Recurrent Klebsiella uti. C section?

On 8th day after my c section, I had uti symptoms. Urinalysis showed pus cells 20-25 and was treated with ceftas 5 days. Still symptoms persisted after antibiotics but urine culture was negative. Urinalysis showed pus cells in urine but bacteria absent. Again after 3-4 weeks , symptoms like back pain appeared. So urine routine and culture was done. Klebsiella uti was found with sensitivity to nitrofuratoin. Had it for 10 days. Urinalysis showed bacteria absent 1 weeks after this but still there was irritation. So vaginal infection was suspected and had vaginal suppository for that. But symptoms persisted. So did urine routine and culture was done on 14th week which showed infection with Klebsiella. Sensitive to nitrofurantoin. What could be the reason for repeated infection. Is it a complications from c section?