Mycoplasmosis (mycoplasmal infection) - Diagnosis

Clinical diagnosis of M. pneumoniae infectionallows us to assume ARI or pneumonia, and in some cases its possible etiology. Final etiological diagnosis is possible using specific laboratory methods.

Clinical signs of pneumonia of mycoplasmal etiology:

• subacute onset of respiratory syndrome (tracheobronchitis, nasopharyngitis, laryngitis);
• subfebrile body temperature;
• unproductive, painful cough;
• non-purulent nature of sputum;
• scanty auscultatory data;
• extrapulmonary manifestations: cutaneous, joint (arthralgia), hematological, gastroenterological (diarrhea), neurological (headache) and others.

In acute respiratory disease caused by M. pneumoniae, the blood picture is uninformative. In pneumonia, most patients have a normal level of leukocytes, in 10-25% of cases leukocytosis up to 10-20 thousand, leukopenia is possible. In the leukocyte formula, the number of lymphocytes is increased, a band shift is rarely observed.

X-ray examination of the chest organs is of great importance for diagnosis.

In M. pneumoniae pneumonia, both typical pneumonic infiltrations and interstitial changes are possible. The radiographic picture can be quite variable. Bilateral lung damage with increased pulmonary pattern and peribronchial infiltration is often observed. Characteristic features include expansion of the shadows of large vascular trunks and enrichment of the pulmonary pattern with small linear and looped details. Increased pulmonary pattern can be limited or widespread.

Infiltrative changes are varied: spotty, heterogeneous and inhomogeneous, without clear boundaries. They are usually localized in one of the lower lobes, involving one or more segments in the process; focal-confluent infiltration in the projection of several segments or lobes of the lung is possible. With infiltration involving a lobe of the lung, differentiation from pneumococcal pneumonia is difficult. Bilateral lesions, infiltration in the upper lobe, atelectasis, involvement of the pleura in the process both in the form of dry pleurisy and with the appearance of a small effusion, interlobitis are possible.

Mycoplasma pneumonia has a tendency to protracted regression of inflammatory infiltrates. In approximately 20% of patients, radiographic changes persist for about a month.

Sputum smears from patients with pneumonia contain a large number of mononuclear cells and some granulocytes. Some patients have purulent sputum with a large number of polymorphonuclear leukocytes. Mycoplasmas are not detected by microscopy of sputum smears stained by Gram.

In specific laboratory diagnostics of M. pneumoniae infection, it is preferable to use several methods. When interpreting the results, it is necessary to take into account that M. pneumoniae is capable of persistence and its isolation is an ambiguous confirmation of acute infection. It should also be remembered that the antigenic affinity of M. pneumoniae with human tissues can both provoke autoimmune reactions and cause false-positive results in various serological studies.

The cultural method is of little use for diagnosing M. pneumoniae infection, since special media are required to isolate the pathogen (from sputum, pleural fluid, lung tissue, swabs from the back of the throat), and colony growth requires 7-14 days or more.

More significant for diagnostics are methods based on the detection of M. pneumoniae antigens or specific antibodies to them.

RIF allows to detect mycoplasma antigens in smears from the nasopharynx, sputum and other clinical material. M. pneumoniae antigen can also be detected in blood serum using the IFA method. Determination of specific antibodies using RSK, IRIF. ELISA, RIGA. ELISA and/or IRIF are most often used to detect IgM, IgA, IgG antibodies. Of diagnostic value are an increase in IgA and IgG antibody titers by four times or more when studying paired sera and high titers of IgM antibodies. It should be remembered that some tests do not differentiate between M. pneumoniae and M. genitalium.

Determination of the genetic material of the pathogen using the PCR method is currently one of the most common methods for diagnosing mycoplasma infection.

One of the recommended diagnostic schemes for M. pneumoniae infection is the determination of the pathogen DNA by PCR in material from the nasopharynx in combination with the determination of antibodies by ELISA.

The minimum diagnostic examination corresponds to the procedure for examining patients with community-acquired pneumonia, which is carried out on an outpatient and/or inpatient basis. Specific laboratory diagnostics of M. pneumoniae infection is not included in the mandatory list, but it is advisable to carry it out if atypical pneumonia is suspected and the corresponding diagnostic capabilities are available. In the case of acute respiratory infections, it is not mandatory, it is carried out according to clinical and/or epidemiological indications.

Differential diagnostics

No pathognomonic clinical symptoms have been identified that would allow distinguishing acute respiratory disease of mycoplasmal etiology from other ARIs. The etiology can be clarified by specific laboratory tests; it is important for epidemiological investigation, but has no determining value for treatment.

Differential diagnostics between ARI and mycoplasma pneumonia is relevant. Up to 30-40% of mycoplasma pneumonias are assessed as ARI or bronchitis during the first week of illness.

The clinical and radiological picture of community-acquired pneumonia in many cases does not allow us to speak with certainty in favor of the "typical" or "atypical" nature of the process. At the time of choosing antibacterial therapy, the data of specific laboratory studies that allow us to establish the etiology of pneumonia are unavailable in the vast majority of cases. At the same time, given the differences in the choice of antimicrobial therapy for "typical" and "atypical" community-acquired pneumonia, it is necessary to evaluate the available clinical, epidemiological, laboratory and instrumental data to determine the possible nature of the process.

Primary atypical pneumonia, except for M. pneumoniae - pneumonia associated with ornithosis. C. pneumoniae infection. Q fever, legionellosis, tularemia, whooping cough, adenovirus infection, influenza, parainfluenza. respiratory syncytial virus infection. To exclude ornithosis, Q fever, tularemia, the epidemiological history is often informative. In sporadic cases of legionellosis, the radiological and clinical picture may be identical to pneumonia caused by M. pneumoniae, and differential diagnostics can only be carried out using laboratory data.

An infiltrate in the upper lobe of the lung in association with blood-streaked sputum makes it necessary to exclude tuberculosis.

Indications for consultation with other specialists

An indication for consultation with other specialists is the occurrence of extrapulmonary manifestations of M. pneumoniae infection.

Indications for hospitalization

Hospitalization for respiratory mycoplasmosis is not always required. Indications for hospitalization:

• clinical (severe course of the disease, aggravated premorbid background, ineffectiveness of initial antibacterial therapy);
• social (inability to provide adequate care and follow doctor’s orders at home, the desire of the patient and/or his family members);
• epidemiological (people from organized groups, such as barracks).

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