Hi, I Had A Surgery For Pilonidal Sinus Two Years

Hi,
I had a surgery for pilonidal sinus two years back with wide excision and healing by secondary intention.
Since then the wound in natal cleft was not healed. The wound was healing and opening again time after time for 2 years. 3 months back, I started using mupirocin topical antibiotic ointment as it was suggested by a dermatologist. He asked me to use it for 7 days. The ointment worked very good and I saw a lot of improvement after using it for 7 days. So, in the fear of getting the wound open again, I have been using it for 3 months till now. Recently I came to know that excessive use of mupirocin can lead to antibiotic resistance such as MRSA. Is this true? Will 3 months use of mupirocin long enough to develop resistant bacteria?
Thanks.