Effect of Chelating Agents on the Susceptibility of Some Strains of Gram-Negative Bacteria to Some Antibacterial Agents

Abstract

The effects of ethylenediaminetetraacetic acid and related chelating agents on the susceptibility of Pseudomonas aeruginosa and other strains of gram-negative bacteria to some fi-lactam antibiotics and some non-antibiotic antibacterial agents have been studied by two methods: (i) the determination of minimal inhibitory concentrations in the presence and absence of a chelating agent; and (ii) pretreatment with a chelating agent, followed by exposure for up to 120 min at 37 C to a fl-lactam drug in a nutrient medium or to the other type of antibacterial agent in a non-nutrient environment. The pretreatment technique gave the more significant results, especially with chlorhexidine, cetrimide, and benzalkonium chloride. Chelating agents that had previously been found to give a low order of activity as measured by effects on bacterial viability nevertheless appeared to induce some changes in the surface layers of the treated organisms, rendering them susceptible to sub-inhibitory concentrations of non-antibiotic drugs.Haque and Russell (2) have recently shown that two strains of Pseudomonas aeruginosa were considerably more susceptible to ethylenediaminetetraacetic acid (EDTA) and related chelating agents than were other, nonPseudomonas strains of gram-negative bacteria. Of the chelating agents studied, nitriloacetic acid (NTA) and iminodiacetic acid (IDA) had little or no inhibitory activity even when used at concentrations 10 times higher than the other substances. It was also found (2) that the two strains of P. aeruginosa were the most resistant to nonchelating antibacterial agents such as cetrimide, chlorhexidine, and benzalkonium chloride.Leive (3-5) has shown that pretreatment of Escherichia coli with EDTA rendered the cells susceptible to actinomycin D; this method has since been adopted by other workers using E. coli or other strains and various antibacterial agents (11). Thus a study has been made of the effect of pretreatment, or simultaneous treatment, with EDTA or other chelating agents on the susceptibility of P. aeruginosa and some other gram-negative strains to some fi-lactam antibiotics (cephaloridine, ampicillin, carbenicillin) and to other antibacterial agents (benzalkonium chloride, cetrimide, chlorhexidine).MATERIALS AND METHODS Bacterial strains. These consisted of P. aeruginosa NCTC 6750 and NCTC 1999, E. coli R+TEM and R-TEM, Enterobacter cloacae P99 and P99M, and Klebsiella aerogenes KJ. Cultures were grown overnight at 37 C on 150 ml of nutrient agar (Oxoid, Ltd., London) in Roux flasks; the cells were collected, washed twice with tris(hydroxymethyl)aminomethane (Tris) buffer (10-2 M, pH 7.8), and resuspended to a density of about 10' viable cells/ml in the same buffer.Antibacterial agents. Carbenicillin sodium and ampicillin sodium were purchased from Beecham

A rapid method of evaluating permeabilizing activity against Pseudomonas aeruginosa

“…aeruginosa, the OM acts as a permeability barrier to prevent the enzyme reaching the target (Nikaido and Vaara 1985;Russell and Chopra 1990). It has, however, been known for many years that cells treated with EDTA (Repaske 1956) or other chelating agents (Haque and Russell 1974) become sensitive to a range of antibacterial agents to which they are usually resistant.…”

Cysteine Depletion Causes Oxidative Stress and Triggers Outer Membrane Vesicle Release by Neisseria meningitidis; Implications for Vaccine Development

“…The second type, eOMV (extracted OMV, also referred to as native OMV) [15], [17], [23]), uses detergent-free extraction with ethylene-diamine-tetraacetic acid (EDTA) to chelate calcium and magnesium ions. This destabilizes the outer membrane which enhances eOMV release and preserves the desired biochemical and immunological properties, even though eOMV are not fully identical to sOMV [11], [24], [25], [26], [27]. The properties do change significantly when detergents are added to the extraction buffer.…”

Role of autolysins in the EDTA-induced lysis of Pseudomonas aeruginosa

“…Incubation of many Gram-negative bacteria with ethylenediaminetetraacetic acid (EDTA) results in damage to surface structures, thereby leading to leakage of intracellular solutes [1] as well as sensitization of cells to lysozyme [2,3] and various bactericides [1,[4][5][6]. In the absence of lysozyme, EDTA alone has appreciable lytic ac-tivity against Pseudomonas aeruginosa [1,3,[7][8][9][10] and this effect is enhanced by tris (hydroxymethyl)aminomethane (Tris) buffers [9,11].…”