In vitro Ascertainment of Interactions between Kanamycin and Adjuvants against Various Bacterial Species

Background: In recent times, there has been incontrovertible evidence regarding the propensity of various bacteria that barge through the immune system of an already debilitated individual. In this regard, combination therapy presents us with a more effective approach than conventional monotherapy. A specific combination of antibiotics exhibits a synergistic antibacterial effect, which can be seen with kanamycin, which shows moderate antibacterial activity alone but acts synergistically with particular adjuvants, displaying a high degree of antibacterial activity. Objective: This study aimed to carry out an in vitro evaluation of the interaction between kanamycin and adjuvants against various bacterial species. Methods: The interaction between kanamycin and adjuvants against various bacterial isolates was determined by checkerboard assay, and the synergistic interactions were further evaluated by time-kill kinetic assay under in vitro settings. Results: The interaction between kanamycin and citric acid was found to be synergistic against all strains of E. coli. Both kanamycin and citric reduced their MICs by at least 4 fold in combination. This synergistic interaction was further confirmed by the time-kill kinetic assay. The result of time kill kinetic assay of combination revealed that at MIC, there was a 2.36 log10 CFU/ml reduction compared to kanamycin (the most active antimicrobial agent alone), at 24 hours at 2 fold MIC, 2.41 log10 CFU/ml reduction was seen in comparison to kanamycin at 24 hours at its one fold MIC. For other bacterial species, the combination of citric acid and kanamycin showed additive or indifferent interactions. In the case of our second combination (kanamycin and sodium salicylate), all the bacterial species displayed additive and indifferent interaction. Conclusion: It has been concluded that the combination of kanamycin and citric acid (adjuvant) demonstrated a remarkable synergistic interaction against E. coli.