Epidemiology of penicillinase-producing Neisseria gonorrhoeae in Singapore

Abstract

The number of infections with penicillinase-producing Neisseria gonorrhoeae (PPNG) strains in Singapore has risen from three in 1976 to 1792 in 1979. In the latter year they formed 19.2% of all infections with gonorrhoea, and 1280 of the strains isolated were from female prostitutes. The prevalence of PPNG infections is analysed according to the different sections of the community and racial groups. Despite energetic control measures PPNG strains are not being contained within Singapore. Thus global dissemination from such a busy port and tourist centre is a real danger.

PIP: The incidence of penicillinase-producing Neisseria gonorrhoeae (PPNG) infections in Singapore increased alarmingly from 3 cases in 1976 to 1792 cases in 1979, in which year such strains comprised 19.2% of total gonorrhea infections. This increase was parallelled by a decrease in the number of non-PPNG cases from 8036 in 1978 to 7540 in 1979. Female prostitutes contributed 72.7% of PPNG infections in 1979. In that year, 32% of gonorrhea infections among women other than prostitutes were PPNG strains. This has implied an increased occurrence of ophthalmia neonatorum and pelvic infection. The group at highest risk of infection includes single men aged 15-29 years engaged in semiskilled or unskilled labor. 85% of patients cited Singapore as the place of contact. Professional prostitutes were the primary contact in 72% of cases in 1978 and 66.8% of cases in 1979. Boyfriends or husbands contributed 10% of infection in both years. Contact tracing has produced a 51% success rate. Non-PPNG strains have been isolated from 15% of primary contacts, suggesting concomitant infection with both PPNG and non-PPNG strains. Measures to control sexually transmitted diseases are vigorously pursued in Singapore. These include intensive bacteriologic surveillance, effective treatment, determined contact tracing, and control of infection in prostitutes. About 5000 prostitutes have been registered with a medical scheme to which they report for periodic examination. The success of this scheme is indicated by the reversal of the male-to-female ratio for gonorrhea from 3:1 in 1975 to 1:3 in 1979. All patients with suspected gonorrhea have smears and cultures performed, and N. gonorrhoeae isolates are screened for penicillinase production by the iodometric method. A 98% cure rate has been achieved through a single 2 gm dose of kanamycin. However, these measures have not been able to contain the spread of PPNG infection. As infection with these strains becomes more prevalent, it may be necessary to switch to more costly treatment methods, e.g., aminoglycosides. Such treatment would increase the risk of 8th nerve damage and renal toxicity, and might not abort incubating syphilis. Since Singapore is a busy port and a major tourist center, global dissemination of PPNG infection constitutes a serious danger.