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At least 811 records · Page 45Linked to original sources
PubMed1973

R-factor-mediated resistance to tetracycline in Proteus mirabilis.

The expression of R-factor-mediated resistance to tetracycline has been compared in Proteus mirabilis and Escherichia coli. Resistance to a range of concentrations of tetracycline was significantly lower in P. mirabilis than in E. coli in both induced and repressed states. Indirect evidence showed that conditions which result in a marked increase in the level of resistance of P. mirabilis harboring the R factor NR1 to chloramphenicol, streptomycin, and spectinomycin due to an amplification in the number of copies of r-determinants per cell do not detectably increase the level of resistance to tetracycline. Tetracycline resistance was inducible in early stationary-phase P. mirabilis NR1 although not after 5 h in this state. Double isotope labeling of control and tetracycline-induced P. mirabilis NR1 in early stationary phase revealed isotopic enrichment of certain peaks in extracts from induced cells subjected to polyacrylamide gel electrophoresis.

Acetyltransferases↗
PubMed1974

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.

Anti-Bacterial Agents↗
PubMed1977

Generation of miniplasmids from copy number mutants of the R plasmid NR1.

Small, closed circular deoxyribonucleic acid molecules, called miniplasmids, were observed in Escherichia coli harboring copy number mutants of the R plasmid NR1 after growth in medium containing tetracycline. The level of tetracycline resistance conferred by the copy mutant plasmids was lower (3 to 6 microgram/ml) than that conferred by NR1 (100 MICROGRAM/ML). The presence of the miniplasmid enhanced the level of tetracycline resistance conferred by the copy mutant. Miniplasmids of molecular weights 4 X 10(6) to 13 X 10(6) were found. They carried no antibiotic resistance markers and could be eliminated by growth in the presence of chloramphenicol and/or streptomycin-spectinomycin. Studies with the restriction endonucleases EcoRI and Sal I indicated that the miniplasmids are derived from the region of the copy mutant plasmids that contains the origin for replication of the resistance transfer factor. There were approximately 12 copies of the miniplasmid per chromosome, compared with 3 and 6 copies of the copy mutants of NR1. The miniplasmids appeared to be incompatible with the copy mutant plasmids.

Chloramphenicol↗
PubMed1978

Construction and characterization of amplifiable multicopy DNA cloning vehicles derived from the P15A cryptic miniplasmid.

Construction and characterization of a class of multicopy plasmid cloning vehicles containing the replication system of miniplasmid P15A are described. The constructed plasmids have cleavage sites within antibiotic resistance genes for a variety of commonly employed site-specific endonucleases, permitting convenient use of the insertional inactivation procedure for the selection of clones that contain hybrid DNA molecules. Although the constructed plasmids showed DNA sequence homology with the ColE1 plasmid within the replication region, were amplifiable by chloramphenicol or spectinomycin, required DNA polymerase I for replication, and shared other replication properties with ColE1, they were nevertheless compatible with ColE1. P15A-derived plasmids were not self-transmissible and were mobilized poorly by Hfr strains; however, mobilization was complemented by the presence of a ColE1 plasmid within the same cell.

Chloramphenicol↗
PubMed1980

Outer membrane-dependent transport systems in Escherichia coli: effect of repression or cessation of colicin receptor synthesis on colicin receptor activities.

Proteins in the outer membrane of gram-negative bacteria serve as general porins or as receptors for specific nutrient transport systems. Many of these proteins are also used as receptors initiating the processes of colicin or phage binding and uptake. The functional activities of several outer membrane proteins in Escherichia coli K-12 were followed after cessation or repression of their synthesis. Cessation of receptor synthesis was accomplished with a thermolabile suppressor activity acting on amber mutations in btuB (encoding the receptor for vitamin B(12), the E colicins, and phage BF23) and in fepA (encoding the receptor for ferric enterochelin and colicins B and D). After cessation of receptor synthesis, cells rapidly became insensitive to the colicins using that receptor. Treatment with spectinomycin or rifampin blocked appearance of insensitive cells and even increased susceptibility to colicin E1. Insensitivity to phage BF23 appeared only after a lag of about one division time, and the receptors remained functional for B(12) uptake throughout. Therefore, possession of receptor is insufficient for colicin sensitivity, and some interaction of receptor with subsequent uptake components is indicated. Another example of physiological alteration of colicin sensitivity is the protection against many of the tonB-dependent colicins afforded by provision of iron-supplying siderophores. The rate of acquisition of this nonspecific protection was found to be consistent with the repression of receptor synthesis, rather than through direct and immediate effects on the tonB product or other components of colicin uptake or action.

Colicins↗
PubMed1982

A chromosomally located transposon in Pseudomonas aeruginosa.

A new transposon, Tn2521, coding for carbenicillin, streptomycin, spectinomycin, and sulfanilamide resistance, has been identified in Pseudomonas aeruginosa. The transposon occurs naturally in the chromosome of clinical strains of P. aeruginosa isolated in geographically separated hospitals. This has been demonstrated by its transductional linkage to the pur-136 marker and also by Southern hybridization. Tn2521 is 6.8 kilobases, can transpose from the chromosome to both IncP-1 and IncP-2 plasmid genomes, and has a pattern of restriction endonuclease sites unlike that of any previously described transposon. The carbenicillin resistance carried by Tn2521 is due to the PSE-4 type of beta-lactamase.

Anti-Bacterial Agents↗
PubMed1985

Phasmid vectors for identification of genes by complementation of Escherichia coli mutants.

A bacteriophage lambda cloning vector was designed to facilitate the isolation of genes from procaryotic organisms by complementation of Escherichia coli mutants. This vector, lambda SE4, was constructed by attaching a very-low-copy-number replication system (from the plasmid NR1) and a spectinomycin resistance gene to the left arm of lambda 1059 (Karn et al., Proc. Natl. Acad. Sci. U.S.A. 77:5172-5176, 1980). This phasmid cloning vector is capable of growing lytically as a phage in a nonimmune host or lysogenically as a phasmid in an immune host. This phasmid utilizes the Spi- selection for insertions of DNA into the vector and has the ability to accept 2- to 19-kilobase Sau3A1, BamHI, BglII, BclI, or XhoII fragments; recombinants lysogenize immune hosts as single-copy-number selectable plasmids at 100% frequency. An E. coli library was constructed by using the initial vector lambda SE4, and clones of a number of representative genes were identified. A typical clone, lambda ant+, was shown to be readily mutagenized by a mini-Tn10 transposon. A general method for transferring cloned DNA segments onto bacteriophage lambda was developed. The method involves the use of in vivo recombination with a selection and was used to construct two derivatives of lambda SE4. Possible uses of these vectors and of the method for transferring cloned DNA onto phage lambda are discussed.

Bacteriophage lambda↗
PubMed1990

Purification, characterization, and in vivo reconstitution of Klebsiella aerogenes urease apoenzyme.

Urease was purified from recombinant Klebsiella aerogenes which was grown in the absence of nickel. The protein was inactive and contained no transition metals, yet it possessed the same heteropolymeric structure as native enzyme, demonstrating that Ni is not required for intersubunit association. Ni did, however, substantially increase the stability of the intact metalloprotein (Tm = 79 degrees C) compared with apoenzyme (Tm = 62 degrees C), as revealed by differential scanning calorimetric analysis. An increased number of histidine residues were accessible to diethyl pyrocarbonate in apourease compared with holoenzyme, consistent with possible Ni ligation by histidinyl residues. Addition of Ni to purified apourease did not yield active enzyme; however, urease apoenzyme was very slowly activated in vivo by addition of Ni ions to Ni-free cell cultures, even after treatment of the cells with spectinomycin to inhibit protein synthesis. In contrast, sonicated cells and cells treated with dinitrophenol or dicyclohexylcarbodiimide were incapable of activating apourease. These results indicate that apourease activation is an energy-dependent process that is destroyed by cell disruption.

Apoenzymes↗
PubMed1991

Site-specific insertion of three structural gene cassettes in transposon Tn7.

Transposon Tn7 has been known to carry genes for resistance to trimethoprim and spectinomycin. A poorly expressed streptothricin resistance gene, identical to the sat gene found in transposons Tn1825 and Tn1826, was localized between the two mentioned genes in Tn7. The surroundings of all three resistance genes indicated site-specific insertion of genetic cassettes.

Amino Acid Sequence↗
PubMed1995

Growth properties associated with A-U replacement of specific G-C base pairs in 16S rRNA from Escherichia coli.

Mutations that disrupt each of seven specific G-C base pairs in 16S rRNA from Escherichia coli confer loss of expression of a plasmid-encoded 16S rRNA selectable marker (spectinomycin resistance). However, A-U replacement of G-C base pairs at nucleotides 359/52 or 1292/1245 in 16S rRNA permits normal expression of the marker. By contrast, A-U replacements at 146/176, 153/168, 350/339, or 1293/1244 are associated with loss of expression of the marker. These genetic studies are designed to determine the importance of specific base pairs by assessment of the structural and functional impairments of 16S rRNA molecules resulting from expression of base pair substitutions at these positions.

Ampicillin↗
PubMed2003

Substrate specificity classes and the recognition signal for Salmonella type III flagellar export.

Most flagellar proteins of Salmonella are exported to their assembly destination via a specialized apparatus. This apparatus is a member of the type III superfamily, which is widely used for secretion of virulence factors by pathogenic bacteria. Extensive studies have been carried out on the export of several of the flagellar proteins, most notably the hook protein (FlgE), the hook-capping protein (FlgD), and the filament protein flagellin (FliC). This has led to the concept of two export specificity classes, the rod/hook type and the filament type. However, little direct experimental evidence has been available on the export properties of the basal-body rod proteins (FlgB, FlgC, FlgF, and FlgG), the putative MS ring-rod junction protein (FliE), or the muramidase and putative rod-capping protein (FlgJ). In this study, we have measured the amounts of these proteins exported before and after hook completion. Their amounts in the culture supernatant from a flgE mutant (which is still at the hook-type specificity stage) were much higher than those from a flgK mutant (which has advanced to the filament-type specificity stage), placing them in the same class as the hook-type proteins. Overproduction of FliE, FlgB, FlgC, FlgF, FlgG, or FlgJ caused inhibition of the motility of wild-type cells and inhibition of the export of the hook-capping protein FlgD. We also examined the question of whether export and translation are linked and found that all substrates tested could be exported after protein synthesis had been blocked by spectinomycin or chloramphenicol. We conclude that the amino acid sequence of these proteins suffices to mediate their recognition and export.

Bacterial Outer Membrane Proteins↗
PubMed1996

Moredun Bordetella Medium, an improved selective medium for isolation of Bordetella parapertussis.

Bordetella parapertussis, previously thought to be an obligate human respiratory tract pathogen, has been isolated from sheep. Attempts to assess the prevalence of B. parapertussis in conventionally reared sheep by nasal swabbing proved futile with existing selective media because of extensive overgrowth with Mucor spp. and other nasal commensals. Moredun Bordetella Medium (MBM), which contains cycloheximide and spectinomycin at final concentrations of 0.5 mg/ml and 100 mu g/ml, respectively, was developed as an improved selective medium to isolate B. parapertussis from the nasal cavities of conventionally reared sheep. The selective ability of MBM was evaluated with 200 nasal swabs from conventionally reared sheep, and B. parapertussis was recovered from 31.5% of the samples. MBM facilitated the simple and effective isolation of B. parapertussis from ovine nasal swabs and, in successfully excluding overgrowth with other contaminants, proved superior to other test formulations evaluated and to existing conventional media.

Bordetella↗
PubMed1975

Antibiotic susceptibility of Neisseria gonorrhoeae isolated in the Western Pacific in 1971.

Isolates of Neisseria gonorrhoeae from 256 patients contracting acute gonococcal urethritis, primarily in the Republic of the Phillipine Islands, in 1971, were tested for the minimum inhibitory concentrations of five antibodies. The median is advocated as a measurement for comparison of ranges of MIC values; the median MIC of penicillin for 258 isolates was 0-23 mug/ml. A positive correlation coefficient was observed for the susceptibility of isolates to penicillin, spectinomycin, cephaloridine, and tetracycline.

Anti-Bacterial Agents↗
PubMed1975

Activity of eight antimicrobial agents in vitro against N. Gonorrhoeae.

The sensitivity of four groups of gonococcal strains to ampicillin (Am), penicillin (P), tetracycline (T), rifampicin (Ri), spectinomycin (Sp), sulphamethoxazole (Su), trimethoprim (Tr), and a combination of Su and Tr in the ratio 5:1 (Su/Tr 5:1) has been determined. The various groups of strains were isolated from male civilians (MC), female civilians (FC), and sailors (S) in Rotterdam (R) in 1972, and from FC in Amsterdam (A) in 1967. The S-R strains, which may be regarded as mainly imported, were compared with the MC-R and FC-R (which may be considered as mainly of Dutch origin). Also investigated was whether the incidence of relative resistance to the antibiotics investigated among Dutch strains has changed in the period from 1967 to 1972. For this purpose, the FC-A and FC-R strains were compared. The MC-R and FC-R strains were also compared with one another. Finally, Spearman's rank correlation coefficient r were calculated between the sensitivity distributions for each pair of antibiotics investigated, for all strains. The S-R strains were significantly less sensitive to Am, P, T, Ri, and Tr than the MC-R and FC-R strains. Comparison of the FC-A and FC-R strains revealed that the FC-R strains were significantly less sensitive only to Su/Tr 5:1. A possible explanation for this finding is given. With the exception of one FC-A strain, all gonococcal strains were sensitive to Sp. High values of r (larger than or equal to 0.50) were found between Am and P, Am and T, and P and T for all groups of strains. The values of r between any pair of the antibiotics Am, P, T, Ri, and Tr (with the exception of the pair Am-P) were always highest for the S-R strains. High values of r (larger than or equal to 0.50) were found between Su and Su/Tr 5:1 for all groups of strains. The FC-A strains, unlike the R strains, gave low values of r between Su and Tr and between Tr and Su/Tr 5:1. A possible explanation for this is given. Finally, a hypothesis is put forward to explain the fact that no significant changes were found in the sensitivity of Dutch gonococcal strains to Am, P, T, Ri, Sp, Su, and Tr in the period from 1967 to 1972, while the S strains (which may be regarded as imported) showed a significantly higher percentage of strains relatively resistant to Am, P, T, Ri, and Tr.

Ampicillin↗
PubMed1978

Chlamydia trachomatis in gonococcal and postgonococcal urethritis.

Chlamydia trachomatis was isolated from the urethra of 38 (28.6%) out of 133 men with gonococcal urethritis (GU). During the follow up of 72 men postgonococcal urethritis (PGU) was diagnosed in 50 (69.5%) patients. More than half (30 out of 50) of these patients with PGU were Chlamydia-positive. Out of 31 patients with Chlamydia 30 developed PGU whether or not procaine penicillin, spectinomycin, or gentamicin were used. These findings are discussed in relation to present recommendations for the treatment and follow up of patients with GU.

Adult↗
PubMed1980

Rectal gonorrhoea in male homosexuals. Presentation and therapy.

In a review of rectal gonorrhoea 73 episodes were studied in 65 homosexual men. The presenting signs and symptoms were carefully noted. Treatment with a single injection of spectinomycin hydrochloride 2 g resulted in a cure rate of 94.5%. The relatively high treatment failure rate associated with rectal gonorrhoea may possibly be due to microbial mechanisms.

Adolescent↗
PubMed1983

Epidemiology and treatment of gonorrhoea caused by penicillinase-producing strains of Neisseria gonorrhoeae in Fukuoka, Japan.

Thirty strains of penicillinase-producing Neisseria gonorrhoeae (PPNG) were detected by a rapid iodometric method out of 206 strains isolated from patients with gonorrhoea between January and December 1981. Of the 30 patients, five of the nine women were prostitutes and 14 of the 21 men were infected by prostitutes in or around Fukuoka City, with the exception of one who was infected in Formosa. Treatment with ampicillin or amoxycillin resulted in failure whereas treatment with spectinomycin was successful.

Adolescent↗
PubMed1986

In vitro antimicrobial sensitivity of Neisseria gonorrhoeae from Rwanda.

The in vitro sensitivity of 104 isolates of Neisseria gonorrhoeae to six antimicrobial agents was tested. More than 50% of the isolates produced penicillinase. Of those that did not produce penicillinase, 26% were resistant (minimum inhibitory concentration (MIC)) greater than or equal to 0.5 mg/l), and 68% showed a decreased sensitivity for penicillin G (0.06 less than or equal to MIC less than or equal to 0.25 mg/l). Twenty six per cent and 50% of the strains, respectively, showed a decreased sensitivity to thiamphenicol (MIC greater than or equal to 1 mg/l) and tetracycline (MIC greater than or equal to 2 mg/l). All isolates were sensitive to spectinomycin, kanamycin, and norfloxacin. Of 20 penicillinase producing N gonorrhoeae (PPNG) isolates examined, seven contained the 3.4 megadalton R-plasmid, another seven contained both the 3.4 megadalton and 22.5 megadalton plasmids, five the 4.3 megadalton and 22.5 megadalton plasmids, and one isolate harboured both the 3.4 and 4.3 R-plasmids, together with the 22.5 megadalton plasmid. A disturbing increase in resistance to penicillin has been observed since the publication of earlier surveys, and the clinical implications of these findings are discussed.

Anti-Bacterial Agents↗