Modification of Syphilitic Genital Ulcer Manifestations by Coexistent HIV Infection : Sexually Transmitted Diseases

Secondary Logo

Journal Logo


Modification of Syphilitic Genital Ulcer Manifestations by Coexistent HIV Infection


Author Information
Sexually Transmitted Diseases 28(8):p 448-454, August 2001.
  • Free



Conflicting data exist regarding whether HIV infection leads to changes in the clinical manifestations and severity of genital ulcer disease (GUD).


To determine the impact of HIV on the etiology and clinical severity of GUD.

Study Design 

From July 1990 to July 1992, consecutive patients presenting to the two Baltimore City Health Department (BCHD) Sexually Transmitted Diseases clinics were approached as candidates for enrollment in a prospective study to determine factors associated with the transmission and acquisition of sexually transmitted diseases (STDs).


Of the 1368 patients who presented to the BCHD, 214 (16%) had genital ulcerations: 160 (21%) of 757 men and 54 (9%) of 611 women. Among the patients with GUD who had undergone HIV testing, 28 (14%) of 204 were infected with HIV: 25 (17%) of 151 men and 3 (6%) of 53 women. Although both groups–those infected with HIV and those not infected with HIV–presented with GUD of similar duration (10 versus 11 days;P = 0.17), multiple lesions were found more frequently in men with HIV infection than in uninfected men: 87% versus 62% (P = 0.02). Although not statistically significant, GUD in men with HIV infection more often were deep (64% versus 44%, respectively) rather than superficial (36% versus 57%, respectively;P = 0.08), and larger (505 mm 2 versus 109 mm 2 ;P = 0.06). Primary syphilis caused more GUD among men with HIV infection than among uninfected men: 9 (36%) of 25 versus 24 (19%) of 126, respectively (P < 0.01). Secondary syphilis was diagnosed with concomitant GUD more frequently among men with HIV infection than among uninfected men: 3 (13%) of 25 versus 3 (2%) of 123, respectively (P < 0.01).


In this study, patients who presented with GUD were more likely to be infected with HIV. A higher proportion of men with HIV infection had multiple lesions, and the lesions were more likely to be caused by syphilis.

IT HAS BEEN SUGGESTED that clinical manifestations of genital ulcer disease (GUD) in patients with HIV infection follow an accelerated course or a more florid development than in patients without HIV infection. 1–6 Some of the earliest reports of patients with AIDS described unusually severe anorectal herpes infections refractory to treatment among men who engage in sex with men. 4 According to a multivariate analysis of data from a large prospective US study of early syphilis, the time required for healing of chancres among patients infected with HIV was longer than among patients not infected with HIV, although the difference was not statistically significant. 7 Similarly, a Baltimore study reported that individuals infected with HIV presented more often in the secondary stage of syphilis, and that they were more likely to have secondary syphilis with resolving chancres than patients who had syphilis but no HIV infection. 8

A study from Malawi of 677 men with GUD mainly from syphilis and chancroid reported impaired genital ulcer healing among patients infected with HIV. 9 Likewise, HIV-related immunologic impairment makes it biologically plausible that syphilis and other causes of GUD may follow a more aggressive course in persons with HIV infection. According to reports, for example, GUD caused by herpes simplex virus (HSV) recurs more frequently among patients with HIV infection as their immune status declines. 10–12 Similarly, in rabbits infected with Treponema pallidum, immunosuppression accelerates both the rate of increase and the maximal concentrations of treponemes in lesions. 13

To further evaluate the impact of HIV on the etiology and clinical severity of GUD, we prospectively studied the behavioral risk profile, the microbiologic etiology, and the clinical manifestations of GUD among patients infected with HIV compared with patients not infected with HIV presenting to two metropolitan sexually transmitted disease (STD) clinics.


Patient Population

As part of a prospective study evaluating the transmission and acquisition of STDs as well as condom use (known as the TRAC Study), consecutive patients who presented to full-time study clinicians at the Baltimore City Health Department (BCHD) Sexually Transmitted Diseases clinics for evaluation of new complaints or for treatment as contacts to STDs were approached as candidates for study enrollment. The study was conducted from July 1990 through July 1992. Procedural details of this study have been published elsewhere. 14 The study was approved by the internal review board on human subjects at The Johns Hopkins University School of Medicine and by the BCHD.

Patient Evaluation

Patients enrolled in the study consented to answer a 40-minute questionnaire, to undergo a clinical examination on the day of enrollment, and to return at 3-month intervals for similar follow-up evaluation over the next year. The questionnaire included a detailed history of the onset, severity, and possible self-treatment of genital ulcerations or presenting problems; current sexual practices as well as the number and types of sexual partners in the past, focusing primarily on the preceding 30 days; history of STDs; and drug and alcohol use. All the participants were questioned regarding their history of specific STDs (e.g., syphilis) and more general STD categories (e.g., genital ulcers).

All the participants were evaluated for prevalent STDs, which included a directed physical examination to detect any abnormalities of the skin, lymph nodes, abdomen, and genitalia. The study clinicians were trained, according to a standard set of clinical photographs, to classify genital ulcerations as shallow if they appeared to be limited to the epidermis and deep if they appeared to involve the dermis. 15

Serologic Testing

Serologic tests for syphilis used the rapid plasma reagin (RPR) card screening test (Macro-Vue, BBL, Cockeysville, MD) and the fluorescent treponemal antibody-absorption confirmatory test (FTA-ABS; Zeus Scientific, Inc., Raritan, NJ). These tests were performed in the BCHD laboratory on sera acquired at each patient’s visit, in accordance with standard procedures. 16 All the sera were analyzed for the HIV antibody, according to standard procedures, using commercially available enzyme-linked immunosorbent assays (ELISA) (Bio-Enzabead HIV Immunoassays; Organon-Teknika, Charleston, SC). 17 For the measurement of T-cell subsets, heparinized whole blood was stained with monoclonal antibodies using a modified whole blood method, and percentages of CD3 + , CD4 + , and CD8 + T cells were determined by flow cytometry. 18

Serologic evidence of HSV-2 infection, determined by Western blot analysis, was based on reactivity with the 92-kD gG-2 glycoprotein band pattern. This pattern was previously shown to be specific for HSV-2. 19 A patient presenting with a genital ulcer and no antibodies to gG-2 at that visit, who 3 to 6 months later gave serologic evidence of antibodies to gG-2, was defined as a HSV-2 seroconverter.

Genital Ulcer Evaluation

When lesions were detected, standardized forms were used to record their appearance, character, depth, number, and size. Photographs also were taken if the study participant consented. Three darkfield examinations were performed to detect spirochetes in fluid obtained from the lesion base. A history of syphilis infection was obtained by patient self-report, clinic medical record review, and a search of state and local syphilis registries by health department disease intervention specialists.

Genital Ulcer Disease Definitions

Genital ulcer disease was defined as a lesion or lesions present on physical examination that were characterized by any break or discontinuity in the genital epithelium. The etiology of each genital ulceration was evaluated using darkfield microscopy and cultures for HSV, Hemophilus ducreyi, and other bacteria or fungi.

Primary syphilis was diagnosed in a participant with no syphilis history if a genital lesion/ulcer was noted and spirochetes consistent with T pallidum were identified on darkfield microscopy examination, or if a genital ulcer was noted and the FTA-ABS was reactive. In a patient with a history of syphilis, primary syphilis was defined if a lesion was present and darkfield examination identified spirochetes, or if a lesion was present and serologic testing demonstrated a reactive FTA-ABS and a fourfold rise in RPR titer. Secondary syphilis with genital ulceration was diagnosed in patients who presented with an ulceration, a rash compatible with secondary syphilis, reactive RPR/FTA-ABS tests, and either positive darkfield microscopy, or in patients with prior syphilis, a documented fourfold rise in RPR titer.

A patient with a genital lesion and a positive culture for HSV or seroconversion of HSV-2 at the next study follow-up visit was considered to have initial HSV-2 infection.

Genital Ulcer Microbiologic Evaluation

Cultures were then taken from the lesion base for herpes simplex virus, H ducreyi, and other bacteria and fungal species. Specimens taken with Dacron swabs for HSV culture were placed in a veal infusion transport medium broth supplemented with glycerol g-1, transported to the laboratory, centrifuged, and inoculated onto a MRC-5 cell tissue culture system within 24 hours of collection. 20 The tissue culture system was evaluated daily for cytopathic effect. When a cytopathic effect was observed, the cells were scraped off the wells and stained with type-specific monoclonal immunofluorescent reagents specific for HSV-1 and HSV-2. Swabs for culture of H ducreyi from genital ulcer bases were obtained by vigorously swabbing the margins of the ulcer and ulcer base. Lesion exudate was obtained to the point of saturating the swab, which then was used to inoculate the culture plate heavily. Biplates were provided for culture, which on one side contained Mueller-Hinton agar base supplemented with 5% horse blood, 1% IsovitaleX, and 3 μg/ml vancomycin, and on the other side contained GC agar base supplemented with 2% bovine hemoglobin, 5% fetal calf serum, 1% IsovitaleX, and 3 μg/ml vancomycin. Growth of H ducreyi was confirmed using Gram stain, nitrate reduction, oxidase tests, and catalase tests. 21

Statistical Analysis

The 6.12 Version of SAS Windows software was used for data analysis. Either χ 2 with appropriate degrees of freedom or a two-tailed Fisher’s exact test was used to identify the relation of each behavioral and clinical factor to prevalent GUD, risk behaviors among men with GUD, and HIV infection status. The same analysis was used to define the relation of clinical presentations and GUD etiologies to prevalent HIV infection. 22 Descriptive statistics and T statistics for equal or unequal variance are given, as appropriate, for age, number of sex partners in the preceding 30 days, number of days between noticing the lesion and coming to the clinic, and largest lesion area.


During the study period, 1368 clinic attendees (757 men and 611 women) enrolled and underwent complete physical examinations. Genital ulcerations were observed in 214 of the 1368 patients (15.6%): 160 (21.1%) of 757 men and 54 (8.8%) of 611 women. Consent for HIV testing was given by 1310 (94.5%) of the patients, 119 (9%) of whom were HIV-positive: 89 (12%) of 719 men and 30 (5%) of 591 women. Among the patients with GUD who consented to HIV testing, 28 (14%) of 204 were HIV-positive: 25 (17%) of 151 men and 3 (6%) of 53 women. In comparison, 91 (8%) of 1106 patients with HIV infection but no genital ulcerations were HIV-positive (P = 0.01). Because this study involved only a small number of women with GUD, especially women who were HIV-positive, this report concentrates on the 151 men with GUD who consented to HIV testing.

Characteristics of Men With Genital Ulcer Disease by HIV Status

Men with HIV infection who presented to the clinics with GUD were similar to uninfected men with GUD in terms of age (30.5 versus 27.8 years;P = 0.156) (Table 1), number of sexual partners in the preceding 30 days (1.4 versus 1.6;P = 0.187), and self-report of previous genital herpes (4% versus 6%;P = 1.0). A self-reported history of prior syphilis, however, was more frequent among patients with HIV infection than among uninfected patients (mean, 38% versus 8%;P ≤ 0.001). Men with HIV infection and GUD reported high-risk behaviors more often than uninfected men with GUD (Table 1). Intravenous drug use was more common among men with HIV infection than among uninfected men (40% versus 10%;P < 0.001). Similarly, a much higher proportion of men with HIV infection reported sexual contact with another person in the past than uninfected men (32% versus 4.8%;P ≤ 0.001). Men with HIV infection did not differ from uninfected men in terms of crack use (32% versus 31%;P = 0.9; data not shown), use of other nonparenteral drugs (32% versus 31%;P = 0.9), or payment for sex with drugs or money (25% versus 15%;P = 0.5; data not shown).

Table 1:
Demographic and Risk Behavior Characteristics of Men With Genital Ulcer Disease, Stratified by HIV Infection Status

Etiology of Genital Ulcer Disease Among Men by HIV Status

Primary syphilis was a more common cause of GUD among men with HIV infection than among uninfected men: 9 (36%) of 25 versus 24 (19%) of 126 (Table 2). Secondary syphilis was diagnosed with concomitant GUD more frequently among men with HIV infection than among uninfected men: 3 (13%) of 25 versus 3 (2%) of 123 (P < 0.01). Among the 121 patients with HSV cultures, HSV-2 was more commonly isolated from lesions of men who were not infected with HIV than from men with GUD who were HIV infected: 50 (49%) of 101 versus 3 (15%) of 20 (P < 0.01) (Table 2). Among 149 men with HSV-2 serology tested at enrollment, 47% (59/125) of men without HIV infection were HSV-2 seropositive and 38% (9/24) of men with HIV infection were seropositive (P = 0.38). Among 70 men for whom paired sera was available, HSV-2 seroconversion was documented in an equal proportion of men infected with HIV and uninfected men: 3 (7%) of 9 versus 14 (7%) of 61 (P = 0.7) (Table 2). Also, HSV-2 was identified by either positive culture or seroconversion more frequently among men with no HIV infection than among men with HIV infection (44% versus 8%;P = 0.02). No H ducreyi was isolated from any genital ulcer. Genital ulcer disease could not be attributed to a specific STD in similar proportions of men with HIV infection and uninfected men (32% versus 35%;P = 0.7). Other organisms such as staphylococcal species and organisms associated with normal skin flora were isolated from GUDs among all patients except one person with HIV infection.

Table 2:
Etiologic Factors of Genital Ulcer Disease Among Men, Stratified by HIV Infection Status

Clinical Characteristics of Genital Ulcer Disease Among Men by HIV Serostatus

Both men with HIV infection and uninfected men reported similar duration of lesions before presenting to the clinic (10 days versus 11 days;P ≤ 0.17) (Table 3). Although men with HIV infection presented more often with shallow to deep ulcers than uninfected men (64% versus 44%;P = 0.08), and with lesions of greater mean size (505 mm 2 versus 109 mm 2 ;P = 0.06), these differences were not significant. Men with HIV infection also were more likely to present with two or more lesions than uninfected men (87% versus 62%;P = 0.02). The mean CD4 cell count among men with HIV infection and GUD was 664 ± 534 cells/mm 2 .

Table 3:
Clinical Characteristics of Genital Ulcer Disease Among Men, Stratified by HIV Infection Status

Clinical characteristics of GUD resulting from syphilis were similar to those for GUD in general (Table 4). Men with GUD resulting from syphilis, both those infected and those not infected with HIV, noticed their ulcers at the same time before presentation (12.9 versus 12.5 days;P = 0.9). Among men with HIV infection and syphilitic GUD, lesions tended to be deeper than among uninfected men (83% versus 65%;P = 0.4), more frequently multiple (83% versus 52%;P = 0.08) and larger (404 mm 2 versus 201 mm 2 ;P = 0.2), but none of these differences were statistically significant. In similar analyses of men with GUD resulting from HSV-2, stratified by HIV status, as compared with men whose GUD resulted from neither syphilis nor HSV-2, no differences were noted regarding lesion depth, number, or size (data not shown).

Table 4:
Clinical Characteristics of Genital Ulcer Disease Due to Syphilis Among Men, Stratified by HIV Infection Status


In this study, patients who presented to the Baltimore City Health Department STD clinics with GUD were more likely to be HIV infected, and genital ulcers among men with HIV infection were more likely to be syphilitic than herpetic. Clinically, men with HIV infection presented more frequently than uninfected men with multiple ulcers, and although a greater percentage of men infected with HIV presented with deeper and larger ulcerations, these observations were not statistically different from those among uninfected men with GUD. No differences in clinical severity were noted when men were stratified by cause of GUD.

Increased clinical severity of genital ulcers resulting from syphilis in patients with HIV infection was reported previously in a prospective syphilis treatment trial. As in the current study, however, the difference in severity was not statistically significant when the patients were stratified by HIV serostatus. 7 In a Malawi STD clinic, genital ulcers resulting primarily from syphilis and chancroid were slower to heal among HIV-infected patients compared to HIV-uninfected uninfected patients. 9 In the current study, men presented with similar durations of genital lesions regardless of HIV status, but no prospective data on time required for healing were collected. These cross-sectional data represent a population of US men in whom chancroid infection was not detected and HIV infection was not far advanced, as indicated by relatively high CD4 cell counts. Such factors may have influenced the current observation that although GUD among men infected with HIV appeared more clinically severe than GUD among HIV-uninfected men, the difference in degree of severity was not great.

As previously reported, the overall seroprevalence of HIV infection among patients presenting to our clinics during the current study was approximately 9%. 23 In this study, 28 (14%) of 204 of patients with GUD were HIV infected. This high HIV-1 seroprevalence was mainly among men rather than women: 23 (16%) of 146) versus 3 (5%) of 55. However, these gender results may be biased by the smaller number of women than men who notice genital ulcers and report to the clinic for evaluation, particularly for syphilis, as shown previously. 24 Nevertheless, the total number of women in the current study was too small for meaningful analysis. The analysis therefore concentrated on men. As expected and reported in prior studies, men with GUD and HIV coinfection frequently admitted to high-risk behavior, such as intravenous drug use and sex with men, and to a history of syphilis. 3,8,23

This study also demonstrated that among men presenting to the BCHD STD clinics with genital ulcerations, men infected with HIV were more likely to have syphilis and less likely to be culture positive for herpes simplex virus than HIV-uninfected men. Although the etiology of GUD may vary geographically, this observation was not expected because HSV generally is believed to be a commonly recurring infection among individuals infected with HIV. 10,12 Furthermore, primary and secondary syphilis rates in the city of Baltimore were relatively low during the early 1990s when this study was conducted. Perhaps these results reflect a bias that men with suspected syphilitic ulcerations are more likely to visit STD clinics for evaluation, or that syphilis is more accurately diagnosed in them because diagnostic tests, such as darkfield microscopy, are immediately available. Another possible explanation may be that these patients with HIV infection and infectious syphilis represented a high-risk core group and the first wave of Baltimore’s future syphilis outbreak.

Men infected with HIV and genital ulcers resulting from syphilis were more likely to have secondary syphilis with concurrent primary chancres men without HIV infection. These results are similar to those of other cross-sectional reports from the BCHD STD clinics and the multicenter US syphilis treatment trial. 7,8 Other investigators have suggested that syphilis may progress more rapidly in patients with HIV infection, and that signs and symptoms of infection are more florid in such persons. 1–3,25,26 The current data from a large population of patients support this hypothesis. Because of insufficient data, it could not be determined specifically whether the observed changes were because of more rapid progression from primary to secondary syphilis, or whether the persistence of chancres in patients with HIV infection and secondary syphilis resulted from delayed healing of primary lesions. However, the time since the patient first noticed his lesions were the same for both men with HIV infection and HIV-uninfected men (12.9 versus 12.5 days). This suggests a more rapid progression from primary to secondary syphilis among patients with HIV infection. Qualitative immunologic changes in patients with HIV infection may lead to more rapid dissemination of treponemes from primary lesions and earlier development of secondary lesions. Furthermore, these immunologic changes could lead to delayed healing of primary lesions. Marra et al 27 showed delayed healing of syphilitic chancres in macaques infected with simian immunodeficiency virus. Also among humans, men with HIV infection and GUD attending an STD clinic in Malawi had slower ulcer healing than men with no HIV infection. 9

Although it has been assumed that individuals with HIV infection present with more severe signs and symptoms of GUD, the current study is among the few documenting this increased severity regarding numbers of lesions and suggesting that lesions may be deeper and larger. The genital ulcers observed among men with HIV infection visiting these STD clinics were mainly the result of newly acquired syphilis, not HSV infection. This observation may be biased because men with HIV infection may not present to care providers for treatment of HSV ulcerations diagnosed previously and recognized as recurrent. Furthermore, the mean CD4 cell count among 17 of the 25 men with HIV infection and genital ulcerations was 664 (range, 34–1355 CD4 cells). This exceeds the range of less than 200 generally associated with frequent HSV clinical recurrences. 28 A specific etiology could not be found for more than 30% of the genital lesions, and this did not differ by HIV status. These data do not differ from those previously reported in several studies among men and women from various geographic regions. 29–32 Even when newly developed polymerase chain reaction techniques are used to identify T pallidum, H ducreyi, and HSV in lesion exudate, the etiology of genital lesions remains unknown in 20% to 30% of cases. 32–34 Further studies are needed not only to determine the cause of these lesions, but also their relation to HIV infection.

The observation that more than 50% of the genital ulcerations in men with HIV infection were caused by newly acquired syphilis has significant public health importance. These men have self-reported histories of high-risk behavior, have HIV infection, are maintaining their high-risk behaviors, and most likely are the most efficient transmitters of HIV infection via sexual contact. 35 The development of risk-reduction messages targeting this group is crucial in the control of HIV infection. Prompt identification of their sexual partners through traditional contact tracing has been reportedly inefficient. 36 New methods to identify these contacts and treat them for incubating syphilis and possibly, in the future, for HIV infection are urgently needed to curtail HIV transmission. The opportunity to identify, treat, and counsel these patients should be regarded as a crucial component of HIV prevention.


1. Radolf JD, Kaplan RP. Unusual manifestations of secondary syphilis and abnormal humoral immune response to Treponema pallidum antigens in a homosexual man with asymptomatic human immunodeficiency virus infection. J Am Acad Dermatol 1988; 18: 423–428.
2. Musher DM, Hamill RJ, Raughn RE. Effect of human immunodeficiency virus (HIV) infection on the course of syphilis and on the response to treatment. Ann Intern Med 1990; 113: 872–881.
3. Tramont EC. Syphilis in the AIDS era. N Engl J Med 1987; 316: 1600–1601.
4. Siegal FR, Lopez C, Hammer GS, et al. Acquired immunodeficiency in male homosexuals manifested by chronic perianal ulcerative herpes simplex lesions. N Engl J Med 1988; 305: 1439–1443.
5. LaGuardia KD, White MH, Saigo PE, Hoda S, McGuinness K, Ledger WJ. Genital ulcer disease in women infected with human immunodeficiency virus. Am J Obstet Gynecol 1995; 172: 553–561.
6. Abeck D, Echert F, Korting HC. Atypical presentation of coexistent Haemophilus ducreyi and Treponema pallidum infections in an HIV-positive male. Acta Derm Venereol 1992; 72: 37–38.
7. Rolfs RT, Joesoef MR, Hendershot EF, et al. A randomized trial of enhanced therapy for early syphilis in patients with and without human immunodeficiency virus syndrome. N Engl J Med 1997; 337: 307–314.
8. Hutchinson CM, Hook EW III, Shepherd M, Verley J, Rompalo AM. Altered clinical presentation of early syphilis in patients with human immunodeficiency virus infection. Ann Intern Med 1994; 121: 94–99.
9. Behets FM, Liomba G, Lule G, et al. Sexually transmitted diseases (STDs) and human immunodeficiency virus control in Malawi: a field study of genital ulcer disease. J Infect Dia 1995; 171: 451–455.
10. Safrin SA, Kemmerly S, Plotkin B, et al. Foscarnet-resistant herpes simplex virus infection in patients with AIDS. J Infect Dis 1994; 169: 193–196.
11. Elrich KS, Mills J, Chatis P. Acyclovir-resistant herpes simplex virus infection in patients with the acquired immunodeficiency syndrome. N Engl J Med 1098; 320:293–296.
12. Augenbraun M, Feldman J, Chirgwin K, et al. Increased genital shedding of herpes simplex virus type 2 in HIV-seropositive women. Ann Intern Med 1995; 123: 845–847.
13. Lukehart SA , Baker Zander SA, Lloyd RM, Sell S. Characterization of lymphocyte responsiveness in early experimental syphilis. J Immunol 1980; 124: 461–467.
14. Upchurch DM, Weisman CS, Shepherd M, et al. Interpartner reliability of reporting of recent sexual behaviors. Am J Epidemol 1991; 134: 1159–1166.
15. Schmid GP, Schalla WO, DeWitt WE. Chancroid. In: Morse SA, Moreland AA, Thompson SE, eds. Atlas of Sexually Transmitted Diseases. Philadelphia: JB Lippincott, 1990.
16. Larsen SA, Hunter EF, Kraus SJ, eds. A manual of tests for syphilis. 8th ed. Washington DC: American Public Health Association, 1990.
17. Update: serologic testing for antibody to human immunodeficiency virus. MMWR Morb Mortal Wkly Rep 1988; 36:833–840, 845.
18. Giorgi JV, Cheng HL, Margolick JB, et al. Quality control in the flow cytometric measurement of T-lymphocyte subsets: the Multicenter AIDS Cohort experience. Clin Immunol Immunopathol 1990; 55: 173–186.
19. Ashley RI, Miltoni J, Lee F, Nahmias A, Corey L. Comparison of Western blot and glycoprotein g-specific immunodot enzyme assay for detecting antibodies to herpes simplex virus 1 and 2 in human sera. J Clin Microbiol 1988; 26: 662–667.
20. Corey L, Adams HG, Brown ZA, Holmes KK. Genital herpes simplex virus infections: clinical manifestations, course, and complications. Ann Intern Med 1983; 98: 958–972.
21. MacDonald K, Cameron DW, Irungu G, et al. Comparison of Sheffield media with standard media for the isolation of Haemophilus ducreyi. Sex Transm Dis 1989; 16: 88–90.
22. Rosner B. Fundamentals of Biostatitics. Boston: Duxbury Press, 1982.
23. Quinn TC, Glasser D, Cannon RO, et al. Human immunodeficiency virus infection among patients attending clinics for sexually transmitted diseases. N Engl J Med 1988; 318: 197–203.
24. Hutchinson CM, Rompalo AM, Reichart CA, Hook EW III. Characteristics of patients with syphilis attending Baltimore STD clinics. Arch Intern Med 1991; 151: 511–516.
25. Johns DR, Tierney M, Feistenstein D. Alteration in the natural history of neurosyphilis by concurrent infection with the human immunodeficiency virus. N Engl J Med 1987; 316: 1569–1572.
26. Lukehart SA, Hook EW III, Baker-Zander SA, et al. Invasion of the central nervous system by Treponema pallidum: implications of diagnosis and treatment. Ann Intern Med 1988; 109: 855–863.
27. Marra CM, Handsfield HH, Kuller L, Morton WR, Lukehart SA. Alterations in the course of experimental syphilis associated with concurrent simian immunodeficiency virus infection. J Infect Dis 1992; 165: 1020–1025.
28. Hanson DL, Chu SY, Farizo KM, Ward JW. Distribution of CD4+ lymphocytes at diagnosis of acquired immunodeficiency syndrome-defining and other human immunodeficiency virus-related illnesses. The Adult and Adolescent Spectrum of HIV Disease Project Group. Arch Intern Med 1995; 155: 1537–1542.
29. Plummer FA, D’Costa LJ, Msanze H, et al. Clinical and microbiologic studies of genital ulcer in Kenyan women. Sex Transm Disease 1985; 12: 193–197.
30. O’Farrell N, Hoosen AA, Coetzee KD, Van den Ende J. Genital ulcer disease in Durban, South Africa. Genitourin Med 1991; 67: 322–326.
31. Mabey DC, Wall RA, Bello CS. Aetiology of genital ulceration in the Gambia. Genitoruin Med 1987; 63: 312–315.
32. Risbud A, Chan-Tack K, Gadkari D, et al. The etiology of genital ulcer disease by multiplex polymerase chain reaction and relationship to HIV infection among patients attending sexually transmitted disease clinics in Pune, India. Sex Transm Dis 1999; 26: 55–62.
33. Orley KA, Gates CA, Martin DH, Body BA, Weiss JB. Simultaneous PCR detection of Haemophilus ducreyi, Treponema pallidum, and herpes simplex virus types 1 and 2 from genital ulcers. J Clin Microbiol 1996; 34: 49–54.
34. Morse SA, Trees D, Htun Y, et al. Comparison of clinical diagnosis and standard laboratory and molecular methods for the diagnosis of genital ulcer disease in Lesotho: association with human immunodeficiency virus infection. J Infect Dis 1997; 174: 583–589.
35. Wasserheit JM. Epidemiological synergy: interrelationship between human immunodeficiency virus infection and other sexually transmitted diseases. Sex Transm Dis 1992; 19: 61–67.
36. Gibson JJ, Lindman T. Cost effectiveness of contact tracing versus screening to find syphilis cases: further study is needed. Sex Transm Dis 1996; 23: 441–443.
© Copyright 2001 American Sexually Transmitted Diseases Association