Uncommon pathogens Flashcards
Describe the gram staining and other characteristics of Bacillus anthracis
B. anthracis is a non-motile, facultative anaerobic, Gram-positive, spore-forming bacillus (in chains)
How do humans get anthrax?
Contaminated animal products or contact with infected animals
Pathogenesis of anthrax is mediated by 2 virulence factors, namely __
Capsule
Toxin (3 parts to it)
Describe the roles of the capsule and toxin in B anthracis
Capsule is a protein capsule
Toxin has 3 parts:
Has protective antigen (polymerizes on host cell membrane and forms pore to deliver one of two factors, edema factor EF or lethal factor LF)
Edema factor: adenylyl cyclase >> increased cAMP >> fluid secretion >> edema
Lethal factor: MAPK inhibitor >> increased cytokine production >> tissue necrosis/hemorrhage/circulatory collapse (due to massive inflammatory response)
A characteristic skin feature of cutaneous anthrax is __
Black, painless, necrotic eschar (there’s also prominent surrounding edema)
**develops from entry of spores through breaks in skin
starts as small papule >> ulcer surrounded by vesicles (24-28h)**
Gastrointestinal anthrax is transmitted by __ and is characterized by GI symptoms and an __ (hint: lesion in the intestine)
Gastrointestinal anthrax is transmitted by ingestion of contaminated meat and is characterized by GI symptoms and an intestinal eschar (hint: lesion in the intestine)
*GI symptoms:fever, acute gastroenteritis, vomiting, hematemesis, bloody diarrhea*
(can progress to toxemia and death)
Inhalational anthrax results from __
The initial presentation of inhalational anthrax is characterized by __
A key feature of inhalational anthrax is __
Inhalation of spores
Initial presentation of inhalational anthrax: non specific, flu like symptoms
Later on: widened mediastinum on imaging
Terminal inhalational anthrax can progress to __ and can lead to death
Hemorrhagic mediastinitis/pleural effusion >> sepsis >> shock
Rx for anthrax
The new monoclonal antibody ___ against anthrax works against which part of the anthrax toxin?
Penicillin or Doxy
FQ (Ciprofloxacin)
or FQ + another agent
**raxibacumab (human mAb against protective antigen)
Post exposure Rx of anthrax
FQ (cipro) or Tetracycline (doxy) or Penicillin (or amoxicillin)
T/F: There is no anthrax vaccine
Falsehood. There is a vaccine: The active component is Protective antigen from filtrate of non-encapsulated strain
___ is the gram negative rod pathogen that causes Bubonic plague
Yersinia_pestis
**natural vector is rodent flea**
The pathogenesis of Y pestis is mediated by __
T3S and fibrinolysin (also capsule but that’s froma different lecture)
Key feature of bubonic plague is __
Inguinal, axillary, or cervical buboes (big, fluctuant lymph node/group of lymph nodes)
**remember the dude with the anti-flea spray in the sketchy video with the buboe in his arm pits**
Presentation of bubonic plague
Sudden onset headache, malaise, myalgia, fever, tender lymph nodes
Regional buboes
Cutaneous findings: Possible papule, vesicle, or pustule at inoculation site
How does one get pneumonic plague?
Ways to get pneumonic plague:
Bubonic plague first >> bacteremia >> pneumonia secondary to bubonic plague
Respiratory droplets from person with plague
Presentation of pneumonic plague
Sudden onset headache, malaise, fever, myalgia, cough
Pneumonia progresses rapidly to dyspnea, cyanosis, hemoptysis
Death from respiratory collapse/sepsis
Septicemic plague develops from ___
Secondary from bubonic or pneumonic forms
Rx for plague
Aminoglycosides
FQs
Tetracyclines
Sulfas
**also isolation w/ droplet precaution if pneumonic plague suspected**
Prophylaxis for plague
Literally the same meds you use to treat
Pneumonic: oral ciprofloxacin, doxycycline, or tetracycline
Bubonic: oral doxycycline, tetracycline, or TMP/SMX
Tularemia is most commonly ass’d with __ and requires a high/low infectious dose
rabbits and ticks
low dose
**no person to person tx**
Forms of tularemia
Ulceroglandular (ulcer with regional lympadenopathy)
Glandular - regional adenopathy without skin lesion
Oculoglandular - painful purulent conjunctivitis with adenopathy
Typhoidal - sepsis, no adenopathy
Pneumonic (primary or secondary)
Pneumonic tularemia presentation
Non specific pneumonia symptoms
Rx for tularemia
Rx:
Streptomycin or gentamicin
Fluoroquinolones
Tetracyclines
Prophylaxis for tularemia
Watch for a wk
Cipro or Doxy (doxy for 2 wks if + fever)
Describe the characteristics of listeria monocytogenes
Motile (at 20-28°C) Gram-positive rod
Facultative anaerobe, b-hemolytic, grows at wide temp range
Outlines the steps in Listeria pathogenesis
invasion (internalin) >> phagosome escape (listeriolysin) >> burglary (hijacks actin cytoskeleton via ActA) >> propulsion (Arp2/3 complex) >> Invasion into next cell (phospholipases)
Listeriosis can be acquired through __ transmission
Foodborne (contaminated food, unpasteurized milk etc)
2 clinical forms of listeriosis are ___
Pregnancy ass’d and non-pregaz ass’d
Presentation of Listeria in pregnancy
Undifferentiated illness: fever, chills, myalgias, bacteremia
Amnionitis: Premature labor; Septic abortion
Disseminated micro-abscesses in the neonate (granulomatosis infantisepticum) are characteristic of which type of listeriosis?
Neonatal listeriosis (happens early - acquired in utero)
Late neonatal listeriosis is characterized by __
Neonatal meningitis (remember that Listeria is high on the differential for this, after Group B Strept and H flu?)
___ is the number one cause of meningitis in an immunocompromised host
Listeria (listerial meningoencephalitis)
What do you use to treat Listeria meningitis?
Need AMPICILLIN!! 3rd generation cephalosporin does not work for this
(if not, next one is TMP-SMX)
___ is the causative agent of cat scratch disease and bacillary angiomatosis
Bartonella henselae
Describe Cat Scratch disease
What is the Rx for this disease?
Unilateral adenopathy several weeks following bite or scratch of cat
Rx: Azithromycin if needed but generally self limiting
Describe Bacillary angiomatosis and the Rx for this disease
Neovascular proliferation involving skin or internal organs seen mostly in HIV patients
Macrolides or tetracyclines
Brucellosis is caused by __ (describe the characteristics of the bug)
Brucella : Gram-negative coccobacilli
How do people get Brucella infection?
What is the presentation and Rx?
Humans infected by direct contact, contaminated milk/milk products
Presentation: Prolonged febrile illness
Rx: Tetracycline + aminoglycosides
