Biomedical subjects
C A Ison
Publications and source records attributed to C A Ison.
Immunological specificity of secretory IgA.
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Enzyme-linked immunosorbent assay (ELISA) to detect antibodies in gonorrhea using whole cells.
The choice of an antigen that will adequately differentiate between infected and non-infected patients has been a problem in detecting gonococcal antibodies for diagnosis. We have used the sensitive technique of ELISA to test various serotypes of Neisseria gonorrhoeae for their suitability as antigens. Whole cells of each serotype were attached to polystyrene plates using poly-L-lysine, N gonorrhoeae, strain H1 type 1 was used to detect antibodies in patients with known clinical history and then as a standard to evaluate the ability of different serotypes to differentiate between infected and non-infected groups.
Classes of antibodies in acute gonorrhoea.
In patients with acute gonorrhoea the antibody responses to envelope antigens of Neisseria gonorrhoea were investigated with a sensitive enzyme-linked immunosorbent assay. IgG antibodies predominated even early in the disease but IgM and IgA antibodies were present. Surprisingly there were circulating antibodies linked to secretory piece. These were largely but not entirely IgA and were presumed to have been absorbed from sites of local production.
Treatment of gonorrhea with clavulanate-potentiated amoxicillin (Augmentin).
One hundred sixty-one patients with culture-proved Neisseria gonorrhoeae infection were treated with a single oral dose of amoxicillin trihydrate (3 g) and potassium clavulanate (Augmentin, 0.25 g). Of 153 patients infected with non-penicillinase-producing strains of N. gonorrhoeae, 139 (91%) were cured, and five (62.5%) of eight patients infected with penicillinase-producing N. gonorrhoeae were cured. Augmentin was successful in eradicating N. gonorrhoeae from the rectum; 30 (97%) of 31 such infections were cured.
Chromosomal resistance to antibiotics in gonococci from Bahrain.
Ninety-one isolates of non-penicillinase-producing Neisseria gonorrhoeae from patients in Bahrain were tested for serotype, auxotype, and antibiotic susceptibility. Ten serovars and three auxotypes were found. Of the 91 isolates, 49 (54%) were serovar IB-5/7, 59 (65%) had a penicillin MIC greater than or equal to 1 mg/l, 39 (45%) had a cefuroxime MIC greater than or equal to 0.5 mg/l, and 63 (69%) had a tetracycline MIC of greater than or equal to 4 mg/l. No spectinomycin or high-level tetracycline resistance was seen. Seventy of the 91 isolates were tested against ciprofloxacin and ceftriaxone, and 40 (57%) and 26 (37%) had MICs greater than or equal to 0.03 mg/l, respectively. DNA from two penicillin-resistant isolates was capable of transforming recipient strain FA19 to donor level of penicillin and cephalosporin resistance in four steps. The first three steps were indicative of the acquisition of known resistance mutations. The existence of the fourth level transformants, with the ability of donor DNA to transform strain FA140 to higher levels of resistance, suggest the presence of another resistance mutation.
Tetracycline-resistant Neisseria gonorrhoeae. Characteristics of patients and isolates at a London Genitourinary Medicine Clinic.
OBJECTIVES: To compare auxotypes, serovars, and antibiograms of tetracycline-resistant Neisseria gonorrhoeae (TRNG) and non-TRNG isolated from patients attending an East London Genitourinary Medicine (GUM) Clinic. To obtain plasmid profiles for penicillinase-producing gonococci (PPNG) as well as presumptive TRNG. To identify differences in patient characteristics for the TRNG and non-TRNG patient groups. STUDY DESIGN: Gonococcal isolates were collected from 400 patients attending the GUM clinic at the Royal London Hospital GUM Clinic over a 1-year period. Isolates (378) were tested for susceptibility to various antibiotics, auxotyped, and serotyped. Plasmid profiles were obtained for PPNG and isolates exhibiting high-level tetracycline resistance (TRNG). The presence of the tet M determinant was confirmed using the polymerase chain reaction (PCR). The PCR product was digested with the restriction endonuclease (RE) Hpa II and electrophoresed on a 2.5% agarose gel to determine an "RE pattern." Patient data were collected by retrospective case-note review. RESULTS: TRNG (n = 42) accounted for 11% of the 378 isolates tested, and the remaining 336 (89%) isolates were non-TRNG. Non-requiring auxotrophy and P1B-2 serovar expression occurred more frequently among TRNG. PPNG accounted for 31% of TRNG and 5% of non-TRNG. Chromosomal resistance to penicillin (CMRNG) was absent among TRNG but accounted for 11% of non-TRNG. One TRNG isolate showed decreased susceptibility to ciprofloxacin (MIC 0.25 mg/l). All isolates were sensitive to cefotaxime, cefixime, spectinomycin, and azithromycin. All TRNG possessed the 25.2 MDa plasmid and produced a PCR product of appropriate size after tet M gene sequence amplification. RE digests of the PCR product gave a single pattern. None of the TRNG in contrast to 18% of the non-TRNG were acquired homosexually. Ethnic distribution differed between the patients with TRNG and patients without non-TRNG (Afro-Caribbean 81% versus 58%; white 19% versus 36%). Most TRNG were acquired in the United Kingdom. CONCLUSIONS: TRNG differ from the non-TRNG in their auxotype and serovar distribution. PPNG are more common among the TRNG isolates, whereas CMRNG appear absent. TRNG are isolated more commonly from Afro-Caribbean patients and were not represented among homosexually acquired isolates.
Sexual partner networks in the transmission of sexually transmitted diseases. An analysis of gonorrhea cases in Sheffield, UK.
BACKGROUND AND OBJECTIVES: Routine contact tracing data on patients with gonorrhea are used to identify sexual partner networks. These are combined with gonococcal typing data to study patterns of transmission. The role of persons in transmission is discussed. STUDY DESIGN: Contact tracing data on patients with gonorrhea attending the Royal Hallamshire Hospital in Sheffield in 1988 and 1989 are analyzed. Gonococcal strains identified by auxotype/serovar (A/S) class are combined with these data to identify transmission paths. RESULTS: The network contained 1,272 persons, 724 (77%) of whom had gonorrhea during the study period. Four hundred two clusters of linked cases were identified. The largest cluster, containing 35 persons connected over 16 months, is discussed in greater detail to illustrate how these data may help identify patterns of transmission and the role of persons. CONCLUSION: Contact tracing data can be used to identify sexual partner networks and to study transmission patterns. Microbiologic data can aid interpretation. An person's risk of acquiring infection depends on indirect links as well as direct links. To understand patterns of transmission it may be important to distinguish between those involved in transmission and those only acquiring infection. Networks established through gonococcal transmission are also relevant to the transmission of other sexually transmitted diseases.
Detection of the tetM determinant in Neisseria gonorrhoeae.
BACKGROUND AND OBJECTIVES: Plasmid-mediated high level resistance to tetracycline in Neisseria gonorrhoeae has become a therapeutic problem in many parts of the world. Simple, fast and accurate screening tests are required to enable rapid detection. GOAL OF THE STUDY: To evaluate screening tests for high-level tetracycline resistance for their ability to predict the presence of the tetM determinant in Neisseria gonorrhoeae. STUDY DESIGN: Strains considered to exhibit plasmid-mediated (90) and chromosomal resistance (19) to tetracycline were used to compare the screening tests, growth on tetracycline agar, disc testing, MIC and plasmid content, with confirmation by hybridization to the tetM probe. A polymerase chain reaction to amplify tetM in N. gonorrhoeae was also evaluated. RESULTS: All strains defined as presumptive TRNG by the screening tests hybridized with the tetM probe. None of the low-level resistant strains were positive in the screening tests or hybridized with the probe. In addition, the polymerase chain reaction (PCR) on whole bacterial cells detected tetM in all TRNG tested. Restriction enzyme digests of the PCR product gave three patterns suggesting genetic diversity within the tetM determinant of N. gonorrhoeae. CONCLUSION: Simple screening tests were found to be reliable predictors of TRNG. tetM was detected by PCR in all strains tested and exhibited some genetic variation that may be of use for epidemiological typing.