Gut bacteria of animals living in polluted environments exhibit broad-spectrum antibacterial activities

Infectious diseases, in particular bacterial infections, are the leading cause of morbidity and mortality posing a global threat to human health. The emergence of antibiotic resistance has exacerbated the problem further. Hence, there is a need to search for novel sources of antibacterials. Herein, we explored gut bacteria of a variety of animals living in polluted environments for their antibacterial properties against multi-drug resistant pathogenic bacteria. A variety of species were procured including invertebrate species, Blaptica dubia (cockroach), Gromphadorhina portentosa (cockroach), Scylla serrata (crab), Grammostola rosea (tarantula), Scolopendra subspinipes (centipede) and vertebrate species including Varanus salvator (water monitor lizard), Malayopython reticulatus (python), Cuora amboinensis (tortoise), Oreochromis mossambicus (tilapia fish), Rattus rattus (rat), Gallus gallus domesticus (chicken) and Lithobates catesbeianus (frog). Gut bacteria of these animals were isolated and identified using microbiological, biochemical, analytical profiling index (API) and through molecluar identification using 16S rRNA sequencing. Bacterial conditioned media (CM) were prepared and tested against selected Gram-positive and Gram-negative pathogenic bacteria as well as human cells (HaCaT). The results revealed that CM exhibited significant broad-spectrum antibacterial activities. Upon heat inactivation, CM retained their antibacterial properties suggesting that this effect may be due to secondary metabolites or small peptides. CM showed minimal cytotoxicity against human cells. These findings suggest that gut bacteria of animals living in polluted environments produce broad-spectrum antibacterial molecule(s). The molecular identity of the active molecule(s) together with their mode of action is the subject of future studies which could lead to the rational development of novel antibacterial(s).