Mycoplasma

Ureaplasma urealyticum has been associated with nongonococcal urethritis (NGU) as well as infertility.

Mycoplasma pneumoniae is the etiologic agent of primary atypical pneumonia. M. hominis, although isolated from up to 30% of patients with NGU, has yet to be implicated as a cause of that disease.

M. fermentans has on rare occasions been isolated from the oropharynx and genital tract. M. mycoides causes bovine pleuropneumonia. 

Ans. is ‘b’ i.e., They are obligate intr acellular organisms 

Morphology

.  Smallest free living organism, are prokaryotes

.  Lack cell wall, are bounded by a triple layered unit membrane that contains sterol (therefore mycoplasmas require sterol for growth).

. Their lack of cell wall is associated with cellular pleomorphism and resistance to cell wall – active antimicrobial agents, such as penicillins and cephalosporins – lactam drugs).

. Multiplication is by binary fission.

.  Non sporing

. Do not posses flagella or fimbria.

. Mycoplasma can be cultivated in fluid or solid media (cell free media).

Biochemical reactions

. Mycoplasmas are chemo-organotrophs, the metabolism being mainly fermentative.

. Most species utilize glucose or arginine as the major source of energy.

. Urea is not hydrolyzed, except by ureoplasmas.

. Unique among prokaryotes is the requirment of most mycoplasmas for cholesterol and related sterols.

.  Mycoplasmas lack the ability to synthesize purine and pyrimidines.

Ans. is ‘a’ i.e., They are L forms 

Features of mvcoplasma

.   Mycoplasmas are unique organisms because they have a very small size similar to viruses but unlike viruses, they have an independent existence i.e. they can grow in cell free media.

• Though they can grow in cell free media but they have a limited biosynthetic ability to they need a rich growth medium containing natural animal protein (usually blood serum) and in most cases a sterol component.

.  The sterol component is required because mycoplasma contains sterol in their cell membrane.

.  Mycoplasmas are also unique because they do not have a regular cell wall instead they are bound by a cell membrane consisting primarily of sterol.

• The absence of the cell wall gives two characteristic properties to mycoplasma –

i)         The absence of cell wall makes them highly pleomorphic.

ii)      Mycoplasmas are completely resistant to penicillin because, they lack the cell wall structure at which penicillin acts instead they are inhibited by tetracycline or erythromycin.

Mycoplasma and L forms of bacteria (cell wall defective bacteria)

• L phase bacteria are cell wall defective bacteria that can replicate serially as non rigid cells and can produce colonies on solid media.

.    L forms develop when many bacteria either spontaneously or induced by certain cell wall inhibiting drugs lose part or all of their cell wall and develop into L forms.

• Some L phase variants are stable, others are unstable and revert to their bacterial parental forms.
• It has been suggested that mycoplasmas may represent stable L forms of bacteria but genetic, antigenic and biochemical evidence are against the possibility.

.  The characteristic of the cell wall defective forms may be similar to those of mycoplasma but by definition, mycoplasmas do not revert to parental bacterial forms or originate from them. There is no genetic relationship  between mvcoplasmas and cell wall defective microbial forms or their parent bacteria.

About option `d’

Mycoplasma and ureoplasma ureolyticum do not produce turbidity in liquid medum. — http://www.springerlink.com

Ans. is ‘b i.e., Are sensitive to beta lactam drugs 

Ans. C. i.e., Require cholesterol for growth 

• Mycoplasma are the smallest free-living organism, are prokaryotes.
• Lack of cell wall is bounded by a triple-layered unit membrane that contains sterol (require sterol for growth).

Ans. is ‘c’ i.e., Can not be cultured from sputum 

. Laboratory diagnosis of mycoplasmal primary atypical pneumonia may be established either by isolation of the mycoplasma or by serological methods.

. Mycoplasma can be cultured in fluid or solid media. A widely used isolation medium is PPLO broth.

.  Specimens are :

1. Throat swabs                        3. Inflammatory exudates
2. Sputum                                 4. Respiratory secretions

Treatment of Mycoplasma pneumonia

About other options

. In a patient with a compatible clinical picture, a cold agglutinin titre of 1 : 32 supports the diagnosis of mycoplasma pneumonia.

.    Cold agglutinins are nonspecific but develop within the first 7 to 10 days.

.   The test can also be performed at the bedside.

.     ESR, may be raised in 50% of the patients.

Ans. is ‘b’ i.e., Salpingitis 

Ans. is ‘b’ i.e., Viral pneumonia

Answer is D (Erythromycin):

Answer is C (Cefotaxime is the drug of choice):

The drugs of choice Jim mycoplasina are Erythromycin and Doxycycline and not Cefotaxime.

Ans. B: Giemsa stain

Mycoplasma are gram negative but are better stained by Giemsa stain Mycoplasma

• Genus of bacteria that lack a cell wall.
• Without a cell wall, they are unaffected by many common antibiotics such as penicillin or other beta-lactam antibiotics that target cell wall synthesis.
• M. pneumonine, which is an important cause of atypical pneumonia
• Mycoplasma is by definition restricted to vertebrate hosts.
• Cholesterol is required for the growth of species of the genus Mycoplasma.
• Their optimum growth temperature is often the temperature of their host if warmbodied (e. g. 37° C in humans) or ambient temperature if the host is unable to regulate its own internal temperature.
• Mycoplasmas are unusual among bacteria in that most require sterols for the stability of their cytoplasmic membrane.
• Sterols are acquired from the environment, usually as cholesterol from the animal host.
• Mycoplasmas generally possess a relatively small genome of 0.58-1.38 megabases
• Additionally they use an alternate genetic code where the codon UGA is encoding for the amino acid tryptophan instead of the usual opal stop codon.
• They have a low GC-content (23-40 mol %).
• Mycoplasma cells are physically small – less than 1          – and they are therefore difficult to detect with a conventional microscope.
• Mycoplasmas are Gram negative but are better stained by Giemsa stain
• Colonies are typically biphasic, with a fried egg appearance
• Detection techniques include DNA Probe, enzyme immunoassays, PCR, plating on sensitive agar and staining with a DNA stain

Ans. is ‘c’ i.e., Dienes method

• Colonies of mycoplasma may be seen with a hand lens but are best studied after staining by Dienes method.
• For this, a block of agar containing the colony is cut and placed on a slide.
• It is covered with a cover slip on which an alcoholic solution of methylene blue and azure has been dried

Ans. is ‘b’ i.e., M. hominis