Antibiotic sensitivity of plague microbe strains from foreign countries]

The method of serial dilutions on the Hottinger agar was applied to comparative assay of antibiotic sensitivity in 50 strains of the plague microbe isolated abroad and in 5 strains isolated in the plague focus in the Central Caucasus. The antibiotics used in the assay were the following: streptomycin, gentamicin, doxycycline, monomycin, kanamycin, tetracycline, erythromycin, ristomycin, lincomycin and polymyxin M. Irrespective of the origin, all the isolates were resistant to erythromycin, lincomycin and polymyxin M. The levels of the sensitivity to the other antibiotics were different. The data serve as a ground for the statement that there is no tendency to development of antibiotic resistance in the plague microbe in patients treated with high doses of the antibiotics and mainly streptomycin. Along with streptomycin, such antibiotics as gentamicin, tetracycline, doxycycline and kanamycin are useful in the therapy of plague and require further investigation.     

Role of antibiotics in lipid peroxidation.

Alterations in the levels of lipid peroxides, superoxide dismutase, catalase, glutathione, free fatty acid and serum ceruloplasmin were studied in rats fed with high fat cholesterol diet administered different antibiotics, viz. ampicillin, tetracycline, streptomycin, chloramphenicol and cephalosporin. The concentrations of lipid peroxides, glutathione, free fatty acid decreased in most of the tissues, except in tetracycline, streptomycin and cephalosporin treated rats. The changes observed in the activities of superoxide dismutase and catalase in the liver and kidney of these antibiotics administered groups also are in accordance with the changes in lipid peroxides. The results show that the tetracycline is hepatotoxic and nephrotoxic, while cephalosporin and streptomycin are nephrotoxic.     

Cross-resistance in Cell Lines of Nicotiana sylvestris Selected for Resistance to Individual Antibiotics

Cell lines initially selected for resistance to the antibioticskanamycin, streptomycin and chloramphenicol, were each testedfor resistance to several different antibiotics. Only the kanamycinresistant lines showed any cross-resistance to other antibiotics.The three lines tested were resistant to streptomycin and neomycin,while one of them, KR103, was also resistant to chloramphenicolearly in its history, although this resistance was subsequentlylost. None of the lines showed any resistance to cycloheximide. Nicotiana sylvestris, cell culture, cross-resistance, antibiotics, chloramphenicol, kanamycin, streptomycin, neomycin, cycloheximide, cytoplasmic mutants, callus     

4种抗生素对蚯蚓-污泥系统细菌群落结构的影响

蚯蚓可摄食污泥中的有机物,其肠道微生物群落在其分解过程中起着主要的作用。利用赤子爱胜蚓(Eisenia foetida)和人工湿地基质构建蚯蚓-污泥系统,添加氯霉素、四环素、链霉素和青霉素4种抗生素,研究不同抗生素对污泥和蚓粪的细菌群落结构的影响。采用高通量测序技术比较分析污泥和蚓粪的细菌多样性及群落结构变化。结果表明,外加抗生素能够导致污泥的Chao1和ACE指数降低,同时降低拟杆菌门和变形菌门的相对丰度,加入氯霉素和青霉素会增加厚壁菌门的相对丰度,降低酸杆菌门、放线菌门和绿弯菌门的相对丰度,加入四环素和链霉素则与之相反。蚓粪样品中,添加氯霉素和链霉素导致Chao1和ACE指数降低,而添加四环素和青霉素则导致Chao1和ACE指数升高,外加抗生素可降低拟杆菌门的相对丰度,增加放线菌门、变形菌门和疣微菌门的相对丰度。主成分分析(PCA)和聚类分析表明,氯霉素和青霉素对污泥细菌群落影响作用相似,四环素与链霉素效果类似;氯霉素对蚓粪群落结构的影响小于其他抗生素。研究结果显示,抗生素可影响污泥和蚓粪的细菌多样性及群落结构,不同抗生素对污泥和蚓粪的影响程度存在差异。     

Effect of antibiotics on development in vitro of hamster pronucleate ova

Antibiotics are commonly added to embryo culture media, but effects on embryo development have not been examined thoroughly. Hamster ova were used to investigate whether penicillin, streptomycin or gentamicin affect embryo development in vitro. Ova were collected 10 h post activation by spermatozoa in vivo and cultured in five treatments: 1) Control: chemically-defined medium HECM-9 with no antibiotics; 2) HECM-9 with 100 IU/mL penicillin; 3) HECM-9 with 50 microg/mL streptomycin; 4) HECM-9 with 10 microg/mL gentamicin and 5) HECM-9 with both 100 IU/mL penicillin and 50 microg/mL streptomycin. Individually, penicillin, streptomycin and gentamicin did not affect embryo development to the 8-cell stage at 58 h post oocyte activation, or morula/blastocyst stages, or blastocysts alone at 82 h post activation. However, when penicillin and streptomycin were both present in the culture medium the percentages of 8-cell embryos at 58 h and blastocysts at 82 h were significantly lower than the control. No antibiotic treatment improved hamster embryo development in vitro. We caution against the use of penicillin and streptomycin together for hamster embryo culture, and show that it is not necessary to include any antibiotics in embryo culture media for up to 72 h if proper sterile technique is used with an oil overlay.     

Antibacterial and Antifungal Spectra of Antibiotics Produced by Different Strains of Erwinia herbicola (= Pantoea agglomerans)

Nine antibiotic producer strains of Erwinia herbicola (=Pantoea agglomerans), belonging to different groups, strongly inhibited growth of 21 streptomycin sensitive strains and 6 streptomycin resistant strains of E. amylovora. The antibacterial spectra of antibiotics produced by the tested strains of E. herbicola were mainly limited to E. amylovora and related tested species. The tested strains of E. amylovora that are resistant to streptomycin did not show cross-resistance to the different types of antibiotics produced by the tested strains of E. herbicola. The antibiotics produced by the different tested strains of E. herbicola did not exert any activity on tested fungi with the exception that strains Eh 153 and Eh 351 slightly inhibited the growth of Verticillium dahliae.     

Evaluation of five antibiotics on larval gut bacterial diversity of Plutella xylostella (Lepidoptera: Plutellidae)

Larvae of the diamondback moth, Plutella xylostella L. (Lepidoptera: Plutellidae), have rich microbial communities inhabiting the gut, and these bacteria contribute to the fitness of the pest. In this study we evaluated the effects of five antibiotics (rifampicin, ampicillin, tetracycline, streptomycin sulfate and chloramphenicol) on the gut bacterial diversity of P. xylostella larvae. We screened five different concentrations for each antibiotic in a leaf disc assay, and found that rifampicin and streptomycin sulfate at 3 mg/mL significantly reduced the diversity of the bacterial community, and some bacterial species could be rapidly eliminated. The number of gut bacteria in the rifampicin group and streptomycin sulfate group decreased more rapidly than the others. With the increase of antibiotic concentration, the removal efficiency was improved, whereas toxic effects became more apparent. All antibiotics reduced larval growth and development, and eventually caused high mortality, malformation of the prepupae, and hindered pupation and adult emergence. Among the five antibiotics, tetracycline was the most toxic and streptomycin sulfate was a relatively mild one. Some dominant bacteria were not affected by feeding antibiotics alone. Denaturing gradient gel electrophoresis graph showed that the most abundant and diverse bacteria in P. xylostella larval gut appeared in the cabbage feeding group, and diet change and antibiotics intake influenced gut flora abundance. Species diversity was significantly reduced in the artificial diet and antibiotics treatment groups. After feeding on the artificial diet with rifampicin, streptomycin sulfate and their mixture for 10 days, larval gut bacteria could not be completely removed as detected with the agarose gel electrophoresis method.     

The use of antibiotics to reduce bacterioplankton uptake of phytoplankton extracellular organic carbon (EOC) in the Potomac River estuary

Phytoplankton production and accumulation of extracellular organic carbon (EOC) was tracked during diel intervals in microcosms by inhibiting bacterioplankton assimilation of EOC with streptomycin and kanamycin. Bacterioplankton production (³H-thymidine incorporation) and metabolism (¹⁴C-glucose incorporation) were monitored in samples collected from the Potomac River estuary to determine the effect of the antibiotics. Particulate (i.e., raw water) primary production and EOC (i.e., water passing through 1.0 μm glass fiber filter) production rates were monitored to determine the impact of antibiotics on phytoplankton. In preliminary experiments, neither streptomycin nor kanamycin alone significantly inhibited bacterioplankton activity compared to controls, but when both were present secondary production and metabolism were reduced up to 90%, and remained as such for 45 h. During field evaluations using a streptomycin and kanamycin mixture (50 μM each) particulate primary production and EOC production were not statistically different in control and antibiotic treated samples indicating that the antibiotics did not negatively influence phytoplankton production rates. In the presence of antibiotics dissolved free amino acids (DFAA) and, to a lesser extent, monosaccharides were significantly elevated compared to controls. This study demonstrates that streptomycin and kanamycin are capable of inhibiting bacterioplankton metabolism and uptake of dissolved organic carbon (DOC) in the samples tested so that the contribution of EOC to the DOC pool and to bacterioplankton metabolism could be measured and assessed.     

In vitro selection and characterization of streptomycin-binding RNAs: recognition discrimination between antibiotics.

As pathogens continue to evade therapeutical drugs, a better understanding of the mode of action of antibiotics continues to have high importance. A growing body of evidence points to RNA as a crucial target for antibacterial and antiviral drugs. For example, the aminocyclitol antibiotic streptomycin interacts with the 16S ribosomal RNA and, in addition, inhibits group I intron splicing. To understand the mode of binding of streptomycin to RNA, we isolated small, streptomycin-binding RNA aptamers via in vitro selection. In addition, bluensomycin, a streptomycin analogue that does not inhibit splicing, was used in a counter-selection to obtain RNAs that bind streptomycin with high affinity and specificity. Although an RNA from the normal selection (motif 2) bound both antibiotics, an RNA from the counter-selection (motif 1) discriminated between streptomycin and bluensomycin by four orders of magnitude. The binding site of streptomycin on the RNAs was determined via chemical probing with dimethylsulfate and kethoxal. The minimal size required for drug binding was a 46- and a 41-mer RNA for motifs 1 and 2, respectively. Using Pb2+ cleavage in the presence and absence of streptomycin, a conformational change spanning the entire mapped sequence length of motif 1 was observed only when both streptomycin and Mg2+ were present. Both RNAs require Mg2+ for binding streptomycin.     

Antibiotic penetration through the blood-brain barrier in rats and the effect on this process of proteolytic enzymes]

Penetration of penicillin, ampicillin, oxacillin, tetracycline, streptomycin and gentamycin through the hemato-encephalic barrier in rats and effect of proteolytic enzymes on the above process were studied comparatively. The levels of penetration to the brain were highest for ampicillin, then followed penicillin, tetracycline, oxacillin, streptomycin and gentamycin. Preliminary intramuscular administration of trypsin and chimotrypsin (10 mg/kg) to the animals had no effect on permeability of the hemato-encephalic barrier for the antibiotics tested, except penicillin. Higher levels of the antibiotics in the brain tissue may be explained by higher antibiotic blood levels under the effect of proteolytic enzymes.     

Effects of subinhibitory concentrations of antibiotics on biological properties ofSalmonella typhimurium

We followed the effects of subinhibitory concentrations (sub-MICs) of 7 antibiotics (ticarcilin, cefotaxim, streptomycin, gentamicin, ciprofloxacin, pefloxacin, mitomycin C) on the sensitivity of aSalmonella typhimurium strain to standard bacteriophages, on the phage DNA as well as on the factors of virulence (permeability and cytotoxic activity). The phage type was not changed by the sub-MICs of the tested antibiotics. However, differences were found in culture filtrates prepared from the bacterial suspensions of the strain cultivated with the sub-MICs. Marked inducing effects on phage DNA were exhibited by mitomycin C (1/2, 1/4, 1/8 of the MIC), pefloxacin (1/2, 1/4, 1/8 of the MIC) and ciprofloxacin (1/2, 1/4, weakly also 1/8 of the MIC). Ticarcilin (1/2 of the MIC), like the aminoglycosides streptomycin and gentamicin (1/2, 1/4, 1/8 of the MIC), had a weak effect. Sub-MICs of the studied antibiotics (with the exception of 1/8 of the MIC of ciprofloxacin and 1/4 of the MIC of ticarcilin) decreased the permeability reaction in rabbit skin. Most effective was streptomycin (1/2 of the MIC). Sub-MICs of the tested antibiotics (with the exception of 1/4 and 1/8 of the MIC of ciprofloxacin and 1/4 of the MIC of pefloxacin) caused also an inhibition of the factor responsible for morphological changes on Vero cells. Gentamicin and streptomycin were effective at all the sub-MICs tested.     

Effect of proteolytic enzymes on antibiotic distribution when the preparations are administered by different routes]

The effect of proteolytic enzymes, such as terrilitine and chymotripsin on pharmacokinetics of morphocycline and streptomycin in rats after their administration by various routes was studied comparatively. The oral use of the enzymes or their introduction directly into the duodenum simultaneously or 30 minutes before the antibiotic administration did not increase the morphocycline and streptomycin levels in the biosubstrates tested. A tendency to a decrease in the serum and organ levels of the antibiotics in animals when used orally in combination with the enzymes was noted. When the drugs were administered intramuscularly, the morphocycline serum and organ levels in the rats increased insignificantly, while the streptomycin levels increased significantly. Administration of formalin as a stressor had an analogous effect which provided a supposition of a possibility of non-specific effect of the enzymes of distribution of the antibiotics on intramuscular injection of the enzymes in large doses having a local irritating effect.     

Bactericidal effects of ampicillin and streptomycin on intracellular and extracellularYersinia pseudotuberculosis

The bactericidal effect of ampicillin and streptomycin on intracellularYersinia pseudotuberculosis was studied using infected HeLa cells as a model system. The results were compared with the effect of the antibiotics on extracellular bacteria in order to evaluate the protective effect of intracellular residence. Ampicillin and streptomycin could be shown to be effective against intracellular bacteria, but had a more pronounced effect on extracellular bacteria. The bactericidal effect of ampicillin and streptomycin at different concentrations follows a commonly accepted formula concerning the relationship between concentration of disinfectant and time of disinfection.     

On the interaction between heparin and some aminoglycoside antibiotics

An interaction between the aminoglycoside antibiotics and heparin wherein charge transfer complexes are formed has been investigated to determine the degree of inhibition of antibacterial function of the antibiotic in the complexed form.Minimum inhibitory concentration (MIC) values have been obtained for the action of the aminoclycoside antibiotics tobramycin, gentamicin, amikacin, kanamycin, and streptomycin, on a sensitive strain ofE. coli. Growth curves ofE. coli determined at concentrations of these antibiotics just below the MIC demonstrated significant lengthening of the lag phase relative to control growth curves generated in the absence of antibiotic. Heparin (1 U ml^–1 and 10 U ml^–1) had no effect on control growth curves; however, particularly at the higher concentration, it reduced the effect on the lag phase produced by the aminoglycoside antibiotics. Thus kanamycin, gentamicin, and tobramycin were most affected, while amikacin and streptomycin were least affected. The rank order of inhibition of antibiotic activity by interaction with heparin was in qualitative agreement with previously published figures for the degree of complexation between antibiotics and heparin.     

Inhibition of nuclear pre-mRNA splicing by antibiotics in vitro.

A number of antibiotics have been reported to disturb the decoding process in prokaryotic translation and to inhibit the function of various natural ribozymes. We investigated the effect of several antibiotics on in vitro splicing of a eukaryotic nuclear pre-mRNA (beta-globin). Of the eight antibiotics studied, erythromycin, Cl-tetracycline and streptomycin were identified as splicing inhibitors in nuclear HeLa cell extract. The K(i) values were 160, 180 and 230 microm, respectively. Cl-tetracycline-mediated and streptomycin-mediated splicing inhibition were in the molar inhibition range for hammerhead and human hepatitis delta virus ribozyme self-cleavage (tetracycline), of group-I intron self-splicing (streptomycin) and inhibition of RNase P cleavage by some aminoglycosides. Cl-tetracycline and the aminocyclitol glycoside streptomycin were found to have an indirect effect on splicing by unspecific binding to the pre-mRNA, suggesting that the inhibition is the result of disturbance of the correct folding of the pre-mRNA into the splicing-compatible tertiary structure by the charged groups of these antibiotics. The macrolide, erythromycin, the strongest inhibitor, had only a slight effect on formation of the presplicing complexes A and B, but almost completely inhibited formation of the splicing-active C complex by binding to nuclear extract component(s). This results in direct inhibition of the second step of pre-mRNA splicing. To our knowledge, this is the first report on specific inhibition of nuclear splicing by an antibiotic. The functional groups involved in the interaction of erythromycin with snRNAs and/or splicing factors require further investigation.     

Influence of cadmium on resistance to antibiotics in salmonellæ isolated from pigs

Repeated cultivations (4 passages) of salmonellæ (18 strains) resistant to cadmium, streptomycin and β-lactam antibiotics in Müller-Hinton Broth (MHB) and Mac-Conkey Broth (MCB) without and with CdSO₄ (2, 20 and 100 mg/L) showed a higher toxic effect of cadmium in MCB. The strains survived at CdSO₄ 100 mg/L in MHB for four transfers, in MCB only a single transfer. In dependence on the medium used and amount of metal added, the increase of resistance to antibiotics was different. In MHB, the same levels of resistance to carbenicillin and streptomycin were induced by CdSO₄ (20 and 100 mg/L), in MCB it was by 2 and 20 mg/L. Simultaneous stop of the growth of a control cultureS. typhimurium with chromosomal resistance to streptomycin, isolates with and without plasmid in MCB which contained CdSO₄ 100 mg/L, and the results of conjugal transfer of resistance suggest that changes of resistance to antibiotics were not medated by determinants of resistance to antibiotics. The binding of cadmium to outer membrane protein can cause a decreased permeability to these antibiotics as a resistance mechanism.     

Effect of antibiotics on the resistance of white mice to C1. perfringens toxin]

The effect of potassium benzylpenicillin, streptomycin sulfate and chlortetracycline on experimental gangrenous intoxication was studied. When the antibiotics were injected before intoxication, the albino mice resistance did not significantly change. When the antibiotics were injected immediately after the toxin administration, the resistance of the test animals markedly decreased.     

Mechanism of streptomycin resistance in Leptospira biflexa strain Urawa

The mechanism of streptomycin resistance of Leptospira biflexa was investigated. A streptomycin-resistance mutant of Leptospira showed cross-resistance to dihydrostreptomycin but not to other antibiotics. Enzymatic inactivation of the drug could not be demonstrated in this mutant. Protein synthesis on the ribosomes from the mutant was insensitive to streptomycin. These results suggest that ribosomal resistance is the reason for streptomycin resistance in Leptospira biflexa.     

Effect of antibiotics on indices of immunologic reactivity in mice

The effect of ristomycin, chloramphenicol, kanamycin, benzylpenicillin, streptomycin, and cephaloridine on the indices of cellular and humoral immunity was studied comparatively on intact animals and on animals with secondary immune deficiency. The study of the antibiotic effect on the count of rosette-forming lymphocytes (RFL) and the total count of lymphocytes showed that all the antibiotics except streptomycin induced a significant decrease in the count of RFL. The most active was kanamycin. It lowered the count of RFL 5-fold as compared to the control. The total count of lymphocytes was lowered after administration of ristomycin, chloramphenicol and kanamycin. In the animals with immune deficiency induced by cyclophosphamide benzylpenicillin potentiated the inhibitory effect of cyclophosphamide on the weight of the lymphoid organs, while streptomycin lowered the effect of cyclophosphamide. No such effect was observed with the use of the other antibiotics. The data indicated the necessity of taking into account the effect of various antibiotics on the immune system, especially under conditions of immune deficiency.     

Determination of antibiotics using luminescent Escherichia coli and serum

The methodical bases for detecting antibiotics using a bioluminescent assay and blood serum are briefed. Antibiotics inhibit the luminescence of a genetically engineered Escherichia coli strain. The degree of inhibition depended on the type of antibiotic, its concentration, and the time of cell incubation with antibiotic. The highest cell sensitivity was recorded towards the aminoglycoside antibiotics, which amounted to 85 +/- 10 ng/ml for gentamicin and streptomycin. The sensitivity of this system to a number of antibiotics essentially increased when the cells were previously activated with blood serum. The sensitivity of this method for gentamicin and streptomycin in the presence of blood serum amounted to 2.5 +/- 0.5 ng/ml; for tetracycline, 45 +/- 8 ng/ml. Use of the sera containing specific antibodies to the antibiotic detected provided a high sensitivity of the biosensor tested. Comparison of the luminescences of E. coli cells activated with normal and specific antisera upon incubation with an antibiotic allows the type of antibiotic and its quantitative content in the sample to be determined. Characteristic of the analysis of antibiotics with the help of recombinant E. coli are a high accuracy, sensitivity, specificity, simplicity, and a short time needed for measurement.