H Young

Azithromycin and erythromycin resistant Neisseria gonorrhoea e following treatment with azithromycin

Summary: A pre-treatment and a 3-week post-treatment isolate of Neisseria gonorrhoeae from a 13-year-old boy treated with azithromycin in a single 1 g oral dose were characterized microbiologically. Both isolates were of the same serovar/ auxotype (1B6/non-requiring) and had similar antibiograms apart from erythromycin and azithromycin: the pre- and post-treatment MICs (minimum inhibitory concentrations) were: 1 mg/L and 32 mg/L to erythromycin and 0.125 mg/L and 3 mg/L to azithromycin. The finding that both isolates were 1B6/NR, had similar antibiograms (other than azithromycin and erythromycin), and no other 1B6/NR isolates were resistant to erythromycin supports the view that macrolide resistance developed following treatment. A high overall level of azithromycin susceptibility was confirmed by testing 67 clinical isolates: MIC 0.5 mg/L (range 0.023-0.75 mg/ L). We conclude that the long half-life of azithromycin which is beneficial in treating chlamydial infection may result in increased selective pressure for resistance in gonococci. This report also highlights the importance of antibiotic susceptibility surveillance of gonococci and stresses the need for appropriate treatment of gonococcal infection, particularly when it is prescribed outwith departments of genitourinary medicine. 90

The sensitivity of syphilis assays in detecting different stages of early syphilis.

Our aim was to determine the sensitivity of the Murex ICE enzyme immunoassay (EIA) as a screening test for early syphilis and to determine how many additional cases of infection were detected by performing additional tests when requested on clinical grounds. This was an observational study on consecutive patients diagnosed with syphilis in the Department of Genitourinary Medicine, Edinburgh between January 1st 2004 and April 1st 2005. Additional tests were performed on sera that gave a positive or equivocal EIA on screening as well as by clinical request on sera from contacts of syphilis, and those with clinical signs of syphilis. Additional tests included a Venereal Diseases Research Laboratory (VDRL) carbon antigen test, a Treponema pallidum particle agglutination (TPPA) test, INNO-LIA line immunoblot assay, and an EIA specific for anti-treponemal IgM. A total of 105 patients were diagnosed with syphilis: primary (50), secondary (26), early latent (8), and of unknown duration (21). The TPPA was the most sensitive test in primary syphilis and had a sensitivity of 96% (48/50), which was significantly higher (P <0.05) than the sensitivity of 84% (42/50) for the screening EIA: seven of the EIA negatives were detected by EIA–IgM, six by TPPA, five by immunoblot, and two by VDRL. EIA–IgM was negative in six primaries; all were positive by TPPA and immunoblot. We conclude that, in order to maximize the serological detection of primary syphilis a specific EIA–IgM test and a TPPA test should be performed whenever there is a clinical suspicion of primary infection. This is particularly important when an EIA such as Murex ICE is used as a single screening test as it is less sensitive than the TPPA in primary infection.

The outcome of oropharyngeal gonorrhoea treatment with different regimens

Little is known of the efficacy of different antibiotics for the treatment of oropharyngeal gonorrhoea in routine clinical practice. The aim of the study was to investigate the treatment outcome of oropharyngeal gonorrhoea with different antibiotics. Case-notes of culturally proven oropharyngeal gonorrhoea diagnosed between January 1998 and January 2003 were reviewed for the antibiotic of choice and the result of test-of–cure (TOC) seven and 14 days after treatment. Of 117 episodes of pharyngeal gonorrhoea, 77 episodes (66%) were followed up with one TOC and 25 (21%) had two TOC. Treatment failure was recorded in 10% (8/77) of episodes: the failure rate was 28% (4/14) in patients treated with amoxicillin 3 g/probenecid 1 g stat and 11% (4/35) in those treated with ciprofloxacin 500 mg stat. The failure rate in treating pharyngeal gonorrhoea supports the need for a pharyngeal TOC culture as part of routine follow-up for patients infected at this site. As only 66% of patients had a TOC culture, efforts should be made to increase the number of patients having a TOC.

Markers of past syphilis in HIV infection comparing captia syphilis G anti-treponemal IgG enzyme immunoassay with other treponemal antigen tests

The sensitivity of the Captia Syphilis G anti-treponemal IgG enzyme immunoassay (EIA-IgG) was compared with the Treponema pallidum haemagglutination assay (TPHA) and the Fluorescent Treponemal Antibody Absorbed (FTA-Abs) test as a marker for past syphilis in 28 HIV-infected and 31 HIV-negative patients with a past history of syphilis. The specificity of EIA-IgG was compared in 89 patients without a history of syphilis who were known to be HIV antibody positive with a control group of 89 patients who had tested HIV negative. In patients with a past history of syphilis each treponemal test (EIA-IgG, TPHA and FTA-Abs) gave a lower sensitivity (82%, 86%, 79%) in the HIV-positive group than in the HIV-negative group (97%) but the difference was significant only in the case of the FTA-Abs test (P < 0.05). In the HIV-positive patients 11% (3/28) were negative in all 3 treponemal tests while 25% (7/28) were negative in at least one treponemal test. In patients without a past history of syphilis the EIA-IgG antibody index in the HIV-positive group (0.436) was significantly higher than in the MV-negative group (0.378): the specificity, however, was similar in the HW-positive (100%) and HW-negative groups (99%). We conclude that the Captia Syphilis G anti-treponemal IgG enzyme immunoassay is of similar specificity in HIV-positive and HIV-negative patients and is of similar sensitivity to the TPHA and FTA-Abs as a marker of past syphilis in HIV-infected patients. Because HIV-infected patients may lose markers to one or more treponemal antibody tests the exclusion of past treponemal infection is more reliable if sera from such patients are tested using several different tests.

Evaluation of the Serodia Treponema pallidum particle agglutination, the Murex Syphilis ICE and the Enzywell TP tests for serodiagnosis of syphilis

We evaluated the Treponema pallidum haemagglutination assay (TPHA), a treponemal test, with three other treponemal tests, the Serodia T. pallidum particle agglutination assay, the Murex Syphilis ICE IgG + IgM enzyme immunoassay (EIA) and the Enzywell TP IgG + M EIA (a new rapid EIA) for use in conjunction with the rapid plasma reagin test (RPR), a non-treponemal test, for serodiagnosis of syphilis. In all, 124 serum samples were found reactive with RPR and/or TPHA after testing by the routine laboratory protocol. Twenty-three (18.5%) of them were positive only by RPR test and were evaluated as biologically false-positive, 16 were positive only by the TPHA and 84 by both the RPR and TPHA tests; one sample was non-specific (heterophile reaction) in the TPHA. Agreements of the TPHA with the Serodia TPPA, the Murex Syphilis ICE and the Enzywell TP tests were 96.7%, 100% and 99.1%, respectively. We conclude that each one of the tests, the Serodia TPPA, the Murex Syphilis ICE and the Enzywell TP, is an appropriate substitute for screening for serodiagnosis of syphilis.

Sensitivity of microscopy for the rapid diagnosis of gonorrhoea in men and women and the role of gonorrhoea serovars

Auditing the sensitivity of microscopic diagnosis of gonorrhoea is recommended by the current guidelines. A retrospective study was performed of 596 cases of positive cultures for Neisseria gonorrhoeae in modified New York City culture (MNYC) media diagnosed from 1995 to 1999. The sensitivity of the cervical slides in women was 51% while in men who have sex with men (MSM) the sensitivity of urethral and rectal slides were 89% and 54% respectively. The sensitivity of urethral slides in heterosexual men was 84%. Neisseria serovar 1B02 among MSM and serovar 1B31 among women were mostly undiagnosed with microscopy. Serovars 1A05, 1A21, B08 among heterosexual men were exclusively associated with negative microscopy. Microscopy is important in the rapid detection and treatment of gonorrhoea. Infections with certain serovars are less likely to be detected by microscopy; making them more likely to spread within the community. Culture from different ano-genital sites is essential to maximize detection of gonorrhoea in all patients.

Qualitative and quantitative aspects of the serological diagnosis of early syphilis

Summary: The aim of the present study was to evaluate the use of various serological tests in the diagnosis of early syphilis. The Murex enzyme immunoassay (EIA) test was used for screening; the Venereal Diseases Research Laboratory (VDRL) test, the Treponema pallidum particle agglutination assay (TPPA) and the Mercia antitreponemal IgM EIA were used in all the patients with a positive screening test and in those with suspected syphilis or in known contacts. In 89 cases of primary syphilis, the Murex EIA screening test was positive in 67 (75%) patients, the Mercia IgM EIA in 80 (90%) cases, the VDRL in 60 (67%) cases and the TPPA in 85 (96%) cases. All the tests were positive in 68 patients with secondary syphilis. In 72 cases of early latent syphilis, the Murex EIA screening test was positive in 68 (94%) patients, the Mercia IgM EIA in 50 (69%) cases, the VDRL in 61 (85%) cases and the TPPA in 68 (94%) cases. The Mercia IgM EIA was the only test positive in four (6%) of these cases; these four patients were known contacts. Antibody titres in the VDRL and TPPA increased as the infection progressed.

Rectal gonorrhoea in homosexual men: source of infection.

The objective of this retrospective study was to determine the possible source of infection in homosexual men with rectal gonorrhoea: the probable source of rectal gonorrhoea was identified in 46/155 cases. Although the urethra was the site of infection in 33 (72%) of these contacts, only pharyngeal gonorrhoea was identified in 9 (20%) men. In 25/26 cases, there was concordance in the auxo/serotypes of Neisseria gonorrhoeae between contacts with urethral gonorrhoea and the index men with rectal gonorrhoea. Eleven out of 12 pharyngeal isolates were of the same auxo/serotype as the index cases. This study supports the hypothesis that rectal gonorrhoea in homosexual men can be acquired from the oropharynx. Because infection at this site is an independent risk factor for acquisition of HIV, screening for rectal and pharyngeal gonorrhoea should be offered to men who have sex with men, even when there is no history of unprotected receptive anal intercourse.

A new recombinant antigen latex agglutination test (syphilis fast) for the rapid serological diagnosis of syphilis

We report an assessment of Syphilis Fast, a new latex test that uses a pool of 3 recombinant Treponema pallidum antigens (TpN15, TpN17, and TpN47) for the serodiagnosis of syphilis. Specificity was evaluated by screening 1518 unselected blood specimens in parallel with Syphilis Fast, the Captia SelectSyphG EIA and the Venereal Disease Research Laboratory (VDRL) cardiolipin antigen test while sensitivity was tested using a panel of 99 treponemal sera (treated and untreated) representing various stages of infection and 15 treponemal sera detected on screening. The specificity of Syphilis Fast on initial testing (99.8%) was significantly higher (P 0.02) than that of Captia SelectSyph-G (99.2%) and the VDRL (99.1%): the specificity of Syphilis Fast remained significantly higher (P 0.02) after repeat testing (respective values 99.9%, 99.5% and 99.4%). There was no difference in the sensitivity of Syphilis Fast and Captia SelectSyph-G on initial (93% vs 92.1%) or repeat (95.6% vs 94.7%) testing: both were significantly more sensitive (P 0.001) than the VDRL (46.5% on initial and 43.9% on repeat testing). The sensitivities of the Treponema pallidum haemagglutination test (TPHA) and FTA-abs were 98.2% and 95.6% respectively. Negative reactions in Syphilis Fast and SelectSyph-G were associated with treated infections and correlated with low TPHA titres (80). We conclude that Syphilis Fast is a highly specific, simple and fast screening test with a sensitivity comparable to native antigen treponemal tests and that it merits consideration as a front-line screening test.

Genital infection in male partners of women with chlamydial infection

The aim of the present study was to examine the prevalence of infection among male contacts of women with endocervical chlamydiae. The study population consisted of men who attended the Department of Genitourinary Medicine at Edinburgh Royal Infirmary as named contacts of women with endocervical chlamydiae. The diagnosis of Chlamydia trachomatis was based on a polymerase chain reaction. Of 632 male contacts of 404 infected women, 155 (24%) attended the clinic, and 147 had satisfactory tests for chlamydiae; 64 (44%) men had chlamydial infection. A greater proportion of symptomatic men (14/22) were infected compared with asymptomatic men (50/125) (P<0.02). Symptomatic men attended the department earlier (median 0.0 days) than asymptomatic male contacts (median 11 days) (P<0.05). A greater proportion of male contacts of women with one partner (105/254) attended the clinic than those of women with two or more partners (42/112). Better counselling policies for chlamydial infection are needed to ensure improved rate of diagnosis and treatment of male contacts.