The Effect of Inoculum Size on Inhibition Zones in Agar Media Using Staphylococci and Streptomycin

Cooper, K. E.; Linton, A. H.; Sehgal, Suren N.

doi:10.1099/00221287-18-3-670

Cited by 25 publications

(21 citation statements)

References 17 publications

(23 reference statements)

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“…1958). In order to verify that M. luteus is in the log phase at T c , a growth curve was experimentally generated which is shown in Fig 4…”

Section: Resultsmentioning

confidence: 99%

“…1958) have shown that the critical time of the test organism can be approximately related to its lag period ( L ) and generation time ( G ) when grown under standard conditions. Their model was verified experimentally with indicator organisms Staphylococcus aureus (Cooper et al.…”

Section: Resultsmentioning

confidence: 99%

“…Their model was verified experimentally with indicator organisms Staphylococcus aureus (Cooper et al. 1958) and Klebsiella pneumonia (Linton 1958) against the antibiotic streptomycin. They proposed that the critical time ( T c ) for visual appearance of bacterial growth could be described by eq.…”

Section: Resultsmentioning

confidence: 99%

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Modeling development of inhibition zones in an agar diffusion bioassay

Chandrasekar

Knabel

Anantheswaran

2015

Food Science & Nutrition

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A two-temperature agar diffusion bioassay is commonly used to quantify the concentration of nisin using Micrococcus luteus as the indicator microorganism. A finite element computational model based on Fick's second law of diffusion was used to predict the radius of the inhibition zone in this diffusion bioassay. The model developed was used to calculate nisin concentration profiles as a function of time and position within the agar. The minimum inhibitory concentration (MIC) of nisin against M. luteus was determined experimentally. The critical time (Tc) for growth of M. luteus within the agar diffusion bioassay was experimentally determined using incubation studies with nisin. The radius of the inhibition zone was predicted from the computational model as the location where the predicted nisin concentration at Tc was equal to MIC. The MIC was experimentally determined to be 0.156 μg mL−1, and Tc was determined to be 7 h. Good agreement (R2 = 0.984) was obtained between model-predicted and experimentally determined inhibition zone radii.

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“…1958). In order to verify that M. luteus is in the log phase at T c , a growth curve was experimentally generated which is shown in Fig 4…”

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

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Modeling development of inhibition zones in an agar diffusion bioassay

Chandrasekar

Knabel

Anantheswaran

2015

Food Science & Nutrition

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“…This technique can be combined with a two-dimensional contour map to show the effects of drug concentration and time [36]. Both methods can provide important information for PK/PD analysis [37,38].…”

Section: Discussionmentioning

confidence: 99%

Accurate assessment of antibiotic susceptibility and screening resistant strains of a bacterial population by linear gradient plate

Liu

et al. 2011

Sci. China Life Sci.

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The dynamics of a bacterial population exposed to the minimum inhibitory concentration (MIC) of an antibiotic is an important issue in pharmacological research. Therefore, a novel antibiotic susceptibility test is urgently needed that can both precisely determine the MIC and accurately select antibiotic-resistant strains from clinical bacterial populations. For this purpose, we developed a method based on Fick's laws of diffusion using agar plates containing a linear gradient of antibiotic. The gradient plate contained two layers. The bottom layer consisted of 15 mL agar containing the appropriate concentration of enrofloxacin and allowed to harden in the form of a wedge with the plate slanted such that the entire bottom was just covered. The upper layer consisted of 15 mL plain nutrient agar added with the plate held in the horizontal position. After allowing vertical diffusion of the drug from the bottom agar layer for 12 h, the enrofloxacin concentration was diluted in proportion to the ratio of the agar layer thicknesses. The uniform linear concentration gradient was verified by measuring the enrofloxacin concentration on the agar surface. When heavy bacterial suspensions were spread on the agar surface and incubated for more than 12 h, only resistant cells were able to form colonies beyond the boundary of confluent growth of susceptible cells. In this way, the true MIC of enrofloxacin was determined. The MICs obtained using this linear gradient plate were consistent with those obtained using conventional antibiotic susceptibility tests. Discrete colonies were then spread onto a gradient plate with higher antibiotic concentrations; the boundary line increased significantly, and gene mutations conferring resistance were identified. This new method enables the rapid identification of resistant strains in the bacterial population. Use of the linear gradient plate can easily identify the precise MIC and reveal the dynamic differentiation of bacteria near the MIC. This method allows the study of genetic and physiological characteristics of individual strains, and may be useful for early warning of antibiotic resistance that may occur after use of certain antimicrobial agents, and guide clinical treatment.

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“…Stab inoculation was useful for detecting such activity; it allowed inhibition which would otherwise not have been observed and directed attention to the importance of limiting diffusion in order to maintain high local antibiotic concentrations. This is important when examining organisms with similar growth rates, since a critical antibiotic concentration may be attained before growth of the sensitive population reaches a resistant level, as was found by Cooper, Linton & Sehgal (1958). These inhibitory agents were heatresistant, able to pass through cellophan, and showed considerable specificity in action when tested against resistant staphfylococcal variants.…”

Section: Discussionmentioning

confidence: 99%

Microbial Antagonism by Staphylococcus aureus

Barrow¹

1963

Journal of General Microbiology

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SUMMARYSeven strains antagonistic to indicator corynebacteria on solid media were found among 100 Staphylococcus aureus strains of human origin. These inhibitory strains all gave sharply defined inhibition zones, belonged to bacteriophage type 71, and were isolated from superficial infections. They were strongly active in direct antagonism tests against all the other ' aureus ' strains, and against some coagulase-negative staphylococci, streptococci and other Gram-positive species ; Gram-negative organisms were not susceptible. S. aureus strains producing hazy inhibition zones with corynebacteria showed similar though less extensive antibacterial activity. Inhibition by both kinds of staphylococci occurred under several different environmental conditions, but not in the presence of oleic acid. The antagonistic agents were relatively heat resistant, passed readily through cellophan, and showed considerable specificity in their action.

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The Effect of Inoculum Size on Inhibition Zones in Agar Media Using Staphylococci and Streptomycin

Cited by 25 publications

References 17 publications

Modeling development of inhibition zones in an agar diffusion bioassay

Modeling development of inhibition zones in an agar diffusion bioassay

Accurate assessment of antibiotic susceptibility and screening resistant strains of a bacterial population by linear gradient plate

Microbial Antagonism by Staphylococcus aureus

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