title: Requirement for Serratia marcescens cytolysin in a murine model of hemorrhagic pneumonia.
abstract: Serratia marcescens, a member of the carbapenem-resistant Enterobacteriaceae, is an important emerging pathogen that causes a wide variety of nosocomial infections, spreads rapidly within hospitals, and has a systemic mortality rate of ≤41%. Despite multiple clinical descriptions of S. marcescens nosocomial pneumonia, little is known regarding the mechanisms of bacterial pathogenesis and the host immune response. To address this gap, we developed an oropharyngeal aspiration model of lethal and sublethal S. marcescens pneumonia in BALB/c mice and extensively characterized the latter. Lethal challenge (>4.0 × 10(6) CFU) was characterized by fulminate hemorrhagic pneumonia with rapid loss of lung function and death. Mice challenged with a sublethal dose (<2.0 × 10(6) CFU) rapidly lost weight, had diminished lung compliance, experienced lung hemorrhage, and responded to the infection with extensive neutrophil infiltration and histopathological changes in tissue architecture. Neutrophil extracellular trap formation and the expression of inflammatory cytokines occurred early after infection. Mice depleted of neutrophils were exquisitely susceptible to an otherwise nonlethal inoculum, thereby demonstrating the requirement for neutrophils in host protection. Mutation of the genes encoding the cytolysin ShlA and its transporter ShlB resulted in attenuated S. marcescens strains that failed to cause profound weight loss, extended illness, hemorrhage, and prolonged lung pathology in mice. This study describes a model of S. marcescens pneumonia that mimics known clinical features of human illness, identifies neutrophils and the toxin ShlA as a key factors important for defense and infection, respectively, and provides a solid foundation for future studies of novel therapeutics for this important opportunistic pathogen.
authors.affiliation: Department of Microbiology and Immunology, Center for Airway Inflammation Research, The University of Texas Health Sciences Center at San Antonio, San Antonio, Texas, USA.
authors.forename: Norberto
authors.initials: N
authors.lastname: González-Juarbe
authors.affiliation: Department of Microbiology and Immunology, Center for Airway Inflammation Research, The University of Texas Health Sciences Center at San Antonio, San Antonio, Texas, USA.
authors.forename: Chris A
authors.initials: CA
authors.lastname: Mares
authors.affiliation: Department of Microbiology and Immunology, Center for Airway Inflammation Research, The University of Texas Health Sciences Center at San Antonio, San Antonio, Texas, USA.
authors.forename: Cecilia A
authors.initials: CA
authors.lastname: Hinojosa
authors.affiliation: Department of Microbiology and Immunology, Center for Airway Inflammation Research, The University of Texas Health Sciences Center at San Antonio, San Antonio, Texas, USA.
authors.forename: Jorge L
authors.initials: JL
authors.lastname: Medina
authors.affiliation: Department of Microbiology and Immunology, Center for Airway Inflammation Research, The University of Texas Health Sciences Center at San Antonio, San Antonio, Texas, USA.
authors.forename: Angelene
authors.initials: A
authors.lastname: Cantwell
authors.affiliation: Department of Microbiology and Immunology, Center for Airway Inflammation Research, The University of Texas Health Sciences Center at San Antonio, San Antonio, Texas, USA.
authors.forename: Peter H
authors.initials: PH
authors.lastname: Dube
authors.affiliation: Department of Microbiology and Immunology, Center for Airway Inflammation Research, The University of Texas Health Sciences Center at San Antonio, San Antonio, Texas, USA orihuela@uthscsa.edu.
authors.forename: Carlos J
authors.initials: CJ
authors.lastname: Orihuela
authors.affiliation: Department of Microbiology and Immunology, Center for Airway Inflammation Research, The University of Texas Health Sciences Center at San Antonio, San Antonio, Texas, USA.
authors.forename: Molly A
authors.initials: MA
authors.lastname: Bergman
mesh_terms: D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics*; D001992:Bronchoalveolar Lavage Fluid / Q000166:cytology; D003428:Cross Infection; D016207:Cytokines / Q000096:biosynthesis / Q000276:immunology; D004195:Disease Models, Animal; D005260:Female; D006460:Hemolysin Proteins / Q000235:genetics*; D006470:Hemorrhage / Q000382:microbiology / Q000473:pathology; D007249:Inflammation / Q000276:immunology; D008168:Lung / Q000276:immunology / Q000382:microbiology / Q000473:pathology; D051379:Mice; D008807:Mice, Inbred BALB C; D020556:Neutrophil Infiltration / Q000276:immunology; D009504:Neutrophils / Q000276:immunology; D011014:Pneumonia / Q000276:immunology / Q000382:microbiology / Q000401:mortality / Q000473:pathology*; D016868:Serratia Infections / Q000276:immunology* / Q000382:microbiology / Q000401:mortality; D012706:Serratia marcescens / Q000276:immunology* / Q000472:pathogenicity
chemical_list: D001426:Bacterial Proteins; D016207:Cytokines; D006460:Hemolysin Proteins; C089911:ShlA protein, Serratia marcescens; C107896:ShlB protein, Serratia marcescens