Listeria Survived More Than 25 Years Inside a Blood Culture Bottle

A strain of Listeria monocytogenes originally isolated from a human case of invasive listeriosis has been recovered alive from a blood culture bottle after more than 25 years of storage in a refrigerator. The finding, published as a brief communication in Acta Veterinaria Scandinavica, documents the bacterium’s ability to persist in a nutrient-poor environment and carries practical implications for the food industry, where the species is known to linger in processing environments and contaminate final products.

The story began in 1999, when L. monocytogenes bacteria from the invasive clinical case were cultured in a BacT/ALERT FA blood culture bottle. The researchers stored the bottle refrigerated for over two decades. In 2024, they reopened it to ask whether any cells had survived the long, cold, nutrient-limited confinement, and if so, whether their pulsed-field gel electrophoresis (PFGE) profiles had changed.

When the bottle was examined in 2024, L. monocytogenes was isolated in pure culture, meaning the recovery yielded the target organism without contamination by other microbes. The team selected 100 isolates from the recovered population and compared them with the isolates obtained in 1999 using PFGE, a typing technique that cuts bacterial DNA with a restriction enzyme and separates the resulting large fragments to produce a characteristic banding pattern.

All 100 selected isolates showed the same PFGE profile with the restriction enzyme Asc I as the L. monocytogenes isolates had in 1999. After more than 25 years of refrigerated storage in a spent blood culture bottle, the bacteria not only remained viable but retained an unchanged genomic fingerprint detectable by this method. The authors conclude that L. monocytogenes can apparently survive for a long time in a nutrient-poor environment.

Persistence of L. monocytogenes in clinical samples has rarely been reported, the researchers note, which makes this single bottle a striking data point. By contrast, persistence of the species in the food industry is well documented: several authors report that L. monocytogenes can establish itself in processing facilities, with bacteria ending up in final products. The authors state that the long survival demonstrated in their study must be taken into account by the food industry.

The use of 100 isolates adds weight to the result, showing uniformity across the sampled population rather than survival of a lone, atypical cell. Identical profiles across a 25-year interval indicate that the recovered population descended from the original culture without detectable divergence at this typing level.

The authors are Wilhelm Tham, Hannu Korkeala, Gloria Lopez Valladares and Marie-Louise Danielsson-Tham. The work was published on 29 June 2026 as a brief communication in Volume 68, article number 27 of the journal.

Subject of Research: Long-term survival of Listeria monocytogenes from a human invasive listeriosis case in a blood culture bottle

Article Title: Listeria monocytogenes isolated from a human case of invasive listeriosis survived more than 25 years in a blood culture bottle

Article References: Tham, W., Korkeala, H., Valladares, G. L., & Danielsson-Tham, M.-L. (2026). Listeria monocytogenes isolated from a human case of invasive listeriosis survived more than 25 years in a blood culture bottle. Acta Veterinaria Scandinavica, 68(1), Article 27. https://doi.org/10.1186/s13028-026-00867-4

Image Credits: AI Generated

DOI: 10.1186/s13028-026-00867-4

Keywords: Listeria monocytogenes, invasive listeriosis, blood culture bottle, PFGE, bacterial survival, food industry, persistence, nutrient-poor environment, Asc I, refrigerated storage, Listeria, monocytogenes