Micro Enteric Bacteria 2

Question 1

salmonella bacteriology

Answer 1

• gram - rods
• motile
• seldom lactose fermenting
• oxidase negative
• urease negative
• H2S producing

Question 2

salmonella pathogenesisxmk4o

Answer 2

1. enterocolitis
2. enteric fevers (typhoid)
3. septicemia
4. risk of reactive arthritis (Reiter’s syndrome)

Question 3

salmonella enterocolitis

Answer 3

• usually s. typhimurium, s enteritidis, s heidelberg
• bacteria invade gut wall (M cells) by fimbriae - immune containment
• bacteremia rare
• MC in children and nursing homes in US
• high infectious dose
• cause inflammation and diarrhea, nausea, vomiting

Question 4

salmonella enteric fever

Answer 4

high infectious dose, invasion of gut wall - specifically peyer’s patches of distal ileum = transport in macrophages (trojan horse) to lymphatics and major organs and causes macrophage apoptosis, bacteremia, toxemia
-protected from humoral immunity by Vi capsul

Question 5

virulence factors salmonella

Answer 5

1. ipf operon enhances adhesion to M cells in Peyer’s patches
2. Type 3 secretion system injects M cell, enhances bacterial translocation
3. SipB injected by Spi1 type 3 system causes macrophage apoptosis
4. Vi antigen: s. typhi capsule for immune evasion

Question 6

what is the difference between shigella and salmonella?

Answer 6

shigella lower infectious dose and risk of HUS

Question 7

salmonella enteric and typhoid fevers symptoms

Answer 7

• onset: fever, malaise, diffuse abdominal pain, constipation
• 3-4 week progression: dry cough, stupor, delirium, intestinal hemorrhage, bowel perforation, myocarditis, death

Question 8

what causes hemorrhage/perforation in salmonella enteric/typhoid fevers

Answer 8

necrosis of the infected peyer patches

Question 9

what pathogens use macrophage as trojan horse?

Answer 9

salmonella, TB, cryptococcus, histoplasma

Question 10

penetration of gut by salmonella resisted by what?

Answer 10

CFTR cystic fibrosis allele (heterozygotes)

Question 11

host risk factors for salmonella

Answer 11

corticosteroids, other immunosuppressants, malignancy, diabetes, HIV

Question 12

salmonella septicemia

Answer 12

• very rare in previously healthy adults

- underlying chronic disease like sickle cell predisposes

Question 13

what are the most common sequelae to salmonella septicemia?

Answer 13

osteomyelitis, pneumonia, meningitis

Question 14

salmonella diagnosis

Answer 14

1. enterocolitis: nonbloody diarrhea, fever, dehydration, culture from stool
2. typhoid: travel abroad, high fever, headache, tender abdomen, anorexia, sometimes rose spots (pink, blanchable, slightly raised), lethargy
3. septicemia: focal symptoms related to affected organ [bone (osteomyelitis), lung (pneumonia), meninges]

Question 15

salmonella treatment

Answer 15

enterocolitis: self-limited

enteric fevers and septicemia: IV ceftriaxone or ciprofloxacin - drain focal abscesses

Question 16

Yersinia enterocolitica and pseudotuberculosis bacteriology

Answer 16

• gram - oval rods
• lack yersinia pestis virulence factors (no plague)
• not lactose fermenting
• urease positive
• grows in cold
• motile at 25 C, non motile at 37

Question 17

what does Yersinia enterocolitica and pseudotuberculosis cause?

Answer 17

foodborne gastroenteritis

Question 18

Yersinia enterocolitica pathogenesis

Answer 18

high infectious dose
-penetration of mucosa occurs in ileum –> multiplication in Peyer patches (M cells) –> spread to local lymph nodes –> mesenteric lymphadenitis (false appendicitis)

Question 19

Yersinia enterocolitica virulence factors

Answer 19

carried on chromosome and plasmid

1. pili and Inv adhesin enhance binding to M cells in Peyer’s patches
2. CNF dermonecrotic toxin destroys tissue
3. Yop Type 3 secretion system injects proteins in macrophages (no phagocytosis = reduced inflammatory response)

Question 20

what is there a risk for with Yersinia enterocolitica and pseudotuberculosis

Answer 20

reactive arthritis

Question 21

pseudotuberculosis

Answer 21

similar to yersinia enterocolitica but rarer and seen with immunocompromised or liver disease
-may be associated with izumi fever in children (fever, rash, conjunctival injection, cervical lymphadenitis, inflammation of the lips and oral cavity, edema of hands and feet

Question 22

Yersinia enterocolitica and pseudotuberculosis diagnosis

Answer 22

-exam: diarrhea, dehydration, false appendicitis
-lab: culture from stool or blood
grow well after cold-enrichment

Question 23

how is pseudotuberculosis differentiated from enterocolitica?

Answer 23

pseudotuberculosis has fermentation of sorbitol and ornithine decarboxylase activity

Question 24

listeria monocytogenes bacteriology

Answer 24

• small gram +
• facultative anerobe
• blue-green sheen on non-blood agar
• forms Ls and Vs
• grows well in cold
• tumbling motility by termperature-sensitive flagella
• beta hemolytic
• intracellular

Question 25

what foods is listeria monocytogenes associated with?

Answer 25

unpasteurized dairy products, undercooked meat, raw veggies (cold food)

Question 26

what does listeria cause?

Answer 26

gastroenteritis - usually in immunosuppressed and pregnant/fetus

Question 27

what does listeria infection cause in pregnant women?

Answer 27

3rd trimester - escape GI and proliferate in the placenta | -causes preterm labor, abortion, stillbirth, intrauterine infection

Question 28

what does listeria cause in the neonate?

Answer 28

- early onset sepsis and premature birth with abscesses and/or granulomas - transmission from vagina during birth = late-onset meningitis with sepsis

Question 29

listeria diagnosis on exam

Answer 29

previously healthy: watery diarrhea, fever, headache, cramps pregnancy: fever, arthralgia, back pain, headache immunocompromised: (think transplant!) CNS: mental status changes, seizures, cranial nerve deficits, strokelike hemiplegia, tremor, myoclonus, ataxia, brain abscess

Question 30

listeria lab

Answer 30

gram stain: diphtheroids | culture: small, gray, beta-hemolytic colonies, motility (tumbling), sugar fermentation

Question 31

which bacteria have risk of HUS?

Answer 31

shigella and enterohemorrhagic E coli (O157:H7)

Question 32

which bacteria have a risk of reactive arthritis/Reiter's syndrome?

Answer 32

shigella, salmonella, yersinia