GI infections Flashcards
ACUTE DIARRHEAL ILLNESS
One of the most common problems evaluated by clinicians
> Transmitted via ingestion of contaminated food or beverage
Clinical Manifestations
> In healthy individuals
- A self-limiting illness, lasting only a few days
> Some people experience chronic symptoms
Some may develop more serious symptoms
- Bacteremia
- Dehydration
- Serious sequelae - Malnutrition, severe dehydration, death
EVALUATING GI INFECTIONS
Diarrhea - An alteration in normal bowel movement
characterized by an increase in the water content,
volume, or frequency of stools
more than three bowel movements/day
Clinical History
point to a causative diagnosis
> Most infections are acquired by ingesting the offending microorganism
- An important component is dietary history
> Other important aspects to consider
- Recent travel history
- Recreational activities
- Seasonality
- Daycare attendance
- Living conditions
Clinical History - Key Questions
> What is the duration of symptoms?
> Are there associated symptoms of inflammation?
> Does the patient have a history of previous GI symptoms?
> Does the patient have an underlying illness?
> Is the patient taking any medications?
- A recent history of antibiotic use may also suggest an
infection with Clostridium difficile
CONSIDERATIONS FOR DIAGNOSIS
Chronicity of disease
Possibility of viral, bacterial and parasitic pathogens involvement
Causes of diarrhea
> Preformed toxins
> Numerous noninfectious cause
- laxative use
- tumor-related
- malabsorption
- inflammatory bowel diseaseAnatomic Related Host Defenses
> Stomach acidity (pH of lower than 4)
- Kills more than 99.9% of coliform bacteria within 30 minutes - However some pathogens are resistant
> Small intestine
- Peristalsis movement prevents adhesion of some bacteria to the
intestinal wall ( if there isnt movement bad bacteia can attach )
> Colon
- Normal flora compete with potential pathogens for nutrients and
attachment space
> Immunoglobulin A (IgA) - antibody secretion by colon and small intestine that may have an effect on potential pathogens
risk factors
> Number of ingested organisms
- Median infectious dose (ID50) - Number of organisms required that
must be ingested to cause disease in 50% of exposed individuals
> Achlorhydria - absence of hydrochloric acid in gastric secretion
- Cause inadequate stomach acidity
- More likely to develop illness
> Reduction in normal flora
- Antibiotic exposure alters gut flora and increases the chance of
infection by an enteric pathogen
common normal flora
lots of normal flora
- gram stain wont be helpful in ID of pathogenic bacteria
bacteroides fusobacterium lactobacilli clostridium peptostreptococcus s. aureus enterococcus strep e.coli q
common pathogens
campylobacter salmonella shigella clostridium difficile yersinia enterolictica entamoeba histolytica cryptosporidium gardia lamblia
common pathogen food sources
chicken eggs milk water fried rice
fish
diagosis : patients history
> Traveler’s Diarrhea
- Enterotoxigenic Escherichia coli (ETEC)
- Contaminated food and water consumption
> Parasitic infections - possibly linked to travel
- Giardiasis
- Entamebiasis
> Recent/current Antibiotic treatment - associated with Clostridium difficile infections
> Duration of illness
> Medications
- Can cause GI upset
history of medical condition
IBS , Malabsorption, chemo
laboratory results may assist with diagnosing the GI infection
- Leukocytosis
- Anemia
- Thrombocytopenia
- Electrolyte abnormalities
- Fecal examination (invasive vs toxigenic disease)
- RBCs
- Fecal leukocytes (inflammation)
- Fecal lactoferrin
- Neutrophil marker associated with inflammation
Gram Stain of Direct Fecal Smear
large # of WBC indicates an inflammation
- means an invasive infection/ disease usually NOT enterotoxin
Enterotoxin mediated diarrhea symptoms
- Rapid onset of diarrhea (Less than 12 hours)
- Lack of fever
- Absence of blood or pus
- Large number of watery stools (Sometimes more than 20 per day)
causes of enterotoxin- mediated diarhhea causes
bacterial
- ETEC
- Vibrio cholerae
- staph aureus
- clostridium perfringes
- bacillus cereus
other types ( viral & parasitic ) can be similar but symptoms last longer
diarrhea mediated by invasion of bowel mucosal surface
symtoms
inflammatory response
- fecal leukocytes
- rbcs
- fever sometimes
causes of diarrhea mediated by invasion of the bowel mucosal surface
salmonella
campylobacter spp
shigella
E.coli
Entamoeba histolytica
diarrhea mediated by invasion of the full bowel thickness and lymphatic spread symptoms & causes
symptoms - usually constipation
- fecal leukocytes and rbcs
- bacteremia
- often mimics appendicitis
causes
- salmonella typhi
- yersinia enterocoloctica ( mimics appendicitis )
viral pathigens of infectious diarrhea
rotavirus - generally children under 5
enteric adenovirus
- serotypes 40& 41
caliciviruses
- norovirus ( cruise ship outbreaks)
- sapovirus
astroviruses
- old or very young
what is the most common cause of gastroenteritis in the world
campylobacter jejuni
bacterial pathogens for infectious diarrhea
c.jejuni
- most common cause of gastroenteritis
salmonella spp
- gastroenteritis and food posioning
s.typhi- enteric fever
shigella spp.
vibrio cholera and non cholera spp
yersinia enteolitica
c.diff
listeria monocytogenes
h. pylori
aeromonas
edwardsiella
what causes a major infection even at a low inoculum
shigella
what is often mistaken for appendicitis
yersinia
what causes antiobiotic associated diarrhea
clostridium difficile
what is associated with peptic ulcers
h.pylori
associated with fish and shellfish
edwardsiella
sexually transmitted disease causing GI disease
Neisseria gonorhoea
chlamydia trachomatis
treponema pallidium
herpes simplex virus ( HSV)
parasitic pathogens
gardia lamblia
E. histolytica
cryptosporidium
specimen handling and
preservative
fresh specimens or properly preserved for ova and parasite detection
what are 2 seagull wing appearing bacteria
campylocbacter
and vibrio
