Pathogenesis and Mechanism of Infection
The pathogen is transmitted from person to person exclusively via airborne droplets. Notably, the contagiousness of this microorganism is considered relatively low. Mycoplasmal infection is characterized by a high frequency of asymptomatic and mild disease courses.
Mycoplasma pneumoniae exhibits a pronounced tropism for the respiratory system and specifically targets ciliated epithelial cells. The pathological process occurs at different levels:
- Upper respiratory tract: development of pharyngitis or tracheobronchitis.
- Deep respiratory structures: direct development of pneumonia.
The main feature of pathogenesis is a unique mechanism of immune evasion. The adhesion process is accompanied by a specific response from the epithelial cell: invagination (deep infolding) of the host cell membrane occurs. Mycoplasmas literally hide inside the resulting membrane folds. Residing in these natural niches, the bacteria become completely inaccessible to circulating antibodies, the complement system, and other factors of specific and nonspecific immune defense.
Clinical Features and Complications
The disease is characterized by a relatively long incubation period, averaging from one to three weeks. The febrile period can also be prolonged, lasting up to four weeks, which requires careful monitoring of the patient's condition.
Although the infection often follows a mild course, there is always a risk of process generalization (dissemination). With hematogenous spread, the pathogen can penetrate other organs and tissues. Typical complications include involvement of the joints, bone marrow, and meninges. Furthermore, prolonged persistence of the microorganism and its specific interactions with the immune system create a high risk of developing various immunopathological processes in the patient's body.
Microbiological Diagnostics
A comprehensive approach is used to confirm the diagnosis, combining serological, bacteriological, and molecular-genetic methods.
- Serological method. Considered fundamental in clinical practice. It is based on mandatory testing of paired acute and convalescent sera. A strict diagnostic criterion is a 4-fold rise in the titer of specific antibodies. It includes two main reactions:
- Complement fixation test (CFT) — utilizes glycolipid antigens.
- Enzyme-linked immunosorbent assay (ELISA) — utilizes protein antigens.
- Bacteriological method. Test materials include nasopharyngeal swabs, sputum, lavage fluid, and blood serum. Inoculation is initially performed in liquid nutrient media, followed by subculturing on solid media or using specialized biphasic media. Colony growth is evaluated after 2–3 days.
- Rapid diagnostics and confirmation. Direct and rapid antigen detection in specimens is performed using the direct fluorescent antibody (DFA) test. High-precision molecular-genetic methods, such as polymerase chain reaction (PCR) and DNA hybridization, are used for definitive confirmation.
Treatment and Prevention
A key biological feature of Mycoplasma pneumoniae is the complete absence of a cell wall. Therefore, targeted antimicrobial therapy requires careful selection of antibacterial drugs. Medications that target cell wall synthesis are completely ineffective against this infection.
Drugs of choice include antibiotics capable of acting intracellularly or directly blocking microbial protein and DNA synthesis:
- Macrolides
- Tetracyclines
- Fluoroquinolones
Specific prophylaxis (vaccination) has not been developed to date. Nonspecific prevention relies on strict adherence to general sanitary and hygienic measures used to prevent the spread of any respiratory infections.