No data exists on the activity of
biocides (
antiseptics and
disinfectants) on Rhinosporidium seeberi that causes
rhinosporidiosis in humans and animals. On account of the inability to culture R. seeberi, in vitro,
dyes were used to assess the morphological integrity and viability of
biocide-treated endospores that are considered to be the infective stage of this pathogen.
Evan's Blue (EvB) identifies the morphological integrity of the endospores while MTT (3-[4, 5-dimethylthiazol-2yl]-2, 5-
diphenyl tetrazolium
bromide) identifies metabolic activity through its reduction by cellular
dehydrogenases to microscopically visible deposits of insoluble
formazan. MTT-negativity has earlier been shown to correlate with absence of growth of yeast and mycelial fungi in culture and could thus indicate the loss of viability of MTT-negative rhinosporidial endospores.
Hydrogen peroxide,
glutaraldehyde,
chloroxylenol,
chlorhexidine,
cetrimide,
thimerosal, 70%
ethanol,
iodine in 70%
ethanol, 10%
formalin,
povidone-iodine,
sodium azide and
silver nitrate were tested on freshly-harvested endospores and all
biocides caused metabolic inactivation with or without altered structural integrity as shown by absence of MTT-staining after 3, 24 or 36 hour after exposure, while EvB stained only the endospores treated with
sodium azide,
ethanol,
thimerosal,
chloroxylenol,
glutaraldehyde and
hydrogen peroxide. With clinically useful
biocides -
chlorhexidine,
cetrimide-
chlorhexidine, 70%
ethanol,
povidone-iodine and
silver nitrate, a total period of exposure of endospores to the
biocide, for seven minutes, produced metabolic inactivation of the endospores. Anti-rhinosporidial
antiseptics that could be used in surgery on rhinosporidial patients include
povidone-iodine in nasal packs for nasal and naso-pharyngeal surgery,
chlorhexidine and
cetrimide-
chlorhexidine on the skin, while
povidone-iodine and
silver nitrate could have application in ocular
rhinosporidiosis.