Role of hemolysin for the intracellular growth of Listeria monocytogenes.

TLDR

The authors generated hemolysin‑deficient Listeria monocytogenes mutants using Tn916/Tn1545 transposons, tested intracellular replication in mouse macrophage, fibroblast, and human epithelial cell lines, and recovered hemolytic revertants by serial passage in J774 macrophages. Nonhemolytic mutants lacked hemolysin, were avirulent in mice, failed to replicate in murine cell lines but grew in human cells, whereas hemolytic revertants regained hemolysin, intracellular growth, and mouse virulence.

Abstract

Listeria monocytogenes insertion mutants defective in hemolysin production were generated using the conjugative transposons Tn916 and Tn1545. All of the nonhemolytic mutants (hly-) lacked a secreted 58-kD polypeptide, presumedly hemolysin, and were avirulent in a mouse model. An intracellular multiplication assay was established in monolayers of mouse bone marrow-derived macrophages, the J774 macrophage-like cell line, the CL.7 embryonic mouse fibroblast cell line, and the Henle 407 human epithelial cell line. The hly+ strain grew intracellularly in all of the tissue culture cells with a doubling time of approximately 60 min. In contrast, the hly- mutants failed to grow in the murine-derived tissue culture cells, but retained the ability to grow in the human tissue culture cells examined. Hemolytic-positive revertants were selected after passage of the hly- mutants through monolayers of J774 cells. In each case, the hemolytic revertants possessed the 58-kD polypeptide, were capable of intracellular growth in tissue culture monolayers and were virulent for mice.