Week 2 Flashcards
(139 cards)
MacConkey agar
inhibits gram + bacteria, lactose fermenters become pink/purple
EMB agar
methylene blue inhibits gram + bacteria, lactose fermenters become dark purple/black (E. coli is green)
Salmonella
oxidase \_\_\_\_\_ gram \_\_\_\_\_\_\_ ferments \_\_\_\_\_\_ Lac \_\_\_\_\_ Invasive or noninvasive? infects what part of GI tract?
oxidase -
gram -
ferment glucose
Lac -
INVASIVE
Small intestine
Typhoid fever
Caused by salmonella Typhi infection
1) enteric fever, systemic disease, fever
2) Human adapted - Colonizes gall bladder → carrier state or intestinal perforation
3) Constipation or inflammatory diarrhea –> Stepwise increase in temperature to high fever
4) 1-3 weeks incubation
- Can continue for 6-8 weeks
5) Can kill immunocompetent people
6) Has a capsule that helps with immune evasion
TX = abx
Non-typhoidal salmonella infection
Fecal-oral transmission from poultry, eggs, contaminated fresh produce
Febrile food poisoning 24-48 hrs after ingestion
Nausea, vomiting, headache, chills, fever, cramps, watery diarrhea
High neutrophils
Self-limited - no abx required
Can cause disseminated disease in HIV patients
Salmonella
Toxins/Virulence Factors
TYPE III SECRETION SYSTEM
1) Invasion via M cells with type III secretion system → transient bacteremia
2) Uptake by phagocytes (macs) via different type III secretion system → salmonella multiply
Typhoid vaccine
purified Vi polysaccharide (adults and children > 2 yrs)
Shigella
gram \_\_\_\_\_\_ oxidase \_\_\_\_\_ ferment \_\_\_\_\_\_ Lac \_\_\_\_\_\_\_ Invasive or noninvasive? Infects what part of GI tract?
Gram - Oxidase - Ferment glucose Lac - INVASIVE Large intestine
What is the infective dose of shigella?
Requires SMALL infective dose (very acid resistant)
Shigella diarrhea
inflammatory diarrhea, dysentery
Fever, malaise, vomiting, watery diarrhea → frank dysentery (frequent small stools with blood/mucus, cramps, tenesmus)
Humans are only known reservoir → fecal-oral from person to person (Food, fingers, feces, flies)
Can cause HUS (S. dysenteriae)
Incubation time for Shigella
Incubation 1-4 days
Shigella
Toxins/Virulence Factors: (2)
1) ENTEROTOXIN –> produce watery diarrhea
2) TYPE III SECRETION SYSTEM
Type III secretion system in Shigella mechanism of invasion and spread
ntry via M cells, uptake by macrophages → induce apoptosis and inflammation (IL-1/IL-8)
Invade basal side of epithelial cells, lyse vacuole, grow in cytoplasm, spread directly into neighboring cells
Only S. dysenteriae (type 1) make cytotoxic Shiga toxin
E. Coli
gram \_\_\_\_ shape? Ferment \_\_\_\_\_ Oxidase \_\_\_\_\_ Lac \_\_\_\_\_
Gram - rod ferments glucose oxidase - lac +
ETEC (Enterotoxigenic)
Diarrhea
traveler’s diarrhea, severe watery, no blood/pus, abdominal cramps, vomiting
Toxigenic, NONINVASIVE
Infects small intestine
ETEC (Enterotoxigenic)
Toxins/Virulence factors (3)
1) Heat labile enterotoxin
2) Heat stable enterotoxin
3) Fimbrial adhesins → colonize small intestine
ETEC (Enterotoxigenic)
Treatment
supportive, fluid replacement
Do NOT use abx
Heat labile enterotoxin
Present in ETEC
similar to CHOLERA TOXIN but binds to different gangliosides (different B-subunit) than cholera → target different populations
Heat stable enterotoxin
Present in ETEC
small peptide toxin, activates guanylate cyclase → increased cGMP → increase fluid secretion
EHEC: Enterohemorrhagic
Diarrhea
bloody, hemorrhagic colitis, dysentery
INITIAL WATERY diarrhea → grossly BLOODY
Fever can be seen
Fecal leukocytes uncommon **
Primarily toxigenic - NONINVASIVE
Infects large intestine
EHEC: Enterohemorrhagic
Infectious dose?
Incubation period?
Possible complications?
Requires only small infectious dose (acid stable)
3-9 days of incubation
Can cause Hemolytic Uremic Syndrome (HUS)
EHEC: Enterohemorrhagic
most common serotype
O157:H7 serotype = colorless colonies on sorbitol-MacConkey media (does NOT ferment sorbitol)
EHEC: Enterohemorrhagic
Treatment
supportive
NO abx
abx → increase risk of HUS by increasing expression of shiga-like toxin
EHEC: Enterohemorrhagic
Toxins/Virulence Factors:
1) Attaching and effacing
2) Shiga-like cytotoxins Stx-1 and Stx-II