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Sometimes multiple samples may be taken if the source of an infection is not clear. [1] These samples are transferred to the microbiology laboratory where they are added to culture media, in or on which the bacteria grow until they are present in sufficient quantities for identification and sensitivity testing to be carried out. [35] [28]
Variety of microbiological samples. A laboratory specimen is sometimes a biological specimen of a medical patient's tissue, fluids, or other samples used for laboratory analysis to assist in differential diagnosis or staging of a disease process. These specimens are often the most reliable method of diagnosis, depending on the ailment.
Etest is a quantitative technique for determining the MIC of microoganisms. It is used for a range of Gram-negative and Gram-positive bacteria such as Pseudomonas, [2] [3] Staphylococcus, [4] and Enterococcus species, [5] as well as fastidious bacteria, such as Neisseria and Streptococcus pneumoniae. [1]
The catalase test tests whether a microbe produces the enzyme catalase, which catalyzes the breakdown of hydrogen peroxide. Smearing a colony sample onto a glass slide and adding a solution of hydrogen peroxide (3% H 2 O 2) will indicate whether the enzyme is present or not. Bubbling is a positive test while nothing happening is a negative result.
Colonial morphology serves as the first step in the identification of microbial species from clinical samples. [10] Based on the visual appearance of the colonies, microbiologists can narrow down the list of possible organisms, allowing them to select appropriate tests to provide a definitive diagnosis.
A test for lipase using polysorbate 80 (polyoxyethylene sorbitan monooleate, a detergent). Certain mycobacteria possess a lipase that splits it into oleic acid and polyoxyethylated sorbitol . The test solution also contains phenol red , which is stabilised by the polysorbate 80; when the latter 80 is hydrolysed, the phenol red changes from ...
To perform the OF-glucose test, two tubes of OF-glucose medium are inoculated with the test organism. A layer of mineral oil is added to the top of the deep in one of the tubes to create anaerobic conditions. Oil is not added to the other tube to allow for aerobic conditions. The tubes are then incubated for 24–48 hours.
A microbiological culture, or microbial culture, is a method of multiplying microbial organisms by letting them reproduce in predetermined culture medium under controlled laboratory conditions. Microbial cultures are foundational and basic diagnostic methods used as research tools in molecular biology .