Mycobacteria L5 Flashcards
Patogenic are
A. M.tuberculosis complex
B. Non-Tuberculous Mycobacteria
C. Saprophytic Mycobacteria
M.tuberculosis complex
Potentially Patogenic are
M.tuberculosis complex
B. Non-Tuberculous Mycobacteria
C. Saprophytic Mycobacteria
Non-Tuberculous Mycobacteria
Non Patogenic are
M.tuberculosis complex
B. Non-Tuberculous Mycobacteria
C. Saprophytic Mycobacteria
Saprophytic Mycobacteria
Transmitted person to person (airborne, coughing of “smear-positive” people)
M. tuberculosis
What kind of MTC happens From cattle (Ingestion of contaminated milk)
M.bovis
What kind of MTC is Transmitted person to person
M. tuberculosis
Thin straight or slightly curved rods and They cannot be stained by simple stains
Tb
They can be stained by Ziehl-Neelsen stain (Z.N.) (Acid-fast bacilli (Rods)
Tb
When stained they appear as thin pink rods arranged singly or in small groups in a contrasting blue background
Tb
high lipid content (approximately 60%) of their cell wall
Tb
They can be stained by fluorochrome stains such as auramine, rodamine
Tb
Cultural characters of TB
Strictly aerobic, 5-10% CO2
The medium of TB contains
Lowenstein-Jensen (L-J) medium that contain complex nutrients (e.g., egg yolk) and dyes (e.g., Malachite green).
How fast does Tb grow
Slow growers, must be held for 6 to 8 weeks before being recorded as negative
The optimistic heat of TB is
37
Tb Cell wall Contains several complex lipids such as
Mycolic acids
Glycolipids
The proteins in TB are the antigens in the PPP used in
the tuberculin skin test
M. tuberculosis is relatively resistant to?
acids and alkalis
M. tuberculosis is resistant to ………
Dehydration
Tb survives in …… expectorated sputum
Dried
TB contains exotoxins and endotoxin in its cell wall
(T/F)
F
TB infects what in the human body?
Macrophages
Tb survives and multiplies within the ………
Phagosome
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.
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
- Change the metabolic pathway that by passes the reactions inhibited by the drug
- Produce enzymes that destroy the drug
- Alter their receptor target for the drug
- 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)
