Mycoplasma – Ureaplasma

Mycoplasmas are the smallest known form of independent living. These are eubacteria that belong to the group Tenericutes (without rigid wall bacteria).

These bacteria are limited only by the cytoplasmic membrane which gives them special properties and makes them share in the bacterial world (Table I).

TABLE I Properties mycoplasma compared to other microorganisms cells
TABLE I Properties mycoplasma compared to other microorganisms cells


For the first time in 1898, and Roux Nocard isolate a germ in a new case of bovine pleuropneumonia. And many other related microorganisms were described under the name of “Pleuro pneumoniae like organisms” (PPLO).

Nowak proposed in 1929 the name of Mycoplasma to group these germs without wall (myces: mushroom – Plasma: shape).

Described in 1937 by Dienes and Edsall, cultivated by Eaton in 1944 on embryonated egg, Mycoplasma pneumoniae was cultured on artificial media by Chanock, Hayflick and Barile in 1961 proving the bacterial nature of this pathogen.

Since 1973, mycoplasmas are grouped in one class, that of Mollicutes (mollis: Soft – cutis: skin) in order Mycoplasmatales, only Mycoplasma, Ureaplasma and Acholeplasma kinds can be isolated in humans.

In animals and plants, other species may also be found: Spiroplasma, Anaeroplasma, Asteroleplasma.

Ureaplasma urealyticum
Ureaplasma urealyticum

Mycoplasmas have long been confused with L-forms of bacteria. These shapes have a wall of residue which ensures their replication but they are devoid of rigidity and their morphological and cultural characteristics they resemble mycoplasmas. However, these forms L kept the genetic and biochemical characteristics of the bacteria from which they derive and reversion to normal bacteria is sometimes possible. By cons it has never been demonstrated relationship between mycoplasma and bacteria fitted wall and their place in the bacterial world is perfectly justified.

Note that Thermoplasma once classified with mycoplasma is a archaebactérie that has a particular habitat: tailings piles of burning coal, seat of a self-combustion, with conditions of extreme cultures (pH 1-4 and 37 to 65 ° C) in the presence of iron sulfide.

TABLE II: classification and main properties of mollicules
TABLE II: classification and main properties of mollicutes


In humans, mycoplasma and ureaplasma can be isolated from genital and respiratory tracts.

Mr. and Mr. oval salivarium are commensal of the oropharyngeal cavity.

By cons, M. pneumoniae is not part of the normal flora and its presence in the airway is always pathological.

M. hominis and U. urealyticum are normal inhabitants of the male and female genital tract and frequency of isolation is directly related to sexual activity.


Mycoplasmas are rarely present in the free state in the body and they attach to host cells, resistant to biological fluids flow into the light of colonized organs.

The attachment is made ​​on receptors, which would, at least in part, of the sialic acid to M. pneumoniae.

Only adherent strains are virulent. They cause for example the cells of the trachea, ciliostasis and desquamation of the epithelium (M pneumoniae).

Among the factors contributing to virulence include:

– Of cellular metabolism end-products: hydrogen peroxide, which acts directly on the membranes: ammonia produced in large amounts by the hydrolysis of urea (Ureaplasma) or arginine (M. hominis), causes cellular alterations. Similarly galactose produced by Mr. mycoides causes bleeding in the animal;

– Toxins Mr neurolyticum produces a neurotoxin; the injection of M. fermentans or its membrane in large quantities to mice produced a table similar to endotoxemia due to Gram-negative bacilli;

– Enzymes: mycoplasma, turns to his advantage cholesterol and other nutrients to the membrane of the host cell, creating a lethal depletion.


A – Mycoplasma pneumoniae:

1. Pulmonary Locations:

M. pneumoniae (Eaton or agent) is responsible conventionally atypical pneumonia in cold agglutinins. M.pneumoniae transmitted by air is rife with small outbreaks during the cold season and classically observed especially in children over five years, adolescent or young adult; but it can cause severe pneumonia in elderly or immunocompromised individuals. These attacks are nothing special and in fact Mr. pneumoniae is responsible for 10% of atypical pneumonia, confirmed radio- logically.

After a relatively long incubation (average 12-14 days up to 35 days), the invasion is progressive and results in fever with chills, headache, arthralgia … while the seed remains localized to the trachea and respects relatively the integrity of the parenchyma. This causes a persistent, dry cough associated with a clinical picture quite poor.Radiography showed significant abnormalities often unilobaires (inhomogeneous opacities, thickening of the hilum …).

Viral superinfection or bacterial are possible. Healing is slow characterized by persistent fatigue, while pulmonary symptoms have disappeared.

2. Complications:

Eruptive skin manifestations (rashes, Stevens-Johnson syndrome …) rare

– ENT manifestations blood (hemolytic anemia), joint, pancreas, heart (pericarditis).

– Neuro-meningeal manifestations (Guillain-Barré syndrome, aseptic meningitis …)

– Septicemia are rare.

The greatest caution is needed in all extra-pulmonary disorders in which the etiological diagnosis is based solely on serology. Indeed the bacterium is isolated only rarely outside the respiratory tree.

Clinical manifestations of infection with M. pneumoniae could be due to an immunological phenomenon awareness of the individual. Particularly antigenic relationship between glycolipids of the cytoplasmic membrane of the bacterium and those brain tissue explain the occurrence of neurological complications in the absence of mycoplasma isolation in CSF.

B – genital mycoplasmas:

Since these are commensal genital tract, it is difficult to ascribe a pathogenic role. Other etiologies (especiallyChlamydia trachomatis) must be removed before attaching an infectious episode to a mycoplasma infection.

However, genital mycoplasmas have been implicated in multiple attacks.

1. In men:

Non-gonococcal urethritis (the presence of ï 104 CFU / ml in the levy would be considered significant)

– Prostatitis, epididymitis.

2. For women:

U. urealyticum and M. hominis were isolated respectively in 60% and 20% of women of childbearing age. Despite the nature of these commensal bacteria, they have been involved in:

– Nonspecific vaginitis,

– Salpingitis (and would then cause of infertility)

– Hares postpartum (with endometritis), during which it is possible to isolate these bacteria in blood cultures. In most cases this is transient bacteremia and these attacks are benign.

In pregnant women, the presence of mycoplasma has been associated with premature abortions, hypotrophy, but without the compelling evidence of their responsibility have been made.

In the newborn, premature or malformations carrier, nerve infections (with the presence of mycoplasma in CSF or brain tissue) and lung have been reported.

U. urealyticum, due to its urease activity was blamed for stones.

In fact it is very difficult to say the pathogenic role of genital mycoplasmas even in isolation during an infectious episode. Indeed, it can still be a contamination of the sample and the bacteria are common in the genital tract, they could superinfect (or coinfecter) an injury due to another pathogen.


A – Body type:

Mycoplasmas are pleomorphic (round shapes, oval, filamentous or rosary, sensitive to physical agents (Osmotic strength, pH, surfactants, temperature) but resistant to freezing.

They are weakly stained with Giemsa and can be observed under phase contrast or electron microscope.

B – Structure:

The genome is small (that. 5 x 108). The cytoplasmic membrane contains cholesterol (except Acholeplasma) which is not metabolized but which allows the bacteria to regulate the fluidity of the membrane, glycolipids (M. genitaliumand M. pneumoniae) and glycoproteins that play a role in adherence to eukaryotic cells.

C – Growth:

Mycoplasmas multiply by binary division without synchronization between genome replication and cell separation: this form filaments which are divided by throttling in coccoid form.

Generation time varies from one hour (genital mycoplasmas) to 6 hours (M. pneumoniae) and more for Mr.genitalium.

On solid medium colonies appear within 48 hours (genital mycoplasmas), 5 days (M. pneumoniae) or 3 weeks (M. genitalium.) Most mycoplasma form egg colonies on the plate (the center of the colony enters agar) but Mr.pneumoniae forms mûriformes colonies. These colonies have a diameter of 100 to 400 microns; U. urealyticum form small colonies in “sea urchin” of 20 to 80 microns in diameter.

D – Metabolism:

Mycoplasmas are facultative anaerobes general. They derive their energy from glucose fermentation (M. pneumoniae, M. ferment) or degradation of arginine ornithine (M. hominis and M. ferment) or urea hydrolysis (U. urealyticum ).

They grow in microaerophilic atmosphere unless Mr. pneumoniae and M. genitalium that require aerobic conditions.In all cases the CO2 promotes growth.

Mycoplasmas require rich media with yeast extract and serum. This brings the cholesterol needed for growth.

There are very few biochemical characteristics to differentiate strains of mycoplasmas: M. pneumoniae reduced the triphényï tetrazolium (TTZ) and produces a hemolysin which acts on the guinea pig erythrocytes. Mycoplasmas are naturally resistant to antibiotics that inhibit peptidoglycan synthesis (B-lactam antibiotics cycloserine …).

E – Antigenic Structure:

According to the antigenic structure, were distinguished within mycoplasma four groups:

Mr. pneumoniae and M. genitalium

– M. ​​hominis, M. salivarium Mr. oval,

– M.fermentans

– U. urealyticum.

Knowledge of the antigenic structure of mycoplasma has three advantages:

– For identification by growth inhibition and metabolic inhibition,

– The prospect of direct diagnostic research antigen directly in pathological products (M pneumoniae.)

For serological tests.

Multiple U serotypes. urealyticum and M. hominis have been described. In M. hominis a common antigen of 102 kDa has been described. Only one serotype of M. pneumoniae is known. This bacterium has glycolipids in its cytoplasmic membrane which are haptens when they are purified. Antibodies against these glycolipids react with similar structures found in plants and in human brain tissue.

TABLE III: Main characters isolated mycoplames species in men (after C. Bébéar et al.)
TABLE III: Main characters isolated mycoplames species in men (after C. Bébéar et al.)

rarely isolated, M. pneumoniae and M. genitalium have haemadsorption properties


A – Direct diagnosis:

1. Samples:

Due to the adhesive properties of these bacteria, collect the maximum of epithelial cells. The samples will be taken during the acute phase of the disease, if possible before any antibiotic therapy,

– Lung infections: morning sputum or better brushing or endobronchial lavage,

– Genital infection: urethral scraping, vaginal swab,

– Other charges: the tissues will not be crushed but lacerated scalpel before seeding. Cerebrospinal fluid and blood will be deposited in a liquid medium. The search for genital mycoplasmas can be made from a urinary sediment.

2. Transport and storage:

The ideal is to conduct an immediate seeding. Without using a transport medium containing penicillin and bovine albumin. Storage at 4 ° C makes it possible to postpone the inoculation of one week.

3. Direct search:

Search germs by immunofluorescence with monoclonal antibodies is under study and development of oligonucleotide probes is ongoing.

4. Crops:

Given the differences between the cultural characters, looking for Mr. pneumoniae and genital mycoplasmas is not made ​​under the same conditions (Table IV).

TABLE IV: cropping, antigenic, pathogenic mycoplasmas for man
TABLE IV: cropping, antigenic, pathogenic mycoplasmas for man
SCHEME 1: isolation frequency of Ureaplasma urealyticum and Mycoplasma hominis in accordance with the number of partners
SCHEME 1: isolation frequency of Ureaplasma urealyticum and Mycoplasma hominis in accordance with the number of partners

If cultural characters of genital mycoplasmas allow species diagnosis to a good approximation, by cons to assert the diagnosis of M. pneumoniae, it will seek additional characters (hemolysis of red blood cells from guinea pigs, reduced TTZ …).

A species diagnosis may be increased accurately by using the growth inhibition by a homologous antiserum.

In practice, the search for genital mycoplasmas is very easy with simple techniques and is now no need to develop other means of diagnosis.

As against the search for Mr. pneumoniae is more random and low sensitivity. In this case, it may be interesting to have means fast and reliable diagnostics for the detection of this pathogen whose frequency is far from negligible. Currently we are moving more towards direct searches in samples by direct immunofluorescence but above probe DNA (the ribosomal RNA hybridizes with M. pneumoniae) and more recently in search of DNA in the samples by polymerase chain reaction ( PCR).

FIGURE 2: Insulation scheme mycoplames human strains (Data Sheet Diagnostics Pasteur)
FIGURE 2: Insulation scheme mycoplames human strains (Data Sheet Diagnostics Pasteur)

B – Indirect diagnosis:

1. Mycoplasma pneumonia:

The isolation of M. pneumoniae is long and giving inconsistent results, the diagnosis of infection is often focused on the results of serology. In extrapulmonary manifestations of infection with M. pneumoniae serology is often the only argument to assert the etiology of the observed damage.

a / Complement fixation reaction:

This is the current technology, it uses the glycolipid antigen. This reaction can be performed on automated microplate.

Antibody persistence after infection is poorly understood, as a single high rate should be interpreted with caution. By cons, seroconverted between samples taken at 2-3 week intervals favors infection with M. pneumoniae.

b / Other techniques:

The antibody research by other techniques is possible, but of little interest in practice.

The metabolic inhibition (inhibition of the reduction of TTZ) is difficult to implement and gives late results.

Other techniques have been proposed (indirect immunofluorescence, haemagglutination, ELISA).

Currently we are moving towards a more specific serology that implements IP adhesion protein, which plays a role in the pathophysiology of the infection. For antibodies against this protein may be by inhibiting the adhesion of M.pneumoniae to sheep red blood cells or by a technique of “dot-ELISA”. there may cross-react with M. genitalium.

c / The research of cold agglutinins:

It is abandoned because it is not specific: these agglutinins are present only in half of infections due to M.pneumoniae and they are also present in viral infections.

2. The genital mycoplasmas:

Serological techniques have been proposed for the detection of specific antibodies against M. hominis and U.urealyticum: metabolic inhibition or ELISA.

The presence of multiple serotypes complicates this research. This is of little interest in benign infections (urethritis) and may only be used for an etiological diagnosis of pelvic inflammatory disease (salpingitis, epididymitis).

But given the high frequency of isolation of these bacteria, serology should be interpreted with caution because the level of immunization of the population is not known.


A – Prevention:

Vaccine trials against Mr. pneumoniae using various fractions were studied and provide partial protection (attenuated germs, formalin …).

Currently hope is provided by the use of the purified PI protein.

B – Curative:

M. pneumoniae is regularly sensitive to tetracyclines and macrolides. By cons, M. hominis is resistant to erythromycin and U. urealyticum lincosamides.

By cons, these two species are sensitive to tetracyclines. Fluoroquinolones are very active. The emergence of resistant strains can make interesting practice of a liquid medium susceptibility (by investigating metabolic inhibition).


Mycoplasma does not have an important place in human pathology. By cons, animal, mycoplasmas have an important pathogenicity resulting in particular by high morbidity in farms.

The presence of mycoplasma in cell culture media is responsible for cytopathic effects and sometimes cell death.This contamination of animal origin (in the isolation cells) or human (aseptic faults) is difficult to remove.

The economic importance and originality of the structure mycoplasma make these bacteria are currently very studied.

They are becoming better known, and it is likely that taxonomy will evolve in the coming years.