Italy investigates ongoing Listeria outbreak
In early 2016, five serotype 1/2a Listeria monocytogenes isolates were collected from patients with invasive listeriosis in Ancona province, according to a report in Eurosurveillance.
These strains and six 1/2a isolates identified in 2015 in the same area were typed by enterobacterial repetitive intergenic consensus (ERIC)-PCR and pulsed-field gel electrophoresis (PFGE).
In early 2016, five serotype 1/2a Listeria monocytogenes isolates were collected from patients with invasive listeriosis in Ancona province, according to a report in Eurosurveillance.
In Europe, Listeriosis infections reported in humans increased by 16% compared with 2013 to 2,161 confirmed cases in 2014.
Start of outbreak last year
A clonal relationship between the two sets of isolates suggested a listeriosis outbreak that potentially started in 2015.
From 4 January to 15 February 2016, six L. monocytogenes strains were isolated from six patients diagnosed with invasive listeriosis. Eight L. monocytogenes strains had been isolated last year.
Multiplex PCR serotyping assigned five 2016 isolates and seven 2015 isolates to serotype 1/2a; the remaining isolates were serotype 4b (2016) and serotype 1/2c.
1/2a 2015 isolates showed a high degree of similarity (> 85%) with respect to the 1/2a 2016 isolates.
Multiplex PCR serotyping is a practical alternative to slide agglutination serotyping, since it differentiates among the five major serogroups, each of which includes multiple serotypes, said the researchers.
Ongoing outbreak with unclear source
“The present data suggest an ongoing outbreak of listeriosis due to serotype 1/2a L. monocytogenes in AV2 that most probably started in 2015, since the strain was already present in the area in 2015,” said the authors.
“Local authorities are working with the Italian national public health institute (the Istituto Superiore di Sanità, Rome) and the regional Istituto Zooprofilattico Umbria and Marche to identify the sources of food contamination.”
The researchers said there are findings which suggest contamination of a pork product as a possible vehicle of infection for at least one human case.
However, no clear link can be established between the contaminated item and the infections so investigation into the source of infection is still in progress.
Listeria is also found in soil, plants and water. Animals, including cattle, sheep and goats, can carry the bacteria.
Source: Eurosurveillance, Volume 21, Issue 17, 28 April 2016
“Ongoing outbreak of invasive Listeriosis due to serotype 1/2A Listeria Monocytogenes, Ancona Province, Italy, January 2015 to February 2016”
Authors: E Marini, G Magi, C Vincenzi, E Manso, B Facinelli
