The invention relates to ketolide compounds of Formula (I) and their pharmaceutically acceptable salts, solvates, hydrates, polymorphs and stereoisomers having antimicrobial activity. The invention also provides pharmaceutical compositions containing the compounds of invention and methods of treating or preventing microbial infections with the compounds of invention, wherein, T is —C*H(R1)—P-Q; R1 is hydrogen; unsubstituted or substituted lower alkyl, cycloalkyl or aryl; P is heteroaryl ring; Q is unsubstituted or substituted aryl or heteroaryl ring; and P is attached to Q via carbon-carbon link; and R3 is hydrogen or fluorine, With the provision that when R1 is hydrogen, R3 is fluorine.