Enteropathogenic Campylobacter jejuni and C. coli presently comprise the most common cause of acute bacterial gastroenteritis in the developed world, as well as being important gastrointestinal pathogens in developing and underdeveloped countries. The majority of human cases (99%) present as sporadic in nature, unlike other gastrointestinal infections, such as those caused by Salmonella Typhimurium, which are generally more related to large institutional outbreaks. However, it is unclear whether or not the epidemiologies of human campylobacter infections are related, due to poorly developed and evaluated subspecies typing schemes for this organism. We report on an outbreak of food-poisoning, caused by C. jejuni among Environmental Health O¤cers (EHOs) attending a lunch in the west of Northern Ireland, over a 6 -day period (Figure 1). Fecal specimens were received from 21 EHOs attending the lunch and were examined conventionally at the Northern Ireland Public Health Laboratory (NIPHL), Belfast City Hospital, for the presence of Campylobacter spp., by direct plating onto Preston's selective agar [1]. Of these, nine were positive. In order to enhance the growth of potentially small numbers ofCampylobacter spp., all culture-negative fecal specimens were selectively enriched in Preston's broth culture; of these, one further specimen became positive. All isolates were con¢rmed by standard phenotypic laboratory methods as C. jejuni and gave the following antibiogram by disk susceptibility testing: resistant to penicillin (2 iu), cephalexin (30 mg) and trimethoprim (2.5 mg); sensitive to chloramphenicol (10 mg), erythromycin (5 mg), gentamicin (10 mg), nalidixic acid (30 mg), tetracycline (10 mg) and cipro£oxacin (1 mg), with the exception of one isolate whichwas resistant to cipro£oxacin. Molecular epidemiologic studies were initiated in order to examine the genetic relatedness among the 10 fecal Campylobacter isolates obtained. Polymerase chain reaction^singlestranded conformational polymorphism (PCR-SSCP) [2] of a 1.7-kb region of the £agellin ( £aA) gene following endonuclease restriction with DdeI [3], and multilocus enzyme electrophoresis (MEE) [4], examining nine cellular enzyme loci, were carried out in parallel. PCR-SSCP relies on the diierential electrophoretic mobility of single-stranded DNA under denaturing conditions, as nucleotide substitutions will induce conformational changes, leading to detectable mobility shifts. Thus, diierences between DNA banding patterns represent markers that are valuable in con¢rming outbreaks, as well as tracing organisms around the environment.The PCR amplicon (1.7 kb) was initially restricted with DdeI to yield small restriction fragments (< 600 bp), which were further separated by SSCP analysis. MEE detects polymorphisms in the gene loci coding for protein enzymes on a starch gel, and previous work has shown that this method is able to detect very ¢ne diierences between isolates. Phenotyping and molecular genotyping expertise is normally not present in most primary diagnostic clinical laboratories, due to the relative complexity and high-costs associated with having such facilities available locally. Consequently, small local outbreaks due to this organism may not be detected, where a rapid and local response for the clinical microbiology laboratory is essential in order to aidwith public health epidemiologic investigations and containment of contaminated foodstuis or water. Presently, with a lack of phenotypic and genotypic schemes available locally, subspecies strain relatedness is crudely based on a number of qualitative phenotypic parameters, such as diierences in colony morphology, and on limited antibiogram typing, based on a qualitative comparison of a limited number of disk diiusion antibiotic susceptibility assays. In this study, PCR-SSCPandMEEgave a single ¢ngerprint and electrophoretic type (ET), respectively, indicating that the isolates involved in this outbreak were genetically indistinguishable. Although the genetics ofCampylobacter used in subtyping methods are hypervariable, the genotype seen in this outbreak, although relatively uncommon, was previously isolated from a 16-year-old male patient with gastroenteritis at LaganValley Hospital on 23 May 1994. In addition, the antibiogram pro¢le of theC. jejuni strain observed in this teenager matched that of the outbreak clone. Concise Communications ânae