What is ditch plate method?

The ditch-plate method, originally used in assessing bacterial resistance to sulfonamides, offers the following advantages: (1) A number of organisms may be tested on a single plate; (2) three separate antibiotic “ditches” may be included on each plate; (3) direct comparison of the effects of a particular antibiotic on …

What is microbiological assay of antibiotics?

The microbiological assay is based upon a comparison of the inhibition of growth of micro-organisms by measured concentration of the antibiotics to be examined with that produced by known concentrations of a standard preparation of the antibiotic having a known activity.

Why do we use streak plate technique?

Agar streak plates are an essential tool in microbiology. They allow bacteria and fungi to grow on a semi-solid surface to produce discrete colonies. These colonies can be used to help identify the organism, purify the strain free of contaminants, and produce a pure genetic clone.

What is gradient plate technique?

The technique is termed the gradient. plate method and can be performed easily by. anyone who can grow bacterial cultures. The method involves solidification of a. layer of agar medium while the petri dish is.

How are antimicrobial disks placed on a plate?

Using a disk dispenser or sterile forceps, the disks are placed in even array on the plate, at well-spaced intervals from each other. When the disks are in firm contact with the agar, the antimicrobial agents diffuse into the surrounding medium and come in contact with the multiplying organisms. The plates are incubated at 35°C for 18 to 24 hours.

How do you do a disc diffusion test?

The discs are applied with sterile forceps, a sharp needle, or a dispenser onto the surface of the medium, streaked with test strains, and the reading is reported after incubating the plate for 18–24 hours at 37°C aerobically. Disc diffusion tests are of the following types:

How are Agar disks placed on a plate?

The agar medium must be appropriately enriched to support growth of the organism tested. Using a disk dispenser or sterile forceps, the disks are placed in even array on the plate, at well-spaced intervals from each other.

How does the Stokes disc diffusion method work?

The top of each colony is touched with a loop, and the growth is transferred into a tube containing 4 to 5 ml of a suitable broth medium, such as tryptic soy broth. The turbidity of the actively growing broth culture is adjusted with sterile saline or broth to obtain turbidity optically comparable to that of the 0.5 McFarland standard.