Is it possible that two different people with two different DNA strands can have the same oral bacteria?
Sure. All they have to do is kiss and exchange oral fluids.
In fact, most bacteria in the mouth have been identified and are common to almost all mouths to one degree or another.
A persons specific DNA type, the strands that separate them from others and determine their characteristics and traits such as hair color, eye color, height. The STR alleles are different in every person because no two people are alike and no two people have the same repeated patterns within their 13 strands of DNA.
Bacteria that make people sick come from different sources. A person can ingest food or a beverage that has bacteria and make them sick. One bacteria that is found in some foods is salmonella. Other sources of bacteria are contaminated swimming pools or rivers in which a person can swim in. These are called waterborne diseases. Similarly, many different diseases are caused by bacteria.
It is certainly possible to find a toxic cemical that kills everything, which would include bacteria, viruses, and us as well. The whole trick of antibiotics is to find something that does kill bacteria but doesn't harm the person whose bacterial infection we are treating. In order to do this we have to find some chemical reaction that bacteria use in their normal metabolic processes, but that people do not use. So antibiotics are very…