MOST COUNTRIES IN WESTERN EUROPE noted a decline in the incidence of gonorrhea during the 1970s. The decline accelerated during the 1980s and remained in most of these countries during the early 1990s.1 However, an increase in the incidence of gonorrhea, as well as in other sexual transmitted infections (STIs), has been reported in many Western European countries during the second half of the 1990s and the beginning of the 2000s.2 The increase has been particularly accentuated in men who have sex with men (MSM), who account for a disproportionately large burden of gonorrhea in several countries, including Sweden, Denmark, and England.2–5 This increase has been seen both in HIV-negative and HIV-positive MSM, and similar trends have been reported from the United States.6
An association between infection with HIV and other STIs has been reported in several epidemiologic studies.7 Also, individuals with gonorrhea have been found to have an increased risk of being infected with HIV.8,9 Furthermore, a rise in gonorrhea cases, especially rectal infections, could be a sign of increased risk of HIV transmission as a result of changes in sexual behavior. Increased sexual risk behavior in MSM has been reported from the late 1990s and onward in several studies in western Europe, the United States, and Australia.10
With better knowledge of the epidemiology of gonorrhea, efforts against spread can be more effective. By characterization of Neisseria gonorrhoeae strains, valuable information about gonococcal strains circulating in the community and in specific core groups can be provided. Classification of N. gonorrhoeae isolates into serovars with coagglutination is a cheap and simple tool that previously has been used to analyze microepidemics of gonorrhea and the dynamics of spread in a given population.11
The aim of the study was to perform a long-term study to analyze the distribution of gonococci in MSM in Stockholm regarding serovars, HIV status, and site of infection to better understand the gonorrhea epidemiology in this endemic core group. A second aim was to compare the distribution of serovars among HIV-positive to HIV-negative MSM.
Materials and Methods
Patients
The patients in this long-term study were all diagnosed with gonorrhea at the Department of Venhälsan of the Södersjukhuset in Stockholm, Sweden. Venhälsan has existed since 1982 and is the only clinic in Stockholm that serves primarily MSM. The clinic offers free counseling, testing, and treatment for STIs, including HIV. The number of patient visits for a new consultation in the counseling and testing service is approximately 3,000 per year (2004).
Tests for HIV, syphilis, hepatitis A and B are routinely offered. In case of symptoms, known exposure, risk for exposure, or at patient request, tests for gonorrhea, chlamydia, and enteric amoebae are also performed. If diagnosed with an STI, partner notification is mandatory for patients with one of the STIs included in the Swedish Communicable Diseases Act, i.e., gonorrhea, chlamydia, syphilis, and HIV. The diagnosed cases are also anonymously reported to the County Medical Officer of Communicable Disease Control (CMO) and to the Swedish Institute for Infectious Disease Control (SMI). All patients treated for gonorrhea were routinely followed up with a test of cure 7 days after the treatment was completed. Patients who have been diagnosed with HIV are followed up and treated in the same clinic. Approximately 550 HIV-positive patients (2004) are registered and followed clinically with visits at least every fourth month. Gonococcal cultures are obtained routinely from these patients when first diagnosed with HIV and later if there has been a risk of exposure or if symptoms are suggestive of gonococcal disease.
The cases included in this study were all MSM. They represented 76% (840 of 1,103) of all MSM reported with gonorrhea to the CMO in Stockholm County during the study period 1990 to 2004. The majority of gonorrhea cases in Sweden are reported from Stockholm County, which accounted for 51% of all gonorrhea cases in Sweden 2004 and 65% of all reported cases in MSM the same year.
HIV Serology
HIV was diagnosed by at least 2 different enzyme-linked immunosorbent assay tests and confirmed by an immunoblot. Repeat specimens were obtained and subjected to the same procedure.
Isolation of Neisseria gonorrhoeae and Serovar Determination
Swabs were obtained routinely from the urethra, rectum, and pharynx for gonococcal culture and sent to the Department of Clinical Microbiology, Karolinska University Hospital in Huddinge and arrived at the laboratory within 12 hours. Before April 1995, charcoaled swabs and Stuart's modified transport medium were used, and after this date, regular cotton swabs were transported in a charcoaled transport medium (Copan Diagnostics Inc., Corona, CA).
Gonococci were cultured on chocolate agar with and without antibiotics (1990–1995: vancomycin, colistin, nystatin, and trimethoprim; 1996–2004: polymyxin B and vancomycin) and diagnosed by colony morphology, positive oxidase test, Gram-negative diplococci in the microscope, typical sugar oxidation test, and confirmed by coagglutination (Phadebact Monoclonal GC-kit; Boule, Stockholm, Sweden). Serovar determination of gonococcal strains was carried out as previously described with a standard set of coagglutination reagents (Phadebact GC serovar test; Boule).12
Statistical Methods
The χ2 test or Fisher exact test was used to calculate the P values. Confidence intervals for the proportions of HIV-positive cases were calculated by assuming a binomial distribution. To compare the mean number of cases in different periods, a 2-sample Wilcoxon sign test was applied. The analyses were made with R version 2.2.1.13
Results
A total of 1,058 N. gonorrhoeae-positive isolates were obtained during the study period. Nineteen isolates from 16 patients were excluded because of possible treatment failure (patients still positive with the same serovars and antibiograms in test of cure and denying any sexual contacts after diagnosis). These 16 cases were diagnosed in 9 different years and represented 9 different serovars. There was no indication that these few episodes of possible treatment failures may have contributed to further spread or persistence. After exclusion of those 19 isolates, 1,039 isolates from 840 gonorrhea episodes in 721 patients remained and were included in the study. As stated subsequently, each diagnosed gonorrhea episode is called a “case.”
Reinfections
Thirteen percent (93 patients) of all patients were reinfected in the same year (36 patients) or another year during the study period, i.e., they were again positive for N. gonorrhoeae the same year or another year after completing treatment and a negative test of cure or they were positive for N. gonorrhoeae with another serovar or antibiogram in test of cure. The majority of the 93 reinfected patients were only infected twice during the study period, but 14 patients were infected 3 times, 4 patients 4 times, and one patient 6 times. These reinfected patients were counted as new cases in the study. In total, 840 cases were included, representing 721 patients.
Site of Infection
The distribution of N. gonorrhoeae-positive isolates (n = 1,039) from different sites in all 840 cases was: 48% urethra, 42% rectum, and 34% pharynx. In 181 cases (22%), strains were isolated from more than one anatomic site at the same time; 164 cases (20%) in 2 sites and 17 cases (2%) in 3 sites. Of all 840 cases, 34% were only positive in isolates from the urethra, 27% in isolates from the rectum, and 17% in isolates from the pharynx.
There was a change over time in the distribution of site of infection. The proportion of cases with positive isolates from the pharynx increased significantly (P <0.001) from 15% in the first period (1990–1997) to 38% of the cases during the second period (1998–2004). During the same time periods, the proportion of cases with positive isolates from the urethra decreased from 54% to 47%, and the proportion of cases with positive isolates from the rectum from 46% to 41%, but neither of these decreases was statistically significant.
Annual Variations
The number of gonorrhea cases increased more than 10 times during the study period. The number of cases during the first half (1990–1997) varied from 13 to 26 cases per year (mean 15). During the second half of the study period (1998–2004), the cases varied from 36 to 158 (mean, 102 per year). This was a significant increase (P = 0.0018) of the mean number of cases during the second part of the study.
HIV Serostatus
The number of HIV-positive men diagnosed with gonorrhea increased during the 15-year period, from 3 cases in 1990 to 16 cases in 2004. However, the proportion of HIV-positive men among all the gonorrhea cases decreased from as much as 50% (95% confidence interval [CI], 21–79) in 1991 to 11% (95% CI, 6–17) in 2004 (Fig. 1).
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Fig. 1: Proportion (ring) and 95% confidence intervals (lines) of gonorrhea cases coinfected with HIV by year (1990–2004). n = total number of gonorrhea cases per year.
A total of 88 (10%) of all gonorrhea cases in the study were in HIV-positive patients. Many of them, 22 of 88 (25%), were diagnosed with HIV and gonorrhea at the same time. This proportion increased significantly (P = 0.038; Fisher exact test) from 11% during the first half of the period (1990–1997) to 32% during the second half of the period (1998–2004).
Sixteen of 22 cases (73%) diagnosed with HIV and gonorrhea at the same time were positive for gonorrhea in the rectum, which was a significantly higher proportion (P = 0.029; Fisher exact test) than among the other cases that were HIV-negative or previously diagnosed with HIV infection. Among the 66 cases with a previously diagnosed HIV infection, there was a significantly higher proportion (61%; P = 0.015; Fisher exact test) that were positive for gonorrhea in the urethra than among the other cases.
Distribution of Serovars
When analyzing the distribution of serovars, 2 isolates from 2 patients were excluded because the serovars were not determined. Also, 178 isolates from patients diagnosed at one time with multiple identical serovars from different sites were excluded. In 17 cases, the patients were diagnosed at one time with 2 different serovars in isolates from different sites, and in 2 cases, the patients were diagnosed with 3 different serovars from different sites. In total, 859 isolates from 838 cases were included in this part of the analysis.
A total of 66 serovars was observed during the 15-year period. Serogroup WII/III (i.e., B serovars) was the most frequent with 61 different serovars, whereas serogroup WI (i.e., A serovars) was only represented with 4 different serovars representing 9 cases. There was also one patient diagnosed with a recombinant serovar Av/Bx.
No serovar was present throughout all 15 years, but 5 serovars were present during a period of 11 to 13 years. These 5 serovars represented 62% of all 859 isolates. Almost half (32 of 66) of the serovars were only present during 1 single year and most of these (27 of 32) were only diagnosed in one case each. The number of different serovars per year varied from 4 to 23 per year (mean, 13 per year). The number of new serovars that were introduced (not seen before in this study) varied from zero to 7 serovars per year (mean, 4 serovars per year). For the annual distribution and number of serovars, see Table 1.
TABLE 1: Neisseria gonorrhoeae Serovars (n = 66) in Isolates (n = 861) From All Gonorrhea Cases (n = 840) in Men Who Have Sex With Men During 1990 to 2004 by Year
Distribution of Serovars Among HIV-Positive and -Negative Patients
Each year, one to 10 different serovars were isolated from HIV-positive patients. A total of 27 serovars were found in HIV-positive patients during the study. Fifteen (56%) of these 27 serovars were present among HIV-positive patients 1 year only and 8 of the 27 serovars (30%) were found in HIV-positive patients only (Table 2).
TABLE 2: Neisseria gonorrhoeae Serovars (n = 27) Occurring Both in HIV-Positive MSM (n = 88) and HIV-Negative MSM (n = 666) by Time Period, HIV Status, Including Previously Known/Not Known (new) HIV-Positive, and Proportion (%) of HIV-Positive
There was a significant difference (P = 0.001) between HIV-positive patients and HIV-negative patients when comparing the serovars. During the 15-year period, the HIV-positive patients were more likely than -negative patients to be infected with a unique or rare serovar than with a serovar that occurred in 5 or more cases. However, this significant difference was only present during the first period (1990–1997) (P = 0.045) and not during the later part of the study (1998–2004) (P = 0.127).
Discussion
The decline in gonorrhea during the AIDS era in 1980s and early 1990s has been assumed to indicate changed sexual behavior with a reduced risk of HIV transmission. An increase in gonorrhea may therefore indicate that guidelines for safer sex have become more difficult to adhere to as the public awareness of the risk for HIV has waned during a post-AIDS era after introduction of highly active antiretroviral therapy in the Western industrialized countries. The significant increase of gonorrhea in MSM in Stockholm during the later years of this 15-year study is in concordance with the trends in many other Western countries.2,6 Incidence data from the SMI) shows an increase of gonorrhea in the Swedish population between 1996 and 2004 from 2.4 to 6.3 cases per 100,000 inhabitants. The reported cases in MSM in Sweden have increased more than 7 times during the same period, and this group accounted for 44% of all cases in 2004 compared with only 15% in 1996.
The use of gonococcal serovars in studying the epidemiology of gonorrhea is a well-established, cost-effective, fast, and easily performed method, but it has also been remarked that the discrimination is suboptimal, interpretation of the results may occasionally be subjective, and there are problems concerning reproducibility.14 The serovar determination system seemed reliable in our study in that only 19 of 181 patients diagnosed with isolates from more than one location at the same time were infected with isolates of different serovars. This is also in concordance with earlier studies.15 Fifteen of the 19 patients had serovars that differed in more than one reaction with the monoclonal reagents. Thus, it is likely that most of these 19 patients actually were infected by multiple strains, which sometimes occurs and has been shown with more discriminating methods in other studies.16
Compared with a previous series of isolates, 6 of the 10 most common serovars in our study belonged to the 10 most common serovars in the general population in Stockholm in 1988 to 1989.17 Two (Brpyut and Brpyust) of the 4 serovars found to be associated with homosexual transmission in men in Edinburgh in Scotland in 1986 to 1990 were also among the 4 most common in our study.18
Surveillance data from the CMO in Stockholm show that the majority of the gonorrhea cases in MSM were infected in Sweden and not abroad and that the proportion of endemic cases in MSM had increased from 64% in 1997 to 77% in 2004. The variation of serovars in this study and the continuing introduction of new serovars during the whole 15-year period indicates an ongoing importation of N. gonorrhoeae strains and, in most cases, rapid elimination in line with previously published experiences in Sweden.3,19 Thus, almost half of the serovars in the study were only present 1 year and only caused one or a few cases each. However, by extending the study period to 15 years, we could demonstrate that several serovars really became endemic in the MSM group. Four predominant serovars (Bpyust, Brpyust, Brpyut, and Bropyst) contributed to more than 100 cases each over more than a decade. The reasons for this variation in serovars over time and greater success for some serovars in becoming endemic are not clear. The existence of serovar-specific immunity has previously been suggested but not found evident by others.20 The 4 most common persistent serovars were present almost all years of the study, but only during the last 5 years did they occur in clusters of 20 to 40 cases per year, indicating possible outbreaks of microepidemics caused by these serovars.
However, it has been shown by more discriminating molecular typing methods that one serovar can represent several different genetic clones.16,21 In a previous study, including the one most common serovar in MSM in Sweden in 1998 to 1999, it was shown that 79% of the domestic cases of this serovar belonged to one genetic clone when analyzed with pulsed-field gel electrophoresis.16 Although serotyping is important as a primary epidemiologic marker to detect possible endemic spread in specific core groups or geographic areas, it is a limitation in our study that neither a complementary typing method nor the antimicrobial susceptibility patterns were used to examine the hetero-/homogeneity within the serovars. Genetic typing methods with high discrimination are needed to confirm transmission chains in sexual networks, especially in core groups in which partner notification can be difficult to perform as a result of anonymous partners, multiple concurrent sexual contacts, or other complicating factors.
In our study, 10% of all cases were seen in HIV-positive men of whom one of 4 was not previously diagnosed with HIV. A high proportion of HIV infection in patients with gonorrhea has been reported in several previous studies.4,9 This suggests that gonorrhea diagnosis in MSM is an important risk marker for HIV, i.e., HIV test should always be offered to these patients if not already known to be HIV-positive. We also found that the proportion of gonorrhea cases that were diagnosed with previously not known HIV infection increased significantly during the second half of the study, whereas the significant difference seen when comparing the distribution of serovars among HIV-positive and HIV-negative cases was not present during the second half of the study. Furthermore, there was a significantly higher proportion of rectal gonorrhea in cases diagnosed with a previously unknown HIV infection compared with the other cases. It has also been shown by others that rectal gonorrhea is independently associated with risk of HIV seroconversion.22 These findings could indicate an increased risk of HIV spread in MSM in Stockholm during the later years of the study with consideration of gonorrhea as a cofactor of HIV transmission.
In contrast to the increasing incidence of gonorrhea, the rates of reported HIV diagnosis in MSM have not increased in Stockholm or in Sweden during the 15-year period according to surveillance data from the Swedish Institute for Infectious Disease Control and the CMO in Stockholm. The finding that the proportion of pharyngeal infections increased significantly during the second part of the study period whereas the proportion of anorectal infections decreased indicates that the increase of gonorrhea in our study rather was associated with unprotected oral sex—with a lesser risk of HIV transmission—than with an increase of high-risk sexual behavior. Similar findings in MSM cohorts have recently been reported from The Netherlands and Germany.23,24 A rise in the incidence of gonorrhea in MSM may not necessarily indicate an increase in high-risk sexual behavior for HIV transmission. It could also reflect changes in sexual networks and an increase in the number of sexual partners that may also affect the incidence of gonorrhea in specific core groups.
In our study, 34% of all the cases positive for N. gonorrhoeae were infected in the pharynx and as many as 17% of all cases were only positive in isolates from this site. This is similar to other studies and it is an important finding in consideration of screening, treatment, and test of cure, because pharyngeal as well as anorectal infections are more difficult to treat and the choice of antibiotics is crucial.25 Furthermore, pharyngeal gonorrhea is most often asymptomatic or subclinical. In a screening study at Venhälsan of 440 MSM seeking consecutive HIV and STI testing, only 13% of the patients infected with gonorrhea in the pharynx and 25% of the patients with rectal infection had symptoms, whereas 86% with urethral infection had symptoms (unpublished data). This underlines that it is not acceptable to only use urine or urethral specimens and DNA amplification methods as diagnostic method in screening MSM. Almost half of the cases (44%) in our study would have been missed in that case.
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