Retaking Doxycycline, will it kill Acne bacteria or am I resistant to it?

i have used doxycycline for 6 weeks before 9 months but when i caught this medication the acne return . and now i changed the Dr anh prescribed to me Doxycycline for 3 months and i have to see ack after this period. i just wanna know if i retake this medication now will it give an effect or the bacteria did resistance for it ?

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