Increased tolerance ofStaphylococcus aureusto vancomycin in viscous media

Abstract

The increased viscosity observed in biofilms, adherent communities of bacterial cells embedded in a polymeric matrix, was hypothesized to induce increased tolerance of bacteria to antibiotics. To test this concept, planktonic Staphylococcus aureus cells were grown and exposed to vancomycin in media brought to specific viscosities in order to mimic the biofilm extracellular polymeric matrix. A viscous environment was observed to decrease the vancomycin susceptibility of planktonic S. aureus to levels seen for biofilms. Both planktonic S. aureus at a viscosity of 100 mPa s and staphylococcal biofilms were able to survive at >500 times the levels of the antibiotic effective against planktonic populations in standard medium. Time-dependent and dose-dependent viability curves revealed that more than one mechanism was involved in high S. aureus tolerance to vancomycin in viscous media. Increased viscosity affects antibiotic susceptibility by reducing diffusion and the mass transfer rate; this mechanism alone, however, cannot explain the increased tolerance demonstrated by S. aureus in viscous media, suggesting that viscosity may also alter the phenotype of the planktonic bacteria to one more resistant to antimicrobials, as seen in biofilms. However, these latter changes are not yet understood and will require further study.

Reduced Vancomycin Susceptibility in anIn VitroCatheter-Related Biofilm Model Correlates with Poor Therapeutic Outcomes in Experimental Endocarditis Due to Methicillin-Resistant Staphylococcus aureus

“…In contrast, there were no significant differences in MRSA clearance by VAN within catheter biofilms formed by non-Rsp isolates. The precise mechanism(s) of this suboptimal MRSA clearance by VAN within non-Rsp-induced catheter biofilms is not well understood, but it will likely include their distinct biofilm compositions, limitations of VAN biofilm penetration, the evolution of "persister" cell populations within the depths of the biofilm, and/or VAN-induced enhancement of biofilm formation (13,48,49).…”

Modulation of the Local Neutrophil Response by a Novel Hyaluronic Acid-Binding Peptide Reduces Bacterial Burden during Staphylococcal Wound Infection

“…4C). Furthermore, PEP35 was capable of reducing tissue bacterial burden when a potent biofilm-forming HA-MRSA strain (UC-18 [24,25]) was used (see Fig. S2 in the supplemental material).…”

Interdependence between iron acquisition and biofilm formation in Pseudomonas aeruginosa

“…First, they enrobe the bacteria in EPS, limiting the diffusion of biocides and antibacterials and their access to cells (Mah and O’Toole, 2001; Anderson and O’Toole, 2008). For example, a number of studies have shown a correlation between biofilm viscosity and antimicrobial sensitivity (Stewart, 1996; Gilbert et al ., 1998; Wirtanen et al ., 1998; Kostenko et al ., 2007; Ruhs et al ., 2013). Genetic disruption or chemical inhibition of biofilm formation also increases pathogen susceptibility to antimicrobial agents (Rashid et al ., 2000; Shih and Huang, 2002; Li and Lee, 2017).…”