• Acid fast/not G- or G+
• non spore-forming
• non motile
• walls are rich with lipid content
• not reactive to staining with analine dyes
• straight, slightly bent rods
• mycolic acids allow it to grow in sputum

• M. bovis
• M. tuberculosis
• M. avium-intracellulare

• M. smegmatis 

• M. leprae - is associated with special growth requirements

The acid fast stain is used because the cell wall of mycobacteria are comprised of mycolic acids. These cell walls are very waxy and heat is used to soften the waxy coat. This allows the stain to enter, and then once it cools the stain is locked in, and not decolorized with the acid alcohol.

There are two methods, the Ziehel-Neelson method

-boil in acid alcohol, stain with dye, because of lipid rich cell wall it stains.

THE REAL METHOD

Carbolfuschin

acid alcohol

methylene blue-counterstain 

• slow grower
• obligate aerobe
• acid fast
• curved/bent rods
• habitat - man and primates

What is the importance of mycolic acids C78-C90?

What is the importance of Wax D?

What is the importance of Phasphatides?

• makes M. tuberculosis acid fast
• Component in Fruend's Augment, raises antigenicity, and gives a hyper immune response
• play a role in necrosis

• grows in long chains called serpentine cords
• Cord factor Trehalose dimycolate is correlated to this form of virulence. Strains without this factor are avirulent

Identification profile of M. tuberculosis

pigment

niacin

nitrate

tween 80

68 C catalse

Urease

Growth in egg based media containing 5% NaCl

• - pigment
• + niacin
• + nitrate reduction
• - tween 80
• - catalase
• + urease
• - growth in egg media + 5% NaCl

Explain what a granuloma is

what are they called in TB?

• The focal area of a granulomatous inflammation
• microscopic aggregations of macrophages that are transfomed into epithelium
• surrounded by a collar of lymphocytes and plasma cells
• in TB it is called a tubercle
• central caseous necrosis which is rare in other granulomatous diseases

Explain how a mycobacterium infection occurs.

The first step is Mycobacterium bind to CR4 on macrophages and produce....

• Cytokines are produced
• The bacterium becomes internalized in the macrophage and there is no response
• Replication occurs in the mac
• causes mac to fuse and form GIANT CELLS which leads to tissue damage
• Tubercles with thick fibrin walls form
• tubercles calcify and are visible on x-rays
• The tubercles become cheese like and liquefy, causing necrosis (very contagious) 

Caseating tubercle

• Central granular debris
• loss of cellular detail
• acid fast bacili

Non caseating tubercle

• Focus of epithelliod cells
• rimmed by fibroblasts
• lymphocytes and giant cells 

Pathogenesis of M. tuberculosis

How does it escape death?

+ 5 factors

****NO EXOTOXINS, ENDOTOXINS OR HISTOLYTIC ENZYMES****

• escapes death through macrophages and induce a delayed type of hypersensitivity
• cord factor, a surface glycolipid
• sulfatides, a surface glycopeptide that prevents activation of macrophage
• LAM, a heteropolysaccharide which inhibits macrophage and causes fever and weight loss
• heat shock protein
• cell surface antigen that prevents macrophage killing

What group of Mycobacterium does M. kansasii belong to?

What is its growth rate?

pigment produced in the light?

pigment produced in the dark?

How do colonies appear?

Niacin?

Nitrate?

Tween?

Catalase?

Urease?

Infections?

• Belongs to group 1, Photochromogens
• It is a slow grower
• + for pigment in light (yellow)
• - for pigment in dark (buff)
• colonies between fully rough and fully smooth
• Niacin - 
• Nitrate +
• Tween +
• Catalase +
• Urease +
• Infection: same drugs as TB, cough, low grade fever
• Usually infects miners, welder and painters

Name a member of Group 2 Mycobacterium

What is this group called?

Pigment in light?

Pigment in dark?

Appearance of colonies?

Growth rate?

Niacin?

Nitrate?

Tween?

Catalase?

Urease?

Infections?

• M. scrofulaceum
• Group 2 is called Scotochromogens
• pigment in light + (Yellow)
• pigment in dark + (Yellow)
• colonies are smooth, buttery in consistency 
• slow growth rate
• Niacin - 
• Nitrate - 
• Tween 80 - 
• Catalase +
• Urease +
• Infections = teeth, molars, and swollen lymph nodes in neck

M. avium-intracellulare, what group?

Growth rate?

Pigment in light?

Pigment in dark?

Colonies?

Niacin?

Nitrate?

Tween?

Catalase?

Urease?

Infection?

• Group 3, Nonphotochromogens
• Slow growth rate
• Pigment in light - (buff-yellow)
• Pigment in dark - (buff-yellow)
• 3 colonial variant, 2 smooth, 1 rough
• Niacin - 
• Nitrate -
• Tween 80 -
• catalase -
• urease -
• Infections : GI tract(localized)~nausea and diarrhea, Not localized: night seats and fever

Group 4, what organism?

Group name?

pigment in light?

pigment dark?

colonies?

Niacin?

Tween?

Nitrate?

catalase?

urease?

infection?

• M. fortuitum-chelonae
• Rapid growers
• pigment in light - (buff)
• pigment in dark - (buff)
• colonies appear smooth
• Niacin -
• tween 80 +/-
• Nitrate reduction + 
• Catalase +
• Urease +
• Infection - Ubiquitous in hospitals

TB epidemiology world wide

TB epidemiology in the US

• 50 million active cases, 8-10m new/year
• 2.5m deaths
• 30% of world has been infected,1 new infection every second
• 400,000 cases a year are drug resistant, 300,000 are extremely drug resistant
• In US
• 250,000 active cases
• 25,000/year
• 2,500 deaths/year
• resurgence in the last 10 years due to AIDS

• 1900-1980 declined
• 1985-1992 increase when federal funding of AIDS care started people from countries with TB immigrated to the US
• 1992-2002 decrease

• close contact with an infected person (airplanes)
• HIV
• IV drug users
• medical conditions that increase risk (immuno-compromised)
• prisons
• health care workers
• minorities
• young people

• Zoopf called it Bacteriu tuberculosis in 1883
• 1886 - Leehmann, Neumann changed the name to Mycobacterium tuberculosis

What is a Ghon complex?

• a calcified scar/lesion that develops in the lung and the lymph nodes it drains into are collectively called a Ghon complex.

How does a host respond to TB?

There are two types of TB, primary and secondary explain them...

• Inflammatory response in non specific and occurs within 2-3 weeks
• positive skin response
• reaction becomes granulomatuos (typical soft tubercle)
• Primary tuberculosis
• begins with inhalation of the strain and ends with T cell mediated response and hypersensitivity to the microbe
• phagocytized by macrophages and transported to lymph nodes
• macrophages cannot destroy it and it spreads through blood and into the lungs
• calcified scar develops in the lung and with the lymph nodes called Ghon complex
• Secondary tuberculosis
• Reinfected or reactive dormant disease
• occurs in lungs but spreads to kidneys, these people do not spread TB
• Caseous necrosis and cavaties rupture into blood vessels resulting in release

• Exogenous - transmission of the organism in children and adults by aerosolized droplets (droplet nuclei)
• Crowded conditions and impaired host resistance enhance spread

Lesions that occur in TB

• Exudative lesion
• Granulomatous lesion

• Weight loss
• fatigue
• low grade fever
• chronic cough
• purulent sputum
• and night sweats

• First exposure
• Early exudative response
• organisms enter the PMN leukocytes
• granulomatous response, develop tubercle
• caseous necrosis

Complications of TB

(3 major complications)

• Erosion of blood vessels
• Military tuberculosis is characterized by disseminated lesions in all organs-no CMI response
• Reactive TB seen in well oxygenated sites of the kidney, brain and bone, (usually in immuno-compromised)

• Ethnic background
• Diseases, diabetes, AIDS
• Malnutrition, stress and overcrowding

• After recovery from primary infection, cellular immunity response
• skin test
• Prior infection detected by a positive skin test PPD

• Inject intradermally 5 tuberculin units of PPD
• After 48hrs, measure diameter of induration
• >10mm indicates TB but not necessarily an active infection
• <10mm weak or doubtful 

• Rifampin - inhibits RNA synthesis
• Ethanbutol - inhibits mycolic synthesis
• Isoniazid - RNA synthesis
• Pyrazinamide

Drug resistance of TB

mortality rate?

what kind of therapy works best?

three different drug resistant strains

• 50% mortality if untreated
• resistance to isoniazid and rifampin occurs at a high frequency
• combination drug therapy works best
• W strain - multiple drug resistance, infected patients died within months
• MDR-TB - resistant to 2 or more primary drugs
• XDR-TB - resistant to isoniazid, rifampin, fluroquinolone and one of the 3 injectable drugs (kanamycin)

• Isocitrate lyase
• Antigen 85 complex

• An avirulant strain of M. bovis called BCG is used in the TB vaccine
• Enters macrophage and replicates before being killed
• given orally with no toxic side effects
• both positive and negative results

Lab diagnosis of TB

What slant?

• Prep
• Lowenstein-Jensen Slant, 37 degrees C, 3-11% CO2, NO CANDLE JAR
• coagulase whole eggs
• salt, glycerol, potato flour
• malachite green - inhibits other bacteria
• morning sputum
• acetyl cysteine- alkalin digestant - liquefies mucus
• centrifuge in capped tube - homogenize sample
• add buffer pH 6.8
• centerfuge and discard supernatant
• culture and stain

Photoreactivity

Differential test depends on whether color develops upon incubation in dark or stimulated only after exposure to light

• Scotochromogenic - dark
• Photochromogenic - light

14-21 day of exposure to light

48 hours in the dark

Accumulation

involves the conversion of free niacin to niacin ribonucleotide

reagent impregnated filter paper strips

yellow color = + test

NO3--->NO2

Red color develops upon adding reagents + test

Test detects the presence of a lipase that splits Tween 80 into oleic acid and polyoxyethylated sorbitol

Yellow to pink color change = + test

The culture is exposed to 68 degrees C for 20 minutes and then H2O2 is added 

Test before and after heat exposure

bubbling = + for catalase

Color change in urea based broth or disk

Yellow to pink = + test

Hansen's Bacillus

Organism was described by Hansen in 1879

Humans are the natural host, it affects the skin, superficial nerves, nose and ears

It is an obligate parasite of humans and armadillos

it is harbored in nasal secretions, ulcerative lesions, and sputum of patients

There are at least 3 intermediate stages

They have characteristics of both tuberculoid and lepromatous

Cases in Africa, India, Japan, Asia, FL, TX, and LA

140 cases reported to CDC each year

80,000 new cases a year

Cell mediated response is strong, limits growth, very few acid fast bacteria present

Lepromin skin test positive

exhibit large flattened patch with raised or elevated red edges

dry, pale, hairless centers on any body surface

loss of sensation on the skin due to invasion of peripheral nerves

M. leprae multiplies at the site of entry, usually the skin

invade and colonizes Schwann cells

Microbe induces T giat cell infiltration of the skin

Reactivity to lepromin

CMI develops and remains vigorous

No M. leprae recovered within lesions

Macule at the cutaneous entry and loss of pain sensation

Cell mediated response is poor, skin and mucous membranes contain large numbers of bacteria

Lepromin skin test negative

Exhibit skin involvement with thickening of looser skin parts of the lips, forehead, and ears

Classic lion face is typical

Extensive penetration of the microbe in the body may cause severe body damage resulting in the loss of bones

More severe

Microbe proliferates within the macrophages at the entry site

suppressor T cells are numerous but epitheloid and giant cells are rare or absent

CMI is impaired, large numbers of the organisms appear in the macrophages and the patients becomes insensitive to lepromin

Papules appear at the entry site with marked skin folding of the skin

Gradual destruction of cutaneous nerves leads to failure of the patient to recognize trauma

Impaired CMI status with lepromatous leprosy accounts for the severity and progressive nature of the lesions

Vigorous CMI is demonstrated in tuberculoid leprosy where lesions are localized and the microbes are rare or absent

Treatment is Dapssone and it is usually given for 2-3 years, but may be given for the lifetime

Prevent and control early detection and treatment of the patient

Specimens and direct examination

Skin lesion biopsies and nasal secretions

Demonstration of acid fast bacilli within phagocytic foam cells observed in lepromatous leprosy but difficult to detect in tuberculoid type

Can survive for years in nasal secretions, dried sputum and relatively resistant to disinfecting agents

Microscopic morphology

Acid fast, non motile, nonencapsulated rods, straight or curved, obligate intracellular parasite

Not culturable in artificial media or in tissue culture

**only mouse pads and armadillos

Antigenic structure: components not defined

Extracellular product: no virulence factor identified

MAP causes a Crohn's like gastrointestinal disease in cattle

"Johne's disease"

considered a prime suspect for the disease in humans

test whether the bacterium is transmitted to humans in the food chain

symptoms include diarrhea, weight loss, remission 

drugs that target mycobacterium help these patients

isolate is being recovered from Crohn's patients