[The colicin selection of the S forms of representatives in the Enterobacteriaceae family].

A method based on a lower sensitivity of S forms to colicines, in comparison with R forms, was used for the selection of S forms of bacteria from dissociated cultures of E. coli O.124:K72, S.

[Immobilization of antibiotics on a titanium surface].

Immobilization of antibiotics on the surface of electrolytically oxidated titanium was tried. Transfer of the immobilized ampicillin into hardly soluble calcium ampicillate resulted in providing the coating with antimicrobial activity for 5 days. The quantity of the immobilized antibiotic determined polarographically amounted to 6.

[Study of the inactivation of antibiotics by bacterial colonies].

A procedure of bacteria application to disks from the colonies was used for determining antibiotic inactivation in the disks by the bacteria colonies after the disk direct contact with the colonies. Changes in the antibiotic activity in the disks were registered after incubation at 37 degrees C for 2 hours. It was shown that ampicillin resistant strains of E.