Showing papers by "Marilyn C. Roberts published in 1987"

Conjugal transfer of transposon Tn916 from Streptococcus faecalis to Mycoplasma hominis.

Abstract: Transposon Tn916 was transferred from Streptococcus faecalis to Mycoplasma hominis by a mating process resembling conjugation with a frequency of 10(-6) to 10(-7). Tn916 was inserted into the mycoplasmal chromosome in single and multiple copies.

Chromosomal DNA Probes for the Identification of Bacteroides Species

Abstract: Summary: We compared 22 Bacteroides species by DNA-DNA homology studies using the S1 endonuclease method. None of the currently defined species shared more than 30% DNA homology with any other species examined with the exception of B. buccae and B. capillus (which along with B. pentosaceus are now considered a single species), which shared 86% of their DNA sequences. Two clusters showed weak genetic relationships, with DNA homology > 10%. The first cluster included B. corporis, B. disiens, B. bivius, B. intermedius and B. melaninogenicus. The second cluster included B. fragilis, B. eggerthii, B. ovatus, B. thetaiotaomicron and B. uniformis. Five of the oral species, B. asaccharolyticus, B. gingivalis, B. loescheii, B. intermedius and B. melanogenicus, were chosen for study as whole chromosomal probes in dot blot assays. These were tested against 243 clinical strains biochemically identified as Bacteroides species. The DNA probes correctly identified 94% of the clinical strains. DNA probe and biochemical identification was 100% for two of the five species. In contrast, only 86% of the strains biochemically identified as B. intermedius were identified by the DNA probe. The DNA probes gave a species identification to seven strains which could not be biochemically identified.

Cloning and characterization of tetM gene from a Ureaplasma urealyticum strain.

Abstract: We have cloned a 4.9-kilobase (kb) HincII fragment which contains a tetracycline resistance determinant (tetM) from the chromosome of Ureaplasma urealyticum. The 4.9-kb HincII fragment contains DNA in addition to the structural gene, is closely related to the previously characterized 5.0-kb fragment from pJI3, and contains no normal ureaplasmal DNA sequences.

DNA probes for the detection of mycoplasmas in genital specimens.

Abstract: The utility of whole-genomic DNA probes for the detection of infections by genital mycoplasmas was investigated in 220 men attending a sexually transmitted diseases clinic. In 144 patients, probe results were compared with quantitative culture results. The prevalence of Mycoplasma hominis was 11% by culture, whereas the prevalence of ureaplasmas was 38%. The M. hominis DNA probe detected 9 of 16 M. hominis culture-positive specimens and 2 of 128 culture-negative specimens. The Ureaplasma urealyticum DNA probe detected 36 of 57 U. urealyticum culture-positive specimens and 18 of 87 culture-negative specimens. Most of the probe-negative culture-positive specimens had colony counts of less than 10(3) organisms/ml of specimen. The DNA probe does not require viable organisms, and the probe-positive, culture-negative specimens suggest that false-negative cultures occurred, perhaps due to specimen handling or insensitivity of culture methods for some strains of mycoplasmas.