Term
| what is the the 2nd leading cause of morbidity/mortality in the world? why? |
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Definition
| diarrhea - and it is the leading cause w/respect to infection, as it outpaces TB, AIDS, and malaria. over 1 billion people in the world don't have access to safe drinking water. |
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Term
| what are the long term sequelae associated with infectious diarrhea? |
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Definition
| HUS, renal failure, guillaume-barre (from campylobacter), and malnutrition |
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Term
| how do children under 3 yrs compare to adults in terms of rates of infectious diarrhea? |
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Definition
| children get diarrheal episodes 2x as often as adults |
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Term
| what are sources of exposure to infectious diarrhea? |
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Definition
| travel, ingestion of raw/undercooked meat, seafood, milk products, ill contacts, daycare, institutional exposure, farms, zoos, recent antibx use, and sexual activity |
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Term
| what is the definition of diarrhea? (*need to know*) |
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Definition
| an *increase in daily stool wt > 200g, including increase in frequency/fluidity/amount |
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Term
| what does diarrhea need to be differentiated from clinically? |
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Definition
|
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Term
| what defines acute vs chronic diarrhea? |
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Definition
acute: episodes less than 2 wks
chronic: over a month |
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Term
| what does diarrhea need to be differentiated from clinically? |
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Definition
|
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Term
| what are the 2 kinds of acute diarrhea? |
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Definition
| inflammatory (pts febrile, blood in stool, colonic damage - includes shigella, e. coli, crohn's, and ischemic bowel) and non-inflammatory (larger volume - watch dehydration, cryptosporidia, cholera, norovirus, rotovirus, giardia, e. coli, laxative abuse) |
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Term
| what do you do in the case of persistent diarrhea (more than 2 wks)? |
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Definition
| stool cx: collect for 3 days to check malabsorption (fat, lytes, osmolality), check for O+P, and sigmoidoscopy to visualize the mucosa |
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Term
| what do most pts with acute diarrhea respond to? |
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Definition
| rehydration and antidiarrheal agents w/in 5-7 days |
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Term
| why not do stool cx more routinely? |
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Definition
| pathogens are isolated from stools only 3% of the time and can be expensive. |
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Term
| what is a good, cheap diagnostic for pts with persistent diarrhea? |
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Definition
| WBC test to check inflammatory status |
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Term
| what will a colonoscopy help determine in the case of persistent diarrhea? |
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Definition
| check for UC, ischemic colitis, and c. diff (can give a false negative on assay) |
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Term
| what are the pros/cons of bypassing stool cx w/a persistent diarrhea pt and treating empirically? |
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Definition
| pros: possible quicker resolution of diarrhea, diarrhea may have resolved before cx results come back anyway, can be expensive. cons: public health importance (salmonella/shigella need to be reported), cxs help determine resistance issues, if e coli 0157:H7 is treated with antibx - in kids HUS may occur, some antibx can create shigella/salmonella carrier state, and VRE colonization risk |
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Term
| what are some approaches to improve the cost effectiveness of stool cxs? |
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Definition
| selective testing - such as for e coli 0157:H7 w/specific media, 3 day rule for pts in hospital (only worry about pts who have been in the hospital for more than 3 days), and screening for inflammatory diarrhea (fever, tenesmus, bloody stools, WBCs) |
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Term
| what is the most common bacterial pathogen responsible for infectious diarrhea in the US? what are some other causes? |
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Definition
| e. coli and its many kinds, (campylobacter in the world). though c. diff is catching up. yersinia, vibrio, aeromonas and pleisomina (also causes cellulitis) |
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Term
| what are the viral pathogens responsible for infectious diarrhea? how are they treated? |
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Definition
| norovirus (cruise ships), calicivirus, astrovirus, and rotovirus. for these = only treat symptoms |
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Term
| what is the most common parasite responsible for diarrhea? others? |
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Definition
| giardia is the most common (from mountain lake water), followed by entamoeba histolytica, cyclospora, cryptosporidium, and microsporidium |
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Term
| what are the chronic infectious agents (diarrhea lasts for more than a couple wks)? |
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Definition
| giardia, entamoeba histolytica, and cyclospora |
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Term
| what are the AIDS-related diarrheal infections? |
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Definition
|
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Term
| what characterizes diarrhea due to salmonella? what causes it? how is it treated? how long is the pt a carrier? |
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Definition
| salmonella is associated with contaminated poultry/egg yolk and incubation is 8-48 hrs. pts present with diarrhea but there is little invasion of the bowel- antibx are not recommended unless the pt is immune compromised. pts can carry infectious particles for up to 2 mos after resolving infection - need to check stools 1x/week and stress importance of hygiene maintenance. |
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Term
| what are the different kinds of e. coli and related diseases? |
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Definition
| enterotoxigenic: traveler's diarrhea (most common cause). enteroinvasive: dysentery. enteropathogenic: infant diarrhea. enterohemorrhagic: 0157 - can cause HUS/microangiopathic hemolytic anemia, liver, and hematopoietic problems. |
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Term
| what is a common cause of c. diff infections? |
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Definition
| overuse of virtually any antibx as well as radical changes in diet, bowel sx, radiation or chemo - all of which alter normal bowel flora, allowing c. diff overgrowth and development of pseudomembranes which cause malabsorption. |
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Term
| what are contributing factors that increase c. diff risk (check these before antibx adm)? |
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Definition
| recent antibx usage, enemas, GI stimulants, often/constant hospitalization, elderly, critically ill, burn patients, hemologic malignancy, and GI sx - alters GI motility |
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Term
| what characterizes humans as a c. diff reservoir? can c. diff be found in infants? what is the carriage rate in healthy adults? asymptomatic hospitalized adults on antibx? nursing home residents? |
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Definition
| c. diff or one of its toxins is found in 15-70% of neonates while the carriage rate in healthy adults is <3-8%. the c. diff carriage rate for hospitalized asymptomatic adults on antibx is 20% and 2-8% for elderly nursing home residents (asymptomatic, b/c few harbor enough toxin A/B) |
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Term
| what are common nosocomial sources of c. diff? |
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Definition
| bed sheets, bed rails, walls, nursing/medical staff hands (c. diff is gram +, a spore-former). c. diff pts are now quarantined. |
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Term
| where in the environment can c. diff be found? |
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Definition
| soil, swimming pools, beaches, sea, river and tap water |
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Term
| what is the c. diff carriage rate for household pets? |
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Definition
|
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Term
| how did c. diff antibx resistance start? how is it progressing? |
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Definition
| clindamycin and ampcillin were the first to incur resistance w/c. diff, but newer strains are increasingly more resistant to most antibx (esp broad spectrum, b/c they are the most likely to interrupt normal bowel flora) |
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Term
| what is the pathogenesis of c. diff? |
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Definition
| acid-resistant spores convert to vegetative forms after exposure to bile. the organisms grow throughout the bowel, rather than attaching to specific receptors. *toxin A causes a diffuse lymphocytic infiltrate in the lamina propria in the apical portions of the villi, leading to edema and bulging of the bowel (toxin A + B mediate cytoskeletal derangement). ensuing cytolysis and separation of the basal portions of the apical epithelial cells leads to eventual *pancolitis. the colonic mucosa is eventually studded with adherent, raised white and yellow plaques that coalesce - pseudomembranes which are most pronounced in the recto-sigmoid colin. |
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Term
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Definition
| a new strain of c. diff set off by levaquin, which produces 15-20x more toxin than before. this and other new strains have produce second binary toxins and have partial deletions in the gene which down-regulates toxin A + B expression |
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Term
| what is a good diagnostic cue for c. diff? |
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Definition
| diarrhea and a *very high WBC count |
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|
Term
| what needs to be differentiated when considering antibx-related diarrhea? |
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Definition
| AAD (antibiotic associated diarrhea) from AAC (antibiotic associate colitis) |
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Term
| what is the clinical manifestation of c. diff? |
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Definition
| can be asymptomatic or fatal. symptoms start 5-10 days after antibx tx and consist of to fever, nausea, malaise, dehydration, leukocytosis, abdominal pain, hypoalbumninemia, anorexia |
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|
Term
| how is c. diff diagnosed? |
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Definition
| stool for c. diff toxin assay (up to 3x b/c of possible false negative), CT scan, WBC count (>10,000) and endoscopy |
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Term
| what are intra-abdominal c. diff complications? |
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Definition
| toxic megacolon, colonic perforation, transverse volvulus, protein-losing enteropathy, and recurrent CDAD |
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Term
| what does c. diff need to be differentiated from? |
|
Definition
| ischemic colitis and diverticultis (the antibx for this will worsen c. diff) |
|
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Term
| how is it possible to have c. diff w/o diarrhea? |
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Definition
| if c. diff causes toxic megacolon, then diarrhea may not occur. leukocytosis may also not occur, and presentation may simply consist of acute abdominal syndrome (abdominal pain, distension, guarding, etc.). |
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|
Term
| what is the definition of toxic megacolon? |
|
Definition
| acute dilation of the colon to a diameter greater than 6 cm, associated systemic toxicity, absence of mechanical obstruction, and a high mortality rate (64%). |
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|
Term
| what is the first step in treating c. diff? |
|
Definition
| stop the offending agent - if due to antibx use |
|
|
Term
| what antibx will work against c. diff? how should they be used? |
|
Definition
| metronidazaole and vancomycin (oral or gentle rectal enema - *NO IV*) if recurrent. oral drugs should never be administered concurrently. pts can't be on metronidazole longer than 20 days due to peripheral neuropathy risk. nitazoxanide can also be used (good for crypto). |
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Term
| what are indications for sx in c. diff pts? |
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Definition
| acute abdomen, sepsis, MOFS, hemorrhage, toxic dilatation, perforation, and deterioration despite medical therapy |
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Term
| what is the rate of recurrence in c. diff pts? what is this thought to be due to? |
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Definition
| ~20%. recurrence is thought to be due to persistence of c. diff spores, which can be helped by tapering doses over one month and probiotics. recurrence is not thought to be due to resistance b/c the antibx kill just the vegetative forms, not the spores. |
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Term
| which is more severe, a recurrent or primary c. diff infection? |
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Definition
|
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Term
| how does one c. diff recurrence affect the likelihood of more? are there other factors which affect this likelihood? |
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Definition
| pts w/one recurrence are 65% more likely to have further recurrences. other risk factors for recurrence include female gender, springtime onset, and exposure to additional antibx |
|
|
Term
| why does colonic perforation risk increase with recurrence? |
|
Definition
| b/c toxic megacolon risk also increases |
|
|
Term
| what are indications for sx in recurrent c. diff pts? |
|
Definition
| abdominal pain/megacolon and high WBC counts |
|
|
Term
| what characterizes norovirus? common/less common symptoms? onset? |
|
Definition
| norovirus is the most common cause of infectious gastroenteritis in the total population. common symptoms: vomiting, diarrhea, some stomach cramping. less common symptoms: low-grade fever, chills, headache, myalgias, nausea, and fatigue. it has a sudden onset and lasts 1-2 days. |
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Term
| what are virulence factors for norovirus? |
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Definition
| norovirus is resistant to chlorination/freezing, it can persist in the environment, and only requires low inocula to infect (<100 particles). it is a notorious cause of cruise ship outbreaks. |
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Term
| how are most norovirus outbreaks spread? |
|
Definition
| p2p and environmental contamination, rather than food. |
|
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Term
| how is norovirus transmission risk reduced? |
|
Definition
| frequent hand-washing and abstaining from eating sketchy shellfish |
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|
Term
| how is infectious diarrhea managed? |
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Definition
| initiate rehydration, ascertain how the illness began, perform selective fecal studies and depending on results, institude selective therapy for shigella, salmonella, campylobacter |
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Term
| why should anti-motility drugs not be given for dysentery? |
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Definition
| b/c these remove fluids as they work |
|
|
Term
| what vaccines are available to prevent some forms of infectious diarrhea? |
|
Definition
|
|
Term
| what is the first step in management of infectious diarrhea? |
|
Definition
| distinguish inflammatory status |
|
|
Term
| what characterizes tx for inflammatory diarrhea? |
|
Definition
| avoid anti-motility drugs, always treat c. diff/ambebiasis/enteric fever/shigella/STDs |
|
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Term
| what characterizes tx for non-inflammatory diarrhea? |
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Definition
| rehydration is most important, loperamide can help, anti-cholinergics are contraindicated due to megacolon risk. always treat: cholera, giardiasis, and traveler's diarrhea |
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Term
| when should fecal testing be considered? |
|
Definition
| when diarrhea lasts longer than a day, esp if accompanied by fever, bloody stools, systemic illness, recent antibx use, day care attendance, hospitalization, dehydration, or food handlers |
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|
Term
| what should also be considered when testing stools from diarrheal pts? |
|
Definition
| serum chemistry, CBC, blood cx, urinalysis, KUB, anoscopy or flex sigmoidoscopy |
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|
Term
| what is the best tx option for shigella? |
|
Definition
| azithromycin - also TMP/SMZ, floroquinolones |
|
|
Term
| what is the best tx option for campylobacter? |
|
Definition
|
|
Term
| what is the best tx option for yersinia? |
|
Definition
|
|
Term
| what is the best tx option for c. diff? |
|
Definition
| metronidazole or vancomycin |
|
|
Term
| what is the best tx option for giardia? |
|
Definition
| metronidazole, tinidazole, and nitazoxanide |
|
|
Term
| what is the best tx option for cryptosporidium? |
|
Definition
| nitazoxanide, paromomycin |
|
|
Term
| what is the best tx option for cyclospora? |
|
Definition
|
|
Term
| what is the best tx option for entamoeba histolytica? |
|
Definition
|
|
Term
| what is the best tx option for e. coli? |
|
Definition
| quinolone or azithromycin. stay away from antibx for enterohemorrhagic |
|
|
Term
| what is controversial about treating e. coli 0157:H7? |
|
Definition
| treatment with TMP/SMZ, fluoroquinolones or beta-lactams increases the risk of HUS, unless given within 3 days of onset of diarrhea - most severe in children |
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