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47 Cards in this Set

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  • Back
What are the general characteristics of the genus Mycobacterium?
Related to G+ but don't Gstain well
Acid Fast
Produce Niacin & heat-stable catalse
High GC content DNA
Thicy waxy cell wall, with mycolic acids
What are the general characteristics of Mycobacterium tuberculosis?
Cord factor in cell wall helps evade immune syst & form granulomas
Slow grower, fastidious obligate aerobe
What are non-human resevoirs for mycobacterium?
Many live in soil or water & aren't human pathogens.
M. bovis - ruminants
M. microti - voles
M. leprae - armadillos
M. tb - NONE
Which bacteria are responsible for Human TB? What is the 4th bacteria in the "TB complex" that doesn't cause human TB?
M. tb
M. bovis
M. africanum

Last one in complex: M. microti - not human TB agent
TB: How much of the world is infected? How many die per year? New Cases per year?
Which regions are most cases found?
1/3 world infected
Kills 2 million/year
Most cases in south-east Asia or sub-Saharan Africa
What vaccine is used for TB? Derived from what? Efficacy?
BCG (Gacille Calmette Guerin) vaccine from M.bovis. Different strains used for vaccine production in different countries, so efficacy widely varies (from 0-90%). Most not very effective. Not used in US
What's Miliary TB?
"Millet seeds" of tb infection spread throughout the body
How is TB transmitted?
By inhaling aerosolized microdroplets of bacteria expelled by a person with ACTIVE TB.
If the droplets are large, they won't reach the alveoli, thus will not cause infection.
Fomites do not transmit TB infection.
5 stages to TB infection:
What happens in the first 3 stages?
1) inhaled droplet with bacilli reaches alveoli
2) Bacilli grow or are killed (halting infection
3)Granuloma forms with macrophages & Tcells. May completely contain infection & calcify with age
5 stages to TB infection:
What happens in the last 2 stages?
4) If granuloma inhibit or kill bacilli, infection halted. Otherwise a caseous necrotic center devolps due to weak cell med immunity & bacilli multiply
5)Granuloma degenerates, liquifies & liquid leaks out (leaving cavity "shell"). Active, contagious TB infection
What percentage of People with close-contact exposure to TB will be infected? Of those, what percent will have Active TB?
Only 30% infected
Of those infected, only 40% will immediately have Active TB. The other 60% will be latent infection until TB is either reactivated (2-23% per lifetime) or HIV infection (then additional 5-10% chance/year)
Are children who are infected with TB contagious? Are adults?
CDC doesn't consider kids infectious due to lack of granuloma formation (different cell mediated immunity).
Adults are infectious ONLY if TB is active (cavities in lungs are leaking liquid with bacilli)
What are the risk factors for Active TB disease?
-Senescence (old age)
-Poor nutrition
-Chronic medical conditions (diabetes, CA, renal failure)
How is TB infection tested for?
(Skin Test)
PPD (purified protien derivative) skil test looks for cell-mediated immune rxn by checking size changes of the "area on induration" (site where ppd injection subcutaneously) after 72 hrs. HIV+ pts may not have immune response even with TB infection
How is TB infection tested for?
(blood test)
QuantiFERON-TB test uses whole blood to measure levels of INF-gamma (produced in response to TB antigens) Immediate results, no
How is TB infection tested for?
(Sputum test)
Sputum digested to isolate bacilli
Acid fast or auramine-rhodamine stain
Grown usually on Lowenstein-Jensen media with malachite green indicator
Usually active disease will be smear+ but neg in 10-15%
How is TB infection tested for?
Chest X-ray will show abnormalities in almost all active cases
CT more sensitive
Problem with PPD test?
False + if vaccinated with BCG or exposed to non-TB mycobacteria
False neg in 10-15% of active cases, often due to low cell mediated immune response to infection
Biased interpretation/human error
"reading" results - what is considered + changes with patient risk factors (Pt may not reveal all)
Unchanged since 1941!
How is TB Controled?
Isolation wards with HEPA filters & UV lights for active TB
6-9 months of antibiotics for active disease - many areas use Directly Observed Therapy to ensure compliance
Now after all those flashcards: what are the 3 key points to remember about TB?
1) Infections doesn't equal disease
2) Latent infection can last a lifetime without becoming active
3) BCG vaccine isn't effective
What bacteria causes Leprosy? Characteristics of the bacteria?
Mycobacterium leprae -acid-fact bacilli, obligate parasite (can't be cultured)also found in Armadillos
Grows at lower that 37 C, so affects extremities that at cooler that body temp
Describe Tuberculoid Leprosy
-Granulomas formed by strong cell meciated immunity (like in TB). If near nerve, can damage dermal & autonomic nerve fibers
-Incubation 2-5 yrs
-Not associated with skin or upper respitory tract symptoms
Describe Lepromatous/multibacillary Leprosy
-Poor or no cell mediated immunity so any granulomas formed are ineffective
-Bacilli muliply in cool ares of body & attackis skin, peripheral nerves & upper resp. tract
-Incubation 8-12 yrs
Describe Mycobacterium ulcerans
-Acid fast bacilli that causes progressive ulceration of the skin with dermal nerve damage - "buruli ulcer"
Endemic to parts of Afric & Australia in water sourves
How are MOTTs (Mycobaterium Other Than Tuberculosis) classified? Name 3 species
The Runyon classification system, by speed of growth - I-IV
(we don't have to know details of the classes)
M. avium, M. kansasii, and M. marinum (model for TB study, causes swimmer's nodule)
What is Lady Windemere syndrome?
What other populations contract the same infection?
Infection of M. avium in "little old ladies" causing pulmonary disease, adenitis and disseminated disease.

Also seen in immunocompromised pts, CA, lung disease/COPD & chronic bronchitis
Vaccine for Leprosy?
Some countries use BCG but not very effective, not used in US
Those at very high rish (long-term close contact exposure) may use prophyactic antibiotics
Describe the order Actinomycetales. Name 5 genuses within that Actinomycetales.
Most abundant bacteria in soil, many with mold-like appearance, break down organic matter

Nocardia, Streptomyces & Actinomyces were all mistaken as fungi originally
Also in this order: Mycobacterium & Corynebaterium
Describe Haemophilus influenzae
G-, pleomorphic bacili found only in Humans & spread via air
6 encapsulated (smooth) types
- Type 'b' most important (95% of H. flu infections) causing septicemia, meningitis, epiglotitis, cellulitis & arthritis
Vaccine for Haemophilus influenzae?
Composed of PRP (polyribool phosphate) from capsule congugated to protein, given in 3 doses before 6 months old.
Can H. influenzae be cultured?
Yes, only on chocolate agar (heated blood agar) or agar supplemented with X and V factors
Describe Legionella pneumophila
Fastidious G- bacilli with LPS found in water supplies & is difficult to kill. Can be aerosolized (ie dental water pik/shower)
Need cystine for growth
Causes atypical pneumonia (Legionnaires disease) from inflammation --> capillary leakage, cell lysis. Can lead to Multi-organ disease & death.
Pneumonic: The three sisters 'ella in the Cystine chapel
3 bacteria that require cystine in environment for growth:
Brucella, Legionella & Francicella
Gram negative rods that are bioterrorism concerns:
Category A pathogens: Yersinia Pestis & Francicella tularensis

Category B: Brucella & Yersinia entercolitica
Describe Yersinia Pestis
G- rod, grow on normal media, facultative anaerobe (enerobacteriaceae), safety pin shape when stained

Causes Sylvatic ("wild") and Urban plague
Describe Fransisella Tularensis
G- rod in rodent & arthropod resevoirs, in humans causes Tularemia/Rabbit Fever (can be fatal - Ulcers, "bubos" respitory disease
Describe Brucella
Genus of Zoonoses. G- rod vauses Undulant fever/MaltaFever/Brcellosis - fever & nonspecific symtoms ("flu-like")
Describe Bartonella
Genus of G- fastidious bacilli causing Trench fever & Cat Scratch Disease
Describe Bordetella Pertussis
Very fastidious G- rod found only in Humans, causing "Whooping cough" & spread through close contact/aerosols
what are the two growth factors (specifically) required for culturing of H.influenzae? where are these factors present?
X (hematin or hemin)

they are found in lysed blood, so chocolate agar is an appropriate medium.
what is the mechanism of legionella pneumophila?
it is first engulfed by a macrophage;
then it inhibits phagolysosome fusion and produces proteolytic enzymes which lyse the vacuole and kill the macrophage.
how is pneumonic plague transmitted? what is the mortality rate?
inter-human transmission. 90% mortality.
what is the function of the 'bubo' in yersinia pestis?
the organism is protected within mononuclear cells (also replicates) and upon lysis, the bacilli released are fairly resistant to phag. they cause an inflammatory response in the bubo.
which group A terrorism threat pathogen is related to "lawn-mowing" danger? how does this work?
francicella tularensis can cause 'respiratory disease' via contamination of grass with rodent urine/feces.
what sort of tissue does brucella have a predilection for? what can this lead to?
brucella has a predilection for erythritol, found in animal breast, uterus, placenta and epididymus. growth in these tissues can lead to abortion sterility or asymptomatic carriage.
describe the pathogenesis of b.pertussis.
b.pertussis attach to ciliated epithelium of the bronchial tree and multiply. it is NOT invasive, but produces an AB toxin which causes altered signal transduction.
what are the three disease stages of b.pertussis?
1. catarrhal (cold-like)
2. paroxysmal (cough)
3. convalescent (non-infectious, 2ndary complications present)