Enteric Bacterial Infections

Question 1

what is the morphology of all foodborne enterobacteriaceae?

Answer 1

gram negative rods

Question 2

how do enterobacteriaceae colonize the lumen of the intestine?

Answer 2

they cannot colonize the epithelium in the lumen

Question 3

how do enterobacteriaceae gain access to the host?

Answer 3

they are sampled by M cells of Peyers patches to gain access to the serosa side of the intestine

Question 4

how do enterobacteriacea avoid the immune system?

Answer 4

they use macrophages as trojan horses and infect the lymphatics

Question 5

what are the diseases caused by Yersinia and salmonella using macrophages as trojan horses?

Answer 5

yersina- local false appendicitis

salmonella- systemic enteric fever or post sepsis focal disease

Question 6

what are the differences in clinical presentation of noninvasive vs invasive/destructive enterobacteriaceae?

Answer 6

noninvasive- watery diarrhea

invasive- bloody diarrhea

Question 7

which enterobacteria are noninvasive?

Answer 7

salmonella, enterotoxic e coli and yersinia

Question 8

which enterobacteria are invasive/destructive?

Answer 8

shigella and enterohemorrhagic e coli

Question 9

what are the common exposures of foodborne enterobacterial infections?

Answer 9

proteins

meat for e coli and meat or eggs for salmonella

Question 10

what causes the most complications of enterobacterial infections?

Answer 10

dehydration and electrolyte loss

Question 11

what life threatening complication may follow gut tissue necrosis?

Answer 11

bacteremia

Question 12

how are virulence factors often carried in enterobacteria?

Answer 12

plasmids

Question 13

what are the common virulence factors for foodborne enterobacteria?

Answer 13

fimbriae/pilli for attachment, T3SS for immune evasion and/or host cell invasion and toxins

Question 14

what determines the disease caused by E coli?

Answer 14

the acquired virulence factors make it able to cause certain diseases

Question 15

which is the only enterobacterial pathogen that is likely to ferment lactose?

Answer 15

e coli

pink on MacConckey agar which detects fermentation of lactose

Question 16

who has the highest risk of developing a foodborne enterobacterial infection? who is at the highest risk for mortality?

Answer 16

children

neonates and elderly

Question 17

which pathogens cause HUS? when does it occur?

Answer 17

shigella and enterohemorrhagic E coli

when shiga toxin (protein synthesis inhibitor) reaches the bloodstream

Question 18

what is one postinfectious sequalae of shigella, salmonella and yersinia infection?

Answer 18

reactive arthritis/ reiter’s syndrome

Question 19

what should be done before treatment of enterobacterial infection?

Answer 19

antimicrobial susceptibility testing

Question 20

how is exposure to enterobacteriacae minimized?

Answer 20

sewage treatment, pasteurization, water chlorination, food processing and hand washing

Question 21

what causes noninfectious bacterial- toxigenic food poisoning?

Answer 21

a patient eats a food containing preformed toxins secreted by non GI bacteria

Question 22

which three pathogens cause toxigenic food poisoning? what happens to the bacteria when they are ingested?

Answer 22

staph aureus, B. cereus and C. botulinum

they do not survive ingestion but their toxins cause gastroenteritis

Question 23

what conditions are suitable for staph aureus and b cereus colonization?
c botulinum?

Answer 23

foods left open at room temp

c b- airtight packaged foods (anaerobic)

Question 24

what is the morphology of listeria? what type of hemolysis does it exhibit?

Answer 24

gram positive rod

beta hemolytic

Question 25

how is listeria transmitted to humans?

Answer 25

ingestion of undercooked, refrigerated foods or contact with farm animals

Question 26

how does listeria infect cells?

Answer 26

escapes from phagocytic vacuole with listerolysin | transmits cell to cell with actin based motility

Question 27

what is the result of listeria infection in pregnant women?

Answer 27

it grows in the placenta | can cause neonatal morbility and mortality

Question 28

what is the result of listeria infection in immunocompromised patients?

Answer 28

sepsis and CNS infection

Question 29

how is listeriosis treated in pregnancy or immunocompromise?

Answer 29

ampicillin + gentamicin or trimethoprim + sulfamethoxazole

Question 30

what does listeria cause in previously healthy hosts? how is it treated?

Answer 30

uncomplicated gastroenteritis | rehydrate and report

Question 31

what is the morphology of vibrios?

Answer 31

curved gram negative rods

Question 32

what selective media is used to grow vibrio?

Answer 32

bile salt agar (salt tolerant)

Question 33

what is the best way to prevent vibrio infection? what else is available?

Answer 33

hygiene | modestly effective vaccines

Question 34

what are reservoirs of cholera?

Answer 34

humans and plankton from the indian ocean and the gulf of mexico

Question 35

describe rout and infectious dose of cholera

Answer 35

fecal oral rout with poor stomach acid survival and high infectious dose

Question 36

how does cholera colonize the small intestine? how does it cause disease?

Answer 36

with mucinase | toxin coregulated pilus secretes enterotoxin

Question 37

describe cholera enterotoxin. what does it do?

Answer 37

AB subunit toxin that causes massive watery diarrhea

Question 38

what gene incurs pathogenicity in cholera? what antigens can be used to test for infection?

Answer 38

Choleragen gene carried by lysogenic bacteriophage CTX | O1 and O139 antigens

Question 39

what is the result of infection with non CTX cholera strains?

Answer 39

mild sporadic disease

Question 40

what causes morbidity and mortality in cholera infection?

Answer 40

dehydration and electrolyte imbalance (acidosis and hypokalemia)

Question 41

how is cholera dehydration treated?

Answer 41

with IV lacted ringer solution (not just saline because of acidosis)

Question 42

what may shorten the course of cholerae and parahaemolytcus infection? what is more important?

Answer 42

doxycycline | rehydration

Question 43

what other vibrio are infectious? what diseases are they associated with

Answer 43

parahaemolyticus and vulanis | self limited gastroenteritis and life threatening cellulitis

Question 44

how are non cholera vibrio infections contracted?

Answer 44

handling or eating raw shellfish

Question 45

what are complicating factors of vibrio infections?

Answer 45

liver or kidney disease, immunodeficiency and iron overload

Question 46

describe non cholera vibrio cellulitis. how is it treated?

Answer 46

rapidly progressive, hemorrhagic bullae in a seawater exposed injury. treat with surgical excision then antibiotics

Question 47

describe the morphology and metabolism of campylobacter

Answer 47

curved gram negative rods that are microaerophilic

Question 48

where are campylobacter found?

Answer 48

ubiquitous | reservoir is farm animals

Question 49

what is the result of campylobacter infection?

Answer 49

destructive intracellular infection of intestines with bloody diarrhea

Question 50

what are possible complications of campylobacter infection?

Answer 50

guillaia- barre, reactive arthritis, HUS, meningitis and vascular infection

Question 51

how is campylobacter diagnosed?

Answer 51

microaerophilic culture, gram stain of fecal smear and sigmoidoscopy

Question 52

how is campylobacter infection treated?

Answer 52

with rehydration | antibiotics if high fever or predisposed to complications (immunosuppressed, pediatric)

Question 53

how does H pylori cause disease?

Answer 53

it colonizes the stomach, expresses urease and irritates the stomach lining. destruction is immunogenic (ulcer)

Question 54

what diseases does h pylori predispose to?

Answer 54

gastric cancer and malt lymphoma

Question 55

how is h pylori infection diagnosed?

Answer 55

scope, urea breath, PCR, biopsy

Question 56

how is h pylori infection treated?

Answer 56

combined antibiotics and proton pump inhibitors