Epidemiology and Molecular Typing of Pregnancy-Associated Listeriosis Cases in Lombardy, Italy, over a 10-Year Period (2005–2014)‎

Abstract EN

In developed countries, pregnancy-related listeriosis accounts for 20–43% of total invasive listeriosis.

This work describes the first pregnancy-related listeriosis survey in Italy based on two data sources, that is, mandatory notification system and regional laboratory-based network.

Out of 610 listeriosis cases reported over a 10-year period, 40 were pregnancy-related (6.6%).

Among these, 29 pregnancy-related isolates were available and have been analysed with serotyping, Pulsed-Field Gel Electrophoresis, and Multi-Virulence-Locus Sequence Typing.

No maternal fatality was recorded, but 11 (29.7%) pregnancies resulted in a foetal death, a miscarriage, or a birth of a foetus dying immediately after birth.

The average incidence of pregnancy-related listeriosis was 4.3 cases per 100000 births, and the proportion of pregnancy-associated listeriosis among ethnic minorities was significantly higher compared to the general population (30.0% versus 3.5%, P<0.01).

L.

monocytogenes isolates belonged to serotypes 1/2a, 1/2b, and 4b, with the latter significantly more prevalent among pregnancy-related isolates.

Twenty different pulsotypes were distinguished and 16 out of the 29 isolates were classified into seven clusters.

A total of 16 virulence types (VTs) were identified.

Five VTs accounted for 45% of the total cases and coincided with those of previously described Epidemic Clones (ECs) of L.

monocytogenes.