Study of the activity of a new glycopeptide antibiotic eremomycin combined with tobramycin against Staphylococci in vitro

Eremomycin is an original natural antibiotic with glycopeptide structure isolated at the Institute of New Antibiotics, the USSR Academy of Medical Sciences. Activity of eremomycin alone or in combination with tobramycin was studied with using 25 clinical strains of staphylococci. 56 and 88 per cent of the strains were respectively resistant to gentamicin and kanamycin, two aminoglycoside antibiotics. All the staphylococcal strains were sensitive to eremomycin in concentrations of 0.12 to 1 microgram/ml. The MIC of tobramycin for 10 (40 per cent) sensitive strains ranged within 0.25-2 micrograms/ml. For 60 per cent of the strains the MIC was equal to or higher than 16 micrograms/ml. When eremomycin was used in combination with tobramycin the antibacterial effect with respect to 17 strains (68 per cent) increased. In 32 per cent of the strains the effect was synergistic and in 36 per cent of the strains it was additive. Indifference and antagonism were detected with respect to 7 (28 per cent) and 1 (4% per cent) strains respectively. No significant difference was shown in manifestation of the synergistic-additive nature of eremomycin and tobramycin interaction with respect to the tobramycin sensitive and resistant strains.     

Experimental study of antibacterial activity, therapeutic effectiveness and toxic properties of the combination of tobramycin and carbenicillin

Tobramycin combination with carbenicillin was studied experimentally. Tobramycin is a new aminoglycoside antibiotic prepared at the Institute of New Antibiotics, the USSR Academy of Medical Sciences. It was shown that the combination had mainly synergistic action (67 per cent) on clinical strains of Pseudomonas aeruginosa which was confirmed in treatment of experimental sepsis caused by the organism. In acute experiments with albino mice there was observed summation of the general toxic action of the antibiotics used in the combination. The level and nature of the nephrotoxic action of the tobramycin combination with carbenicillin were shown in experiments with rats to be the same as those of the nephrotoxic action of tobramycin used alone. The presence of carbenicillin in the combination did not increase the inhibitory effect of tobramycin on excitement transmission in the neuromuscular synapses.     

Eremomycin--a new antibiotic of the polycyclic glycopeptide group

Eremomycin is a novel antibacterial antibiotic. It was isolated at the Institute of New Antibiotics, the USSR Academy of Medical Sciences from the culture fluid of actinomycete INA-238. By its physico-chemical and biological properties the antibiotic was classified as belonging to the group of polycyclic glycopeptides. Chemical structure of eremomycin was asserted and it was shown to be a new representative of the group close by its structure to vancomycin and differing from it by the carbohydrate composition and structure of tri-phenoxytriaminotricarboxylic acid. By its anti-bacterial spectrum eremomycin was found to be close to ristomycin and vancomycin. Still, its activity was 2-10 times higher. The antibiotic was several times less toxic than vancomycin. Unlike vancomycin and ristomycin, the novel antibiotic induced no tissue necrosis after its intramuscular administration. The chemotherapeutic indices of eremomycin in treatment of staphylococcal and streptococcal sepsis in albino mice exceeded 10 times those of vancomycin. At present eremomycin is under clinical trials.     

Experimental study of histamine-liberating properties of eremomycin

Eremomycin, a new glycopeptide antibiotic showed the same as ristomycin, polymyxins B and M and kanamycin histamine liberating properties. Liberation of endogenic histamine induced destructive lesions on the mucosa of the gastrointestinal tract. The most pronounced lesions were observed after intraperitoneal administration of the antibiotic. When eremomycin was administered intravenously or subcutaneously the affection of the gastrointestinal tract epithelium was less pronounced. After subplantar administration of the antibiotics pad edema in albino rats was observed. The most pronounced edema was after the use of ristomycin and the polymyxins. After the use of eremomycin and kanamycin it was at the average 2 times less pronounced. Preliminary administration of dimedrol decreased intensity of the pad edema induced by the antibiotics.     

Comparative study of the therapeutic effect of the glycopeptide antibiotics eremomycin, vancomycin and ristomycin in a model of antibiotic-associated colitis in golden hamsters]

Experiments with a model of intraperitoneal or intragastric lincomycin-induced fatal colitis indicated that eremomycin, vancomycin and ristomycin administered orally in daily doses of 100, 100 and 200 mg/kg, respectively, for 5 days protected the animals from development of antibiotic-associated colitis (AAC), which was evident from prolongation of their life-span to 10-23 days against 3-9 days in the controls. Eremomycin administered intraperitoneally according to an analogous scheme protected the animals from development of AAC, prevented 45 per cent of the animals from death and prolonged the life-span of the other animals to 15-28 days against 3-9 days in the controls. Vancomycin administered intraperitoneally was somewhat more efficient. Still, unlike eremomycin it had a local irritating effect. The protective effect of ristomycin administered intraperitoneally was much lower than that of vancomycin and eremomycin.     

Preclinical toxicological study of the new antibiotic eremomycin. Chronic toxicity and effect on intrauterine development of rats

Toxicity of eremomycin was studied after its multiple parenteral administration to albino rats, guinea pigs and dogs in doses equivalent by the body surface to the daily doses for humans i. e. 1 and 3 g. The antibiotic was administered for 1 to 6 months. Tolerance of the antibiotic by the dogs after intravenous and intramuscular administration was satisfactory. In some animals there were observed an insignificant increase in the activity of alanine aminotransferase and a rise in the level of urea in blood serum. Pathomorphological examination of the internal organs of the albino rats and dogs showed that in high doses the antibiotic could have a damaging effect on the kidneys and epithelium of the gastrointestinal tract. The level of the damages depended on the dose of the antibiotic and duration of its use. The damages induced by eremomycin were reversible. It had no marked effect on the peripheral blood count, coagulation system and erythrocyte resistance. In the tested doses the antibiotic had no unfavourable effect on the hearing function in the experiments with guinea pigs. Studies with rats revealed that eremomycin had no teratogenic effect. A slightly pronounced embryotoxic action was observed only after using the antibiotic in doses exceeding more than 12 times the approximate therapeutic dose.     

The structure of antibiotic eremomycin B

A new biologically active component, antibiotic eremomycin B, was isolated from the culture liquid of Amycolatopsis orientalis subsp. eremomycini, the producing strain for antibiotic eremomycin. Its structure was established by NMR spectroscopy and mass spectrometry. Eremomycin B was shown to differ from eremomycin by the presence of an N-carboxymethyl substituent in the disaccharide eremosamine fragment.     

In vitro activity of a new glycopeptide antibiotic eremomycin in relation to obligate anaerobic Gram-positive bacteria]

Antibacterial activity of eremomycin, a novel glycopeptide antibiotic, against obligate anaerobic Gram-positive++ bacteria was studied. Eremomycin was shown to inhibit the growth of obligate anaerobic Gram-positive++ cocci and bacteria belonging to Clostridium in rather low concentrations and within narrow ranges of the MIC which was indicative of the antibiotic undoubted advantages. The antibacterial activity of eremomycin was 2 times as high as that of vancomycin and 8 times as high as that of ristomycin with respect to Gram-positive++ anaerobic cocci. Pathogenic strains of Clostridium spp. were 2 to 4 times more sensitive to eremomycin than to vancomycin. A significant property of the novel glycopeptide antibiotic was shown to be its capacity for inhibiting the growth of Gram-positive++ aerobic and obligate anaerobic cocci within the same concentration ranges which might be of importance in monotherapy of mixed aerobic and anaerobic infections.     

The structure of the aglycon of eremomycin--a new antibiotic of the polycyclic glycopeptide group

Eremomycin is shown to be a new representative of the group of polycyclic glycopeptides. By the amino acid composition it is close to vancomycin but by the structure of triphenoxytriaminotricarboxylic acid it differs from vancomycin. Monodechlorovancomycinic acid was detected in eremomycin. On the basis of the data obtained in studies on the amino acid sequence and the molecule functional groups the structural formula of eremomycin aglycon was assigned. It is demonstrated that the chlorine-containing phenylserine fragment of monodechlorovancomycin acid is located in the N-end region of the aglycon peptide chain.     

Action of lincomycin, chymotrypsin and their combinations on the course of experimental staphylococcal infection

The culture of Staphylococcus aureus was administered intraperitoneally in a dose of LD30 to albino mice. The animals of the 1st, 2nd and 3rd groups were treated with lincomycin, chymotripsin and combination of lincomycin with chymotripsin respectively. The animals of the 4th group were used as control and were not subjected to the treatment with the drugs. A part of the animals from every group was killed on the 3rd, 7th, 14th, 21st and subsequent days and their organs were investigated microscopically and bacteriologically. It was found that staphylococci was isolated from the control mice during a 50-day period after inoculation. Complete liberation of the organs from the causative agent within 25 days from the beginning of the experiment was registered in the animals treated with lincomycin. Isolation of the staphylococci was over by the 27th day in the animals treated with chymotrypsin. Liberation of the organs from the causative agent by the 17th day was observed in the albino mice treated with the combination of lincomycin with chymotrypsin. The combined use of lincomycin with chymotrypsin proved to be most effective: no death was registered among the albino mice, the levels of the pathogenicity and antibiotic resistance in the pathogenic staphylococci decreased.     

Experimental study of the antibacterial activity and chemotherapeutic efficacy of the novel glycopeptide eremomycin

The study of antibacterial and chemotherapeutic activity of eremomycin, a novel glycopeptide antibiotic showed that it inhibited the growth of gram positive and acid fast microbes. The antibacterial spectrum of the novel glycopeptide was close to that of ristomycin and vancomycin. However, the in vitro antibacterial activity of eremomycin was 2-10 times higher than that of ristomycin and vancomycin. It also inhibited the growth of oxacillin resistant microbes at concentrations 5.20 times lower than those of vancomycin and ristomycin. By the therapeutic efficacy in albino mice with staphylococcal or streptococcal sepsis eremomycin was 2-4 times as superior as vancomycin and ristomycin and by the chemotherapeutic indices it was more than 10 times as superior.     

Toxicity of tobramycin in single and multiple administrations to laboratory animals]

The LD50 of tobramycin sulphate administered intravenously, intraperitoneally, subcutaneously and orally to albino mice was 77 (73--82), 262 (234--294), 560 (500--627) and greater than 10500 mg/kg respectively. With an increase in the rate of intravenous administration tobramycin toxicity increased. When tobramycin sulphate was administered subcutaneously daily in multiple doses equivalent to the daily therapeutic doses from humans (calculated for the body surface) and in the doses 2--3 times higher than the above therapeutic ones, the function of the kidneys, liver and the Preier's reflex did not significantly change. When the doses were 8--10 times higher than the therapeutic ones, an increase in the urea level in the blood serum, disappearance and a decrease in the Preier's reflex were observed. The impairment of the kidney function was accompanied by degenerative changes in the convoluted tubules of the kidneys, ischemia of the renal glomeruli and appearance of protein secretion in their capsule cavities. The picture of the peripheral blood did not suffer significant changes. The studies on the acute and chronic toxicity of tobramycin sulphate prepared at the Institute of New Antibiotics showed that the drug did not differ from the import tobramycin samples.     

Effectiveness of tobramycin and immunologic preparations in experimental Pseudomonas infection

Certain indices of immunity were studied in mice with burn sepsis due to P. aeruginosa during their treatment with tobramycin (Tb) alone or in combination with immunological drugs. The most significant stimulation of the phagocytic function of peritoneal macrophages was observed when Tb was used in combination with polyvalent corpuscular vaccine of P. aeruginosa. When Tb was used alone or in combination with hyperimmune plasma of P. aeruginosa there was observed close correlation between the phagocytic index and the levels of cyclic adenosine-3',5'-monophosphate in them. Therapy of P. aeruginosa infection with the antibiotic and immunological drugs resulted in much higher levels of agglutinine antibodies in blood serum of the mice than the therapy with Tb alone.     

Acute toxicity and the cumulative properties of carfecillin

Acute toxicity of oral and intraperitoneal carfecillin was studied on different species of laboratory animals, such as albino mice, rats and guinea pigs. The average lethal doses equal to 3040 (2393.7-3860.8) and 1325 (1104.2-1590) mg/kg for oral and intraperitoneal administration respectively allowed the authors to consider the antibiotic as a low toxic substance under conditions of a single administration. Higher toxicity of carfecillin as compared to carbenicillin may be due to production of free phenol on carfecillin hydrolysin in the animal organism. The different laboratory animals of both sexes had almost the same sensitivity to the antibiotic. On repeated administration of carfecillin to the albino mouse stomach (in portions of LD50) no cumulative properties of the antibiotic were observed.     

Effectiveness of a polyvalent corpuscular Pseudomonas aeruginosa vaccine, antibiotics and their combinations in experimental chronic Pseudomonas aeruginosa infection

The data on the development of the experimental model of P. aeruginosa chronic infection in mice, produced by their intraperitoneal inoculation with the infective agent, and on the study of the properties of this model are presented. The model has been used in the experimental study of the preventive action of P. aeruginosa polyvalent corpuscular vaccine. The comparative study, carried out with the use of the proposed model, has been made with a view to evaluating the effectiveness of different methods for the treatment of P. aeruginosa chronic septic infection by means of antibiotics (polymixin B and tobramycin), P. aeruginosa polyvalent corpuscular vaccine and their combination. The combined use of this vaccine with antibiotics (polymixin B or tobramycin) has proved to give the most pronounced curative effect with respect to P. aeruginosa chronic infection.     

Convulsant action of diphenylhydantoin overdose in young rats

Acute toxicity of diphenylhydantoin (DPH) was studied in 241 male albino rats aged 7, 12, 18, 25 and 90 days. Single intraperitoneal dose of DPH (from 200 to 1000 mg/kg) induced only ataxia and loss of righting reflex in 25-day-old and adult rats. In rats aged 18 days or less ataxia of hindlimbs was also marked. In all these age groups generalized convulsions appeared; they were formed by wild running followed by a clonic phase. The dose of DPH necessary for elicitation of seizures was lowest in 7-day-old rats (75 mg/kg) and increased with age up to 200 mg/kg in 18-day-old rats. The 1000 mg/kg dose was lethal for 25- and 12-day-old rats, but not for 7-day-old ones. The uneven development of excitatory and inhibitory action of DPH is suggested.     

Influence of Ivabradine on the Anticonvulsant Action of Four Classical Antiepileptic Drugs Against Maximal Electroshock-Induced Seizures in Mice

Although the role of hyperpolarization-activated cyclic nucleotide-gated (HCN) channels in neuronal excitability and synaptic transmission is still unclear, it is postulated that the HCN channels may be involved in seizure activity. The aim of this study was to assess the effects of ivabradine (an HCN channel inhibitor) on the protective action of four classical antiepileptic drugs (carbamazepine, phenobarbital, phenytoin and valproate) against maximal electroshock-induced seizures in mice. Tonic seizures (maximal electroconvulsions) were evoked in adult male albino Swiss mice by an electric current (sine-wave, 25 mA, 0.2 s stimulus duration) delivered via auricular electrodes. Acute adverse-effect profiles of the combinations of ivabradine with classical antiepileptic drugs were measured in mice along with total brain antiepileptic drug concentrations. Results indicate that ivabradine (10 mg/kg, i.p.) significantly enhanced the anticonvulsant activity of valproate and considerably reduced that of phenytoin in the mouse maximal electroshock-induced seizure model. Ivabradine (10 mg/kg) had no impact on the anticonvulsant potency of carbamazepine and phenobarbital in the maximal electroshock-induced seizure test in mice. Ivabradine (10 mg/kg) significantly diminished total brain concentration of phenytoin and had no effect on total brain valproate concentration in mice. In conclusion, the enhanced anticonvulsant action of valproate by ivabradine in the mouse maximal electroshock-induced seizure model was pharmacodynamic in nature. A special attention is required when combining ivabradine with phenytoin due to a pharmacokinetic interaction and reduction of the anticonvulsant action of phenytoin in mice. The combinations of ivabradine with carbamazepine and phenobarbital were neutral from a preclinical viewpoint.     

Rapid evaluation of the effectiveness of antibacterial drugs in experimental tularemia

Rapid estimation of the protective effect of antibacterial drugs on Fransiella tularensis for not more than 2 days was shown possible in experiments on albino mice infected with tularemia. High efficacy of aminoglycosides (kanamycin, gentamicin, streptomycin, amikacin, netilmicin, tobramycin, sagamycin, ribostamycin and sisomicin), tetracyclines (tetracycline, doxycycline, minocycline and methacycline), rifampicin, phosphomycin and oxolinic acid was determined with the recommended rapid method. Amoxycillin, ampicillin, piperacillin, carbenicillin, erythromycin, levomycetin, cefradine, cefmetazole, cefatrizine, cefoxitin, cefsulodin and bactrim (biseptol) proved to be inefficient against the tularemia causative agent.     

Therapeutic efficacy of Triazavirin, a novel Russian chemotherapeutic, against influenza virus A (H5N1)

Therapeutic activity of Triazavirin against experimental influenza A was studied on albino mice intranazally infected with influenza virus A/Chicken/Kurgan/Russia/02/05 (H5N1) vs. reference drugs (Oseltamivir, Remantadin and Arbidol). The study showed that in a therapeutic dose of 1 mg/kg Triazavirin was efficient in protection of the animals from death. Its protective therapeutic efficacy (36.7+/-1.7%) was close to that of Oseltamivir (50.0+/-0.0%), comparable with that of Remantadin (38.3+/-1.7%) and higher than that of Arbidol (11.7+/-1.7%). During the whole observation period (up to the terminal phase) Triazavirin inhibited the influenza virus A accumulation in the lungs of the infected albino mice by more than 3 lg.     

Evaluation of outcomes of combined specific prophylaxis with the antibiotic resistant immunogenic plague pathogen strain and emergency prophylaxis with aminoglycosides in the experimental plague model in white mice]

It was shown that aminoglycosides (streptomycin, kanamycin, gentamicin, sisomicin, tobramycin, amikacin) prevented manifestation of postvaccine immunity in albino mice immunized by vaccine strain Yersinia pestis EV. Avirulent strain Y. pestis 363 Monr with chromosome resistance to aminoglycosides of the 1st, 2nd and 3rd generations provided manifestation of antiplague immunity when streptomycin, kanamycin, gentamicin and amikacin were administered for prophylaxis. ED50 achieved 1.0-1.2 x 10(3) CFU and in control group (without treatment) 9.3 x 10(2) CFU. Gentamicin and amikacin were highly effective for experimental plague prophylaxis (90-100% animal survival), but inhibited development of postinfective immunity. Protective index (PI) value was 1.1 x 10(2). It was demonstrated that combination of specific prophylaxis (Y. pestis 363 Monr) and emergency prophylaxis with aminoglycosides in albino mice infected with approximately 1000 LD50 of virulent strain Y. pestis 358 (5 hours after infection) was highly effective and provided protective effect against subsequent infection with plague pathogen. Value of PI was 1.1 x 10(5) and practically did not differ from PI (1.7 x 10(5)) in control group (intact mice, immunized with strains EV [symbol: see text] 363 Monr).