host-associated 1,538 animal host 1,538 digestive tract 1,538 intestine 1,538 mammalian host 1,536 human host 1,518 industrialized 1,361 adult 819 urban 264 elderly 111 child 44 infant 40 adolescent 37 rural 26 non-industrialized 21 full term birth 8 preterm birth 1 traditional agriculturalist 1