Treatment of GI Infections

Question 1

What are the major anaerobic genuses of the gut, and are they more common than aerobes?

Answer 1

Bacteroides, Clostridium, peptostreptococci

Outnumber aerobes 100:1

Question 2

What are the major aerobic genuses of the gut?

Answer 2

PEK - E. coli, Proteus, Klebsiella, enterococcus

Question 3

When do we cover enterococcus?

Answer 3

Only when it is cultured, because there is question as to whether it’s even pathogenic

Question 4

What is the most resistant anaerobe and what is good against it?

Answer 4

Bacteroides fragilis

Usual: Beta-lactam / b-lactamase inhibitors, metronidazole, or cefoxitin (2nd generation GI)

Question 5

What is the aerobe we try to empirically cover and what is good against it?

Answer 5

E. coli
Sensitivities vary greatly from location to location (hospital to hospital), so just know general susceptibility profiles

Question 6

What must be covered in a nosocomial or a previously antibiotically treated peritonitis vs a community acquired?

Answer 6

In CA, we typically don’t cover enterococcus.

If nosocomial, we cover P. aeruginosa, Enterococcus, and Candida spp.

Question 7

What is SBP and what causes it?

Answer 7

Spontaneous bacterial peritonitis (primary peritonitis)

Complication of impaired liver function / cirrhosis which lowers albumin, leading to loss of oncotic pressure in blood vessels and subsequent ascites. Bacteria can translocate into peritoneum during ascites.

Question 8

What are the most common causative organisms of SBP?

Answer 8

E. coli, Klebsiella, Streptococccus spp. (facultative anaerobes)

Question 9

What is the mainstay of treatment for SBP? How long?

Answer 9

3rd generation cephalosporins, i.e. ceftriaxone

Short course: 5-7 days

Question 10

What is given as prophylaxis for SBP if there has been a previous episode or a GI bleed?

Answer 10

Bactrim 5 days a week or Ciprofloxacin once weekly.

Question 11

A fungus is isolated in SBP. When should you treat?

Answer 11

Unnecessary to treat unless patient is immunocompromised or infection is recurrent

Question 12

What are other common intra-abdominal infections? What is cholangitis?

Answer 12

Abscesses, ruptured bowel, cholangitis (inflammation of bile duct)

Question 13

What typically causes other intra-abdominal infections?

Answer 13

Normal flora (i.e. B. fragilis or E. coli)

Question 14

How do we treat community acquired vs nosocomial or critically ill CA intra-abdominal infections

Answer 14

CA: treat E. coli empirically based on location with a cephalosporin + metronidazole for B fragilis

Nosocomial: Expand coverage to cover Pseudomonas, i.e. Cefepime /metronidazole or Piperacillin/tazobactam

Question 15

When is acute cholecystitis treated and why?

Answer 15

Only when an infection is expected -> often only an inflammatory condition

Treat the same causative organisms as an intra-abdominal infection

Question 16

What is most critical in determining the duration of treatment for an intra-abdominal infection? What is your benchmark of stopping?

Answer 16

Typically 4-7 days is good, but need source control (i.e. draining abscesses / checking inoperable abscesses via X-ray or CT)

Benchmark of stopping: GI function return, no fever, WBC decreases

Question 17

What is the first thing we do when a patient comes in with infectious diarrhea?

Answer 17

Initiate rehydration + perform clinical evaluation including fecal studies

Question 18

When should we give antimicrobial therapy for diarrhea?

Answer 18

Travelers diarrhea, Shigella, Campylobacter, some C. difficile infections

Question 19

When should we really avoid giving anti-motility (anti-diarrheal) drugs?

Answer 19

Toxin-producing bugs, i.e. bloody diarrhea, EHEC, C. difficile.

We gotta poop that toxin out

Question 20

What is the recommendation for anti-microbial treatment of Salmonella?

Answer 20

Not routinely recommended, except in severe disease or extreme agents

Question 21

What are the two recommended treatments for Salmonella / Shigella?

Answer 21

Either Ciprofloxacin or Amoxicillin / Ampicillin (HELPS)

Question 22

What are the treatment courses for Salmonella / Shigella in normal / immunocompromised or relapsing patients? Which is a shorter duration?

Answer 22

Salmonella = 5-7 days like SBP for normal
Shigella = 3-5 days

Salmonella = 14 days for immunocompromised / relapse
Shigella = 7-10 days for immunocompromised

Typically, Shigella has shorter durations

Question 23

What is the duration of therapy for E. coli and what is the mainstays of therapy?

Answer 23

3 days

Typically cephalosporins or Cipro or bactrim

Question 24

What is the #1 treatment for Aeromonas and how long?

Answer 24

Ciprofloxacin - 3 days

Question 25

What is the number 1 treatment for Vibrio, and what do you do if you can’t use that agent?

Answer 25

Doxycycline 300 mg x 1 (triple the normal dose)

If child under 8, use TMP/SMX x3 days, or 1 dose FQ

Question 26

What is the treatment / duration of choice for Giardia?

Answer 26

Metronidazole x7-10 days

Question 27

For Traveler’s diarrhea, why are antibiotics of secondary importance?

Answer 27

Hydration is key! Electrolyte abnormalities can cause cardiac arrythmias which are acutely fatal

Question 28

How do we treat Traveler’s diarrhea in children?

Answer 28

Avoid tetracyclines - tooth damage
Avoid FQ - cartilage damage

Bactrim and Beta-lactams are a good option

Question 29

What is the mainstay of antibiotic treatment for Traveler’s diarrhea?

Answer 29

Fluoroquinolones

Question 30

What are two things which can exacerbate C. difficile infections?

Answer 30

1. Broad spectrum antibiotics

2. Acid-suppressive agents (i.e. PPIs), blocking your major immune function

Question 31

What is the first choice treatment for mild-moderate C. difficile and how is this defined?

Answer 31

Metronidazole

Defined as lack of systemic complication, with normal WBC and serum creatinine (showing no acute renal disfunction)

Question 32

What is the first line treatment for severe C. difficile infection?

Answer 32

Oral vancomycin

Question 33

What is the duration of therapy for C. difficile?

Answer 33

10-14 days on first instance… afterwards just do an FMT honestly

Question 34

What is the mechanism of action of Fidaxomicin? Why might it be preferable to oral vancomycin? Why not?

Answer 34

Inhibits RNA synthesis by inhibiting RNA polymerases - bactericidal

Preferable due to lower recurrence rates overtime

Problem: Super expensive

Question 35

What is the post-exposure prophylaxis to HBV?

Answer 35

Vaccine + HBVIg = antibodies to HBV

Question 36

What are the treatment options to HBV?

Answer 36

Interferon-alpha, and some HIV meds (lamivudine, adefovir)

Question 37

What are the mechanisms of action of interferon-alpha?

Answer 37

Inhibits viral protein synthesis, viral penetration, and viral uncoating directly

Also BOOSTS host immune response

Question 38

When and how is IF-alpha given?

Answer 38

Typically in Hep C or acute Hep B, otherwise in Hep B the HIV antivirals are better

Given subcutaneously or intramuscularly, often conjugated to polyethylene glycol (Pegylated) to allow weekly option rather than 3x weekly.

Question 39

What are the side effects of IF-alpha?

Answer 39

Flu-like syndrome when drug is administered

Thrombocytopenia / granulocytopenia
Severe depression (give with SSRI)
Rash / alopecia

Question 40

What was the old regimen for Hep C?

Answer 40

24-48 week course of interferon-alpha + Ribavirin, a guanine analog also used in RSV.

Had very toxic side effects = hemolytic anemia and renal insufficiency. Also poor SVR

Question 41

What is SVR?

Answer 41

Sustained virological response - essentially a full cure with no HCV in blood after 24 weeks off treatment.