Shigellosis linked to sex venues, Australia - Dispatches

Emerging Infectious Diseases, August, 2002 by Belinda O'Sullivan, Valerie Delpech, Giulietta Pontivivo, Thomas Karagiannis, Debbie Marriott, John Harkness, Jeremy M. McAnulty

From January 1 to July 31, 2000, 148 cases of Shigella infection were reported in New South Wales, Australia, compared with an annual average of 95 cases. Of reported cases, 83% were confirmed as Shigella sonnei biotype G infections; 80% were in homosexual men. Visiting a sex venue in the 2 weeks before onset of illness was the only factor significantly associated with shigellosis.

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In 2000, a major inner-city hospital laboratory in Sydney, New South Wales (NSW), reported to local health authorities an unexpected increase in the incidence of shigellosis in homosexual men. Shigellosis outbreaks have commonly been reported related to person-to-person contact (1), child-care centers, food sources (2), institutionalized populations (3), and contaminated water (4). The infectious dose is low, with 10-100 organisms/mL sufficient for infection (5). In the United States, reports in the 1970s linked shigellosis transmission to orogenital and oral-anal sexual contact between men in bathhouses (6-7) and more recently with underlying HIV infection (8). Recent clusters of Shigella sonnei infection have been identified in Canada (9) and San Francisco (10) in men who have sex with men.

Sex venues in Australia are commercial establishments or bathhouses where men pay an entry fee to engage in casual sex with other men. Such establishments-may provide bondage equipment, cubicles for anonymous sex, saunas, lounges, douching facilities, and toilets. At the time of the outbreak, no guidelines governed infection control in these venues.

The Study

We contacted all public and private microbiology laboratories in inner Sydney as well as state and national reference laboratories to identify cases of shigellosis in NSW and determine the average number of cases per year. We defined outbreak-associated cases as shigellosis in homosexual men resident in NSW, aged 19-66 years, and identified by laboratories to have Shigella sonnei biotype G (SSBG) infection or untyped S. sonnei (if the laboratory did not routinely biotype S. sonnei) from April 1 to July 31, 2000. A patient questionnaire, piloted in 1999, included demographic details and history of illness, sexual activity, dining out, and overseas travel. Physicians from five key medical centers in inner Sydney specializing in homosexual men's health agreed to seek verbal consent from patients to either complete the questionnaire or be contacted by the investigators by telephone.

We compared reported risk exposures of patients with controls who completed the same questionnaire (all self-administered) at the same medical centers from March 1 to July 31, 1999 (Delpech, unpub. data). Controls were defined as homosexual or bisexual male residents of NSW who did not report any diarrhea in the previous 3 months.

We contacted all sex venues in inner Sydney by telephone to request permission to conduct an audit of hygiene and infection control practices. An infection control nurse inspected each venue, completing a standard audit tool that covered the appropriateness of lighting and surfaces for cleaning, cleaning regimens, hand washing, douching facilities, condom availability, and staff education. Microbiologic swabs were taken from contact surfaces including mattresses, cubicle walls, bondage equipment, door handles, and lubricant dispensers and placed in transport medium.

Aerobic cultures were performed on blood agar and MacConkey agar plates. Organisms were identified on Gram stain and routine biochemical testing. Antimicrobial susceptibility was performed by the National Committee of Clinical Laboratory Standards method with ciprofloxacin, co-trimoxazole, ampicillin, and cefotaxime. Clonality was demonstrated by using pulsed-field gel electrophoresis, enterobacterial repetitive intergenic consensus, and random-amplified polymorphic DNA polymerase chain reaction.

Univariate and multivariate logistic regression analysis was conducted by using Statistical Analytic Software (SAS; SAS Institute Inc., Cary, NC). Variables with p values <0.25 were applied to the multivariate model initially, and the backward stepwise elimination method was used. "Casual sexual partners" were defined by reporting "having casual sex partners in the last 3 months."

One hundred forty-eight patients with Shigella infection were identified from January 1 to July 31, 2000, in NSW; 123 (83%) were confirmed as having SSBG infections, compared with an annual average of 95 cases, with about 50% typed as SSBG (11). Most of the patients were reported during April and May (N=89) (Figure). Of the 123 patients with confirmed SSBG, 98 were identified as homosexual men ages 16-66 years and were defined as outbreak-associated cases. Of these, 15 (15%) were excluded because they had no physician-contact details, as these details were not routinely collected by state and national reference laboratories.

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Questionnaires were completed by 42 (51%) of the remaining 83 patients; 33% of 42 questionnaires were completed by telephone interview with the investigators. Similar proportions of patients who completed a questionnaire (N=42) lived in inner Sydney (64%) compared with all outbreak-associated cases (N=148) (58%); both groups had a median age of 38 years. The main reason questionnaires were not completed was refusal to participate.