Biomedical subjects
Publications and source records attributed to M A Rozhavin.
Melanin synthetized by Pseudomonas aeruginosa has been found to protect these bacteria from hyper- and hypoxia, as well as from the lethal action of ultraviolet radiation. The author believes that melanin-synthetizing P. aeruginosa strains are more dangerous in hospitals than P. aeruginosa strains incapable of synthesizing this pigment.
The combined effect of ethonium and 5 antibiotics belonging to different groups was studied with 30 clinical strains of P. aeruginosa. A 2--8-fold increase in the activity of kanamycin and tetracycline against some strains was observed. The MIC of carbenicillin, polymycin M and cefotaxime was lowered by 2--6 times and with respect to some strains by 16--32 times. The detergent is recommended to be used in combination with some antibiotics in treatment of infections caused by resistant strains of P. aeruginosa.
The data on the capacity of 50 melanogenic and 50 amelanogenic P. aeruginosa strains to produce hemolysins, gelatinase, caseinase, DNAase, RNAase, lecithinase, elastase, neuraminidase and to form extracellular slime, obtained in the comparative study of these strains in vitro, are presented. Melanogenic P. aeruginosa cultures were found to have a higher lecithinase and neuraminidase activity. The strains incapable of melanogenesis formed slime more frequently. The properties of the strains in respect to other pathogenicity characteristics under study were identical.
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Gentamicin is one of the most effective drugs for treatment of infections caused by Ps. aeruginosa. However, isolation of the strains resistant to the antibiotics was not infrequent. It was shown in the experiments with 40 cultures that the activity of gentamicin against Ps. aeruginosa increased approximately 20 times when it was used in combination with ethonium, a derivative of bis-quaternary ammonium compounds.
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Sensitivity of 80 Pseudomonas aeruginosa cultures forming melanin and 80 cultures synthesizing other pigments to amikacin, gentamicin, kanamycin, carbenicillin, levomycetin, monomycin, 5-NOK, polymyxin M, rifampicin, streptomycin, tetracycline, tobramycin and erythromycin was determined. It was found that the cultures of Ps. aeruginosa synthesizing melanin were less resistant to most of the antibiotics that the other representatives of this species.
The EPR, IR, UV and visible absorption spectra of a melanin-like pigment from P. aeruginosa were studied. By the whole complex of the spectral characteristics the pigment may be classified as belonging to the melanin group. The study of the antibiotic properties of the pigment showed that it did not inhibit the growth of P. aeruginosa and E. coli. Still, it possessed some antistaphylococcal activity.
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The properties of microbial melanines are very diverse. Melanine of P. aeruginosa is little studied. The pigment was isolated from a strain of P. aeruginosa possessing all characteristic properties of the species. Interaction of P. aeruginosa melanine with various antibiotics was determined by the method of serial dilutions in beaf-peptone broth, using Staph. aureus 209 as a test-microbe, which was added to the medium in an amount of 10(6) cells to each tube. It was found that P. aeruginosa melanine differed from DOPA-melanine in a concentration of 1 mg/ml and did not change the activity of penicillin, tetracycline, oleandomycin, kanamycin and gentamicin with respect to Staph. aureus.
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