Modelling the effect of pH and water activity in the growth of Aspergillus fumigatus isolated from corn silage

ALONSO, V.; CAVAGLIERI LR; RAMOS, A.J.; TORRES AM; MARIN, S.

JOURNAL OF APPLIED MICROBIOLOGY

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2017 p. 1048 - 1056

1364-5072

Aims: The aim of this work was to use mathematical kinetic modelling toassess the combined effects of aW, pH, O2 availability and temperature on thegrowth rate and time to growth of Aspergillus fumigatus strains isolated fromcorn silage.Methods and Results: A full factorial design was used in which two factorswere assayed: pH and aW. The aW levels assayed were 080, 085, 090, 092,094, 096, 098 and 099. The levels of pH assayed were 35, 4, 45, 5, 6, 7, 75and 8. The assay was performed at normal oxygen tension at 25 and 37°C, andat reduced oxygen tension at 25°C. Two strains of A. fumigatus isolated fromcorn silage were used. Kinetic models were built to predict growth of the strainunder the assayed conditions. The cardinal models gave a good quality fit forradial growth rate data. The results indicate that the environmental conditionswhich take place during silage production, while limiting the growth of mostmicro-organisms, would not be able to control A. fumigatus. Moreover, pHlevels in silage, far from limiting its growth, are also close to its optimum.Carbon dioxide at 5% in the environment did not significantly affect itsgrowth.Conclusions: A need for a further and controlled acidification of the silageexists, as no growth of A. fumigatus was observed at pH 35, as long as theorganoleptic characteristics of the silage are not much compromised.Significance and Impact of the Study: Aspergillus fumigatus is one of themajor opportunistic pathogens able to cause illness such as allergicbronchopulmonary aspergillosis, aspergilloma and invasive aspergillosis to ruralworkers. Exposure of animals to A. fumigatus spores can result in infections,particularly in those organs exposed to external invasion, such as the airways,mammary gland and uterus at birth.