Micro 8 (GI infections pt 1)

staphylococcus aureus characteristics

gram positive cocci in grape-like clusters

staphylococcus aureus associated disease

food poisoning

staphylococcus aureus virulence factors

enterotoxins A-E (bacteria can be killed with heat, but the toxins will not)

staphylococcus aureus food poisoning modes of transmission

ingestion of enterotoxins

staphylococcus aureus food poisoning symptoms

severe vomiting, cramps, and diarrhea (some cases)

staphylococcus aureus food poisoning prevention

enterotoxins associated are heat stable, so avoid foods like mayo-based potato salad that has been out in the sun

staphylococcus aureus food poisoning treatment

antibiotic

staphylococcus aureus lab characteristics and diagnosis

catalase positive, yellow growth on mannitol salt agar

bacillus cereus characteristics

gram positive spore-forming rod in boxcar-like arrangement

bacillus cereus associated disease

gastroenteritis (food poisoning)

bacillus cereus virulence factor and MOA

enterotoxins (heat labile) increase cAMP, causing profuse watery diarrhea

bacillus cereus transmission

ingestion of enterotoxins, typically from rice (emetic type) or meat and vegetables (diarrhea type)

bacillus cereus gastroenteritis symptoms (for emetic and diarrhea types)

• emetic type = rapid onset vomiting/cramps

• diarrhea type = watery diarrhea

bacillus cereus gastroenteritis prevention

heating up food properly and refrigerating food properly

difference between food poisoning caused by staphylcoccus aureus and bacillus cereus

staph aureus enterotoxin is heat stable (not killed with heat), whereas bacillus cereus enterotoxin is heat labile (can be killed with heat)

escherichia coli characteristics

gram negative rods

escherichia coli associated diseases

• enterotoxigenic E coli (traveler’s diarrhea) (ETEC)

• enterohemorrhagic E coli (EHEC)

ETEC virulence factors

LT1 (heat labile, increases cAMP) and STa (heat stable, increases cGMP) enterotoxins

ETEC transmission

ingestion of enterotoxins from infected water and foods washed with that water

ETEC symptoms

explosive, sudden onset watery diarrhea, abdominal cramps, fever, (nausea/vomiting some cases)

EHEC virulence factors

Stx1 and Stx2 shiga-like toxins encoded by phage (5B subunit binds to kidney and intestinal cell receptors on 28SrRNA, 1A subunit disrupts protein synthesis)

EHEC transmission

fecal-oral from cattle, goats, and/or sheep GI tract

EHEC symptoms and complications

• starts with watery diarrhea, progresses to profusely bloody diarrhea with severe stomach cramps and NO FEVER

• hemorrhagic colitis and hemolytic uremic syndrome (HUS)

EHEC prevention

avoid/use caution around alfalfa sprouts, unpasteurized milk/juice, PETTING ZOOS, lettuce, spinach

escherichia coli lab characteristics

pink on macconkey agar, metallic green colonies on EMB agar, glucose fermenter, lactose fermenter, catalase positive, oxidase negative

salmonella enterica typhi associated disease

typhoid fever

salmonella enterica enteritidis associated disease

enteric infections with diarrhea

salmonella enterica and salmonella bongori associated disease

salmonellosis (yes both strains cause this disease)

salmonella strains (enterica and bongori) characteristics

gram negative rods

typhoid fever transmission and MOA

fecal-oral (only from human feces); bacteria spread from small intestine to macrophages, lymphoid tissue, liver, and gallbladder by targeting Peyer patches on M cells

salmonellosis transmission and MOA

ingestion of contaminated food/water; bacteria multiply and invade the intestinal mucosa by targeting Peyer patches on M cells, destroying M cells, and replicating in phagocytic cells

typhoid fever symptoms

fever, headache, abdominal pain, CONSTIPATION, anorexia, malaise, CHARACTERISTIC ROSE SPOTS on abdomen

salmonellosis symptoms

diarrhea w/ mucus (maybe blood), fever, abdominal cramping

salmonellosis prevention and treatment

• avoid raw eggs

• prevent dehydration by drinking lots of fluids and electrolytes

salmonella enterica is found in (1) while salmonella bongori is found in (2)

1. humans and warm-blooded animals

2. cold-blooded animals

salmonella strains lab characteristics

lactose nonfermenter, catalase positive

shigella strains (s. sonnei, s. flexneri, s. boydii, s. dysenteriae) characteristics

gram negative rod

shigella strains associated diseases

shigellosis, bacillary dysentery

shigella strains toxin and MOA

shiga toxin (1A-5B subunuts that cleave 28srRNA to inhibit protein synthesis)

shigella strains transmission

fecal-oral (requires very small infective dose)

shigella strain disease symptoms

first symptoms -- watery diarrhea, abdominal cramps, fever. these first symptoms can then progress to dysentery (bloody diarrhea with mucus)

shigella strain diseases treatment

usually self-limiting, so supportive therapy is only needed

shigella strain diseases at-risk populations

children, daycare centers, and schools

shigella strain lab characteristics

lactose nonfermenter, catalase negative

vibrio cholerae characteristics

gram negative curved rod

vibrio cholerae associated disease

cholera

vibrio cholerae toxin and MOA

• phage-mediated cholera toxin

• ADP ribosylates protein that irreversibly activating Gs, activating adenylate cyclase, increasing cAMP conc, triggering cell to pump water from blood to intestinal tract --> diarrhea

cholera symptoms

explosive rice water stools, dehydration

cholera transmission

ingestion of contaminated food/water

cholera treatment

fluids and electrolytes! very inexpensive to treat and yet so many people die from it :/

vibrio cholerae lab characteristics

growth on thiosulfate citrate bile salt agar (turn green agar orange), halophile, oxidase positive

vibrio parahemolyticus characteristics

gram negative curved rod

vibrio parahemolyticus associated disease

GI infection

vibrio parahemolyticus virulence factor and MOA

• thermostable direct hemolysin/Kanagawa hemolysin, enterotoxin

• increases intracellular Ca2++ —> chloride secretion induced

vibrio parahemolyticus transmission

ingestion of improperly cooked seafood

vibrio parahemolyticus GI infection symptoms

explosive, watery diarrhea

vibrio hemolyticus lab characteristics

growth on thiosulfate citrate bile salt agar (turn green agar orange), halophile, oxidase positive

campylobacter jejuni characteristics

gram negative corkscrew-shaped rod

campylobacter jejuni associated disease

campylobacteriosis

campylobacter jejuni virulence factor and MOA

• no specific toxin because disease is caused by invasion not intoxication, but does use flagella to move

• invades epithelium of small intestine, causing inflammation

campylobacteriosis symptoms

bloody diarrhea, fever, abdominal pain

campylobacter jejuni lab characteristics

microaerophilic, capnophilic, prefers 42 degrees C

what is so special about campylobacter jejuni?

#1 cause of bacterial gastroenteritis in the US

camplyobacter jejuni at risk patients

Guillain-Barre syndrome, reactive arthritis

helicobacter pylori characteristics

gram negative spiral (changes shape as culture ages)

helicobacter pylori associated diseases

chronic gastritis --> peptic ulcers --> gastric cancer

helicobacter pylori virulence factor and MOA

• flagella

• block acid production —> neutralize acid with ammonia —> burrow into mucus —> attach to epithelial cells

helicobacter pylori infection symptoms

fullness, vomiting, nausea

helicobacter pylori at risk populations

people with hypochlorhydria (why? these people have low stomach acid production, which exacerbates the symptoms of this disease that already blocks acid production)

why is helicobacter pylori so special?

one of the few organisms directly linked to causing cancer

helicobacter pylori lab characteristics

acidophile, urease positive, microaerophile