Bacteria are the most common cause of cystitis, and may be introduced into the urinary system
for many reasons. Infections such as
chlamydia and gonorrhoea can cause symptoms similar to cystitis, particularly when they are present in young, sexually active men. You are on the right antibiotics. Plesae continue on the same.
Refer: http://www.cobfoundation.org/BC/bacterialCystitis.