1828. In Vitro Effect of Different Antimicrobial Colistin Based Regimens in Biofilm Production Strains of MDR A baumannii.
Session: Poster Abstract Session: Treatment of HAIs/Antimicrobial Resistant Infections
Saturday, October 10, 2015
Room: Poster Hall
Background: Infections related by biofilm producing bacteria , has been implicated in prolonged antimicrobial treatments, therapeutic failures and or clinical relapses.
There have been described dual regimes to improve results in treating MDR (resistant to carbapenems, quinolones and aminoglycosides) Acinetobacter baumannii, but most studies were made on planktonic state agents.

Methods: Objective: To evaluate different antimicrobial colistin based regimens in the production of biofilm generated by MDR A. baumannii.

We used strains of MDR A. baumannii, with recognized biofilm – production phenotype; all of them showing susceptibility to colistin, according to EUCAST. After 24hrs of incubation, different combinations of antibiotics were added, then they were assigned    in 3 groups as follows: Group 1 - colistin 2 mg / ml (for each experiment fixed dose); Group 2 - colistin 2 mg / ml + rifampicin 2 mg / ml and 4 mg / ml; Group 3 - colistin 2 mg / ml + meropenem 2 mg / ml and 4 mg / ml. For the generation of biofilm polystyrene microplates of 96 wells "U" were used, and then biofilm determined by crystal violet to an OD630nm. Each experiment was performed three fold.

Results: A total of 36 strains of MDR A. baumannii were studied. After monotherapy with colistin at 2 mg / ml (Group 1), the  biofilm production was evident just in 16 strains (44.4%). The remaining 20 strains were then evaluated with the combination of: colistin plus rifampicin inhibiting biofilm production in 91.7% at 2 mg / ml and 97.3% at 4 mg / ml and colistin plus meropenem in 69.5% at 2 mg / ml and 86.2% at 4 mg / ml.  

Conclusion: The effect of anti-biofilm production in the combination therapy with rifampicin–colistin it is similar as the already published, however the results from the combination meropenem-colistin and its directly proportional effect in biofilm production according with the dose of carbapenem used against biofilm production of MDR A. baumannii it is a good window of opportunity for the treatment of this complex rod

César Emmanuel Lopez, Infectious Disease Resident, Infectious Disease, Instituto Nacional de Cancerología, México, Mexico, Patricia Rodriguez Zulueta, Internal Medicine Physician, Infectology, Hospital Manuel Gea Gonzalez, Mexico City, Mexico and Rigoberto Hernández Castro, PhD, Ecology of Pathogen Agents, Hosp. Manuel Gea Gonzalez, Mexico, Mexico


C. E. Lopez, None

P. Rodriguez Zulueta, None

R. Hernández Castro, None

Findings in the abstracts are embargoed until 12:01 a.m. PDT, Wednesday Oct. 7th with the exception of research findings presented at the IDWeek press conferences.