Agar Diffusion Test

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Agar Diffusion Test

The most commonly used lab test for determining antibiotic susceptibility of bacteria causing clinical disease.


a dried hydrophilic, colloidal substance extracted from various species of red algae. When suspended in a liquid medium and heated to 212°F (100°C), the agar dissolves. When it is allowed to cool to 110°F (43°C) the medium becomes a solid gel. It is used in culture media for bacteria and other microorganisms, in making emulsions, and as a supporting medium for immunodiffusion and immunoelectrophoresis. Because of its bulk it is also used in medicines to promote peristalsis and relieve constipation.

birdseed agar
one containing Guizotia abyssinicia (Niger) seed and creatinine, used for growing Cryptococcus neoformans. Called also Niger agar.
bismuth sulfite agar
a special preparation used for isolation of salmonellae from food.
blood agar
a culture medium used for the growth of bacteria. Consists of agar and intact erythrocytes.
brain heart infusion agar
used for cultivating the yeast phase of dimorphic fungi.
brilliant green agar
used to cultivate salmonellae.
chocolate agar
an enriched agar for the growth of Hemophilus, some Actinobacillus, and Taylorella spp. A molten agar and blood mixture is held at 122°F (50°C) prior to pouring plates. The additional nutrients supplied are hemin and NAD.
agar diffusion test
see antimicrobial sensitivity test.
eosin-methylene blue (EMB) agar
used for the identification of Eschericha coli.
agar gel immunodiffusion test
see immunodiffusion tests.
MacConkey agar
contains bile salts, lactose and neutral red indicator for isolation of enterobacteria.
mannitol salt agar
selective for staphylococci.
milk agar
contains skim milk and used to demonstrate casein digestion.
Niger seed agar
see birdseed agar (above).
nutrient agar
the basic growth medium for bacteria, composed of beef extract and peptone.
potato dextrose agar
used in cultivating fungi; promotes sporulation and pigmentation.
Sabouraud's dextrose agar
one used for isolation of fungi. See also dermatophyte test medium.
agar sausage
see medium sausage.
xylose lysine (XLD) agar
used to differentiate Enterbacteriaceae.
References in periodicals archive ?
In addition, even when resistance marker results are available, some clinicians do not know how to interpret the results, and end up waiting the two to four days for the conventional antibiotic susceptibility test results anyway.
Bacterial Antibiotic susceptibility test results species Amikacin Amoxiclav Sulbactam Ampicillin Pseudomonas S - - - fluorescens Pasteurella - - - - multocida Serratia S S S S spp.
Antibiotic susceptibility test was performed to identify the Methicillin Resistant Staphylococcus aureus (MRSA) from these 23 clinical isolates.
coli antibiotic susceptibility test results Antibiotic Susceptibility Interpretation Amikacin < 16 S Ampicillin > 16 R Cefazolin > 16 R Tobramycin 8 I Trimeth/Sulf > 2/38 R Gentamicin > 8 R Imipenem < 4 S Ceftazidime > 16 R Cefepime < 2 S Levofloxacin > 4 R Cefotetan > 32 R Ciprofloxacin > 2 R Ceftriaxone 32 I Sulbactam/Ampi > 16/8 R Cefuroxime > 16 R Pipercillin/Ta 32 I Table 3.
It would have been more complete if some newer approaches to antibiotic susceptibility test were added.
Antibiotic susceptibility testing: Antibiotic susceptibility test was done for each S.
1) This means it is crucially important that the microbiology laboratory provide physicians with the most accurate antibiotic susceptibility test data possible.
These physicians were interested in a computer program for collecting and monitoring all antibiotic susceptibility test data on isolates from their patients.
Alamar received clearance on the antibiotic susceptibility test kits for the READar in July and August 1993.
Antibiotic susceptibility tests were also determined by using the broth microdilution method according to Clinical and Laboratory Standards Institute guidelines (6).
Common terms regarding antibiotic therapy are prophylaxis (prevention of infection), empiric (directed at a condition), pathogen-directed (organism identified) and susceptibility-guided (when the organism is identified and antibiotic susceptibility tests are completed).
The results of antibiotic susceptibility tests indicated that all nine isolates in the study were resistant to cefotaxime and ciprofloxacin and intermediate or resistant to ceftazidime (Table II).

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