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Biomedical subjects

C Ison

Publications and source records attributed to C Ison.

28 records · Page 2Linked to original sources
PubMed1994

Neisseria gonorrhoeae acquires mutations in analogous regions of gyrA and parC in fluoroquinolone-resistant isolates.

Neisseria gonorrhoeae homologues of gyrA and parC have been identified using hybridization probes generated from conserved regions of diverse gyrA genes. These genes have been tentatively identified as gyrA and parC, based on predicted amino acid sequence homologies to known GyrA homologues from numerous bacterial species and to ParC from Escherichia coli and Salmonella typhimurium. The gyrA gene maps to a physical location distant from the gyrB locus on the gonococcal chromosome, which is similar to the situation found in E. coli. The parC gene is not closely linked (i.e. greater than 9 kb) to an identifiable parE gene in N. gonorrhoeae. The gonococcal GyrA is slightly larger than its E. coli homologue and contains several small insertions near the C-terminus of the predicted open reading frame. A series of ciprofloxacin-resistant mutants were selected by passage of N. gonorrhoeae on increasing concentrations of the antibiotic. Sequential passage resulted in the selection of isolates with minimum inhibitory concentrations approximately 10,000-fold higher than the parental strain. Mutations within gyrA resulted in low to moderate levels of resistance, while strains with high-level resistance acquired analogous mutations in both gyrA and parC. Resistance mutations were readily transferred between N. gonorrhoeae strains by transformation. The frequencies of transformation, resulting in different levels of ciprofloxacin resistance, further support the notion that both gyrA and parC genes are involved in the establishment of extreme levels of ciprofloxacin resistance.

Amino Acid Sequence↗
PubMed1983

Differentiation of neisseriaceae by isoenzyme electrophoresis.

Analysis of 71 strains of Neisseriaceae by starch-gel electrophoresis of hexokinase, phosphoglucomutase, glucose phosphate isomerase, and L-malate-nicotinamide adenine dinucleotide phosphate oxidoreductase showed that all gonococci and all memingococci have a characteristic hexokinase isoenzyme that is specific for each species and clearly distinguishes meningococci and gonococci from each other and from other species of Neisseriaceae. Strains of gonococci that were transformed into maltose utilizers by DNA from Neisseria lactamica and Neisseria meningitidis showed no change in the isoenzymes so that they could still be differentiated from meningococci and other Neisseriaceae by isoenzyme electrophoresis. In view of the limited sensitivity and specificity of conventional tests for the identification of gonococci and the possibility that gonococci may be transformed into maltose utilizers by DNA from normal throat flora, electrophoresis of hexokinase isoenzymes should be useful for the precise laboratory identification of the pathogenic neisseriae, especially those from atypical sites and those giving indeterminate reactions.

Electrophoresis, Starch Gel↗
PubMed1982

Acquisition of new genes by oral Neisseria.

It is suggested that part of the increased pharyngeal carriage of meningococci reported in patients with gonorrhoea is due to misidentification of gonococci which have been transformed to maltose fermenters by DNA from normal throat flora. The distribution of specific aminopeptidases in strains of gonococci, meningococci isolated from the throat and meningococci from systemic infections is consistent with this view. Gonococci oxidising maltose and gonococci with gamma-L-glutamyl aminopeptidase activity, both factors regarded as typical of Neisseria meningitidis, can be produced in vitro by transformation with DNA from N lactamica and N meningitidis. The clinical and theoretical implications of such changes are discussed.

Aminopeptidases↗
PubMed1978

Serological diagnosis of gonorrhoea by an enzyme-linked immunosorbent assay (Elisa).

IgG antibody to an outer membrane protein extracted from Neisseria gonorrhoeae was measured in patients with gonorrhoea. The level in such patients was significantly higher than in normal controls or in patients with other conditions who were attending the clinic for sexually transmitted diseases. Significantly higher antibody levels were detectable in half the patients within a few days of infection and in a similar proportion of carriers--both male and female. Men with rectal gonorrhoea had particularly high antibody levels. Sixteen per cent of presumptively normal men and 11% of normal women gave positive results but the actual false positive rate could be lower.

Adolescent↗
PubMed1978

Bulk growth of Neisseria gonorrhoeae type 1 in a biphasic system.

A biphasic system for the bulk growth of Neisseria gonorrhoeae is described. It appears to combine the convenience of liquid media with the growth qualities of solid media. By using the agar in dialysis tubes rather than as slabs the surface-to-volume ratio was improved and harvesting made easier. The system is also useful in isolating gonococci from blood and joint fluids in patients with disseminated infection.

Agar↗
PubMed1977

Which Neisseria?

A case of disseminated gonococcal infection in which the gonococcus was isolated from the blood and genitalia and the meningococcus from the throat is described. A second patient, in whom the meningococcus was isolated from the throat and the gonococcus from the genitals but in whom no organisms were recovered from the blood, had lesions resembling those of a disseminated infection. The results of 150 throat cultures from patients who were examined at a clinic because they had a history of oral sexual intercourse are presented. The meningococcus was isolated nearly six times more often in patients with genital gonorrhoea than in those in whom genital cultures were negative, while the gonococcus was found 2 1/2 times more often in those who carried the meningococcus in the throat than in those who did not. If these findings can be confirmed it could indicate an individual susceptibility to the acquisition of Neisserian organisms that would merit further investigation.

Adult↗
PubMedDate not supplied

Persistence of multiple serovars of Neisseria gonorrhoeae.

Two simple mathematical models of gonococcal transmission dynamics that allow for heterogeneity within the pathogen were assessed. Models were compared for their ability to mirror the observed persistence of different gonococcal serovars over time and differential distribution within subgroups of the total population. Serotyping data collected between the periods of 1984-1988 and 1988-1990 were analyzed for differences in serovar distribution. The data show persistence of multiple serovars within both homosexual and heterosexual contact groups over time. The models provide a framework for the use of phenotypic markers to assess behavior change in sexually active populations.

Gonorrhea↗