Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
52 Cards in this Set
- Front
- Back
|
C. diphtheriae is a?
|
Gram positive, pleomorphic, non-spore forming aerobic rod
|
|
|
What is the characteristic symptom of C. diphtheriae disease?
|
Grayish membrane in throat, that may extend to the lung. Called a "pseudomembrane", it adheres strongly to the tissues and **should not be removed physically**
|
|
|
Systemic and fatal injury in C. diphtheriae infection results from what?
|
The diphtheriae toxin
|
|
|
What are the three types of bacterial toxins?
|
Type I - Binds to host cell surface (superantigens)
Type II - Acts on cell membrane (phospholipase, pore forming cytotoxin) Type III - A-B toxins |
|
|
How does an A-B toxin work?
|
B subunit binds to something on cell surface, inducing phagocytosis.
A subunit translocates through membrane of phagocytic vesicle into cytoplasm, where it acts. |
|
|
How does the diphtheriae toxin work?
|
It catalyzes the covalent attachment of the ADP-ribose moiety of NADH to the rare AA, diphthamide, present in EF2
The result is it interferes with EF2 and prevents protein synthesis |
|
|
What are the limiting factors of the diphtheeria toxin?
|
The toxin gene is encoded by a bacteriophage as a single polypeptide chain. Any bacteria not infected with the phage DO NOT CAUSE DIPHTHERIA.
There is a gene that codes for dtxR, a diphtheria toxin repressor protein. In the presence of Iron, the repressor binds to the tox gene promoter, suppressing transcription of the diphtheria toxin. |
|
|
How is expression of the diphtheria toxin controlled?
|
There is a gene that codes for dtxR, a diphtheria toxin repressor protein. In the presence of Iron, the repressor binds to the tox gene promoter, suppressing transcription of the diphtheria toxin.
|
|
|
What does the diphtheria toxin bind to on the host cell?
|
The HB-EGF receptor
|
|
|
What is the treatment for diphtheria infection?
|
Rapid therapy with anti-toxin, along with antibiotics. Penicillin or Erythromycin.
|
|
|
What is the prevalence of diphtheria disease?
|
It is almost non-existent in the US and other developed countries, due to immunization.
3rd world countries it is a major cause of death in children. |
|
|
How are C. diphtheriae identified in culture?
|
They are grown on Loeffler's medium, followed by staining for metachromatic bodies (polyphosphate granules, Babes-Ernst bodies)
Metachromatic refers to the color difference of the intracellular polyphosphate granules (pink) compared to the rest of the cell (blue) |
|
|
Black colonies seen on tellurite agar with the microscopic "chinese letter arrangement" is characteristic of what organism?
|
Corynebacteria Diphtheriae
|
|
|
What is the most virulent strain of H. influenzae
|
Haemophilus influenzae
Type b, the encapsulated strain is the most virulent |
|
|
What causes the STD chancroids?
|
Haemophilus ducreyi
|
|
|
What disease is H. influenzae aegyptius cause?
|
Conjunctivitis
|
|
|
Grows on chocolate agar, supplemented with hemin (factor X) and Factor V, with 5% CO2 is?
|
Haemophilus influenzae
|
|
|
What disease used to be associated with H. influenzae?
|
Meningitis in children between 6 months and 5 years, although now disappeared thanks to vaccine.
|
|
|
What is diagnosis of H. influenzae disease based on?
|
History, physical examination and symptoms.
In meningitis, gram negative coccobacilli found in CSF of more then 80% of cases |
|
|
What is the mortality of H. influenzae-b disease?
|
Meningitis and epiglotitis are almost 100% fatal
|
|
|
What is the treatment for H. influenzae meningitis?
|
Cephalosporin, as it penetrates the blood brain barrier
|
|
|
What does H. aegyptius cause?
|
Pediatric disease known as Brazilian Purpuric Fever. Starts with conjunctivitis, fever, vomiting, abdominal pain, and can lead to death.
|
|
|
What is the treatment for H. ducreyi and H. influenzae aegyptius?
|
Erythromycin
|
|
|
Gram negative, aerobic, motile with 2 or more polar flagella is?
|
Legionella
|
|
|
What diseases does Legionella cause?
|
Legionnaires Disease - A pneumoniae which attacks 2-5% of those exposed.
Pontiac Fever - Fever and myalgia, but no pneumonia |
|
|
What is the mortality rate of Legionella?
|
About 5-15% of those who contract Legionella die from it
|
|
|
How does Legionella spread?
|
The organism is spread through contaminated air, most often growing in hot water towers and air conditioning systems.
There is NO person to person spread. This is the only bacterial agent whose presence is a major concern to indoor air quality. |
|
|
How is Legionalla prevented or cleared when it is detected in a building?
|
Cleaning of the water supply by Chlorination.
|
|
|
How does Legionella grow and survive?
|
Legionally pneumophila proliferates inside of protozoa.
In the human host, it also survives as an intracellular pathogen. |
|
|
How does Legionalla reproduce?
|
Macrophage lysis is a two-staged process: apoptosis and cytolysins-mediated lysins
It is taken up into a phagosome by a MACROPHAGE, but Legionalla stops the fusion with lysosome so it does not become acidified. The phagosome is then surrounded by ER with ribosomes attached, and Legionalla replicates inside. When numbers are sufficiently large, the phagosome ruptures and the Legionalla lyses the cell. |
|
|
How does Legionally regulate virulence?
|
In a low AA concentration, it activates RelA. This increases concentrations of ppGpp, which activates virulence genes such as:
Flagella Type IV Secretion System Lysis of Host Cell This process is activated when Legionalla has "exhausted" the host cell. |
|
|
How is L. pneumonphilae culture?
|
On medium which contains iron and cysteine. It stains poorly as a gram negative rod, so PCR or serology are useful.
|
|
|
What is the treatment for L. pneumophilae?
|
Erythromycin is the drug of choice, but antibiotics have trouble reaching intracellular bacteria.
|
|
|
What are the optimal growth conditions for L. pneumophila?
|
Water temp between 35-46 C, although capable of growing in water between 20-50 C.
Stagnant water, with wide pH range (2.0-8.5) Sediment in water to support growth of supporting microbiota |
|
|
What is the drug of choice for Pertussis?
|
Erythromycin
|
|
|
What causes whooping cough?
|
Bordetella pertussis
|
|
|
What are the three stages of whooping cough?
|
Catarrhal stage - 1-2 weeks
Paroxysmal Cough stage - 1-6 weeks Convalescence - weeks to months |
|
|
Gram negative, coccobacillus, strictly aerobic, Oxidase positive, non-motile in human but has genetic potential for flagella is?
|
Bordatella pertussis
|
|
|
What are the virulence factors of pertussis?
|
LPS, Pertussis toxin, ACase toxin, Dermonecrotic toxin
|
|
|
Obligate aerobe, slow growing, acid-fast rods are?
|
Mycobacterium tuberculosis, avium complex, intracellulare complex
|
|
|
Where to M. tuberculae replicate?
|
Inside alveolar macrophages
|
|
|
What is the reactivation rate of TB?
|
5% in the first 2 years following primary infection. 5% more for rest of life.
|
|
|
What features are unique to TB?
|
Mycolic acids - extremely long chain (mycobacteria, nocardia, cornebacteria)
Cord factor - aggregation of bacteria Wax D - extraction of cell wall |
|
|
How do you stain TB?
|
Acid-fast stain, exhibit banding and beading
|
|
|
What do you use for early diagnosis of TB infection?
|
Acid-fast staining of sample.
Still need culture, but that can take weeks |
|
|
What does the immune response target in leprosy?
|
Peripheral nerves
|
|
|
What are the types of Leprosy?
|
Tuberculoid type - few bacteria, non-infective. Mild, self-limiting disease. Active cellular immunity
Lepromateous type - Little inflammatory response, mucus highly contaminated. Compromised cellular immunity |
|
|
What are the treatments for the 2 types of Leprosy?
|
Tuberculoid - Dapson and Rifampin for 6 months
Lepromateous - Dapson, Rifampin and Clofazimine for 2 years |
|
|
What is the treatment of endocarditis of unknown cause?
|
If organism not known:
Ampicillin (every 4 hours) Gentamycin (every 8 hours) If organism known: Regimen based on ID of pathogen If antibiotic therapy doesn't work, or if fugnal, surgical removal of infected endocardium may be necessary |
|
|
How does endocarditis cause damage?
|
Tiny clots form in turbulent areas of the abnormal heart, trapping microorganisms in an environment that protects them from the immune response. They grow EXTREMELY SLOWLY in this environment, making them relatively resistant to antibiotics.
|
|
|
Why are endocarditis causing bugs resistant to antibiotics?
|
As they are trapped in micro-clots, they grow very slowly. The induced slow metabolism makes them relatively resistant to antibiotics.
|
|
|
What are the ways to estimate bacterial death rates?
|
TDP - Thermal Death Point - temperature at which all microorganisms in a liquid suspension will be dead after 10 minutes
TDT - Thermal Death Time - Minimum time for all bacteria in liquid suspension to be killed at a given temperature D or DRT - Decimal Reduction Time - Time at which 90% of the bacterial population will be killed at a given temperature |
