Changes in Preservative Sensitivity for the USP Antimicrobial Agents Effectiveness Test Micro‐organisms

Al-Hiti, Mustafa M.; Gilbert, Peter

doi:10.1111/j.1365-2672.1980.tb01049.x

Cited by 23 publications

(8 citation statements)

References 12 publications

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“…In a chemostat the medium has an excess of all nutrients except for one at a growth-limiting concentration. The existence in a chemostat of an equilibrium cell mass is a consequence of the exponential loss of cells resulting from the dilution rate (D) (volume changes per hour) being equal to the specific growth rate (1) and related to td as D = ,u = ln2/td. Thus, the chemostat enables the study of growth rate effects per se.…”

Section: Introductionmentioning

confidence: 99%

Influence of growth rate on susceptibility to antimicrobial agents: modification of the cell envelope and batch and continuous culture studies

Brown

Collier

Gilbert

1990

Antimicrob Agents Chemother

188

103

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Section: Introductionmentioning

confidence: 99%

Influence of growth rate on susceptibility to antimicrobial agents: modification of the cell envelope and batch and continuous culture studies

Brown

Collier

Gilbert

1990

Antimicrob Agents Chemother

188

103

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“…All three sets of conditions significantly reduced the degree of bactericidal activity. Such effects were particularly marked 'W0 '2 '4 '6 '8 lo 12 1 Bronopol pg/ml FIG. 1.…”

Section: Resultsmentioning

confidence: 99%

Antibacterial action of 2-bromo-2-nitropropane-1,3-diol (bronopol)

Shepherd

Waigh

Gilbert

1988

Antimicrob Agents Chemother

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Patterns of growth inhibition of Escherichia coli in the presence of 2-bromo-2-nitropropane-1,3-diol (bronopol) indicate a period of biocide-induced bacteriostasis followed by growth at an inhibited rate. The length of the bacteriostatic period, but not the subsequent growth inhibition, was reduced by the addition of excess cysteine. Patterns of growth inhibition were unaffected by catalase or superoxide dismutase. The bactericidal concentrations (100 to 500 ,ug/ml) were considerably in excess of the MIC (13 ,ug/ml) and generally produced first-order reductions in viability. Bactericidal activity was considerably reduced by anoxic conditions and by the presence of catalase or superoxide dismutase. Results indicate that there are two distinct reactions between bronopol and thiols. Under aerobic conditions, bronopol catalytically oxidizes thiolcontaining materials such as cysteine, with atmospheric oxygen as the final oxidant. By-products of this reaction are active oxygen species such as superoxide and peroxide, which are directly responsible for the bactericidal activity of the compound and for the reduced growth rate after the bacteriostatic period. The latter effect probably results from the oxidation of intracellular thiols such as glutathione and cysteine. Catalytic oxidation of thiols in the presence of excess thiol leads to the creation of an anoxic state. Under these conditions, the slower reaction with thiols, which consumes bronopol, predominates. Consumption of bronopol by its reaction with thiols, without the involvement of oxygen, leads to the eventual removal of bronopol from treated suspensions and the resumption of growth.2-Bromo-2-nitropropane-1,3-diol (bronopol) has a broad spectrum of antibacterial activity (12) and is widely used, at concentrations of up to 0.1% (wt/vol), as a preservative for pharmaceutical and cosmetic products (4, 15). Previous studies of the mechanism of action of bronopol all conclude that the antibacterial activity of bronopol relates to its interaction with essential thiols within the cell (3,16,18). Such interaction is thought to lead to the oxidation of thiols through a radical anion intermediate (11). Unlike other thiol-interactive antimicrobial agents, bronopol possesses significant bactericidal activity that cannot be explained solely in terms of thiol oxidation. This paper examines the hypothesis that separate actions are responsible for the growth inhibitory and bactericidal activities of the compound. MATERIALS AND METHODSOrganisms, chemicals, and culture maintenance. Escherichia coli ATCC 8739 was used throughout the study. Cultures were maintained on nutrient agar (Oxoid CM 3) slopes at room temperature in the dark after incubation at 35°C. 2-Bromo-2-nitropropane-1,3-diol (bronopol) was obtained from the Boots Chemical Co., Nottingham, England. Catalase, superoxide dismutase, cytochrome c, cysteine, cystine, cysteine hydrochloride, and cystine dimethyl ester were obtained from the Sigma Chemical Co., St. Louis, Mo. All other reagents were of the purest avail...

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“…Microorganisms were grown in an orbital incubator within 100‐ml volumes of a simple salts medium (Al‐Hiti and Gilbert 1980) in 250‐ml Erlenmeyer flasks. The medium facilitated growth to an O.D.…”

Section: Preparation Of Inoculamentioning

confidence: 99%

A rapid method for the evaluation of both extrinsic and intrinsic contamination and resulting spoilage of water-in-oil emulsions

2004

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Aims: To develop a method for studying the microbial spoilage of water-in-oil emulsions and to use this to investigate (i) the intrinsic stability of water-in-oil formulations and (ii) Pseudomonas aeruginosa SP1-induced spoilage of a proprietary emulsion. Methods and Results: Aliquots of test emulsion were placed into wells of a microtitre plate and the opacity (492 nm) monitored at 120-min intervals over several hours. Cracking of the emulsion was associated with marked reductions in opacity. Rate and extent of change in O.D. could be used as indicators of spoilage. Spoilage of a laboratory emulsion formulation was investigated where microorganisms with demonstrated spoilage potential were incorporated either into the water phase prior to emulsification or where the proportion of contaminated water droplets was varied by dilution of contaminated emulsion with a sterile formulation. Results suggested that the route of introduction was a critical determinant of the probability of gross spoilage. Ps. aeruginosa SP1-induced spoilage of a proprietary formulation was found to be independent of growth in the formulation; rather it was attributed to the presence of a heat-labile extracellular spoilage-factor that was protease labile and possessed both lipase and polysorbate hydrolytic activity. Such spoilage potential was unique to one Ps. aeruginosa culture filtrate amongst five pseudomonads tested. Significance and Impact of the Study: The method is both rapid and reproducible, enables evaluation of the effects of route of contamination upon emulsion spoilage and has potential application in formulation development for cosmetic, pharmaceutical and food products.

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Changes in Preservative Sensitivity for the USP Antimicrobial Agents Effectiveness Test Micro‐organisms

Cited by 23 publications

References 12 publications

Influence of growth rate on susceptibility to antimicrobial agents: modification of the cell envelope and batch and continuous culture studies

Influence of growth rate on susceptibility to antimicrobial agents: modification of the cell envelope and batch and continuous culture studies

Antibacterial action of 2-bromo-2-nitropropane-1,3-diol (bronopol)

A rapid method for the evaluation of both extrinsic and intrinsic contamination and resulting spoilage of water-in-oil emulsions

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