ANALYSIS OF CIRCULATING STRAINS, CAUSING INVASIVE LISTERIOSIS IN BULGARIA FOR TEN YEARS, 2010-2019

Listeriosis is a zoonosis with multiple mechanisms of infection and multiple organ symptoms, severe course and high lethality. An increasing incidence of listeriosis has been reported in several European countries in recent years. A limited range of Listeria strains is responsible for most blasts occurring in different countries. The aim of the study is to monitor the spread of the Listeria strains causing invasive listeriosis in Bulgaria for the period 2010-2019 and to analyze the etiological structure of the infection in different hospitals in the country. A total of 56 strains Listeria from 17 hospitals were investigated for confirmation of species and serogroup. The materials were isolated from haemocultures, fetuses water, cerebrospinal fluids and anal and throat secretions and two tests were used. Confirmed strains isolated from the clinical samples for the study period belonged to 4 serogroups of Listeria. Listeria monocytogenes serogroup I was detected in 28 (50%) of the samples, Listeria monocytogenes serogroup II – in 43%, Listeria innocua –in 5% and Listeria welshimeri – in 2% of the samples. The strains isolated from cerebrospinal fluid predominated (52%) and those isolated from haemocultures were 36%. Nineteen of the isolated strains from cerebrospinal fluid belonged to serotype 4b (19/29). Listeria monocytogenes serogroup I was detected in 70% from haemoculture. Listeria innocua and Listeria welshimeri were detected from cerebrospinal fluid. Serotype 1/2a was found in six hospitals and serotype 4b - in five hospitals. The majority of isolated strains was from newborns  -12/56 (21.43%). Serotype 1/2a was detected in 12 hospitals and serotype 4b in 11 hospitals. The largest variety of strains was found in Plovdiv, UMBAL “Sv. Georgi”. The data confirmed a steady trend in the spread of certain listeria serotypes in each hospital over the years. The focus in the future should be on screening at-risk groups, mainly women of childbearing and it is recommended to look for the risk of listeriosis.