Antianaerobic antibiotic therapy promotes overgrowth of antibiotic-resistant, gram-negative bacilli and vancomycin-resistant enterococci in the stool of colonized patients.
OBJECTIVE
Antianaerobic antibiotic therapy promotes persistent high-density growth of vancomycin-resistant enterococci (VRE) in the stool of colonized patients. We tested the hypothesis that antibiotic regimens with potent antianaerobic activity promote overgrowth of coexisting antibiotic-resistant, gram-negative bacilli in the stool of VRE-colonized patients.


METHODS
Eight-month prospective study examining the effect of antibiotic therapy on the stool density of gram-negative bacilli resistant to ceftazidime, ciprofloxacin, or piperacillin/tazobactam.


METHODS
A Department of Veterans Affairs medical center including an acute care hospital and nursing home.


METHODS
All VRE-colonized patients with at least 3 stool samples available for analysis.


RESULTS
One-hundred forty stool samples were obtained from 37 study patients. Forty-nine (61%) of 80 stool samples obtained during therapy with an antianaerobic regimen were positive for an antibiotic-resistant, gram-negative bacillus, where-as only 14 (23%) of 60 samples obtained 4 or more weeks after completion of such therapy were positive (P < .001). Twenty-four (65%) of the 37 patients had one or more stool cultures positive for a gram-negative bacillus resistant to ciprofloxacin, ceftazidime, or piperacillin/tazobactam. The density of these organisms was higher during therapy with antianaerobic regimens than in the absence of such therapy for at least 2 weeks (mean +/- standard deviation, 5.6 +/- 1.4 and 3.9 +/- 0.71 log10 organisms/g; P < .001).


CONCLUSIONS
Limiting the use of antianaerobic antibiotics in VRE-colonized patients may reduce the density of colonization with coexisting antibiotic-resistant, gram-negative bacilli.
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000900:Anti-Bacterial Agents / Q000627:therapeutic use*; D001421:Bacteria, Anaerobic / Q000187:drug effects*; D024881:Drug Resistance, Bacterial; D016983:Enterococcus / Q000187:drug effects* / Q000502:physiology; D005243:Feces / Q000382:microbiology; D005260:Female; D006090:Gram-Negative Bacteria / Q000187:drug effects* / Q000472:pathogenicity; D006801:Humans; D008297:Male; D008875:Middle Aged; D011157:Population Dynamics; D011446:Prospective Studies; D020713:Vancomycin Resistance
D000900:Anti-Bacterial Agents