Horizontal gene transfer is pretty new to a lot of people. It’s now known that bacteria can easily transfer it’s genes without reproduction and I think even between species. In fact, it’s my understanding that this may be the most common way that genes are transferred in single felled organisms, but I’m not sure how similar bacteria have to be in order to do this. Recently, someone I know had MRSA and coincidental strep. Could that strep have become resistant from the MRSA?
Resistant to what, exactly? (Not trying to be pedantic, but “MRSA” is often used as a generic label for “scary S. aureus resistant to lots of stuff” rather than “methicillin resistant in particular”.)
Is it likely that it happened in this particular case? No - exceedingly unlikely. Can it happen in the lab? Under certain specific conditions, yes. Does it happen “in the wild”? A qualified “yes”: transfer of the vancomycin gene cassette between bacterial species as far apart as Staphylococcus and Streptococcus has been reported, but the incidence appears low. (See this link for details.)
What types of things are favorable for horizontal gene transfer? Presumably, closely related species are better at transferring genes from one species to another, but can some completely unrelated species transfer easier than others?
Oh, as far as “resistant to what” I have no idea. She’s getting better in reasonable time, so not the uber scary type.