Mycobacterium Spp. Flashcards
What are the general characteristics of Mycobacterium species?
71 species with Mycobacterium tuberculosis and Mycobacterium leprae as the most recognized
They are slender, slightly curved, or straight rod-shaped, nonmotile, and have a high lipid content in their cell walls.
What type of bacteria is Mycobacterium tuberculosis?
Slow growing, strictly aerobic bacteria
Incubation takes 2-6 weeks for most pathogenic mycobacteria.
How is Mycobacterium tuberculosis transmitted?
Through airborne droplet nuclei containing tubercle bacilli
These bacilli can be excreted by coughing, sneezing, or talking.
What are the symptoms of progressive pulmonary tuberculosis?
- Coughing
- Shortness of breath
- Night sweats
- Chills
- Fatigue
- Anorexia
- Weight loss
This occurs in a small percentage of individuals infected with tuberculosis.
What is miliary tuberculosis?
A common form of tuberculosis in patients with HIV and AIDS
It can occur due to dissemination in children, older adults, and those with immunodeficiencies.
What is the significance of the Mycobacterium Avium Complex (MAC)?
Increase in infections due to the number of AIDS patients
Symptoms are similar to pulmonary tuberculosis.
What is the purpose of digestion and decontamination of specimens?
- Liquify the sample
- Decontaminate sample of nonmycobacterial organisms
This process optimizes recovery of mycobacterial isolates.
What are common agents used for decontamination and digestion?
- NaOH (2%, 3%, 4%)
- N-acetyl-L-cysteine (NALC)
NALC is commonly used with NaOH to improve the yield of mycobacteria.
What are the conventional acid-fast staining techniques?
- Ziehl-Neelsen stain
- Kinyoun stain
Carbolfuchsin is the primary stain, acid alcohol is the decolourizer, and methylene blue is the counterstain.
What types of media are used for the isolation of acid-fast bacilli?
- Egg Based Media (e.g., Lowenstein-Jensen)
- Serum or Agar Based Media (e.g., Middlebrook 7H10, 7H11)
- Liquid Media (e.g., Middlebrook 7H9, 7H12, 7H13)
A combination of these media is typically used.
What is the BACTEC system used for?
Incorporates liquid media for the detection of mycobacteria
It uses 14C-labelled palmitic acid which mycobacteria metabolize to produce 14CO2.
True or False: Neisseria gonorrheae is always pathogenic.
True
What is the difference between Neisseria gonorrheae and Neisseria meningitidis?
Neisseria gonorrheae is always pathogenic; Neisseria meningitidis can be a commensal inhabitant
Neisseria meningitidis may reside in the upper respiratory tract of carriers.
What is the first step following the recovery of a mycobacterial isolate?
Determine the presence of acid fast bacilli by completing acid fast staining or auramine O staining.
What are the two types of colony morphology for Mycobacterium tuberculosis?
- Smooth and soft
- Rough and friable
What is the Runyon Classification used for?
To classify mycobacteria based on growth rate and recovery time.
What are the optimum incubation temperatures for certain species of mycobacteria?
Can be within very narrow limits.
Which species is always pathogenic: Neisseria gonorrheae or Neisseria meningitidis?
Neisseria gonorrheae is always pathogenic.
What is a characteristic of Neisseria meningitidis?
Can be a commensal inhabitant of the upper respiratory tract of carriers.
What are the three groups of mycobacteria classified by photoreactivity?
- Photochromogens
- Scotochromogens
- Nonphotochromogens
What is the most commonly used biochemical test for identification of Mycobacterium tuberculosis?
Niacin Accumulation.
What does a positive nitrate reduction test indicate?
May be seen with M. kansasii, M. szulgai, M. fortuitum, and M. tuberculosis.
What is the significance of heat stable catalase in Mycobacterium species?
Organisms with heat stable catalase enzymes will produce a positive catalase reaction after heating.
What is the result of hydrolysis of Tween-80?
Oleic acid and polyoxyethylated sorbitol.
What does the arylsulfatase enzyme do in Mycobacterium?
Hydrolyzes the bond between the aromatic ring and sulfate group.
What does pyrazinamidase convert pyrazinamide into?
Pyrazinoic acid and ammonia.
What is the role of NAP in inhibitory tests?
Inhibits species of the Mycobacterium tuberculosis complex.
What does TCH distinguish?
Distinguishes M. bovis from M. tuberculosis.
What type of infections are commonly caused by Nontuberculous Mycobacteria (NTM)?
Chronic pulmonary disease in those with underlying disease, immunosuppression or AIDS.
What is the Mycobacterium avium Complex (MAC)?
Includes M. avium and M. intracellulare.
What is the causative agent of Hansen’s disease?
Mycobacterium leprae.
What are the two forms of leprosy?
- Tuberculoid leprosy
- Lepromatous leprosy
What characterizes Tuberculoid leprosy?
Skin lesions with nerve involvement causing anesthesia in the affected area.
What characterizes Lepromatous leprosy?
A slowly progressing and malignant disease process resulting in skin lesions and symmetric nerve damage.
How is laboratory diagnosis of Mycobacterium leprae performed?
By demonstrating acid-fast bacilli that cannot be cultured from clinical samples.
Which class do Moraxella species belong to?
Proteobacteria
What is the relationship between Moraxella catarrhalis and Neisseria species?
Moraxella catarrhalis have morphology and biochemistry very similar to Neisseria species but are no longer part of the Neisseriaceae family.
Is Neisseria gonorrheae pathogenic?
Yes, Neisseria gonorrheae is always pathogenic.
Can Neisseria meningitidis be a commensal inhabitant?
Yes, Neisseria meningitidis can be a commensal inhabitant of the upper respiratory tract of carriers.
What is essential for the laboratory diagnosis of Mycobacterium leprae?
Demonstration of acid-fast bacilli that cannot be cultured from clinical samples.
In which type of leprosy are acid-fast bacilli abundant?
Lepromatous leprosy
In which type of leprosy are acid-fast bacilli extremely rare?
Tuberculoid leprosy
Which genera are included in the same class as Neisseria species?
- Kingella
- Eikenella
- Simonsiella
- Alysiella
- CDC EF 4a and b
- Acinetobacter
- Moraxella
