title: Haemophilus influenzae luxS mutants form a biofilm and have increased virulence.
abstract: To gain insight into the role of luxSHi in disease pathogenesis, we inactivated that gene in several non-typeable Haemophilus influenzae isolates with an antibiotic resistance cassette. Gene inactivation was confirmed by PCR and by Southern blot analysis in each strain. Culture filtrates from luxSHi mutants contained a decreased amount of autoinducer-2 (AI-2) activity in comparison to the wild-type isolates using the Vibrio harveyi BB170 bioassay. Culture filtrates from Escherichia coli strain DH5alpha expressing a cloned luxSHi contained 350-fold more AI-2 activity per cell than E. coli DH5alpha containing the vector alone. The growth rate in several liquid media, and the cell density after overnight growth were not significantly different between the parents and the luxSHi mutants. Two clinical H. influenzae and their luxSHi mutants produced an identical biofilm in a flow system. Invasion of human cells by the luxSHi mutants, in comparison to the wild-type parents was strain-dependent, and cell type-dependent, but the luxSHi mutants tended to be more invasive. The luxSHi mutant of an otitis media isolate, strain R3157 appeared more virulent in the chinchilla model of otitis media: there were more bacteria in the middle ear, a greater inflammatory response and more goblet cell hyperplasia 10 days after the inoculation. We conclude that the H. influenzae homologue of luxS modulates certain virulence traits.
authors.affiliation: Section on Microbial Pathogens, Seattle Biomedical Research Institute, 307 Westlake Ave North, Suite 500, Seattle, WA 98109-5219, USA.
authors.forename: Dayle A
authors.initials: DA
authors.lastname: Daines
authors.forename: Marcella
authors.initials: M
authors.lastname: Bothwell
authors.forename: Jason
authors.initials: J
authors.lastname: Furrer
authors.forename: William
authors.initials: W
authors.lastname: Unrath
authors.forename: Kevin
authors.initials: K
authors.lastname: Nelson
authors.forename: Justin
authors.initials: J
authors.lastname: Jarisch
authors.forename: Natalie
authors.initials: N
authors.lastname: Melrose
authors.forename: Laura
authors.initials: L
authors.lastname: Greiner
authors.forename: Michael
authors.initials: M
authors.lastname: Apicella
authors.forename: Arnold L
authors.initials: AL
authors.lastname: Smith
mesh_terms: D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics*; D018441:Biofilms / Q000254:growth & development*; D013437:Carbon-Sulfur Lyases; D045744:Cell Line, Tumor; D002682:Chinchilla; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D005260:Female; D006192:Haemophilus Infections / Q000382:microbiology*; D006193:Haemophilus influenzae / Q000235:genetics / Q000254:growth & development / Q000472:pathogenicity* / Q000648:ultrastructure; D006714:Homoserine / Q000031:analogs & derivatives / Q000235:genetics / Q000276:immunology; D006801:Humans; D007783:Lactones / Q000276:immunology; D008855:Microscopy, Electron, Scanning; D016254:Mutagenesis, Insertional; D010033:Otitis Media / Q000382:microbiology; D014774:Virulence
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; D007783:Lactones; C091088:N-octanoylhomoserine lactone; D006714:Homoserine; D013437:Carbon-Sulfur Lyases; C117753:LuxS protein, Bacteria