Mycobacteria and Related Pathogens

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Questions and Answers

Which feature allows mycobacteria to be resistant to detergents, drugs, and desiccation?

The mycolic acid content in the cell wall (correct)

Formation of spores

Presence of peptidoglycan in the cell wall

Ability to stain well by the Gram method

What is the primary means of transmission for Mycobacterium tuberculosis?

Respiratory droplets (correct)

Contaminated water supply

Vector-borne transmission

Direct contact with infected sores

What type of growth pattern is characteristic of mycobacteria due to the presence of cord factor?

Formation of biofilms

Spore-based growth

Exponential growth with increased nutrient absorption

Filamentous growth (correct)

In which form of tuberculosis does the infection remain dormant but can reactivate later?

Latent tuberculosis Signup and view all the answers

What is the estimated number of people worldwide currently infected with Mycobacterium tuberculosis?

2 billion Signup and view all the answers

What is a significant characteristic of MDR-TB?

Resistant to isoniazid and rifampin Signup and view all the answers

Which of the following statements regarding the BCG vaccine is true?

It is a live attenuated strain of Mycobacterium bovis. Signup and view all the answers

What is the role of ELISA in the diagnosis of active tuberculosis?

Determines the presence of IFN-γ. Signup and view all the answers

What is the primary cause of infections by M.avium complex (MAC) in immunocompromised patients?

Disseminated disease and focal lymphadenitis. Signup and view all the answers

Which of the following agents is FDA approved for the treatment of XDR-TB?

Pretomanid in combination with bedaquiline and linezolid Signup and view all the answers

What is the primary mode of transmission for Nocardia infection?

Inhalation of aerosolized bacteria from soil Signup and view all the answers

Which of the following clinical presentations is most commonly associated with nocardiosis?

Acute bronchopneumonia Signup and view all the answers

What is the drug of choice for treating Nocardia infections?

Trimethoprim-sulfamethoxazole Signup and view all the answers

Which of the following characteristics best describes Actinomyces species?

Gram-positive filamentous rods and obligate anaerobes Signup and view all the answers

Which of the following statements is correct regarding the epidemiology of Actinomyces?

Actinomyces species are major contributors to dental plaque in the oral cavity. Signup and view all the answers

What is the primary role of low oxygen conditions in latent tuberculosis?

It triggers the bacteria to enter a dormant state. Signup and view all the answers

Which factor is least likely to contribute to the reactivation of latent tuberculosis?

Increased physical activity Signup and view all the answers

What is the consequence of granulomas rupturing in tuberculosis?

Spreading bacteria to other parts of the lung. Signup and view all the answers

Which of the following is NOT a clinical manifestation of extrapulmonary tuberculosis?

Cavitary lesions in the lungs Signup and view all the answers

How do mycobacteria evade the host immune response during infection?

By hiding inside granulomas. Signup and view all the answers

What is a major drawback of culturing sputum for tuberculosis diagnosis?

Does not detect non-culturable bacteria. Signup and view all the answers

Which of the following statements about tuberculosis is true?

Bacterial latency can occur without significant immune response. Signup and view all the answers

What is the purpose of the Tuberculin/Mantoux Test?

To assess the immune response to TB exposure. Signup and view all the answers

What is the most common form of actinomycosis?

Oral-cervicofacial actinomycosis Signup and view all the answers

Which species of Actinomyces is highlighted as an 'early colonizer' in plaque biofilms?

Actinomyces naeslundii Signup and view all the answers

What type of pathogen is Actinomyces considered?

Opportunistic pathogen Signup and view all the answers

What tends to trigger actinomycosis development?

Trauma to mouth or jaw Signup and view all the answers

Which condition has an established occurrence of Actinomyces israelii due to intrauterine devices?

Chronic Pelvic Inflammatory Disease Signup and view all the answers

What is the typical manifestation of oral-cervicofacial actinomycosis?

Submandibular swelling Signup and view all the answers

What characters distinguish Eubacterium species?

Gram-variable rods or filaments Signup and view all the answers

Which interaction is associated with Actinomyces israelii in dental plaque?

Interacts with Fusobacterium nucleatum Signup and view all the answers

Study Notes

Mycobacteria General Information

Cause chronic infections that may spread throughout the body.
Major human pathogens include:
- Mycobacterium tuberculosis (TB)
- Mycobacterium leprae (leprosy)
- Mycobacterium avium complex (MAC), comprising M. avium and M. intracellulare.

Mycobacteria Morphology and Physiology

Morphology: Thin rods, non-motile, do not form spores.
Staining: Acid-fast positive, requiring special staining methods due to poor Gram stain results.
Cell wall: Contains mycolic acid (waxy consistency) and lipoarabamannan (LAM), providing hydrophobic properties and protection against detergents and drugs.
Physiology: Obligate aerobes with slow growth (colonies visible in 8-10 days); grow in filaments due to cord factor.

Tuberculosis Overview

Current incidence in the U.S. is 2.9 cases per 100,000 persons (2023).
Approximately 2 billion worldwide are infected, with 30 million having active disease.
Transmission primarily occurs through respiratory droplets or ingestion of unpasteurized milk.

Tuberculosis Pathogenesis

Initial infection occurs via inhalation, leading to intracellular growth within alveolar macrophages.
Granulomas form to contain bacteria, presenting as latent tuberculosis where bacteria become dormant.
Reactivation occurs due to factors such as waning immunity and underlying health conditions, causing dissemination of bacteria and lung cavity formation.

Clinical Manifestations of Tuberculosis

Symptoms include gradual body wasting, cough, fever, and significant pulmonary issues.
Extrapulmonary tuberculosis can affect various organs, including the mouth, kidneys, meninges, and skin, especially in immunocompromised patients.

Diagnosis of Tuberculosis

Diagnosis methods include sputum acid-fast stain, culture, tuberculin (Mantoux) test, chest X-ray, and interferon-gamma release assays (IGRA).
Chest X-rays may reveal cavitary lesions and other lung abnormalities.

Treatment and Prevention of Tuberculosis

Treatment requires multiple antibiotics for several months, tailored to TB type and drug susceptibility.
Multidrug-resistant TB (MDR-TB) resists isoniazid and rifampin; extensively drug-resistant TB (XDR-TB) is resistant to additional antibiotics.
BCG vaccine (live attenuated strain) is used in developing countries but not in the U.S., as it provides limited prevention against pulmonary TB.

Mycobacterium Avium Complex (MAC)

Involves infections from M. intracellulare and M. avium, primarily affecting individuals with HIV/AIDS and causing pulmonary infections in immunocompetent people.

Nocardia Overview

Nocardia are Gram-positive bacilli with branched/filamentous growth.
Cell wall contains intermediate-length mycolic acid, partially acid-fast.
Important pathogens include Nocardia asteroides and Nocardia brasiliensis.
Transmission occurs through inhalation, skin trauma, or eye injury.

Nocardiosis Clinical Presentation

May present as acute, chronic, or relapsing infections, often starting with pulmonary difficulties.
Symptoms include cough, fever, and breathing difficulties, with potential dissemination leading to brain abscesses.

Diagnosis and Treatment of Nocardiosis

Diagnosis through Gram staining or culture of affected tissue.
Treatment involves assessing antibiotic sensitivity; Trimethoprim-sulfamethoxazole is the first-line drug.

Actinomyces Overview

Actinomyces are Gram-positive, filamentous rods, obligate anaerobes linked to chronic infections.
Frequently found in the oral cavity, especially in dental plaque, and associated with periodontal disease.

Actinomyces Clinical Manifestations

Most common manifestation is oral-cervicofacial actinomycosis, characterized by swelling, abscess formation, and draining sinus tracts, often related to poor oral hygiene.
Actinomyces israelii is commonly found in biofilms and interacts with other oral bacteria.

Chronic Actinomycosis

Can lead to chronic pelvic inflammatory disease, particularly in women using intrauterine devices.

Eubacterium Overview

Eubacterium species are Gram-variable and obligate anaerobes; several strains are asaccharolytic, found in various body sites.

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Description

This quiz covers essential information about Mycobacteria, Nocardia, and Actinomyces. It includes details about major human pathogens, their morphology, and infection characteristics. Perfect for medical students or professionals looking to test their knowledge on these important bacteria.