<prompt> Which of the following is not an established antimicrobial drug synergism at clinical level?Amphotericin B and flucytosine in cryptococcal meningitisCarbenicillin and gentamicin in pseudomonal infectionsPenicillin and tetracycline in bacterial meningitisTrimethoprim and sulfamethoxazole in coliform infections  <response>: Combination of a bacteriostatic and a bactericidal drug in most cases is antagonistic. Bactericidal drugs act on fast multiplying organisms whereas bacteriostatic drugs inhibit the growth. Here, penicillins are bactericidal whereas tetracyclines are bacteriostatic. 