mycobacteria Flashcards by Robinson Raymundo

acid fastness property of mycobacterium is mainly due to

organism’s high content of mycolic acids, long
chained cross-linked fatty acids and other cell
wall lipids

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treatment regimen for M. tb for initial therapy

Rifampicin
Isoniazid
Pyrazinamide
ethambutol

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Routine culture uses

nonselective egg medium

Lowenstein-Jensen or Middlebrook 7H10

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Typical TB lesion

epithelioid granuloma w/ central caseation

necrosis

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Bacilli proliferate locally & spread through the

lymphatics to a hilar node, forming

Ghon complex

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4 cellular zones

1.central caseation necrosis
2. inner cellular zone of epithelioid macrophages&
Langhans giant cells admixed with lymphocytes
3. outer cellular zone of lymphocytes, plasma cells, &
immature macrophages
4.rim of fibrosis in healing lesions

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3 zones of productive lesions

Central area of large, multinucleated giant cells
containing tubercle bacilli
─ A mid zone of pale epithelioid cells, often
arranged radially
─ Peripheral zone of fibroblasts, lymphocytes and
monocytes

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consists of an acute inflammatory reaction with edema fluid, PMN leukocytes, and later monocytes around the tuberfcle bacilli

exudative lesion

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mycobacteria reide principally intracellularly where

monocytes

Reticuloendothelial cells and giant cells

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If a person has ever been exposed to the TB bacteria
(Mycobacterium tuberculosis), the skin will react to the
antigens by developing

firm red bump at the site

w/in 2 days – induration, edema, erythema

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Done by putting a small amount of TB protein (antigens)
under the top layer of skin on the inner forearm.
(intradermal)

tuberculin skin test

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disadvantage of tuberculin skin test

can’t tell how long px is infected & if infection’s latet or active

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most often site of infection of tb in the lungs

at the bae

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reactivation TB is char by

chronic tissue lesions, formation of tubercles, caseation and fibrosis

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reactivation type almost begins at the apex of the lung, why

oxygen tension is highest

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Lupus vulgaris

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Scrofuloderma

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MTA

Metastatic tuberculosis abscess

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(AMT)

Acute miliary tuberculosis

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Orificial tuberculosis (

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PIT

Primary inoculation Tuberculosis

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TVC):

Tuberculosis verrucosa cutis

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lymphadenitis or tuberculosis of bones & joints,

results in

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lymphatic spread to skin, results

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hematogenous dissemination, results in

AMT, LV, or | MTA

initial lesion due to direct infection of the skin or mucous membranes from an outside source of mycobacteria lesion

Primary-inoculation TB or Tuberculous chancre

asymptomatic, firm shallow, crust-covered ulcers w/ a | granular base

Primary-inoculation TB or Tuberculous chancre

Occurs after direct inoculation of TB into the skin in someone who has been previously infected w/ mycobacteria

Tuberculosis Verrucosa Cutis

Presents as a purplish or brownish-red warty growth Lesions most often occur on the knees, elbows, hands, feet & buttocks

Tuberculosis Verrucosa Cutis

Initial flat papule is ill-defined and soft and evolves | into well-defined, irregular plaque.

Lupus Vulgaris

``` Small sharply defined reddish-brown lesions w/ a gelatinous consistency (called apple-jelly nodules) ```

• Lupus Vulgaris

Skin lesions result from direct extension of underlying TB infection of lymph nodes, bone or joints. • Often associated w/ TB of the lungs

SCROFULDERMA

SD most often results from

continuous spread from affected lymph nodes or tuberculous bones (phalanges, sternum, ribs) or joints

Chronic TB infection that has spread from the primary infection (usually in the lungs) to other organs & tissues via the bloodstream

MILIARY TUBERCULOSIS

rare manifestation of fulminant miliary TB resulting from hematogenous spread of mycobacteria to multiple organs, including skin

Miliary TB of the skin

histological char of miliary TB of the skin

lesions show microabscesses w/tissue | necrosis & nonspecific inflammatory infiltrates

Generalized exanthem in patients w/ moderate or high degree of immunity to TB because of previous infection; usually in good health with no identifiable focus of active TB in skin or elsewhere

TUBERCULID

``` presents as recurring nodules or lumps on the back of the legs (mostly women) that may ulcerate and scar. It is a type of nodular vasculitis ```

Erythema induratum (Bazin disease)

results in crops of recurrent crusted skin papules on knees, elbows, buttocks or lower trunk that heal with scarring after about 6 weeks

Papulonecrotic tuberculid

extending eruption of small follicular papules in young | persons w/ underlying TB

Lichen scrofulosorum

Also called tuberculous gumma

METASTATIC TUBERCULOUS ABSCES

Hematogenous infection of the skin from an internal lesion may result in a large dermal or subcutaneous nodule that is necrotic & ultimately ulcerates the epidermis

METASTATIC TUBERCULOUS ABSCES

Small yellowish nodule on mucosa breaks down to form painful circular or irregular ulcer w/ undermined borders & pseudomembranous material

• Orificial Tuberculosis

Subcutaneous abscess, nontender, “cold,” fluctuant

METASTATIC TUBERCULOUS ABSCES

the standard diagnostic skin test for tuberculosis

MANTOUX TEST

The PPD contains a very small amount of tuberculosis | proteins, called

antigens.

TVC: is characterized by

massive pseudoepitheliomatous hyperplasia of epidermis and abscesses.

the infection commences as a cutaneous nodule that ulcerates down to fat & bone w/ extensive undermining of the epidermis

MYCOBACTERIUM ULCERANS

antecedent factor in M ulcerans

penetrating trauma

an infectious disease that is characterized by disfiguring | skin sores & nerve damage

LEPROSY

enzyme characteristic | of leprosy bacilli

O-diphenoloxidase

Positive lepromin skin test

TUBERCULOID

in tuberculoid TB Skin is infiltrated with

helper T cells

more severe leprosy, contagious & may be transmitted from person to person

LEPROMATOUS

Negative lepromin skin test

LEPROMATOUS

in lepromatous leproy Cell –mediated immunity is markedly deficient the skin is infiltrated with

suppressor T Cells

can be used to distinguish between tuberculoid & | lepromatous leprosy

Lepromin skin test

standard combination for the treatment of leprosy

dapsone, rifampin & | clofazimine.

Other antibiotics used to treat leprosy

ethionamide, minocycline | clarithromycin, ofloxacin

hallmark of infections with M tuberculosis

granulomas

You observe a 40-year-old man begging on a street in a town in India. He has clawing of the fourth and fifth digits with loss of distal parts of the digits of both hands, strongly suggesting leprosy. The causative agent of this disease (A) Is susceptible to isoniazid and rifampin (B) Grows in parts of the body that are cooler than 37°C (C) Can be cultured in the laboratory using Middlebrook 7H11 medium (D) Is seen in high numbers in biopsies of tuberculoid leprosy lesions (E) Commonly infects people in Texas because armadillos are hosts of Mycobacterium leprae

produce | pigment in light but not in darkness

Photochromogens

develop pigment when growing in the dark

scotochromogens

nonpigmented or have | light tan or buff-colored colonies

nonchromogens