Intra-Abdominal Infections

1.5 LH - I really doubt he will ask about the normal flora even though it's on study guide so ignore that if it's too much

An intraabdominal infection is one that is located within the _________ or _____________

An infection within the peritoneal or retroperitoneal space

Define uncomplicated and complicated IAIs 

uncomplicated if infection remains contained within an organ

complicated if it extends beyond a single organ, involves anatomical disruption, peritonitis

_{peritonitis = (inflammation of the peritoneum) or abscess ^{(localized collection of pus caused by infection - dead WBC, bacteria, tissue + fluid)}}

What is the difference between primary, secondary, tertiary peritonitis?

Primary - (spontaneous) = infection w/o any clear source of the infection

Secondary - infection of peritoneal cavity caused by another infection within the abdomen

Tertiary - persistent or recurring infection after tx of primary or secondary that happens >48h after it seemed controlled

what flora are normal to the stomach?

streptococcus and lactobacillus

what flora are normal to the bilary tract?

e. coli, klebsiella, enterococcus

Infection occurs because abdominal organs leak bacteria into the peritoneal cavity

secondary peritonitis

Infection occurs without GI perforation (blood spread or bacterial translocation).

Primary peritonitis

inflammation of the gallbladder

cholecystitis

inflammation and infection of the bile duct

cholangitis

What is the difference between diverticulitis and diverticulosis?

diverticulosis - small pockets develop in wall of colon

“ “ itis - acute inflammation of diverticula caused by infection

What generalization about number of bacteria and aerobes/anaerobes can you make as you go down the GI tract?

as you go down the GI tract the # of bacteria increases and anaerobes become dominant

The biliary tract is normally sterile. If infection (usually ascending from the intestine) is present, what 3 bacteria would be suspected to colonize?

e. coli; klebsiella; enterococci

_{Prob low yield} - (aside from stomach) - Which THREE bacteria are located in all regions of the GIT?

e. coli, klebsiella, enterococci

Colonizers of the proximal small bowel, aside from the 3 that are everywhere:

strep, lactobacillus, diptheroids

(+ e. coli, klebsiella, enterococci)

Colonizers of the distal ileum, aside from the 3 that are everywhere:

1. enterobacter

2. b.fragilis

3. clostridium

4. peptostrepto

ebcp

(+ e. coli, klebsiella, enterococci)

Colonizers of the colon, aside from the 3 that are everywhere:

= distal ileum BUT NOW WITH candida

Are primary and secondary peritonitis usually mono or polymicrobial?

primary = mono

secondary = poly

common bacteria that are culprits in cirrhosis SPB (primary;spontaneous)

1. e. coli

2. klebs

3. strep pneumo

4. h.influenzae

What family is klebsiella:

Enterobacteriaceae (gram negative rods)

What is the oxygen requirement of enterobacteraceae?

facultative anaerobes

What are the GRAM POSITIVES that are culprits in peritoneal dialysis-associated primary peritonitis?

staph, strep, and enterococci

What are the GRAM NEGATIVES that are culprits in peritoneal dialysis-associated primary peritonitis?

e.coli, klebs, and psuedomonas

Way of remembering the pathogens that can cause a secondary peritonitis

anything that we said colonized the GIT + proteus

List the big 3 most clinically important anaerobes that we see:

1. bacteroides

2. clostridium

3. peptostrepto

difference in s/s of primary vs secondary peritonitis

primary sx are vague and mild and pretty nonspecific + moderate iflammation

secondary are acute and severe, sepsis/medical emergency signs + high inflammation

How is spontaneous bacterial peritonitis diagnosed (i.e., what is the main diagnostic criteria)?

paracentesis - ascitic PMN count ≥ 250 cells/mm³ is the main diagnostic criterion ± culture to identify pathogen

mainstay of uncomplicated IAI treatment

surgical management

T/F - Primary peritonitis may often be managed with abx alone

true; in secondary the abx have more of a supplemental role to surgical intervention

Say you want to design an empiric regimen for secondary bacterial peritonitis… what general spectrum would you aim for?

gram negative that covers both aerobes and anaerobes

T/F - an empiric regimen for secondary peritonitis should always include enterococci, fungal, and MRSA coverage

false;

^{Empiric enterococcal coverage recommended only in high-risk patients}

^{Fungal coverage is NOT recommended empirically}

^{Antifungal therapy is indicated for higher-risk patients with IAI if Candida spp. is grown from an intraabdominal culture}

^{MRSA also typically not rec’d}

Source control (non-pharm procedures) are almost always needed for secondary peritonitis. This includes what 4 steps, starting with

1. draining the abscess

2. ?

3. ?

4. ?

1. draining the abscess

2. correcting perforation

3. remove dead tissue

4. irrigate w/ NS

What are some of the characteristics that make a patient “high risk” for treatment failure? List at least two.

1. HEALTHCARE-ASSOCIATED IAI

2. sepsis or shock

3. APACHE-II score > 10

4. comorbidities (hepatic, CV, malignancy, renal)

(FYI) What generalizations can you make about the empiric coverage for treating biliary infections?

• Mild

• Moderate

• Severe

as severity increases, we get more nuclear and increase severity of coverage

Mild - use narrower gram-negative coverage

moderate - broader gram neg + anaerobes

severe/healthcare - broader spectrum + MRSA coverage

gram (-) rods + anaerobes

Why is metronidazole often added on to cephalosporins?

for anaerobe coverage (cephalosporins do not reliably cover anaerobes)

List at least 3 drugs that cover anaerobes:

1. pip/tazo

2. carbapenems

3. cefoxitin (2nd gen)

4. moxifloxacin

When do we add vanco in the contxt of empiric tx for biliary infections? Why?

When high severity or healthcare-associated - to cover MRSA

A way to think about treating diverticulitis is to always cover flora from the ______

colon (colonic diverticulum is what gets infected)

(again, gram negative rods and anaerobes)

Which two drugs should always raise a flag to add metronidazole to due to lack of anaerobe coverage?

cephalosporins* and FQs

_{*some exceptions}

Why might ampicillin or vanco be added in healthcare-associated diverticulitis?

Enterococcus coverage

What is the preferred empiric treatment for spontaneous bacterial peritonitis?

IV 3rd-generation cephalosporin
• ceftriaxone
• cefotaxime

Most common cause of primary peritonitis

Cirrhosis with ascites

Preferred antibiotic route for peritoneal dialysis peritonitis

Intraperitoneal (not IV)

Gram-positive coverage for peritoneal dialysis peritonitis

1. Cefazolin (gen 1)

2. Vancomycin (if MRSA suspected)

Gram-negative coverage for peritoneal dialysis peritonitis

1. Ceftazidime

2. Aminoglycoside

3. cefipime (if no suspected MRSA) (would be monotherapy)

How do we distinguish between a community onset and healthcare onset IAI?

healthcare = obtained >48h after admission

community - see attachment

What is the first line preferred antibiotic regimen for chronic appendicitis?

ANTIBIOTICS ARE NOT RECOMMENDED!