Mycobacteria L5 Flashcards by Rahaf Shook

Patogenic are
A. M.tuberculosis complex
B. Non-Tuberculous Mycobacteria
C. Saprophytic Mycobacteria

M.tuberculosis complex

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Potentially Patogenic are
M.tuberculosis complex
B. Non-Tuberculous Mycobacteria
C. Saprophytic Mycobacteria

Non-Tuberculous Mycobacteria

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Non Patogenic are
M.tuberculosis complex
B. Non-Tuberculous Mycobacteria
C. Saprophytic Mycobacteria

Saprophytic Mycobacteria

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Transmitted person to person (airborne, coughing of “smear-positive” people)

M. tuberculosis

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What kind of MTC happens From cattle (Ingestion of contaminated milk)

M.bovis

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What kind of MTC is Transmitted person to person

M. tuberculosis

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Thin straight or slightly curved rods and They cannot be stained by simple stains

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They can be stained by Ziehl-Neelsen stain (Z.N.) (Acid-fast bacilli (Rods)

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When stained they appear as thin pink rods arranged singly or in small groups in a contrasting blue background

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high lipid content (approximately 60%) of their cell wall

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They can be stained by fluorochrome stains such as auramine, rodamine

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Cultural characters of TB

Strictly aerobic, 5-10% CO2

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The medium of TB contains

Lowenstein-Jensen (L-J) medium that contain complex nutrients (e.g., egg yolk) and dyes (e.g., Malachite green).

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How fast does Tb grow

Slow growers, must be held for 6 to 8 weeks before being recorded as negative

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The optimistic heat of TB is

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Tb Cell wall Contains several complex lipids such as

Mycolic acids
Glycolipids

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The proteins in TB are the antigens in the PPP used in

the tuberculin skin test

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M. tuberculosis is relatively resistant to?

acids and alkalis

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M. tuberculosis is resistant to ………

Dehydration

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Tb survives in …… expectorated sputum

Dried

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TB contains exotoxins and endotoxin in its cell wall
(T/F)

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TB infects what in the human body?

Macrophages

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Tb survives and multiplies within the ………

Phagosome

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TB produces a protein in the phagosome that prevents ?

the phagosome from fusing with the lysosome, allowing the organism to escape the degradative
enzymes in the lysosome.

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Pathogenesis of Tb is either one of three what are they?

Primary tuberculosis Latent tuberculosis infection (LTBI) Re-infection or Activation of latent TB infection

Occurs most commonly in the lung

Primary infection

Primary infection are characterized by

a small lesion called “Primary complex”

“Primary complex” consists of 2 components?

Ghons focus (T.B. granuloma) Lymphadenitis and lymphangitis in the draining lymph node

Primary infection may also occur via the intestine with involvement of the?

mesenteric lymph node

What heals leaving the person immune and hypersensitive (i.e.) tuberculin positive

Primary lesion

Tuberculosis then became latent which may undergo what?

reactivation of an old primary lesion

Resistance to the organism is mediated by

cellular immunity

Whic patients are at much higher risk for reactivation of latent infection and disseminated, life-threatening tuberculosis. .

Patients deficient in cellular immunity, such as patients with (HIV)

Approximately 90% infections with M. tuberculosis are

asymptomatic (latent infections) can reactivate and cause symptomatic tuberculosis

Symptoms of TB

Fever, fatigue, night sweats, and weight loss are common

dysuria, hematuria, flank pain “Sterile pyuria” are all symptoms of?

Renal tuberculosis

cough and hemoptysis are all symptoms of?

Pulmonary tuberculosis

Abdominal pain ,diarrhea Intestinal obstruction or hemorrhage may occur are symptoms of?

Gastrointestinal tuberculosis

Positive tuberculin means?

exposure to organism

Tuberculin skin test Interpretation depends on?

The measurement in millimeters (mm) of the induration The person’s risk of being infected with TB and/or progression to disease if infected

Laboratory diagnosis of TB

Specimen Direct microscopic examination Culture Nucleic acid amplification tests Susceptibility tests

Culture might be either?

Traditional Automated

Radioactive metabolites are present, and growth can be detected by the production of radioactive carbon dioxide in about 2 weeks

Automated culture

Can be used to detect the presence of M. tuberculosis directly in clinical specimens

Nucleic acid amplification test

Laboratory diagnosis of TB by culture & molecular techniques is?

Susceptibility tests

In the case of Diagnosis of latent infections There are two approaches what are they?

Tuberculin skin test Interferon-γ release assay (IGRA)

In the case of which latent infection diagnosis the Blood cells from the patient are exposed to antigens from M. tuberculosis, then amount of interferon-γ released from the cells is measured.

Interferon-γ release assay (IGRA)

What is used to prevent the emergence of drug-resistant mutants during the long duration of treatment??

Multidrug therapy

Treatment for most patients with pulmonary tuberculosis is with three drugs?

Isoniazid ,rifampin, and pyrazinamide

Resistant to both isoniazid and rifampicin

Multidrug resistant

Resistant to isoniazid, rifampin, a fluoroquinolone, and at least one additional drug

Extended drug resistant TB

the failure of patients to complete the full course of therapy is a major factor in?

in allowing the resistant organisms to survive

the failure of patients to complete the full course of therapy

Noncompliance

One approach to the problem of noncompliance is

directly observed therapy

Applying proper infection control measures in hospitals. Avoid overcrowding, good ventilation ,Pasteurization of milk are all

Prevention from TB

Medical Importance of Plasmids

Drug Resistance Bacteriocin Production Virulence Plasmids Biochemical activities Plasmids encoding for protective functions to the bacterial cell

Plasmids may carry genes for bacteriocin production for example

E.coli

……… are Proteinaceous or peptidic toxins produced by bacteria to inhibit the growth of similar or closely related bacterial strain

Bacteriocins

Can carry genes that code for production of exotoxins

Virulence plasmids

Plasmids may carry genes for sugar fermentation like Galactose fermentation

Biochemical activities

Plasmids encoding for protective functions to the bacterial cell

Protection against radiation damage by radiation e,g. UV.

Are changes in the bacterial characters under the influence of the environment with no underlying genetic change

Phenotypic variations

It is reversible and not heritable

Phenotypic variations

Due to change in nucleotide sequence of the DNA by e.g. Mutation or Gene transfer

Genotypic variation

It is heritable and stable (irreversible)

Genotypic variation

This is due to change in the sequence of bases in DNA double helix

Mutation

this result in a mutant (variant) with a new character which is heritable and usually irreversible

Mutation

Gene Transfer

Transformation Transduction Conjugation

The transfer of naked DNA (released from the donor cell to the medium) to another cell recipient cell.

Transformation

Transformation may occur either …… or ……

Naturally or artificially

Steps of Transformation

Release of DNA Then Uptake of DNA

It is the process by which DNA fragment is transferred from one bacterium to another by means of a virus (bacteriophage)

Transduction

direct contact between the donor (male) cell and the recipient (female) cell

Conjugation

Conjugation leads to what?

leads to establishment of a cytoplasmic bridge between both cells, and transfer of part or whole genome to the recipient cell

The donor cell is called

F+ cell

after conjugation the donor cell remains … while the recipient cell changes from … to … cells

F+/F-/F+

Which method is one of the important mechanisms of drug resistance

Conjugation

Mechanism of F+ x F- Crosses?

Pair formation DNA transfer

Mechanisms of Drug resistance

1. Change the metabolic pathway that by passes the reactions inhibited by the drug 2. Produce enzymes that destroy the drug 3. Alter their receptor target for the drug 4. Change their permeability to the drug

Spontaneous mutation in a gene that controls susceptibility to drug

Chromosomal resistance

Plasmids carry genes control the formation of enzymes capable of destroying the drug

Extrachromosomal resistance (plasmids)