Maladies infectieuses Flashcards
What are the two main categories of infections?
Acute: a couple hours to a couple days
Chronic: over 2 weeks
What are the main causes of infections? (3+1)
- Bacteria
- Parasites
- Viruses
Sometimes mycoses… but not as common
What are the two main ways in which infections can be acquired?
- Ingesting contaminated food/water
- Transmission fécale/orale
What are the three main mechanisms in which infections work?
-
Invasive:
- Destroys enterocytes
-
Irritative:
- Destroys bordure en brosse (cell stays intact)
-
Toxic:
- Stimulated cellular secretions due to the presence of a toxin
What does Vibrio cholerae stimulate?
Stimulates secretion by enterocytes:
- Activate Cl CFTR canal –> causes a cascade… Na+ follow and then H2O
- Dim. Na+ absorption –> sort d’eau
- Inhibit NEH-2 and NEH-3 (échangeurs)
What does Vibrio cholerae cause?
Diarrhea which can lead to lethal levels of dehydration
Enterocytes can still absorb because toxins only target cellules sécrétoires
How does rotavirus work?
Inhibits the activity of disaccharidases on the bordure en brosse
Inhibits absorption through SGLT-1 transporters
How do bacteria/ZOT work?
Attack “jonctions serrées” and facilitates paracellular passage of toxins (agresseurs)
What are the most common clinical manifestations of infections?
Diarrhea (can be bloody)
Douleur abdocrampiforme
Fever
Vomiting
Which bacteria can cause bloody diarrhea? (4)
Shigella, Campylobacter, Salmonella, and E. Coli
What are the 4 kinds of viruses that can cause viral infections?
Rotavirus –> winter in temperate climates
Noravirus –> ex: Norwalk, during epidemics, or food poisoning
Adenoviruses
Astroviruses
Information about gastroentérite virale:
Transmission:
- Fécale/orale
- Aliments contaminés
- Respiratory system (??)
Short term and self-resolving
No examination for identification
Dx: clinical and épidémie
Information about viral colitis:
Can be documented if caused by something such as CMV (cytomegalovirus)
Most commonly in pts that are immunosuppressed
Tx: with IV Ganciclovir
What are the types of bacteria that cause food poisoning (toxins)? (3)
Staph. aureus
Clostridium perfringens
Bacillus cereus
What are the sx of bacterial food poisoning?
Diarrhea and vomiting
2-12 hours post-ingestion
Self-resolving in a couple hours
What bacteria can cause diarrhea that persists for over 48 hours?
Campuloacter jejuni
Salmonella
Shigella
When should you do a fecal examination? (4 reasons)
Severe diarrhea
Diarrhea for more than 3-4 days
Bloody diarrhea
Epidemics
- These tests don’t exclude a dx
- only 3% chance if finding smt
- Takes around 2-4 days to get a result
What bacteria can cause bloody diarrhea? (4)
Atteinte colique…
- Campylobacter
- Shigella
- Salmonella
- E. coli entéropathogène
What is Campyloacter jejuni ?
Contamination from?
Sx, Tx?
Gram - bacteria
Most frequent cause of bacterial enteritis
Contamination:
- Uncooked chicken
- Cross contamination
Sx: diarrhea w/ severe abdominal rxn
Tx: azythro or cipro (resistance starting to develop)
How can you contract Salmonella paratyphi ?
Contamination:
- Contaminated chicken
- Contact with exotic animals (turtles, lizards)
What is Salmonella typhi?
Rarer
Responsible for typhoid fever:
- Often without diarrhea
- Severe infection with fever (Typhoid fever)
- Abdominal pain with atteine Iléeale
- Hepatosplenomegaly
Salmonella in the vésicule biliaire:
Porteurs chroniques
Rechutes à l’occasion
tx: 4-6 semaines avec ATB –> essaye d’éradiquer
- cholécystectomie au besoin pour éradiquer la source d’infection
- usually in immunosuppressed patients
What is Shigella?
Very rare
It’s toxin is resistant to acid and very virulent which can cause epidemic eclosions
Risk factors?
- Epidemics
- Vacations
- Homosexual relations
What is E. coli O157:H7 (entérohémorragique)?
Toxine entéropathogène (shiga toxine)
Maladie de hamburger –> poorly cooked ground beef
Contamination:
- Ground beef contaminated with fecal matter (destroyed when cooked)
- Contaminated water
- Fruit and veggies washed with contaminated water
What does ECEH cause?
Bloody diarrhea (atteinte du colon transverse)
Can lead to “syndrome hémolytique urémique (SHU)”
- Hemolysis and vascular complications mostly In kidneys and brain (hémodialyse PRN)
ATB –> increase in shigatoxin release so DO NOT USE THEM as tx for ECEH
What is E. coli entérotoxigénique?
Different strain of E. coli that causes travellers diarrhea
- Activates intestinal adenylate cyclase ou guanylate cyclase
Usually lasts 24-72 hours and causes 3-6 BM a day
- If blood or fever… suspect another cause
Usually acquired in southern countries, Mexico, Antilles, India, etc..
Due to contaminated water/food washed with this water
Cannot be identified in fecal examinations
What is Yersinia enterocolitica?
Rare
Can present in two main ways:
- Acute: pseudo-appendicitis
- Chronic: mimic ileitis or ileocolitis (Crohns)
What is C. diff?
Can colonize the intestines –> asymptomatic
ATB can cause disequilibrium of flora which allows for proliferation and liberation of A OR B TOXINS –> TOXIC FOR GRÊLE AND COLON
Often quite severe and can be lethal
Called colite pseudo-membraneuse (CPM)
What are some C. diff risk factors?
- ATB use (quinolones)
- Hospitalisation
- IPPs –> not 100% sure
- Altered immunity
- Age
How is C. diff dx?
E/p and questionnaire +++
- Endoscopie: pseudo-membranes –> pathogneumonique for CPM
- Fecal examination but you must specify you’re looking for it
- Presence of bacteria is fine but its an issue if the toxin is present too
How is CPM tx?
Prevention:
- Use ATBs only when needed
- Importance of hygeine
- Use of probiotics
ATB to treat:
- metronidazole po or IV
- vanco po… IV will not get to intestines
- fidaxomicin
IF severe case:
- IV Immunoglobulins
- Fecal transplant
- Colectomie totale si réfractaire au tx médical
What is the main complication of “maladies infectieuses”?
Dehydration –> goal #1 is to rehydrate the pt
What is WHOs rehydration solution?
Oral rehydration therapy is a type of fluid replacement used to prevent and treat dehydration, especially due to diarrhea. It involves drinking water with modest amounts of sugar and salts, specifically sodium and potassium
Megacolon and perforation?
Rare complication that happens with more serious cases
Ileal perforation –> typhoid
Syndrome hémolytique urémique?
O157:H7
Hemolysis with atteinte vasculaire rénale/cérébrale
What is Reiter’s syndrome?
Immune rxn a couple weeks after enteritis
Leads to inflammatory arthritis (sometimes atteinte urétérale)
HLA-B27
ex: campylobacter, salmonella, shigella, and yersinia
What is Guillain-Barré syndrome?
Autoimmune manifestation in the PNS
After a campylobacter infection (usually)
What is Cyclospora?
Parasite
Epidemic –> infection alimentaire
Usually caused by travelling (ex: Nepal)
What is Giardia?
Most frequent parasite found in NA
Contamination:
- Contaminated water in the Rockeys and Adirondacks
- Preschools/daycares
- Trips to the south/nordic countries
What are Amibas?
Usually affect the colon
After trips to Africa and Asia
Dx:
- Fecal examination
- Colonic biopsies
What are some common amibas?
Entamoeba histolytics: pathogen –> requires tx
E. gingivalis, E. hartmanni, E. coli, E. dispar: not pathogens
How are amoebas tx and what are the main complications?
Tx: metronidazole 1-3 weeks
Complications:
- Hepatic abcesses (fever, douleur abdo HCD, bilan hépatique perturbé)
- Echo helps with identification
What are the most frequent chronic parasite infections? (3)
- Giardia lamblia
- Entamoeba histolytica
- Blastocystis hominis
What is Candida albicans?
Flore intestinale ou fécale normale
Aucun rôle pathogène au niveau du grêle/colon mais pathogène dans l’oesophage
What is intestinal tuberculosis?
Cause:
- Swallowing contaminated pulmonary secretions
- Ingesting infected foods (such as cows milk)
Clinical presentation: inflammation of distal ileum
Quite rare in industrialized countries
What is sprue tropicale?
Clinical presentation: diarrhea and malabsorption
Histology: partial atrophy of villosities (similar to celiacs)
Dx to consider mostly in endemic countries
Tx: tetracycline with folic acid
No identifiable pathogen
What is Whipples disease?
Caused by Tropheyma whipplei (gram +)
Classic presentation: digestive sx (diarrhea, weight loss, abdominal pain) with arthralgia
How is Whipples dx and tx?
Dx: duodenal biopsies
- Atrophie vollositaire avec infiltration de la lamina propria par des organismes qui se colorent au PAS
Tx: ATB for many months
Flore intestinale normale:
Tube digestif est stérile à la naissance mais colonisé par bactéries maternelles et alimentaires (36 000 espèces)
4 main groups of bacteria:
- Firmicutes
- Bacteroidetes
- Proteobacteria
- Actinobacteria
What is the role of intestinal flora?
Energy: metabolize sugar/fibre in the colon
Digest exfoliative epithelial cells
Probiotics and prebiotics were developed to foster these roles
How to protect host from infection or too many bacteria?
pH of gastric acid
Bile salts in the small intestine
Peristalsis
- Phase 3 allows stomach and intestine to get rid of extra bacteria
- If not working properly –> pullation actérienne intestinale
What is bacterial overgrowth (pullulation)?
Increase in the normal bacteria found in the GI tract
- 10 ^5 bacteria/ml
- Anaerobic bacteria
Not due to the proliferation of a pathogen
How is malabsorption linked to overgrowth?
Deconjugation of bile salts –> stops formation of “micelles” which prevents absorption of lipids and liposoluble vitamins
Atteinte inflammatoire de la muqueuse –> irregular villosities, deficit in dissacharidases
Consume B12, carbohydrates, and protein
What pathologies are responsible for overgrowth?
Stenosis: empêche transit normal
Formation sacculaire/segments exclus (ex: diverticulose ou chx) –> harder to clean
Problem with peristalsis
Déversement exagéré de bactéries
How is overgrowth dx?
Clinical presentation: diarrhea, malabsorption, weight loss, bloating, discomfort
Gold standard: aspiration of duodenal liquid (quite hard)
So instead… tests indirects fonctionnels
- Bile salts marked with C13 or C14 –> pic d’excretion at 1-2 hours instead of 3-5 post-ingestion
- Lactulose –> pic d’hydrogène at 1-2 hours instead of 3-5 post-ingestion
How is overgrowth tx?
Correct the reason for why its happening and
Decrease intestinal bacteria with ATB: alternance et intermittence (not a bunch all at once for a long time)
