Term
| what is TB of the spine called? |
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Definition
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Term
| for whom is TB a possible occupational problem? |
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Definition
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Term
| what bacteria is responsible for most cases of TB? how do they appear? |
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Definition
| mycobacterium TB, which are slender bacteria and aerobic rods that grow in straight or branching chains |
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Term
| why are mycobacterium TB referred to as acid fast bacteria? how do they gram stain? |
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Definition
| m TB have a waxy cells composed of mycolic acid, which retains stains even after treatment with a mixture of alcohol and acid (thus: acid fast). mycobacterium stain weakly with gram stain. |
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Term
| how does TB interact with HIV? how major is it in terms of global disease? |
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Definition
| TB is the leading cause of death worldwide, and HIV infection makes people more susceptible to the effect of TB |
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Term
| who does TB affect most commonly? |
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Definition
| TB flourishes wherever there is poverty, crowding, and chronic debilitating disease. in the US, TB is mainly a disease of the poor/elderly/urban poor/HIV infected. |
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Term
| what % of people infected w/TB contract the disease? |
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Definition
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Term
| how is TB transmitted? what does the presence of the organisms in a pt indicate? |
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Definition
| TB is transmitted by *airborne droplets, though infection (presence of organisms) may or may not cause clinically significant disease. in most cases TB is asymptomatic, but *it can cause fever and pleural effusion |
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Term
| what is often the only sign of TB infection? |
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Definition
| a small fibrocalcific nodule at the point of infection, in which viable organisms may remain dormant in the lesions for years - and when the person's immune system is compromised, the infection can reactivate to cause communicable and potentially life-threatening disease. |
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Term
| what does a positive TB test mean? |
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Definition
| a positive TB test indicates the presence of cell mediated hypersensitivity to tubercular antigens - *but does not differentiate between disease and infection |
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Term
| what does the pathogenesis of TB in an previously unexposed immunocompetent person depend on? |
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Definition
| cell mediated immunity - which gives resistance to the bacteria and results in hypersensitivity to the tubercular antigens. the hypersensitivity response leads to *caseating granuloma and *cavitation. |
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Term
| how does m TB enter the macrophage? |
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Definition
| TB enters the macrophage via several receptors, and once inside - the macrophage *replicates in the phagosome by *blocking fusion of the phagosome and lysosome |
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Term
| does m TB block phagolysosome formation? how? what does this stage allow? |
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Definition
| m TB blocks *phagolysosome* formation by inhibition of *Ca++ signals, *recruitment, and *assembly of the proteins which mediate the phagosome-lysosome formation. this stage allows multiplication of the organisms in the alveolar airspaces and alveolar macrophages. |
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Term
| what happens 3 wks after a TB infection? |
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Definition
| a *TH1 response is mounted, activating macrophages to become bactericidal. mature TH1 produce *interleukin which drives the macrophages to become competent to *contain the organism as well as forming granulomas and casesous necrosis (if you can't destroy it - wall it off). in some individuals - the response can cause tissue destruction |
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Term
| are viable m TB often found in the granulomas? |
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Definition
| the granulomatous response can often contain viable m TB |
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Term
| what is the morphology of *primary TB morphology*? |
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Definition
| inhaled bacilli attach to the distal airspaces of the *lower part of the upper lobe* or the *upper part of the lower lobe*. as sensitization develops, a 1-1.5 cm lesion of gray-white *inflammatory consolidation with a central area of necrosis appears - called a "ghon focus" |
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Term
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Definition
| in primary TB, the bacilli drain to regional lymph nodes which often caseate, and this combination of *parenchymal lung lesion (ghon focus) and *nodal lesion is called a *ghon complex*. in most cases, *cell mediated immunity controls the infection and the ghon complex undergoes *fibrosis and calcification* (these are typically referred to as "burnt-out TB" which do not usually contain viable organisms) |
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Term
| what are the clinical features of primary TB? |
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Definition
| primary TB develops in a previously unexposed, unsensitized person and about *5% of newly infected people develop clinically significant disease. in primary TB, the source of the organism is *exogenous |
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Term
| what is the course of most primary TB pts? what is the course of the minority of TB pts? |
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Definition
| most pts have a latent course, but some may go on to have progressive infection. the progressive infection can involve the *lower and *middle lobes w/consolidation, hilar adenopathy, and pleural effusion. complications include *tuberculosis meningitis and miliary TB (small lesions occurring in various organs) |
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Term
| what does secondary TB consist of? |
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Definition
| secondary TB arises in a *previously sensitized host and it may *follow a primary TB (exogenous) or *arise from reactivation of dormant primary lesions (endogenous) many decades after initial infection |
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Term
| where is secondary TB located? why? |
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Definition
| secondary TB is located in the apex of the upper lobes of one or both lungs *due to the high O2 tension in the apicies, which promotes growth |
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Term
| what is the typical response to secondary TB? |
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Definition
| secondary TB elicits a prompt and marked tissue response due to the *preexistence of hypersensitivity. this occurs to wall off the focus of infection w/possible cavitation leading to dissemination of the organism into the airways which can be expectorated or swallowed |
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Term
| what is the clinical presentation of secondary TB? what is needed to make the most accurate dx? |
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Definition
| localized secondary TB may be asymptomatic or can cause malaise, weight loss and fever w/night sweats. and an increasing amount of sputum may occur w/possible hemoptysis and pleural pain. a positive cx is needed to make the most accurate dx |
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Term
| what characterizes the initial lesion in secondary TB? are bacilli present? |
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Definition
| the initial lesion is usually a small focus of consolidation less than 2 cm in diameter w/in 1-2 cm of the *apical pleura. it may undergo progressive fibrous encapsulation, leaving a fibrocalcific scar. *bacilli may be found in early lesions, but rarely in late ones. |
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Term
| who does progressive pulmonary TB generally occur in? |
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Definition
| progressive pulmonary TB can occur in the elderly and immunocompromised as apical lesions enlarge and expand their areas of cavitation. |
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Term
| even if the TB lesions heal, can the pulmonary architecture still head? |
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Definition
| the lesions may heal, but distortions of the pulmonary architecture are still possible |
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Term
| what may happen with the remaining cavities in secondary TB? when does miliary |
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Definition
| the remaining cavities may result in the spread of infection to the airway, lymphatics, or hematogenous route. *miliary pulmonary disease occurs when the bacilli drain through the lymphatics into the *lymphatic ducts, causing multiple small nodules scattered throughout the lung parenchyma |
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Term
| how are endobronchial, endotracheal and laryngeal TB spread? |
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Definition
| via lymphatics or expectorated infectious material |
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Term
| how does systemic miliary TB occur in pts w/secondary TB? |
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Definition
| infective foci in the lung seed the pulmonary venous return to the heart w/dissemination throughout the entire arterial system, involving many organs such as the spleen, kidney, adrenals (common), liver, etc |
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Term
| where can secondary TB seed hematogenously to? |
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Definition
| the adrenals, meninges, and bones (pott's disease) |
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Term
| can secondary TB result in lymphadenitis? |
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Definition
| yes, this is the most *frequent form of extrapulmonary TB* - usually occurring in the *cervical region* |
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Term
| can secondary TB result in intestinal infection? how does this happen commonly? |
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Definition
| yes, and this can be contracted by drinking contaminated milk as the organisms are trapped in mucosal lymphoid aggregations |
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Term
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Definition
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Term
| what is MAI? who is it most common in? |
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Definition
| mycobacterium avium-intracelluare complex which is composed of two different organisms (avium and intracelluare), but present as very similar disease. it is *most common in AIDS pts, and organisms are seen to proliferate in many organ systems, appear as abundant acid-fast bacilli in macrophages, and cause enlargement of the lymph nodes, liver, and spleen |
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