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171 Cards in this Set
- Front
- Back
What are 7 possible consequences of Staphylococcal infections?
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-Respiratory infection
-Food poisoning -Toxic shock syndrome -Wound infection -Impetigo -Focal skin infections -Endocarditis |
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When does a staph-induced respiratory infection usually arise?
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Secondary to influenza
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What is the predominant staph species that is normal flora on the skin?
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Staph epidermidis
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What is the major staph species that causes wound infections?
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Staph aureus
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What is the difference between impetigo and carbuncles/furuncles/abscesses?
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Impetigo = diffuse
Carbs/furuncs/abcess = focal |
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What is an abcess characterized by?
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Presence of PMNs
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What are carbuncles and furuncles?
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Carbuncles = whiteheads
Furuncles = big whiteheads |
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What is endocarditis?
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Infection of heart valves with bacteria
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What does bacterial endocarditis have the potential for?
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Diffuse systemic sepsis when the infected pus covered valve breaks off and travels into the circulation.
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How fast is projectile vomiting caused by Staph aureus food poisoning usually seen? Why?
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Very quickly due to preformed toxin.
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Why is staph aureus commonly seen as the agent causing infections of severe burns and surgical wounds?
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Because of nosocomial transfer.
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What type of infections does Staph epidermidis typically cause?
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Opportunistic infections in:
-Catheterized patients -Prosthetic heart valves -IV Drug users |
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What exactly is a Furuncle?
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A focal suppuration on the skin; a boil
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How is a Carbuncle different from a furuncle?
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It has DEEPER suppuration that spreads laterally beneath deep subcutaneous fascia.
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What are 6 diseases caused by Strep Group A?
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GRIPES
-Glomerulonephritis -Rheumatic fever -Impetigo -Pharyngitis -Erysipelas -Scarlet fever |
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What do Rheumatic fever and glomerulonephritis represent?
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The post-strep sequelae that results from untreated infections.
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What are 2 diseases caused by Strep group B?
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-Neonatal sepsis
-UTI |
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What are 2 diseases caused by Strep group D?
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-Endocarditis
-UTI |
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What can Strep viridans cause? Where is it commonly seen?
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Endocarditis (normal flora in the mouth)
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What are 2 diseases caused by Strep pneumoniae?
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-Community acquired pneumonia
-Bacterial meningitis |
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What does Strep mutans cause?
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Dental caries
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What are the toxins on Strep group A that cause Erysipelas?
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Exotoxins A and C
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What is erysipelas?
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A rapidly spreading cutaneous red swelling that resembles a butterfly rash
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What organisms can cause impetigo?
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Staph or strep A
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What is Impetigo?
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-A superficial skin infection
-if seen its mostly on infants -spreads over trunk and body -infectious |
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What is Listeria monocytogenes associated with?
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-Severe food-borne illness
-Neonatal meningitis |
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What foods does Listeria monocytogenes get transmitted in?
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Hotdogs, chicken, and cheese
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What can Listeria cause in pregnant women?
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Chorioamnionitis
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What type of morphology is listeria?
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Gram pos bacilli
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What will be seen in neonatal meningitis caused by listeria monocytogenes? Catalase?
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Intracellular GPB within neutrophils in CSF
-Catalase pos |
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What are the distinguishing characteristics of Nocardia?
-gram stain -respiration |
Gram Pos branching chains
-Aerobic |
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In what patients will nocardia infections be seen?
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-Immunocompromised (on steroids or have HIV, or poorly controlled diabetes)
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Where is Nocardia normally found?
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In soil
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What species of nocardia causes resp infections?
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Nocardia asteroids
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What is the respiratory infection presentation of N. asteroids similar to?
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TB
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What happens to 20% of N. asteroids resp infections?
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Dissemination to the brain
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What is the morphology of Neisseria gonorrhoeae?
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-Gram neg diplococcus (lancet)
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What are 4 diseases caused by N. gonorrhoeae?
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-Urethritis
-Pharyngitis -Proctitis -PID |
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What can septic dissemination of gonorrhoeae cause?
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Gonococcal arthritis and dermatitis
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What is the characteristic presentation of GC in males?
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-Nonpainful white discharge
-Intracellular GNdC on direct smear |
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Are intracellular GNdC from a female direct smear sufficient to diagnose gonorrhoeae?
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NO - there are other gram neg cocci that can be normal flora in females.
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What additional steps have to be taken to diagnose gonorrhoeae in females?
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Specific testing in the lab.
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What is the morphology of Pseudomonas aeruginosa?
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Anaerobic gram neg bacillus
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In what 3 cases is Pseudomonas aeruginosa deadly as a pathogen?
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-Cystic fibrosis
-Severe burn patients -Neutropenia (immunosuppressed) |
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What is P. aeruginosa a major cause of?
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Nosocomial infection
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What are the 3 most common bacteria associated with nosocomial infections?
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-P. aeruginosa
-Staph aureus -E. coli |
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What type of pathology morphology is seen in P. aeruginosa infections?
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Necrotizing inflammation (ischemic necrosis)
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What does P. aeruginosa cause in contact lens wearers?
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Corneal keratitis
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How does P. aeruginosa get into hospitals in the first place?
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Often on lettuce leaves
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What is the causative agent of the plague?
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Yersinia pestis
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What is the morphology of Yersinia pestis?
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Gram neg bacillus
facultative intracellular |
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How is Yersinia pestis transmitted?
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By flea bites or aerosols
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What are the symptoms associated with plague?
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-Lymph node enlargment
-bubos -Pneumonia -Sepsis w/ marked neutrophilia |
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What is a common site of bubos in plague infections?
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Inguinal
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What is the causative agent of Chancroid?
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Haemophilus ducreyi
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Why is it called chancroid?
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Because it causes chancres similar to those in syphilis.
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What type of chancres are seen in chancroid?
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Soft chancres
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How are the chancres in chancroid different from syphilitic chancres?
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They are PAINFUL
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What is the gram stain morphology of haemophilus ducreyi?
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Gram neg coccobacilli - school of fish distribution.
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What are the 2 very uncommon STDs?
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-Chancroid (h. ducreyi)
-Granuloma inguinale |
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What is the causative agent of Granuloma inguinale?
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Calymmatobacterium donovani
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What are the characteristic intracellular inclusion bodies in Granuloma inguinale?
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Donovan bodies
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What is the usual manifestation of granuloma inguinale?
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Genital lesions which are indolent, progressive, ulcerative, and granulomatous.
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How many important STD causing agents are there?
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16 (see additional cardset)
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Where are anaerobes normal flora?
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In sites with low oxygen
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What 2 types of infections do anaerobes typically cause?
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Abscesses or peritonitis
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Do anaerobes typically only contain one type of bacteria?
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No, they usually contain mixed flora including normal anaerobic flora.
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What are the characteristic features of abscess pus?
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-Discolored
-Very foul smell |
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What is the causative agent of Anaerobic cellulitis and what are 2 other names for this?
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Agent: Clostridium perfringens
Aka, Myonecrosis or Gas Gangrene |
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What types of sites normally see gas gangrene develop?
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Traumatic wounds
Surgical wounds |
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What is the gram stain morphology of C. perfringens?
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Gram pos bacilli (box car)
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What is the causative agent of Pseudomembranous colitis?
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Clostridium difficile
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Where does pseudomembranous colitis form?
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In the GI tract
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What is another name for Pseudomembranous colitis?
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Antibiotic-associated colitis
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Why is C. diff so good at being spread nosocomially from patient to subsequent patient?
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Because it is a spore former and the spores can survive in between patients.
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What type of toxin is formed by Clostridium tetani, and what disease results?
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-Neurotoxin
-Tetani - lockjaw |
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Where is C. tetani normally found and how does it get into the body?
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In dirt and nails - via puncture wounds.
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What is the characteristic site that harbors Clostridium botulinum?
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Canned foods (like honey)
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What type of toxin is formed by C. botulinum, and what disease results?
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-Neurotoxin
-Paralysis - Botulism |
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What is the most pathogenic acid fast bacillus?
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Mycobacterium tuberculosis
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How much of the world population is infected by TB? How many deaths result annually?
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1/3
-3 million deaths annually |
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What is the dominant method of transmission for TB?
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Aerosol/coughing
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What are the 2 leading causes of infectious death in the world?
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1. HIV
2. TB |
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How bad is a primary Mycobacterium tuberculosis infection?
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Not all that bad - it may be asymptomatic, or just cause a fever and cough.
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When does TB become a life-threatening disease?
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When the immune system is suppressed.
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What does infection with M. tuberculosis lead to?
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Delayed type hypersensitivity to M. tuberculosis antigens.
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What test detects DTH to TB?
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the Mantoux tuberculin test
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When after primary M. tuberculosis infection will the mantoux test be positive?
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2-4 weeks
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What are the 2 pathological manifestations of TB infection?
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-Caseating granulomas
-Cavitation |
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What are the primary cells infected by mycobacterium tuberculosis?
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Macrophages
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How do the bacilli replicate during the course of TB infection?
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Early: replication is unchecked
Later: Thelper response contains it |
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How does M. tuberculosis get into macrophages?
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Via endocytosis mediated by mannose receptors (TLR) and complement receptors.
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How is M. tuberculosis able to survive and replicate inside macrophages?
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By preventing fusion of the phagosome and lysosome.
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Where are the macrophages in which TB replicates early in infection?
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In alveolar macrophages.
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In what patients will TB progress from early proliferation without developing an immune response?
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Those that have polymorphisms in NRAMP-1
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What is NRAMP-1?
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The gene that encodes a Calcium pump for lysosomes that is important for making ROS to kill intracellular bacteria.
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What happens when patients lack NRAMP-1?
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They progress directly into the miliary form of TB.
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When after infection does the Th1 response get mounted? What is the result?
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3 weeks; Macrophages become bactericidal.
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What stimulates the Th1 cells?
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Ag presentation of TB antigens in lymph nodes by APC's MHCII
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What cytokine induces Th1 cells to differentiate?
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IL12
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What is the critical mediator that drives macrophages to become competent to contain the TB infection?
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IFN-y
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2 principle changes in macrophages in response to IFNy:
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-Phagolysosome formation
-iNOS expression |
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Other than activating macrophages, what does the Th1 response drive?
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Formation of
-Granulomas -Caseous necrosis |
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What cells charactize the granulomatous response, and what recruits them?
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-Monocytes which differentiate into EPITHELIOID HISTIOCYTES
-Recruited by TNF from activated macrophages |
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What is the result of epithelioid histiocyte recruitment in normal healthy individuals?
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Containment of the TB infection, no significant tissue destruction or illness.
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What is the result of epithelioid histiocyte recruitment in immunosuppressed individuals?
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-Progression of infection
-Caseation and cavitation -Tissue destruction |
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What happens in patients with rheumatoid arthritis who are given a TNF antagonist?
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They don't get monocyte recruitment so are susceptible to tuberculosis reactivation.
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Why is it bad to test neg for TB when a skin test was previously positive?
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Because it's a sign that immune resistance has faded.
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What is Secondary tuberculosis?
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The result of reactivation or reinfection in a previously sensitized host.
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Where is the classic localization of 2ndary pulmonary TB? why?
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In the apex of the upper lobe of one or both lungs; the higher O2 tension may be better for the bugs there.
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What does the rapid and marked response of cells to secondary infection result in?
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-Less regional LN involvement
-More cavitation |
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Why is cavitation bad?
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It results in more dissemination of mycobacteria along the airway and coughing and erosion of the airways creating aerosols.
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What are some clinical manifestations of localized secondary TB infection?
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-Chronic low grade fever
-Night sweats |
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What is becoming an increased problem with TB?
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Multi-drug resistance
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When is the prognosis good for TB infection?
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When infection is localized to the lungs
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At what stage of HIV infection are patients at increased risk of TB infection?
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All stages
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What will be the presentation of TB infection in an HIV patient with Tcell count >300 cells/mm?
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Like 2ndary TB - apical disease with cavitation.
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What will be the presentation of TB infection in an HIV patient with Tcell count >200 cells/mm?
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Primary TB - lower/middle lobe consolidation, hilar lymphadenopathy, noncavitation.
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What is a Ghon focus?
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A single subpleural nodule that is asymptomatic
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What occurs at the middle of a Ghon focus?
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Caseous necrosis
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What often happens to the lymph nodes where tubercle bacilli drain?
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More caseous necrosis
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What is the Ghon focus plus involved lymph nodes called?
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Ghon complex
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What is the outcome of MOST (95%) cases of primary TB?
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It does not progress
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What are signs of contained primary TB?
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-Progressive fibrosis of the Ghon complex
-Ranke complex (radiology detects calcification) |
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What would a lack of granulomas, but instead sheets of foamy histiocytes packed with AFB mycobacteria make you suspect?
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Infection in an immune suppressed individual.
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What is miliary tuberculosis?
In whom does it occur? |
-Uncontrolled dissemination of a primary focus
-elderly and immunocompromised |
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How does miliary pulmonary disease develop?
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When M. tuberulosis spreads to lymph nodes, the lymphatic duct, the right heart, then pulmonary vessels.
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When does miliary pulmonary disease become Systemic miliary tuberculosis?
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When infective foci in the lungs seed the pulmonary venous return to the heart.
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What disease does mycobacterium AVIUM intracellulare complex cause?
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Disease that resembles TB in AIDS patients, except WITHOUT granulomas.
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What is the hallmark of mycobacterium avium intracellular complex infections? Why?
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-ABUNDANT AFB w/in macrophages -Due to lack of proliferation control
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What causes Hansen's disease?
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Mycobacterium leprae
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What does M. leprae affect?
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-Skin
-Peripheral nerves |
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How is M. leprae transmitted?
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By aerosols
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Can M. leprae be cultured in the lab?
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No but it can be in an armadillo footpad.
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What are the 2 forms of leprosy?
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-Lepromatous
-Tuberculoid |
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Which form is less severe?
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Tuberculoid
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What are the characteristic lesions in Tuberculoid leprosy?
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Dry, scaly skin lesions that lack sensation and have assymetric nerve involvement.
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What are the characteristic lesions in Lepromatous leprosy?
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Raised, symmetric skin thickening with nodules.
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Why is lepromatous leprosy called the anergic form?
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Because there is no host immune response.
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What parts of the skin are mostly affected?
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Cooler - the face and hands.
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Why is the Tuberculoid form better?
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Because well-formed granulomas develop which limit the bacterial dissemination.
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What is the gram stain morphology of Spirochetes?
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Gram neg corkscrew shaped bugs
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What are the 3 spirochetes and what disease does each cause?
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T. pallidum - syphilis
Borrelia recurrentis - relapsing fever Borrelia burgdorferi - Lyme disease |
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How is T. pallidum identified with microscopy? (3 ways)
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-Silver stains
-Darkfield examination -Immunofluorescence |
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How many stages does Syphilis occur in?
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Three:
Primary Secondary Tertiary |
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What is the pathology of primary syhphilis?
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Chancre
|
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What is the pathology of secondary syphilis?
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Palmar/solar rash
Lymphadenopathy Condyloma latum |
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What is condyloma latum?
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A raised red-brown plaque on the penis or vulva
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What are the 3 pathologic manifestations of Tertiary syphilis?
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-Neurosyphilis
-Aortitis -Gummas |
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What are the 2 manifestations of Neurosyphilis?
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-Meningovascular Tabes dorsalis
-General paresis |
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What are the 2 manifestations of Aortitis in tertiary syphilis?
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-Aneurysms
-Aortic regurgitation |
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What are the 2 manifestations of Gummas in tertiary syphilis?
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-Hepar lobatum
-Skin, bone, others |
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When after initial contact with an infected individual will primary syphilis occur?
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3 weeks after
|
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When does 2ndary syphilis occur?
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2-10 weeks after the primary chancre
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When does Tertiary syphilis occur?
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Usually after a latent period of 5 years of more
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At what stage of syphilis are AFB isolatable?
|
Only during primary from a chancre.
|
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What are 3 types of childhood syphilis manifestations?
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-Late abortion/stillbirth
-Infantile -Childhood |
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What are 3 agents that can cause rashes on the palms and soles?
|
-Syphilis
-RMSF -Smallpox |
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When is congenital syphilis most severe?
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When mother's infection is recent
|
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When do Treponemes invade the placenta or fetus?
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Not until the 5th month
|
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What is the late-occuring congenital syphilis triad?
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-Interstitial keratitis (blind)
-Notched incisors -8th nerve deafness |
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What are the nonspecific screening tests for syphilis?
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-RPR
-VDRL |
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What is the basis of the RPR and VDRL tests?
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-Cardiolipin detection in T. pallidum but also host tissue
|
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What do you do if the RPR or VDRL is positive?
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Specific treponemal testing via FTA-Abs and Microhemagglutination assay
|
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What agent causes relapsing fever?
|
Borrelia recurrentis
|
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How is borrelia transmitted?
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Via person-person spread of body lice and ticks
|
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Why do relapses occur in Relapsing fever?
|
Because after antibodies clear the initial infection, antigenic variation results in new serotypes causing similar symptoms.
|
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What is the Jarisch Herxheimer reaction?
|
An antibiotic reaction seen in some patients that leads to the massive release of endotoxin.
|
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How is Lyme disease transmitted?
|
By deerticks infected with the bacterium B. burgdorferi
|
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What are actually three bacteria deerticks can transmit?
|
-Borrelia
-Babesia -Ehrlichia |
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What are the 3 stages of lyme disease?
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-Acute (within weeks)
-Dissemination (weeks-months) -Late chronic form |