Hyper-Virulent Listeria monocytogenes Strains Associated With Respiratory Infections in Central Italy.

Listeria monocytogenes (Lm) is a foodborne pathogen causing listeriosis. Invasive forms of the disease mainly manifest as septicaemia, meningitis and maternal-neonatal infections. Lm-associated respiratory infections are very rare and little known. We reported two Lm respiratory infection cases occurred in Central Italy during the summer of 2020, in the midst of the SARS-CoV2 pandemic. In addition to collect the epidemiological and clinical characteristics of the patients, we used Whole Genome Sequencing to study the genomes of the Lm isolates investigating their virulence and antimicrobial profiles and the presence of genetic mobile elements. Both the strains belonged to hypervirulent MLST clonal complexes (CC). In addition to the Listeria Pathogenicity Island 1 (LIPI-1), the CC1 strain also carried LIPI-3 and the CC4 both LIPI-3 and LIPI-4. Genetic determinants for antimicrobial and disinfectants resistance were found. The CC1 genome presented prophage sequences but they did not interrupt the comK gene, involved in the phagosomal escape of Lm. None of the strains carried plasmids. Lm is an important, although rare, opportunistic pathogen for respiratory tract and lung infections. To avoid dangerous diagnostic delays of these severe clinical forms, it is important to sensitize hospital laboratories to this rare manifestation of listeriosis considering Lm in the differential diagnosis of respiratory infections.

Hypo- and Hyper-Virulent Listeria monocytogenes Clones Persisting in Two Different Food Processing Plants of Central Italy.

A total of 66 Listeria monocytogenes (Lm) isolated from 2013 to 2018 in a small-scale meat processing plant and a dairy facility of Central Italy were studied. Whole Genome Sequencing and bioinformatics analysis were used to assess the genetic relationships between the strains and investigate persistence and virulence abilities. The biofilm forming-ability was assessed in vitro. Cluster analysis grouped the Lm from the meat plant into three main clusters: two of them, both belonging to CC9, persisted for years in the plant and one (CC121) was isolated in the last year of sampling. In the dairy facility, all the strains grouped in a CC2 four-year persistent cluster. All the studied strains carried multidrug efflux-pumps genetic determinants (sugE, mdrl, lde, norM, mepA). CC121 also harbored the Tn6188 specific for tolerance to Benzalkonium Chloride. Only CC9 and CC121 carried a Stress Survival Islet and presented high-level cadmium resistance genes (cadA1C1) carried by different plasmids. They showed a greater biofilm production when compared with CC2. All the CC2 carried a full-length inlA while CC9 and CC121 presented a Premature Stop Codon mutation correlated with less virulence. The hypo-virulent clones CC9 and CC121 appeared the most adapted to food-processing environments; however, even the hyper-virulent clone CC2 warningly persisted for a long time. The identification of the main mechanisms promoting Lm persistence in a specific food processing plant is important to provide recommendations to Food Business Operators (FBOs) in order to remove or reduce resident Lm.

A bicistronic CYCLIN D1-TROP2 mRNA chimera demonstrates a novel oncogenic mechanism in human cancer.

A chimeric CYCLIN D1-TROP2 mRNA was isolated from human ovarian and mammary cancer cells. The CYCLIN D1-TROP2 mRNA was shown to be a potent oncogene as it transforms naïve, primary cells in vitro and induces aggressive tumor growth in vivo in cooperation with activated RAS. Silencing of the chimeric mRNA inhibits the growth of breast cancer cells. The CYCLIN D1-TROP2 mRNA was expressed by a large fraction of the human gastrointestinal, ovarian, and endometrial tumors analyzed. It is most frequently detected in intestinal cell aneuploid cancers and it is coexpressed with activated RAS oncogenes, consistent with a cooperative transforming activity in human cancers. The chimeric mRNA is a bicistronic transcript of post transcriptional origin that independently translates the Cyclin D1 and Trop-2 proteins. This is a novel mechanism of CYCLIN D1 activation that achieves the truncation of the CYCLIN D1 mRNA in the absence of chromosomal rearrangements. This leads to a higher CYCLIN D1 mRNA stability, with inappropriate expression during the cell cycle. The stabilized CYCLIN D1 mRNA cooperates with TROP2 in stimulating the growth of the expressing cells. These findings show a novel epigenetic, oncogenic mechanism, which seems to be widespread in human cancers.

Trop-1 are conserved growth stimulatory molecules that mark early stages of tumor progression.

BACKGROUND: Trop-1 is a cell-cell adhesion regulatory molecule that is overexpressed by a large fraction of tumors in man. METHODS: To identify fundamental, conserved functional features of Trop-1 in transformed cells, a search was performed for evolutionarily conserved structure, expression patterns, and function by gene cloning, DNA array and serial analysis of gene expression (SAGE), Northern and Western blotting, flow cytometry, and immunohistochemistry of sequential stages of tumor progression in experimental systems and in man. RESULTS: TROP1 genes demonstrate conserved structure and promoter regions with parallel expression patterns (high expression in the small intestine and colon; lower expression in prostate, thyroid, salivary glands, breast, kidney, lung, liver, and spleen; very low levels in skin and stomach; no expression in heart, muscle, and brain). Progenitor cells of different tissues were shown to express Trop-1. Hence, the expression and functional role of Trop-1 were analyzed at successive stages of tumor progression in vitro and in vivo. The findings show that Trop-1 is expressed at early stages of tumor development, eg, in dysplastic lesions and immortalized cells, is sufficient to stimulate cell growth of expressing transformed cells, and is required for tumor growth in vivo. CONCLUSIONS: The findings identify Trop-1 as a novel determinant of cell growth at early stages of tumor development and as a marker of early stages of development in normal tissues and in cancer, making this molecule a candidate for novel diagnostic and therapeutic procedures.

Mutations of TP53 induce loss of DNA methylation and amplification of the TROP1 gene.

p53 and DNA methylation play key roles in the maintenance of genome stability. In this work, we demonstrate that the two mechanisms are linked and that p53 plays a role in the maintenance of the DNA methylation levels. The loss of p53 was shown to induce loss of DNA methylation in the TROP1 gene, a human cancer-expressed locus that undergoes amplification when hypomethylated. This demethylation was reverted by the reintroduction of a wild-type TP53 (wtTP53) in the TP53-null cells. Using a gene-amplification assay in vivo, we demonstrate that the loss of p53 leads to a demethylation-dependent TROP1 gene amplification. The induction of gene amplification was reverted by the expression of a wtTP53 gene or by in vitro methylation of the transfected DNA with the Sss I DNA methylase. Taken together, these findings demonstrate that the inactivation of TP53 induces loss of DNA methylation and DNA methylation-dependent gene amplification.