Effect of unsaturated fatty acids in growth inhibition of some penicillin‐resistant and sensitive bacteria

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Abstract
The growth of 2 penicillin-resistant gram-positive bacteria, Bacillus licheniformis (749/C, penicillin G-resistant) and Staphylococcus aureus (metR 18, methicillin-resistant) and 1 gram-negative strain, Escherichia coli (cloxacillin-resistant) and that of their wild counterparts was inhibited by the long-chain unsaturated fatty acids, linoleic, linolenic and arachidonic acid. The minimum inhibitory concentrations (MIC) of all the fatty acids were found to be 4-6 .mu.g/ml for S. aureus (metR 18 and wild), 8-30 .mu.g/ml for B. licheniformis (749/C and wild) and 70-90 .mu.g/ml for E. coli (cloxacillin-resistant and wild). The inhibitory activity increased as the number of double bonds in the fatty acids increased. In most instances the concentrations of fatty acids required to inhibit the growth of the penicillin-resistant strains were lower than that required for their sensitive counterparts. This inhibition of growth in the presence of fatty acids may be due to an increase in permeability of the membrane as evidenced by the measurement of the leakage of 260 nm absorbing material and fluidity.