Pregnancy-associated listeriosis- 30 years of experience in Argentina

Abstract

Background: Invasive listeriosis is a rare but life-threatening infection caused by Listeria monocytogenes (Lm). Human invasive listeriosis is considered a foodborne disease and generally affects immunocompromised individuals, pregnant women and newborns. Listeriosis may cause fetal loss, preterm delivery and neonatal sepsis. In Argentina, listeriosis is included as a reportable disease in the National Laboratory-based Surveillance System. This report is voluntary, so underreporting might exist. Objective: To report cases of pregnancy-associated listeriosis (PRL) occurring in Argentina from 1986 to 2016 to determine the burden and trend of this disease in our setting. Methods & Materials: Identification of Lm isolates from PRL referred to the National Reference Laboratory (NRL) during the period 1986-2016, was confirmed using conventional biochemical tests and serotyped by the slide agglutination method until 2004 and by multiplex PCR since 2005. From 2005, ongoing subtyping was conducted by pulsed-field gel electrophoresis (PFGE) with ApaI and AscI, according to standard protocols. Results: From 325 isolates from human listeriosis referred to NRL during the last 30 years, 34% (n = 111) corresponded to cases PRL. They were classified as: maternal infection with ongoing pregnancy (12%); fetal loss (7%) and live-born neonatal listeriosis (81%). Serotype 4b was prevalent (71%), followed by serotype 1/2b (28%) and only one isolate (1%) belonging to serotype 1/2a. From 2005, 24 isolates from PRL were analyzed by PFGE. Three clusters were detected. Each cluster included 2 isolates with indistinguible pulsovar with both enzymes. Epidemiological data suggested that two clusters corresponded to a probable nosocomial transmission and the third cluster corresponded to a newborn and a post delivery control of the mother. Conclusion: A decrease in the number of cases of PRL was observed during the last decade. This might be related to the improvement in control measures implemented at the food production level. Effective surveillance of listeriosis requires information about types of food consumed by the patients in order to assess risk and improve the awareness of dietary recommendations in susceptible population. The inclusion of listeriosis in the National Mandatory Notification System from 2018 will improve the analyses of the distribution of this infection and the promotion of effective prevention and control.