Synergistic antimicrobial combination

Other synergistic antimicrobial combinations have been shown to be more effective than monotherapy with individual components. Trimethoprim-sulfamethoxazole has been successfully used for the treatment of bacterial infections and Pneumocystis jiroveci (carinii) pneumonia. 3-Lactamase inhibitors restore the activity of intrinsically active but hydrolyzable 3-lactams against organisms such as S aureus and Bacteroides fragilis. Three major mechanisms of antimicrobial synergism have been established ... 

Fyfe, L., Armstrong, F. and Stewart, J. (1998) Inhibition of Listeria monocytogenes and Salmonella enteriditis by combinations of plant oils and derivatives of benzoic acid the development of synergistic antimicrobial combinations. International journal of Antimicrobial Agents 9(3), 1 95-1 99. 

Co-trimoxazole consists of trimethoprim and sulphamethoxazole combined because of their synergistic antimicrobial effects. Trimethoprim is a folate antagonist that poses a teratogenic risk. 

Lambert, R.J.W., Hanlon, G.W. and Denyer, S.P. (2004) The synergistic effect of EDTA/antimicrobial combinations on Pseudomonas aeruginosa. J. Appl. Microbiol., 96, 244—253. 

One limitation is the strong flavour of vanillin at the minimal inhibitory concentrations required, but this may be partially overcome by using it in combination with other, synergistic, antimicrobials, thus lowering the effective concentrations that are necessary (Gould, 1996). 

Fig. 11.7 Diagrammatic representation of MIC values obtained with two synergistic antimicrobials, penicillin and gentamicin. The resulting graph or isobologram (A) is obtained by linking MIC values for each drug alone and in various dilution combinations. The MIC values for penicillin and gentamicin alone are 1.0 mg/L and 32 mg/L, respectively. The slope of the isobologram for purely additive or antagonistic combinations is shown by B and C, respectively.

The third group ccmsists of excipients with collateral antimicrobial activity that are principally added to dosage forms for reasons unrelated to their (sometimes weak) antimicrobial activity. For example, sodium lauiyl sulfate is known to inactivate some gram-positive bacteria. Similarly, edetate has weak antimicrobial activity, and it confers synergistic antimicrobial properties when combined with quaternary anmumium substances. In... 

In the CIT/MIT blend the chlorinated species has by far the greater biocidal efficacy but is also the less stable of the two components. Although MIT alone has relatively low antimicrobial performance it has recently been discovered that this compound has truly synergistic activity when combined with BIT and such a blend has several advantages over CIT/MIT products. 

Synergy studies are in vitro tests that attempt to measure synergistic, additive, indifferent, or antagonistic drug interactions. In general, these tests have not been standardized and have not correlated well with clinical outcome. (See section on Antimicrobial Drug Combinations for details.)... 

Edetic acid and edetates possess some antimicrobial activity but are most frequently used in combination with other antimicrobial preservatives owing to their synergistic effects. Many solutions used for the cleaning, storage, and wetting of contact lenses contain disodium edetate. Typically, edetic acid and edetates are used in concentrations of 0.01-0.1% w/v as antimicrobial preservative synergists see Section 10. 

Antimicrobial activity potassium sorbate is predominantly used as an antifungal preservative although it also has antibacterial properties. Similarly to sorbic acid, the antimicrobial activity is dependent on the degree of dissociation there is practically no antibacterial activity above pH 6. Preservative efficacy is increased with increasing temperature, and increasing concentration of potassium sorbate. The efficacy of potassium sorbate is also increased when used in combination with other antimicrobial preservatives or glycols since synergistic effects occur. Reported minimum inhibitory concentrations (MICs) at the pH values indicated are shown in Table... 

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