Mycoplasma Characteristic Features Quiz

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Questions and Answers

Why are mycoplasmas resistant to antibiotics that inhibit cell wall synthesis?

Mycoplasmas lack a cell wall (correct)

Mycoplasmas have a thick cell wall

Mycoplasmas have a rigid cell wall

Mycoplasmas have a flexible cell membrane

What is the characteristic appearance of mycoplasma colonies?

Rough, irregular colonies

Smooth, circular colonies

Tiny, 'fried egg' shaped colonies (correct)

Large, opaque colonies

What is the role of cholesterol in the cell membrane of mycoplasmas?

Cholesterol is required for mycoplasmas to grow on cell-free media

Cholesterol is used as an energy source by mycoplasmas

Cholesterol provides structural rigidity to the cell membrane

Cholesterol helps compensate for the lack of a cell wall in mycoplasmas (correct)

What is the reason for the difficulty in diagnosing mycoplasma infections?

Mycoplasmas are difficult to culture and require prolonged incubation Signup and view all the answers

Which test is considered most diagnostic for mycoplasma infection?

Serology (IgM or a fourfold rise in IgG) Signup and view all the answers

What characteristic feature of mycoplasma contributes to their resistance against antibiotics that inhibit cell wall synthesis?

Lacking a cell wall Signup and view all the answers

What is the significance of a high cold agglutinin titer in the diagnosis of mycoplasma infection?

It indicates a recent mycoplasma infection Signup and view all the answers

Why is direct microscopy of limited value in the diagnosis of Mycoplasma infections?

Mycoplasma lack cell wall and cannot be stained by the Gram stain Signup and view all the answers

What is the unique characteristic of Mycoplasma's cell membrane compared to other bacteria?

It is enveloped by a cell membrane Signup and view all the answers

What do cold agglutinins do in the context of Mycoplasma infections?

Agglutinate RBCs at low temperatures Signup and view all the answers

Which type of antibody response indicates recent Mycoplasma infection?

IgM antibody response Signup and view all the answers

In what way do mycoplasmas differ from other bacteria in terms of growth requirements?

They need serum-enriched medium containing cholesterol Signup and view all the answers

How do mycoplasmas compensate for their lack of a cell wall?

By incorporating sterols like cholesterol into their cell membrane Signup and view all the answers

Why is cultivation of mycoplasmas difficult compared to other bacteria?

They require prolonged incubation periods Signup and view all the answers

How do fastidious bacteria like mycoplasmas appear when observed microscopically after several days of incubation?

As minute colonies with a 'fried-egg' appearance Signup and view all the answers

Study Notes

Mycoplasma Characteristic Features

Lack cell wall, making them resistant to antibiotics that inhibit cell wall synthesis, such as beta-lactams (e.g., penicillin and cephalosporins)
Unstainable by the Gram stain
Variable in shape (pleomorphic)
Contents are enveloped by a cell membrane
Cell membrane contains sterol in the form of cholesterol to compensate for the lack of cell wall
The smallest bacteria that can be grown on cell-free media
Require serum-enriched medium containing cholesterol (fastidious bacteria)
Produce minute colonies with a characteristic “fried-egg” appearance (seen only microscopically) after several days of incubation

Mycoplasma Laboratory Diagnosis

Diagnosis of Mycoplasma infection is based on serology
Direct microscopy is of limited value due to inability to stain with Gram stain
Cultivation is difficult and requires prolonged incubation (up to 3 weeks in case of M.pneumoniae)
PCR is rapid and highly sensitive, but expensive and does not distinguish between colonization and infection

Serological Tests

Specific tests: IgM or a fourfold rise in IgG antibody titre by ELIA is diagnostic
Non-specific test: cold agglutinins (IgM that agglutinate RBCs at 4°C but not 37°C)
A titre of ≥1:128 indicates recent infection

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Description

Test your knowledge on the characteristic features of Mycoplasma, including lack of cell wall, resistance to antibiotics, variable shape, presence of cell membrane, and containing sterol like cholesterol. Learn more about the smallest bacteria that can be grown on cell-free media.