Interaction of cytoplasmic membrane and ribosomes in Escherichia coli: spectinomycin-induced disappearance of membrane protein I-19.

Incubation of Escherichia coli with spectinomycin caused the disappearance of a major protein from the cytoplasmic membrane. This protein, called "I-19", was not a ribosomal protein. Its disappearance was not a result of the direct action of spectinomycin on the cytoplasmic membrane, but a result of its action on ribosomes. The disappearance was specifically induced by spectinomycin, and other antibiotics such as neomycin, erythromycin, and chloramphenicol had no effect. Although growth was not required for spectinomycin-induced disappearance of protein I-19 from the cytoplasmic membrane, the disappearance was not observed under conditions where protein synthesis was inhibited completely either by the addition of chloramphenicol or by cooling in ice. It is suggested that at least some ribosomes interact with the cytoplasmic membrane and that a modification of the mode of interaction through the action of spectinomycin on ribosomes caused the deletion of membrane protein I-19.     

The increased sensitivity of rifamycin-resistant mutants of Methylobacterium AM1 to a variety of antimicrobial agents

Rifamycin-resistant strains of Methylobacterium AM1 are more sensitive to β-lactam antibiotics, chloramphenicol, tetracycline, spectinomycin, puromycin, nalidixic acid, benzalkonium chloride and p -fluorophenylalanine than are rifamycin-sensitive strains. This suggests that mutation to rifamycin resistance is associated with a general increase in membrane permeability and may have a bearing on the use of rifamycin-resistant mutants in genetic and biochemical studies of this organism.     

Changes in antibiotic sensitivity in strains of Staphylococcus aureus, 1952-78.

Two hundred strains of Staphylococcus aureus isolated from outpatients with infections of the skin and subcutaneous tissues were tested for sensitivity to penicillin, erythromycin, tetracycline, sodium fusidate, methicillin, clindamycin, chloramphenicol, and gentamicin. One hundred and sixty-three (81.5%) of the strains were resistant to penicillin and 16 (8%) resistant to tetracycline. Incidence of resistance to other antibiotics was low. No strain was resistant to chloramphenicol, gentamicin, or methicillin. When compared with results of earlier studies, there was an increase in the incidence of resistance to penicillin and tetracycline, but no appreciable increase in resistance to other antibiotics.     

Long-term antibiotic susceptibility pattern of strains of Neisseria gonorrhoeae isolated in Czechoslovakia in the years 1957-1982

Over the past 25 years a total of 7492 strains of Neisseria gonorrhoeae have been isolated in Czechoslovakia, mainly in Prague (64%). All these strains have been tested for susceptibility to the following antibiotics: penicillin G, ampicillin, tetracycline, spectinomycin, erythromycin, doxycycline, kanamycin, rifampin, chloramphenicol, gentamicin, cephalothin, cephaloridine, lincomycin and clindamycin. In addition, seven derivatives of newer antibiotics of penicillin and cephalosporin series were tested in 1981. The study showed that in 1957 the MIC of 0.03 units of penicillin per ml was effective against 95% of strains, but in 1981 only 37% of isolates were sensitive to this concentration. The first gonococcal strains with the MIC value of 4.0 units/ml to penicillin were detected in 1981. This tendency towards decreased gonococcal susceptibility to benzylpenicillin is alarming. Over the last eight years there have been described sporadic isolations of strains relatively resistant to tetracycline (MIC = 8.0 mg/l). The susceptibility to spectinomycin has been tested in over 4000 gonococcal strains, since 1967. The test showed that this antibiotic remained highly effective against the gonococcal infection with over 95% of gonococci with the MIC value of 16.0 mg/l. No fully spectinomycin resistant strains have been found. Penicillin G as well as spectinomycin and cefotaxim are still considered the antibiotics of the first choice in the treatment of gonorrhoea. The alternative antibiotics may include cefuroxim, chloramphenicol and, in cases of sensitive strains, tetracyclines.     

Phenotypic Suppression in Escherichia coli by Chloramphenicol and Other Reversible Inhibitors of the Ribosome

Antibiotics that interfere reversibly with various aspects of ribosomal function (chloramphenicol, tetracycline, erythromycin, and spectinomycin) are shown to antagonize, at barely inhibitory concentrations, the inhibitory effect of low concentrations of streptomycin (SM) on the growth of Escherichia coli. Paradoxically, these compounds can also replace SM in supporting the growth of conditionally SM-dependent mutants. Chloramphenicol produced about as much phenotypic suppression as SM in SM-sensitive strains, but less than that attainable with high concentrations of SM in resistant strains. The antagonism to SM inhibition and the phenotypic suppression appear to be specific for those growth inhibitors that act on the ribosome. Since inhibitors of the 50S subunit of the ribosome (chloramphenicol, erythromycin) are as active as inhibitors of the 30S subunit, it is suggested that phenotypic suppression by borderline concentrations of ribosome inhibitors does not necessarily depend on an alteration of the recognition region of the ribosome. Alternatively, partial inhibition of the ribosomes might change the environment in a way that would influence the frequency of misreading. Phenotypic suppression by a low concentration of SM as well as by chloramphenicol was found to depend on the presence of a trace of the required growth factor.     

Identifi cation of antibiotics that are effective 2 in eliminatingAgrobacterium tumefaciens

An assay was performed to identify the antibiotics that are most effective againstAgrobacterium tumefaciens strains EHA101 and LBA4404, and to determine if these antibiotics inhibited tobacco callus and shoot formation. We tested ten antibiotics: cefotaxime, carbenecillin, erythromycin, spectinomycin, polymixin B, chloramphenicol, methicillin, Augmentin 500, Augmentin 250, and moxalactam. The effectiveness of each antibiotic against the two strains was determined by measuring the zones of inhibition of bacterial growth in a disk-diffusion assay. The five antibiotics that generated the largest zones of inhibition for each strain were assayed to determine their effects on callus formation. Cefotaxime was the most active antibiotic tested against strain LBA4404, and moxalactam was the most effective antibiotic against EHA101. Both cefotaxime and moxalactam had little or no effect on callus development.     

Study of the sensitivity of the L-forms of group A Streptococcus to antibiotics in artificial nutrient media and in human cell cultures

Sensitivity of L-forms of group A streptococci to 5 antibiotics such as erythromycin, lincomycin, tetracycline, gentamicin and chloramphenicol was studied in an artificial nutrient medium and cell cultures i.e. human fibroblast diploid cells and transplantable human heart cells (Girardi). In vitro investigation of the antibiotic effect on the streptococcal L-forms revealed their sensitivity to erythromycin (MIC, 0.4 micrograms/ml), lincomycin (MIC, 0.08 microgram/ml) and tetracycline (MIC, 2 micrograms/ml). The streptococcal L-forms were slightly sensitive to gentamicin (MIC, 6 micrograms/ml) and chloramphenicol (MIC, 30 micrograms/ml). Complete inhibition of the growth of the L-forms in the Girardi cells on the 1st day of the experiment after the antibiotics administration in single doses was induced by lincomycin, 5 micrograms/ml, erythromycin, 10 micrograms/ml, and tetracycline, 100 micrograms/ml. In the diploid cells, the respective figures were 50, 100 and 200 micrograms/ml. Chloramphenicol and gentamicin had an inhibitory effect on the growth of the L-forms but produced no sanative effect.     

Genetic Mapping of Linked Antibiotic Resistance Loci in Neisseria gonorrhoeae

Loci for resistance to several antibiotics in laboratory-derived strains of Neisseria gonorrhoeae were mapped by genetic transformation. Genes for high-level resistance to streptomycin (str) and spectinomycin (spc) and for low-level resistance to tetracycline (tet) and chloramphenicol (chl) were linked. Also, a locus for high-level resistance to rifampin (rif) was linked to str and tet. The apparent order was rif... str... tet... chl... spc. Loci for resistance to other antibiotics (penicillin, erythromycin) were transferred independently of each other and were not linked to the cluster around str. Similar linkage relationships were found with str, tet, chl, and spc loci obtained from naturally occurring (clinical) isolates of N. gonorrhoeae.     

支原体对抗生素的体外敏感性研究

目的研究非淋菌性尿道(宫颈)炎(NGU)患者支原体对12种抗生素敏感性,指导临床治疗。方法男性标本取尿道拭子．女性标本取宫颈拭子,采用支原体培养鉴定及药敏试剂盒进行体外药敏测定。结果126株解脲支原体(Uu)对12种抗生素敏感性从高至低依次为交沙霉素、强力霉素、美满霉素、克拉霉素、四环素、阿奇霉素、罗红霉素、司帕沙星、甲砜霉素、红霉素、可乐必妥和壮观霉素。12株人型支原体(Mh)对12种抗生素敏感性从高至低依次为交沙霉素、强力霉素、美满霉素、司帕沙星、四环素、壮观霉素、可乐必妥、甲砜霉素、红霉素、阿奇霉素、克拉霉素和罗红霉素。结论支原体耐药情况相当普遍。Uu、Mh对相同抗生素具有不同的敏感性。治疗时可依据药敏结果选择用药。     

Effect of hydroacridine derivatives on the sensitivity of polyresistant strains of Staphylococcus aureus and Escherichia coli to antibiotics]

Sensitivity of 4 clinical strains of Staph. aureus and E. coli to 13 hydroacridine derivatives and their combinations with antibiotics, such as benzylpenicillin, ampicillin, semi-synthetic penicillins, streptomycin, chloramphenicol, tetracycline, chlortetracycline, monomycin, oleandomycin and erythromycin was studied. The highest bacteriostatic effect was observed on the use of perhydroactidine derivatives with benzylpenicillin or ampicillin with respect to polyresistant penicillinase-producing strains of Staph. aureus, resistance of which to these antibiotics was decreased 250--1000 times. Under the effect of the above compounds the staphylococcal resistance to chloramphenicol, tetracycline, chlortetracycline, oleandomycine and erythromycin decreased 2--66 times. The combinations of hydroacridine with the antibiotics, except 10-amino-trans-syn-trans-perhydroacridine had no effect on the resistance of the E. coli strains. The results of the combined effect of the above substances were associated with their chemical nature, the bacterial type and possibly the character of the strain resistance.     

Increased sensitivity to protein synthesis inhibitors in cells lacking tmRNA.

tmRNA (also known as SsrA or 10Sa RNA) is involved in a trans-translation reaction that contributes to the recycling of stalled ribosomes at the 3' end of an mRNA lacking a stop codon or at an internal mRNA cluster of rare codons. Inactivation of the ssrA gene in most bacteria results in viable cells bearing subtle phenotypes, such as temperature-sensitive growth. Herein, we report on the functional characterization of the ssrA gene in the cyanobacterium Synechocystis sp. strain PCC6803. Deletion of the ssrA gene in Synechocystis resulted in viable cells with a growth rate identical to wild-type cells. However, null ssrA cells (deltassrA) were not viable in the presence of the protein synthesis inhibitors chloramphenicol, lincomycin, spiramycin, tylosin, erythromycin, and spectinomycin at low doses that do not significantly affect the growth of wild-type cells. Sensitivity of deltassrA cells similar to wild-type cells was observed with kasugamycin, fusidic acid, thiostrepton, and puromycin. Antibiotics unrelated to protein synthesis, such as ampicillin or rifampicin, had no differential effect on the deltassrA strain. Furthermore, deletion of the ssrA gene is sufficient to impair global protein synthesis when chloramphenicol is added at sublethal concentrations for the wild-type strain. These results indicate that ribosomes stalled by some protein synthesis inhibitors can be recycled by tmRNA. In addition, this suggests that the first elongation cycle with tmRNA, which incorporates a noncoded alanine on the growing peptide chain, may have mechanistic differences with the normal elongation cycles that bypasses the block produced by these specific antibiotics. tmRNA inactivation could be an useful therapeutic target to increase the sensitivity of pathogenic bacteria against antibiotics.     

Psychiatric care and politics.

The minimum inhibitory concentrations (MIC''s) of penicillin, ampicillin, tetracycline, erythromycin, spectinomycin and sulfadiazine were determined for 732 isolates of Neisseria gonorrhoeae collected in 1973-74. Comparison of the results of this survey with data from other Canadian studies showed that the percentage of isolates resistant to tetracycline had not changed since 1966, but that the percentage of erythromycin-resistant isolates had decreased. After an initial increase in 1966 the percentage of penicillin-resistant isolates stabilized. Spectinomycin-resistant isolates were not found. Positive correlations were observed between the MICs of the antibiotics tested; the highest positive correlations were between penicillin and ampicillin and between penicillin and tetracycline. A positive correlation was also noted between penicillin resistance and increasing spectinomycin MICs. Finally, a significant seasonal variation in MICs was found, the trend being towards increasing MICs during the summer.     

Effect of viomycin on dihydrostreptomycin binding to bacterial ribosomes.

Viomycin, a peptide antibiotic, reduced the amounts of dihydrostreptomycin bound to ribosomes of Myobacterium smegmatis and Escherichia coli, although they have different modes of action. The [3H]dihydrostreptomycin binding to ribosomes could not exchanged with streptomycin or dihydrostreptomycin, but not with unrelated antibiotics, namely, kanamycin, neomycin, spectinomycin, capreomycin, tuberactinomycin-N, chloramphenicol and erythromycin. We suggest that there is a significant interaction between the binding sites of viomycin and streptomycin on ribosomes.     

Studies of two strains of Actinopolyspora halophila,an extremely halophilic actinomycete

Actinopolyspora halophila is an extremely halophilic actinomycete requiring a minimum salt concentration of 12% (w/v) for growth in liquid media at 37°C. During antibiotic sensitivity testing of the organism, an erythromycin-resistant phenotypic variant designated A. halophila ER, was isolated. This strain was approximately 60-fold more resistant to erythromycin than the wild-type strain, and, moreover, was capable of growth in 6% sodium chloride. Optimal growth of both strains in liquid media was observed in 20% salt.After resuspension in water for up to 20 days, the organism exhibited good growth in fresh salt-containing media. Cultures resuspended in salt-containing media, however, were subject to extensive cellular autolysis.In addition to resistance to -lactam antibiotics which was mediated by cellular and exocellular -lactamases, the organism was insensitive to all other tested antibiotics except amakacin, chloramphenicol, kanamycin, gentamycin, naladixic acid, streptomycin, and tetracycline. No plasmids were detected in either strain. A. halophila possessed high cellular levels of catalase, -lactamase, and -glucosidase. A variety of exocellular enzymes including protease, -lactamase, xylanase, and carboxymethyl cellulase, were secreted maximally into growth media containing 15% NaCl.Issued as NRCC 25148     

Sensitivity of 56 strains of Streptococcus group B to 12 antibiotics: its determination by dilution and diffusion in agar

Sensitivity of 56 streptococcal strains of group B to 12 antibiotics was studied with the method of dilution in a special solid medium for cultivation of streptococci and with the method of agar diffusion in the same medium. All the strains were found to be sensitive to chloramphenicol, ristomycin and erythromycin. The predominating majority of the strains were sensitive to beta-lactam antibiotics and lincomycin. All the strains were resistant to aminoglycoside antibiotics, such as streptomycin and gentamicin. More than 85 per cent of the strains were resistant to tetracycline. Strains with multiple resistance to 2-7 antibiotics were detected. Satisfactory correlation between the two methods was observed. It was shown to be clinically advisable to determine the sensitivity of streptococci of group B to beta-lactam antibiotics, erythromycin and lincomycin.     

Effects of some antibiotics on the stringent control of RNA synthesis in Escherichia coli.

Effects of neomycin, spectinomycin, tetracycline and chloramphenicol on the stringent control RNA synthesis and on ppGpp synthesis in the rel+-cells of Escherichia coli having a temperature-sensitive valyl-tRNA synthetase were examined. Without antibiotics, ppGpp began to accumulate and both RNA and protein syntheses were inhibited by transferring the exponentially growing cells from 30 degrees C (permissive temp.) to 40 degrees C (non-permissive temp.). Tetracycline or chloramphenicol, when added after the temperature shift, caused a resumption of RNA synthesis and decay of the accumulated ppGpp, while neomycin or spectinomycin had little effect both on RNA synthesis and the level of ppGpp. When the cells were treated with these antibiotics at permissive temperature, the shift of the temperature to 40 degrees C caused neither inhibition of RNA synthesis nor an accumulation of ppGpp. When neomycin or spectinomycin was added at the beginning of the temperature shift, RNA synthesis continued with an accumulation of ppGpp. Tetracycline or chloramphenicol had no such effect under the same conditions; RNA synthesis continued without an accumulation of ppGpp.     

Effect of antibiotics on growth and laccase production from Cyathus bulleri and Pycnoporus cinnabarinus

The effect of nine different antibiotics (chloramphenicol, ampicillin trihydrate, kanamycin A monosulfate, neomycin sulfate, erythromycin, thiostrepton, tetracycline, apramycin sulfate and streptomycin sulfate) on growth and laccase production from Cyathus bulleri and Pycnoporus cinnabarinus has been investigated. All the antibiotics tested at a concentration of 200 mg/l affected the fungal growth, release of protein and laccase production to different extent. Inhibition in fungal growth was found to be positively correlated with increase in laccase production. Interestingly, apramycin sulfate inhibited biomass production (14.9-26.2%), nevertheless, it stimulated maximum laccase production (18.2 U/ml) in both the fungi. Increasing concentrations of apramycin sulfate enhanced laccase production from P. cinnabarinus but not from C. bulleri.     

Conformational changes in the ribosome induced by translational miscoding agents

Ribosomes are dynamic complexes responsible for translating the genetic information encoded in mRNAs to proteins. The accuracy of this process is vital to the survival of an organism, and is often compromised by translational miscoding agents. Aminoglycosides are a group of miscoding agents that bind to the ribosome and reduce the fidelity of translation. Previous studies have shown that aminoglycosides alter the higher order structure of the ribosome. Here, we used a toeprinting assay to how that streptomycin, neomycin, kanamycin, gentamycin, and hygromycin B trigger conformational changes within Escherichia coli ribosome. Miscoding agents viomycin and 30% ethanol also cause similar structural changes within the ribosome. In contrast, antibiotics that do not cause miscoding, such as tetracycline, chloramphenicol, erythromycin, fusidic acid and spectinomycin, do not induce the conformational changes triggered by miscoding agents. Furthermore, ribosomes isolated from strains that are either streptomycin resistant or dependent for growth do not show these conformational changes in the presence of streptomycin. These results correlate structural changes in the ribosome induced by miscoding agents in vitro with their in vivo phenotype.     

Specificity and mechanism of tetracycline resistance in a multiple drug resistant strain of Escherichia coli

Izaki, Kazuo (University of Tokyo, Tokyo, Japan), Kan Kiuchi, and Kei Arima. Specificity and mechanism of tetracycline resistance in a multiple drug resistant strain of Escherichia coli. J. Bacteriol. 91:628-633. 1966.-A decrease in the uptake of tetracycline occurred concurrently with a rise in the level of resistance of a multiple drug resistant strain of Escherichia coli grown in the presence of tetracycline. Although the strain was also resistant to streptomycin and chloramphenicol, growth in the presence of these two antibiotics did not influence the uptake of tetracycline. The induction of resistance, or decreased uptake of tetracycline, was dependent on growth of the organism in the presence of the drug. Decreased uptake of tetracycline could not be induced in a sensitive strain of the same organism under conditions suitable for induction of the resistant strain. The decrease in accumulating power of the resistant organism cultured in the presence of tetracycline does not appear to be due to selection of a resistant strain from cultures containing both resistant and sensitive strains.