The using of the polymerase chain reaction for the detection of resistance genes in gram-negative bacteria in routine practice in a pediatric hospital.

Objective - assessment of RT-PCR for the detection of carbapenem-resistance genes in gram-negative bacteria. A total, 499 strains of gram-negative microorganisms isolated in two pediatric hospitals in 2019-2020 were studied. Species identification was performed using MALDI-ToF mass-spectrometry (Bruker Daltonics, Germany). Meropenem and imipenem minimal inhibitory concentration (MIC) was determined by E-test method (BioMerieux, France). The presence of acquired carbapenemase genes of IMP, NDM, VIM, KPC, OXA-48, OXA-23, OXA-40, OXA-58-groups was determined by RT-PCR. Klebsiella pneumoniae (34%), Escherichia coli (4%), Serratia marcescens (6%) and other members of Enterobacterales (6%), also gram-negative non-glucose-fermenting bacteria Acinetobacter baumannii (14%), Pseudomonas aeruginosa (36%) were found among selected strains. Carbapenemase production was found in 385 isolates (77%). The main mechanism determining carbapenem resistance in P. aeruginosa was the production of blaVIM (100%). A. baumanii strains harbored OXA-23 (55%) and OXA-40 (45%) carbapenemases. The major determinant of carbapenem resistance in K. pneumoniae isolates was OXA-48 carbapenemase, detected in 63% strains, 13% of the strains possessed blaNDM-group, 16% isolates had a combination of blaNDM-group and blaOXA-48-like. Carbapenemase of KPC-group was found in 8% K. pneumoniae strains. OXA-48 carbapenemase prevailed (95%) among S. marcescens strains. Most of E. coli isolates harbored metallo-beta-lactamase NDM (89%). Other members of Enterobacterales most often had OXA-48 carbapenemase (57%), 39% of the isolates carried blaNDM-group. In one strain, a combination of blaNDM-group and blaOXA-48-like was discovered. RT-PCR is a fast and reliable method for the detection of acquired carbapenemases and can be recommended for routine use in bacteriological laboratories.

[Some features of measles virus morphogenesis in highly differentiated human astrocyte cultures]. / Nekotorye osobennosti morfogeneza virusa kori v kul'turakh vysoko- differentsirovannykh astrotsitov cheloveka.

Astrocyte cultures of adult human brain were used to study the morphogenesis of measles virus at different multiplicity of infection. High-dose (1 to 10 TCD50/ml) inoculation of the culture was found to give rise to an acute infection with cytolysis on days 10-12 postinfection and formation of extracellular mature virions. Low multiplicity of infection (0.01-0.1 TCD50/ml) caused the persistence of virus. During a persistent infection the virus in titers 1.7 to 2.4 lg TCD50/ml was detected as long as up to the 3rd passage. Ultrastructural studies of such cultures revealed some features which were not observed in an acute infection: (1) the diameter of intracytoplasmic RNP increased by 1.5 times vs. that in other cell cultures because of coarse thickening of the envelope; (2) numerous immature virions in which nucleocapsids were completely or partially absent; and (3) uncommonly low number of mature virions. Moreover, alterations in the spatial orientation of cytoskeleton components, such as intermediate and thin (actin) filaments were observed. A conclusion is made that astrocytes as a reservoir for measles virus accumulation serve as the source of immature envelope virus production, which may be one of the possible causes of sclerosing panencephalitis. The causes of disturbances in RNP transport from the site of assembly to cell membrane are discussed.

[Morphological characteristics of the course of HIV infection in laboratory animals]. / Morfologicheskaia kharakteristika techeniia VICh-infektsii u laboratornykh zhivotnykh.

The integrative form of infection was obtained in cotton rats intraperitoneally or retrobulbarly infected with the highly-productive strain Zmb HIV-1. Clinically, it appeared as reduced animal weight gain and high mortality rates in the disease terminal stage. The proviral DNA was detected by the polymerase chain reaction in the genomes of cerebral and splenic cells in most animals. A comprehensive study of the time course of morphological changes within 6 months showed impairments in some CNS cells, giving rise to glial nodules and neurone dystrophy. It should be noted that the most profound changes were observed when the virus had been intraperitoneally injected. It was found that some pathomorphological changes were similar to those seen in human neuro-AIDS. In the spleen, HIV-1 first stimulated an immune response, caused an increase in the extent of white bulb follicles and an active formation of germinative centers, then involution of lymphoid formations took place.