Flashcards in GI Infections-Hunter Deck (180)
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1
Which microbes cause GI infections? HOw are pathogens causing diarrhea transmitted?
bacteria, viruses, parasites
transmitted: food, water, person-person
2
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
3
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
4
What is inflammatory enterocolitis?
Infections in the large intestine often cause dysentery (small fecal volume with mucus and blood)
5
If you ingest microorganisms instead of pre-formed toxins...when will you start to see symptoms?
24-72 hours later.
6
What are some symptoms of esophagitis?
dysphagia (difficulty swallowing)
odynophagia (pain w/ swallowing)
7
What is the most common cause of infectious esophagitis? Other causes?
Most common: candida albicans
Other causes: CMV, HSV, Varicella zoster virus, HIV, TB
8
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
9
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.
10
What is odynophagia highly suggestive of?
highly suggestive of infectious esophagitis
11
What is another name for infectious gastritis?
peptic ulcer disease
12
What are most cases of PUD associated w/?
H. pylori infections
13
Talk about the structure of H. Pylori.
short
spiral-shaped
microaerophilic
gram-neg.
urease +
bacillus
**colonizes gastric mucosa
14
What are the virulence factors of H. Pylori?
cytotoxic protein--vac A (vacuolating toxin)
CagA gene product
15
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
16
What is chronic H. pylori infections a risk factor for?
gastric tumors (lymphomas, adenocarcinomas)
17
What is involved in the diagnosis of H. Pylori PUD?
endoscopy
antigen tests (stool)
urea breath test
18
PUD often presents with pain where?
epigastric pain
19
Toxin-mediated food poisoning is primarily due to which 4 bacteria?
Staphylococcus aureus
Bacillus cereus
Clostridium perfringens
Clostridium botulinum
20
What is the typical incubation period of staph aureus?
1-8 hours
21
What are the signs & symptoms of food poisoning by staph aureus toxins?
N/V
abdominal pain
diarrhea
22
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.
23
What is the onset of staph aureus food poisoning like? Recovery?
abrupt onset, intense vomiting for 24-48 hours.
give fluids & electrolytes
24
What is the incubation period of bacillus cereus?
2-16 hours
25
What are the signs & symptoms of food poisoning by bacillus cereus?
N/V
abdominal pain
diarrhea
**shorter incubation period--mainly vomiting. Longer incubation period--mainly diarrhea
26
What is the epidemiology & pathogenesis of bacillus cereus food poisoning?
reheated fried rice
enterotoxin formed in food or gut from B. cereus growth
27
What is the incubation period of clostridium perfringens?
8-16 hours
28
What are the signs/symptoms of clostridium perfringens food poisoning?
abdominal cramping
watery diarrhea (abrupt onset, profuse)
**recovery w/i 1-4 days
29
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
30
What is the incubation period of clostridium botulinum?
18-24 hours
31
What are the signs & symptoms of food poisoning by clostridium botulinum? Diagnosis?
paralysis
diplopia, dysphagia, dysphonia, difficulty breathing
will need ventilatory support & antitoxin.
diagnosis--via seeing toxin in blood or stool
32
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
33
What is the most common cause of food poisoning in the US? Give the structure of this organism.
staph aureus
gram + aerobic coccus
34
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
35
WHat are the predominant symptoms in staph aureus food poisoning?
mainly vomiting, less diarrhea
36
Talk about the enterotoxins of staph aureus.
water-soluble
low-molecular weight
heat stable (resist boiling)
bind serotonin receptors in intestine
then serotonin binds receptors on vagal afferent neurons-->get vomiting.
37
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.
Diagnosis?
staph aureus food poisoning
38
What's the type of diarrhea experienced w/ staph aureus food poisoning?
not much of it
no WBCs or blood in it
39
TF Fever is a common feature of staph aureus food poisoning.
False. Fever is not a part of it.
40
What is the structure of bacillus cereus?
gram + aerobic rod.
41
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
42
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.
43
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.
Diagnosis?
Bacillus cereus food poisoning
from pre-formed neurotoxin
44
Talk again about the symptoms of B. cereus food poisoning.
N/V
no fever
diarrhea if it is there lacks WBCs or blood.
45
What is the structure of clostridium perfringens?
gram +
spore-forming rod
heat-resistant spores are made that can survive cooking
46
What are the symptoms of clostridium perfringens?
abdominal cramping
watery diarrhea (can last a while)
8-12 hrs after ingestion
47
Which dishes are clostridium perfringens often found in?
meat & poultry dishes
sauces & gravy
48
What does the C. perfringens enterotoxin do?
binds to the brush border membrane in the SI
messes w/ ion transport in ileum & jejunum
49
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.
50
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
51
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
52
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?
botulism
trivalent botulinum antitoxin
53
Review again the symptoms of botulism.
blurred vision
pupils fixed & dilated
dry mouth
constipation
abdominal pain
muscle weakness
flaccid paralysis
54
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
55
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.
56
What is the treatment for C. botulinum food poisoning?
gastric lavage
trivalent (A, B, E) botulinum antitoxin
57
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
58
T/F In non-inflammatory gastroenteritis, fecal leukocytes are found.
False. Noninflammatory. Same whether bacterial or viral cause.
59
What are some causes of viral gastroenteritis?
noroviruses
rotaviruses
adenoviruses
astroviruses
60
What is the structure of noroviruses?
naked single-stranded RNA-containing viruses
Caliciviridae family
61
When do you usu see norovirus gastroenteritis? Who do you usu see this in?
older children & adults
seasonal, winter vomiting disease. stomach flu.
62
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.
63
Why is it often hard to decontaminate infected cruise ships?
non-enveloped norovirus is resistant to decontamination
64
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
65
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
66
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.
67
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
68
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).
69
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.
Diagnosis?
rotavirus--gastroenteritis
n/v watery diarrhea
no leukocytes or blood in stool
oral rehydration is all that is really required, self-limiting.
70
What are some things that can be used to diagnose a rotavirus infection?
rapid antigen tests of stool
-enzyme immunoassay or latex agglutination test
71
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
True.
72
Describe the rotavirus vaccines available.
given at ages 2, 4, 6 months
rotatez & rotarix
73
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
74
Which of the E coli types that can cause E coli gastroenteritis can cause diarrhea in infants?
mainly ETEC
mild diarrhea--EPEC
75
What does ETEC colonize & which enterotoxins does it produce?
SI
LT (heat labile toxin). A-B toxin, causes increase in cAMP
ST (heat stable toxin) increases cGMP
**cause secretion of chloride & watery diarrhea
76
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.
Diagnosis?
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
77
Profuse and watery diarrhea suggests infection at which site?
SI
78
Absence of bloody stool means which type of diarrhea is less likely?
inflammatory diarrhea
79
What provides a definitive diagnosis of ETEC?
stool culture on MacConkey agar
assay for toxins by immunoassay or toxin genes w/ DNA probe
80
What is guiac a test for?
occult blood
81
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.
82
What is the bad result that can come from cholera?
rapid loss of H2O & electrolytes from GI tract, hypovolemic shock, metabolic acidosis, death
83
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.
84
What are some other species of vibrio that can cause similar symptoms to cholera?
V. parahemolyticus
V. vulnificus
85
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.
Diagnosis?
stool cultures on TCBS agar + for vibrio cholerae.
86
Which food is often associated with cholera? What is the treatment?
Food: often contaminated seafood
treatment: rehydration therapy, severe cases azithromycin or doxycycline
87
What is the main thing seen on presentation that tips you off to cholera?
rice water stool
88
Describe the structure of giardia lamblia.
flagellated protozoan
growing form: trophozoite
environemntal resistant form: cyst
89
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
90
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.
91
Incubation period of giardiasis? Symptoms?
10 day incubation period
crampy abdominal pain
smelly, watery diarrhea
flatulence
steatorrhea
**severe & chronic--malabsorption problems
**spontaneous recovery
92
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
93
Aside from giardiasis, give another cause of parasite diarrhea.
cryptosporidiosis
C. parvum is a coccidian parasite that is found in intestines of bunches of animals & is found in water
94
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).
95
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.
96
How much fluid loss is possible w/ an HIV pt w/ crytposporidiosis?
15L/day
97
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
98
How can you visualize C. parvum parasites?
stool smear w/ Kinyoun acid-fast stain to visualize
C. parvum is acid fast
99
What is the drug of choice for c. parvum infection if the patient isn't immunocompromised?
nitazoxanide
maybe some diarrheal agents too.
100
Which diseases are included in the category of inflammatory enterocolitis?
pseudomembranous colitis
bacterial dysentery
amebiasis (parasitic dysentery)
101
What are some organisms that can cause bacterial dysentery?
campylobacteriosis
E coli
shigellosis
salmonellosis
yersiniosis
102
Where do inflammatory enterocolitis diseases usu take place?
in the distal SI & colon
can invade surrounding tissues
103
Inflammatory enterocolitis has a distinguishing feature. what is it?
blood in feces
leukocytosis
104
Describe the structure of C. diff.
anaerobic
gram +
spore-forming rod
produces toxin A (enterotoxin) & toxin B (cytotoxin)
105
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
106
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
107
Once again, what are the symptoms of C. diff pseudomembranous colitis?
abdominal pain
low-grade fever
leukocytosis
blood in stool
108
Which antibiotics are commonly implicated in cases of C. diff?
clindamycin
cephalosporin
ampicillin
amoxicillin
109
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
110
What are some down the road implications of pseudomembranous colitis from C. diff?
toxic megacolon
bowel perforation
111
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
112
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
113
How should toxic megacolon be treated?
surgically resect the area of bowel that is affected.
114
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
115
What is tenesmus?
pain w/ defecation
116
What are some organisms responsible for bacterial dysentery?
Campylobacter jejuni
shigella
salmonella
yersinia enterocolitica
E coli (EIEC)
117
Describe the structure of campylobacter jejuni (a possible cause of bacterial dysentery).
motile
gram-neg.
S-shaped OR gull wing-shaped rods
paired rods
microaerophilic
118
Where do you find C. jejuni?
undercooked or raw meat
unpasteurized milk
nonchlorinated contaminated water
119
What are the 2 top causes of invasive dysentery?
1. salmonella
2. campylobacter jejuni
120
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.
121
What are the symptoms found w/ campylobacteriosis?
malaise
fever
abdominal cramps
tenesmus
bloody stools
fecal leukocytes
**superficial ulcers on bowel mucosa
122
What toxin does C. jejuni sometimes produce?
shiga toxin
a protein synthesis inhibitor
123
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
124
What is the treatment for C. jejuni infection?
oral rehydration
usu no antibiotics
azithromycin or ciprofloxicin if extreme.
125
What is a rare complication of campylobacteriosis?
post-campylobacter guillain-barre reactive arthritis
b/c endotoxin cross reacts w/ gangliosides found in CNS
126
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
127
Where do you find EHEC?
in the intestines of healthy cattle
you can eat bad meat
128
Which type of EHEC is the most common cause of hemorrhagic colitis & HUS?
EHEC serotype O157;H7
129
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
130
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.
Diagnosis?
EHEC confirmed by growth on MacConkey medium
**E coli infection, hemorrhagic colitis
131
WHAT CAN EIEC infection produce?
watery diarrhea
dysenteric stools (small volume, mucous-containing bloody feces)
132
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
133
Describe the features of HUS.
HUS is a microangiopathic hemolytic anemia marked by the appearance of thrombocytopenia, schistocytes, and azotemia
134
Describe the structure of E coli.
gram neg.
lactose-fermenting bacilli
135
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
136
What is the structure of shigella?
nonmotile
**non-lactose fermenting
gram-neg. rods
(closely related to E coli)
137
What is the most common species that causes shigellosis in the US?
shigella sonnei
138
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%
139
How do patients with shigellosis present?
fever
abdominal pain
diarrhea
dysentery
dehydration
**more severe in children
**often seen in closed population groups
140
What exactly does the shiga toxin do in shigellosis?
infect colon epithelial cells & inhibit protein synthesis
141
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
142
Is there a treatment that is contraindicated in patients with shigellosis?
antidiarrheal compounds
143
What is the structure of salmonella?
motile
lactose-non-fermenting
gram neg. bacilli
produce hydrogen sulfide
144
How can you distinguish E coli from salmonella or shigella?
E coli is lactose fermenting
Shigella & Salmonella are lactose non-fermenting
145
What exactly causes enteritis in salmonellosis?
serovars of S. enterica
146
What can typhi & paratyphi A serovars of S. enteric cause?
enteric or typhoid fevers
147
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
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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
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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
150
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
151
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
Diagnosis?
typhoid fever caused by salmonella typhi
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10-14 days after ingestion of salmonella, patients begin experiencing what?
fever
headache
myalgias
malaise
anorexia
persist for 1wk (bacteremic phase)
153
Where is the reservoir for salmonella in the body? What happens next?
reservoir is gallbladder
reinfection of the intestines w/ diarrhea
154
What is seen on the skin of patients infected with S. Typhi?
rose spots, skin lesions
155
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
156
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)
157
What are the 2 typhoid vaccines available in the US?
oral LAV
Vi capsular polysaccharide vaccine that is injected
158
Describe the structure of yersinia enterocolitica.
gram neg.
family of enterobacteria
zoonotic disease
injects yersinia protein kinase A & YOPE into eukaryotic cells.
159
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
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Most yersiniosis can be traced to what?
consumption of contaminated meat, milk, water
161
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.
Diagnosis?
yersiniosis
gram neg. rod
can see on cold enriched fecal cultures on CIN agar.
PCR can reveal y. enterocolitica
162
What is the treatment for yersiniosis?
usu self-limiting
can be treated by doxycycline & tobramycin
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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)
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What causes amebiasis? Important features?
entamoeba histolytica, a protozoan parasite
**causes dysentery
cyst form is infectious
liver common site of extra intestinal amebic disease
fecal-oral
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Which patients are at higher risk for amebiasis?
MSM
travelers outside US
recent immigrants
institutionalized populations
166
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
AMEBIASIS
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What is the treatment for amebiasis?
metronidazole or tinidazole
luminal agent--iodoquinol
168
WHat else is on the differential w/ patients who have amebiasis?
other causes of dysentery
inflammatory bowel disease
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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.
170
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
171
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
172
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
173
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
174
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
175
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
176
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
177
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
178
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
179
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
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