Chapter 1.15 Acid-Fast Bacteria Flashcards
What are the 2 most common mycobacteria?
mycobacterium tuberculosis- causes tuberculosis
mycobacterium leprae- causes leprosy
What is the cell type of mycobacteria?
rods with lipid-laden cell walls
obligate aerobe
form clumped colonies during infection
What staining is used for mycobacteria?
acid-fast staining that holds a red stain
*a smear of sputum
What patients are not able to fight tuberculosis?
HIV/AIDS patients due to no cell-mediated immunity
What organ does mycobacteria most commonly infect?
lungs where oxygen is abundant (and it’s an aerobe so it likes that)
What class of lipids is only present in acid-fast organisms?
mycosides
How does mycobacterium tuberculosis interact with the immune system?
- facultative intracellular growth- first exposure causes local infiltration of neutrophils and macrophages but do not die
- cell mediated immunity- some macrophages break down bacteria and present to T-helper cells– cause macrophages to attack lung tissue causing necrosis
What is the necrosis of tuberculosis called?
caseous necrosis
What hypersensitivity is associated with tuberculosis?
delayed-type hypersensitivity
What helps determine if a person has been infected with Mycobacterium tuberculosis?
Purified Protein Derivative PPD
*doesn’t mean the patient has TB but it means they were exposed to it at some point
What does a positive PPD test look like?
red, raised and hard skin after 1-2 days of injection of PPD
What is the clinical manifestation of person with asymptomatic primary tuberculosis?
granulomas that turn into fibrosis, calcified scar tissue
tiny tubercles
How is primary tuberculosis transmitted?
aerosolized droplet nuclei from respiratory secretions of an adult with TB
What is a Ghon focus
calcified tubercle in the middle or lower lung zone in tuberculosis
What is the clinical presentation of a patient with symptomatic primary tuberculosis?
occurs in infants or elderly
mediastinal or hilar lymph nodes
can cause necrosis and form holes in lungs
What are the general manifestations of primary tuberculosis?
large caseous granulomas in lung
cavitary lesions that fill with fluid
When do most adult cases of tuberculosis occur?
after bacteria has been dormant for a while
What is the most common type of reactivation (secondary) tuberculosis?
pulmonary tuberculosis
What is the clinical presentation of a patient with pulmonary tuberculosis?
chronic low-grade fever, night sweats, weight loss, productive cough
What is the appearance of lymph nodes in lymph node infection secondary tuberculosis?
cervical lymph nodes are swollen, mat together, and drain
*called scrofula
What is the clinical presentation if the kidney is involved in secondary tuberculosis?
red and white blood in the urine
no bacteria seen in gram stain or none grow in culture
*called sterile pyuria
What is the clinical presentation if the skeletal system is involved in secondary tuberculosis?
destruction of intervertebral discs and vertebral bodies
*called Pott’s disease
What is the clinical presentation if the central nervous system is involved in secondary tuberculosis?
subacute meningitis
granulomas in the brain
What is miliary tuberculosis?
tiny millet-seed-sized tubercles all over the body
chest film shows millet-seed pattern in lung
*occurs in children and elderly
What is the overall clinical picture of tuberculosis?
usually a chronic disease
weight loss
low-grade fever
can involve lots of organ systems
What are 4 tests that can be done to diagnose tuberculosis?
- PPD- indicates exposure in the past
- Chest X-ray- shows granulomas, Ghon focus, Ghon complex, old scarring in upper lobes, active tuberculosis pneumonia
- Sputum acid-fast stain and culture- if positive, means active pulmonary infection
- Rapid Molecular Detection of MTB- sputum sample
What is the “Rule of Fives” for tuberculosis?
- Droplet nuclei are 5 micrometers and contain 5 Mycobacterium tuberculosis bacilli
- Patient’s infected with Mycobacterium tuberculosis have 5% risk of reactivation in the first 2 years and then 5% lifetime risk
- Patients with “high five” HIV with have a 5 + 5% risk of reactivation per year
What is the disease caused by Mycobacterium leprae?
Leprosy (Hansen’s Disease)
What is the cell type of mycobacterium leprae?
acid-fast rod
How is mycobacterium leprae transmitted?
when a person is exposed to respiratory secretions or skin lesions of an infected individual
What does the clinical presentation of leprosy depend on?
- bacteria grow better in cooler body temperatures close to the surface
- severity depends on host’s cell mediated immune response to bacilli
Where on the body does mycobacterium leprae damage?
skin, superficial nerves, eyes, nose, testes
What are the 2 general types of leprosy?
- Lepromatous leprosy (LL)
2. Tuberculoid leprosy (TL)
Why is lepromatous leprosy the severest form of leprosy?
because patients canNOT mount a cell-mediated immune response
What organs are involved in lepromatous leprosy?
skin, nerves, eyes, and testes
What is the clinical presentation of a patient with lepromatous leprosy?
skin lesions over body, facial skin is thickened (leonine facies), nasal cartilage destroyed (saddlenose deformity), intertesticular damage (infertility), anterior eye damage (blindness), peripheral nerve thickness (loss of sensation)
What occurs in tuberculoid leprosy (TL)?
Patient’s with TL can mount a cell-mediated defense against the bacteria thus have milder symptoms
What is the clinical presentation of patient with tuberculoid leprosy?
localized superficial, unilateral skin and nerve involvement
well-defined, hypopigmented, elevated blotches
What are the most frequently enlarged nerves in tuberculoid leprosy?
*nerves closest to skin
greater auricular, ulnar, posterior tibial, peroneal
What is the lepromin skin test?
measures the ability of the host to mount a delayed hypersensitivity reaction against antigens of Mycobacterium leprae
What is the difference between LL and TL patients when given the lepromin skin test?
TL patients- cell-mediated response, + test
LL patients- do not have cell-mediated response, - test
What are nontuberculous mycobacteria (NTM)?
organisms that are ubiquitous in the soil and water
When is nontuberculous mycobacteria most likely seen?
in AIDS patients with disseminated Mycobacterium avium-complex (MAC) disease
What is the clinical presentation of a patient with mycobacterium avium-complex disease?
unexplained fevers, weight loss, diarrhea, malaise, elevation of alkaline phosphatase
How is diagnosis of mycobacterium avium-complex confirmed?
growth in mycobacterial blood cultures
