In vitro interaction of ampicillin with ciprofloxacin or spiramycin as determined by the decimal assay for additivity technique

  • CO Esimone Department of Pharmaceutical Microbiology Unit, Department of Pharmaceutics, University of Nigeria, Nsukka, Nigeria
  • IR Iroha
  • OC Okeh
  • IG Ude
  • MU Adikwu


The in vitro interactions of Ampicillin (AMP) with Ciprofloxacin (CIP) and Ampicillin with Spiramycin (SPIR) were evaluated against Staphylococcus aureus ATCC 12600 using the Decimal Assay for Additivity (DAA) technique. Most of the combinations of CIP/AMP with Biological Equivalent Factor (BEF) (5/30mg) or SPIR/AMP with biological equivalent factor (BEF) (10.96/30mg) against Staphylococcus aureus ATCC 12600 showed synergism. Given that the test organism was intrinsically resistant to either SPIR or AMP alone (MIC, 15.6 and 23.4 µg/ml respectively), the observed in vitro synergism could be therapeutically exploited. Moreover, the present data further authenticates the potential applicability of the DAA technique in selecting suitable antibiotic combinations prior to combined antimicrobial therapy.

Keywords: decimal assay for additivity (DAA), antibiotic interaction, Ciprofloxacin, spiramycin, ampicillin

Nigerian Journal of Health and Biomedical Sciences Vol. 5(1) 2006: 12-16

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eISSN: 1595-8272