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sl 2013MISCELLANEOUS BACTERIA1BacteriaCharacteristicsEpidemiologyPathogenesis and VirulenceDiseasesLab DiagnosisTreatment

Mycobacterium tuberculosis

Weakly Gram + Strongly Acid FastAerobicCell wall: peptidoglycan & lipoarabinogalactanSpread: aerosolLocation: patients with active TB infectionRisk Factors: 1. Geographic (Asia, Eastern Europe)2. Exposure to infected groupAt Risk:1. Immunocomp2. Drug/Alcohol abuser, homeless3. Exposed individualsVirulence1. Trehalose mycolate or cord factor: induces granuloma formation2. Establishes lifelong infection: intracellular pathogen3. Prevent phagolysosome fusion: sulphatide secretion4. Phagosome fuses with other intracellular vesicles for nutrient access5. Oxidant inactivation: evade macrophage killing6. Stimulate IL-12 and TNF- release: TH1 CD4+ response IFN- and nitric oxide release

Pathogenic Development1. Macrophages and lymphocytes are attracted to infectious focus2. Fuse to form Langhan giant cells3. Granuloma formation to prevent further spread of bacteria4. TH1 CD4+ cells attempt to control and eradicate the infection via pro-inflammatory and cell-mediated cytokines5. Depending on the size of the focus, the bacteria can either get eradicated or remain dormantPrimary (children): Initial focus in subpleural part of lung activate cellular immunity replication ceases1. Pneumonia, abscess formation, cavitation in upper lobes and hilar lymphadenopathy2. Ghons complex: Calcification of healed primary lesion (scarring)3. Nonspecific complaints of weight loss, cough and night sweats4. Sputum: scant or bloody and purulent; can be associated with tissue destruction

Secondary (adults): Reactivation of dormant tubercle bacilli or reinfection spread to upper lobe apex1. Fibrocaseous cavitary lesion near apex of upper lobe

Miliary: Hematogenous widespread dissemination of tubercle bacilli1. Millet-like seeding in lung

Extrapulmonary: hematogenous spread of tubercle bacilli causing tissue destruction at lymph nodes, pleura, urogenital tract, bones, kidneysCulture collectionAcid Fast StainPCRVarious media: LJ, Middlebrook, BACTEC 460Chest X-ray

Tuberculin (Mantoux) skin test: injection of PPD intra-dermally>5mm: HIV px, immunosupp, contact with TB px>10mm: immigrants, IV drug users, hospital workers>15mm: no risk factors for TB

Quantiferon Gold Test: detect whole blood IFN-; immune reactivityRIPE: Rifampin, Isoniacid, Pyrazinamide, EthambutolBCG vaccineDOT: Directed Observed Treatment

Mycobacterium lepraeWeakly Gram + Strongly Acid FastAerobicSpread: aerosol or person-person contactLocation: armadillo, soil, contaminated personsAt Risk:1. Contact with infected person1. Prolonged contact required2. Low infectivity: longer duration for disease developmentChronic granulomatous lesion of peripheral nerves and mucocutaneous tissue (nasal mucosa)1. Tuberculoid leprosy: few skin lesions in cooler body tissues (nose, ears, fingers, testicles), CMI, low infectivity, lepromin +2. Lepromatous leprosy: extensive destruction of skin, immunity is depressed, high infectivity, lepromin - Acid-fast in lepromatous leprosyDapsoneRifampinClofazamine

Mycobacterium avium complex (MAC)Weakly Gram + Strongly Acid FastAerobicSpread: aerosol At Risk:1. HIV patients2. ChemotherapyAsymptomatic colonization in immunocompetentDissemination in immunocompromised1. Development of single infected nodule: disseminates in immunocompromisedMacrolides

Mycoplasma pneumoniae

Cell-wall has no peptidoglycan but contains sterol (requires cholesterol!)AerobicPleomorphic

Spread: aerosol Location: ubiquitousRisk Factors:1. Schools, prisons, military settings (close contact)At Risk:1. Children and young adults1. P1 adhesion protein: adherence to ciliated respiratory epithelia2. Eventual loss of ciliated epithelia: facilitate bacterial spread to lungs

**Fried egg appearance!!1. Upper Respiratory Tract Infection: low grade fever, headache, dry, non-productive cough2. Lower Respiratory Tract Infection: primary atypical pneumonia (walking pneumonia) mild, diffuse interstitial pneumonia; tracheobronchitis

**Pneumococcal pneumonia (Strep) is consolidate, lobar pneumoniaCold agglutinin test: Ab that lyses RBC in 4CPCRErythomycinDoxycycline

**Penicillin resistant (no cell wall)

Other Miscellaneous Bacteria:

U. urealyticum: causes non-gonococcal urethritisM. hominis: causes pyelonephritis, PID, post-partum fever