Biofilm Formation and Quorum-Sensing-Molecule Production by Clinical Isolates of Serratia liquefaciens.
Serratia spp. are opportunistic human pathogens responsible for an increasing number of nosocomial infections. However, little is known about the virulence factors and regulatory circuits that may enhance the establishment and long-term survival of Serratia liquefaciens in the hospital environment. In this study, two reporter strains, Chromobacterium violaceum CV026 and VIR24, and high-resolution triple-quadrupole liquid chromatography-mass spectrometry (LC-MS) were used to detect and to quantify N-acyl-homoserine lactone (AHL) quorum-sensing signals in 20 S. liquefaciens strains isolated from clinical samples. Only four of the strains produced sufficient amounts of AHLs to activate the sensors. Investigation of two of the positive strains by high-performance liquid chromatography (HPLC)-MS confirmed the presence of significant amounts of short-acyl-chain AHLs (N-butyryl-l-homoserine lactone [C4-HSL] and N-hexanoyl-l-homoserine lactone [C6-HSL]) in both strains, which exhibited a complex and strain-specific signal profile that included minor amounts of other short-acyl-chain AHLs (N-octanoyl-l-homoserine lactone [C8-HSL] and N-3-oxohexanoyl-l-homoserine lactone [OC6-HSL]) and long-acyl-chain (C10, C12, and C14) AHLs. No correlation between biofilm formation and the production of large amounts of AHLs could be established. Fimbria-like structures were observed by transmission electron microscopy, and the presence of the type 1 fimbrial adhesin gene fimH in all strains was confirmed by PCR. The ability of S. liquefaciens to adhere to abiotic surfaces and to form biofilms likely contributes to its persistence in the hospital environment, increasing the probability of causing nosocomial infections. Therefore, a better understanding of the adherence properties of this species will provide greater insights into the diseases it causes.
Servicio de Microbiología, Hospital Universitario Marqués de Valdecilla-IDIVAL, Santander, Cantabria, Spain.
Sara
S
Remuzgo-Martínez
Servicio de Microbiología, Hospital Universitario Marqués de Valdecilla-IDIVAL, Santander, Cantabria, Spain.
María
M
Lázaro-Díez
Departamento de Microbiología y Parasitología, Facultad de Biología, Universidad de Santiago de Compostela, Santiago de Compostela, Spain.
Celia
C
Mayer
Servicio de Microbiología, Hospital Universitario Marqués de Valdecilla-IDIVAL, Santander, Cantabria, Spain.
Maitane
M
Aranzamendi-Zaldumbide
Instituto Universitario de Sanidad Animal, Universidad de Las Palmas de Gran Canaria, Arucas, Gran Canaria, Spain.
Daniel
D
Padilla
Servicio de Microbiología, Hospital Universitario Marqués de Valdecilla-IDIVAL, Santander, Cantabria, Spain Red Española de Investigación en Patología Infecciosa (REIPI), Instituto de Salud Carlos III, Madrid, Spain.
Jorge
J
Calvo
Departamento de Microbiología Clínica, Hospital Clínic, CRESIB/IDIBAPS, Facultad de Medicina, Universidad de Barcelona, Barcelona, Spain.
Francesc
F
Marco
Servicio de Microbiología, Hospital Universitario Marqués de Valdecilla-IDIVAL, Santander, Cantabria, Spain Red Española de Investigación en Patología Infecciosa (REIPI), Instituto de Salud Carlos III, Madrid, Spain Departamento de Biología Molecular, Universidad de Cantabria, Santander, Cantabria, Spain.
Luis
L
Martínez-Martínez
Departamento de Anatomía y Biología Celular, Universidad de Cantabria, Santander, Cantabria, Spain.
José Manuel
JM
Icardo
Departamento de Microbiología y Parasitología, Facultad de Biología, Universidad de Santiago de Compostela, Santiago de Compostela, Spain.
Ana
A
Otero
Servicio de Microbiología, Hospital Universitario Marqués de Valdecilla-IDIVAL, Santander, Cantabria, Spain Red Española de Investigación en Patología Infecciosa (REIPI), Instituto de Salud Carlos III, Madrid, Spain jvivas@idival.org.
José
J
Ramos-Vivas
D015107:4-Butyrolactone / Q000031:analogs & derivatives / Q000378:metabolism; D018441:Biofilms; D003428:Cross Infection / Q000382:microbiology*; D006801:Humans; D053038:Quorum Sensing; D016868:Serratia Infections / Q000382:microbiology*; D044090:Serratia liquefaciens / Q000235:genetics / Q000302:isolation & purification / Q000502:physiology*
C088386:homoserine lactone; D015107:4-Butyrolactone