What is a small colony variant?
Small colony variants constitute a slow-growing subpopulation of bacteria with distinctive phenotypic and pathogenic traits.
What causes small colony variants?
Bacterial variants of Staphylococcus aureus called small colony variants (SCVs) originate by mutations in metabolic genes, resulting in emergence of auxotrophic bacterial subpopulations. These variants are not particularly virulent but are able to persist viable inside host cells.
What is the colony morphology of Staphylococcus aureus?
S. aureus – individual colonies on agar are round, convex, and 1-4 mm in diameter with a sharp border. On blood agar plates, colonies of Staphylococcus aureus are frequently surrounded by zones of clear beta-hemolysis.
What is SCV positive?
SCVs form small, colorless, non-hemolytic colonies after 48 h, are only slowly coagulase positive, fail to ferment mannitol, and can revert to the parental phenotype. The phenotype of SCVs is mostly related to alterations in hemin and/or menadione biosynthesis or to thymidine deficiency.
What are small colonies called?
Size – the diameter of the colony. Tiny colonies are referred to as punctiform.
What do E coli colonies look like?
Traditionally, the colony morphology of Escherichia coli is identified as either a rough or a smooth form. The two forms are readily distinguished, as the colonies of the former are rough, flat, and irregular and colonies of the latter are smooth, high, and circular.
Are small colony variants rapidly growing?
Small-colony variants (SCVs) are slow-growing variants of human bacterial pathogens.
Which type of microorganisms live in colonies?
Microorganisms like amoebacan live alone, while fungi and bacteria may live in colonies.
How do I know if I have E. coli colony?
coli colony is off-white or beige in color with a shiny texture. It often looks like mucus or a cloudy film over the whole surface of the plate. An E. coli colony is slightly raised and has an entire, fixed margin and a steady growth pattern, creating concentric growth rings in the colony.
What are the characteristics of small colony variants?
Small colony variants constitute a slow-growing subpopulation of bacteria with distinctive phenotypic and pathogenic traits. Phenotypically, small colony variants have a slow growth rate, atypical colony morphology and unusual biochemical characteristics, making them a challenge for clinical microbiologists to identify.
Can a small colony variant cause an infection?
Clinically, small colony variants are better able to persist in mammalian cells and are less susceptible to antibiotics than their wild-type counterparts, and can cause latent or recurrent infections on emergence from the protective environment of the host cell.
How are small colony variants of Staphylococcus aureus formed?
Bacterial variants of Staphylococcus aureus called small colony variants (SCVs) originate by mutations in metabolic genes, resulting in emergence of auxotrophic bacterial subpopulations. These variants are not particularly virulent but are able to persist viable inside host cells.
How big are the colonies of SCV bacteria?
As their name implies, the most conspicuous feature of SCVs is their colony size — SCVs form colonies that are almost one-tenth the size of colonies associated with wild-type bacteria. In addition, SCVs have fastidious growth requirements and therefore present a challenge to clinical microbiologists.