Search PubMed⌕ Search

Biomedical subjects

C A Ison

Publications and source records attributed to C A Ison.

At least 73 records · Page 4Linked to original sources
PubMed1992

Concordance of auxotype/serovar classes of Neisseria gonorrhoeae between sexual contacts.

One hundred and three known sexual-contact pairs of patients with culture-proven gonorrhoea who attended St Mary's Hospital, London between May 1989 and February 1991 were identified. All isolates from these patients were serotyped and auxotyped and compared for type concordance within sexual-contact pairs. Serotype was concordant in 80 (78%) of 103 sexual-contact pairs, auxotype in 88 (85%) and auxotype/serovar (A/S) class in 66 (64%) on the first screening. All pairs of isolates showed concordance in both serotype and auxotype when typing was repeated using a single set of serotyping reagents and of auxotyping media. Seventeen serovars, 9 auxotypes and 36 A/S classes were found in this population. Our results suggest that both serotyping and auxotyping may be used as markers to allow tracing of sexual-contact pairs, but that a single set of reagents should be used to ensure maximum reliability.

Contact Tracing↗
PubMed1992

A longitudinal study of pelvic inflammatory disease.

OBJECTIVE: To study the microbiology and long term prognosis of pelvic inflammatory disease (PID). DESIGN: A prospective study of women with laparoscopically confirmed PID. SETTING: Teaching hospital in central London. SUBJECTS: 23 women with PID. OUTCOME MEASURES: Microbiological investigations at the time of diagnosis and at follow up; subsequent fertility and the occurrence of pelvic pain. RESULTS: PID diagnosed by laparoscopy was regarded as moderate to severe in 15 cases. Neisseria gonorrhoeae, Chlamydia trachomatis, Mycoplasma hominis and Ureaplasma urealyticum or a combination of these micro-organisms were detected most frequently in the cervix, less often in the endometrium and least in the tubes, C. trachomatis being the micro-organism found most commonly in the tubes. There was serological evidence of acute chlamydial infection in 13 of 20 cases in which paired sera were available and a serological response to M. hominis in 9 of 12 cases in which it was possible to evaluate the results. On the basis of microbiological and serological results, C. trachomatis appeared to be the most important aetiological agent in 10 cases, N. gonorrhoeae in four cases, M. hominis in three cases and U. urealyticum in none; in five cases, two of these micro-organisms appeared to be of equal importance. After 1 to 3 years, 33% of the women were having difficulty conceiving and 56% continued to complain of pelvic pain. CONCLUSION: It is difficult to be certain of the infectious cause of PID in any given case. However, the evidence that N. gonorrhoeae and C. trachomatis are pathogens is very strong. M. hominis may be responsible for a few cases on its own or together with other micro-organisms.

Cervix Uteri↗
PubMed1992

The dominance of a multiresistant strain of Neisseria gonorrhoeae among prostitutes and STD patients in The Gambia.

OBJECTIVE: To study the epidemiology of antibiotic resistant strains of Neisseria gonorrhoeae from sexually transmitted disease clinics in The Gambia. MATERIALS AND METHODS: One hundred and sixty five strains of N gonorrhoeae were tested for their antibiotic susceptibility, auxotype, serotype, and plasmid content. RESULTS: Of the total population 84 (51%) were non-penicillinase producing (nonPPNG) and 81 (49%) penicillinase-producing N gonorrhoeae (PPNG). There were 16 serovars, five auxotypes and 33 auxotype/serovar (A/S) classes in the total population and the nonPPNG. Among PPNG only five serovars, two auxotypes and nine A/S classes were found. One A/S class predominated, NR/IB-7 (86 isolates), of which 66 (77%) were PPNG and the remainder were chromosomally-mediated resistant N gonorrhoeae (CMRNG). These strains also showed reduced susceptibility to ciprofloxacin, ceftriaxone and tetracycline and were evenly distributed among patient groups. CONCLUSION: We have identified a relatively homogeneous gonococcal population with a core group of isolates exhibiting high levels of antibiotic resistance.

Drug Resistance, Microbial↗
PubMed1991

Epidemiology of penicillin resistant Neisseria gonorrhoeae.

OBJECTIVE: To study the epidemiology of Neisseria gonorrhoeae that exhibit both chromosomal and plasmid-mediated resistance to penicillin. MATERIALS AND METHODS: A total of 1589 strains of N gonorrhoeae isolated from patients attending St Mary's Hospital, London were tested for both their susceptibility to penicillin and for their auxotype and serotype. RESULTS: Of the 940 non-penicillinase producing N gonorrhoeae, 840 were considered penicillin sensitive (MIC less than or equal to 0.5 mg/l) and 100 were chromosomally-mediated resistant N gonorrhoeae (CMRNG), (MIC greater than or equal to 1.0 mg/l). Of the 649 penicillinase producing N gonorrhoeae (PPNG), 429 carried the 4.4 megadalton (MDa) penicillinase encoding plasmid and 220 carried the 3.2 MDa plasmid. CMRNG were predominantly serogroup IB (90%). PPNG with 3.2 MDa plasmid were the only group more often serogroup IA (58%) than IB (42%). Serovar IA-1/2 and requirement for arginine, hypoxanthine and uracil (AHU) were associated with increased susceptibility to penicillin whereas serovar IB-5/7 was associated with decreased susceptibility in nonPPNG. There was a significant difference in the distribution of the IA and IB serovars between PPNG carrying either the 4.4 MDa or 3.2 MDa plasmid. AHU and PAOU requiring strains were not found among PPNG and were uncommon among CMRNG. CONCLUSION: Some clear associations have been found but the pattern among PPNG appears more complex and in most instances could be related to clusters of a single strain over a short time span.

Chromosomes↗
PubMed1990

Current status of serotyping of Neisseria gonorrhoeae.

Protein I has become the basis of serotyping of N. gonorrhoeae. A panel of 12 anti-protein I monoclonal antibodies is supplied by Syva Company, Palo Alto, CA, through distributors for research purposes only. These distributors are responsible for storing the monoclonal antibodies, supplying research groups and training new users, particularly in the interpretation of coagglutination reactions. A European Workshop was held in Heidelberg, Federal Republic of Germany in July 1988 to discuss serotyping with these antibodies. The current uses of serotyping of N. gonorrhoeae include epidemiological studies, clinical purposes and surveillance of antibiotic resistance and plasmid carriage. Predominant serovars may be subtyped either by additional antibodies or with the use of another technique, such as auxotyping, determination of antibiotic sensitivities, plasmid analysis or genetic fingerprinting. Conversely, there is growing evidence that it may be appropriate to group certain serovars together. Data collected during prevalence studies could be combined with clinical information and an international data bank set up. This supposes a close future collaboration of all groups involved in the epidemiology of N. gonorrhoeae.

Antibodies, Monoclonal↗
PubMed1990

Transfer of beta-lactamase plasmids by conjugation in Neisseria gonorrhoeae.

Conjugation experiments in vitro have been used in an attempt to explain certain epidemiological phenomena seen amongst penicillinase producing Neisseria gonorrhoeae (PPNG) isolated at St Mary's Hospital, London. These include changes in plasmid profiles, a lack of beta-lactamase encoding plasmids in PAOU-requiring strains and a difference in the serological classification of strains of PPNG and non-PPNG isolated from the same clinic. It was shown that acquisition of the conjugative plasmid by beta-lactamase producing transconjugants does vary, but is not related to the auxotype/serovar (A/S) class of, or type of beta-lactamase plasmid carried by the donor. It was not possible to transfer either the 3.2MDa or 4.4MDa plasmids to PAOU-requiring strains of N gonorrhoeae. The conjugation frequency from a single donor to different recipients was shown to be variable, but was not influenced by the serovar of the recipients. It was shown that the transfer and acceptance of beta-lactamase encoding plasmids is variable but it was not possible to identify the factors responsible.

Conjugation, Genetic↗
PubMed1990

Penicillin and cephalosporin resistance in gonococci.

Non-penicillinase producing Neisseria gonorrhoeae isolated at St Mary's Hospital, London were examined for the prevalence of resistance to penicillin and for decreased susceptibility to cefuroxime. Of the 941 non-PPNG tested 100 (10.6%) were resistant to penicillin (minimum inhibitory concentration, MIC, greater than or equal to 1 mg/l) and were considered to be chromosomally-resistant N gonorrhoeae (CMRNG). Decreased susceptibility to cefuroxime (MIC, greater than or equal to 0.5 mg/l) was detected in 79% of the CMRNG. The CMRNG were also more often prototrophic and of serogroup IB than the remaining non-PPNG. The correlation coefficient for resistance to penicillin and cefuroxime was high, 0.79. Transformation experiments with both genetically-defined strains and transformants obtained using DNA from clinical isolates, showed that increased resistance to cephalosporins was acquired in three steps in close association with penicillin. We think this suggests that the loci controlling resistance to the cephalosporins are identical or closely linked to those controlling penicillin resistance.

Cefuroxime↗
PubMed1990

Laboratory methods in genitourinary medicine. Methods of diagnosing gonorrhoea.

Gonorrhoea is normally diagnosed presumptively by the presence of intracellular Gram-negative cocci on a Gram stain and confirmed by culture of the causative organism, Neisseria gonorrhoeae. Alternative methods have been evaluated extensively for the detection of gonococci in clinical specimens including immunological techniques such as ELISA and immunofluorescence, DNA probes, genetic transformation and the limulus lysate assay. Some of these tests have proved as sensitive and specific for the detection of gonorrhoea in symptomatic men as the Gram stain but offer no advantage in time or cost. In women, no test has been found that shows a sensitivity and specificity sufficiently adequate for clinical use. Culture in men and women remains the method of choice for diagnosis. In addition the need to obtain the infecting organism for antibiotic susceptibility testing has not been overcome. In contrast, the rapid identification of N gonorrhoeae can be achieved within four hours using either monoclonal antibodies or by the detection of preformed enzymes. New methods for both the detection and identification of N gonorrhoeae should be carefully evaluated particularly for use in cases of child and sexual abuse where medico-legal problems may arise.

Adult↗
PubMed1989

Sampling methods for monitoring changes in gonococcal populations.

A total of 160 consecutive isolates of Neisseria gonorrhoeae was collected over a 3-month period. They were tested for their susceptibility to penicillin, erythromycin and spectinomycin and the auxotype and the serotype determined. We have evaluated two sampling methods, the collection of every fifth isolate and the first 20 isolates (10 male and 10 female) each month, to determine whether either is representative of the total population. There was no significant difference between either method of sampling and the total for detecting the predominant auxotypes and serovars or the distributions in antibiotic susceptibility. It is possible to monitor major changes in a gonococcal population, particularly susceptibility to antibiotics, using a sample of the total population.

Bacterial Typing Techniques↗
PubMed1989

Characterisation of monoclonal antibodies for detection of Mobiluncus spp. in genital specimens.

Monoclonal antibodies were raised to the anaerobic curved rods, Mobiluncus curtisii subsp. curtisii NCTC 11656, M. curtisii subsp. holmesii NCTC 11657 and M. mulieris NCTC 11658. Three antibodies reacted with the two subspecies of M. curtisii and, when used in combination against clinical isolates, showed 100% sensitivity and specificity in immunofluorescence studies. Immunoblotting showed that two of these antibodies reacted with an epitope on a protein which had an electrophoretic mobility corresponding to a Mr of 75 Kda in the absence of a reducing agent and 82 Kda in its presence in both type strains and in clinical isolates. The third antibody reacted with an epitope in type strains which had a mobility corresponding to 75 Kda and was unaffected by a reducing agent. However, in clinical isolates the epitope was present on a protein of 75 Kda or 71 Kda, or on both. A fourth antibody showed reactivity with M. mulieris NCTC 11658 alone, but only 6 (24%) of 25 clinical isolates gave positive results by immunofluorescence. The epitope is believed to be present on a protein of greater than 90 Kda. All four antibodies were shown by immunogold staining to be directed against epitopes exposed on the cell surface.

Antibodies, Bacterial↗
PubMed1989

Changes in penicillinase-producing Neisseria gonorrhoeae isolated in London.

To investigate changes in the gonococcal population over time, the plasmid content, serotype and auxotype have been determined for strains of penicillinase-producing Neisseria gonorrhoeae (PPNG) isolated from patients attending the Praed Street Clinic for Sexually Transmitted Diseases between 1978 and 1987. Three distinct changes have been identified: (i) in the main plasmid type, from PPNG with the 3.2-Mda plasmid before 1982 to strains with the 4.4-Mda plasmid between 1982 and 1985; (ii) the decline during this time of strains also carrying the 24.5-Mda conjugal plasmid; (iii) the re-emergence of PPNG with the 3.2-Mda plasmid in 1986. The three typing methods used have identified eight clusters of strains which have been prevalent in different years between 1978 and 1987.

Bacterial Typing Techniques↗
PubMed1989

Associations between serotype and susceptibility to antibiotics of Neisseria gonorrhoeae.

A serological classification scheme for Neisseria gonorrhoeae was used to investigate the epidemiological associations between gonococcal serotype and other bacterial and host characters. Six hundred and fifty clinical isolates of non-penicillinase producing N gonorrhoeae from the Praed Street Clinic, St Mary's Hospital, were included in this study. The strains collected represented 41 serovars, although 485 (75%) of the 650 strains belonged to five serovars. Strains of serovar IA-1/2 were commonly isolated from the cervix and tended to be sensitive to penicillin and moderately resistant to erythromycin. Strains of serovar IB-1 showed bimodal patterns of susceptibility to both penicillin and erythromycin and were obtained equally from all anatomical sites. Strains of serovar IB-2 were isolated more often from the rectum and were associated with homosexually acquired infections, whereas those of serovar IB-3 were sensitive to erythromycin and were rarely isolated from the rectum. Strains of IB-5/7 were more resistant to penicillin and erythromycin than strains of other serovars. The serological classification of N gonorrhoeae is thus a powerful tool that may be used to study biological characteristics of the gonococcus, such as susceptibility to antimicrobials and site tropism.

Anti-Bacterial Agents↗