What Causes Infection Over The Stitches In Vaginal Region?

sir, i hv infection over the stiches in the vaginal region that was put during the time of delivery. I t was a normal delivery which happened on 23rd dec 2008. After six months of delivery i first noticed the infection and has taken some medicines upon prescription for cure, but the problem was not sloved. It gets healed up when i take the medicine and the problem repeats once in every 4-6 months. Finally in the month of 0ct 2010, i got tissue culture test done of the pus sample and it was determined as bcoz of the organism "enterobacter s m" and it was scanty and my doctor has prescribed ciplox 500mg and rantac 150mg twice a day for a week. i felt the problem has solved but again now i hv noticed the infection bit severe compared to the previous infections. plz let me know what the problem exactly is and kindly suggest me the solution as well.