Survival of Mycoplasma hyorhinis in trypsin solutions

The survival of four strains of Mycoplasma hyorhinis in stock solutions of trypsin was tested at 22, 4 and -15 degrees C. Low (10(4)-10(5) cfu/ml) and high (10(6)-10(7) cfu/ml) initial concentrations of each strain were used, each was tested three times. A regular decrease of low and high concentrations (1 log in 10 and 20 min, respectively) was seen at 22 degrees C. At 4 degrees C the low concentrations showed a reduction of about 1 log/h, while apart from one strain high concentrations hardly decreased during the first 6 h and the survival time ranged from 24 to more than 30 h at the end of which there was a reduction of 4 logs. At -15 degrees C low concentrations survived up to 1 week in only one of the three tests, high concentrations survived for more than 12 weeks (reduction 3 logs). These latter results suggest that mycoplasmas may be present in trypsin as clumps, which deteriorate very slowly. A study was also performed to compare the sensitivity of different cultural procedures for detecting mycoplasmas.