Mycobacteria By Eman Abdul-Aziz Mycobacteria By Eman Abdul-Aziz

*They cause 2major human disease, tuberculosis& lebrosy.Aerobic, acid fast bacilli (not stained by gram stain,why?) *The major medically important pathogens are: M. tuberculosis M. bovis (tuberculosis in human &cattle). M. africanum (tuberculosis in humans) M. lebrae (the agent of leprosy). MOTT: Mycobacteria Other Than Tuberculosis bacilli such as: M. avium-intracelullar complex &M. kanasii which cause frequently diseases in HIV infected patients. Mycobacteria:

*Acid and alcohol fast *Slender,beaded bacilli. *Non sporing. *Special stain(Ziehl-Neelsen stain). M.tuberculosis

4 obligate aerobe acid-fast rods

#Tuberculosis a chronic ganulomatous,slowly progressive infection usually of lungs, eventually many other organs and tissue may be affected. #15-20 % of individuals with HIV disease may have T.B. #The hallmark of the disease is grauloma formation caseation mediated by cellular immunity #No exotoxins or endotoxins.

 Cell-mediated immunity develops which causes infiltration of macrophages and lymphocytes with development of granulomas (tubercles).  The disease can be diagnosed by skin testing for delayed hypersensitivity with tuberculin (protein purified derivative, PPD).  A positive test does not indicate active disease; merely exposure to the organism.

8 Laboratory diagnosis - tuberculosis 1-skin testing delayed hypersensitivity delayed hypersensitivity tuberculin tuberculin protein purified derivative, PPD protein purified derivative, PPD 2-X-ray

Culture and identification: Culture and identification: #Do not grow on ordinary medium. #Requires Lowenstein – Jsnsen-Medium[whole egg,aspargine,glycerol,malachite green) #Slow growing (2-3weeks,up to 6weeks),at 37Ċ they grow as tough,rough and buff colonies. Tough ═ difficulty in lifting the colony from the surface. Rough ═ Dry and irregular growth. Buff ═ pale yellow colour.

Antibiotic sensitivity and control: *Long – term therapy (6-9 months) with (isoniazid, rifampicin, pyrazinamide, ethambutol) *Tuberculosis baclli resistant to a number of anti tuberculosis drugs. *Prevention is by B.C.G. {Bacille Calmette Guerin}, vaccination containg live attenuated m.o., pasteurization of milk.

intermediate in nocardia  The chain length of the mycolic acids is longest in mycobacteria, and shortest in corynebacteria.  This explains why mycobacteria are generally acid fast; nocardia less acid fast; and corynebacteria are non-acid fast.

M.bovis M.bovis This m.o cause cattle. Humans become infected by ingesting M.bovis contaminated milk. The m.o. specifically causes the childhood disease characterized by enlarged, caseous cervical lymphnodes. This m.o. is similar in many respects to M. tuberculosis In the laboratory it can be distinguished from the latter by its poor growth on Lowenstein – Jensen medium and ready infection in rabbits..

MOOT: Mycobacteria Other Than Tuberculosis bacilli,include: M. avium M.intracelullare M.kanasii M. fortuitum, and others.

Habitat and Transmission : Isolated from soil,water, birds & animals.

Culture and Identification: * Grow on Lowenstein _ Jensen medium but differ From pathogenic Mycobacteria in the colour of pigment produce and temp. requirements *Some species produce pigments in the dark (scotochromogens), others after exposure to light (photochromogens) and still others non chromogenic.

Pathogenicity: #Cause pulmonary infection often with M.tuberculosis Infections are especially seen in compromised individuals (e.g. H.I.V.) disease #Usually sensitive to the normal anti tuberculous drugs..

21 Mycobacterium leprae lepromatous leprosy..

M. leprae : *Humans are the only known host of M.leprae which resides mainly in the skin and nerves. *Prolonged contact is thought to be the mode of transmission. Characteristics: Aerobic acid fast bacilli No known toxins Culture and Identification: Can not be cultured in vitro but grows on footpads of mice or armadillos,yielding chronic granulomas at the inoculation site. Habitat and transmission:

Pathogenisity: #The leprosy bacilli cause also progressive chronic disease of skin and nerves. #The lesions are seen in the cooler part of the body #Two forms of leprosy are recognized. 1-Lepromatous leprosy: *T cell mediated immune response is depressed or absent. *M. leprae bacilli are usually seen in large number In the lesions and in blood ; commonly involves mucosa,especially the nose lead to much disfigurement. Achronic disease often leading to disfigurement

* Associated with an intense cell immune response to the organisms,involves the nerves, with resultant anasthesia and paraesthesia,hence damage to extremities is caused with resultant loss of fingers,toes. Antibiotic sensitivity and control: *Antileprotic drugs are Dapsone, Rifampicin & Clofazimine. *No vaccine is available *Family contacts may be given Dapsone. 2-Tuberculoid leprosy:

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

 In "tuberculoid" leprosy there are few organisms due to control by active cell- mediated immunity.  In "lepromatous" leprosy, due to immunosuppression by the organism, the opposite is found. 

27 Deformity due to nerve damage with its consequent ulcers and resorption of bone. Such deformities can be worsened by careless use of the hands. © WHO/TDR

28 Legionella pneumophila Gram negative rodGram negative rod Stains poorlyStains poorly

29 Transmission contaminated air infected water supply not spread person-person

There are 39 recognized species belong to the genus Legionella, L.pneumophila first described, they cause pneumonia...

Culture and Identification: # Dose not grow on ordinary media #Grow slowly (3weeks)in a special medium (cysteine-charcoal-yeast extract agar) under 5% Co2. #Identification is by direct immuno fluorescence.

Pathogenicity: *The portal of entry is the R.T.and infection results in Legionnaires disease (a sever form of pneumonia). *Older men who smoke and drink alcohol are typically affected, other risk factors are cancer and immunosupression. *The clinical picture is variable, ranging from mild influenza like illness to sever pneumonia with mental confusion,diarrhea, haematuria and proteinuria.

Antibiotic sensitivity and control: * Erythromycin is the drug of choice and may be combined with rifampicin or ciprofloxacin. *Protective measures include increasing chlorine con. And the temp. of hospital water supplies.