An improved method for in vitro susceptibility testing of Trichomonas vaginalis

A protocol is presented for in vitro susceptibility testing of Trichomonas vaginalis. A 100 ml culture of the microorganisms is prepared for inoculation into antibiotic dilutions and controls by centrifugation, washing with 10 mM HEPES (pH 6.2) plus 1.5 x 10(-1) M NaCl, a second centrifugation and a resuspension in the HEPES-saline buffer. Inclusion of the gelling agent carrageenan in the culture medium permits an ease of harvesting the trichomonads and a reproducible initial cell density of 1-4 x 10(4) cells per ml. Following inoculation, tubes with antibiotic dilutions and controls are incubated anaerobically at 35 degrees C for 48 h, which corresponds to late exponential phase. Inclusion of a negative control helps determine Minimum Lethal Concentration (MLC) values.