Safety and effectiveness of colistin compared with tobramycin for multi-drug resistant Acinetobacter baumannii infections.
BACKGROUND
Nosocomial infections due to multi-drug resistant Acinetobacter baumannii are often treated with colistin, but there are few data comparing its safety and efficacy with other antimicrobials.


METHODS
A retrospective cohort study of patients treated with colistin or tobramycin for A. baumannii infections in intensive care units (ICUs) at Groote Schuur hospital. Colistin was used for A. baumannii isolates which were resistant to all other available antimicrobials. In the tobramycin group, 53% of the isolates were only susceptible to tobramycin and colistin. We assessed ICU mortality, nephrotoxicity and time to the first negative culture.


RESULTS
32 patients, with similar admission APACHE scores and serum creatinine, were treated with each antimicrobial. There were no significant differences between the colistin and tobramycin groups in ICU mortality (p=0.54), nephrotoxicity (p=0.67), change in creatinine from baseline to highest subsequent value (p=0.11) and time to microbiological clearance (p=0.75). The hazard ratio for total in-hospital survival in patients treated with colistin compared to tobramycin was 0.43 (95% CI 0.19 to 0.99).


CONCLUSIONS
Our study suggests that colistin and tobramycin have similar risks of nephrotoxicity and are equally efficacious. Colistin is an acceptable antibiotic for the treatment of A. baumannii infections when the organism is resistant to other available antimicrobials.
Gounden
Ronald
R
Department of medicine, division of clinical pharmacology, University of Cape Town, Cape Town, South Africa. ronald.gounden@uct.ac.za
Bamford
Colleen
C
van Zyl-Smit
Richard
R
Cohen
Karen
K
Maartens
Gary
G
D000151:Acinetobacter Infections / Q000188:drug therapy*; D040981:Acinetobacter baumannii / Q000187:drug effects*; D000328:Adult; D000900:Anti-Bacterial Agents / Q000627:therapeutic use; D015331:Cohort Studies; D003091:Colistin / Q000627:therapeutic use*; D003428:Cross Infection / Q000188:drug therapy*; D024901:Drug Resistance, Multiple, Bacterial; D006801:Humans; D007362:Intensive Care Units; D053208:Kaplan-Meier Estimate; D008875:Middle Aged; D012189:Retrospective Studies; D014031:Tobramycin / Q000627:therapeutic use*; D016896:Treatment Outcome
D000900:Anti-Bacterial Agents; D014031:Tobramycin; D003091:Colistin