Flashcards in Mycobacteria etc Deck (56)
What are the characteristics of Mycobacterium sp?
Acid fast (thick cell wall containing mycolic acid) - many branched lipids
What are the growth conditions for Mycobacterium sp?
Fastidious (have complex growth requirements)
Difficult to treat - hearty
What are the human Mycobacterium pathogens?
What are the characteristics of Mycobacterium tuberculosis (Mtb)?
Appear as white colony on Lowenstein-Jensen or Middlebrook's medium
What are some characteristics of pulmonary tuberculosis?
Less than 10% develop TB disease upon infection
Some people are latent carriers - tuberculin positive in absence of disease
What is the tuberculin skin test?
It measures the immune reaction to Mtb as a measure of exposure to the bacterium
Protein isolate from Mtb are injected in the skin and the size of reaction measured
Positive is greater than a certain threshold
What are the risk factors associated with TB?
IV drug use
Close contact with infected individuals
HIV status - TB is the leading cause of death for HIV infected individuals world wide
What does the primary infection of TB look like?
Inhale via respiratory droplets
Colonization of lung and uptake by phagocytosis into macrophages
Bacterial cell wall inhibits phagosome-lysosome fusion and virulence factors prevent phagosome acidification
Macrophages remain unactivated, bacteria may replicate uncontrollably inside without antigen presentation
Following macrophage burst, activation of lymphocytes leads to granuloma formation
What is a TB granuloma?
infected cells surrounded by macrophages and lymphocytes
Caseous necrosis a characteristic feature of TB granuloma
What does a latent TB infection look like?
Occurs after initial infection and dissemination
Absence of clinical symptoms and no shedding, non-transmissible
May last for long period time before reactivation (if ever)
What happens following a reactivation of a latent TB infection?
Granulomatous infection leads to necrosis, cavitation, release of bacteria into respiratory droplets
What are the clinical features primary or post primary pulmonary TB?
Fever, nausea, productive coughing
Chest pain, dyspnea
CXR: consolidation of lung (often upper), for patients with HIV/immunosuppressed consolidation may be mild/absent
What are the clinical features of primary progressive pulmonary TB?
Progressive nausea, loss of appetite, fatigue
Weight loss, muscle wasting
Productive cough with bloody sputum, dyspnea
What are some characteristics of extrapulmonary TB?
15-20% active cases and 50% of HIV cases
Spread to various organs, granulomas, multiple organ failure
CNS - tuberculosis meningitis
Bones and joints - Potts disease of the spine, osteomyelitis
Miliary TB - widespread
What are the prevention strategies for TB?
Novel immunotherapies in development: New ag, new platform, booster
What are some characteristics of M. leprae?
Granulomatous disease of URT, peripheral nerves
Progressive disease leads to characteristic lesions of the skin and deformation
Similar characteristics and morphology of Mtb
How is M. leprae transmitted?
person to person contact
ultimately unknown - maybe vector borne?
Armadillo only known non human reservoir
What does the initial infection of M. leprae look like?
Mild, often asymptomatic
Slow growing (5 year incubation period) symptoms may occur 20 years after infection
Hypopigmentation of the skin may be present
what is tuberculoid leprosy?
aka paucibacillary leprosy
milder form of the disease
large asymmetrical skin lesions - rash like, sensitive to touch
May progress to pain, muscle weakness, skin stiffness, dryness
Loss of nerve function = loss of skin sensation
What is borderline leprosy?
intermediate form of the disease (most common)
numerous lesions, may affect entire limbs leading to loss of function
This stage is unstable, may progress milder or more severe
What is lepromatous leprosy?
begins with small symmetrical, diffuse lesions
progress with larger extensive lesions
Deformity of skin and limbs, loss of innervation and function
Eye involvement: glaucoma, photophobia, blindness
What are characteristics of mycoplasma sp. and ureaplasma sp?
Lack cell walls - resistant to many antibiotics
smallest known cell
parasites and commensals of vertebrate hosts
mycoplasma are common contaminants in laboratories
What are the human pathogens of mycoplasma sp and ureaplasma sp?
Mycoplasma pneumonia - atypical walking
Mycoplasma genitalium - PID, bacterial vaginosis
Mycoplasma homonis - PID
Ureaplasma urealyticum - non specific urethritis, perinatal complications
What are symptoms of Mycoplasma pneumonia?
Atypical walking pneumonia
Also caused by C. pneumonia, L. pneumophile
Typically mild illness: cough, fever, chills, chest pain, fatigue, muscle soreness
More severe symptoms: eye pain, ear pain, sore throat, rash, lymphadenopathy
Complications involve: CNS invasion (meningitis) haemolytic anemia (very rare)
What are characteristics of M. genitalium, M. homonis?
Thought to be normal flora of genital tract
Associated with PID, bacterial vaginosis
Probably sequelae of other disease and or antibiotic use
What are characteristics of ureaplasma urealytica?
Normal flora of urogenital tract
Associated with non-specific urethritis
Associated with complications during pregnancy: sterility, stillbirth, preterm labour, meningitis, pneumonia in pregnant women
What are characteristics of filamentous bacteria? What is an example?
Segmented filamentous bacteria
Gram (+), spore forming, rod shaped (filamentous) clostridia like
non culturable cells adhere to intestinal epithelium
Pro-inflammatory in animal models of infection
lead to inhibition of growth in pathogenic organisms
lead to increase incidence of autoimmune or inflammatory diseases
What are characteristics of spirochaetes?
Spiral shaped, double membrane
anaerobic, or microaerophilic
Flagella run internally causing corkscrew motion
Gram (-) type cell wall but not classified by gram stain
What are human spirochaetes pathogens?
trepemona pallidum - syphilis
Borrelia burgdorferi - Lyme disease
leptospira sp- leptospirosis