Diarrhoeal infections are major cause of morbidity and mortality of children globally
[1]. Moreover, emerging antibiotic resistance complicates diarrhoea treatment. Combination
of compounds and antibiotics is considered as a new prospective strategy for overcoming
bacterial resistance. For example, augmentin (amoxicillin and clavulanic acid) is
used to treat certain bacteria-caused diseases such as urinary tract infections. In
long time practice, various plant-derived compounds such as berberine sulphate and
berberine hydrochloride are useful for diarrhoea control [2]. However, their combinatory effect with conventional antibiotics against diarrhoea
causing bacteria has only poorly been investigated.
In this study, we tested in vitro combinations of plant compounds (e.g. berberine chloride, tannic acid and sanguinarine)
and their derivatives (e.g. 4, 8-hydroxy-5-nitroquinoline and zinc pyrithione) with
selected conventional antibiotics (e.g. ciprofloxacin and tetracycline) against standard
strains of diarrheagenic bacteria (e.g. Escherichia coli and Shigella sp.). Minimum inhibitory concentrations of each agent and antibiotics were determined
by the broth microdilution method according to Clinical and Laboratory Standards Institute
[3] guidelines, whereas the combinatory effect was evaluated according to the sum of
fractional inhibitory concentration (ΣFIC) indices obtained by chequerboard method
[4].
Several combinations (e.g. sanguinarine with tetracycline) showed additive effects
against the majority of bacterial strains tested with ∑FICI ranging from 0.507 to
0.531, whereas the synergistic activity exhibited combination of sanguinarine with
ciprofloxacin (∑FICI 0.281 - 0.375) against Vibrio parahaemolyticus and Shigella flexneri.
The results can be used by food and pharmaceutical industries for development of new
herbal-based food and pharmaceutical preparations.
