Antibiotic Activity in the Presence of Agar

Hanus, F. J.; Sands, J. G.; Bennett, E. O.

doi:10.1128/aem.15.1.31-34.1967

Cited by 16 publications

(7 citation statements)

References 16 publications

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“…Sands and Bennett (33) have demonstrated that some phenolic compounds are less inhibitory to Staphylococcus aureus in unwashed agar, and that inhibition can be restored by washing agar cubes in distilled water before adding the agar to growth media. Similar agar effects have been shown for fatty amines (23), antibiotics (15,24,38), and infectivity of Dengue virus (34). Greenberg (19) has studied removal of agar factors with water, methyl alcohol, ethyl alcohol, acetone, and butanoi.…”

Section: Agar Plug Diffusion Culturesmentioning

confidence: 55%

Comparison of Liquid and Agar‐Solidified Defined Media Regarding the Physiological Mechanism by which β‐2‐Thienylalanine Inhibits Growth of Escherichia, Shigella, and Salmonella Cultures

Brown

Tannock

Elliott

et al. 1980

Microbiology and Immunology

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Growth comparisons were made, using Shigella, Escherichia, and Salmonella cultures, in liquid and agar-solidified defined media containing fl-2-thienylalanine (/3-24). The comparisons were performed to determine the nature of growth inhibition by 13-24 under different physical growth conditions.In a plate assay, with increasing 13-2-t mixed into the agar, inhibition of Escherichia and Shigella increased. However, Salmonella cultures were not inhibited even at the highest /-2-t concentrations used. With 13-2-t added to liquid cultures, however, dose-response growth relationships were exhibited by all three genera.The differences occurring in [3-24 inhibition between liquid and plate assay conditions were not due to composition of culture plates, time of challenge of cultures with 13-24, availability of oxygen and associated differences in ratios of volume of media to available surface area, selection of mutants in the plate assay, or to extractable substances from the agar.However, when fl-2-t diffusion into the liquid medium was delayed by using agar plug diffusion cultures, a physiological mechanism was demonstrable which largely protected Salmonella cultures, but not Escherichia and Shigella cultures, from growth inhibition.

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Section: Agar Plug Diffusion Culturesmentioning

confidence: 55%

Comparison of Liquid and Agar‐Solidified Defined Media Regarding the Physiological Mechanism by which β‐2‐Thienylalanine Inhibits Growth of Escherichia, Shigella, and Salmonella Cultures

Brown

Tannock

Elliott

et al. 1980

Microbiology and Immunology

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“…A few studies have examined the influence of agar on antimicrobial activity (9,13). For example, antibiotics such as aminoglycosides and polymyxins are bound to negatively charged groups on the agar molecule (6).…”

Section: Discussionmentioning

confidence: 99%

Problems Related to Determination of MICs of Oximino-Type Expanded-Spectrum Cephems for Proteus vulgaris

Ohno

Ishii

et al. 2000

J Clin Microbiol

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During in vitro susceptibility testing of clinical isolates ofProteus vulgaris, we noted that the MICs of several expanded-spectrum cephems were much higher in the broth microdilution method than in the agar dilution method (termed the MIC gap phenomenon). Here we investigated the mechanism of the MIC gap phenomenon. Cephems with the MIC gap phenomenon were of the oximino type, such as cefotaxime, cefteram, and cefpodoxime, which serve as good substrates for inducible class A β-lactamase (CumA) enzymes produced by P. vulgaris; this finding suggests a relationship between the MIC gap phenomenon and CumA. Since peptidoglycan recycling shares a system common to that inducing CumA, we analyzed the mechanism of the MIC gap phenomenon using P. vulgaris B317 and isogenic mutants with mutations in the peptidoglycan recycling and β-lactamase induction systems. The MIC gap phenomenon was observed in the parent strain B317 but not in B317G (cumG-defective mutant; defective peptidoglycan recycling) and B317R (cumR-defective mutant; defective CumA transcriptional regulator). No β-lactamase activity was detected in B317G and B317R. β-Lactamase activity and the MIC gap phenomenon were restored in B317G/pMD301 (strain transcomplemented by a clonedcumG gene) and B317R/pMD501 (strain transcomplemented by a cloned cumR gene). MICs determined by the agar dilution method increased when lower agar concentrations were used. Our results indicated that the mechanism of the MIC gap phenomenon is related to peptidoglycan recycling and CumA induction systems. However, it remains unclear how β-lactamase induction of P. vulgaris is suppressed on agar plates.

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“…Agarose probabiy affects germination by interfering with the cation supply of P. hyoscyami. Hanus et al (1967) noted that divalent cations, including calcium and magnesium, were often bound to agar. The purification process used to prepare agarose from agar involves chemically removing all impurities and undesirable components (Duckworth & Yaphe, 1971).…”

Section: Discussionmentioning

confidence: 99%

Inhibition of germination of sporangia of Peronospora hyoscyami by cation deprivation: the effects of substrate and chelating agents

Johnson

1988

Plant Pathology

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Germination of sporangia of Peronospora hyoscyami de Bary (tobacco blue mould) was affected by the germination substrate. Washed sporangia germinated freely in water on glass slides, but failed to germinate on agarose. Germination was reduced on detached tobaceo leaves, being lower on cv. Hicks Q46 than on cv. ZZIOO. Inhibition of germination by agarose was reversed by the addi'.ion to the inoculum of an extract obtained by centrifuging a suspension of non-living, powdered torula yeast Candida utilis (Hennenberg) Lodder & van Rij. Yeast extract also improved germination in vivo. The siderophore rhodotorulic aeid, the chelating agents ferric and sodium citrate, and riboflavin eombined with calcium and magnesium salts, also stimulated germination of sporangia on agarose. The chelating agent ethylenediaminetetraaeetic acid (EDTA) inhibited germination on glass slides. Inhibition by EDTA was partially reversed by the addition of ferric salts. The inhibition of germination by agarose and stimulation by additives may have been due to efleets on the availability of cations to sporangia of P. hyoscyami. The reduetion in germination on tobacco leaves may have involved a similar mechanism.

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Antibiotic Activity in the Presence of Agar

Cited by 16 publications

References 16 publications

Comparison of Liquid and Agar‐Solidified Defined Media Regarding the Physiological Mechanism by which β‐2‐Thienylalanine Inhibits Growth of Escherichia, Shigella, and Salmonella Cultures

Comparison of Liquid and Agar‐Solidified Defined Media Regarding the Physiological Mechanism by which β‐2‐Thienylalanine Inhibits Growth of Escherichia, Shigella, and Salmonella Cultures

Problems Related to Determination of MICs of Oximino-Type Expanded-Spectrum Cephems for Proteus vulgaris

Inhibition of germination of sporangia of Peronospora hyoscyami by cation deprivation: the effects of substrate and chelating agents

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