In vitro susceptibility of Prototheca spp. to gentamicin

One hundred strains of Prototheca zopfii, Prototheca wickerhamii, Prototheca moriformis, Prototheca stagnora, and Prototheca ulmnea; five strains of Chlorella protothecoides; and two strains of Candida albicans were obtained from a number of different clinical and environmental sources and were tested for their in vitro susceptibility to the antibacterial agent gentamicin. All Prototheca strains were susceptible to gentamicin at concentrations between 0.3 and 0.9 micrograms/ml. A modified macrobroth dilution MIC assay with a colorimeter and a microbroth dilution assay with a 96-well plate reader were the two methods used to determine the MICs.