In-vitro inhibitory activity of gamma-linolenic acid on Escherichia coli strains and its influence on their susceptibilities to various antimicrobial agents.
Recent experimental evidence implies that polyunsaturated fatty acids (PUFAs) possess anti-infective activity which is unrelated to any alteration of eicosanoid biosynthesis or cytokine production provoked by PUFAs and it seems necessary to establish their possible influence on Gram-negative bacteria. Forty-two Escherichia coli strains were cultured in vitro in the presence of gamma-linolenic acid (GLA) at concentrations of 50 mg/L and 300 mg/L and a total of 77 killing curves were performed with GLA concentrations of 100, 200 and 300 mg/L GLA. At 50 and 300 mg/L, GLA inhibited 9.5% and 33.3% of strains respectively; GLA killing curves demonstrated a > or = 1 log GLA inhibitory effect in 0%, 18.2% and 72.7% of strains after the 5 h sequential exposures at 100, 200 and 300 mg/L GLA but this was not observed after the 24 h GLA exposure. Following removal of the E. coli strains from the culture medium with GLA, > or = four-fold increases in MICs and/or MBCs of various antimicrobials, were observed in 42.9% and 60% of strains after exposure to 50 and 300 mg/L GLA respectively; most of these increases involved aminoglycosides. The reproducibility of GLA inhibitory effects and increase in MICs and/or MBCs for E. coli in the two different experimental procedures used, was 82% and 73% respectively. Further studies are necessary to clarify the mechanism of GLA action on E. coli and assess the clinical relevance of these findings.
First Department of Propedeutic Medicine, Laiko General Hospital, Athens, Greece.
E J
EJ
Giamarellos-Bourboulis
P
P
Grecka
A
A
Dionyssiou-Asteriou
H
H
Giamarellou
D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001437:Bacteriuria / Q000382:microbiology; D004357:Drug Synergism; D004926:Escherichia coli / Q000187:drug effects*; D006090:Gram-Negative Bacteria / Q000187:drug effects; D006801:Humans; D008826:Microbial Sensitivity Tests; D017965:gamma-Linolenic Acid / Q000494:pharmacology*
D000900:Anti-Bacterial Agents; D017965:gamma-Linolenic Acid