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The cells of a newly isolated neomycin sensitive and neomycin resistant strains of Pseudomonas aeruginosa contained similar level of catalase activity. The difference spectrum of the cells revealed the presence of cytochrome c-554 and cytochrome b-560-. The presence of both cytochromes in the same molecular ratio in the cells and subcellular fractions indicates that they are tightly bound to the cytoplasmic membrane. The neomycin resistant strain contained five times less cytochromes than the sensitive strain. The lower cytochrome level in the neomycin resistant cells was found to be independent of the presence or absence of neomycin in the medium. The difference spectra of the cells and particulate fractions did not reveal any cytochromes of alpha-type.
Some amino acids, particularly glycine and serine, favour the accumulation in the fermentation broth of three phosphorylated amino sugar compounds that are intermediates in the pathway of neomycin biosynthesis by Streptomyces fradiae 3535. The compounds were separated and purified further by Amberlite IRC-50 (NH(4) (+) form). The intermediates were characterized by physicochemical methods as neomycin B pyrophosphate (C(23)H(48)N(6)O(19)P(2),3H(2)O), neomycin C pyrophosphate (C(23)H(48)N(6)O(19)P(2),3H(2)O) and neomycin C dipyrophosphate complex (C(24)H(66)N(8)O(33)P(4)).
The inhibition of canine renal sodium potassium adenosine triphosphatase (ATPase) by neomycin was examined. Neomycin inhibited ATPase nearly maximally at 0.02 mM. The inhibition was temperature dependent with a decrease in inhibition occurring at temperatures below 21 degrees C, a temperature which corresponded to a change in activation energy of the ATPase as determined by Arrhenius plot. Preincubation of the ATPase with phosphoinositides was found to prevent the inhibition by neomycin. Other phospholipids were not found to prevent the inhibition. These results indicate a possible interaction between neomycin and the phosphoinositides of the ATPase complex.
Neomycin (paromomycin) phosphotransferase was isolated from the mycelium and fermentation broth filtrates of Act. fradiae. The substance was partially purified by means of fractionation with ammonium sulphate followed by gel-filtration through Sefadex G-100. The extracellular and intracellular forms of the enzyme had the same substrate specificity and used only neomycin and paromomycin as substrates. The other aminoglycosides, including kanamycins A and B, lividomycin and ribostamycin were not used. The both forms had the same thermolability. The intracellular form of the enzyme was detected in the mycelium at the early stages of the organism development, while the extracellular form was found in detectable amounts in the culture medium only at the late stages of the actinomycete development. Therefore, the neomycin-producing organism, i.e. Act. fradiae had one enzyme which phosphorilated neomycin and paromomycin and was excreted from the mycellium into the culture medium during the fermentation process.
A chromatographic assay of neomycin sulfate powders on strongly alkaline ion-exchange resin (hydroxide form) is described. D-(+)-alpha,alpha-Trehalose was used as an internal standard. The amount of neomycin B and C in commercial samples was determined with the proposed method, and the results are compared with those obtained by microbiological assay. In addition, minor neomycin components were estimated by TLC and GLC methods.
In two groups of patients submitted to surgery of the colon and/or rectum, treatment to prevent bacterial infections using a combination of 100 mg neomycin and 10,000 U bacitracin every 6 h for 48 h gave the same results as neomycin employed alone at a dosage of 500 mg every 6 h for 48 h. Results confirm the synergism of action between neomycin and bacitracin.
In 132 patients who underwent elective surgery of the colon, the value of bowel preparation with a conventional oral antibiotic preparation of neomycin-erythromycin (N-E) was compared with erythromycin-metronidazole (E-M). Of 125 patients who were available for assessment, 61 received N-E and 64 E-M. The two groups were evenly matched. Two wound infections occurred in patients receiving E-M, neither due to anaerobic bacteria, but seven wound infections developed in patients given N-E (p = 0.057), five of them caused by anaerobic bacteria. Anaerobic bacteria of the colon are the dominant cause of postoperative wound infection in elective surgery of the colon. Adequate antibiotic preparation directed against these bacteria makes the use of neomycin unnecessary.
A cell-free protein-synthesizing system from Streptomyces fradiae was developed by preparing ribosomes and an S-150 fraction with precautions to prevent protease action. Using this system, the ribosomes of this organism were shown to be susceptible to its own product, neomycin.
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