UTI Due To Serratia Marcescens Bacteria Post Sex. Bladder Sling Surgery Done. Treatment?

Due to bladder sling surgery, my bladder neck is at an extreme angle to the bladder and so I am susceptible to post-coital UTIs. I take macrobid post-coitus (consulted with urologist for this regimen) as prevention, as well as diligent pre-and post hygiene practices, but twice in the last six months I have had UTIs caused by the Serratia marcescens bacteria. Much of our sexual activity is oral. I suspect that transmission is from that vector, as my partner has really foul breath despite frequent brushing. I understand that the S. marcesens bacteria lives subgingivally. Would antibiotic treatment of him help? What other approaches can he take to reduce oral colonization? Thanks.