Outbreaks of shigellosis in England and Wales, 2004: use of phenotypic and molecular typing for strain differentiation

Abstract number: 1733_745

Cheasty T., Threlfall J.

Objectives: In the summer of 2004 a number of apparently unrelated outbreaks of Shigella sonnei infection were observed amongst patients throughout England and Wales. Infections were identified throughout the country but were concentrated in the London area, and the north-west and north-east of England. Outbreaks were in both religious communities and in homosexual men. The outbreak among homosexual men was centred in the London area but outbreaks in the religious community occurred in London, the north-west and the north-east. For meaningful epidemiological investigations in real-time discrimination within the serovar was essential. With this in mind a hierarchical approach based on phenotypic subdivision by phage typing and antibiogram, supplemented by molecular typing using plasmid profile and macrorestriction fingerprinting by pulsed-field gel electrophoresis (PFGE) has been adopted.

Methods: Isolates of Sh. sonnei from infections in England and Wales in 2004 have been phage typed using the scheme of Hammerstrom, Kallings and Sjoberg. Isolates have been tested for resistance to a range of antimicrobials, plasmids identified and sized following extraction of plasmid DNA according to Kado and Liu, and PFGE performed by standard protocols according to Pulse-Net USA.

Results: In all outbreaks the only resistance pattern (R-type) identified was that of ASSuSpTTm (A, ampicillin; S, streptomycin; Su, sulfonamides, Sp, spectinomycin; T, tetracyclines; Tm, trimethoprim). The outbreak among homosexual men was characterised by a new Sh. sonnei phage type (PT), designated PT Q. The isolates from this outbreak were further characterised by a distinctive plasmid-and pulsed-field profile. Isolates from outbreaks among members of a religious community were characterised by three other phage types distinct from PT Q, and by different plasmid- and PFGE profiles, indicating the presence of temporally-associated but independent incidents.

Conclusions: These results indicate that outbreaks of Sh. sonnei can be subdivided by a combination of phenotypic and molecular typing. Results can be obtained rapidly, and can be used in real-time for epidemiological investigations.

Session Details

Date: 31/03/2007
Time: 00:00-00:00
Session name: European Society of Clinical Microbiology and Infectious Diseases
Location: ICC, Munich, Germany
Presentation type:
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