AUTHOR=Xu Jiang , Wu Shi , Liu Ming , Xiao Zitian , Peng Yangyang , He Huanqing 

TITLE=Prevalence and contamination patterns of Listeria monocytogenes in Pleurotus eryngii (king oyster mushroom) production plants

JOURNAL=Frontiers in Microbiology

VOLUME=14

YEAR=2023

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2023.1064575

DOI=10.3389/fmicb.2023.1064575

ISSN=1664-302X

ABSTRACT=<p><italic>Listeria monocytogenes</italic> is a major foodborne pathogen that is well-known for its high mortality rate upon infection. In recent years, the edible mushroom has also been found to be an important source of <italic>L. monocytogenes</italic>, but the contamination sources in <italic>Pleurotus eryngii</italic> (the king oyster mushroom) were unclear. In this study, a total of 203 edible mushrooms and environmental samples from four <italic>P. eryngii</italic> production plants were obtained. As a result, 29 samples (14.3%) were positive for <italic>L. monocytogenes</italic>, including eight mushroom samples (13.3%, 8/60) and 21 associated environmental samples (14.7%, 21/143). The contamination of <italic>L. monocytogenes</italic> in plants A and B was more severe and was likely to originate from the mycelium stimulation machine. The isolates belonged to serogroups II.1 (4b-4d-4e), I.1 (1/2a-3a), and I.2 (1/2c-3c), and multilocus sequence typing (MLST) revealed that these <italic>L. monocytogenes</italic> strains belonged to five different sequence types (ST3, ST121, ST9, ST87, and ST224). The ST121 and ST3 isolates were only found in plants A and B, respectively. The isolates were carried by <italic>hly</italic> (29/29, 100%), <italic>inlB</italic> (23/29, 79.3%), <italic>inlA</italic> (29/29, 100%), <italic>inlC</italic> (29/29, 100%), <italic>inlJ</italic> (29/29, 100%), <italic>actA</italic> (19/29, 65.5%), <italic>iap</italic> (29/29, 100%), <italic>plcA</italic> (26/29, 100%), <italic>plcB</italic> (29/29, 100%), <italic>prfA</italic> (27/29, 93.1%), and <italic>mpl</italic> (29/29, 100%). Further study of <italic>inlA</italic> sequencing showed that 65.5% of strains (19/29) contained full-length InlA that was required for host cell invasion, whereas the mutation led to premature stop codons (PMSCs) at position 492 (type 6) on <italic>inlA</italic> alleles. All isolates in this survey were sensitive to gentamicin, kanamycin, sulbactam/ampicillin, trimethoprim-sulfamethoxazole, tetracycline, and doxycycline. The drug with the highest resistance is rifampicin (37.9%), followed by penicillin (24.1%) and ciprofloxacin (10.3%). Most multiply resistant strains are isolated from raw materials and equipment of the <italic>P. eryngii</italic> processing lines. Our study reflects the contamination patterns and potential risk of <italic>L. monocytogenes</italic> infection in <italic>P. eryngii</italic> production plants. The persistence of specific <italic>L. monocytogenes</italic> isolates (such as ST121 and ST3) may assist with contamination. In accordance with these results, the control of <italic>L. monocytogenes</italic> should focus on the environmental materials, especially in the mycelium stimulation stage. However, effective <italic>Listeria</italic> monitoring programs will allow for the improved development of <italic>Listeria</italic> control measures to minimize cross-contamination in the processing of <italic>P. eryngii</italic>.</p>