Synergistic antibacterial effects of Ulva lactuca methanolic extract alone and in combination with different antibiotics on multidrug-resistant Klebsiella pneumoniae isolate

Various antibiotics are available, including gentamicin, chloramphenicol, ampicillin, amoxicillin, and streptomycin, but they have some restrictions. Many microorganisms are resistant to these medications. A new antimicrobial source must be found or developed to solve this issue. Inhere, extract from seaweeds Ulva lactuca was investigated for its antibacterial activity using a well diffusion assay against Klebsiella pneumoniae, and a promising inhibition zone diameter was recorded to be 14.04 mm. The biochemical structure of the antibacterial compound was determined via GC-MS and FTIR analysis. Also, a micro-dilution assay was used to calculate the minimum concentration that makes inhibition (MIC) to be 1.25 mg/ml from U. extract reliable to prevent the visibility of any bacterial growth, this was followed by examining the antibacterial effect of U. Lactuca methanolic extract alone and the synergetic effect of U. Lactuca methanolic extract in combination with two different antibiotics (gentamicin and chloramphenicol). This was assayed by the agar well diffusion method to achieve promising and strong inhibiting power against K. pneumoniae. It was deduced that the maximum synergism could be achieved by adding 2.5 mg/ml of Ulva methanolic extract to gentamicin (4 µg/ml), and the results were illustrated obviously via transmission electron microscope in which severe morphological deteriorations were experienced by the treated cells. From this study, we can conclude that U. lactucae extract has the power to aid antibiotics in reducing the growth of pathogenic K. pneumoniae.