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Which microbes cause GI infections? HOw are pathogens causing diarrhea transmitted?

bacteria, viruses, parasites
transmitted: food, water, person-person


Discuss microbial toxin-mediated food poisoning.

you don't ingest the microorganisms themselves, you ingest the toxins
get N/V/D w/i 1-8 hours


What is non-inflammatory gastroenteritis?

Infections in the stomach and small intestine; symptoms usually include watery diarrhea, nausea, and vomiting
won't see WBCs or blood in the feces


What is inflammatory enterocolitis?

Infections in the large intestine often cause dysentery (small fecal volume with mucus and blood)


If you ingest microorganisms instead of pre-formed toxins...when will you start to see symptoms?

24-72 hours later.


What are some symptoms of esophagitis?

dysphagia (difficulty swallowing)
odynophagia (pain w/ swallowing)


What is the most common cause of infectious esophagitis? Other causes?

Most common: candida albicans
Other causes: CMV, HSV, Varicella zoster virus, HIV, TB


What are some characteristics of a pt with candida albicans esophagitis that you would expect?

immunosuppressed, steroid therapy, recent antibiotics use, systemic illness or something. maybe alcoholism


A 43-year-old HIV-positive man presents to his primary care physician with acute onset dysphagia (difficulty swallowing), odynophagia (painful swallowing), heartburn, retrosternal discomfort, nausea, and fever. Esophagogastroduodenoscopy is performed and creamy white plaques are observed in the mid to distal esophagous (A). A biopsy of the mucosal tissue is taken and stained with methenamine silver. A large number of black pseudohyphae are seen Diagnosis? Treatment?

esophagitis most likely caused by candida albicans
treatment: topical or IV antifungals, clotrimazole or fluconazole.
prognosis good.


What is odynophagia highly suggestive of?

highly suggestive of infectious esophagitis


What is another name for infectious gastritis?

peptic ulcer disease


What are most cases of PUD associated w/?

H. pylori infections


Talk about the structure of H. Pylori.

urease +
**colonizes gastric mucosa


What are the virulence factors of H. Pylori?

cytotoxic protein--vac A (vacuolating toxin)
CagA gene product


A 66-year-old man presents with a two year history of increasing epigastric pain. He characterizes the pain as a gnawing or burning sensation and occurs right after meals. Antacids provide only minimal relief of the pain. He describes belching, bloating, and distention. He denies alcohol use, but indicates that he takes 600 mg of ibuprofen three times a day to control arthritis pain. Stool exam is positive for occult blood. Fecal antigen testing identifies an active Helicobacter pylori infection. Endoscopy demonstrates a 3 cm gastric ulcer.
What exactly does this pt have? What is the appropriate treatment?

peptic ulcer disease
secondary to H. Pylori infection
Treatment: antibiotics combo: amoxicillin, clarithromycin, PPI (omeprazole) for 2 weeks
stop taking ibuprofen


What is chronic H. pylori infections a risk factor for?

gastric tumors (lymphomas, adenocarcinomas)


What is involved in the diagnosis of H. Pylori PUD?

antigen tests (stool)
urea breath test


PUD often presents with pain where?

epigastric pain


Toxin-mediated food poisoning is primarily due to which 4 bacteria?

Staphylococcus aureus
Bacillus cereus
Clostridium perfringens
Clostridium botulinum


What is the typical incubation period of staph aureus?

1-8 hours


What are the signs & symptoms of food poisoning by staph aureus toxins?

abdominal pain


Describe the epidemiology & pathogenesis of staph aureus?

staph grows in meats, dairy, other foods
produces enterotoxin
***enterotoxin acts on receptors in gut (serotonin receptors), transmits impulses to medullary centers that control vomiting.


What is the onset of staph aureus food poisoning like? Recovery?

abrupt onset, intense vomiting for 24-48 hours.
give fluids & electrolytes


What is the incubation period of bacillus cereus?

2-16 hours


What are the signs & symptoms of food poisoning by bacillus cereus?

abdominal pain
**shorter incubation period--mainly vomiting. Longer incubation period--mainly diarrhea


What is the epidemiology & pathogenesis of bacillus cereus food poisoning?

reheated fried rice
enterotoxin formed in food or gut from B. cereus growth


What is the incubation period of clostridium perfringens?

8-16 hours


What are the signs/symptoms of clostridium perfringens food poisoning?

abdominal cramping
watery diarrhea (abrupt onset, profuse)
**recovery w/i 1-4 days


What is the epidemiology/pathogenesis of clostridium perfringens food poisoning?

it grows in rewarmed meat dishes
enterotoxin produced during sporulation in gut
causes hypersecretions in gut


What is the incubation period of clostridium botulinum?

18-24 hours


What are the signs & symptoms of food poisoning by clostridium botulinum? Diagnosis?

diplopia, dysphagia, dysphonia, difficulty breathing
will need ventilatory support & antitoxin.
diagnosis--via seeing toxin in blood or stool


What is the epidemiology & pathogenesis of food poisoning via clostridium botulinum?

it grows in anaerobic food & produces toxin
toxin absorbed from gut
blocks Ach @ neuromuscular jcn


What is the most common cause of food poisoning in the US? Give the structure of this organism.

staph aureus
gram + aerobic coccus


Which types of foods often house staph aureus? When do symptoms begin?

potato salad
ham salad
sandwich spreads
things requiring hand preparations
usu symptoms begin w/i 1-4 hours


WHat are the predominant symptoms in staph aureus food poisoning?

mainly vomiting, less diarrhea


Talk about the enterotoxins of staph aureus.

low-molecular weight
heat stable (resist boiling)
bind serotonin receptors in intestine
then serotonin binds receptors on vagal afferent neurons-->get vomiting.


A 15-year-old man presents to the ER with acute onset of nausea, vomiting, and diarrhea shortly after returning from an outdoor party that was held at the home of a friend. At the party, a picnic lunch of hamburgers, hot dogs, potato salad, baked beans, and lemonade was served. The food was served outdoors, and the guests were free to eat at any time during the party. None of the food tasted spoiled or tainted. His symptoms started abruptly about an hour after he returned home, which was approximately 4 hours after he had eaten. He currently is unable to keep down anything. He does not have a fever and has not passed any blood in his stool or vomitus. Two friends who attended the same party have similar symptoms.

staph aureus food poisoning


What's the type of diarrhea experienced w/ staph aureus food poisoning?

not much of it
no WBCs or blood in it


TF Fever is a common feature of staph aureus food poisoning.

False. Fever is not a part of it.


What is the structure of bacillus cereus?

gram + aerobic rod.


What food type is associated w/ B. Cereus food poisoning? Describe Type 1 food poisoning with this.

fried rice
Type 1:
grows in starchy foods
neurotoxin-mediated emetic illness 2-3 hrs after ingestion


What is Type II food poisoning w/ b. cereus food poisoning?

found in meat, milk, vegetables, fish
heat labile enterotoxin
profuse diarrhea w/i 10-12 hrs after ingestion.


A 28-year-old woman presents at the urgent care with an acute onset of crampy diffuse abdominal pain and multiple episodes of emesis that are nonbloody. She is afebrile, denies any diarrhea, and shows no signs of dehydration. When questioned further, the patient states that her last meal was 5 hours ago when she joined her friends for lunch at a local Chinese restaurant. She ate from the buffet, which included multiple poultry dishes and fried rice.

Bacillus cereus food poisoning
from pre-formed neurotoxin


Talk again about the symptoms of B. cereus food poisoning.

no fever
diarrhea if it is there lacks WBCs or blood.


What is the structure of clostridium perfringens?

gram +
spore-forming rod
heat-resistant spores are made that can survive cooking


What are the symptoms of clostridium perfringens?

abdominal cramping
watery diarrhea (can last a while)
8-12 hrs after ingestion


Which dishes are clostridium perfringens often found in?

meat & poultry dishes
sauces & gravy


What does the C. perfringens enterotoxin do?

binds to the brush border membrane in the SI
messes w/ ion transport in ileum & jejunum


A 19-year-old man presents to the emergency department with 2 days of abdominal cramps, watery diarrhea, mild nausea, but no vomiting or fever. He has not traveled, but had dinner 3 days ago at a new Ethiopian restaurant where he ate an exotic meat dish. He is hydrated with IV fluid, given antiemetics, and discharged home after feeling much better. Two days later, the laboratory reports positive cultures for __________.

Clostridium perfringens
Note: fever & vomiting not common w/ this.


How long does it take for C. botulinum toxin to produce symptoms? What foods is this associated with?

1-2 days b/c toxin has to spread from the intestine to nerve synapses
home-canned vegetables & sausage


Describe the characteristics of botulinum toxin. What do the 30% of people who die from this after infection actually die from?

neurotoxin w/ zinc metalloproteinase--cleaves synaptosomal protein
prevents exocytosis of vesicles containing Ach
death from resp failure


A 21-year-old university student had spent Thanksgiving day with relatives at her grandparent's farm. During her drive back to campus on Friday morning her vision became blurry, and she was forced to pull over to the side of the road. As she sat in her car, her vision worsened. A highway patrol officer pulled over and approached her. By this time, she was having trouble swallowing and speaking clearly. He rushed her to the emergency room at a nearby hospital. In the ER, she was able to describe her symptoms to a physician, and to mention that her grandmother canned all of her own vegetables. The physician observed that her breathing was becoming labored, so her blood was sampled, her gastrointestinal tract pumped, and a mechanical respirator prepared for use.
Diagnosis? Further treatment?

trivalent botulinum antitoxin


Review again the symptoms of botulism.

blurred vision
pupils fixed & dilated
dry mouth
abdominal pain
muscle weakness
flaccid paralysis


When is the source of food intoxication usually sought? What is the only fatal form of food poisoning?

only sought w/ botulism
only c. botulinum is fatal


What is the treatment for toxemia due to S. aureus, B cereus, or C. perfringens?

no treatment maybe IV rehydration if dehydrated
good prevention--good hygiene, proper cooking, processing of food.


What is the treatment for C. botulinum food poisoning?

gastric lavage
trivalent (A, B, E) botulinum antitoxin


What does non-inflammatory gastroenteritis cause? Where are the bacteria of this found? Viruses that cause this found?

Abdominal cramps
watery diarrhea
**bacteria colonize surface of SI but don't invade mucosa
**viruses infect enterocytes & damage intestinal brush border


T/F In non-inflammatory gastroenteritis, fecal leukocytes are found.

False. Noninflammatory. Same whether bacterial or viral cause.


What are some causes of viral gastroenteritis?



What is the structure of noroviruses?

naked single-stranded RNA-containing viruses
Caliciviridae family


When do you usu see norovirus gastroenteritis? Who do you usu see this in?

older children & adults
seasonal, winter vomiting disease. stomach flu.


Describe the transmission of the norovirus gastroenteritis.

found in stool or vomit of infected persons
highly contagious & spreads via food, water, fomites
**think army barracks or cruise ship.


Why is it often hard to decontaminate infected cruise ships?

non-enveloped norovirus is resistant to decontamination


What are the symptoms of norovirus? WHen do you first see these? When do you stop seeing these? Treatment?

N/V Watery diarrhea
24-48 hr incubation
duration: 12-60 hrs
make sure they are dehydrated


Which symptoms are NOT seen in norovirus gastroenteritis patients that tips you off that it is NOT a bacterial cause?

no fever
no bloody stools
no severe abdominal pain


What is the structure of the rotavirus? Transmission?

naked double-stranded RNA virus
**replicates in the intestines of the wild animals, transmitted via fecal-oral route.


Which patients do you usu see rotavirus gastroenteritis in?

children <2 yo, severe diarrhea & dehydration, dry skin, lethargy, poor skin turgor
more commonly seen in the winter


What do rotaviruses do in the intestines?

enter mature enterocytes at the tips of the intestinal villi
rotaviral enterotoxin (NSP-4) induces Cl- & fluid secretion (diarrhea).


The patient was a 3-year-old male brought to the hospital by his parents in early December because of fever and dehydration. His parents reported that he had a 3-day history of fever, watery diarrhea, emesis, and decreased urine output. On admission his vital signs were temperature 39.5°C, pulse 126/min, respiratory rate 32/min, blood pressure 110/75. He was somnolent. Physical exam revealed only hyperactive bowel sounds. There were no leukocytes, or blood in the stool. Stool, blood, and urine cultures were negative for bacteria. A rapid enzyme immunoassay on the stool samples revealed rotavirus. The patient was given normal saline IV for rehydration and his emesis abated in 48 hours. He was discharged home.

n/v watery diarrhea
no leukocytes or blood in stool
oral rehydration is all that is really required, self-limiting.


What are some things that can be used to diagnose a rotavirus infection?

rapid antigen tests of stool
-enzyme immunoassay or latex agglutination test


T/F Persons who are infected with norovirus or rotavirus should not prepare food while they are symptomatic and for 3 days after they recover from the illness



Describe the rotavirus vaccines available.

given at ages 2, 4, 6 months
rotatez & rotarix


What is the most common cause of traveler's diarrhea?

E coli--bacterial gastroenteritis
**ETEC: enterotoxigenic E Coli
**EAEC: enteroaggregative E coli
**EPEC: enteropathogenic E Coli


Which of the E coli types that can cause E coli gastroenteritis can cause diarrhea in infants?

mainly ETEC
mild diarrhea--EPEC


What does ETEC colonize & which enterotoxins does it produce?

LT (heat labile toxin). A-B toxin, causes increase in cAMP
ST (heat stable toxin) increases cGMP
**cause secretion of chloride & watery diarrhea


A 21-year-old woman presents with the complaint of diarrhea. She returned from Mexico the day before her visit. The day before that, she had an acute onset of profuse watery diarrhea. She denies blood or mucus in the stools. She has had no associated fever, chills, nausea, or vomiting. She has no other medical problems and is taking no medications. Examination is remarkable for diffuse, mild abdominal tenderness to palpation without guarding or rebound tenderness. Stool is guaiac negative.

ETEC most likely, most common cause of traveler's disease in Mexico.
Treatment: prevent dehydration & maybe use antibiotics (ciprofloxacin, maybe rifaximin)
bismuth subsalicylate may provide symptomatic relief


Profuse and watery diarrhea suggests infection at which site?



Absence of bloody stool means which type of diarrhea is less likely?

inflammatory diarrhea


What provides a definitive diagnosis of ETEC?

stool culture on MacConkey agar
assay for toxins by immunoassay or toxin genes w/ DNA probe


What is guiac a test for?

occult blood


What is the structure of vibrio cholera?

slightly curved gram neg. rod
acid sensitive
illness is due to the a-b enterotoxin in the SI
LPS types-140!
O1 & O139 produce the cholera toxin.


What is the bad result that can come from cholera?

rapid loss of H2O & electrolytes from GI tract, hypovolemic shock, metabolic acidosis, death


How do vibrio cholera organisms do their thing?

attach to microvilli of jejunum & ileum
make cholera enterotoxin, mucinase, endotoxin
don't invade mucosa
**do this by ADP-ribosylation that increases adenylate cyclase activity, increased cAMP & fluid secretion.


What are some other species of vibrio that can cause similar symptoms to cholera?

V. parahemolyticus
V. vulnificus


A 57-year-old man was hospitalized in New York with a 2-day history of severe, watery diarrhea and vomiting. The illness had begun 1 day after his return from Ecuador. The patient was dehydrated and suffering from an electrolyte imbalance (acidosis, hypokalemia). He recalled having oysters on the half shell the last night of his trip. The patient made an uneventful recovery after fluid and electrolyte replacement was instituted to compensate for the losses resulting from the watery diarrhea.

stool cultures on TCBS agar + for vibrio cholerae.


Which food is often associated with cholera? What is the treatment?

Food: often contaminated seafood
treatment: rehydration therapy, severe cases azithromycin or doxycycline


What is the main thing seen on presentation that tips you off to cholera?

rice water stool


Describe the structure of giardia lamblia.

flagellated protozoan
growing form: trophozoite
environemntal resistant form: cyst


Describe the transmission of giardiasis.

parasite lives in the SI of humans & domestic & non domestic mammals
get by consuming cystic forms in water or food
**also transferred via fecal-oral route @ day care centers


A 24-year-old female medical student from Reno presents to the urgent care with crampy abdominal pain, flatulence, and a watery, foul-smelling diarrhea that has worsened over 3 days. She is an avid hiker and reported several recent hikes up Hunter Creek canyon to look at the mountain beaver dams. On the last hike 10 days ago she forgot her water purifier and drank creek water.
Diagnosis? Treatment?

Stool examination shows small cysts containing four nuclei, and stool antigen immunoassay is positive for Giardia lamblia. She was treated with metronidazole (Flagyl) and made an uneventful recovery.


Incubation period of giardiasis? Symptoms?

10 day incubation period
crampy abdominal pain
smelly, watery diarrhea
**severe & chronic--malabsorption problems
**spontaneous recovery


How do you diagnose giardiasis?

detect g. lamblia trophozoites or cysts in feces collected on 3 consecutive days
duodenum can be sampled by string test (enterotest). swallowed capsule.
NOTE: chlorination doesn't kill these cysts in water. Needs to be properly filtered or boiled


Aside from giardiasis, give another cause of parasite diarrhea.

C. parvum is a coccidian parasite that is found in intestines of bunches of animals & is found in water


HOw is crytposporidium parvum transferred?

via oocysts-->can cause persistent chronic diarrhea particularly if immunocompromised
**day care centers & MSM
autoinfections & person-person spread (fecal-oral, anal-oral).


A 28-year-old woman is brought to the hospital because of abdominal pain, weight loss, and dehydration. She has been diagnosed with HIV for the past 2 years with a history of oral candidiasis and pneumocystis pneumonia. She reports voluminous watery diarrhea over the past 2 weeks. Because of medical non-compliance, she has not taken any antiretroviral therapy. Stool samples were concentrated by flotation and stained with an acid-fast stain.
Diagnosis? Treatment?

oocysts for c. parvum were found in stool samples.
no anti-parasite drug for HIV+, so antiretroviral therapy to strengthen immune system.


How much fluid loss is possible w/ an HIV pt w/ crytposporidiosis?



Describe in more detail what happens to your intestine w/ C. parvum infection.

intestinal ion transport compromised
inflammatory damage of the microvilli
malabsorption of the SI


How can you visualize C. parvum parasites?

stool smear w/ Kinyoun acid-fast stain to visualize
C. parvum is acid fast


What is the drug of choice for c. parvum infection if the patient isn't immunocompromised?

maybe some diarrheal agents too.


Which diseases are included in the category of inflammatory enterocolitis?

pseudomembranous colitis
bacterial dysentery
amebiasis (parasitic dysentery)


What are some organisms that can cause bacterial dysentery?

E coli


Where do inflammatory enterocolitis diseases usu take place?

in the distal SI & colon
can invade surrounding tissues


Inflammatory enterocolitis has a distinguishing feature. what is it?

blood in feces


Describe the structure of C. diff.

gram +
spore-forming rod
produces toxin A (enterotoxin) & toxin B (cytotoxin)


pseudomembranous colitis caused by C diff looks like what?

toxin-mediated destruction of colonic epithelium w/ pseudomembrane formation
**often happens w/i hospital after long-term antibiotic treatment


An 78-year-old white woman was readmitted to the hospital because of recurrent pneumonia. Ten days earlier, she had been treated at another institution. She had been treated with amoxicillin for right lower lobe pneumonia. Upon readmission she was febrile and her WBC count was 36,000 per mm3. She had lower abdominal pain and passed several loose bloody, stools.
Diagnosis? Treatment?

C. diff pseudomembranous colitis is a possible result after diarrhea (type of inflammatory enterocolitis)
stool sample would show C diff toxin A.
sigmoidoscopy would show pseudomembranous colitis
treatment: stop other antibiotics, start on metronidazole


Once again, what are the symptoms of C. diff pseudomembranous colitis?

abdominal pain
low-grade fever
blood in stool


Which antibiotics are commonly implicated in cases of C. diff?



Describe how the pseudomembranous colitis forms w/ C diff infection.

toxins--depolymerize actin filaments & cells round up & detach & you get shallow ulcers
acute inflammation w/ pus & mucus-->pseudomembrane


What are some down the road implications of pseudomembranous colitis from C. diff?

toxic megacolon
bowel perforation


How do you diagnose & treat C. diff inflammatory gastroenteritis?

diagnosis, usu don't culture but can see toxins A &B w/ fecal specimen
can also use sigmoidoscopy
treatment--withdrawal of antibiotic, rehydration, metronidazole or vancomycin
fecal enema


T/F Antimotility drugs are a useful treatment for C. diff infection.

False. increase the risk for full-blown colitis or toxic megacolon
used if you don't have access to toilet


How should toxic megacolon be treated?

surgically resect the area of bowel that is affected.


Which area of the gut does bacterial dysentery target? What are the symptoms?

large intestine affected by invasive organisms that prompt inflammation
symptoms/results--small stool volume w/ mucus & leukocytes and maybe blood
fever, abdominal pain, tenesmus


What is tenesmus?

pain w/ defecation


What are some organisms responsible for bacterial dysentery?

Campylobacter jejuni
yersinia enterocolitica
E coli (EIEC)


Describe the structure of campylobacter jejuni (a possible cause of bacterial dysentery).

S-shaped OR gull wing-shaped rods
paired rods


Where do you find C. jejuni?

undercooked or raw meat
unpasteurized milk
nonchlorinated contaminated water


What are the 2 top causes of invasive dysentery?

1. salmonella
2. campylobacter jejuni


A previously healthy 32-year-old man describes 1 to 2 days of fever, myalgia, and headache followed by abdominal pain and diarrhea. He has experienced up to 10 bowel movements over the past day. He has noted mucus and blood in the stool. The patient notes that 3 days ago, he was at a church picnic where he ate barbeque chicken. He has not traveled in more than 6 months. Physical examination is unremarkable except for a temperature of 38.8°C and diffuse abdominal tenderness.
Diagnosis & treatment?

Wright's stain of a fecal sample reveals the presence of neutrophils. Colonoscopy reveals inflamed mucosa. Fecal culture on Skirrow agar under microaerophilic conditions at 42°C reveals colonies of gram-negative, motile, S-shaped rods. The diagnosis is campylobacteriosis.


What are the symptoms found w/ campylobacteriosis?

abdominal cramps
bloody stools
fecal leukocytes
**superficial ulcers on bowel mucosa


What toxin does C. jejuni sometimes produce?

shiga toxin
a protein synthesis inhibitor


Once again, how do you diagnose campylobacteriosis?

culture of stool & ID of gull wing-shaped bacteria in watery, bloody, leukocyte-filled feces
bacteria have darting motility


What is the treatment for C. jejuni infection?

oral rehydration
usu no antibiotics
azithromycin or ciprofloxicin if extreme.


What is a rare complication of campylobacteriosis?

post-campylobacter guillain-barre reactive arthritis
b/c endotoxin cross reacts w/ gangliosides found in CNS


Which types of E coli have the shiga toxin? What does this toxin cause?

enterohemorrhagic E coli (EHEC)
enteroinvasive E coli (EIEC)
causes cell death, edema, hemorrhage in lamina propria. attachment to epithelial cells & effacement of microvilli
in kidneys can cause hemolytic uremic syndrome


Where do you find EHEC?

in the intestines of healthy cattle
you can eat bad meat


Which type of EHEC is the most common cause of hemorrhagic colitis & HUS?

EHEC serotype O157;H7


What tips you off that you are dealing with EHEC?

watery bloody diarrhea w/ hx of ground beef ingestion
abdominal cramps w/o fever
E coli in stool that is typed to be O157; H7 should be reported to the state health dept


A 25-year-old, previously healthy woman came to the emergency room for the evaluation of bloody diarrhea and diffuse abdominal pain of 24 hours duration. She complained of nausea and had vomited twice. She reported no history of inflammatory bowel disease, previous diarrhea, or contact with other people with diarrhea. The symptoms began 24 hours after she had eaten an undercooked hamburger at a local fast food restaurant. Rectal examination revealed watery stool with gross blood. Sigmoidoscopy showed diffuse mucosal erythema and petechiae with a modest exudation but no ulceration or pseudomembranes.

EHEC confirmed by growth on MacConkey medium
**E coli infection, hemorrhagic colitis


WHAT CAN EIEC infection produce?

watery diarrhea
dysenteric stools (small volume, mucous-containing bloody feces)


Physicians and state epidemiologists investigate a cluster of acute diarrheal cases in children who attend a preschool in a small Midwestern town. The children presented with fever, acute episodes of bloody diarrhea, and petechial rash or purpura. Two of the children have scanty urine output and are showing signs renal failure (azotemia). Both have leukocytosis (>20,000/mm3). They are anemic and show schistocytes on peripheral blood films.
Further work up? Diagnosis?

Shiga toxin is identified in stools by immunoassay, and stool cultures on MacConkey/Sorbitol agar indicate enterohemorrhagic Escherichia coli (EHEC). The two children are diagnosed with hemolytic uremic syndrome (HUS).
**begins as hemorrhagic colitis & has leukocytosis
**common in


Describe the features of HUS.

HUS is a microangiopathic hemolytic anemia marked by the appearance of thrombocytopenia, schistocytes, and azotemia


Describe the structure of E coli.

gram neg.
lactose-fermenting bacilli


Which drugs should NOT be given in cases of EHEC & EIEC infections?

antimotility & antibiotics
b/c this will cause release of more toxin & increase the likelihood that the pt will develop HUS


What is the structure of shigella?

**non-lactose fermenting
gram-neg. rods
(closely related to E coli)


What is the most common species that causes shigellosis in the US?

shigella sonnei


Describe the spread of shigellosis?

strictly human disease
pediatric disease in US
fecal-oral route
spread via food or water contaminated by humans
rate of secondary attacks: 40%


How do patients with shigellosis present?

abdominal pain
**more severe in children
**often seen in closed population groups


What exactly does the shiga toxin do in shigellosis?

infect colon epithelial cells & inhibit protein synthesis


What is the process for diagnosis & treatment for shigellosis?

diagnosis--culture stools for shigella sonnei (on Hektoen enteric or S-S agar). look for WBCs (lactoferrin +)
rectal biopsy--ulcers, microabscesses
treatment--antibiotics & fluid replacement


Is there a treatment that is contraindicated in patients with shigellosis?

antidiarrheal compounds


What is the structure of salmonella?

gram neg. bacilli
produce hydrogen sulfide


How can you distinguish E coli from salmonella or shigella?

E coli is lactose fermenting
Shigella & Salmonella are lactose non-fermenting


What exactly causes enteritis in salmonellosis?

serovars of S. enterica


What can typhi & paratyphi A serovars of S. enteric cause?

enteric or typhoid fevers


Describe the epidemiology of salmonellosis.

salmonella found in animals.
strains that create typhoid only found in humans
**some humans become chronic carriers of typhoid-causing types
transmission from animals-->humans
OR animal food products-->humans


A 37-year-old man presented with a 2 day history of abdominal cramps, diarrhea, nausea, and vomiting. His vital signs are normal except for a low grade fever. One day prior to the onset of symptoms, he had visited his grandmother who prepared soft-boiled eggs for breakfast. His clinical history reveals gastroesophageal reflux disease for which he regularly takes antacids. Examination of a fecal smear from the patient revealed abundant fecal leukocytes.
Further workup & diagnosis?

fecal culture reveals lactose non-fermenting salmonella
diagnosis: salmonella enterocolitis


Once again, where do you commonly find salmonella? What is the presentation?

eggs, poultry, dairy
non-bloody diarrhea, fever, myalgias, abdominal cramps
24-48 hrs after ingestion
**decrease in gastric acidity (GERD treatment) predisposes


How does salmonella do its thing once it gets in the gut?

invades intestinal mucosa
multiplies in macrophages in lymph follicles
enters mesenteric lymph nodes to blood & disseminates


A 20-year-old male is brought to the emergency department with a 1-day history of delirium. He has had a sustained fever of up to 40°C and a history of progressive headache, myalgia, and constipation which began 10 days previously as he was returning to the United States from a trip to visit relatives in India. Physical examination revealed hepatosplenomegaly, diffuse abdominal tenderness, and red spots on the chest and neck. Colonies of a Gram-negative bacillus that produced a characteristic “fish-eye” growth (lactose nonfermenter with sulfur reduction) are isolated on Hektoen agar

typhoid fever caused by salmonella typhi


10-14 days after ingestion of salmonella, patients begin experiencing what?

persist for 1wk (bacteremic phase)


Where is the reservoir for salmonella in the body? What happens next?

reservoir is gallbladder
reinfection of the intestines w/ diarrhea


What is seen on the skin of patients infected with S. Typhi?

rose spots, skin lesions


What is necessary for definitive diagnosis of salmonella?

Isolation of the organisms from a fecal sample using Hektoen or S-S agar followed by biochemical identification (API20E) is necessary for a definitive diagnosis


What is the appropriate treatment for salmonella? Contraindicated treatments?

fluid & electrolyte replacement good.
antidiarrheal compounds & usu antibiotics are contraindicated.
if the pt has enteric fever-->need antibiotic therapy (cipro or ceftriaxone)


What are the 2 typhoid vaccines available in the US?

oral LAV
Vi capsular polysaccharide vaccine that is injected


Describe the structure of yersinia enterocolitica.

gram neg.
family of enterobacteria
zoonotic disease
injects yersinia protein kinase A & YOPE into eukaryotic cells.


Describe the features of yersinosis.

enteric fever-like illness
mesenteric adenitis
inflammatory ileitis
ulcerative colitis syndrome
**may also be associated with migratory polyarthritis, Reiter's syndrome, erythema nodosum
**can mimic acute appendicitis


Most yersiniosis can be traced to what?

consumption of contaminated meat, milk, water


A 7-year-old boy presents to the emergency department with fever, abdominal pain, and tenderness in the right lower quadrant. A white blood cell count reveals leukocytosis. Suspecting appendicitis, the child is taken to surgery; however, the removed appendix is grossly and histologically normal.

gram neg. rod
can see on cold enriched fecal cultures on CIN agar.
PCR can reveal y. enterocolitica


What is the treatment for yersiniosis?

usu self-limiting
can be treated by doxycycline & tobramycin


What is the xtag gastrointestinal pathogen panel?

This panel is a multiplexed nucleic acid test that detects seven bacterial pathogens (Campylobacter, Clostridium difficile toxin A/B, Escherichia coli O157, enterotoxigenic E. coli LT/ST, Salmonella, Shigella, and Shiga-like toxin producing E coli stx 1/stx 2), two viruses (norovirus and rotavirus A), and two parasites (Cryptosporidium and Giardia)


What causes amebiasis? Important features?

entamoeba histolytica, a protozoan parasite
**causes dysentery
cyst form is infectious
liver common site of extra intestinal amebic disease


Which patients are at higher risk for amebiasis?

travelers outside US
recent immigrants
institutionalized populations


A 31-year-old immigrant from Mexico presents with lower quadrant abdominal tenderness of a month duration. He has recently noted diarrhea with blood and mucous in his stool. His vital signs are temperature 38° C, heart rate 78, respirations 18, and blood pressure 128/78. On physical exam he has abdominal pain, distention, and rebound tenderness. Workup & diagnosis?

order fecal leukocytes
antigen test for entamoeba histolytica
trichrome stain
**few leukocytes & pos. antigen test & microscopy shows trophozoites w/ ingested RBC


What is the treatment for amebiasis?

metronidazole or tinidazole
luminal agent--iodoquinol


WHat else is on the differential w/ patients who have amebiasis?

other causes of dysentery
inflammatory bowel disease


What are other important findings w/ amebiasis?

amebic liver abscess b/c trophozoites can penetrate the colon & infect the liver (sometimes need to be surgically drained)
parasite releases cytotoxins that destroy leukocytes
flask-shaped ulcers when the bug eats thru LP.


Describe important features in the diagnosis of amebiasis.

**If the cytoplasm of the trophozoite contains red blood cells, the diagnosis of amebiasis is definitive
**Leukocytosis without eosinophilia is common
**Immunoassays are used to detect cysts in feces; serology is useful in extraintestinal infections
**Chest radiograph, CT scan, and MRI are useful in visualizing extraintestinal amebic abscesses
**A brown anchovy paste-like material is often aspirated from liver abscesses


What are some important characteristics of schistosoma mansoni & s. japonicum?

flukes in mesenteric veins lay eggs
cause fever, malaise, abdominal pain, liver tenderness
chronically can cause bowel inflammation & blood in stool


What are some important features of adult hookworms?

hookworms (Ancylostoma duodenale and Necator americanus) in the small intestine produce the gastrointestinal symptoms of nausea, vomiting, and diarrhea with copious amounts of blood. As blood is lost from feeding worms, a microcytic hypochromic anemia develops


Describe what the deal is with trichiuris trichirua.

trichirua (whipworm) larvae may produce abdominal pain and distention, bloody diarrhea, weakness, and weight loss. Anema is seen in severe infections


What are intestinal infections w/ large strongyloides stercoralis worms like?

worm burdens can affect the entire small bowel and the colon. Inflammation and ulceration causes epigastric pain and tenderness, vomiting, diarrhea (occasionally bloody), and malabsorption


What are important features of balantidium coli?

cause abdominal pain and tenderness, tenesmus, nausea, anorexia, and watery stools with blood and pus. Ulceration of the intestinal mucosa possible


What are some important features of cyclospora?

infections cause mild nausea, anorexia, abdominal cramping, and watery diarrhea. Fatigue, malaise, flatulence, and bloating has also been reported. Similar in presentation to cryptosporidiosis


What are important features of isospora belli?

infected patients may be asymptomatic, or suffer mild to severe gastrointestinal disease. Disease most commonly mimics giardiasis, with a malabsorption syndrome characterized by loose, foul-smelling stools


What are some important features of dientamoeba fragilis?

can colonize the cecum and colon. Some patients may develop symptomatic disease with abdominal discomfort, flatulence, intermittent diarrhea, anorexia, and weight loss


A 62-yr-old female patient who lived in a local rural village in Guatemala had suffered from severe chronic anemia for several years. She was transferred to a hospital in Guatemala City for management of severe dyspnea and dizziness. At admission, she showed symptoms or signs of severe anemia.
Workup & diagnosis?

stool exam-hookworm eggs
Endoscopy of the duodenum identified Necator americanus by characteristic morphology of cutting plates in the buccal cavity

Hookworm disease
treated w/ albendazole & supportive measures for anemia


HOw does early & chronic hookworm disease present? Protracted infections may cause what? Treatment?

Early: cutaenous lesions & pneumonitis
Chronic: blood in stools & anemia
protracted: developmental delay in children
treatment: albendazole & iron supplementation