Pneumocystosis
Pneumocystosis is a protozoan disease caused by Pneumocystis carinii, and this infectious organism is one of the most common causes of pneumonia in immunocompromised people.
What are the causes?
The causative agent of the disease is Pneumocystis carina, which is a unicellular microorganism. According to morphological signs and sensitivity to antiprotozoal preparations, it was believed that they belong to the simple types of protozoa.
But gradually they began to discover properties more characteristic of fungi in pneumocysts. Attempts to assign them to fungi or protozoa were met with ambiguity of systematic criteria.
In some respects, they are close to protozoa – in terms of morphology, the presence of meiosis, the presence in the composition of the cell wall of cholesterol, and not of ergosterol, as in fungi, which makes pneumocystis sensitive to antiparasitic preparations and insensitive to the antifungal agent amphotericin B , impossibility of their cultivation in a nutrient medium for fungi.
They are linked by the fact that pneumocysts contain structures similar to fungal ascospores, as well as phytosterols, which animal cells lack.
The metabolism of P. Carinii /synthesis of aromatic amino acids, thymidine, etc./ takes place as in fungi, except in pneumocysts, sporogony is absent, which is characteristic of protozoa.
In 1988, Edman and Stringer, using the methods of molecular genetics, showed that the nucleotide sequence of the pneumocystis transport RNA has a high degree of homology with the nucleotide sequence of the tRNA of the yeast Saccharomycetes serevisiae. .
For comparison – analogous sequences were also studied in different types of protozoa such as toxoplasma, plasmodium, acanthamoeba, etc. Genetically, pneumocystis are closest to fungi. But they have a number of characteristics that bring them closer to protozoa.
Because the mitochondrial DNA of P. Carinii contains dehydrogenase and cytochrome oxidase genes that are 60% similar to fungal genes and only 20% similar to protozoan genes. Analogous properties were found in other types of fungi.
According to the latest data, pneumocystis belong to the higher species of fungi. And P. Carinii is an extracellular parasite with a tropism towards lung tissue, that is, it mainly parasitizes in the lungs.
What are the symptoms?
In children, it usually develops in the 4th-6th month of life, mainly among premature, sick with rickets, hypotrophy, affected nervous system, and among older age groups most often in hemoblastosis, malignant neoplasms, AIDS.
The disease begins gradually, the normal growth of the body ceases, the child becomes pale and cyanosis of his labial triangle appears. The normal temperature at the beginning is replaced by subfebrile with a rise to febrile.
Sometimes the disease in children occurs under the guise of acute laryngitis, obstructive bronchitis or bronchiolitis. In rare cases, a fatal outcome occurs with a clinical picture with a pronounced edema of the lungs.
In adults, protozoan infection develops in people who are undergoing immunosuppressive therapy – usually corticosteroids and in people with AIDS.
In the case of medical immunosuppression, the disease often occurs against the background of a reduced dose of corticosteroids.
Treatment of pneumocystosis
The main drugs for the treatment of pneumocystis pneumonia are trimethoprim and sulfamethoxazole /bactrim and biseptol/ and peptamidine isothionate.
It has been established that combining bactrim and peptamide does not increase the effectiveness of the therapy, but only the toxicity of the latter.
Replacing one preparation with another leads, if one of them does not cause significant positive dynamics, clinical manifestations occur in manifestations within 5-7 days.
