Clinical characteristics and epidemiologic study of a listeriosis outbreak in Grand Canary

BACKGROUND AND METHODS: Human infections caused by Listeria monocytogenes often present as sporadic cases without any epidemiological relationship among them; however they also appear as outbreaks that are usually detected by an increase in the number of cases diagnosed by hospitals of the geographic area. Between December 1991 and May 1993, twenty four cases of listeriosis were detected in three hospitals of Las Palmas de Gran Canaria; and they were classified as an outbreak. Our report describes its clinical, epidemiological and microbiological aspects. RESULTS AND CONCLUSIONS: Twenty four cases of listeriosis were diagnosed, 12 occurred in pregnant women or neonates (5 and 7 respectively) and 12 in non pregnant adults. All adult infections were community-acquired. The incidence rate was, for the epidemic area, 76.3 cases per million population during the period considered (18 months). Among non pregnant adults, 9/12 patients had some underlying disease and 9/12 presented CNS affection (meningitis and/or cerebritis). In the group of pregnant women, 4 cases occurred in the second trimester and fetal loss was caused; one case was detected in the third trimester and four weeks later the patient delivered an unaffected infant. All cases of neonatal listeriosis presented as early-onset sepsis. Of the 24 strains of L. monocytogenes, 21 were serotype 4, two were serotype 1 and one was not typeable. Strains from 12 patients were available for epidemiological analysis, seven of which corresponded to the same pattern and there were three more different patterns.