Colonial morphology
In microbiology, colonial morphology refers to the visual appearance of
Procedure
When a specimen arrives in the microbiology laboratory, it is inoculated into an
The opacity of a microbial colony can be described as transparent, translucent, or opaque.
Consistency is examined by physically manipulating the colony with a sterile instrument. It is described using terms like brittle, creamy, sticky and dry. Staphylococci are considered to have a creamy consistency,
When certain microorganisms are grown on
The odour of a culture is sometimes considered part of colonial morphology. While intentionally smelling microbial cultures is not advised, some organisms produce distinctive odours that can be detected during routine examination of the culture. Among these are Pseudomonas aeruginosa, which has a grape-like scent; Staphylococcus aureus, which is said to smell like old socks; and Proteus mirabilis, whose scent is alternately described as putrid[1]: 168 or like chocolate cake.[7]: 124
Other distinctive features of colonial morphology include motility and the production of pigments. Pseudomonas aeruginosa produces the pigments
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Staphylococcus aureus: large opaque, round, creamy, white to yellowish colonies displaying beta-hemolysis on blood agar[1]: 167–73
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Streptococcus pyogenes: small translucent colonies displaying beta-hemolysis on blood agar[1]: 167 [8]: 216
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Streptococcus pneumoniae: small colonies with raised edges displaying alpha-hemolysis on blood agar[8]: 223
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Serratia marcescens: red pigmentation: although considered characteristic of the species, only about 10% of specimens produce this pigment[8]: 236
Interpretation
Colonial morphology serves as the first step in the identification of microbial species from clinical samples.
Observation of hemolysis is useful in the presumptive identification of bacteria,
Although automated techniques like
References
- ^ ISBN 978-0-323-48212-7.
- ^ ISBN 978-0-323-22545-8.
- ^ ISBN 978-1-4511-1659-5.
- ISBN 978-1-118-25116-4.
- ^ ISBN 978-1-61731-007-2.
- ISBN 978-93-5270-185-8.
- ISBN 978-1-68367-035-3.
- ^ ISBN 978-0-07-182503-0.
- ISBN 978-0-85404-284-5.
- S2CID 38205341.
- ISBN 978-0-323-27702-0.
- ^ Androulla, Efstratiou; Theresa, Lamagni (10 February 2016). "Epidemiology of Streptococcus pyogenes". Streptococcus pyogenes : Basic Biology to Clinical Manifestations. Oklahoma City, United States: University of Oklahoma Health Sciences Center. Retrieved 6 March 2020.
See also
- Bacterial cellular morphologies—the microscopic appearance of bacterial cells