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82 Cards in this Set
- Front
- Back
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what is the morphology of staph aureus?
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gram + cocci in clusters
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what is staph aureus positive for? (2)
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coagulase
catalase |
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is staph aureus motile?
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no
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can staph aureus form spores?
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no
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what are 3 ways to culture staph aureus?
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sheeps blood (beta-hemolytic)
mannitol salt PEA |
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what is the clinical presentation of staph aureus food poisoning?
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abrupt, violent onset of severe nausea, cramps, vomiting, and diarrhea
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what is a complication of staph aureus?
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can lead to severe metabolic alkalosis
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what are 2 toxins of staph aureus?
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A and B enterotoxins
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how is staph aureus transmitted?
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food-handler who is a carrier contaminates food
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what are 4 foods commonly contaminated with staph aureus?
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processed meats
custard-filled pies potato salad ice cream |
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what is the morphology of clostridium perfringes?
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gram+
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can clostridium perfringes form spores?
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yes
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how does clostridium perfringes respire?
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aerotolerant
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what does clostridium perfringes grow on?
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egg-yolk agar
precipitation forms around colonies to indicate lecithinase activity |
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what will clostridium perfringes do on blood agar?
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beta-hemolysis
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where does clostridium perfringes exert its maximum effect?
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ileum
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where does clostridium perfringes exert its minimum effect?
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duodenum
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where can clostridium perfringes be found?
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in the intestinal flora of humans, animals, and soil
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how is clostridium perfringes transmitted?
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ingestion of food contaminated with dirt or feces
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what food are associated with clostridium perfringes?
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meat or poultry dish to be precooked, then reheated
roasted, steamed, or boiled beef, turkey, or chicken |
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what is unique about clostridium perfringes?
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commonly found in bullk (40-50 people/outbreak)
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what type of clostridium perfringes culture produces a more powerful disease?
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older cultures
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what is enteritis necroticans?
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clostridium perfringes type C
first found in WWII |
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what type of food is enteritis necroticans associated with?
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pork
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what is the course of enteritis necroticans?
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severe necrotixing disease of the small intestine
mortality rate about 40% due to intestinal perforation |
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what is the morphology of clostridium botulinum?
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gram + rod
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does clostridium botulinum form spores?
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yes
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how does clostridium botulinum respire?
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anaerobe
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how does clostridium botulinum cause damage?
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potent preformed toxin
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how does the clostridium botulinum toxin work?
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attaches to the NMJ of affected nerves
prevents release of Ach leading to flaccid paralysis |
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what is clostridium botulinum associated with?
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home canning of asparagus, green beans, peppers
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what is the most predominant toxin in clostridium botulinum?
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type A toxin
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how does clostridium botulinum type A toxin work?
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toxin enters the blood stream once it is absorbed from the stomach and small intestines (toxin is not degraded by digestive enzymes)
binds to receptors of presynaptic terminals of cholinergic synapses |
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what is clostridium botulinum toxic effects limited to?
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peripheral nerves
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how will clostridium botulinum present? (2)
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descending, symmetric, flaccid paralysis
n/v/d |
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how do you treat clostridium botulinum and what are the limitations?
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ABE antitoxin will slow the progression but will not neutralize toxin that is already bound
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what is the pathogenesis of the diarrheal form of bacillus cereus?
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mediated by an enterotoxin that activates adenylate cyclase in intestinal cells (similar to e. coli and cholera)
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how long is the incubation period with the diarrheal form of bacillus cereus?
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9 hours
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what 3 foods are associated with the diarrheal form of bacillus cereus?
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spagetti sauces
dried potatoes dried milk |
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what does the emetic form of bacillus cereus not do?
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does not activated adenylate cyclase so there is no net secretion of fluid and electolytes
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what food is associated with the emetic form of bacillus cereus? why?
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fried rice
if cooked rice is not refrigerated, spores germinate and releases heat-stable enterotoxin which will not be destroyed when the rice is reheated |
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what is a complication of the emetic form of bacillus cereus?
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ingestion of large amounts could result in liver failure
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what is key about the emetic form of bacillus cereus?
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heat-stable, proteolysis resistant enterotoxin
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what is key about the diarrheal form of bacillus cereus?
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heat-labile enterotoxin
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what is the morphology of bacillus cereus?
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gram + rod
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is bacillus cereus motile?
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yes
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is bacillus cereus beta-hemolytic?
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yes
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how can you isolate bacillus cereus?
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in the food or from a cluster of patients exhibiting the same symptoms
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what form of cryptosporidium parvum is infective?
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oocysts
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how can cryptosporidium parvum autoinfect?
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rupture of thin-walled oocysts in the intestines
patients can remain infective even after diarrhea ceases because they continue to shed thick-walled oocysts |
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what are 5 symptoms of cryptosporidium parvum in the immunocompetent?
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frequent, watery diarrhea
N/V abdominal cramps low-grade fever self-limiting |
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what are 4 symptoms of cryptosporidium parvum in immunocompromised?
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debilitating, cholera-like diarrhea
severe abdominal cramps maialase low grade fever |
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how should you treat cryptosporidium parvum in the immunocompromised?
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paromomycin
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what causes fluid loss in cryptosporidium parvum?
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alters the osmotic pressure
will see bits of mucus in the diarrhea but little fecal matter |
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how does cryptosporidium parvum cause damage?
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epithelial cells are damaged by invasion of parasite and t-cell mediated inflammation causing villous atrophy
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how can cryptosporidium parvum be cultured?
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acid-fast in fecal specimens (modified ziehl-neilsen)
must be preserved in 10% buffered formalyn |
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how is crypto spread?
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contaminated water
swimming pools, water parks untreated well water |
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what can cryptosporidium parvum survive?
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filtrations and chemical treatments
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what are the resistant forms of giardia lamblia?
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cysts
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how is giardia lamblia transmitted?
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through non-diarrhea feces
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what parasite has a ventral sucking disk?
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giardia lamblia
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what is the reproductive form of giardia lamblia and where does it replicate?
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trophozoites
in the lumen of the proximal small bowel |
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how long is the giardia lamblia incubation period?
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1-14 days
lasts 1-3 weeks |
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what are the symptoms of giardia lamblia? (6)
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diarrhea
abdominal pain bloating nausea vomiting |
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how do you diagnose giardia lamblia?
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microscopic identification of cysts or trophozoites in feces
sometimes duodenal fluid or biopsy |
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how long can entamoeba histolytica surviev outside a host?
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it can't
it can't survive in the acidic environment of the stomach thus it is restricted to the intestinal lumen |
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how can entamoeba histolytica cause hepatic abscesses?
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it may erode the intestinal mucosa and enter the circulation to colonize the liver (most commonly colonized organ)
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what will entamoeba histolytica present with? (4)
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URQ pain
weight loss increased WBCs elevated liver enzymes |
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what entamoeba histolytica will lung abscesses present with? (3)
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chest pain
dyspnea productive cough |
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how does entamoeba histolytica invade?
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secretion of proteolytic enzymes allows it to invade epithelial cells creating a flask shaped ulcer
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how do you diagnose entamoeba histolytica?
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microscopic evidence of trophozoites in the stool
antibody in 90% of extraintestinal infections |
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what is the problem with entamoeba histolytica antibody detection?
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it is not reliable in distinguishing past and current infections
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what distinguishes cyclospora from crypto?
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cyclospora has noninfective thick walled oocysts
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where will cyclospora sporulate?
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in the environment
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what will cyclospora contaminate?
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fruit, vegetables, water
guatemalan rasberry can be killed by washing or cooking the vegetables |
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how does cyclospora cause damage?
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encysts in the intestine releasing sporozoites
invades the epithelial cells of the small intestine and undergoes asexual reproduction to produce more oocysts which are then shed in the stool |
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where is cyclospora found?
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primarily in the subtropics
rare in US |
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how is cyclospora diagnosed?
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acid fast staining
preserved in 10% foramlin |
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what are 4 symptoms of cyclospora?
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watery diarrhea
nausea vomiting abdominal pain |
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what will cyclospora patients initially complain of?
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flu like symptoms
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how long will cyclospora last?
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for several weeks
may occur in a relapsing pattern for up to 2 months (4 in immunocompromised) |
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how do you treat cyclospora?
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self limiting
TMP-SMX |
