(Hopefully) High Yield Micro Flashcards
Toxin associated with pathogen that is pink on MacConkey agar and associated with recent travel
(Enterotoxigenic E coli)
Toxins = LT, ST
(LT = accumulation of cAMP; ST = accumulation of cGMP)
Attaching and effacing
Associate with EPEC (also occurs with EHEC, but that’s not the main virulence factor)
Antibiotic to use for patient with bloody diarrhea; pathogen is pink on MacConkey agar and when cultured on SMAC agar, does not fluoresce under UV light.
Do NOT use antibiotics! Can cause HUS.
EHEC does not ferment sorbitol due to lack of β-glucuronidase = no fluorescence.
“Stacked bricks” appearance
EAEC
Toxin associated with pathogen that is often acquired from contaminated hamburger
Pathogen = EHEC Toxin = STx
Pathogen that bears many similarities to Shigella spp.
EIEC:
Both cause dysentery, fever, stools with blood/pus/mucus. Both are non-motile and do not ferment lactose.
Shigella has a MUCH lower infectious dose than EIEC.
Three Gram (-) GI pathogens that use a Type III injection secretion system
Yersinia
Salmonella
Shigella
What is a major reason Shigella has such a low infectious dose?
Acid resistance - can survive the stomach
Buzzword: “ruffles” (associated with pathogenesis)
Salmonella
Which pathogen did we stress empiric antibiotic therapy for, and why?
Shigella: HUS is not more likely with antibiotic use in Shigella and individuals who are not treated can shed asymptomatically for 6 weeks
Associated with poultry and reptiles
Salmonella
Which pathogen is associated with a process that results in the formation of a “throne”?
EPEC, through the process of attaching and effacing
https://youtu.be/gnNFNI9_pT0
Association with feces from warm-blooded animals (think: dog poop)
Yersinia
Three Gram (-) curved rods
Helicobacter (more helical)
Vibrio (“comma shaped”)
Campylobacter
Association with Guillain Barre
Campylobacter
Association with shellfish
Vibrio
Treatment for H pylori
Quad or Triple therapy:
Quad: PPI + Metro + Tetra + Bismuth
Triple: PPI + Clarithromycin + (Amox or Metro)
Buzzword: “Seagull appearance”
Campylobacter
Gram (-) and Oxidase positive
Vibrio
Campylobacter
Positive string test
Vibrio
Mimics appendicitis, especially in kids
Yersinia
Associated with reactive arthritis
Yersinia
Frosted glass appearance
B cereus
Umbrella appearance on motility medium
Listeria monocytogenes
Medium used to isolate Campylobacter
Skirrow medium
Microaerophilic pathogens
Campylobacter
H pylori
Urease positive Gram (-) pathogen
H pylori
Gram + pathogen and B-hemolysis
B cereus
Listeria
Gram + bacilli with association with disease in pregnant women
Listeria (why pregnant women should avoid soft cheeses and deli meats)
Tumbling motility
Listeria
Actin rocket tails
Listeria
Treatment for Listeria
Ampicillin, with or without gentamicin
Association with rice/pasta
B cereus (emetic, heat-stable enterotoxin)
Treatment for B cereus
Usually self-limiting but if antibiotic is needed, Vanco is first choice since resistance to PCN and B-lactams is common
How is Listeria diagnosed?
Isolation from blood, CSF, or focal lesions
Association with home-canned goods
C botulinum
Association with infants + raw honey
C botulinum
Spore-forming GI pathogens
Only G + bacilli: B cereus C perfringens C botulinum C diff
Spore-forming GI pathogens
Only G + bacilli:
- Bacillus cereus
- Clostridium spp
- NOT Listeria
Associated with under-cooked pork and sweet potato
Enteritis necroticans
Difference between botulism in infants vs adults
Infants: transmitted via ingestion of spores
Adults: transmitted via ingestion of pre-formed toxin.
Toxins associated with C diff, and their actions
Exotoxin A: brush border damage, causes watery diarrhea
Exotoxin B: depolymerizes actin, leading to pseudomembranous colitis
Tx for C diff
ORAL Vanco (not IV)
Onset of symptoms after ingestion of C perfringens?
8 - 12 hours; takes time for spores to germinate and release toxin
At what stage is entamoeba histolytica infectious vs diagnosed?
Infectious: cyst
Diagnosed: cyst and trophozoite
Associated with liver abscess, RUQ pain
Entamoeba histolytica
Trophozoites with endocytosed RBCs on microscopy
Entamoeba histolytica
Drug used to clear Entamoeba cysts from the lumen
Paramycin
Buzzword: Hikers/campers drinking from stream
Giardia lamblia
Form of Giardia that is ingested
Cysts
MC parasite infection
Giardia lamblia
Buzzword: steatorrhea
Giardia lamblia; can caue vit A, D, E or K deficiency
“Falling leaf” motility
Giardia lamblia: trophozoites in stool demonstrate this motility pattern
MC organism found in AIDS patients with diarrhea
Cryptosporidium
Which portion of the GI does Cryptosporidium primarily affect?
Small intestine
Pathogen associated with perianal pruritus
Enterobius vermicularis (pinworm): female deposits eggs outside of anus at night, eggs hatch and crawl back inside
Treat with albendazole
Buzzword: bare feet
- Necator americanus and Ancylostome duodenale (New World and Old World Hookworm)
- Strongyloides stercoralis (threadworm)
What will be present in a stool sample positive for Strongyloides stercoralis?
Larvae, not eggs!
Eggs are laid into GI wall; larvae emerge and can pass into stool
Treatment for Strongyloides stercoralis
Ivermectin
Hosts associated with Taenia spp
Intermediate hosts:
Taenia saginata = cattle
Taenia solium = pigs
Definitive hosts = humans
Cysticercosis vs Taeniasis
Taeniasis = ingesting the eggs of taenia spp. Causes GI problems.
Cysticercosis = ingesting cysts of taenia; can affect any tissue of the body (including brain)
Treatment for cestode infections
Praziquantel
Pathogen associated with contaminated fish
Diphyllobothrium latum (Tapeworm) - transmitted via ingestion of fish containing pleorcercoid larvae
Hepatitis for which we have vaccines
A and B
ssRNA + hepatitis viruses
HAV (picornavirus); HCV (flavivirus) and HEV (hepevirus)
