Large Nationwide Outbreak of Invasive Listeriosis Associated with Blood Sausage, Germany, 2018–2019

Abstract

L isteriosis is a severe, mainly foodborne, human infection associated with higher casefatality and hospitalization rates than other bacterial gastrointestinal pathogens (1). The causative agent, Listeria monocytogenes, occurs ubiquitously in the environment and disseminates into the food production chain. Patients develop either self-limiting noninvasive gastroenteritis or invasive listeriosis (2,3). Listeriosis adversely affects older and immunocompromised persons, as well as pregnant women, causing a severe invasive form of the disease that leads to sepsis, meningitis, and encephalitis, as well as neonatal infections and miscarriage (4). Case-fatality rates of invasive listeriosis are ≈30% for neurolisteriosis and even higher in septic patients (5). In Europe and North America, invasive listeriosis affects 0.3-0.6 persons/100,000 population/year (6,7). L. monocytogenes forms hard-to-remove biofilms in food-processing plants, can acquire tolerance to sanitizers, and multiplies even at temperatures used for refrigeration (8). These properties complicate efficient prevention of L. monocytogenes contaminations in different types of ready-to-eat products, including dairy, meat, and fish, and in fruits and vegetables, all of which have been vehicles for listeriosis outbreaks in the past (9-12).

Listeriosis Caused by Persistence of Listeria monocytogenes Serotype 4b Sequence Type 6 in Cheese Production Environment

“…L. monocytogenes ST6 is increasingly associated with outbreaks, including an outbreak linked to frozen vegetables in 5 countries in Europe during 2015–2018 ( 5 ), an outbreak associated with contaminated meat pâté in Switzerland during 2016 ( 6 ), and the largest listeriosis outbreak globally, which occurred in South Africa during 2017–2018 ( 7 , 8 ). More recently, the largest outbreak of listeriosis in Europe in the past 25 years was reported in Germany and was traced back to blood sausages contaminated with L. monocytogenes ST6 belonging to a particular clone referred to as Epsilon1a ( 9 ).…”

Population structure-guided profiling of antibiotic resistance patterns in clinical Listeria monocytogenes isolates from Germany identifies pbpB3 alleles associated with low levels of cephalosporin resistance

“…If strains with different CTs formed a joined complex, a representative strain belonging to the most abundant CT within this complex was selected. An observation further justifying the selection of cluster representatives was obtained in a previous study, showing that isolates belonging to an outbreak cluster possess highly similar antibiotic resistance profiles [40]. In addition to the cluster representatives, all sporadic isolates (422 of 1220) were included to further increase the genetic diversity within the selection of L. monocytogenes isolates.…”

Listeriosis Caused by Persistence of Listeria monocytogenes Serotype 4b Sequence Type 6 in Cheese Production Environment

“…A cluster was defined as a group of isolates with <10 different alleles between neighboring isolates (9,11). Twelve of 13 isolates were assigned to ST6 CT7448, a unique profile in the database, showed by cluster detection to be closely related.…”

“…back to blood sausages contaminated with L. monocytogenes ST6 belonging to a particular clone referred to as Epsilon1a (9).…”