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PubMed1995

Antimicrobial sensitivity testing of Australian isolates of Bordetella avium and the Bordetella avium-like organism.

The in-vitro sensitivity of 16 Australian isolates of Bordetella avium and 15 isolates of B avium-like organism to 11 antimicrobial agents or combinations of agents was determined using a microtitre plate system to establish minimal inhibitory concentrations. All the B avium isolates were sensitive to ampicillin but resistant to erythromycin, lincomycin, spectinomycin, sulphamethoxazole, trimethoprim, and lincomycin + spectinomycin. Most of the B avium isolates were sensitive to tetracycline and resistant to streptomycin and sulphadiazine. All the B avium-like isolates were resistant to ampicillin, erythromycin, lincomycin, spectinomycin, streptomycin, tetracycline, trimethoprim, and lincomycin+spectinomycin. Most B avium-like isolates were sensitive to sulphadiazine, sulphamethoxazole and trimethoprim-sulphamethoxazole.

Animals↗

PubMed1992

Correlation between in vitro antimicrobial susceptibilities and beta-lactamase plasmid contents of isolates of Haemophilus ducreyi from the United States.

We determined the susceptibilities of 94 strains of Haemophilus ducreyi isolated in various municipalities in the United States between 1982 and 1989 to the following antimicrobial agents: amoxicillin-clavulanic acid, ceftriaxone, erythromycin, azithromycin, ciprofloxacin, ofloxacin, trimethoprim, and spectinomycin. Ceftriaxone (MIC, less than or equal to 0.008 micrograms/ml), azithromycin (MIC, less than or equal to 0.125 micrograms/ml), erythromycin (MIC, less than or equal to 0.125 micrograms/ml), ciprofloxacin (MIC, less than or equal to 0.25 micrograms/ml), and ofloxacin (MIC, less than or equal to 0.25 micrograms/ml) were highly active against all isolates. Amoxicillin-clavulanic acid (MICs, 0.25 to 8.0 micrograms/ml), trimethoprim (MICs, 0.06 to 16.0 micrograms/ml), and spectinomycin (MICs, 2.0 to greater than or equal to 32.0 micrograms/ml) were less active against these isolates. Isolates possessing the 5.7-MDa beta-lactamase plasmid were less susceptible to erythromycin, trimethoprim, and spectinomycin than were isolates possessing the 3.2-MDa beta-lactamase plasmid. The susceptibilities of plasmidless isolates to erythromycin, trimethoprim, and spectinomycin were distributed bimodally; the median MIC for the more susceptible plasmidless isolates corresponded to that for isolates with the 3.2-MDa plasmid, and the median MIC for the less susceptible plasmidless isolates corresponded to that for isolates with the 5.7-MDa plasmid. Thus, plasmid profiles may be valuable markers for geographical variations in antimicrobial susceptibilities of H. ducreyi strains that may indicate the relative efficacy of regimens for the treatment of chancroid. Of the regimens recommended by the U.S. Public Health Service for the treatment of chancroid, our results support the use of erythromycin, ceftriaxone, and ciprofloxacin, and perhaps ofloxacin, but suggest that amoxicillin-clavulanic acid and sulfamethoxazole-trimethoprim should be used with caution.

Anti-Bacterial Agents↗

PubMed1990

Influence of antibiotics on intestinal tract survival and translocation of environmental Pseudomonas species.

The environmental release of microorganisms has prompted the investigation of potential health effects associated with their release. In this study, survival and translocation to the spleen and liver of several environmental Pseudomonas spp. were investigated in antibiotic-treated mice. Pseudomonas aeruginosa BC16 and P. maltophilia BC6, isolated from a commercial product for polychlorinated biphenyl degradation; P. aeruginosa AC869, a 3,5-dichlorobenzoate degrader; and P. cepacia AC1100, an organism that metabolizes 2,4,5-trichlorophenoxyacetic acid were examined for their survival capabilities in the intestines of mice dosed with clindamycin, kanamycin, rifampin, or spectinomycin. A mouse intestinal isolate, strain PAMG, was included in the study. Following antibiotic pretreatment (1 mg twice daily for 3 days), mice were dosed by gavage with 10(9) CFU of each Pseudomonas strain. At the end of the 5-day test period, strains AC869 and PAMG survived in kanamycin-, rifampin-, spectinomycin-, and clindamycin-treated animals. A statistically significant (P less than 0.05) increase in survival of strain PAMG was observed in clindamycin-, kanamycin-, and spectinomycin-treated mice for the test period. Treatment with clindamycin or rifampin increased (P less than 0.05) survival of strain BC6, an organism resistant to both antibiotics. However, strain BC6 was detected only in rifampin-treated mice at the end of the 5-day test period. Strain BC16, a clindamycin-resistant strain, was detected in clindamycin-treated mice and the untreated control animals. Rifampin had a negative effect (P less than 0.05) on strain AC869 and PAMG survival. Translocation to the spleen was observed in spectinomycin- and clindamycin-treated mice but was not detected in kanamycin- or rifampin-treated animals.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1989

DNA amplification in Streptomyces achromogenes subsp. rubradiris is accompanied by a deletion, and the amplified sequences are conditionally stable and can be eliminated by two pathways.

Southern blot analysis of BglII-digested DNA isolated from wild-type Streptomyces achromogenes, which harbors the 8.8-kilobase amplifiable unit of DNA, AUD-Sar 1, and of similarly digested DNA from 12 strains carrying an array of 200 to 300 tandem copies of a specific AUD-Sar 1-derived 8.0-kilobase DNA sequence, ADS-Sar 1, revealed the absence of the 12.4-kilobase BglII AUD-Sar 1-chromosome right junction band in the latter strains, whereas the corresponding 26.0-kilobase left junction band remained unaltered. Further Southern analyses indicated in all of the seven amplified strains tested the occurrence of a deletion of at least 10 kilobases of the DNA adjacent to the right side of the AUD. The deletion has one endpoint in the vicinity of the ADS array. Corroborating and expanding upon previously reported results, we found that the amplified DNA of strain C010 was stably maintained for at least 20 transfers when the transfers involved mycelia propagated in spectinomycin-free liquid medium. In contrast, when strain C010 was subjected separately to one cycle of protoplast formation and regeneration or to three cycles of spore germination, aerial mycelium formation, and sporulation on spectinomycin-free media, only approximately 20% of the protoplast regenerants and spores retained the reiterated DNA sequences and the ability subsequently to form colonies on media containing high levels of spectinomycin. Approximately 80% of these units completely deleted the reiterated DNA and left adjacent sequences and exhibited sensitivity to 25 micrograms of spectinomycin per ml. One among 24 protoplast-derived deletants apparently retained the left portion of the AUD-ADS left direct repeat plus left adjacent sequences.

Blotting, Southern↗

PubMed1985

[Drug toxicity in piglets following long-term consumption of medicated feed].

The effect of the addition of various drugs to the feed on the performance of recent weaned piglets was studied. The following procedures were examined: no additive, 50 ppm of carbadox, 50 ppm of carbadox plus 400 ppm of furazolidone, 50 ppm of carbadox plus 22 ppm of lincomycin plus 22 ppm of spectinomycin, 400 ppm of furazolidone and 22 ppm of lincomycin plus 22 ppm of spectinomycin. Each treatment was carried out in ten groups of eight piglets. The trials were continued from the fifth to the eighth week of life. Addition of lincomycin and spectinomycin improved both growth and feed conversion. Combined administration of lincomycin and spectinomycin with carbadox resulted in the best performance. Supplementation of carbadox alone did not produce any beneficial effects. Addition of 400 ppm of furazolidone resulted in a significant depression of growth. Combined administration of 400 ppm furazolidone and 50 ppm of carbadox resulted in the poorest performance. The growth depressing effect of this combined treatment was observed as early as the first two weeks of the experiment. The animals undergoing this treatment showed a greyish-white colour of the skin and very hard stools.

Animals↗

PubMed1975

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.

Anti-Bacterial Agents↗

PubMed2004

Generation of fertile transplastomic soybean.

We describe here the development of a plastid transformation method for soybean, a leguminous plant of major agronomic interest. Chloroplasts from embryogenic tissue of Glycine max have been successfully transformed by bombardment. The transforming DNA carries a spectinomycin resistance gene (aadA) under the control of tobacco plastid regulatory expression elements, flanked by two adjacent soybean plastome sequences allowing its targeted insertion between the trnV gene and the rps12/7 operon. All generated spectinomycin resistant plants were transplastomic and no remaining wild type plastome copies were detected. No spontaneous mutants were obtained. The transformation efficiency is similar to that of tobacco plastids. All transplastomic T0 plants were fertile and T1 progeny was uniformly spectinomycin resistant, showing the stability of the plastid transgene. This is the first report on the generation of fertile transplastomic soybean.

Drug Resistance↗

PubMed2005

Stable plastid transformation in lettuce (Lactuca sativa L.).

Although plastid transformation in higher plants was first demonstrated in the early 1990s it is only recently that the technology is being extended to a broader range of species. To date, the production of fertile transplastomic plants has been reported for tobacco, tomato, petunia, soybean, cotton and Lesquerella fendleri (Brassicaceae). In this study we demonstrate a polyethylene glycol-mediated plastid transformation system for lettuce that generates fertile, homoplasmic, plastid-transformed lines. Transformation was achieved using a vector that targets genes to the trnA/trnI intergenic region of the lettuce plastid genome employing the aadA gene as a selectable marker against spectinomycin. Spectinomycin resistance and heterologous gene transcription were shown in T(1) plants derived from self-pollinated primary regenerants demonstrating transmission of the plastid-encoded transgene to the first seed generation. Crossing with male sterile wild-type lettuce showed that spectinomycin resistance was not transmitted via pollen. Constructs containing the gfp gene showed plastid-based expression of green fluorescent protein. The lettuce plastid could have potential both as a production and a delivery system for edible human therapeutic proteins.

Crosses, Genetic↗

PubMed1989

Isolation of temperature-sensitive mutants of 16 S rRNA in Escherichia coli.

Temperature-sensitive mutants have been isolated following hydroxylamine mutagenesis of a plasmid containing Escherichia coli rRNA genes carrying selectable markers for spectinomycin resistance (U1192 in 16 S rRNA) and erythromycin resistance (G2058 in 23 S rRNA). These antibiotic resistance alleles, originally identified by Morgan and co-workers, enable us to follow expression of cloned rRNA genes in vivo. Recessive mutations causing the loss of expression of the cloned 16 S rRNA gene were identified by the loss of the ability of cells to survive on media containing spectinomycin. The mutations were localized by in vitro restriction fragment replacement followed by in vivo marker rescue and were identified by DNA sequence analysis. We report here seven single-base alterations in 16 S rRNA (A146, U153, A350, A359, A538, A1292 and U1293), five of which produce temperature-sensitive spectinomycin resistance and two that produce unconditional loss of resistance. In each case, loss of ribosomal function can be accounted for by disruption of base-pairing in the secondary structure of 16 S rRNA. For the temperature-sensitive mutants, there is a lag period of about two generations between a shift to the restrictive temperature and cessation of growth, implying that the structural defects cause impairment of ribosome assembly.

Ampicillin↗

PubMed1991

Evolution of Staphylococcus aureus resistance to erythromycin in Denmark, 1959 to 1988: correlations between characteristics of erythromycin-resistant bacteraemia strains.

In an attempt to characterize erythromycin-resistant Staphylococcus aureus we present the intricate relationships between the following factors: phage type, period of isolation, antibiogram, minimum inhibitory concentration (MIC) to erythromycin, inducible or constitutive resistance, spectinomycin susceptibility, hospital- or community-acquired infection, and mortality rate. We studied 718 cases of bacteraemia with erythromycin-resistant S. aureus, occurring between 1959 and 1988. Central factors were phage type pattern, period of isolation, and antibiogram. Between 1959 and 1973 the majority of the erythromycin-resistant strains were multiresistant and belonged to the 83A complex and the related group III. They were mainly inducibly resistant, spectinomycin resistant, and had intermediate MICs (1-4 mg l-1) to erythromycin. The majority of these strains came from hospital-acquired infections and still exist today, although in decreased numbers. By contrast, erythromycin-resistant S. aureus isolated in recent years are usually co-resistant only to penicillin and more rarely also to tetracycline. These strains have inducible resistance, are spectinomycin susceptible, and have a high erythromycin MIC. They are isolated both from hospital- and community-acquired infections. Strains with constitutive resistance to macrolides occurred at a stable low level (13%) during the whole observation period and always had high MICs to erythromycin. The mortality rate among patients with S. aureus bacteraemia due to an erythromycin-resistant strain was only associated with the year of infection and decreased from 61% in the first 15-year period to 40% in the subsequent 15 years.

Bacteriophage Typing↗

PubMed2002

Construction of a stable non-mucoid deletion mutant of the Streptococcus equi Pinnacle vaccine strain.

Streptococcus equi causes equine strangles, a purulent lymphadenopathy of the head and neck. An avirulent, non-encapsulated strain (Pinnacle) has been used widely in North America as an intranasal vaccine. The aim of the study was to create a specific mutation of the hyaluronate synthase (hasA) gene in Pinnacle to permanently abolish the production of capsule and provide an easily recognisable genetic marker. An internal fragment of hasA was generated by PCR and cloned into pTW100 (Microscience, UK). An encapsulated revertant of Pinnacle was then transformed with the recombinant plasmid by electroporation and cultured under conditions to promote homologous recombination. Among 90 spectinomycin resistant transformants observed, one non-mucoid (non-encapsulated) spectinomycin resistant colony was detected. The presence of plasmid sequence within the hasA gene was confirmed by the PCR. After six passages in antibiotic-free medium, four non-mucoid spectinomycin sensitive colonies were found. Sequence analysis of one of these clones, designated Pinnacle HasNeg, revealed loss of the 3' end of the hasA and the 5' end of the hasB genes. This deletion mutant should serve as a useful candidate to replace Pinnacle since it cannot revert to a mucoid phenotype and can be distinguished genetically from wild type strains.

Animals↗

PubMed1999

Susceptibility testing of Actinobacillus pleuropneumoniae in Denmark. Evaluation of three different media of MIC-determinations and tablet diffusion tests.

This study was conducted to compare the applicability of three different media in sensitivity testing of Actinobacillus pleuropneumoniae by means of MIC and tablet diffusion tests. The media used were: modified PPLO agar, chocolatized Mueller-Hinton-II and Columbia agar supplemented with NAD. Seven antimicrobial agents were tested: ceftiofur, enrofloxacin, penicillin, spectinomycin, tiamulin, trimethoprim + sulfadiazine and tylosin, against 40 randomly selected A. pleuropneumoniae isolates. In general, good agreement was found between results obtained with all combinations of media, most antimicrobials tested and the two-test systems. Some variations between media were observed for spectinomycin, tiamulin and tylosin. For ceftiofur and trimethoprim + sulfadiazine some isolates with low MIC-values were classified as resistant using tablet diffusion, indicating that the break points of resistance for these antimicrobials using the tablet diffusion tests need adjustment. Using current break points for resistance with MIC-determinations, all isolates tested susceptible to ceftiofur, enrofloxacin, penicillin, tiamulin and trimethoprim + sulfadiazine. A larger number of isolates tested resistant to spectinomycin and tylosin on all three media using both MIC determinations and tablet diffusion.

Actinobacillus Infections↗

PubMed2003

Plastid transformation in Lesquerella fendleri, an oilseed Brassicacea.

A plastid transformation protocol was developed for Lesquerella fendleri, a species with a high capacity for plant regeneration in tissue culture. Transformation vector pZS391B carried an aadA16gfp marker gene conferring streptomycin-spectinomycin resistance and green fluorescence under UV light. Biolistic transformation of 51 Lesquerella leaf samples, followed by spectinomycin selection, yielded two transplastomic clones. The AAD-GFP fusion protein, the marker gene product, was localized to chloroplasts by confocal laser microscopy. Fertile plants and seed progeny were obtained in line Lf-pZS391B-1. In the 51 samples a large number (108) of spontaneous mutants were identified. In five of the lines spectinomycin resistance was localized to a conserved stem structure by sequencing 16S rRNA genes. Success in L. fendleri, a wild oilseed species, extends plastid transformation beyond Arabidopsis thaliana in the Brassicaceae family.

Anti-Bacterial Agents↗

PubMed1976

National gonorrhea therapy monitoring study: in vitro antibiotic susceptibility and its correlation with treatment results.

To monitor temporal trends and regional differences in antibiotic susceptibility, we measured the minimum inhibitory concentrations for penicillin G, ampicillin, tetracycline, and spectinomycin of 4405 pre-treatment gonococcal isolates from patients with uncomplicated gonorrhea. As compared to isolates studied in 1970-1971, recent United States isolates appeared equally sensitive to penicillin G and more sensitive to tetracycline. Relatively resistant strains were found throughout the country. We also studied 1974 patients, treated for uncomplicated gonorrhea according to the 1972 regimens recommended by the United States Public Health Service, to determine the relation between pretreatment minimum inhibitory concentrations and treatment results. For patients receiving the procaine penicillin-probenecid and ampicillin-probenecid regimens, minimum inhibitory concentrations to the treatment drugs were significantly higher in patients not cured than in those cured (P less than 0.01 fr penicillin and P less than 0.05 for ampicillin). In contrast, spectinomycin-treatment results appeared to be independent of the isolate's susceptibility to spectinomycin and other antibiotics.

Ampicillin↗

PubMed1990

Base changes at position 792 of Escherichia coli 16S rRNA affect assembly of 70S ribosomes.

To investigate the function of base 792 of 16S rRNA in 30S ribosomes of Escherichia coli, the wild-type (adenine) residue was changed to guanine, cytosine, or uracil by oligonucleotide-directed mutagenesis. Each base change conferred a unique phenotype on the cells. Cells containing plasmid pKK3535 with G792 or T792 showed no difference in generation time in LB broth containing ampicillin, whereas cells with C792 exhibited a 20% increase in generation time in this medium. To study the effect on cell growth of a homogeneous population of mutant ribosomes, the mutations were cloned into the 16S rRNA gene on pKK3535 carrying a spectinomycin-resistance marker (thymine at position 1192), and the cells were grown with spectinomycin. Cells containing G792 or C792 showed 16% and 56% increases in generation time, respectively, and a concomitant decrease in 35S assimilation into proteins. Cells with T792 did not grow in spectinomycin-containing medium. Maxicell analyses indicated decreasing ability to form 70S ribosomes from 30S subunits containing guanine, cytosine, or uracil at position 792 in 16S rRNA. It appeared that C792-containing 30S ribosomes had lost the ability to bind initiation factor 3.

Base Sequence↗

PubMed1994

Direct selection of binding proficient/catalytic deficient variants of BamHI endonuclease.

Variants of BamHI endonuclease in which the glutamate 113 residue has been changed to lysine or the aspartate 94 to asparagine were shown to behave as repressor molecules in vivo. This was demonstrated by placing a BamHI recognition sequence, GGATCC, positioned as an operator sequence in an antisense promoter for the aadA gene (spectinomycin resistance). Repression of this promoter relieved the inhibition of expression of spectinomycin resistance. This system was then used to select new binding proficient/cleavage deficient BamHI variants. The BamHI endonuclease gene was mutagenized either by exposure to hydroxylamine or by PCR. The mutagenized DNA was reintroduced into E. coli carrying the aadA gene construct, and transformants that conferred spectinomycin resistance were selected. Twenty Spr transformants were sequenced. Thirteen of these were newly isolated variants of the previously identified D94 and E113 residues which are known to be involved in catalysis. The remaining seven variants were all located at residue 111 and the glutamate 111 residue was shown to be involved with catalysis.

Aspartic Acid↗

PubMedDate not supplied

Antimicrobial susceptibility of Neisseria gonorrhoeae isolates from a military population in San Diego.

Neisseria gonorrhoeae isolates were studied to determine their patterns of antimicrobial susceptibility and possible chemotherapeutic implications. Of 370 consecutive isolates, 32 (8.7%) were penicillinase-producing N. gonorrhoeae (PPNG). The remaining 338 were subjected to disk-diffusion tests, and those apparently resistant to penicillin, tetracycline, or spectinomycin were tested by an agar-dilution method. The dilution test showed that 5.4% (20/370) were penicillin-resistant, non-PPNG strains, of which 100%, 90%, and 45% were also resistant to tetracycline, cefoxitin, and erythromycin, respectively. No resistance to spectinomycin or ceftriaxone was demonstrated, although there was an association between minimum inhibitor concentrations (MICs) of penicillin of greater than or equal to 1.0 microgram/ml and increased MICs of ceftriaxone. The overall incidence of penicillin resistant isolates, including PPNG, was 14.1% (52/370). Of the 20 penicillin-resistant, non-PPNG strains, all were also resistant to tetracycline, and another 21 exhibited tetracycline resistance but were sensitive to penicillin. The in-vitro data suggested that: (1) neither penicillin, tetracycline, nor cefoxitin were acceptable drugs for routine treatment of gonorrhea in our population during the study period; (2) spectinomycin and ceftriaxone continue to demonstrate adequate in-vitro activity against N. gonorrhoeae despite increasing in-vitro resistance to penicillin; and (3) non-plasmid-mediated resistance to penicillin may predict future resistance to ceftriaxone.

Anti-Bacterial Agents↗

PubMed2000

Analysis of the antibiotic sensitivity of Neisseria gonorrhoeae in Guangzhou, Peoples Republic of China.

BACKGROUND: Sexually transmitted diseases began to re-emerge in China in the mid 1980s. During the last one and a half decades, Neisseria gonorrhoeae infection has become one of the three most common sexually transmitted diseases in China. At present, resistant strains of N. gonorrhoeae are increasing each year. This study was undertaken to better understand the sensitivity of five antibiotics to N. gonorrhoeae isolates in Guangzhou, China. GOAL: To determine the frequency and diversity of antibiotic resistance, particularly to penicillin and tetracycline, on gonococcal strains in Guangzhou. STUDY DESIGN: Strains of N. gonorrhoeae isolates from 203 patients with uncomplicated urethral gonococcal infections from Guangzhou, China were reviewed from September 1997 to August 1998. All strains were characterized with five different antimicrobials for sensitivity, including penicillin, tetracycline, spectinomycin, ciprofloxacin, and ceftriaxone. RESULTS: Penicillin resistance was present in 121 of 203 isolated strains (59.6%). The plasmid-mediated strains and chromosome-mediated strains among the penicillin-resistant strains that were resistance to penicillin were 5.8% and 94.2%, respectively. Plasmid-mediated strains resistant to penicillin and tetracycline were each 3.4%. Most isolated strains were resistant to ciprofloxacin, accounting for 60.6%. All strains were sensitive to spectinomycin and ceftriaxone. CONCLUSION: N. gonorrhoeae isolates exhibited a high rate of resistance to penicillin and ciprofloxacin. Spectinomycin highly effective for penicillin-producing N. gonorrhoeae, tetracycline-resistant N. gonorrhoeae and the highly resistant strains of ciprofloxacin.

Anti-Bacterial Agents↗