Question: Does taking of antibiotics (which kill bacteria) constitute as killing, to create negative karma?
Answer: While it is difficult to draw the solid line between sentient and non-sentient lifeforms, especially at the microscopic level, very simple (i.e. less complex) organisms slant more towards non-sentient plant life than sentient animal life. Bacteria is regarded by some as more as the first. The First Precept against killing lives refers to non-killing of sentient lives.
That said, it makes sense to consume less antibiotics due to the rise of antibiotic resistance from over-consumption. Also, healthy bacteria might be killed, which in turn impairs well-being. It is surely better to focus on healthy living (especially through eating and drinking healthy, the Buddhist way), to prevent health issues, and to use more directly plant-based cures when unwell.
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