[Optimization of the growth of Paenibacillus larvae in semi-selective media]

The sensitivity of media MYPGP, MYPGP(NALPIA) A (6 microg/ml nalidixic acid and 10 microg/ml pipemidic acid) and MYPGP(NALPIA) B (9 microg/ml nalidixic acid and 20 microg/ml pipemidic acid) for the recovery of viable spores of Paenibacillus larvae from honey, was evaluated by using different incubation times and different spore concentrations. No significant differences between incubation times, spore concentration or culture media were found. In the case of the recovery of vegetative cells from PBS at different incubation times and different dilutions no significant differences were found between the incubation times or the dilutions tested, while significant differences were found in the three media when compared with one another, MYPGP(NALPIA)B providing the lowest recovery of vegetative cells. Considering these results, we propose the use of MYPGP(NALPIA)B to recover spores of P. larvae from honey, specially for honeys with heterogeneous populations of bacterial spores; when culturing vegetative cells, MYPGP or MYPGP(NALPIA)A must be used to obtain good growth.