GI Flashcards
Duration of GI symptoms
- acute: < 14 days
- persistant: < 30 days
- chronic: > 30 days
GI anatomic considerations
- esophagus to stomach to small intestine to large intestine
- pH of stomach can withstand most bacteria
- peristalsis of small intestine inhibits adherence
- colon flora and IgA compete with pathogens
GI risk factors
- number of ingested organisms
- achlorhydia
- reduction in normal flora due to antibiotics
Traveler’s diarrhea
Enterotoxigenic E. coli
Parasitic infections
Giardia, Entamoeba
Antibiotic-associated diarrhea
C. difficile
Practical diagnosis
- History (food ingestion, travel, activities)
- Duration of illness
- Medications
- Underlying conditions
- Physical exam (state of hydration, exam of abdomen)
- Laboratory studies
- Fecal exam
Direct fecal smear
- Gram stain of smear
- WBC’s indicate invasion, not toxin
Enterotoxin-mediated diarrhea
- rapid onset indicates preformed toxin
- lack of fever
- absence of blood or pus
- large number of watery stools (> 20/day)
- Enterotoxigenic E. coli, cholera, S. aureus, C. perfringens, Bacillus cereus, viral or parasitic
Diarrhea mediated by invasion of bowel mucosal surface
- fecal leukocytes, RBC’s, fever
- Salmonella, Campy, Shigella, E. coli, Entamoeba
Diarrhea mediated by invasion of full thickness of bowel with lymphatic spread
- S. typhi, Y. enterocolitica
- presents with constipation
- fecal leukocytes and RBC’s
Common viral pathogens
Norovirus, Rotavirus, Adenovirus,? Some Enterovirus
Common bacterial pathogens
Salmonella, Shigella, Campylobacter. E coli, Yersinia, Clostridium difficile
Common parasitic pathogens
Giardia intestinalis, E. histolytica, Cryptosporidium, Cyclospora, Microsporidia
common protozoa
Giardia, Cryptosporidium, Entamoeba
common toxins associated with GI
Staphylococcal, Bacillus cereus, Cl botulinum, Cl perfringens, Scrombotoxin
- most common cause of diarrheal illness worldwide
- microaerophilic, Campy BAP, 42C
- seagull wing appearance, darting motility
- oxidase +, catalase +
Campylobacter jejuni
- contaminated meat, eggs
- symptoms 6-8 hours after ingestion
- usually self-limiting
- indole -, K/A H2S +, oxidase -
- enteric fever
- high inoculum required
Salmonella typhi
how many salmonella organisms need to be ingested for infection?
need around 1000 organisms per g of food to get infected
- dysenteriae, flexneri, boydii, sonnei
- sonnei is most common in US
- non-motile, oxidase -
- causes dynsentery
- low inoculum required
Shigella
- infantile diarrhea
- adhesive, mucus in stool (no blood)
Enteropathogenic E. coli
- Traveler’s diarrhea
- due to poor sanitation
- requires large inoculum
- releases toxins
Enterotoxigenic E. coli
- dysentery with direction invasion/destruction of mucosa
- similar to Shigella, but higher inoculum
- watery diarrhea with blood, mucus and WBCs
Enteroinvasive E. coli
- rice-water stool
- large loss of electrolytes
- associated with epidemics
- catalase +, oxidase +
- toxin produced
- yellow on TCBS
Vibrio cholera
- Summer diarrhea in Japan, associated with seafood
- diarrhea and cramping
- green on TCBS
Vibrio parahaemolyticus
- “lactose positive” species
- raw or undercooked seafood, wounds
- green on TCBS
Vibrio vulnificus
- grows at 4C, can go septic
- meat, unpasteurized milk, dairy products
- CIN agar (target growth)
- K/A, ODC +, non-motile
- self-limiting, possible invasion of mesenteric lymph nodes
- sometimes mistaken for appendicitis
Yersinia enterocolitica
- sometimes normally in intestines
- antibiotic-associated diarrhea
- pseudomembranous colitis
- mild to severe disease
Clostridium difficile
- deli meat
- grows at cold temps
- CAMP +, catalase +, tumbling motility
- premature labor, spontaneous abortion
Listeria monocytogenes
- peptic ulcers
- stomach cancer
- urease +, Christensen’s urea medium, urea breath test
- cinaedi and fennelliae associated with diarrhea
Helicobacter pylori
STD’s causing GI infections
- cause proctitis with lose stools and pain on defecation
- N. gonorrhoeae, Chlamydia, Treponema
Toxic agents of Food Poisoning (chemical)
- scombroid: flushing, headache, crampy abdominal, tissue of fish
- Ciguatera: red tide toxin buildup in fish, diarrhea, weakness, abdominal pain
- Tetrodotoxin: puffer fish toxin (death in 50%)
Preformed toxin from food borne disease?
S.aureus, B.cereus,Cl botulinum, scrombotoxin and paralytic shellfish poisoning
Toxin production in vivo from food borne disease?
C perfringens, B.cereus, Enterotoxigenic E.coli
Tissue invasion in food borne disease?
C.jejuni, Salmonella, Shigella, VTEC
when are the peaks of food borne disease during the year?
Peaks at Christmas (eat too much) and summer (BBQ)
HE plate
- Salmonella shows H2S (black colonies)
- Shigella has no H2S
SMAC
E. coli O157:H7 doesn’t ferment sorbitol
Campy agar
selective for Campylobacter jejuni
CIN agar (cefsulodin- Igrasan-novobiocin)
selective for Yersinia enterocolitica (target/bulls-eye growth)
TCBS agar
- Vibrio cholera and alginolyticus utilize sucrose (turn yellow)
- Vibrio vulnificus and parahaemolyticus don’t utilize sucrose
CCFA agar
selective for C. difficile (pale yellow colonies - fluoresce bright yellow)
Diarrhea treatment and prevention
- replenish electrolytes (IV fluids if necessary)
- antidiarrheal medications (not for invasive diarrhea)
- antibiotics to treat infection
incubation period of norovirus?
Usually 24 to 48 hours
common clinical features?
Vomiting, diarrhoea, fever
diagnosis?
EM, PCR
how is norovirus transmitted?
Person to person by the faecal oral route
how can vomiting transmitted the virus?
risk of infection from aerosols of projectile vomit.
how does norovirus contaminate the environment?
especially of toilets; gloves should be used by cleaners. Contaminated food and water, especially bivalve molluscs.
how many organisms does it take to infect a person?
2-3
what is the incubation period of rotavirus?
Approximately 48 hours.
what are the clinical features?
Diarrhoea, vomiting.
diagnosis?
ELISA, EM
transmission?
Person to person by faecal oral route by environmental contamination
significant characteristic of the viruses?
Enveloped viruses
whats the incubation period of a E coli O157 infection?
1 to 10 days.
what does a diagnosis require?
Culture/serotyping/ toxin detection (serology)
what is the Reservoir of e coli O157?
The gastrointestinal tract of cattle and possibly other domesticated animals
how is the infection transmitted?
Contaminated foodstuffs - beef and beef products (for example, undercooked beefburgers), milk, and vegetables have been associated with cases or outbreaks.
Contact with infected animals, particularly on farms or in animal sanctuaries.
can it be spread from person to person?
Person to person spread can occur by direct contact (faecal oral), particularly in households, nurseries, and infant schools.
what complications are associated with infection?
HUS, Haemorrhagic colitis
what is the incubation period of Shigella species infections?
1 - 7 days
how is a infection diagnosed?
culture
how is it transmitted?
Faecal oral from cases with diarrhoea, in households, and institutions, mainly those containing young children. Occasionally spread by food and water.
which species is endemic in UK and wales?
S. sonnei
causing mild illness
which species originate outside of UK?
S. boydii and S. dysenteriae, and most S. flexneri
how do they present clinically?
as dysentery (diarrhoea with blood, mucus, and pus).
what is S. dysenteriae may be associated with?
serious disease, including toxic megacolon and the haemolytic uraemic syndrome
what is the incubation period of Cryptosporidium?
2-5 days
what are the reservoirs of cryptosporidium?
Gastrointestinal tract of man and animals, particularly farm and other domesticated animals. Water contaminated with faeces.
what are the two main genotypes of transmission?
parvum and hominis
what is the parvum transmission?
Contact with infected animals. Outbreaks have been associated with public water supplies and contaminated food.
Seasonal outbreaks are associated with farm visits to feed and handle lambs.
what is the hominis transmission?
Person to person spread, particularly in households and nurseries. Infection through swimming pools has been reported.
what is the incubation period for Giardia lamblia infection?
5-25 days
how is the infection transmitted?
Person to person. Foodborne transmission is rare.
Faecal oral in young children. Waterborne. Spread within families is common
Gram positive, anaerobic bacillus
Clostridium difficile
what is the main transmission mode of clostridium difficile?
Subterminal spores
how are the spores spread?
Patient to patient
Spread via hands of HCWs
Spread via environment
Transmission from asymptomatic patients unlikely
how do the spores survive in any environment?
resistant to heat, air and drying
how many toxins do clostridium difficile produce?
two, toxin A and B
toxin A?
loss of fluid from gut mucosa
toxin B?
potent cytopathic toxin
where does the infection affect?
Predominantly affects the colon
how does it present clinically?
Abdominal pain, explosive, watery, foul smelling diarrhoea, fever
Variable severity
what complication is common?
Recurrence after successful treatment is common
May have long period of excretion
when do you test for infection?
All adult inpatients with diarrhoea
Other risk groups
- children
what used to be the gold standard for diagnosis?
Demonstration of toxin in stool by cell culture – overnight incubation required
what other diagnostic tests are available now?
“sniff” test
Commercial ELISA (sensitivity 75-95%)
culture/ribotyping for epidemiological studies
Glutamate dehydrogenase detection + toxin detection
what must be remembered when using the diagnostic tests?
do not rely on one false negative
what groups of people are susceptible?
old and young
people with antibiotic treatment
what Underlying diseases could help infection?
Surgery due to prophylactic antibiotics given before surgery
Cancer patients coz immunosurpressed
chronic renal disease
how can infection be prevented?
Control of antibiotic usage
Handwashing
Cleaning/disinfection/sterilisation of equipment
Environmental cleaning
how can outbreaks be controlled?
Isolation of cases and cohort nursing
Antibiotic treatment of cases
Management of relapses
Abrupt onset of nausea, vomiting, cramps and prostration
Staphylococcal food poisoning
what is the incubation period of staphylococcal?
1-6hrs
what are the diagnosis requirements?
Culture/enterotoxin detection in faeces and food(>10^5/g)
what is the reservoir of the bacteria?
Contamination of ready to eat food from hands of food handler, followed by temperature abuse
what disease does Bacillus cereus cause?
emetic syndrome
diarrhoeal syndrome
incubation period of emetic syndrome?
1 to 5 hours
incubation period of diarrhoeal syndrome?
8 to 16 hours
how can it be diagnosed?
Culture (Food and faeces)
what are the reservoirs?
No human or animal sources. Environment: soil, sediments, dust, vegetation and Food
what food is commonly infected?
mainly rice dishes; occasionally pasta, meat or vegetable dishes, dairy products, soups, sauces, sweet pastry products.
how is the bacteria transmitted to humans?
Contaminated cooked foods subjected to inadequate post-cooking temperature control during cooling and storage.
Prodromal fever, headache, abdo pain, D for 1-2 weeks
Campylobacter sp
what is the most common cause of Campylobacter sp infection?
food poisoning
why are there vary in age distribution
20-49 more likely to eat out, take out, BBQ. More risk
how many cases do the Infectious Intestinal Disease Survey (England) record annually?
9,500,000
For every 136 cases in the community
how many present to GP?
23
how many have a faecal sample tested?
6
how many have a pathogen identified?
1.4
how many is reported to CDSC?
1
three main sources of intestinal disease annually?
Pecked doorstep milk
Foreign travel
Diarrhoeal dogs (32% positive)
contamination in shop?
Cross contamination in retail premises
2/1132 cleaning cloths positive
how can domestic kitchen hygiene go wrong and risk contamination
kitchen less than 2m in length
kitchen work surface less than 1m long
more than 3 hrs shopping to fridge
storing meat in top half of fridge
no separate chopping board for meat
what is the incubation period of Giardia lamblia?
5 to 25 days.
how is an infection diagnosed?
Light microscopy
what are the reservoirs of bacteria?
Gastrointestinal tracts of people and animals.
how is the infection transmitted?
Person to person.
Foodborne transmission is rare.
Faecal oral in young children. Waterborne.
Spread within families is common.
what is the live form of the bacteria?
Giardia trophozoite
what form is more common to see on microscopy?
Giardia cyst
why cysts more common?
Cysts resist standard chlorination
