MYCOPLASMA PNEUMONIAE INFECTION

Mycoplasma pneumoniae infection is an acute respiratory disease characterized by the polymorphism of the clinical manifestations, frequent lung affection.

Historic reference

In 1944 M. D. Eaton and his co-authors isolated a filtrating agent form the patients with pneumonia, it caused pneumonia in cotton rats and could be neutralized with the serum of the recovered patients. The pathogen was called Eaton factor after the name of the author. It was considered to be a virus till 1962. when in 1962 R. Chanock and his co-authors proved that Eaton factor belonged to Mycoplasmiaceae and in 1963 this factor was named Mycoplasma pneumoniae after the proposal of the same authors.

Etiology

The mycoplasma is noted for extreme polymorphism because of the absence of the cell wall. Their cell consists.of three morphological elements: an elementary membrane, ribosome and nucleoid, which is represented by DNA - like filaments. The problem of the mycoplasma pneumonia replication is still open.

Mycoplasma can be destroyed by the ultrasound, alternating freezing and defrosting in the distilled water, warming up at a temperature of 40 °Ñ and higher. There is a considerable amount of liquid, solid and semisolid mediums, which can be used for mycoplasma cultivation. The temperature optimum is 37 °Ñ. The appearance of the colony on the agar medium is very typical: the center or the whole colony is situated below the surface of the agar.

Epidemiology

The characteristic peculiarities of the epidemiology of the mycoplasma pneumoniae infection are that it is airborne, and that it is spread widely and everywhere. It usually causes local outbreaks in the organized groups of children and adults and a whole spectrum of diseases develops from the latent infection and the diseases of the upper parts of the respiratory tract to bronchopneumonia which is sometimes accompanied by pleuritis. The ability of the infected organism to spread the infection for a long time is proved, as the pathogen remains for a long time in the respiratory tract of the patients even in case of the clinically effective antibiotic therapy. Mycoplasma pneumoniae infection is registered all the year round, the distinct seasonally has not been ascertained.

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Pathogenesis

The study of the mycoplasma pneumoniae infection pathogenesis was mainly done under the conditions of the experimental modeling in the experiments on the volunteers. The intranasal infection showed the possibility of the development of the pathological changes, which are characteristic of the natural infection, and the formation of the specific antibodies. Pneumonia, laryngitis, an acute respiratory disease, accompanied with fever developed in the volunteers on the 5-13th day after the infection.

Anatomic pathology

The peculiarity of the experimental mycoplasma pneumoniae infection is the development of the moderate inflammatory reaction in the lung tissue and appearance of the growing productive-infiltrative reaction with the formation of the peribronchial, perivascular and interstitial lymphoid-monocyte infiltration. Which is an evidence of the specific immunomorphologic rebuilding in the lungs.

Clinical manifestations

Mycoplasma pneumoniae infection is distinguished by the polymorphism of the clinical manifestations. Mainly causing the diseases of the respiratory organs mycoplasma can cause the affection of other organs or systems. Most often mycoplasma pneumoniae infection causes pneumonia. However, it plays an important role in the affection of the upper respiratory tract, which takes a course of an acute respiratory disease. In case of an acute respiratory disease, after the incubation period of 3-11 days, there is often a gradual onset with the temperature increase up to the subfebrilc values, the development of indisposition, malaise, aches in the body headaches. In one-two days the temperature increases, the symptoms of intoxication get worse, especially, the headache, in some patients there are symptoms, of meningism with meningeal signs. Along with it an acute onset of the disease is also possible, when the temperature reaches 39-40 °Ñ during the first hours. The fever period lasts 4-6 days but hyperthermia not more than 2-3 days. In some cases after the temperature decrease there is a monotonous subfebrile condition during 10-12 days. There are symptoms of the upper respiratory tract affection from the first days of the disease. The most frequent of them are the dryness and tickle in the throat,stuffed nose and cough.

There is a bright hyperemia in the throat, especially, on the back wall and an enlargement of the follicles. Pharyngitis is usually accompanied by rhinitis. All the patients complain of the labored nasal breathing. It is caused by an edema of the nose mucous membrane, but there is not any expressed rhinorrhea. One of the main symptoms is a dry cough. In most patients it is excruciating, sometimes it reminds the attacks of the whooping-cough, causes vomiting, pain in the chest and in the abdomen. It remains for 6-Þ days but it can last longer. Quite often the symptoms of bronchitis join the mentioned symptoms. The breathing becomes hard, dry rale appear. There are no other physical changes.

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The disorder of the cardiovascular system is not characteristic of this form of mycoplasma pneumoniae infection. The pulse corresponds with the temperature. The picture of the peripheral blood is characterized by the normal amount of leukocytes, often lymphocytosis, ESR is normal or slightly increased.

Mycoplasma pneumonia. The incubation period is longer than that in an acute respiratory disease and lasts from 7 to 28 days. In the majority of the adults the disease develops gradually with the symptoms of an acute respiratory disease: malaise, moderate headache, stuffed nose, dry cough. The chill appears in 3-4 days and the temperature increases up to 39-40 °Ñ. The fever lasts not more than 10-12 days. The acute development of the process is also possible, when the temperature reaches the high points on the first days.

In contrast to bacterial pneumonia there is no severe intoxication. Nausea, vomiting, sleep disorders are very rare. Much more often the patients complain of joint, muscles aches, especially, in the waist. The cough is the permanent symptom, which develops on the first day of the disease and lasts 10-15 days and sometimes longer. In the beginning it is usually dry, exhausting, but by the end of the 2nd week it starts to be productive, but the sputum is discharged with difficulty and in a small amount. On the first days of the disease the symptoms of pneumonia are not observed. The pain in the chest develops in half of the patients on the 5-7 day. As for the physical changes in the lungs, they are either scanty or absent, though, the inflammatory changes are observed during the x-ray examination. In this case shortness of breath, cyanosis are not typical symptoms of the pulmonary (respiratory) insufficiency. However, the changes of the ventilation function of the lungs and the disorder of the bronchial permeability are observed during the spirographic examination.

The x-ray picture of mycoplasma pneumonia is variable. The process can take the segmental focal or interstitial pneumonia course. The infiltrates are most often found in the lower lobe where they capture 1-2 segments. The lobe affections are rare. The foci may not be homogeneous, without distinct borders. Atelectasis and pleural exudate may be the manifestations of the inflammatory process. However, neither of the mentioned manifestations can be a diagnostic

symptom.

The cardiovascular system is not considerably affected. The changes in the function of the alimentary tract are not ascertained. The increase of the lymphocytes is characteristic of the peripheral blood.

Complications

Of all the extrapulmonary manifestations of M. pneumoniae cardiac abnormalities are the most commonly reported. The signs of heart involvement are arrhythmia, congestive failure, chest pain, ECG abnormalities. Among neurologic complications aseptic meningitis, meningoencephalitis, brain stem dysfunction have been reported.

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Diagnosis

An acute respiratory disease caused by the Mycoplasma pneumoniae does not have any specific symptoms, that is why its clinical diagnosis is very difficult. In spite of some peculiarities of the course mycoplasma pneumonia does not have any pathognomonic symptoms, that is why the results of the x-ray and laboratory investigations are conclusive in the diagnosis.

The laboratory diagnosis is based on the method of neutralization of the growth suppression, reaction of the indirect hemagglutination and detection of the mycoplasma pneumoniae infection antigen in the cells of the washouts from the throat with the immunofluorescent method. The skill test with mycoplasma pneumonia allergen can be used starting from the second week.

Differential diagnosis

Diferential diagnosis is complicated. Because the mycoplasma pneumoniae infection does not have any specific symptoms, it should be based both on the data of clinical examination, and on the data of laboratory methods of diagnosis.

Treatment

Tetracycline and erythromycin are the most effective etiotropic treatment. In case of the sole affection of the upper respiratory tract parts the antibiotic treatment is pointless, the symptomatic medications are enough.

In case of severe pneumonia with a tendency to a long course, when enteral and parenteral antibiotic usage is not effective, it is recommended to use them in the form of the ultrasound aerosol with the proteoclastic enzymes. The prognosis is usually favorable, but it can be serious in case of the severe complications, especially, in children.

Prophylaxis

The vaccines did induce specific antibody responses, but protection against infection was limited to more than 50 % of vaccine recipients. Live vaccines using attenuated wild-type and temperatyre sensitive mutant mycoplasma have proven no more effective.

Control questions:

1. Etiology and epidemiology of mycoplasma pneumoniae infection.

2. Pathogenesis of mycoplasma pneumonia.

3. Clinical manifestations of mycoplasma pneumonia.

4. Complications of mycoplasma pneumonia

5. Laboratory methods of diagnosis.

6. Criteria of diagnosis.

7. Differential diagnosis of mycoplasma pneumonia.

8. Treatment of mycoplasma pneumonia.

9. Preventive measures in spot of disease outbreak.

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Date: 2014-12-21; view: 1052