Outbreak of Shigella boydii dysentery in the county of El Bierzo

BACKGROUND: Investigation of an outbreak of bacillar dysentery of possible transmission by water produced by Shigella boydii. METHODS: The strains were isolated in the stools and studies of identification, serotyping, susceptibility to antibiotics and plasmid profile were carried out according to standard methods. The epidemiological investigation was carried out retrospectively. RESULTS: 51 strains were isolated from 48 patients. All were identified as S. boydii serotype 4. The pattern of susceptibility was variable, all of them showed resistance to ampicillin, tetracycline and chloramphenicol. The plasmid profile was homogeneous. Of the 41 patients who completed the questionnaire all were living in the same town or nearby localities. CONCLUSIONS: The serotype 4 of S. boydii, infrequent in Spain, the homogeneous plasmid profile and the relationship between time and place of the cases, suggest that we find ourselves faced with an outbreak epidemiologically relationed. The localisation of the cases and the network of the drinking water supply represented on the plan of the town, support the hypothesis of the origin of hte outbreak as being in the lack of chlorination of one of the tanks of the network of supply.