Evaluation of antimicrobial activity of certain combinations of antibiotics against in vitro Staphylococcus epidermidis biofilms.
OBJECTIVE
Staphylococcus epidermidis is the most common pathogen associated with infections of surgical implants and other prosthetic devices owing to its adhesion and biofilm-forming ability on biomaterials surfaces. The objective of this study was to compare susceptibilities of biofilm-grown cells to single antibiotic and in combination with others to identify those that were effective against S. epidermidis biofilms.


METHODS
Biofilms were grown in the MBEC™ assay system. The use of this methodology allowed a rapid testing of an array of antibiotics alone (eight) and in combination (25 double combinations). The antibacterial effect of all treatments tested was determined by colony forming units (cfu) enumeration method.


RESULTS
The MBEC™ assay system produced multiple and reproducible biofilms of S. epidermidis. Although none of the antibiotics tested have demonstrated an antimicrobial effect (log reduction >3) against all S. epidermidis isolates biofilms, but combinations containing rifampicin showed in general a broader spectrum namely rifampicin-gentamicin and rifampicin-clindamycin. Levofloxacin in combination with rifampicin showed a killing effect against three isolates but failed to attain a bactericidal action against the other two.


CONCLUSIONS
Our findings showed that rifampicin should be a part of any antibiotic therapy directed against S. epidermidis biofilms. However, the efficient antibiotics combination might be dependent on S. epidermidis isolate being tested.
IBB-Institute for Biotechnology & Bioengineering, Centre of Biological Engineering, University of Minho, Braga, Portugal.
Fernanda
F
Gomes
Pilar
P
Teixeira
Howard
H
Ceri
Rosário
R
Oliveira
D018441:Biofilms / Q000187:drug effects / Q000254:growth & development; D002981:Clindamycin / Q000494:pharmacology; D004338:Drug Combinations; D005839:Gentamicins / Q000494:pharmacology; D006801:Humans; D064704:Levofloxacin; D008826:Microbial Sensitivity Tests; D015242:Ofloxacin / Q000494:pharmacology; D012293:Rifampin / Q000494:pharmacology*; D013203:Staphylococcal Infections / Q000188:drug therapy / Q000382:microbiology; D013212:Staphylococcus epidermidis / Q000187:drug effects / Q000254:growth & development
D004338:Drug Combinations; D005839:Gentamicins; D002981:Clindamycin; D064704:Levofloxacin; D015242:Ofloxacin; D012293:Rifampin