MYCOBACTERIA CORYNEBACTERIA Lecture 40 Faculty: Dr. Alvin Fox

KEYWORDS Acid Fast Tuberculosis (TB) M. tuberculosis (MDR, XDR) M. avium - M. intracellulare complex M. bovis M. leprae Tubercle PPD Tuberculin Mycobactin Cord factor BCG Leprosy (Hansen's Disease) AIDS and TB Runyon groups Mycolic acids Diphtheria C. diphtheriae Loeffler's agar Tellurite agar Metachromatic bodies Diphtheria toxin Schick test Diphtheroids

Mycobacterium tuberculosis obligate aerobe acid-fast rods

Tuberculosis (TB, consumption) M. tuberculosis major human disease healthy people problems association with AIDS multiple drug-resistance

M. avium- M. intracellulare complex (M. avium) non-AIDS infection almost never AIDS major bacterial opportunist multiple drug-resistance

M. bovis spread from cattle infected cattle are culled positive skin test rarely seen in US

M. leprae leprosy major disease of third world rare in US

Transmission -tuberculosis M. tuberculosis causes disease healthy individuals transmitted man-man airborne droplets

Pathogenesis of tuberculosis infects lung distributed within macrophages facultative intracellular pathogen inhibits phagosome-lysosome fusion

Cell-mediated immunity -tuberculosis infiltration macrophages lymphocytes granulomas tubercules

Laboratory diagnosis - tuberculosis skin testing delayed hypersensitivity tuberculin protein purified derivative, PPD X-ray

Positive skin test -tuberculosis indicates exposure to organism does not indicate active disease

tuberculosis Other minor pathogenesis factors mycobactin siderophore cord factor damages mitochondria

Laboratory diagnosis M. tuberculosis acid fast bacteria sputum

Laboratory diagnosis M. tuberculosis (culture) grows very slowly two weeks or longer non-pigmented colonies niacin production differentiates from other mycobacteria

Tuberculosis polymerase chain amplification rapid diagnosis

Antibotic treatment - tuberculosis extensive time periods (e.g. 9 months) organism grows slowly, or dormant two or more antibiotics e.g. rifampin and isoniazid resistance minimized

Tuberculosis and Drug resistance Multiple drug resistant (MDR) resistant to first line drugs Extremely drug resistant (XDR) Resistant to some of the second line drugs Nearly un-treatable

Vaccination BCG vaccine an attenuated strain of M. bovis not effective in US, incidence is low vaccination not practiced immunization interferes with diagnosis

Mycobacterium leprae

Leprosy (Hansen's Disease) M. leprae causative agent chronic disease disfigurement rarely seen in the U.S. common in third world - effective antibiotic therapy recently initiated, incidence way down infects the skin low temperature

ulcers, resorption of bone worsened from careless use of hands (nerve damage)

Leprosy tuberculoid few organisms active cell-mediated immunity lepromatous many organisms immunosuppression

Production of M. leprae antigens and pathogenesis studies in vitro unculturable in vivo growth low temperature armadillo (laboratory and native [e.g. TX]) mouse footpad

Leprosy lepromin skin testing acid-fast stains skin biopsies clinical picture

Other mycobacterial species (including M. avium) infect immunocompromised host not transmitted man-man, healthy people M. avium – common Other species - rare

Mycobacterial diseases tuberculosis-like leprosy-like

M. avium is much less virulent than M. tuberculosis Mycobacteria and AIDS M. avium is much less virulent than M. tuberculosis does not infect healthy people infects AIDS patients M. avium infects when CD4 (helper T cell) count greatly decreased M. tuberculosis infection infects healthy people earlier stage of disease more systemic

Clinical features with AIDS systemic disease (versus pulmonary) greater in AIDS lesions often lepromatous

Antibiotic therapy selected primarily for M. tuberculosis if M. avium involved other antibiotics included

Other species pigmented or not pigmentation in the light in the dark growth fast slow

Mycobacterial species identification cellular fatty acid profiles mycolic acid profiles genetic markers

Mycolic acids mycobacteria longest chain length strongly acid fast nocardia intermediate chain length weakly acid fast corynebacteria shortest chain length not acid fast

Corynebacterium diphtheriae Gram positive strict aerobe pleomorphic (e.g. club-shaped)

Diphtheria member of normal flora of pharynx overgrowth upper respiratory tract pseudomembrane chocking bacteria do not spread systemically The toxin does disseminates .

This child has diphtheria resulting in a thick gray coating over back of throat. This coating can eventually expand down through airway and, if not treated, the child could die from suffocation CDC

Diptheria toxin spreads systemic and fatal injury

Diphtheria toxin B binds to host cell A inhibits protein synthesis ADP-ribose moiety (NADH) attaches elongation factor 2 inhibited

Treatment anti-toxin antibiotic

Immunization against diphtheria (infant) disease vanished in US without immunization will return toxoid (+ pertussis and tetanus) DPT neutralizing antibodies colonization not inhibited found in normal flora

Testing immunity Schick skin test toxin

Diphtheria toxin coded by bacteriophage tox gene not synthesized if iron present iron-repressor complex forms inhibits expression of tox gene

Identification - C. diphtheriae growth Loeffler's medium stain for polyphosphate granules metachromatic polyphosphate granules (pink) cell (blue) tellurite agar reduction by bacteria tellurium precipitation black colonies

Identification – Exotoxin production in vivo in vitro

C. diphtheriae should not be confused with: diphtheroids other corynebacteria propionibacteria