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At least 937 records · Page 52Linked to original sources
PubMed1984

Characterization of aminoglycoside-lipid interactions and development of a refined model for ototoxicity testing.

Aminoglycoside interactions with various phospholipids were measured in three model systems and compared with the ototoxicities of the drugs: (a) competition for [14C]neomycin binding; (b) competition for 45Ca2+ binding; and (c) effect on surface pressure of monomolecular lipid films. The efficacies of the antibiotics in displacing neomycin from phosphatidylserine, phosphatidylinositol or phosphatidylinositol bisphosphate were netilmicin greater than neomycin greater than or equal to gentamicin; the efficacies in displacing calcium from phosphatidylinositol, phosphatidylinositol phosphate or phosphatidylinositol bisphosphate were netilmicin greater than gentamicin greater than neomycin much greater than kanamycin greater than spectinomycin. Neither measure correlated well with the ototoxicities of the drugs which were quantitated at equimolar drug concentrations in cochlear perfusions: neomycin greater than gentamicin greater than or equal to tobramycin greater than netilmicin greater than or equal to amikacin. When monomolecular films of phosphatidylcholine with phosphatidylserine, cardiolipin, phosphatidylinositol, or phosphatidylinositol phosphate or bisphosphate were challenged with neomycin, the phosphatidylinositol bisphosphate film showed a unique dose-dependent increase in surface pressure while the others showed a decrease or no significant effect. The abilities of aminoglycosides to increase the surface pressure of a film of phosphatidylcholine:phosphatidylinositol bisphosphate (1:1 molar ratio) in the presence of 3 mM CaCl2 correlated well with their toxicities. Non-ototoxic cations increased the film pressure or left it unaffected. The results confirm the unique interactions between aminoglycosides and phosphatidylinositol bisphosphate as a possible basis of a mechanism of toxicity and development of a drug-screening system.

Aminoglycosides↗
PubMedDate not supplied

Control of Campylobacter fetus in artificially contaminated bovine semen by incubation with antibiotics before freezing.

Fresh, diluted semen containing 1.55 X 10(6) cfu/ml of Campylobacter fetus subsp. venerealis was incubated with 500 iu of penicillin, 500 micrograms of streptomycin, 160 micrograms of lincomycin and 300 micrograms of spectinomycin per ml at 35 degrees C for 0, 1, 2, 5, 10, 20 or 40 minutes. The semen was cooled to 5 degrees C, packaged in 0.25 ml French straws and then frozen in liquid nitrogen for 2 weeks. Immediately after thawing and removal of the antibiotics by centrifugation semen samples from each of the seven treatment groups were cultured as for C. fetus. Semen samples were also examined by in-vitro tests for sperm motility prior to and post-freezing. Incubation with the antibiotics for 5, 10, 20 or 40 min prior to freezing reduced the numbers of C. fetus in the semen to non-detectable levels in 38%, 69%, 88% and 100% of samples respectively. The incubated semen showed no significant reduction of sperm motility although fertility trials have not been done.

Animals↗
PubMed1994

Autoregulation and kinetics of induction of the Rhizobium phaseoli recA gene.

A fusion between the recA gene of Rhizobium phaseoli and the lacZ gene was constructed in vitro and cloned in a mini-Tn5 transposon derivative to obtain chromosomal insertions which make it possible to quantitatively examine their transcriptional regulation in both R. phaseoli and E. coli. Likewise, and by insertion of a spectinomycin-resistance gene cassette into the recA gene of R. phaseoli and subsequent marker exchange, a RecA- derivative of this bacterial species has been obtained. Analysis of this recA-lacZ fusion showed that it was inducible by DNA damage in the RecA+ strain of R. phaseoli but not in the RecA- mutant. On the other hand, the recA-lacZ fusion of R. phaseoli was not induced in DNA-damaged RecA+ cells of E. coli. Furthermore, the range of UV doses which give rise to dose dependence in the induction of its respective recA genes is different in R. phaseoli from that in E. coli.

Cloning, Molecular↗
PubMed1981

A study of drug resistance among Salmonella typhi and Salmonella paratyphi A in an endemic area, 1977-79.

Tests for antibiotic resistance were carried out on 198 strains of Salmonella typhi and S. paratyphi A isolated from cases of enteric fevers. Their minimal inhibitory concentrations for streptomycin, chloramphenicol, ampicillin, furazolidine and co-trimoxazole were estimated by plate dilution technique. Four strains of S. typhi and one strain of S. paratyphi A were found to show multiple resistance with a set pattern of resistance to chloramphenicol, streptomycin, sulphonamide, tetracycline and spectinomycin. All the five strains carried R-factors. Three of the resistant S. typhi belonged to Phage type 'O' and one was in Phage type 'A'. The single resistant S. paratyphi A belonged to Phage type '2'.

Ampicillin↗
PubMed1983

Inhibition of Tn554 transposition: deletion analysis.

Tn554, a transposon in Staphylococcus aureus that specifies resistance to erythromycin and spectinomycin, exhibits a high preference for a single chromosomal insertion site. If this site is already occupied by a copy of Tn554, the transposition of a second element is inhibited 100- to 1000-fold. This report defines the locus of the inhibitory activity and presents both a functional and a restriction map of Tn554. Fragments containing parts of Tn554 were cloned on an autonomously replicating plasmid. Those clones containing the "left" end of Tn554 strongly inhibited the transposition of an incoming, intact copy of Tn554. Analysis of deleted derivatives of these clones defined a locus tnpI, which is both necessary and sufficient for transpositional inhibition. This locus consists of the terminal 89 bp of the "left" end of Tn554. It is suggested that this terminal sequence acts to titrate a factor required for transposition.

Cloning, Molecular↗
PubMed1986

Characterization of transferable plasmids from Shigella flexneri 2a that confer resistance to trimethoprim, streptomycin, and sulfonamides.

A set of plasmids conferring resistance to several antibiotics, including the combination of trimethoprim and sulfamethoxazole, has been isolated from Escherichia coli following conjugative cotransfer from a clinical isolate of Shigella flexneri 2a. One of the plasmids, pCN1, was shown by subcloning and DNA sequencing to carry a gene encoding a trimethoprim-insensitive dihydrofolate reductase identical to that found in E. coli transposon 7. This plasmid was also shown to confer resistance to both streptomycin and spectinomycin by production of an adenylyltransferase that inactivated the drugs and the gene encoding this enzyme has also been sequenced. A second plasmid from the set, pCN2, was shown to inactivate streptomycin by a phosphotransferase mechanism and also to confer resistance to sulfonamides. The third plasmid from the set could not be correlated with a drug-resistance phenotype, but does appear to play a crucial role in plasmid mobilization.

Base Sequence↗
PubMed1987

A low copy number cosmid.

A low copy number cosmid was constructed by subcloning the pair of cos sites and the kanamycin resistance gene of pcos2EMBL into pGB2. The resulting cosmid, pPR691, has the pSC101 replicon and specifies resistance to kanamycin, spectinomycin, and streptomycin. pPR691 also carries restriction sites suitable for cloning partial Sau3A digests using the strategy of Bates and Swift (P. F. Bates and R. A. Swift, 1983, Gene 26, 137-146). A library of Salmonella typhimurium chromosomal DNA was made using this cosmid and the rfb gene cluster (map position 42) was isolated from this library.

Cloning, Molecular↗
PubMed1987

Genetic analysis of the gentamicin resistance region of pPH1JI and incorporation into a wide host range cloning vehicle.

A region of the IncP plasmid pPH1JI encoding resistance to gentamicin, spectinomycin, and streptomycin was characterized by subcloning, deletion, and insertion mutagenesis. Approximate locations of these resistance determinants were established. A 1.6-kb HindIII-SphI segment of this region expresses gentamicin resistance (Gmr) in Escherichia coli when inserted into various plasmid vectors; this DNA segment encodes a polypeptide of 17.5 kDa. Incorporation of this fragment into an IncP cloning vehicle produced a Gmr wide host range vector, pRAR209, which confers levels of Gmr comparable to those expressed by pPH1JI in E. coli, Agrobacterium tumefaciens, and Rhizobium meliloti.

Cloning, Molecular↗
PubMed1988

The Salmonella wien virulence plasmid pZM3 carries Tn1935, a multiresistance transposon containing a composite IS1936-kanamycin resistance element.

Tn1935, a 23.5-kb transposon mediating resistance to ampicillin, kanamycin, mercury, spectinomycin, and sulfonamide was isolated from pZM3, an IncFIme virulence plasmid from Salmonella wien. Tn1935 possesses the entire sequence of Tn21 and contains two additional DNA segments of 0.95 and 2.7 kb carrying the ampicillin and kanamycin resistance genes, respectively. The latter is part of a composite element since it is flanked by two IS15-like insertion sequences (IS1936) in direct orientation. IS1936 is about 800 bp long and is closely related to IS15 delta, IS26, IS46, IS140, and IS176. Functional analysis of IS1936-mediated cointegrates shows that both insertion sequences are active and able to form cointegrates at the same frequency. Resolution of the cointegrates requires the presence of the host Rec system. The presence of the composite IS1936-element within Tn1935 supports the hypothesis that multidrug resistance transposons evolved by insertion of antibiotic determinants which are themselves transposable.

Anti-Bacterial Agents↗
PubMed1989

Tn4527, a Tp Sp/Sm transposon related to Tn7 and flanked by IS1.

Tn4527 was isolated from a Salmonella typhimurium strain obtained in Brazil. Its size is 19.6 kb and it carries resistance to trimethoprim, spectinomycin, and streptomycin, as in the case of Tn7 (14 kb). A restriction analysis of the transposon shows regions of similarity to Tn7 mixed with extra DNA. The 2.6-kb and 2.2-kb HindIII fragments of Tn7, which encode transposition-related proteins, show homology to Tn4527. In contrast to Tn7, Tn4527 is flanked by direct repeats, which seem to be IS1's, as they have appropriate restriction sites and hybridize both to IS1 and to internal IS1 oligonucleotides.

Anti-Bacterial Agents↗
PubMed1988

Antibiotic resistance of Escherichia coli strains isolated from chickens with colisepticaemia in Morocco.

Sixty-two strains of Escherichia coli were isolated in 58 farms from broiler chickens showing respiratory signs and lesions characteristic of avian colibacillosis. Serological examination of these strains showed that the types 078, 01 and 02 (for the somatic antigen) and K1 (for the capsular antigen) were the most frequently found. Newcastle disease virus was also isolated in two cases. All the strains of E. coli isolated were sensitive to colistin, flumequine and gentamicin. A few strains were resistant to neomycin, nalidixic acid and trimethoprim. The frequency of strains resistant to nitrofurans, sulfonamides, chloramphenicol, spectinomycin and ampicillin was intermediate. Most strains were resistant to tetracycline. Multiple resistance was common.

Animals↗
PubMed1990

Discrepancy between in vitro and in vivo assays for the susceptibility of Bacillus C.I.P. 5832 to antimicrobial agents.

In vitro, avoparcin, flavomycin, virginiamycin bacitracin, trimethoprim + sulfadimethoxine, colistin, spiramycin, oxolinic acid, lincomycin + spectinomycin and a mixture of organic acids were able to inhibit Bacillus C.I.P. 5832. In vivo, none of these antibacterial agents, at the levels incorporated in feeds, could affect the viable bacillus count in the caecal content of chickens. In another in vitro assay, olaquindox, carbadox and tylosin were also effective in inhibiting Bacillus C.I.P. 5832. But, concomitantly administered with carbadox or tylosin, Bacillus C.I.P. 5832 still promoted growth and feed conversion of fattening pigs. These results, as well as data of the quoted literature, suggest that the current in vitro techniques should not be used to screen the susceptibility of Bacillus C.I.P. 5832 to antimicrobial agents. Only in vivo assays seem to be of value.

Animals↗
PubMed1991

Evolution of Staphylococcus aureus resistance to erythromycin in Denmark, 1959 to 1988: comparison with erythromycin-susceptible strains.

Between 1959 and 1988, all Staphylococcus aureus strains (15 168 patients) isolated from blood in Denmark have been collected, investigated and stored, and clinical data has been obtained. Erythromycin resistance was found in 4.9% of these strains. The frequency of erythromycin resistance peaked at 25% in 1966, due to the spread in hospitals of multiresistant strains of the 83A complex. When these strains dominated, an increased mortality rate was seen in patients infected with erythromycin-resistant S. aureus. In contrast to most countries, erythromycin resistance in S. aureus declined to less than 5% in 1971, continued to fall to 1.3% in 1983, and has increased slowly to 2.4% in 1988. The decline was only due to a decrease of multiresistant strains. Erythromycin-resistant strains isolated in recent years are predominantly resistant only to penicillin and erythromycin and belong to many different phage type patterns. In Denmark, inducible resistance has occurred at a stable high frequency of approximately 90% of the erythromycin-resistant strains during the last 30 years. Erythromycin-resistant strains isolated today, however, have higher minimum inhibitory concentrations, and are rarely resistant to spectinomycin, in contrast to the strains isolated in the first half of the observation period.

Denmark↗
PubMed1987

Higher-order structure of domain III in Escherichia coli 16S ribosomal RNA, 30S subunit and 70S ribosome.

We have investigated in detail the conformation of domain III of 16S rRNA (nucleotides 913-1408), using a variety of chemical and enzymatic structure probes. The sites of reaction were identified by primer extension with reverse transcriptase using appropriate oligodeoxyribonucleotide primers. This study has been done on 16S rRNA in its naked form, in the 30S subunit and in the 70S ribosome. Data obtained with naked RNA broadly confirm the secondary structure model proposed essentially by comparative sequence analysis, and allow identification of nucleotides involved in tertiary interactions. Our results are in reasonably good agreement with structure probing experiments of Moazed et al. [1]. However, several discrepancies have been observed. Within the 30S subunit, a high number of nucleotides become unreactive whereas other nucleotides show an enhanced reactivity. This probably reflects local conformational changes. Interestingly, they are located in strategic regions of the RNA, e.g. around C1400 (involved in tRNA binding) and C1192 (involved in spectinomycin recognition). Results are also discussed together with the topographical localization of the ribosomal proteins in this area. The study on the 70S particle allows identification of regions at the interface of subunits or exposed at the surface of the ribosome.

Base Sequence↗
PubMed1991

Presence of a gene in the archaebacterium Methanococcus vannielii homologous to secY of eubacteria.

The nucleotide sequence of a gene located at the promoter-distal side of the 'spectinomycin-operon' homologue of the archaebacterium Methanococcus vannielii was determined. Its derived amino acid sequence displayed 20% (identical positions) or 52% (including conservative exchanges) similarity, respectively, to SECY from E coli. An alignment of the Methanococcus SECY with eubacterial SECY sequences showed the existence of 10 membrane-associated primary structure domains in equivalent positions. The 5' and 3' ends of the secY transcript were mapped and the gene was expressed in the T7 promoter/polymerase system in E col. The temperature-sensitive growth of the E coli mutant IQ292 which harbours a secYts mutation could be complemented by the secY gene from Methanococcus. This indicates that a protein integral to an archaebacterial ether-lipid membrane can be inserted into a eubacterial phospholipid membrane without apparent loss of function.

Amino Acid Sequence↗
PubMed1984

A pSC101-derived plasmid which shows no sequence homology to other commonly used cloning vectors.

We have constructed a plasmid cloning vector, pGB2, which is derived from the Escherichia coli plasmid pSC101. The plasmid, which specifies resistance to spectinomycin and streptomycin, contains unique restriction sites for the enzymes HindIII, PstI, SalI, BamHI, SmaI and EcoRI. pGB2 shows no sequence homology, as detected by DNA-DNA hybridization, to several widely used vectors such as pBR322, pUC8 and phage lambda L47.1. Amongst other applications, DNA fragments can be cloned into the plasmid and then radioactive plasmid DNA can be used as a probe to screen recombinant DNA libraries.

Animals↗
PubMed1992

TnblaM: a transposon for directly tagging bacterial genes encoding cell envelope and secreted proteins.

A transposon, TnblaM, designed for the direct selection of bacterial mutants with insertions in genes encoding cell envelope and secreted proteins, was constructed and subcloned into plasmid and bacteriophage lambda delivery vectors. TnblaM is a spectinomycin-resistant derivative of Tn5 with an unexpressed open reading frame encoding mature beta-lactamase (BlaM) at its left end. Therefore, when it inserts into genes in the correct orientation and reading frame, gene fusions encoding hybrid proteins are generated. By introducing TnblaM into bacterial cells and selecting ampicillin-resistant (ApR) colonies, the subset of isolates producing extracytoplasmic BlaM, and hence containing TnblaM inserted in genes encoding secreted proteins and cell envelope proteins, can be directly selected. TnblaM, like TnphoA, can therefore be used to preferentially mutagenise genes encoding extracytoplasmic proteins, but it has the advantage over TnphoA that the desired mutants can be isolated by direct selection (as ApR colonies) rather than by phenotypic screening. Isolates in which TnblaM occupies sites in the chromosome from which it can transpose at high frequency are readily identifiable, and constitute TnblaM donors, with which to simply and efficiently generate rare types of insertion mutants. Moreover, the ApR selection that is used with TnblaM can be fine-tuned to obtain blaM fusions to poorly or well-expressed genes.

Amino Acid Sequence↗
PubMed1993

Construction of new beta-glucuronidase cassettes for making transcriptional fusions and their use with new methods for allele replacement.

Five cassettes carrying uidA, encoding beta-glucuronidase, were made for the construction of insertion mutants with transcriptional fusions to uidA. Three uidA cassettes contain antibiotic-resistance genes, for chloramphenicol (Cm), for kanamycin (Km) and neomycin (Nm), or for streptomycin (Sm) and spectinomycin (Sp). Some cause polar insertions while others provide a promoter for downstream gene expression. The expression of these uidA cassettes was compared to the expression of lacZ at the same site in phnD, a phosphate-regulated gene for phosphonate use. Several phn::uidA or phn::lacZ insertions were recombined onto the chromosome to test mutational effects and to measure gene expression in single copy. This was done using one of three methods for allele replacement. A new method involved recombination of mutations in M13 onto the chromosome by infection of an Escherichia coli rep mutant that fails to propagate single-stranded DNA phages. Merodiploid recombinants were selected using a resistance marker carried by the M13 phage; segregants lacking M13 sequences were then selected as deoxycholate-resistant (DocR) ones. An improved method for recombination of mutations in pir-dependent, oriR6K vectors involved the use of plasmids containing genes for tetracycline resistance (TcR). Merodiploid recombinants were selected by conjugative transfer of such plasmids into a recipient lacking pir (encoding the pi protein of the R6K plasmid); segregants lacking vector sequences were subsequently selected as Tc-sensitive ones. Both procedures are efficient and allow for recombining marked as well as unmarked mutations onto the chromosome. In addition, some insertions with an antibiotic-resistance marker were directly recombined onto the chromosome by transformation of a recD mutant with linear DNA.(ABSTRACT TRUNCATED AT 250 WORDS)

Alleles↗