Slide 2. Peritonitis
This aspirate of peritoneal fluid contains a few neutrophils and numerous faintly-stained, thin, short, and sometimes coccoid, gram-negative bacilli. Their structure and source strongly suggest that the organisms are anaerobic. However, they could also be other bacteria, such as Eikenella or other fastidious bacilli. Only Bacteroides fragilis grew on this culture.

(Labeled view)

Slide 3. Peritonitis
This aspirate of peritoneal fluid contains a few neutrophils; several gram-positive cocci singly, in pairs, and in chains; and many gram-negative bacteria of various forms. They include long, slender bacilli with pointed ends, shorter rods, and cocci. Mixed anaerobic flora grew on the culture. Anaerobic and microaerophilic streptococci tend to be smaller than facultative streptococci, but the distinction is often difficult to make on Gram stains.

Slide 4. Peritonitis
This aspirate of peritoneal fluid contains a few neutrophils, a few gram-negative coccobacilli, and thick gram-positive bacilli that resemble Clostridium. Mixed anaerobic flora, including Clostridium species, grew on the culture.

(Labeled view)

Slide 5. Peritonitis
This slide of peritoneal fluid from a patient with a perforated colonic diverticulum demonstrates several neutrophils and bacteria of two major types: gram-positive cocci in chains and pleomorphic gram-negative coccobacilli. Cultures of fluid yielded a Peptostreptococcus species. These anaerobic bacteria are numerous in the fecal flora and are common in infections that complicate colonic perforation.