Role of Klebsiella oxytoca in antibiotic-associated diarrhea.

BACKGROUND: Klebsiella oxytoca was recently shown to be the causative agent of antibiotic-associated hemorrhagic colitis. Because it is unclear whether K. oxytoca also causes nonhemorrhagic antibiotic-associated diarrhea, our study investigated a possible association between K. oxytoca and that disorder.
METHODS: A total of 371 consecutive patients were recruited into 4 study groups: (1) group A+D+ (patients who received antibiotics and experienced diarrhea; n = 107), (2) group A+D- (patients who received antibiotics but did not experience diarrhea; np93), (3) group A-D+ (patients who experienced acute-onset diarrhea but did not receive antibiotics; n = 60), and (4) group A-D- (patients without diarrhea who did not receive antibiotics; n = 111). Stool samples were plated on MacConkey agar and K. oxytoca was identified using a standard test kit. Clostridium difficile was detected by a toxin A/B antigen test. K. oxytoca strains were tested for cytotoxicity with use of cell-culture assays.
RESULTS: In 15 of 371 stool samples, K. oxytoca strains were isolated during the study period. There was no significant difference in the distribution of K. oxytoca among the 4 study groups. Six of the 15 strains were found to be toxin producing. Three of the toxin-producing strains caused antibiotic-associated hemorrhagic colitis. No case of nonhemorrhagic antibiotic-associated diarrhea due to toxin-producing K. oxytoca was detected.
CONCLUSION: K. oxytoca is not the causative agent of nonhemorrhagic antibiotic-associated diarrhea. This is in contrast to the distinct clinical entity of antibiotic-associated hemorrhagic colitis. Testing for K. oxytoca is therefore only warranted for patients who experience bloody diarrhea during antibiotic therapy.