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Identification and characterization of Tn phoA mutants of Salmonella that are unable to pass through a polarized MDCK epithelial cell monolayer
Author(s) -
Finlay B. B.,
Starnbach M. N.,
Francis C. L.,
Stacker B. A. D.,
Chatfield S.,
Dougan G.,
Falkow S.
Publication year - 1988
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/j.1365-2958.1988.tb00087.x
Subject(s) - mutant , biology , virulence , transcytosis , microbiology and biotechnology , intracellular , enterobacteriaceae , bacterial outer membrane , vibrio cholerae , endocytosis , gene , cell , genetics , escherichia coli , bacteria
Summary Surface protein mutants of the invasive Salmonella species, S. choleraesuis , were generated using the transposon TnphoA. 626 alkaline phosphatase (PhoA + ) fusion mutants were identified and screened for their ability to pass through (transcytose) polarized epithelial monolayers of Madin Darby canine kidney (MDCK) cells grown on membrane filters. Forty two mutants were unable to pass through this barrier. All of these transcytosis mutants were unable to adhere to or invade MDCK monolayers, yet these mutations were not in the genes encoding type 1 pili or mannose‐resistant haemagglutination (MRHA). These transcytosis mutants could be grouped into six classes. Class 1 mutants had altered lipopolysaccharide (LPS) O side‐chain structures while Class 2 mutants had defects in their LPS core. Mutants belonging to Classes 5 and 6 did not decrease the transepithelial electrical resistance of polarized MDCK cell mono‐layers, in contrast to the parental strain and the other mutants (Classes 1, 2, 3 and 4). Mutants belonging to Class 1 were less virulent in mice, while Class 2 (defective core) and Classes 4 and 5 (normal LPS) mutant strains were avirulent in mice. Mutants from Classes 3 and 6 were as virulent in mice as S. choleraesuis. These results suggest that the ability to pass through epithelial barriers may be an important virulence characteristic of Salmonella. These data indicate that bacterial adherence, internalization and monolayer transcytosis are closely linked events. It was also demonstrated that a mutant with decreased rates of intracellular replication still passed through the monolayer at rates similar to wild‐type S. choleraesuis.