Micro-epidemics of campylobacteriosis in Luxembourg: Statistical cluster detection using extended multi-locus sequence typing

Abstract

Campylobacter infections are a major public health concern and in the past few years, have emerged as a leading cause of bacterial gastroenteritis in Luxembourg as well as in the other EU member states. Most cases are thought to be sporadic and the source of contamination is rarely known, but few researchers have investigated this issue using state of the art typing methods. Our investigation has conducted a large epidemiological study of campylobacter infections detected in Luxembourg during 2011 and 2012 with over 1000 documented cases. All campylobacter isolates reported to us were genotyped using state of the art molecular sequencing techniques (multi locus sequence typing + 2 other genes) and patients were sent a questionnaire with for reporting clinical symptoms and exposures. We conducted an exploratory data analysis of the full data set including genotyping information and seasonality. We conducted cluster detection in time and space of genotypes using scan statistics in order to investigate whether genotyping can reveal small clusters that are indicative of an outbreak due to a common source. Though it is common knowledge that most human Campylobacteriosis cases are sporadic in nature, our analysis has been able to demonstrate that a considerable proportion of human campylobacter infection may occur in clusters which are representative of mini outbreaks at the molecular level of which some may be attributed to a single genotype.