A McMillan

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

Evaluation of ligase chain reaction for the non-cultural detection of rectal and pharyngeal gonorrhoea in men who have sex with men.

Objectives: To compare a nucleic acid amplification test (ligase chain reaction) with culture for detecting rectal and pharyngeal gonorrhoea in men who have sex with men (MSM). Methods: Duplicate rectal and throat swabs from MSM attending a genitourinary medicine clinic were collected for culture on modified New York City medium and detection of gonococcal nucleic acid by the Abbott ligase chain reaction (LCR) utilising probes based on opa 1 gene sequences. LCR positive culture negative specimens were tested by a second LCR utilising probes based on pilin gene sequences. Patients with rectal and/or pharyngeal cultures yielding Gram negative diplococci confirmed as Neisseria gonorrhoeae by biochemical and immunological methods were diagnosed with rectal and/or pharyngeal gonorrhoea. The criteria for diagnosing rectal and pharyngeal infection by LCR included a positive opa LCR with a positive culture from the same site or, in the case of a negative culture, a positive opa LCR and a positive pilin LCR. Results: Duplicate rectal samples were obtained from 227 MSM. The results of LCR and culture were concordant in 219 samples (96.5%). The prevalence of rectal gonorrhoea by LCR and culture was 7.0% (16/227) and 4.0% (9/227), respectively. Duplicate throat samples were obtained from 251 MSM. The results of LCR and culture were concordant in 230 (91.6%) cases. The prevalence of pharyngeal gonorrhoea by LCR and culture was 12.7% (32/251) and 6.0% (15/251), respectively. The specificity of LCR was 99.5% (210/211) for rectal and 98.2% (215/219) for pharyngeal specimens. Conclusions: The high prevalence and asymptomatic nature of pharyngeal and rectal gonococcal infection suggests that routine screening for infection at these sites by a nucleic acid amplification test method such as LCR should be considered as part of the overall strategy to control gonorrhoea in MSM.

Screening for treponemal infection by a new enzyme immunoassay.

A new enzyme immunoassay (EIA, Captia Syphilis-G) for detecting IgG antibodies against Treponema pallidum was evaluated as a screening test for syphilis. When serum samples were tested at a dilution of 1 in 20 (EIA20), the overall agreement between the IgG EIA and serological status based on the T pallidum haemagglutination assay (TPHA) and the fluorescent treponemal antibody absorption (FTA-ABS) test was 99.2% (1310/1321). The sensitivity of the EIA20 was 98.4% (60/61) and the specificity 99.3% (1251/1260). Discrimination between patients with and without treponemal infection was good: the mean EIA20 absorbance ratios (patient/mean low titre positive control results) were 0.49 for antibody negative patients, 3.30 for patients with positive Venereal Diseases Research Laboratory (VDRL) test and TPHA results, and 1.77 for patients with negative VDRL but positive TPHA results. The cut off point for excluding treponemal infection was taken as 0.9. Specimens with ratios of more than 0.9 should be confirmed by the FTA-ABS test and evaluated for specific IgM antibodies to treponemes. When serum samples were tested at a 1 in 50 dilution (EIA50) the sensitivity was lower (80.3%) but the specificity was absolute. The reduction in sensitivity correlated with low absorbance ratios in the patients who were VDRL negative and TPHA positive. The screening performance of the IgG EIA20 is thus comparable with that provided by a combination of the VDRL test and TPHA. The potential for automation makes the EIA an attractive alternative, particularly in larger centres. Alternatively, the test can be performed at a 1 in 50 dilution (EIA50), at which level it is ideally suited for confirming the treponemal status of antibodies in serum samples preselected by positive cardiolipin antigen screening test results.

Evaluation of an enzyme-linked immunosorbent assay for the detection of antibody to Trichomonas vaginalis in sera and vaginal secretions.

Using a whole-cell antigen antibody to Trichomonas vaginalis was measured by an enzyme-linked immunosorbent assay (ELISA). IgG antibody was found in sera from only three of 99 children under 12 years of age. In contrast, serum IgG or IgM antibody or both were detected in 80.4% of women who had vaginal trichomoniasis and in 13.7% of uninfected women. Although antibody was found in cervical and vaginal secretions, the correlation between current infection and the presence of antibody was poorer than found between circulating antibody and infection. IgG or IgA antibody or both was detected in the secretions of 73.2% and 41% of infected and uninfected women respectively. This may be accounted for, at least partly, by previous infections since antibody, circulating or local, was found most often in women who had a history of trichomoniasis. There was no indication that some other vaginal micro-organism stimulated antibody directed against T vaginalis.

An immunohistological study of spontaneous regression of Condylomata acuminata

An immunohistological study of four men whose perianal warts were undergoing spontaneous regression was undertaken, and the results compared with those obtained from non-regressing condylomata from six men. CD4+ and CD8+ cells were noted in the stroma of each wart, but there was no clear difference in the density of the infiltrate between regressing and non-regressing warts. Natural killer cells (CD16+ and CD57+) were only noted in the stroma and epidermis of regressing warts. Possible immunological mechanisms of regression of condylomata acuminata are discussed.

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.

Serum immunoglobulin response in uncomplicated gonorrhoea.

Sera from 225 men and 140 women were examined by an indirect immunofluorescent antibody technique for antibody reactive with Neisseria gonorrhoeae. Antigonococcal IgM was demonstrated at a titre of greater than or equal to 16 in about 45% of infected, but in only 3% of non-infected, patients. Most of this antibody occurred in sera of patients who had been infected for less than 14 days. Antibody of the IgA class was found at a titre of greater than or equal to 16 in over half the infected, but in none of the non-infected, patients. IgG antibody reactive with the gonococcus was found in each infected patient at a titre of greater than or equal to 16 but in only 8% of controls. The mean log titre of this antibody was significantly higher in patients who had been infected for more than seven days than in those whose infection was of shorter duration.

Gonorrhea in the homosexual man: frequency of infection by culture site.

The aims of this study were to determine the frequencies of infection with Neisseria gonorrhoeae at various sites in homosexual men who were attending clinics for treatment of sexually transmitted diseases in central Scotland and to appraise the diagnostic tests used. Specimens for culture were taken from the urethra, pharynx, and anorectum of every homosexual man in the study. When the first cultures of pharyngeal and rectal specimens were negative, these cultures were repeated twice at weekly intervals. The urethra was infected in 169 (60.8%), the anorectum in 114 (41.0%), and the pharynx in 23 (8.3%) of 278 patients who had gonorrhea. By reliance on only one set of tests, eight (7.0%) of 114 patients who had rectal gonorrhoea and six (26.1%) of 23 patients with pharyngeal infection would have been missed. The results indicate the importance of obtaining specimens for culture from all sites that might possibly be infected, regardless of the symptoms.