A numerical method to determine minimal inhibitory concentrations (MICs) of antibiotics directly from disc-diffusion susceptibility tests

Awerbuch, Tamara; Lustman, Levi; Piret, Jacqueline

doi:10.1016/0167-7012(89)90024-9

Cited by 10 publications

(6 citation statements)

References 7 publications

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“…Sensitivity to common commercial antibiotics was tested according to disc diffusion assay (Awerbuch et al , 1988), using paper discs containing the following concentrations of antibiotics (Oxoid, Basingstoke, Hants, UK): TE30 – tetracycline, 30 μg; SXT25 – sulphamethoxazole trimethoprim, 25 μg; NA30 – nalidixic acid, 30 μg; E15 – erythromycin, 15 μg; C30 – chloramphenicol, 30 μg; MET5 – methicillin, 5 μg; AMP10 – ampicillin, 10 μg. After spreading 100 μL of the tested isolates on a 50% marine agar plate, antibiotic discs were placed on top of the agar for a 24‐h period of incubation.…”

Section: Methodsmentioning

confidence: 99%

Coral mucus-associated bacteria: a possible first line of defense

Shnit-Orland

Kushmaro

2009

FEMS Microbiology Ecology

311

227

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Interactions among microorganisms found in coral mucus can be either symbiotic or competitive. It has been hypothesized that microbial communities found on the surface of coral play a role in coral holobiont defense, possibly through production of antimicrobial substances. Selected microorganisms isolated from the mucus layer of a number of coral species were grown using agar-plating techniques. Screening for antimicrobial substances was performed using overlay and drop techniques, employing several indicator microorganisms. Between 25% and 70% of cultivable mucus-associated bacteria from scleractinian corals demonstrated bioactivity. Higher percentages of activity were evident in mucus-associated cultivable bacteria from massive and solitary corals, as compared with bacteria from branching or soft corals. Isolates related to the genera Vibrio and Pseudoalteromonas demonstrated high activity against both Gram-positive and Gram-negative bacteria. Gram-positive bacteria (Bacillus, Planomicrobium) demonstrated lower levels of activity, primarily against other Gram-positive bacteria. In some cases, inhibitory effects were confined to the cell fraction, suggesting the involvement of a cell-bound molecule, sensitive to temperature and most likely proteinaceous in nature. These results demonstrate the existence of microorganisms with antimicrobial activity on the coral surface, possibly acting as a first line of defense to protect the coral host against pathogens.

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Section: Methodsmentioning

confidence: 99%

Coral mucus-associated bacteria: a possible first line of defense

Shnit-Orland

Kushmaro

2009

FEMS Microbiology Ecology

311

227

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“…Sensitivity to common commercial antibiotics was tested according to the disk diffusion assay (Awerbuch et al , 1989), using Oxoid antimicrobial susceptibility test disks (Oxoid, Hampshire, UK) containing the following antibiotics: tetracycline, sulfamethoxazole trimethoprim, nalidixic acid, erythromycin, chloramphenicol, methicillin and ampicillin.…”

Section: Methodsmentioning

confidence: 99%

Vibriosp. as a potentially important member of the Black Band Disease (BBD) consortium inFaviasp. corals

Arotsker¹,

Siboni²,

Ben‐Dov³

et al. 2009

FEMS Microbiology Ecology

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Black Band Disease (BBD) is a well-described disease plaguing corals worldwide. It has been established that ecological and environmental stress factors contribute to the appearance and progression of the disease, believed to be caused by a diverse microbial consortium. We have identified and characterized Vibrio sp. associated with BBD in Eilat reef corals using both culture-dependent and -independent methods. Direct sampling using 16S rRNA gene clone libraries showed seasonal dynamics in the diversity of BBD-associated Vibrios. In the two sampling periods, BBD-associated Vibrio clones showed similarities to different groups: October samples were similar to known pathogens, while December samples were similar to general aquatic Vibrio sp. Cultured bacterial isolates of Vibrio sp. were highly homologous (>or=99%) to previously documented BBD-associated bacteria from the Caribbean, Bahamas and Red Seas, and were similar to several known coral pathogens, such as Vibrio coralliilyticus. The proteolytic activity of Vibrio sp., as measured using casein- and azocasein-based assays, directly correlated with temperature elevation and peaked at 26-28 degrees C, with the microorganisms producing more proteases per bacterial cell or increasing the rate of proteolytic activity of the same proteases (potentially metalloproteases). This activity may promote coral tissue necrosis and aid in ensuing progression of the coral BBD.

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“…1958; Awerbuch et al. 1989). The concentration profile of nisin was related to inhibition zone radii using concepts of minimum inhibitory concentration of the antimicrobial (MIC) and critical time of bacterial growth ( T c ) as described by Linton (1958).…”

Section: Introductionmentioning

confidence: 99%

“…Early attempts have been made to theoretically describe the inhibition zone radii using Fick's laws of diffusion (Cooper and Woodman 1946;Cooper et al 1958;Awerbuch et al 1989). The concentration profile of nisin was related to inhibition zone radii using concepts of minimum inhibitory concentration of the antimicrobial (MIC) and critical time of bacterial growth (T c ) as described by Linton (1958).…”

Section: Introductionmentioning

confidence: 99%

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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A numerical method to determine minimal inhibitory concentrations (MICs) of antibiotics directly from disc-diffusion susceptibility tests

Cited by 10 publications

References 7 publications

Coral mucus-associated bacteria: a possible first line of defense

Coral mucus-associated bacteria: a possible first line of defense

Vibriosp. as a potentially important member of the Black Band Disease (BBD) consortium inFaviasp. corals

Modeling development of inhibition zones in an agar diffusion bioassay

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