Enteric Bacteria 1 + 2

Question 1

shigella bacteriology

Answer 1

gram -, oxidase - rods. not lactose fermenting. nonmotile. facultative anerobe and intracellular. fecal-oral.

Question 2

MacConkey selective-differential medium

Answer 2

only gram - can grow on it, and if it grows pink, then they ferment lactose!

Question 3

shigella symptoms

Answer 3

very low infectious dose. causes enterocolitis/dysentery/shigellosis. bloody diarrhea, local inflammation, ulceration. risk of reactive arthritis (reiter’s syndrome)

Question 4

reactive arthritis

Answer 4

autoimmune sequel of bacterial infection in patients positive for HLA B27. conjunctivitis, urethritis, arthritis. treat with NSAIDs

Question 5

shigella pathogenesis

Answer 5

invades epithelium (M cells of peyer’s patch) of distal ileum and colon epithelium using T3SS and secretes exotoxins, which kill adjacent cells. cell necrosis and inflam response lead to bloody diarrhea. virulence depends on 220kb plasmid. protein synth inhibiting shiga toxin is plasmid encoded. also carries siderophores genes, which allow bacteria to grow to large numbers

Question 6

hemolytic uremic syndrome

Answer 6

begins when shiga toxin escapes into bloodstream. sets off immunological/hematological cascade -> hemolysis, renal failure, uremia, DIC.

Question 7

shigella exam

Answer 7

fever, dehydration, headache, lethargy, diarrhea. HUS = fever, dehydration, hemolysis, thrombocytopenia, uremia

Question 8

shigella lab

Answer 8

strain determined by lab immunoassays. methylene blue stain of poop reveals whether neutrophils are present or not. HUS bloodwork shows schistocytes, low platelets, increased lactate dehydrog and PMNs

Question 9

shigella treatment and prevention

Answer 9

fluid and electrolyte replacement. test for Ab sensitivity. Ab treatment decreases HUS risk. no antodiarrheal meds. wash hands, chlorinate water, dispose of sewage

Question 10

e. coli bacteriology

Answer 10

straight gram - rod. facultative anaerobe. lactose fermenter. extracellular, with the exception of EIEC.

Question 11

e. coli cell entry

Answer 11

fimbriae for adherence to host cell. type 3 or 4 secretion system injects molecules to force cells to make actin bundle and causes inflammation. cell to cell motility

Question 12

what does enterotoxigenic E. Coli cause?

Answer 12

ETEC causes traveler’s diarrhea

Question 13

what does enterohemorrhagic e. coli cause?

Answer 13

EHEC is infected by phage STX, produces shiga toxin, and causes HUS.

Question 14

enterotoxigenic diarrhea

Answer 14

pili attaches to jejunum and ileum, enterotoxins synthed. forces host membrane bound ion transporters to export, host loses fluid, potassium, and chloride. watery diarrhea

Question 15

enterohemorrhagic diarrhea

Answer 15

EHEC attach to mucosal epithelial cells of the colon, may invade. lysogenic STX encodes shiga toxin. activates inside gut cells, destroys protein synth. inflammation and bloody diarrhea follow

Question 16

EHEC pathogenesis

Answer 16

carries shigella’s gene for shiga toxin. halts protein synth and kills infected cells. associated with the use of antibiotics to treat bloody diarrhea

Question 17

enterotoxic vs enterohemorrhagic diarrhea treatment

Answer 17

enterotoxic: self-limited, rehydrate
enterohem: no antimotility agents. antibiotics associated with increased HUS risk. rehydrate

Question 18

salmonella bacteriology

Answer 18

gram - rods. motile. seldom lactose fermenting. H2S producer!

Question 19

salmonella pathogenesis

Answer 19

enterocolitis, enteric fevers, septicemia, risk of reiter’s syndrome

Question 20

enterocolitis from salmonella

Answer 20

bacteria invade epithelial and subepithelial tissue of large and small intestine. inflamm and diarrhea, N/V. immune response restricts to gut, bacteremia is rare. gastric acid is protective, antacids increase risk. Go in through M cells.

Question 21

salmonella virulence factors

Answer 21

Ipf operon enhances adhesion to M cells. T3SS injects M cells. SipB causes macrophage apoptosis (Spi1 T3SS). Spi2 T3SS remodels phagosomes for systemic spread. Vi antigen is capsule for immune evasion

Question 22

enteric and typhoid fevers

Answer 22

human restricted, fecal oral. high infectious dose. invades peyer patch of distal ilieum. enters macrophages. invades major organs. bacteria cause macrophage to apoptose, go into blood.

Question 23

enteric/typhoid fever symptoms

Answer 23

fever, malaise, diffuse ab pain, constipation. 3-4 week progression of cough, stupor, delirium, hemorrhage, bowel perforation, myocarditis, death. survivors have long term neurological sequale or chronic carriage in gallbladder

Question 24

cystic fibrosis allele and typhoid

Answer 24

CFTR allele resists penetration of the gut, protective against typhoid fever.

Question 25

septicemia with salmonella

Answer 25

rare in healthy ppl. sickle cell anemia predisposes. children susceptible. osteomyelitis, pneumonia, meningitis most common sequelae.

Question 26

treatment of enterocolitis and enteric fevers/septicemia caused by salmonella

Answer 26

enterocolitis: rehydrate, do Ab resistance testing before giving drugs.

fever/septicemia: IV ceftriaxone or ciprofloxacin. drain abscesses

Question 27

yersinia bacteriology

Answer 27

gram - oval rods. lack y. pestis virulence factors. not lactose fermenting. grows in cold. motile at 25C, nonmotile at 37C.

Question 28

yersinia e+p pathogenesis

Answer 28

Y. e causes enterocolitis, virulence factors carried on both chromosome and plasmid. high infectious dose. enters through peyer patches. doesnt make siderophore. both species may predispose to reactive arthritis

Question 29

yersinia virulence factors

Answer 29

pili and Inv adhesin enhance binding to M cells. CNF dermonecrotic toxin destroys tissue. Yop T3SS injects proteins into macrophages, leading to no phagocytosis and reduced inflamm response

Question 30

y. pseudotuberculosis in kids

Answer 30

may be associated with izumi fever: generalized vasculitis with symptoms of fever, rash, conjunctival injection, cervical lymphadenitis, inflammation of the lips and oral cavity, erythema and edema of the hands and feet

Question 31

diagnosis for yersinia

Answer 31

exam: diarrhea, dehydration, false appendicitis. lab: culture from stool, blood or CSF. both grow well after cold-enrichment. grow on CIN agar. pseudotub differentiated from entero by fermentation of sorbitol and ornithine decarb activity.

Question 32

yersinia e+p treatment

Answer 32

enterocolitis and mesenteric adenitis dont require drug treatment, replace fluid and electrolytes. serious: use trimeth sulfa or ciprofolx.

Question 33

listeria bacteriology

Answer 33

gram + rod. facultatively anaerobic. blue-green sheen on agar. forms Ls and Vs. tumbling motility by temperature sensitive flagella. beta hemolytic

Question 34

listeria pathogenesis

Answer 34

infection from environmentally contaminated food. causes gastroenteritis. patients immunosuppressed, including pregnant people. can escape GI and cause preg issues, meningitis, absess, etc.

Question 35

listeria + pregnancy

Answer 35

bacteria escape GI, proliferate in placenta (causes early onset sepsis), particularly in 3rd trimester when CMI is lowest. commonly causes preterm labor, abortion, stillbirth, intrauterine infection

Question 36

neonate + listeria

Answer 36

can transmit from vagina during birth. late-onset meningitis with sepsis.

Question 37

listeria exam

Answer 37

in prego: fever, arthralgias, back pain, headache.

CNS symptoms: mental status change, seizures, cranial nerve deficits, strokelike hemiplegia

Question 38

listeria lab

Answer 38

blood cultures. If CNS symptoms, draw CSF: wet mount for motile bacteria. MRI

Question 39

listeria treatment

Answer 39

antibiotics indicated, IV if CNS or bacteremic. ampicillin for 6 weeks with gentamicin combo for first week. resistant to all cephalosporins. reportable (forms epidemics)