Intraabdominal Infections

Question 1

Secondary peritonitis

Answer 1

Occurs secondary to abdominal process
(Perforations, appendicitis, pancreatitis, diverticulitis, neoplasms, etc)

Question 2

Microbiology of ileum

Answer 2

ileum = final section of small intestine

E.coli, Enterococcus, anaerobes

Question 3

Microbiology of large intestine

Answer 3

Obligate anaerobes (bacteroides, clostridium)
E. coli
Streptococcus
Enterococcus
Klebsiella
Proteus
Enterobacter

Question 4

Ascitic fluid in peritonitis

Answer 4

Protein: >3 g/dL
Exudate
Many WBC, primarily granulocytes

Question 5

Treat peritonitis for <24 hours in these cases

Answer 5

1. Bowel injury from trauma, repaired in 12 hours
2. Intra-operative contamination
3. Perforation of stomach, duodenum, proximal jejunum (If on antacids or malignancy, need longer)
4. Acute appendicitis without evidence of perforation, abscess, peritonitis

Question 6

Antibiotic options for mild-moderate peritonitis, community-acquired

Answer 6

Cefoxitin (2nd gen ceph with anaerobic coverage)
Cefazolin, cefuroxime, ceftriaxone + metronidazole
Ertapenem
Moxifloxacin
Cipro or levo + metronidazole
Tigecycline

*Most do not have Pseudomonas coverage, so cover for typical gram negative, gram positive, and anaerobes

Question 7

High risk/severe peritonitis qualifications

Answer 7

APACHE II score > 15
Old
Poor nutrition/low albumin
Inability to achieve source control
Malignancy
Immunosuppression

Question 8

Antibiotics for high risk/severe peritonitis

Answer 8

Zosyn
Ceftazidime or cefepime + metronidazole
Imipenem/cilastatin or meropenem
Cipro or levo + metronidazole

**Coverage for Pseudomonas + anaerobes

Question 9

CIlastatin purpose for imipenem

Answer 9

Inhibits dehydropeptidase, which normally breaks down imipenem

Cilastatin will prolong activity of imipenem

Question 10

Therapy duration for high risk/severe peritonitis

Answer 10

4 days post source control

Question 11

Nonsevere C.diff labs

Answer 11

WBC <15
SCr <= 1.5

Question 12

Severe Cdiff labs

Answer 12

WBC >= 15
SCr > 1.5

Question 13

Fulminant Cdiff

Answer 13

Hypotension, shock, ileus, or megacolon

Question 14

BI/NAP1 Cdiff strain

Answer 14

Produces more toxins
More likely for metronidazole failure, morbidity, mortality

Question 15

Initial Cdiff episode treatment

Answer 15

Nonsevere/severe:
1. Fidaxomicin 200mg PO BID x10 days
2. Vancomycin 125mg PO QID x10 days

3. If nonsevere and vanc/fidaxomicin unavailable, may use metronidazle PO 500mg TID x10 days.

Question 16

Fulminant Cdiff initial treatment

Answer 16

Vancomycin 500mg PO QID x10 days

If ileus (unable to move food&waste through body):
1. Add metronidazole 500mg IV q8h
2. Add vancomycin 500mg in 100mL NS per rectum in enema QID
3. If ileus resolves, discontinue both.

Question 17

First Cdiff recurrence after metronidazole tx

Answer 17

Vanco 125 PO QID x10 days
Or
Fidaxomicin 200mg PO BID X10 days

Question 18

First Cdiff recurrence after vancomycin & fidaxomicin tx

Answer 18

Fidaxomicin 200mg PO BID x10 days (prefer) (even in first fidaxomicin failure)

Fidaxomicin extended (200mg PO BID x5 days, then 200mg daily for 20 days)

Vanco taper + pulse dose:
125mg PO QID x10-14 days,
then 125mg PO BID x7 days,
then 125mg PO daily x7 days
then 125mg PO q2-3 days for 2-8 weeks

Question 19

Second & subsequent C. diff recurrence

Answer 19

-Fidaxomicin 200mg PO BID X10 days
-Fidaxomicin prolonged course
-Vanco prolonged taper & pulse dose
-Vanco 125mg PO QID x10 days, followed by rifaximin 400mg TID x20 days
-Fecal microbiotia (Rebyota) 150mL rectally x1 24-72 hrs after vanco/fidaxomicin
-Fecal microbiota (Vowst) 4 caps q24H x3 days; 2-4 days after vanco/fidaxomicin

Question 20

Cdiff prophylaxis

Answer 20

Approriate if fidaxomicin not an option, >65 or immunocompromised w/ Cdiff in past 3 months, systemic ABX)

Vancomycin 125m PO daily (if on systemic ABX, discontinue 5 days after therapy complete)

Question 21

Bezlotoxumab

Answer 21

MAB that binds Cdiff toxin B. Lower incidence of recurrent Diff

Use as ppx if high risk of recurrence:
-1 or more prior episode in previous 6 months
->65
-Immunocompromised
-Severe CDI

10mg/kg as single 60 min infusion, given during antibiotic therapy

Caution in CHF

Question 22

Surgical prophylaxis timing

Answer 22

-60 minutes before incision
-60-120 minutes before incision if vancomycin or FQ
-Redose if surgery > 4 hours or considerable blood loss

Question 23

Surgical prophylaxis antibiotics and dosing

Answer 23

Cefazolin 2gm (3gm if >120kg)
Ceftriaxone or cefoxitin 2gm
Clindamycin 900mg
Vancomycin 15mg/kg

Question 24

Surgical prophylaxis antibiotic duration

Answer 24

Most do not need antibiotics after surgery wound closure

Cardiac procedure: 24-48 hours postop

Question 25

Perforated appendicitis surgical prophylaxis

Answer 25

Cefoxitin 2gm or cefazolin + metronidazole or ertapenem 1gm before surgery and 4 days after

Question 26

Colorectal surgical prophylaxis

Answer 26

IV + PO = lower rate of wound infection, leaks, mortality
Anaerobic and aerobic coverage

IV:
-Cefazolin or ceftriaxone + metronidazole
-Cefoxitin 2gm or Unasyn 3gm or ertapenem 1gm
-Gent/tobramycin 5mg/kg + clinda 900 or metronidazole

PO:
-Neomycin 1gm + erythromycin 1gm PO 2, 3, 10pm
-Neomycin 1gm + metronidazole 500mg 2, 3, 10pm

Question 27

When antibiotics are recommended as prophylaxis postoperatively

Answer 27

Cardiothoracic vascular surgery
(3 doses postop)

Otherwise the preoperative dose should be sufficient

Question 28

Broad spectrum ABX Associated with Cdiff

Answer 28

Carbapenems
Clindamycin
Cephalosporins, especially 3-4th gen
FQs

Question 29

Cdiff clinical tests

Answer 29

Toxin A&B immunoassays: low sensitivity, moderate specificity

Glutamate dehydrogenase: high sensitivity, low specificity

NAAT: expensive but high sensitivity