GI infections (3) Flashcards
list the GI tract infections we are expected to know
- C. difficile
- gastroenteritis/travellers diarrhea
- rotavirus
- hepatic abscess
- H. pylori related infections
- esophagitis
what is the #1 etiologic cause of antibiotic related diarrhea
C. difficile
96% of C. diff infections are antibiotic related
how is C. difficile transmitted
fecal oral
how can a C. difficile infection present
- asymptomatic colonization
- mild-moderate diarrhea
- severe pseudomembranous colitis
what is a pseudomembrane
a layer of exudate resembling a membrane, formed on the surface of the skin or a mucous membrane
what is pseudomembranous colitis
C. difficile infection
what antibiotics can cause C. difficile?
which are the most risky?
all antibiotics can cause C. difficile
most risky = CLINDAMYCIN and CIPROFLOXACIN
lincosamide and fluoroquinolone
what are the toxins associated with C. diff, and what type of toxin are they
toxin A and toxin B
A = enterotoxin
B=cytotoxin (more potent)
how does C. difficle cause disease
colonization of the colonic mucosa–> antibiotic therapy (disruption of normal intestinal flora)–>C. diff releases toxin A and toxin B–> mucosal injury and inflammation–> C. difficile colitis
what is the J strain of C. diff
epidemic CLINDAMYCIN RESISTANT strain
what is the NAP1/B1/027 strain of C. diff
emergent virulent strain
produces more toxins A and B, have higher recurrence, less clinical cure
FLUOROQUINOLONE resistance
how long after Ab Tx does C. diff present
during Ab Tx or within 2 weeks
what type of diarrhea does C. diff cause
watery
> 3 stools/day
describe the clinical presentation of C. diff
watery diarrhea
elevated WBCs
60% have unexplained leukocytosis
low grade fever
what is fulminant colitis
can arise as a result of C. diff infection
“toxic megacolon”
abdominal pain, distention, lactic acidosis, hypovolemia, high WBC, may NOT have diarrhea, pseudomembranes
URGENT SURGICAL EVAL
Tx of C. diff (protocol)
- Assess (vital signs, abdo exam, hydration; CBC, chemistry)
- contact precautions
- STOP: all possible antibiotics, proton pump inhibitors, all anti-diarrheal agents
Tx of C. diff (meds)
- mild-moderate disease–> METRONIDAZOLE
reassess after 4-6 days and if not improved, add oral VANCOMYCIN - severe disease or recurrence–> oral VANCOMYCIN
reassess in 4-6 days and if not better add METRONIDAZOLE
always: monitor patients closely, use ORAL vancomycin, contact GI, ID and surgery in severe disease
what % of returning travellers get travellers diarrhea
30-70%
is most travellers diarrhea viral or bacterial
bacterial
what are the most common etiologic agents of travellers diarrhea
- ETEC
- Enteroaggregative E. coli (EAEC)
- campylobacter jejuni
- Salmonella spp
- Shigella spp
would you suspect intestinal helminths in a returning traveller with diarrhea?
not usually as most are asymptomatic and wouldn’t cause travellers diarrhea as much as a bacterial cause would
what would you suspect as the etiologic agent in travellers diarrhea with the following presentations:
- acute onset
- gradual onset or chronic low grade diarrhea
- bloody with fever
- brief episode of vomiting and diarrhea resolving within 12 hours
- bacterial or viral
- protozoa (giardia or entamoeba histolytica)
- (dysentery) shigella, campylobacter or salmonella
- ingested toxin (food poisoning)
though its usually not necessary to ID the pathogen in traveller’s diarrhea, when you need to, how do you do it?
- stool culture for immunocompromised patients or in outbreaks, or with dysentery presentation–> can ID shigella, campylobacter, salmonella
- CANT distinguish ETEC/EAEC from nonpathogenic E. coli and cant ID viral causes - stool microscopy (“ova and parasites”)
- for giardia, cyclospora, entamoeba, microsporidia, cryptosporidia
- order for symptoms lasting more than 10 days - direct fluorescent antibody (DFA)/ enzyme immunoassay for giardia and cryptosporidium
would you or would you not use anti-motility agents with dysentery
NO
use anti motility agents only with Abs
what is the leading cause of acute diarrhea in children
rotavirus
responsible for 40% of hospital admissions worldwide
what are the largest factors in diarrheal deaths?
unsafe water
inadequate sanitation
poor hygiene
where do most diarrhea deaths occur
Africa
South Asia
how many rotavirus particles are required for infection
10
what is the most common age affected by rotavirus
6-24 months
babies are protected by IgA in breastmilk
how do you diagnose rotavirus
ELISA or latex agglutination or PCR
how do you treat rotavirus
ORS
Zinc
continued breastfeeding
how do you prevent rotavirus
ROTARIX vaccine
2 doses at 2 and 4 months
do hepatic abscesses usually present with bowel symptoms
no, often present without
what is the most likely organism causing amoebic liver abscess
entamoeba histolytica
or E. dispar
how do you distinguish between E. histolytica and E. dispar as the cause of an ALA?
their cysts are indistinguishable on microscopy
E. histolytica can have ingested RBCs whereas E. dispar doesn’t
E. histolytica have invasive disease (liver, intestine, lung, brain) whereas E. dispar is asymptomatic colonization
which is more common in the developed world, ALA or bacterial liver abscess
bacterial
what is the source of ALA infection? bacterial liver abscess?
ALA = 100% hematogenous
bacterial = biliary (60%), hematogenous (20%) and other like trauma, iatrogenic, extension
what is the aspirate like in ALA? in bacterial?
ALA = brown, no odor, “anchovy paste” quality
bacterial = purulent, green/yellow, foul odor
what organisms cause bacterial liver abscesses
- E. coli
- Klebsiella
- Strep
- enterococcus
- bacteroides
often polymicrobial
what are serology results for ALA? bacterial liver abscecss?
ALA = + bacterial = -
Tx for ALA
- METRONIDAZOLE
2. paramomycin/iodoquinol
Tx for bacterial liver abscess
empiric coverage for enteric GNRs, enterococcus, anaerobes
what is the most common cause of gastritis
H. pylori related infections
what is the most common chronic bacterial infection in humans
H. pylori related infections
what causes 90% of duodenal ulcers
H. pylori
how is H. pylori transmitted
fecal-oral and oral-oral
what bacteria increases the risk of gastric cancer
H. pylori
pathophysiology of H. pylori infections
bacterial UREASE hydrolyzes urea –> NH4
NH4 neutralizes stomach acid
SPIRAL shaped, flagella, and MUCOLYTIC enzymes of H. pylori allow it to “swim” through mucous to epithelium
ADHESINS bind to epithelial receptors
who do you test for H. pylori
anyone with:
gastric cancer
active PUD
of Hx of PUD
anyone with symptoms of dyspepsia
what tests do you use for H. pylori
- urease breath test (really sensitive and specific)
- serology (ELISA, IgG)
- stool antigen (less accurate)
- endoscopy and biopsy (for urease, histology and culture)–> do in older patients with “danger signs”
Tx of H. pylori
HP-Pac–> Lansoprazole + clarithromycin + amoxicillin (14 days)
20% of pts fail first Tx
what is the primary HIV opportunistic infection when CD4 cell count falls below 200
thrush
how do you treat oropharyngeal candidiasis
NYSTATIN rinse
clotrimazole troches
ARVs if HIV+
fluconazole
what is esophageal candidiasis
esophagitis
usually with thrush
HIV or other immunosuppresion = comorbid
Tx of esophageal candidiasis
always SYSTEMIC antifungals
empiric Tx same in immunocompromised as competent
FLUCONAZOLE
echinocandins
amphotericin B
what are GI infections usually caused by?
usually due to ingestion of a pathogen or toxin that either localizes to the gut or disseminates beyond
can also be caused by disruption of normal gut flora, gut architecture or host immune system
what causes most travellers diarrhea
ETEC or EAEC
usually doesnt require diagnostic tests or antibiotics
is liver abscess serious?
YES
it is a serious condition that requires prompt hospitalization, CT scan, empiric Ab therapy to cover ENTERIC GRAM - RODS, ENTEROCOCCUS and ANAEROBES
most common cause of bacterial liver abscess
biliary tract obstruction or infection
how does most entamoeba present?
usually asymptomatically
how does E. histolytica usually present
can be locally invasive and disseminate (i.e ALA)
who requires an evaluation for immunosuppresion on presentation with thrush
patients older than 12 months old
