Search PubMed⌕ Search

Biomedical subjects

J Brunton

Publications and source records attributed to J Brunton.

48 records · Page 3Linked to original sources
PubMed1982

Molecular epidemiology of beta-lactamase-specifying plasmids of Haemophilus ducreyi.

We have studied the genetic basis of beta-lactamase production in eight strains of Haemophilus ducreyi isolated in diverse areas of the world. Beta-lactamase production in all strains was mediated by plasmids having a molecular mass of either 5.7 or 7.0 megadaltons. Plasmids of 5.7 megadaltons were shown to carry the entire sequence of pFA7, the beta-lactamase specifying plasmid found in isolates of Neisseria gonorrhoeae epidemiologically linked to West Africa. Plasmids of 7.0 megadaltons were shown to carry the entire sequence of pFA3, the beta-lactamase specifying plasmid found in Far Eastern isolates of N. gonorrhoeae. Both groups of H. ducreyi plasmids were shown to carry physically complete and functional TnA sequences. Thus we have identified two types of H. ducreyi beta-lactamase plasmid which are identical to the two types of N. gonorrhoeae beta-lactamase plasmid, except that they carry complete TnA sequences.

Base Sequence↗
PubMed1981

Molecular nature of a plasmid specifying beta-lactamase production in Haemophilus ducreyi.

We characterized pJB1, the plasmid previously reported to mediate beta-lactamase production in Haemophilus ducreyi. We studied its relationship to pMR0360 and RSF0885, the plasmids responsible for beta-lactamase production in Neisseria gonorrhoeae and Haemophilus parainfluenzae, respectively. Although pJB1 was maintained as a multicopy pool in Escherichia coli, it was not stably maintained in the absence of antibiotic selection. Electron microscope heteroduplex studies showed that it carried 100% of the transposable ampicillin resistance sequence TnA. This sequence was transposed to plasmid pUB307 at a low rate. Heteroduplexes between pMR0360 and pJB1 showed that they contained 3.3 megadaltons of homologous sequences. Two sets of nonhomologous sequences, one a TnA sequence and the other a non-TnA sequence, took the form of insertion loops. For plasmids pMR0360 and RSF0885, previously shown to be highly related, the nonhomologous sequences took the form of a substitution loop. We concluded that all three plasmids shared major portions of their sequences but differed in discrete segments. pJB1 was the first such plasmid to have a physically and functionally intact TnA sequence.

Ampicillin↗
PubMed1980

Enterotoxigenic Escherichia coli in central Canada.

During epidemiological studies carried out in urban and rural areas of the midwestern Canadian province of Manitoba, we cultured enterotoxigenic Escherichia coli (ETEC) from 16 (1.7%) of 945 diarrheal stools and 4 (0.3%) of 1,282 normal stools. ETEC was found in not more than 2.3% of diarrheal stools obtained from any population during any season. Diarrhea associated with ETEC persisted for a mean of 9 days. Two children were dehydrated and required intravenous fluid therapy, and one adult suffered a cholera-like syndrome. Half of the children required hospitalization for management of their diarrhea. Two adults and two children who harbored ETEC were completely asymptomatic. The pattern of toxin production correlated with serotype and the serotypes encountered were (with a few exceptions) similar to those found in other areas. We conclude that ETEC is an uncommon cause of diarrhea, both in rural and urban areas of central Canada. However, the possibility that ETEC might cause severe sporadic cases or epidemics of gastroenteritis remains.

Adult↗
PubMed1978

Biochemical characteristics of Haemophilus influenzae in relationship to source of isolation and antibiotic resistance.

Based on a limited number of biochemical properties, a system for biotyping Haemophilus influenzae (M. Kilian, Acta Pathol. Microbiol, Scand. Sect. B82:835-842, 1976) was used to analyze the relationship of biotype to source of infection and antibiotic resistance for 600 clinical strains. The distribution of biotypes from bacteremic patients was significantly different (P less than 0.001) from the distribution of biotypes from nonbacteremic patients. Although there appeared to be a correlation between biotype and source of isolation, no single biotype correlated with a specific clinical syndrome in bacteremic patients. The frequency of resistance to antibiotics (ampicillin, tetracycline, chloramphenicol, and kanamycin), which was known to be at least in part plasmid mediated, was determined. Of the 600 isolates, 43 were resistant to at least one antibiotic (30 were ampicillin resistant, 11 were tetracycline resistant, 1 was ampicillin-tetracycline resistant, and 1 was tetracycline-chloramphenicol resistant). Of these 43 resistant isolates, 42 were either biotype I or II. This distribution of biotypes among antibiotic-resustant isolates was significantly different from the overall distribution of biotypes (P is less than 0.001).

Adolescent↗
PubMedDate not supplied

Molecular epidemiology of antibiotic resistance plasmids of Haemophilus species and Neisseria gonorrhoeae.

Ampicillin resistance in Haemophilus influenzae and Neisseria gonorrhoeae is most commonly due to plasmid-mediated production of the TEM beta-lactamase. The H. influenzae plasmids may have evolved by insertion of various antibiotic resistance transposons into a phenotypically cryptic plasmid found in one of 699 isolates of H. influenzae examined. The small, nonconjugative, beta-lactamase-specifying plasmids of N. gonorrhoeae and Haemophilus species are highly related. Phenotypically cryptic plasmids found in several epidemiologically distinct isolates of Haemophilus parainfluenzae are highly related to the beta-lactamase plasmids but carry no transposon A (TnA) sequences. This evidence strongly favors the hypothesis that the beta-lactamase plasmids evolved by the insertion of TnA (possibly introduced from enteric bacteria) into cryptic plasmids resident in H. parainfluenzae.

Conjugation, Genetic↗