In vitro activity of ceftazidime, ciprofloxacin, meropenem, minocycline, tobramycin and trimethoprim/sulfamethoxazole against planktonic and sessile Burkholderia cepacia complex bacteria.
OBJECTIVE
The goal of the present study was to obtain a comprehensive overview of the bacteriostatic and bactericidal effects of six commonly used antibiotics on planktonic as well as on sessile Burkholderia cepacia complex cells.


METHODS
The bacteriostatic and bactericidal activities of ceftazidime, ciprofloxacin, meropenem, minocycline, tobramycin and trimethoprim/sulfamethoxazole were determined against 38 B. cepacia complex strains. MICs and minimal biofilm inhibitory concentrations (MBICs) were determined using a traditional broth microdilution method and a novel resazurin-based viability staining, respectively. The bactericidal effects of the investigated antibiotics (using antibiotic concentrations corresponding to 10 x MIC; except for tobramycin, for which a final concentration of 4 x MIC was tested) on stationary phase planktonic cultures and on 24-h-old biofilms were evaluated using conventional plate count methods.


RESULTS
Our results confirm the innate resistance of B. cepacia complex organisms to six first-line antibiotics used to treat infected cystic fibrosis patients. All antibiotics showed similar bacteriostatic activities against exponentially growing B. cepacia complex planktonic cells and freshly adhered sessile cells (4 h). In addition, most of the antibiotics showed similar bactericidal effects on stationary phase planktonic cultures and on young and older biofilms.


CONCLUSIONS
Despite the general assumption that sessile cells show a decreased susceptibility to antibiotics, our data indicate similar bacteriostatic and bactericidal activity of six selected antibiotics against planktonic and sessile B. cepacia complex bacteria.
Peeters
Elke
E
Laboratory of Pharmaceutical Microbiology, Faculty of Pharmaceutical Sciences, Ghent University, Ghent, Belgium.
Nelis
Hans J
HJ
Coenye
Tom
T
D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D018441:Biofilms / Q000187:drug effects / Q000254:growth & development; D042602:Burkholderia cepacia complex / Q000187:drug effects* / Q000254:growth & development; D015169:Colony Count, Microbial; D008826:Microbial Sensitivity Tests / Q000379:methods; D050296:Microbial Viability / Q000187:drug effects
D000900:Anti-Bacterial Agents