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.