Peritonitis refers to inflammation of the peritoneum lining the abdominal cavity. There are three main types: primary involves direct bacterial invasion from the bloodstream; secondary occurs when the peritoneum is contaminated by a perforated organ; and tertiary develops in immunocompromised patients and is difficult to treat. Primary peritonitis involves a single bacterium and usually resolves with antibiotics alone. Secondary peritonitis requires source control through surgery in addition to broad-spectrum antibiotics to address mixed aerobic and anaerobic bacteria. Tertiary peritonitis has high mortality over 50% even with antibiotics and source control due to drug-resistant bacteria and weakened host defenses.

1. Peritonitis

4. Peritonitis aka intra-abdominal infection
• Microbial contamination of the peritoneal
cavity
• inflammation of the serosal membrane
that lines the abdominal cavity and the
organs contained therein
• may be infectious or sterile

5. Primary microbial peritonitis
• microbes invade the normally sterile
confines of the peritoneal cavity via
hematogenous dissemination from a
distant source of infection or direct
inoculation
• invariably monomicrobial and rarely
require surgical intervention

6. Primary microbial peritonitis
• Physical examination
– diffuse tenderness and guarding without localized
findings
• CBC
– presence of more than 100 WBCs/mL
• Imaging study
– absence of pneumoperitoneum
• Gram’s stain (fluid obtained via paracentesis)
– microbes with a single morphology
• Diagnosis:
– established based on identification of risk factors
(ascites, individuals who are being treated for
renal failure via peritoneal dialysis)

7. Primary microbial peritonitis
• Treatment
– administration of an antibiotic to which the
organism is sensitive often 14 to 21 days of
therapy are required.
– Removal of indwelling devices (e.g., a
peritoneal dialysis catheter or a
peritoneovenous shunt) may be required for
effective therapy of recurrent infections.

8. Secondary microbial peritonitis
• occurs subsequent to contamination of the
peritoneal cavity due to perforation or
severe inflammation and infection of an
intra-abdominal organ
• e.g. appendicitis, perforation of any portion
of the gastrointestinal tract, or diverticulitis

9. Secondary microbial peritonitis
• in most patients the precise diagnosis
cannot be established until exploratory
laparotomy is performed
• most morbid form of this disease process
is colonic perforation, due to the large
number of microbes presen

10. Effective Therapy
• source control to resect or repair the
diseased organ
• débridement of necrotic, infected tissue
and debris
• administration of antimicrobial agents
directed against aerobes and anaerobes

11. • Effective source control and antibiotic
therapy is associated with low failure rates
and a mortality rate of approximately 5%
to 6%
• inability to control the source of infection is
associated with mortality greater than 40%

12. Tertiary (persistent) peritonitis
• develops more frequently in
immunocompromised patients and in
persons with significant preexisting
comorbid conditions
• Microbes such as Enterococcus faecalis
and faecium, Staphylococcus epidermidis,
Candida albicans, and Pseudomonas
aeruginosa commonly are identified,
typically in combination, and their presence
may be due to their lack of responsiveness
to the initial antibiotic regimen, coupled with
diminished activity of host defenses

13. • even with effective antimicrobial agent
therapy, this disease process is
associated with mortality rates in excess
of 50%.

14. Tertiary (persistent) peritonitis
• Diagnosis
– Intraabdominal abscesses can be effectively diagnosed via
abdominal computed tomographic (CT) imaging techniques
and drained percutaneously.
• Surgical intervention
– reserved for those individuals who harbor multiple abscesses,
those with abscesses in proximity to vital structures such that
percutaneous drainage would be hazardous, and those in
whom an ongoing source of contamination (e.g., enteric leak)
is identified.
• Antimicrobial agent therapy
– necessity not established
• Catheter drainage
– precise guidelines that dictate duration are not established

15. • A short course (3 to 7 days) of antibiotics
that possess aerobic and anaerobic
activity seems reasonable
• Most practitioners leave the drainage
catheter in situ until
– it is clear that cavity collapse has occurred
– output is less than 10 to 20 mL/d
– no evidence of an ongoing source of
contamination is present
– patient’s clinical condition has improved

16. Common Causes of Secondary Peritonitis

18. Microbial Flora of Secondary Peritonitis

19. Microbiology of Primary, Secondary, and
Tertiary Peritonitis