Antibiotic susceptibility of Gram-negative bacteria in cerebrospinal fluid compared with Mueller-Hinton broth and...

Antibiotic resistance in Gram-negative bacteria has become an increasing problem in the treatment of critically ill patients, particularly in central nervous system infections. In clinical practice, MICs and minimal bactericidal concentrations are usually determined in standard test media and not in the respective body fluids.

MICs and minimal bactericidal concentrations were tested in human cerebrospinal fluid (CSF), Mueller-Hinton broth (MHB), and artificial cerebrospinal fluid by microdilution for 24 h at 37°C in room air supplemented with 5% CO₂.

Cefotaxime, ceftazidime, and ciprofloxacin inhibited the growth of Pseudomonas aeruginosa, cefotaxime, ceftazidime and amikacin inhibited the growth of Morganella morganii, and amikacin inhibited the growth of Acinetobacter baumannii in the nutrient-deficient CSF medium at lower concentrations than the MICs determined in MHB. The differences in MIC between MHB and artificial cerebrospinal fluid were less pronounced than between MHB and human CSF.

In central nervous system infections, when antimicrobial susceptibility testing in standard media does not result in adequate therapeutic options, we suggest testing the antimicrobial susceptibility of the causative bacterium in human CSF.