Introduction: Staphylococcal infections rank high among healthcare-associated infections. Coagulase-negative staphylococci, especially S. epidermidis and S. haemolyticus, often induce inflammatory processes in newborns. In this regard, it is important to study the persistence of these microorganisms in pediatric hospitals using intraspecific differentiation based on the comparison of spectra of their extracellular proteins. Our objective was to study circulation of S. epidermidis and S. haemolyticus strains in a children’s hospital by electrophoretyping of their extracellular proteins. Materials and methods: We studied 277 strains of S. haemolyticus and 267 strains of S. epidermidis isolated from patients and various objects of the hospital environment by obtaining extracellular proteins of the isolates, analyzing them using polyacrylamide gel electrophoresis, and determining their antibiotic resistance and ability to form biofilms. Results: The analysis of electrophoregrams of extracellular proteins of staphylococci revealed groups of identical strains. Isolates from different patients were combined into 21 S. haemolyticus groups comprising of 69 strains and 13 groups of S. epidermidis comprising of 38 strains. All the cultures were methicillin-resistant, with the exception of one group of two S. haemolyticus strains. More than half of the cultures grouped by spectra of extracellular proteins were multidrug resistant. The absolute majority of S. haemolyticus strains (97.2 %) and three quarters of S. epidermidis strains (76.0 %) were able to form biofilms. The average values of the degree of film formation in S. haemolyticus strains were significantly higher than those in S. epidermidis. Conclusions: Of all the studied cultures of staphylococci, 25 % of strains and 14 % of S. epidermidis strains persisted and were endemic in the children’s hospital, including 88.4 % of hemolytic and 42.1 % of epidermal staphylococcus strains for more than a month, and 21.7 % of S. haemolyticus and 21.1 % of S. epidermidis strains for almost a year. The strains were resistant to methicillin, and the isolates of S. haemolyticus had a high ability to form biofilms.

Objective. To determine frequency of Staphylococcus isolation and antimicrobial resistance in hospitalized children with different types of infections. Materials and Methods. Species identification and antimicrobial susceptibility testing in staphylococci were performed on a WalkAway 96 analyzer using Pos Combo type 20 tablets, and mecA gene detection was performed on a RotorGene 6000 amplifier with a set of AmpliSens MRSA-screen FL. Results. A total of 876 strains of staphylococci isolated in children’s hospitals were tested. The species and antibiotic resistance of Staphylococcus aureus and coagulase-negative staphylococci were studied. The most common types of staphylococci were: S. aureus – 36.0%, S. epidermidis – 23.0%, S. haemolyticus – 19.7%, S. hominis – 14.0%. As many as 35.3% of isolates were methicillin-resistant, while 32.9% of methicillin-resistant S. aureus was detected, and 65.6% of methicillin-resistant strains were among the most frequently isolated coagulase-negative staphylococci. The mecA gene was detected in 97.1% of phenotypically methicillin-resistant strains. Antibiotic resistance of S. aureus and coagulase-negative staphylococci circulating in children’s hospitals is very high. Two strains of S. aureus with intermediate resistance to vancomycin (MIC = 4 mcg/ml) and one S. aureus with resistance to linezolid (MIC = 8 mcg/ ml) were isolated. Among coagulase-negative staphylococci, two strains with intermediate resistance to vancomycin (MIC = 8 mcg/ml), two resistant to vancomycin (MIC = 16 mcg/ml), and 6 strains resistant to linezolid (MIC from 8 to 32 mcg/ml) were identified. Conclusions. Antimicrobial resistance of staphylococci in children’s hospitals does not depend on the species, more than half of the isolated isolates are methicillin-resistant. During the reporting period, staphylococci resistant to vancomycin and linezolid were identified, which requires resistance mechanisms to be determined.

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Introduction: A large number of infectious processes are associated with opportunistic microorganisms. The phenotype of antibiotic resistance of such pathogens is multidrug-resistant strains with the presence of various β-lactamases. Our objective was to determine the phenotypic and genotypic features of antibiotic resistance of staphylococci, enterobacteria, and non-fermenting Gram-negative bacteria – the cause of infectious diseases in patients of various health facilities of Nizhny Novgorod. Material and methods: Using classical microbiological methods and molecular genetic studies, we analyzed 486 strains of microorganisms isolated from the upper respiratory tract, intestines, urine, and wound discharge of patients in 2019–2020. In all isolates, the phenotype of antibiotic resistance was determined by the disco-diffusion method (Bioanalyse, Turkey) and using the Multiscan FC spectrophotometer (ThermoScientific, Finland) with Microlatest tablets (PLIVA-Lachema, Czech Republic), along with molecular features of resistance mechanisms by PCR on the CFX96 device (BioRad, USA) using AmpliSens kits (Russia). Results and discussion: The results showed that the most prevalent causative agents of infectious diseases (40.7 %) were Gram-negative bacteria, of which Enterobacteriaceae and non-fermenting bacteria accounted for 27.1 % and 13.6 % of cases, respectively. Staphylococci were isolated in 37.6 % of patients: S. aureus and coagulase-negative staphylococci induced 13.4 % and 24.2 % of cases, respectively. The analysis of antibiotic resistance of the isolates showed a high level of antimicrobial resistance in all hospitals, regardless of the isolation locus. The phenotype of methicillin-resistant strains was found in 26.3 % and 37.9 % of S. aureus and coagulase-negative staphylococci, respectively; the mecA gene was found in 89.0 % of methicillin-resistant staphylococci. The highest number of antibiotic-resistant strains among Gram-negative microorganisms was observed in K. pneumoniae, A. baumannii, and P. aeruginosa. We established that 61.7 % of K. pneumoniae, 75.1 % of A. baumannii, and 58.2 % of P. aeruginosa were resistant to carbapenems. The results of molecular genetic studies confirmed the presence of serine carbapenemases KPC and OXA groups in all multidrug-resistant K. pneumoniae and A. baumannii; genes of the metallo-β-lactamase of VIM group were found in 40.9 % strains of P. aeruginosa. The production of numerous β-lactamases and the presence of determinants of antibiotic resistance in the genome determine the virulent properties of opportunistic microorganisms. Conclusion: The antibiotic resistance of opportunistic microorganisms is the cause of developing a chronic infectious process. Today, a wide spread of antibiotic-resistant infectious agents is a serious public health problem, which determines the need for constant microbiological monitoring and studies of molecular mechanisms of resistance to identify the most potent antibiotics and to determine the ways of eradication of multidrug-resistant strains.

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