[Use of DNA-DNA hybridization methods for studying the epidemiology and evolutionary similarity of drug resistance determinants]. / Ispol'zovanie metodov DNK-DNK gibridizatsii dlia izucheniia épidemiologii i évoliutsionnogo skhodstva determinantov lekarstvennoi ustoichivosti.

A procedure for rapid mass assay of clinical strains of microorganisms based on DNA-DNA hybridization was developed. Epidemiology of the gentamicin resistance determinant cloned earlier from clinical strains of the same hospital was studied and its plasmid localization in representatives of various genera of Enterobacteriaceae was confirmed. The studies on dot-hybridization showed that in three antibiotic-producing organisms, i.e. S. fradiae 918 producing neomycin, M. purpurea 1535 producing gentamicin and S. rimosus 65 producing oxytetracycline there were DNA sequences homologous to those of the gentamicin resistance determinant cloned from the clinical isolates.

[Biochemical characteristics of the determinants of drug resistance to gentamycin from clinical strains of gram-negative microorganisms]. / Biokhimicheskaia kharakteristika determinantov lekarstvennoi ustoichivosti k gentamitsinu iz klinichekikh shtammov gramotritsatel'nykh mikroorganizmov.

Three to four aminoglycoside inactivating enzymes were detected in cell-free extracts of clinical strains of gram-negative bacteria including Pseudomonas, Escherichia, Serratia, Enterobacter and Klebsiella and in cell-free extracts of their transconjugants. The clinical strains were selected by the feature of gentamicin resistance. All the strains contained AAC(3), APH(3') and APH(3"). In addition to these enzymes 12 out of 25 investigated strains contained AAD(2"). The biochemical characteristics of the gentamicin resistance determinant cloned from the clinical strains on the plasmid vector pUC 19 were studied. By the size of the insertion element pAA4 was the smallest among the constructed hybrid plasmids determining gentamicin resistance. It was shown that just this plasmid determined formation of the two gentamicin inactivating enzymes: AAC(3) and AAD(2") in the transformants carrying it.

[Molecular genetic analysis of the determinant of gentamicin resistance in Enterobacter cloned from a clinical strain]. / Molekuliarno-geneticheskii analiz determinanta ustoichivosti k gentamitsinu, klonirovannogo iz klinicheskogo shtamma Enterobacter.

Resistance of clinical strains of Enterobacteriaceae to aminoglycoside antibiotics and in particular to gentamicin was studied. The data on conjugation and plasmid DNA transformation of a clinical strain 10171 of E. cloacae, as well as the data on P1 transduction showed that its gentamicin resistance was due to plasmids. The gentamicin resistance determinant was cloned from the plasmid DNA with the use of the restriction sites of EcoR I, Hind III and Pst I into the vector plasmid pUC 19. Plasmids pAA1, pAA2, pAA3 and pAA4 carrying the gmr determinant were isolated. Their physical maps were constructed. The restriction analysis supplemented by the data on DNA-DNA hybridization was indicative of the identical 2.0 kb sequences in all the plasmids carrying the gmr determinant.

[Genetic and physicochemical analysis of the resistance of Pseudomonas aeruginosa strains to gentamycin and other antibiotics]. / Geneticheskii i fiziko-khimicheskii analiz ustoichivosti k gentamitsinu i drugim antibiotikam klinicheskikh shtammov sinegnoinoi palochki.

The genetic and physicochemical mechanisms of antibiotic resistance were studied in 50 clinical strains of P. aeruginosa resistant to gentamicin. The serotypes and pyocinotypes of the bacteria were determined. The spectra and levels of antibiotic resistance and the plasmid profiles of the strains were estimated. It was shown that 16 multiresistant isolates had identical spectra and levels of antibiotic resistance, belonged to the same serotype and pyocinotype and were characterized by the absence of the extrachromosomal DNA, which indicated the circulation of the same polyresistant strain in hospital. Plasmids with identical molecular weights and antibiotic resistance spectra were detected in 14 strains belonging to different serotypes and pyocinotypes. These plasmids determined synthesis of the same aminoglycoside inactivating enzymes: APH (3') and AAC (3). Epidemiologic distribution of the same high molecular R plasmid among the clinical strains of P. aeruginosa is suggested.

[Analysis of the etiological structure and dynamics of antibiotic resistance in the causative agents of suppurative inflammatory diseases in the patients at a large general hospital]. / Analiz étiologicheskoi struktury i dinamiki antibiotikorezistentnosti vozbuditelei gnoio-vospalitel'nykh zabolevanii u bol'nykh krupnogo mnogoprofil'nogo statsionara.

The structure of the causative agents isolated from patients with pyoinflammatory infections in 1980-1983 was analysed. It was shown that the surgical and urological infections were mainly caused by gram-negative bacteria. The other pyoinflammatory infections were mainly due to gram-positive cocci. A relatively high frequency of the strains of gram-negative bacteria, especially among Pseudomonas spp. and Enterobacter spp., resistant to aminoglycoside antibiotics, such as gentamicin, sisomycin and tobramycin with preserved sensitivity to amikacin and netilmicin in the majority of the strains was shown. Among the beta-lactam antibiotics cephotaxim and cephalotin were most active against gram-negative bacteria and staphylococci, respectively. The majority of the antibiotic resistant strains of gram-negative bacteria had analogous structures and levels of resistance to 7-12 antibiotics which might indicate the occurrence of 1-2 resistance plasmids among the clinical strains.

[Determination of beta-lactamase types of clinical strains of bacteria using a modified microiodometric method]. / Opredelenie tipov beta-laktamaz u klinicheskikh shtammov bakterii s pomoshch'iu modifitsirovannogo mikroiodometricheskogo metoda.

The substrate profiles and sensitivity to dicloxacillin inhibition were studied in the enzymes of the clinical strains of Pseudomonas aeruginosa and the transconjugants of E. coli carrying the plasmids discovered earlier in P. aeruginosa. The study was performed with a modified microiodometric method for determination of the activity of beta-lactamases. According to the M. Richmond classification of beta-lactamases the enzymes detected in P. aeruginosa strains 4529, 5290 and 9902 may correspond to the 5th class, the enzymes of P. aeruginosa strain 8208 to the 2nd class and the beta-lactamases of the E. coli transconjugants to the 3rd class. Two different beta-lactamases were detected in P. aeruginosa strain 10294.