Paradoxical effect of synthetic hydroxy isothiocyanates on antimicrobial action of aminoglycosides.

Hydroxy isothiocyanates, especially 2-(4-hydroxyphenyl)ethyl isothiocyanate (hITC), were examined for antimicrobial synergism with streptomycin (SM) against Escherichia coli. On the course of those experiments, a peculiar suppression of SM by a low concentration of hITC was observed, besides the antibacterial synergism of hITC with SM. Further, bactericidal activity of SM in physiological saline was reduced by addition of hITC. Time course experiments proved that the antagonistic effect of hITC occurred in an early stage after exposure of bacterial cells to SM.

Dizocilpine attenuates streptomycin-induced vestibulotoxicity in rats.

NMDA receptor mediated excitotoxicity contributes substantially to aminoglycoside antibiotic-induced cochlear damage. Since vestibular as well as cochlear hair cells have glutamatergic synapses, aminoglycoside-induced vestibulotoxicity may also have an excitotoxic component. This hypothesis was tested by examining the effects of the uncompetitive NMDA receptor antagonist dizocilpine on streptomycin-induced vestibulotoxicity. Streptomycin-treated rats exhibited almost complete destruction of sensory hair cells in the crista ampullaris, vestibular impairment in the drop test, and hyperkinesia. Concurrent treatment with dizocilpine not only rescued a substantial population of sensory hair cells in the cristae, but prevented the attendant hyperkinesis and vestibular impairments. These results indicate that excitotoxic mechanisms contribute to aminoglycoside-induced vestibulotoxicity and that NMDA antagonists may be useful in attenuating aminoglycoside ototoxicity.

Reduction of streptomycin-induced acute and chronic toxicities.

The acute and chronic toxicities of streptomycin sulfate (SS) and of the streptomycin hydrochloride-calcium chloride complex (SCC) were compared. The LD50 determined in mice was significantly higher for SCC than for SS. Chronic toxicity was evaluated by recording the nystagmus induced by damped torsion pendulum in rabbits. SS and SCC treatments (200 mg/kg intramuscularly of absolute streptomycin base) decreased the duration, the maximal frequency, and the total number of beats of nystagmus. However, SCC-induced changes were significantly lower than SS-induced ones. The extent of the lesion in the crista ampullaris was evaluated by light and electron microscopy and was correlated with the electrophysiological findings. Because the authors also demonstrated that there are no differences in the antibacterial effects of these salts, SCC may have a place in long-term streptomycin treatment.

Calcium as a counteractive agent to streptomycin induced respiratory depression: an in vivo electrophysiological observation.

Effect of streptomycin on respiratory function in cats was studied. It was observed that streptomycin at a dose of 40 mg/kg body weight intravenously (i.v.) caused respiratory failure or streptomycin induced respiratory depression (SIRD). This respiratory failure is not linked with Herring-Breuer stretch receptors because the effect remained unaltered in artificially ventilated cats. The involvement of central structures in SIRD can be discarded since intracarotid and intraventricular administration of streptomycin failed to produce any change in respiration. Studies on monosynaptic reflex, dorsal and ventral root activities of spinal phrenic and intercostal nerves, and on fusimotor and alpha-motor neuron activities of spinal intercostal and phrenic nerves in decerebrated cats indicated clearly that respiratory depression is not only due to blockade at neuromuscular junction but due to functional depression at the level of muscle receptors and spinal cord motor neurons. The respiratory depression induced by streptomycin was more or less completely reversed when calcium was administered intravenously from external source. It is speculated that streptomycin induced respiratory depression may be mediated through calcium inhibition which can be treated with external calcium in conjunction with artificial respiration.

[The utilization of heme iron by Yersinia pestis in human blood and blood sera]. / Utilizatsiia gemovogo zheleza Yersinia pestis v krovi i syvorotkakh krovi cheloveka.

Y. pestis, the causative agents of plague, have been found to be incapable of using heme iron bound to haptoglobin and hemopexin complexes in human blood and blood serum, and protein components of the serum are not the factors inhibiting this process. At the same time iron of free hemoglobin can be successfully utilized by Y. pestis in the systems used in this study. On the contrary, hemin not only produces any stimulating effect on the growth of Y. pestis in blood serum, but leads to the death of these bacteria [correction of lasteria].

[The isolation and characteristics of the biological and genetic properties of neamin-resistant mutants of Salmonella abortus-ovis that are promising for vaccine creation]. / Poluchenie i kharakteristika biologicheskikh i geneticheskikh svoistv ustoichivykh k neaminu mutantov Salmonella abortusovis, perspektivnykh dlia sozdaniia vaktsin.

Neamine-resistant mutants were obtained from S. abortus ovis virulent strain. These mutants were divided into three classes according to their sensitivity to streptomycin: mutants completely retaining their sensitivity, mutants sensitive to moderate and high doses of the antibiotic. On the basis of genetic analysis carried out with the use of bacteriophage P22, the Near mutation of class Near 100 Strr 500 mutants was identified as nea B, and the Near mutation of class Near 100 Strs, as nea A. The study showed a decreased virulence of Salmonella transductants that acquired both neamine-resistant mutation of the two classes and streptomycin-resistant mutation. The streptomycin-resistant mutation produced no changes in the virulence of these bacteria. According to the results of experiments on mice, mutants of the two classes under study were found to possess protective activity.

High calcium solutions prevent the depressant effects of aminoglycoside antibiotics on central synaptic transmission in rat hippocampal slices.

1. The aminoglycoside antibiotics neomycin and streptomycin were tested on the synaptic activity of the CA1 pyramidal neuron-Schaffer collateral interconnections in rat hippocampal slices. 2. Neomycin (0.5 mM) decreased the magnitude and shifted to the right the stimulus-response curve of the somatic and dendritic excitatory postsynaptic potential (EPSP) and the somatic population spike (PS). 3. Streptomycin (1 mM) decreased the magnitude and shifted to the right the stimulus-response curve of the somatic and dendritic EPSP and the somatic PS. 4. High (+2 mM) calcium solutions were able to prevent the effects induced by the antibiotics and to shift to the left the stimulus-response curve of the 0.5 mM neomycin and 1 mM streptomycin treated hippocampal slices. 5. The data demonstrate an effect of aminoglycoside antibiotics on a central mammalian hippocampal synapses, that may depend on an interference of the drugs on calcium conductances.

[Localization of the genes coding for the specific modification-restriction system in the E. coli tF strain]. / Lokalizatsiia na genite, kodirashti spetsifichnata modifikatsionno-restriktsionna sistema v shtama E. coli tF.

The recombinant Escherichia coli tF strain has been shown to have its own specific modificational and restrictional system. In order to establish the location of genes, coding this system a plasmid has been isolated from the investigated strain, which substantiates the resistance to streptomycin. The plasmid DNA has been transformed into a recipient strain, E. coli O, which has no modificational and restrictional system of its own. The newly obtained E. coli O (ptF) transformants also have proved negative with regard to their testing for the presence of a specific modificational and restrictional system. The conclusion follows that the genes, coding the modificational and restrictional system of the E. coli tF strain are not located in the plasmid isolated from it.

[Isolation and characteristics of the biological and genetic properties of neamin-resistant mutants of Salmonella typhimurium and Salmonella dublin candidates for vaccine creation]. / Poluchenie i kharakteristika biologicheskikh i geneticheskikh svoistv ustoichivykh k neaminu mutantov Salmonella typhimurium i Salmonella dublin, perspektivnykh dlia sozdaniia vaktsin.

Mutants, resistant to neamine and spectinomycin, have been isolated from S. typhimurium and S. dublin highly virulent strains. The neamine-resistant mutants can be divided into 3 classes in accordance with their sensitivity to streptomycin: sensitive, resistant to low and high concentrations of this antibiotic. The transduction analysis with the use of bacteriophage P 22 has revealed that the spectinomycin-resistant mutations under study are spc A mutations, while the mutations leading to resistance to neamine in class Near Strr 500 are nea B mutations. The mutation leading to resistance to spectinomycin (spc A) has been found to produce no changes in the virulence of salmonellae in the intraperitoneal infection of mice. The mutations leading to resistance to neamine and streptomycin (nea B and str A) have been found to decrease virulence.

[Biochemical characteristics of the determinants of drug resistance to gentamycin from clinical strains of gram-negative microorganisms]. / Biokhimicheskaia kharakteristika determinantov lekarstvennoi ustoichivosti k gentamitsinu iz klinichekikh shtammov gramotritsatel'nykh mikroorganizmov.

Three to four aminoglycoside inactivating enzymes were detected in cell-free extracts of clinical strains of gram-negative bacteria including Pseudomonas, Escherichia, Serratia, Enterobacter and Klebsiella and in cell-free extracts of their transconjugants. The clinical strains were selected by the feature of gentamicin resistance. All the strains contained AAC(3), APH(3') and APH(3"). In addition to these enzymes 12 out of 25 investigated strains contained AAD(2"). The biochemical characteristics of the gentamicin resistance determinant cloned from the clinical strains on the plasmid vector pUC 19 were studied. By the size of the insertion element pAA4 was the smallest among the constructed hybrid plasmids determining gentamicin resistance. It was shown that just this plasmid determined formation of the two gentamicin inactivating enzymes: AAC(3) and AAD(2") in the transformants carrying it.

Genetic analysis of a streptomycin-resistant oligosporogenous Bacillus subtilis mutant.

Strain SRB15T+, a streptomycin-resistant, oligosporogenous mutant of Bacillus subtilis, contains two mutations, fun and strR. These mutations were mapped by PBS-1 mediated transduction and by transformation to two different sites in the cysA-linked region of the B. subtilis chromosome. The fun mutation mapped very close to rpsLl, a classic strA mutation, whereas strR mapped to a site distal to rpsE. The effects of these mutations on growth, sporulation, and streptomycin resistance in vivo and in vitro were determined. The fun mutation gave a different phenotype than did the rpsLl mutation and caused altered migration of a ribosomal protein which was identified as S12, the protein encoded by rpsL. It therefore appears that fun is an allele of the rpsL gene.

[Alteration of the acute toxicity and various pharmacologic effects of streptomycin sulfate by calcium 4'-phosphopantothenate]. / Izmenenie ostroi toksichnosti i nekotorykh farmakologicheskikh éffektov streptomitsina sul'fata 4'-fosfopantotenatom kal'tsiia.

The effect of calcium 4'-phosphopantothenate (CPP) on acute toxicity of streptomycin and the decrease by the antibiotic of the muscle working capacity, "holes" reflex, body temperature and oxygen intake was studied on 258 albino mice weighing 22-26 g. Medical calcium pantothenate (CPA) was used for control purposes. CPP is an antagonist of streptomycin sulfate. In a dose of 1/10 or 1/5 of the LD50 injected intraperitoneally CPP lowered acute toxicity of streptomycin and prevented its effect in a dose of 0.11--1.1 g/kg injected subcutaneously on the muscle working capacity, "holes" reflex and body temperature. The spectrum index of the CPP antitoxic effect was equal to 22.5. By its acute toxicity CPP (LD50 1.18 +/- 0.07 g/kg) did not differ from CPA (LD50 1.25 +/- 0.08 g/kg). The efficacy of CPP, by its antitoxic spectrum, was 1.8 times higher than that of CPA. CPA lowered the streptomycin effect on the "holes" reflex and body temperature, while CPP prevented it. Both the drugs did not influence the decrease in the oxygen consumption induced by streptomycin.

Prevalence of transformable Streptococcus mutans in human dental plaque.

A total of 100 strains of Streptococcus mutans serotypes c/e/f and d/g, freshly isolated from dental plaque, were screened for their ability to undergo genetic transformation to streptomycin resistance. Of the serotype c/e/f strains, 28% were found to be transformable, whereas none of the serotype d/g strains could be transformed by donor DNA from streptomycin-resistant S. mutans strains of either serotype c or d/g. Two of the transformable serotype c/e/f strains were transformed by DNAs from a variety of oral streptococcal species commonly found in the microflora.

[Effect of conjugative R plasmids on the virulence of antibiotic-sensitive Salmonella strains and their streptomycin-resistant mutants]. / Vliianie kon"iugativnykh R-plazmid na virulentnost' chuvstvitel'nykh k antibiotikam shatmmov sal'monell i ikh streptomitsinorezistentnykh mutantov.

The pathogenicity level of antibiotic sensitive and streptomycin resistant strains of S. typhimurium, S. paratyphi B and S. kottbus changed under the effect of identical R plasmids more frequently in contrary directions. The conjugative plasmids of antibiotic resistance widened the ranges of the virulence changes in the Salmonella serovars for albino mice. It was found that 7 out of 8 plasmids studied significantly decreased and increased the virulence of the antibiotic sensitive Salmonella strains. As a rule, R plasmids of various origin decreased the virulence of all the tested streptomycin chromosome resistant causative agents of salmonellosis.

Mechanism of antibiotic resistance in Mycobacterium intracellulare.

The mechanism of resistance of Mycobacterium intracellulare strain 103 and other clinical isolates to a variety of drugs including aminoglycoside and peptide antibiotics was investigated. Enzymatic inactivation of aminoglycoside and peptide antibiotics could not be demonstrated. Ribosomes of the strain were found to be sensitive to the antibiotics. The levels of resistance of strain 103 and other clinical isolates decreased dramatically when the culture medium was changed from Dubos agar to Tween 80-containing agar. These results suggest that a permeability barrier is the reason for naturally occurring resistance in M. intracellulare.

[Intergeneric bacterial conjugation in crosses of Vibrio cholerae biotype proteus X Serratia marcescens]. / Mezrodovaia kon"iugatsiia bakterii pri skreshchivaniiakh Vibrio cholerae biotip proteus X Serratia marcescens.

Intergeneric conjugants were obtained in crosses of bacteria Vibrio cholerae biotype proteus (donor) x Serratia marcescens. The study of exconjugants demonstrates the following characteristics: 1. The majority of clones isolated possess some morphological characters of the donor (colourlessness and transparency of colonies) which gradually disappear during successive transfers and return to the phenotype of recipients (red colour of colonies); 2. Exconjugants acquire a plasmid factor of the fertility of vibrios (P-factor) and may transmit it to other cells; 3. The majority of exconjugants are agglutinated by immune sera of both donor and recipient; 4. The factor of streptomycine resistance is transmitted from the donor to a recipient. Conjugants acquire streptomycine resistance from the donor and laevomycetine (chloramphenicol) resistance from the recipient and can grow on a nutrient medium containing both antibiotics; 5. The conjugants isolated show a great diversity in a number of characters and, supposedly, form a genetically heterogenous group. A great part of exconjugants is characterized by a slow growth, some of them being not viable and unable to survive during transfers. In connection with instability of conjugants, we suppose that the exongenome is not incorporated into the chromosome of the recipient; more likely, it exists in a form of self-replicating duplex, or is connected with a plasmid genome.

[Method of selecting mutations for the plasmid genes of streptomycin resistance in Escherichia coli K-12 cells]. / Metod selektsii mutatsii po plazmidnym genam ustoichivosti k streptomitsinu v kletkakh Escherichia coli K-12.

Evidence is presented that streptomycin-dependent mutants of Escherichia coli K-12 are incompatible with the functional activity of streptomycin-resistance genes coding for aminoglycoside adenilyl transferase. On the basis of this phenomenon, a method for selection of streptomycin-sensitive mutations in these genes is proposed, and the possibility of the direct selection of hybrid DNA molecules carrying inserts inactivating streptomycin-resistance genes is discussed. The effectiveness of the method for isolation of streptomycin-sensitive R100.1 plasmid derivatives was demonstrated.