Laboratory diagnostic service range

Test material: culture isolate

Routine

Identification using biochemical methods
Serovar identification using multiplex PCR and agglutination
Type identification using PFGE (Pulsed-field gel electrophoresis)
Antibiogram using agar diffusion test

Special tests

AFLP (amplification fragment-length polymorphism)
Rep PCR (Repetitive extragenic palindromic PCR)
Identification using sequencing
Liquor: PCR for Listeria monocytogenes
Stool: PCR for Listeria monocytogenes
Serum: Listeriolysin O-IgG (LLO-IgG, enzyme immunoassay)
Serum: Widal agglutination reaction (O:1, H:1, O:4b, H:4b)
Clinical test material: direct cultivation on selective, solid and liquid nutrient media

The routine tests listed usually suffice to answer all clinically-diagnostic and epidemiological questions reliably. PCR from liquor can be used if the pathogen culture cannot be identified following previous antibiotic treatment. Serological tests are difficult to interpret as cross reactions in healthy specimen and a shortage of antibody evidence in Widal tests are very common. As a result, we only recommend serological tests in individual cases (e.g. suspicion of rhombencephalitis), if a direct pathogen test cannot be carried out. 

Should consumers be worried about having been infected with listeria after warnings about contaminated food products, their doctor can send a stool sample to a microbiology lab for a listeria test. A negative result should clear up all worries. The prophylactic administering of Amoxicillin may be considered only should the sample tested be positive for listeria; the prophylactic administering of antibiotics without testing the pathogen culture is considered contraindicative because the risk of severe side effects caused by the antibiotics is much higher than the very low risk of developing listeriosis.

Test of isolates from samples taken from food and the environment are carried out at the National Reference Laboratory for Listeria.

Reporting Obligation

Listeria are considered bacterial food poisoning pathogens and cause invasive, bacterial infections (sepsis, meningoencephalitis) and must be reported to the authorities in line with Art. 1 Austrian Epidemic Act 1950. The following has applied to reporting listeriosis cases associated with pregnancies since June 2013: any miscarriage and stillbirth caused by a pregnancy-associated listeriosis infection of the mother must be officially reported. The listeriosis infection of the mother must be considered a separate case that must be reported to the authorities.