Biofilm Formation and Quorum-Sensing-Molecule Production by Clinical Isolates of Serratia liquefaciens

Abstract

AHLs. No correlation between biofilm formation and the production of large amounts of AHLs could be established. Fimbrialike 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. S erratia spp. are opportunistic Gram-negative bacteria that belong to the family Enterobacteriaceae. Serratia marcescens and Serratia liquefaciens are frequently encountered in nosocomial infections (1-4). S. liquefaciens is an increasingly recognized cause of transfusion-related sepsis and has been reported as a cause of meningitis, thrombophlebitis, corneal ulcers, and other infections (5-10). Moreover, Serratia species are inherently resistant to several antibiotics and are capable of readily acquiring resistance (11,12).N-Acylhomoserine lactone (AHL)-mediated quorum-sensing (QS) systems are cell density-dependent intercellular signaling mechanisms that regulate many physiological processes in Gramnegative bacteria. When the concentration of the molecule exceeds a threshold, signaling pathways are modulated, and the bacteria respond by modifying gene expression in a concerted manner throughout the population. This AHL-dependent QS system has been investigated extensively in S. marcescens strain MG1 (previously misidentified as S. liquefaciens) (13). Moreover, quorum sensing may play a role in biofilm formation in S. marcescens (14,15). A biofilm can be defined as a structured community of bacterial cells enclosed in a self-produced polymeric matrix and adherent to an inert or living surface. Growth in biofilms enhances the survival of bacterial populations in hospital environments and during host infections (i.e., in the presence of antibiotics), increasing the probability of causing nosocomial infections (16-18). In addition, some biocides used in hospitals are ineffective against nosocomial pathogens growing as biofilms attached to surfaces (19). Biofilm formation has been connected to infections associated with indwelling medical devices, such as central venous catheters, urinary catheters, and contact lenses (20). Also, in hospitals, some medicinal products need to be stored at lower than ambient temperatures to ensure their quality and efficacy (vaccines, insulin, biotechnology products, drugs, etc.). Moreover, red blood cells or whole blood must always be stored at a temperature between 2 and 6°C to maintain the oxygen-carrying ability of blood and to minimize bacterial contamination. However, some psychrophilic, primarily Gram-negative pathogenic bacteria can proliferate from very low to clinically significant concentrations under storage conditions. The goal of the present study was ...

Multiple Quorum Quenching Enzymes Are Active in the Nosocomial Pathogen Acinetobacter baumannii ATCC17978

“…A wide range of intraspecific variability was also found in the AHL profile within A. baumannii clinical isolates, since OHC12-HSL was present in only 4 of 7 strains when cultured in the rich LB medium. Intraspecific variation in AHL profile has been also reported in other important pathogens, such as Serratia liquefaciens (Remuzgo-Martínez et al, 2015 ). In the case of A. baumannii , these differences could be derived from differences in the control of the expression of the abaI synthase that is present in all isolates, or in the QQ activity, that was also present in all of them.…”

DqsIR quorum sensing‐mediated gene regulation of the extremophilic bacterium Deinococcus radiodurans in response to oxidative stress

“…AHLs were identified and confirmed by comparing the retention times and the spectra with synthetic standards (C6‐HSL, C10‐HSL, 3OC10‐HSL, and C12‐HSL; Sigma). The AHL content was measured by comparison with a calibration curve generated with each of the appropriate AHL synthetic standards (Remuzgo‐Martínez et al ., ).…”

Effect of Capsicum Frutescens Extract, Capsaicin, and Luteolin on Quorum Sensing Regulated Phenotypes

“…Nonetheless, Remuzgo‐Martínez et al. () showed that clinical isolates of S. marcescens formed denser biofilms at 24 °C than at 37 °C on plastic surfaces. These evidences suggest that incubation temperature is a determining factor in bacterial BF, since microorganisms might adapt differently in the environment or in the host depending on the temperature, among other factors.…”