In March 2024, the case report "Recurrent, ICD-associated L. monocytogenes bacteraemia with multiple septic pulmonary embolisms over a 2-year period" was published in a collaboration between AGES, the Tauernklinikum Zell am See and the Paracelsus Medical University Salzburg. AGES was involved in this report with the National Reference Laboratory for Listeriosis, the National Reference Laboratory for Listeria monocytogenes and the Department of Statistics and Analytical Epidemiology. AGES employees Astrid Füszl and Stefanie Schindler are the first authors of this publication.
This report presents a complex case of chronic listeriosis in which six relapses occurred within two years, some of them with severe clinical pictures such as pulmonary embolisms and septicaemia. After intensive investigation, the patient's implanted defibrillator was identified as the source of infection.
The case shows that in patients with foreign bodies, e.g. artificial joints or an implanted defibrillator, the bacteria Listeria monocytogenes can remain after an infection and trigger relapses.
The aim must be to identify and reduce the risk of such relapses through comprehensive clarification.
Listeria (L.) monocytogenes
L. monocytogenes are bacteria that are mainly transmitted through the consumption of contaminated food, including unpasteurised dairy products, smoked salmon and poultry. In people with an intact immune system, an infection usually remains asymptomatic or only triggers mild symptoms. In older and immunocompromised people, L. monocytogenes can lead to invasive listeriosis, in which the bacteria spread beyond the digestive tract. This can lead to septicaemia (blood poisoning) or inflammation of the brain and meninges. In rare cases, invasive listeriosis can trigger several relapses, whereby foreign bodies such as heart valves, heart apparatus or joint prostheses can be colonised and serve as a reservoir in the body.
Case description
The report describes a particularly complex case of chronic invasive listeriosis with a total of six episodes of illness over a period of two years, from 2021 to 2023. The 78-year-old patient had a defibrillator implanted in 2002. Several Listeria infections occurred, in which the electrodes of this implanted defibrillator were suspected as the cause. Despite extensive examinations and treatment, including several hospitalisations, the infections could not be permanently cured. Ultimately, the defibrillator was removed, but this was not completely successful due to complications during the procedure. The patient died as a result of a stroke and multiple septic embolisms.
Investigations
The bacterium L. monocytogenes was isolated from the patient's blood and from the electrodes of the defibrillator between 2021 and 2023 and five L. monocytogenes isolateswere obtained. These five L. monocytogenes isolates were subjected to various microbiological tests. The National Reference Laboratory for Listeriosis and the National Reference Laboratory for Listeria monocytogenes analysed the susceptibility of the bacteria to antibiotics using antimicrobial susceptibility testing (AST). They also carried out serotyping and sequencing. An important step in this was to find out the relationship between the isolates in a cluster analysis. This involves analysing and comparing the alleles, i.e. the different variants of a gene at a specific position on a chromosome. The current threshold value in the cluster analysis to confirm descent from the same parent cell is a difference of seven alleles. The results of the genetic analyses showed that the L. monocytogenes isolates from the blood cultures and the defibrillator electrodes were essentially identical. Only the blood culture from February 2023 differed slightly from the others. It is assumed that a separate cluster has formed here, even if it remains part of the original clone. In this case, it was therefore a case of relapses and not new infections.
Outlook
This case study shows the challenges of treating Listeria infections caused by implanted medical devices. For the future, it is important to better understand the origin and development of the disease and the evolution of Listeria monocytogenes. Further studies are planned to investigate the impact of the molecular findings on future cluster analyses of Listeria monocytogenes. In particular, the current cluster threshold of seven alleles will be reviewed in order to develop better diagnostic and therapeutic strategies. These findings could help to improve management protocols for patients with chronic Listeria infections and minimise the risks of relapse
The study is available at: Füszl, A., Schindler, S., Heger, F. et al, 2024. Recurrent, ICD-associated L. monocytogenes bacteraemia with multiple septic pulmonary embolisms over a 2-year period. infection. https://doi.org/10.1007/s15010-024-02209-w