The Composition of Modified BHI Medium for Optimal Growth of Malassezia spp / 대한의진균학회지

BACKGROUND: There are several media for culture of Malassezia spp., such as Leeming & Notman (LN) medium, modified Leeming & Notman (mLN) medium, Dixon's medium and modified Dixon's medium etc. It is known that Malassezia spp. grow well in these media in general, but the kind and amounts of their ingredients are various and un-uniform according to researchers. Author propose the new and transparent BHI based medium for the optimal growth of Malassezia spp. OBJECTIVES: The purpose of this study was to design the simple and transparent BHI based medium and find essential ingredients for the growth of M. globosa and M. obtusa. METHODS: The colony size of eight standard strains (M. dermatis, M. furfur, M. globosa, M. japonica, M. obtusa, M. sloofiae, M. sympodialis, M. yamatoensis) on the modified BHI (mBHI) agar media with different ingredients was observed by naked eye after seven day culture. The compositions of mBHI medium were as follows; mBHI-1 was supplemented with 0.7% dextrose, 1.5% Tween 80, 1% glycerol to BHI medium, mBHI-2 was supplemented with 1.5% Tween 40 to mBHI-1 instead of Tween 80, mBHI-3 was supplemented with 1.5% Tween 60 to mBHI-1 instead of Tween 80, mBHI-4 was added with 0.8% bile salts to mBHI-1. mBHI-5 was supplemented with 1.5% Tween 60 to mBHI-4 instead of Tween 80, and mBHI-6 was supplemented with 1.5% Tween 40 to mBHI-4 instead of Tween 80. pH of six mBHI media was all adjusted to 6.5. RESULTS: M. furfur & M. japonica were grown well on mBHI-1 agar, but M. globosa & M. obtusa were not grown and others grown poorly. M. globosa & M. obtusa were not grown on mBHI-1 & mBHI-4 containing Tween 80 as lipid source, but others grown on all mBHI media. The media that all eight Malassezia strains grew well were slightly turbid mBHI-5 & transparent mBHI-6 medium. CONCLUSIONS: M. globosa & M. obtusa need glycerol and bile salts as well as Tween 60 or 40 instead of Tween 80 for growth. M. furfur & M. japonica need not bile salts for growth. Author proposes the transparent modified BHI medium supplemented with 0.7% dextrose, 1.5% Tween 40, 1% glycerol and 0.8% bile salts (mBHI-6) as new standard medium for culture of eight Malassezia species.

Avaliação da qualidade microbiológica de bebida láctea e creme de leite UAT por ATP-Bioluminescência / Evaluation of microbiological quality of UHT milk drink and UHT milk cream by ATP-Bioluminescence

Embora métodos tradicionais sejam utilizados na avaliação microbiológica de produtos UAT, metodologias rápidas, baseadas em ATP-Bioluminescência, têm sido desenvolvidas. Os resultados da aplicação dessa técnica em 54 amostras de bebida láctea UAT achocolatada e 12 de creme de leite UAT foram comparados com os resultados de métodos microbiológicos, utilizando-se diferentes meios de cultura e tempos de incubação das referidas amostras. A técnica de ATP-Bioluminescência foi aplicada por meio do sistema MLS, e os resultados foram expressos em unidades relativas de luz (RLU). Em todos os tempos de incubação - 48, 72 e 168 horas - , as amostras apresentaram contagens baixas de microrganismos mesófilos e psicrotróficos aeróbios quando analisadas em meio PCA, BHI, PetrifilmTM AC e por ATP-Bioluminescência (<150 RLU), demonstrando alta especificidade da técnica. Apenas uma amostra de creme de leite UAT apresentou contagem de mesófilos aeróbios acima do padrão estabelecido pela legislação brasileira (<100 UFC/mL) quando analisada em meio PCA (260 UFC/mL) e PetrifilmTM AC (108 UFC/mL), no tempo de 168 horas. Essa alta contagem de microrganismos mesófilos aeróbios também foi detectada pela técnica de ATP-Bioluminescência (416 RLU). Os resultados da técnica de ATP-Bioluminescência foram iguais aos resultados em meio PCA, BHI e PetrifilmTM AC.

Although traditional methods are used for the microbiological evaluation of UHT products, rapid methodologies based on ATP-Bioluminescence have been developed. The results of applying this technique in 54 samples of chocolate UHT milk drink and 12 of UHT milk cream were compared with the results of microbiological methods, using different culture media and incubation times for the referred samples. The ATP-Bioluminescence technique was applied through the MLS system and the results were expressed as relative light units (RLU). In all incubation times - 48, 72, and 168 hours - , the samples showed lower counts of mesophilic and psychrotrophic aerobic microorganisms when analyzed using PCA, BHI, PetrifilmTM AC and ATP-Bioluminescence (<150RLU), demonstrating the technique's high specificity. Only one sample of UHT milk cream showed a mesophilic aerobic count above the standard established by Brazilian legislation (<100CFU/mL) when analyzed in PCA (260 CFU/mL) and PetrifilmTM AC (108CFU/mL) at 168 hours. This high count of aerobic mesophilic microorganisms was also detected by the ATP-Bioluminescence (416 RLU) technique. The results of the ATP-Bioluminescence technique were equal to the results in PCA, BHI and PetrifilmTM AC.