Lecture 10 - Mycobacteria and spirochaetes Flashcards
What are the types of mycobacterium species?
Mycobacterium tubercolosis
MOTT (Mycobacterium Other Than Tubercolosis) / NTM (Non Tubercolosis Mycobacteria)
Mycobacterium leprae
What are the types of spirochaetes?
Genus Treponema
Genus Borrelia
Genus Leptospira
Genus Spirillum
What are the characteristics of Mycobacterium?
Very slow growers
Very fastidious growth requirements
Not detectable on Gram stain
Waxy mycolic acid in cell envelop making them resistant to drying
Why are mycobacterium so good at surviving for long periods of time?
Due to the presence of mycolic acid in their capsules
What type of stains work on mycobacterium?
Carbol fuchsin stain
Ziehl-Neelson stain
AFBs appear red against blue background
What type of stains work on mycobacterium?
Carbol fuchsin stain
Ziehl-Neelson stain
AFBs appear red against blue background
What are Acid Fast Bacteria (AFBs)?
They are bacteria that stain carbol fuchsin the stain cannot be removed with acid-alcohol
What is a Ziehl-Neelson stain?
A blue counter stain which contrasts with AFB
How are mycobacteria classified?
Using species complexes
What are the related species to the mycobacterium tubercolosis complex?
Mycobacterium tubercolosis
Mycobacterium Bovis
Mycobacterium bovis BCG (attenuated strain of mycobacterium bovis used in vaccines)
Mycobacterium africanum
How much of the population is infected by TB?
1/4 to 1/3 of the world’ds population
What kind of people have TB?
The urban homeless
Immigrants
AIDS patients
Which countries have TB most?
Developing countries
How is TB transmitted?
Through inhalation and spread by people with active pulmonary infection
How does pulmonary TB transfer from one person to another?
Open case of pulmonary TB occurs from lesions in the lungs opening into the airways and aerosol droplets get transferred between people
What happens after inhalation of TB?
Sometimes Bacteria is elminated by immune system
Other times the bacteria survive in granuloma of lung.(90 - 95% remain in granuloma whereas 5 - 10% are reactivated and cause disease in people in >50% in less than 2 years and in another 50% in more than 2 years.
What is pott’s disease?
Infection of vertebral body causing collapse of vertebrae and a hump appearance
What potential sites can TB be seen on?
Foci of infection could be focused in lungs as primary site of infection and then disease can move to distant organs (eg meninges, brain, myocardium, pericardium, bone, kidneys, lymphorectal tissue)
What can mycobacteria other than TB do?
Range of pulmonary diseases or disseminated disease in AIDS patients
lymphadenitis
chronic skin and soft tissue lesions
How is leprosy acquired?
Inhalation route or direct contact
How likely is it for mycobacterium leprae to cause disease?
Majority of infections are overcome by the immune system producing no symptoms
What is the response of the body to the leprosy pathogen caused by?
Host’s immune response
What are the types of leprosy responses?
Weak as in Lepromatous leprosy (weak CMI response)
Strong Tuberculoid leprosy (strong CMI response)
Which tissue is typically affected by leprosy?
skin
upper respiratory tract
peripheral nerves
testes
What are the defining features of tubercoloid leprosy?
Hypopigmented macules with raised red borders and the center lacks sensation
Damage to large nerves resulting in complete sensory loss in nerve’s distribution
What are the features of lepromatous leprosy?
Nodules, plaques, and generally thickened dermis
Heavy infiltration of upper respiratory tract particularly nasal with congestion and nosebleeds as well as destruction of nasal cartilage.
Destruction of bone and ear cartilage
Diffuse nerve involvement; sensory loss to hands and feet
Testicular invasion and impaired function; low testosterone
What are the types of spirochaetes?
Treponema
Borrelia
Leptospira
Spirillum
What is the spirochaete shape?
Spiral
Which treponema species are pathogenic to humans?
Treponema pallidum (syphilis)
Treponema pertenue (yaws)
Treponema endemicum (bejel)
Treponema carateum (pinta)
What does syphilis do?
Chronic disease that is sexually transmitted
What are the stages of syphilis?
primary
secondary
teriary quaternary
What are the symptoms of primary syphilis?
Chancre at inoculation site with raised edges
Painless
Raised firm edges
is syphilis limited to genital sites?
No it can happen to non-genital sites
What are the symptoms of secondary syphilis?
Fever
Fatigue
Myalgia
Skin rashes
Mucous patches
Condyloma lata (plaque like lesions)
meningitis can or may not manifest
What are the stages of latent syphilis?
Early latent syphilis is asymptomatic with recurrences of secondary syphilis lesions
Late latent syphilis is asymptomatic and can cause tertiary syphilis
What are the forms of tertiary syphilis?
Gummatous
Cardiovascular
Neurosyphilis
What is gummatous syphilis?
granulomatous lesions called gummas in skin and bone
What happens over time with gummatous lesions?
Destruction of surrounding tissue by expanding mass effect
In bone gumma produce pressure and deformity
What are the cardiovascular effects of tertiary syphilis?
Syphilic aortitis causing inflammation of small vessels feeding the aorta leading to aneurysm or dilation of aortic valve ring causing insufficiency of the valve
Coronary artery stenosis
Myocardial infarction
What are the symptoms of neurosyphilis?
Meningovascular syphilis causing aseptic meningitis, cranial nerve damage, and blindness/deafness
Parenchymatous syphilis Neuropsychiatric disturbance
Posterior spinal cord damage and inability to receive sensory peripheries
What are the symptoms of parenchymatous syphilis?
Neuropsychiatric disturbance and posterior spinal column damage “general paresis of the insane”
Inability to receive sensory input from peripheries “tabes dorsalis” (slapping feet gait)
How does syphilis affect neonates?
50% die and wide variety of symptoms in survivors
What are the symptoms in neonatal survivors of syphilis?
Hutchinson’s teeth
Saddle nose
rashes
What is yaws?
Chronic non-venereal disease caused by Treponema pertenue
What does non-venereal mean?
Not related to sexual intercourse
What does yaws affect?
Mainly skin and bone
Where is yaws typically seen?
Tropical areas in underprivileged commnities
How is treponema pertenue transmitted between people?
spread by contact
What is bejel?
Non-venereal syphilis like disease caused by treponema endemicum
Where is bejel typically seen?
In the tropics and acquired by children in conditions of poor hygiene
What is pinta?
Ulcerative or papular depigmenting skin disease caused by the bacteria; treponema carateum
How are borrelia species transmitted?
Insects
What are the species of borrelia relevant to us?
Borrelia recurrentis (epidemic louse-borne relapsing fever)
Borrelia burgdorferi (lyme disease)
Other Borrelia species (endemic tick-borne relapsing fever)
How do humans get leptospira infections?
Contact with domestic and wild animal tissue, urine, soil, mud or water containing urine
What are the symptoms of leptospira interrogans infection?
Spectrum of symptoms
Can cause flu like symptoms such as: sudden onset fever, malaise, severe headache, lowback+calf pain, photophobia
Or it can cause Weil’s disease which appears as jaundice, renal failure, obliguria, haemorrhage, and shock
How is spirillum minor transmitted between people?
Rat bites (uncommon infection)
