Cerclage during 24 weeks

Hi,

My cervix is 3.5cm @ 13 weeks, 3.0cm@16 weeks.
now i am 21weeks and dr told i have got short cervix , immediate cerclage has to be placed. Unfortunately, my urine culture test showed i have got e.coli infection and dr prescribed tablets for 5 days. after a week if the test is ok, they will place the cerclage..
Is it ok if cerclage is placed @ 24 week?

What to do to avoid the infection? is taking tablets alone sufficient?
I am on complete bed rest for the past 2 months..waking only for bath..
Need your suggestion.

Thanks..