitis case?

Aspergillus.

What previous injury was noted in the Fusobacterium orbital cellulitis patient?

A remote orbital floor fracture that occurred five years earlier and did not require surgery.