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171 Cards in this Set

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