Bacterial Infections 2 Flashcards
TB meningitis is caused by
Mycobacterium tuberculosis (MTb)
MTb stanning
can’t be gram stained (b/c of nusual, waxy coating on its cell surface primarily due to the presence of mycolic acid)
test used - Acid-fast bacilli
MTb is a ____ pathogen
Facultative intracellular pathogen - lives inside and outside cells
Considered one of the most successful pathogens in history - only lives in humans - have been unable to find a resevar
Hallmark of MTb is its
very intricate and elaborated cell wall
very waxy - reason why had to diagnose and kill
layer of heavily modified lipids - cannot use gram staning
MT b Killed
1.6 million people in 2017
- mostly due to pneumonia and its complications
- ~5% of TB patients develop TB meningitis
- Mostly children, elderly, or HIV+ patients
TB meningitis is a result of
a bloodstream dissemination
- usually coming from the lung
- source site may be latent (lung granulomas)
TB meningitis First seeds the
meninges, usually around the base of the skull
- classic triad: headache/fever, malaise, and neck pain
May produce hydrocephalus and cranial nerve palsies
As disease progresses, the parenchyma can be seeded
- forms brain abscesses (can be known as tuberculomas- can be latent for years)
tuberculoma
(in brain) immune response - try to wall of to contain infection - but not clear it - later in life can break open
(granuloma - can also be in lungs)
TB entry into CNS
Multiple routes of entry
Expresses virulence factors that enable invasion of BMECs
- cross transcellularly [into SAS APCs in - pro inflammatory cytokines - activate endothelial (makes BBB more loose) - also attract immune to control infection into turbucluomas - immune can also already be infected (constant infltration of immune can also cause BBB breakdown)]
Can also survive inside phagocytes
- cross using Trojan horse
Once in parenchyma, recognition induces immune response - BBB breakdown
MTb is a ____ pathogen
NOT an opportunistic pathogen – will infect healthy individuals as well!
Risk factors for TB meningitis
- Close contacts of a person with infectious TB disease
- Persons who have immigrated from areas of the world with high rates of TB
- Persons who work or reside with people who are at high risk for TB (i.e. hospitals, jails, nursing homes, etc.)
- Immunocompromised individuals (i.e. HIV)
It is estimated ____ of the world has latent TB
1/4
No effective vaccine - high priority with rise in MDR [multi drug resistant] TB - treatment also involves months of antibiotics - causes other issues
Listeria monocytogenes acquired from
generally contaminated food - port of entry GI tract (mostly gastroenteritis - if healthy can contain it)
Treponema pallidum acquired from
generally sexually transmitted
Borrelia burgdorferi acquired from
tick-borne
Burkholderia pseudomallei acquired from
tropical climate, associated with water
L. monocytogenes morphology
Gram-positive bacillus
Facultative intracellular bacterium – can live both free or inside other cells
Has 12 recognized serotypes
L. monocytogenes serotypes
(based on presence of 2 antigens), three of which (1/2a, 1/2b, and 4b) cause most (95%) human illness
L. monocytogenes burden
Worldwide burden (2010) ~24,000 cases with 5,500 deaths
In US ~1,600 cases yearly with ~260 deaths
L. monocytogenes cycle food to brain
Gastroenteritis in healthy individuals
CNS infection in immunocompromised
individuals
Abortions in pregnant women
L. monocytogenes Expresses surface proteins that ____
No ___ BUT ____
promote invasion of non-phagocytic (end/epithelial) cells
No capsule, easily internalized by phagocytes
BUT Once intracellular, it escapes the vacuole (phagosome - into cytoplasm) and replicates in the cytosol