Shigella sonnei Outbreak among Homosexual Men, London

摘要

To the Editor: In the summer of2004, genitourinary medicine clinicsin London reported cases of Shigellasonnei with a novel phage type pattern(later designated PTQ). Outbreak casefinding involved local laboratoriesand genitourinary medicine physi-cians in London, as well as the nation-al reference laboratory. A case wasconsidered confirmed if S. sonneiPTQ was isolated from January 2004through April 2005, and the patienthad not traveled outside the countrythe week before illness. Possible caseswere defined as for confirmed casesbut were so designated when patienthad a history of foreign travel in theweek before illness or when travelhistory was unknown. From October2004, when we became aware of theoutbreak, until December 2004, weconducted telephone interviews withnewly identified case-patients. Forcases that occurred before October2004, and from January 2005 throughApril 2005, information was obtainedfrom laboratory records only.Strains were phage typed by usingthe scheme described by Hammer-strom, Kallings, and Sjoberg, accord-ing to a protocol supplied by R.Wollin (1,2). The scheme consists of11 phages and is based on the typingof the rough phase II variant of S. son-nei. The scheme comprises definedphage types (PT) 1–100 and provi-sional PTs A–P. Cultures were grownovernight on MacConkey agar, and arough colony was placed in nutrientbroth and grown for 18 hours at 37°C.The broth culture was then used toflood a nutrient agar plate and, oncedry, spotted with the 11 phages andincubated at 37°C for 5 hours. Thepatterns of lysis were recorded andcompared with those indicated on thetyping chart. All isolates werescreened for resistance to a panel ofantimicrobial agents by an agar incor-poration method with Iso-Sensitestagar (Oxoid, Basingstoke, UK).