Susceptibility of Escherichia coli, Salmonella sp. and Clostridium perfringensto organic acids and monolaurin

Abstract

The antimicrobial activity of fatty acids, monolaurin, citric, succinic, fumaric, malic and lactic acid was determined in cultures of two strains of Escherichia coli, three strains of Salmonella sp. and two strains of Clostridium perfringens. Antimicrobial activity was expressed as minimum inhibitory concentration (MIC) that prevented growth and glucose utilization in treated cultures. Caprylic acid was the only acid inhibiting glucose utilization in all cultures. Its MIC varied from 1 to 3 mg/ml. Strains CCM 3954 and CCM 4225 of E. coli were inhibited also by capric acid at 5 mg/ml. Strains CCM 4435<sup>T </sup>and CNCTC 5459 of Cl. perfringens were inhibited by medium-chain fatty acids (C<sub>8</sub> to C<sub>14</sub>), oleic acid and one strain also by linoleic acid. The minimum MICs were those of lauric and myristic acid (between 0.1 and 0.2 mg/ml). Growth of Cl. perfringens, but not other bacteria, was inhibited also by monoglyceride of lauric acid (MIC = 3 mg/ml), and by citric acid (MIC = 4 mg/ml). Inhibitory effects of other acids were not observed at 5 mg/ml. Caprylic and lauric acid did not influence the K<sup>+ </sup>permeability of the cytoplasmic membrane in cells of E. coli CCM 4225 and Cl. perfringens CCM 4435<sup>T</sup>, respectively. In cultures of both strains of E. coli treated with caprylic acid at 5 mg/ml, and in those of Cl. perfringens CCM 4435<sup>T </sup>treated with lauric acid at 1 mg/ml, or with its monoglyceride at 5 mg/ml, the transmission electron microscopy revealed damage of cytoplasmatic structures. In cells of Cl. perfringens the separation of inner and outer membranes was apparent, the integrity of the outer membrane, however, was maintained. It can be concluded that medium-chain fatty acids are more efficient antimicrobials than other, more polar organic acids tested.

Antimicrobial Effects of 1-Monocaprylin and 1-Monocaproin Through <i>in vitro</i> Growth Inhibition and Molecular Docking Studies

“…There were lot published literatures to prove the inhibitory property of various MAGs against Grampositive bacteria (Kabara et al, 1972;Schlievert et al, 1992;Oh and Marshall, 1993;Branen and Davidson, 2004;Bunkova et al, 2011) and the resistant property to Gramnegative bacteria (Skrivanova et al, 2006;Kabara, 1978;Kabara, 1984). Based on detailed published studies of saturated fatty acids with chain lengths between 6 and 18 carbons, the lauric acid was found to possess more inhibitory activity against Gram-positive bacteria (Kabara et al, 1972) and MAG synthesized with caproic acid and caprylic acid in our study were found to show similar inhibitory effect.…”

Comparison of antibacterial effect of seven 1-monoglycerides on food-borne pathogens or spoilage bacteria

“…Růžička et al (2003) did not detect an inhibitory effect of MAG-C12:0 on E. coli or Klebsiella pneumoniae. No inhibitory effect of the same MAG against Salmonella, Escherichia and Klebsiella was observed (McLay et al 2002;Marounek et al 2003;Preuss et al 2005;Skrivanova et al 2006). It was possible to enhance the antimicrobial effect of 1-monoglycerides on enterobacteria by other factors, e.g.…”

“…Under certain conditions, fatty acids and monoglycerides can inhibit the growth of vegetative forms of pathogenic bacteria, viruses (Thormar and Hilmarsson 2007), spore-forming bacteria (Mansour et al 1999;Skrivanova et al 2006) or yeasts (Bergsson et al 2001). However, food composition can influence the inhibitory effect of both monoglycerides and fatty acids.…”

In vitro combined effect of oregano essential oil and caprylic acid against Salmonella serovars, Escherichia coli O157:H7, Staphylococcus aureus and Listeria monocytogenes

“…It has been suggested that the antimicrobial activity of medium-chain fatty acids is targeted on cell membrane, leading to disruption of electron transport chain and disruption of oxidative phosphorylation (Desbois and Smith 2010). In a study with C 2 -C 18 fatty acids caprylic acid was the most effective against Salmonella serovars and E. coli (Skřivanová et al 2006).…”