The article presents the results of microbiological studies of water from Lake Baikal in the spring period, and identifies a wide range of microorganisms that are tested for pathogenicity. It was established that many microorganisms of the enterobacteriaceae were pathogenic for laboratory animals. In 100 % of cases, pathogenic, sporogenous, anaerobic microorganisms were isolated - Cl. perfringens that multiply without access to oxygen, so, in the water mass.

The relevance of the ecological problem of the mass death of the Baikal seal (Pusa sibirica Gm.) forces researchers to establish causes of this phenomenon. The article presents the results of microbiological studies of swabs isolated from the nasal, oral cavities and rectum. The taxonomic characteristics of microorganisms and their virulence were studied. 14 Baikal seals found in the nerpinaria of Listvyanka were tudied. It was established that in the seal there are the following microorganisms: Clostridium perfringens, Escherichia coli, Enterococcus faecalis, Staphylococcus warneri, Pseudomona aeruginosa, Staphylococcus epidermidis, Staphylococcus aureus, Proteus hauseri, Proteus vulgaris bellisella, Proteus migarisella, rabitemorganii, Psychrobactersanguinis, Enterobacter cloacae. When studying the virulence of microorganisms, it was found that 58% of the strains do not cause the death of laboratory animals, they are mainly the representatives of opportunistic microflora. 42% of the strain were pathogenic, of which two strains of Plesi omonas shigelloides and 42 strains of Clostridium perfringens were identified.

The results of microbiological studies of the material taken from the diseased seal are presented. The taxonomic characteristics of microorganisms, their virulence and antibiotic resistance were studied. Treatment measures were developed and performed. It was found that the seal has the following types of microorganisms: Staphylococcus aureus; Enterococcus faecalis; Escherichia coli; Staphylococcus warneri; Proteus vulgaris; Clostridium perfringens, Proteushauseri, Staphylococcus epidermidis, Plesiomonas shigel-loides. All pathogens isolated from the seals were sensitive to 60.3% of antibiotics (ampicillin, cefuroxime, cefixime, gentamicin, amikacin, ciprofloxacin, ofloxacin, furadonin, Ceftriaxone, vancomycin) and resistant to 39.7% of antibiotics, two representatives of cephalosporins (cefaclor and ceftazidim) and ticarcillin.

The article presents the results of microbiological studies of the material taken from the seals’ corpses. The authors studied the taxonomic characteristics of microorganisms, their virulence and antibiotic resistance. It has been established that the following types of microorganisms are found in the seal: Citrobacter braakii, S. warneri, S. aureus, Escherichia coli serotypes O2, O18 and O39, Lactobacillus sakei, Aguamicrobium lusatiense. All pathogens isolated from the gastrointestinal tract were sensitive to 52.6% of antibiotics (ampicillin, cefuroxime, cefixime, gentamicin, amikacin, ciprofloxacin, ofloxacin, furadonin, Ceftriaxone) and resistant to 15.8% of antibiotics, two representatives of cephalosporins (cefaclor and ceftazidim) and ticarcillin. Conditionally pathogenic enterobacteria (Citrobacter braakii and Escherichia coli) isolated from muscles and liver were sensitive to all antibiotics.

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