Enzymatic inactivation of levomycetin and penicillin by cells of the plague and pseudotuberculosis microbes that contain R plasmid depending on cultivation conditions]

The activity of enzymes, inactivating levomycetin and penicillin in the cells of plague and pseudotuberculosis microbes bearing extrachromosomal determinants resistant to a number of antibiotics was studied as dependent on some cultivation parameters: population age, aeration rate and temperature. It was shown that the highest capacity for levomycetin acetylation was characteristic of the cells in the late logarithmic and early stationary growth phages. Accumulation of levomycetin O-acetothers in the incubation medium markedly increased, when the cells were grown under the conditions of intensive aeration. An increase in the cultivation temperature up to 37 degrees C was accompanied by a reliable decrease in the activity of levomycetin acetylase in the transconjugant plague and pseudotuberculosis microbes though no correlation with the resistance levels in the same strains to the above antibiotics was observed. Optimal conditions for penicillinase production were determined. The maximum levels of penicillinase were found in the cells of Y. pestis 556/106 Rn with the episotic resistance type in the early exponential developmental phase under the aeration conditions and the temperature of 28 degrees C.     

Antibiotic sensitivity and the characteristics of transmissive R plasmids in Shigella belonging to various species]

Sensitivity of 241 Shigella strains isolated from patients at various regions of the USSR in 1975--1978 was tested with respect to 14 antibiotics by the method of serial dilutions. 90.5 per cent of the isolates proved to be resistant to the antibacterial drugs and the greater part of 75.9 per cent of them had multiple resistance. The resistance of the Shigella was most pronounced and frequent with respect to tetracycline, streptomycin, levomycetin, as well as ampicillin and carbenicillin. Gentamicin, cephaloridin, polymyxin M, kanamycin, monomycin, neomycin and rifampicin were highly active against the Shigella. More than 50 per cent of the isolates were sensitive to levomycetin, ampicillin and carbenicillin. Differences in the frequency of the resistant strains and the spectrum of the antibiotic resistance of different Shigella subgroups (species) were observed. The study of 173 multiple resistant Shigella strains showed that about 67 per cent of the strains had a capacity for transduction of the resistance markers into the recipient cells of E. coli. The conjugative R-plasmids were most frequent in Sh. boydii and Sh. sonnei (95 and 95 per cent respectively), less frequent in Sh. flexneri and Sh. newcastle (68 and 53 per cent respectively) and least frequent in the mannitol negative Shigella (25 per cent). The capacity for transduction of R-plasmids in the strains carrying the determinants of resistance to 2 or 3 antibiotics was higher than in the strains carrying the determinant of resistance to one antibiotic. The clinical Shigella strains tested mainly had transmissive R-plasmids of fi--character (79 per cent).     

Clinical evaluation of antibiotic therapy of NAG-infection]

It is not concluded yet whether it is expedient to use antibiotic therapy with respect to patients and vibrio-carries with NAG-infection. Observation of a group of patients with acute gastro-intestinal infections caused by NAG-vibrio and carriers of NAG-vibrioes showed that the rate of vibrio isolation after a course of antibiotic therapy (tetracycline, levomycetin) significantly decreased as compared to that in the group of the patients subjected only to symptomatic therapy. The data of the study provided recommendation of antibacterial therapy with respect to patients with NAG-infection especially in cases with accompanying infections or invasions. As for "asymptomic" carriers antibiotic therapy is required only with respect to persons with repeated vibrio isolation.     

The sensitivity to 12 antibiotics of 125 strains of Streptococcus group B isolated in a maternity home

Sensitivity of 125 strains of group B streptococci isolated from newborns, their mothers and personnel in a maternity home was studied with respect to 12 antibiotics: benzylpenicillin, ampicillin, methicillin, cephalotin, erythromycin, lincomycin, levomycetin (chloramphenicol), oxacillin, tetracycline, streptomycin, gentamicin and ristomycin. The method of serial dilutions in a solid medium was applied. All the strains were sensitive to ristomycin and erythromycin. The predominating number of the strains were sensitive to lincomycin, levomycetin and the beta-lactam antibiotics. Strains resistant or moderately resistant to benzylpenicillin, ampicillin, oxacillin, methicillin and cephalotin were detected. The majority of the strains were resistant to streptomycin, tetracycline and gentamicin. Multiple antibiotic resistance with 2-7 determinants was revealed in 11.2 per cent of the strains. The antibiotic sensitivity of the strains isolated from the newborns, their mothers and the personnel in the maternity home was on the whole similar or insignificantly differed.     

Antibiotic resistance and its transmissibility in strains of opportunistic enterobacteria

Sensitivity of 39 opportunistic Enterobacteria strains was studied with respect to tetracycline, kanamycin, ampicillin, levomycetin, streptomycin and nevigramon. The strains were isolated from children with acute intestinal infections of obscure etiology. 38 isolates were resistant to one or more drugs. The highest number of the strains was resistant to kanamycin, ampicillin and levomycetin, i.e. 81.5, 84.2 and 84.2 per cent of the cultures respectively. Nevigramon proved to be the most effective in vitro (76.4 per cent of the sensitive strains). The ability of the strains to transfer the antibiotic resistance markers on conjugation was tested. Transmission of R plasmids was shown in 75 per cent of the isolates.     

Sensitivity to antibacterial preparations of the pathogenic staphylococci isolated from carriers]

After discontinuation of the use of antibiotics for sanation of the carriers of pathogenic staphylococci among the staff of a maternity unit, the number of the strains resistant to penicillin, streptomycin, chlortetracycline, tetracycline, levomycetin, erythromycin, monomycin and neomycin decreased 1.3, 2.9, 10,4.3,5.5,1.5,3.9 and 2.4 times respectively. The differences were statistically reliable. The causes of the antibiotic resistance decrease require further investigation.     

Restoration of radiation resistance in ataxia telangiectasia cells by the introduction of normal human chromosome 11

In order to identify the human chromosome which carries a mutated gene in cells from a patient with the hereditary disorder ataxia telangiectasia belonging to complementation group D (AT-D), we performed chromosome transfer experiments via microcell fusion. A single, pSV2neo-tagged chromosome, either 11 or 12, derived from normal human fibroblasts was introduced into AT-D cells by microcell fusion, and clones which were resistant to the antibiotic G418 were isolated. All 3 hybrid clones containing an additional copy number of chromosome 11 showed a restoration of the resistance of wild-type cells to killing by X-irradiation, whereas all 3 hybrid clones containing an additional copy number of chromosome 12 remained hyper-radiosensitive, like the parental AT cells. The results indicate that a defective gene of AT-D cells is also located on chromosome 11, since a genetic linkage analysis has previously suggested that a defective gene of its complementation group A is located on this chromosome.     

Antibiotic sensitivity of El Tor vibrios isolated from open reservoirs

Sensitivity of 500 El Tor vibrio strains isolated from open water reservoirs was studied with respect to 14 antibiotics. Some of the strains markedly differing from the other isolates by the sensitivity levels and the set of the resistance determinants were subjected to a detailed analysis. The problem of distribution of antibiotic resistant strains of the cholera germ is discussed.     

Antibiotic sensitivity of beta-hemolytic Streptococcus group A on a new nutrient medium for the cultivation of streptococci

Sensitivity of 167 strains of beta-hemolytic streptococci of group A was studied with the method of serial dilutions on a solid agar medium for cultivation of streptococci. The medium was developed at the I. I. Mechnikov Research Institute of Vaccines and Sera. It does not require addition of blood or serum. The strains were found to be highly sensitive to penicillin, cephalothin and erythromycin. The number of the strains resistant to tetracycline, streptomycin, gentamycin, levomycetin (chloramphenicol) and ristomycin amounted to 51, 36, 23, 1.8 and 1.8 per cent, respectively. One of the strains (0.6 per cent) was resistant to lincomycin. Strains with multiple resistance were isolated. The necessity of regular control of distribution of antibiotic resistance among staphylococci is indicated.     

Structure of the microflora of suppurative wounds and its sensitivity to antibiotics]

Clinico-bacteriological examination of patients with purulent infections showed that Staphylococcus was the predominating microflora in the wounds. Simultaneously an increasing role of gram-negative conditionally pathogenic bacteria was shown. Multiple drug resistance was found in the organisms tested. The highest sensitivity levels were observed to gentamicin, kanamycin, tetracycline, levomycetin. It was shown by means of special typing methods that staphylococci of phage group III and Ps. Aeruginosa of serotype II predominated in the infected wounds. When the pathological material contained the antibiotic resistant cultures of Ps. aeruginosa, Proteus, Klebsiella and toxigenic strains of Staphylococcus, a tendency for prolongation of the suppurative process was observed.     

Transposon-induced genetic rearrangements in the chromosome of Vibrio El Tor and their application to the construction of the first genetic map of a cholera vibrio

The specificity of integration of chloramphenicol resistance transposon (Tn9) into Vibrio El Tor chromosome was studied. As shown by the isolation of auxotrophs offerring various nitritional requirements, Tn9 displayed fairly low specificity in its interaction with the chromosome. When inserted into cholera vibrio chromosome, Tn9 induced secondary rearrangements of genetic material. Nutritional requirements were identified for the polyauxotrophic clones which resulted from the mutations in chromosome region adjacent to the insertion sites of Tn9 and Tn10. Based on these observations a preliminary map was constructed for certain regions of V. eltor chromosome.     

Study of the pharmacological properties and safety of a solution of levomycetin in hexamethylene tetramine for intravenous administration]

Pharmacological properties of 2 per cent levomycetin solution in 40 percent hexamethylentetramine solution, as a new pharmaceutical form of levomycetin for intravenous administration prepared at drug-stores were studied. The maximum tolerating doses of the drug for mice, rabbits, and dogs were 26-47 times higher than the therapeutic ones with respect to the content of levomycetin and hexamethylentetramine. No increase in the toxicity of levomycetin and hexamethylentetramine in the preparation was observed. The drug in the doses 16 times higher than the therapeutic ones by the content of levomycetin did not almost change the arterial pressure and the drug in the doses 3.7 times higher than the therapeutic ones did not affect the blood coagulation either in acute experiments, or on its prolong intravenous infusion. Repeated administrations of the drug to rats and rabbits for 15-18 days in doses 3.7-4.8 times higher than the therapeutic ones by the content of levomycetin were innocuous for the animals. Absorption, circulation in the blood, distribution in the tissues and excretion with the urine of levomycetin used in the above pharmaceutical form did not differ from circulation of the antibiotic on its intravenous and oral administration. The drug is recommended for use in medical practice.     

Induction of polymyxin resistance in Pseudomonas fluorescens by phosphate limitation

Shift of Pseudomonas fluorescens NCMB 129 from a phosphate rich into a phosphate limited medium results in a reduction of the membrane phospholipids phosphatidylethanolamine, phosphatidylglycerol and cardiolipin. Concomitantly a positively charged ornithine amide lipid is synthesized. The gradual increase of this lipid is paralleled by an increasing resistance to polymyxin B. The binding capacities of intact cells, and isolated inner and outer membranes for the antibiotic are reduced in the resistant organisms. It is discussed that the observed effect could be circumstantial evidence that the positively charged polymyxin B needs negatively charged receptors in biological membranes in order to exert its antibiotic activity.List of Abbreviations PE phosphatidylethanolamine - PG phosphatidylglycerol - CL cardiolipin - PX polymyxin B     

SOME BIOCHEMICAL PROPERTIES OF CHINESE HAMSTER CELLS SENSITIVE AND RESISTANT TO ACTINOMYCIN D

A graded series of drug-resistant Chinese hamster sublines has been examined for biochemical changes accompanying resistance to actinomycin D. The most highly resistant subline, DC-3F/AD X, is maintained at 10 µg/ml of the antibiotic. It was shown that over 250 times more actinomycin D is required to inhibit RNA synthesis in this subline than in the parental DC-3F line. The DC-3F/AD X subline was also shown to have a somewhat reduced capacity to transport uridine as compared to parental cells. Sensitive cells took up over 50 times more tritiated antibiotic than the most resistant cells, as determined in a 1-h assay. Uptake of actinomycin D was shown to be temperature-dependent in both resistant and sensitive cells and was not influenced by various metabolic inhibitors. Resistance could not be explained by a rapid uptake and release of the antibiotic, as demonstrated in efflux experiments, or by its metabolism. In addition, highly resistant cells which are cross-resistant to puromycin were shown to have a reduced capacity to take up labeled puromycin. These studies provide further evidence indicating that the mechanism of resistance to actinomycin D is reduced permeability to drug and suggesting that cell membrane alteration accounts for resistance to both actinomycin D and puromycin.     

Sensitivity of Shigella to antibiotics]

Three hundred and twenty two Shigella cultures isolated from dysentery patients within 1986-1989 were tested with the use of standard paper disks for their sensitivity to levomycetin, streptomycin, tetracycline, monomycin, neomycin, kanamycin, erythromycin, gentamicin, carbenicillin, ampicillin, oxacillin, methicillin and doxycycline. The number of the cultures belonging to Shigella sonnei amounted to 85.1 per cent of the total number of the strains studied. 91.9, 89.5, 87.3, 87.3, 80.1 and 80.1 per cent of the cultures were sensitive to gentamicin, kanamycin, carbenicillin, neomycin, levomycetin and ampicillin, respectively. 99.4 per cent of the isolates were resistant to streptomycin and 97.2 per cent were resistant to tetracycline. The sensitivity to erythromycin remained rather high (70.2 per cent). The overwhelming majority of the Shigella sonnei isolates had multiple resistance.     

Antibiotic sensitivity of El Tor Vibrio cholerae after exposure to various pesticides and mineral fertilizers]

The strains of El Tor Vibrio cholerae were exposed to different concentrations of pesticides (fazolone, treflane, prometrine, magnesium chlorate, omait and gardon) and mineral fertilizers (superphosphate, ammophos and carbamide) for 2 to 135 days. The subcultures of various ages were tested for their sensitivity to 16 antibiotics. The whole of 229 cultures were tested. There was a general tendency to lowering of the El Tor vibrio sensitivity to the majority of the antibiotics tested. The vibrio strains resistant to the antibiotics widely used in medical practice i. e. levomycetin, streptomycin, tetracycline, lincomycin, neomycin and kanamycin were isolated.     

Genetic analysis of tumorigenesis: IV. Chromosome reduction and marker segregation in progeny clones from Chinese hamster cell hybrids.

Hybrid cells produced by the fusion of pairs of cells, one a tumorigenic derivative of CHEF/16 and the other a nontumorigenic derivative of CHEF/18, give rise to clones which are largely tetraploid, but rare reduced hybrids with chromosome counts in the diploid range have been recovered from tumors of hybrid origin. This paper describes the recovery in cell culture of reduced hybrids in the diploid range by selection with 5-bromodeoxyuridine (BrdU) or methylcellulose as well as by growth in culture of cells from excised tumors. All selected subclones were tumorigenic and resistant to BrdU, but they segregated for resistance to 6-thioguanine. Unselected subclones were tetraploid, nontumorigenic, and sensitive to both drugs. These data show that chromosome reassortment as well as extensive chromosome reduction both occur in a small fraction of the population during growth of each hybrid clone.     

Induced deletions within a cluster of resistance genes in the mec region of the chromosome of Staphylococcus aureus

Variants of a methicillin-resistant Staphylococcus aureus showing loss of or reduced resistance to the antibiotic were isolated at frequencies of 0.1-100% from cultures which had been starved, grown at elevated temperature, or given small doses of UV radiation. Three types of variant were identified on the basis of population distribution of resistance to the antibiotic, and field-inversion gel electrophoresis of digests of the chromosome cut with the rare-cutting restriction endonuclease SmaI. Type I variants are methicillin-sensitive and have a deletion in the mec region of the chromosome. Type II variants have reduced methicillin resistance and rearranged DNA elsewhere in the chromosome. Type II variants show reduced methicillin resistance and no detectable change in the chromosome. Type I deletions were mapped using cloned fragments from the mec region. In 13 of the 16 independently isolated deletion mutants, one of the deletion endpoints appears to correlate with the positions of insertion sequences or transposons found in this region of the staphylococcal chromosome.     

Experimental resistance of Vibrio cholerae el tor to nalidixic acid and fluoroquinolones]

It was shown that sensitivity of Vibrio cholerae eltor P-5879 to tetracycline, levomycetin, furazolidone, trimethoprim/sulfamethoxazole, aminoglycosides, beta-lactams, rifampicin, quinolones in vitro correlated with drugs efficacy in the treatment of experimental cholera of albino mice. Mutants of V. cholerae eltor P-5879 Nalr resistant to nalidixic acid (MIC 160-200 mg/l) formed with frequency 10(-9)-110(-8) had no cross resistance to fluoroquinolones. But the efficacy of ofloxacin, lomefloxacin, norfloxacin against these mutants in vivo reduced, though it was not changed in vitro. Mutants of V. cholerae eltor P-5879 resistant to fluoroquinolones and selected after culturing in the presence of the drugs had cross resistance to all quinolones studied. Infection caused by Cpfr mutant could not be treated with nalidixic acid and fluoroquinolones, therapeutic efficacy of rifampicin and beta-lactams, also reduced though sensitivity in vitro was not changed. The results of investigation proves the necessity of quinolones use for cholerae treatment as it is recommended for other severe enteric infections.     

Effect of prodigiozan and pyrimidine derivatives on the effectiveness of the antibiotic therapy of experimental infections]

The effect of prodigiozan and pyrimidine derivatives, such as methyluracyl, oxymetacyl and 2-methyl-4-amino-6-hydroxypyrimidine on the efficiency of antibiotic therapy of experimental infections caused by Staph. aures and E. Coli under conditions of immune depression due to levomycetin, prednisolone, 6-mercaptopurine and ionizing radiation was studied. The effect of prodigiozan on the efficiency of the antibiotic treatment of staphylococcal infection in the presence of the immune depression due to 6-mercatopurine, levomycetin and prednisolone was higher than that of pyrimidines. The combined use of prodigiozan and pyrimidines usually was not more effective than the use of every drug alone. The efficiency of the drugs in radiation disease was the same. After prednisolone administration prodigiozan increased the host resistance to the infection without the antibiotic use.