There are provided methods and pharmaceutical compositions for the treatment or prevention of conditions associated with infection by Chlamydia species or similar susceptible microorganisms in a patient in need of such treatment or prevention. The methods of the invention comprise the administration to the patient of an effective amount of at least two different antibiotics or antimicrobial agents selected from the group consisting of tetracyclines, macrolides, quinolones, chloramphenicol, rifamycins, sulfonamides, co-trimoxazole and oxazolidinones. Compositions of the invention comprise at least two antibiotics or antimicrobial agents selected from the group consisting of tetracyclines, macrolides, quinolones, chloramphenicol, rifamycins, sulfonamides, co-trimoxazole and oxazolidinones.