Whole-genome sequencing links cases dispersed in time, place, and person while supporting healthcare worker management in an outbreak of Panton-Valentine leucocidin meticillin-resistant Staphylococcus aureus; and a review of literature

This is a report on an outbreak of Panton-Valentine leucocidin-producing meticillin-resistant Staphylococcus aureus (PVL-MRSA) in an intensive care unit (ICU) during the COVID-19 pandemic that affected seven patients and a member of staff. Six patients were infected over a period of ten months on ICU by the same strain of PVL-MRSA, and a historic case identified outside of the ICU. All cases were linked to a healthcare worker (HCW) who was colonized with the organism. Failed topical decolonization therapy, without systemic antibiotic therapy, resulted in ongoing transmission and one preventable acquisition of PVL-MRSA. The outbreak identifies the support that may be needed for HCWs implicated in outbreaks. It also demonstrates the role of whole-genome sequencing in identifying dispersed and historic cases related to the outbreak, which in turn aids decision-making in outbreak management and HCW support. This report also includes a review of literature of PVL-MRSA-associated outbreaks in healthcare and highlights the need for review of current national guidance in the management of HCWs' decolonization regimen and return-to-work recommendations in such outbreaks.

[Double immunoenzymatic and two-color flow cytometric analyses of tonsillar T-cell subsets]

Distribution of various T-cell subsets in the palatine tonsil was investigated by two-color flow cytometry and double immunoenzymatic stain. Tonsillar lymphocytes contained many (about 20%) helper T (CD4+ Leu8-) cells and few (only 1%) suppressor T (CD8+ CD11b+) cells. In interfollicular area, each T-cell subset, i.e., helper, helper-inducer (CD4+ CD29+), suppressor-inducer (CD4+ CD45RA+), cytotoxic (CD8+ CD11b-), and suppressor, was identified by double immunoenzymatic labeling technique using alkaline phosphatase and peroxidase. On the other hand, only two T-cell subsets, helper, and cytotoxic T-cell subpopulations, were recognized in germial center. These results indicate that double immunoenzymatic stain as well as two-color flow cytometry gives us useful informations in terms of tonsillar T-cell subsets.

[Immunohistological identification of the activated lymphocytes in human palatine tonsil]

Employing various monoclonal antibodies and immunoperoxidase technique, we studied the distribution of the activated lymphocytes in human tonsillar tissue. Both the activated T-cells positive for IL2-receptor (IL2-R) and the activated B-cells defined by L29 were seen in the interfollicular area. Vast majority of the lymphocytes in the germinal center was stained with the L29, the anti-transferrin-receptor antibody, and the Ki-67 antibody which reacts with cycling cells in G1, S, or G2 + M phase. On the other hand, scarcely any cells in the mantle zone were stained with those. The Ki-67 positive cells in the germinal center were identified as two types of staining pattern, i.e., with strong nucleolar staining found in the dark zone and with nuclear staining found in the light zone. Small number of IL2-R positive cells was found in the mantle zone. The cell number per unit area of the activated lymphocytes in the interfollicular area as well as in the germinal center was decreased as the increment of patients' age. From these results, the immunological activation system of T- and B-cells in the tonsils was discussed.