Effective Removal of Staphylococcal Biofilms by the Endolysin LysH5

Abstract

Staphylococcal biofilms are a major concern in both clinical and food settings because they are an important source of contamination. The efficacy of established cleaning procedures is often hindered due to the ability of some antimicrobial compounds to induce biofilm formation, and to the presence of persister cells, a small bacterial subpopulation that exhibits multidrug tolerance. Phage lytic enzymes have demonstrated antimicrobial activity against planktonic and sessile bacteria. However, their ability to lyse and/or select persister cells remains largely unexplored so far. In this work, the lytic activity of the endolysin LysH5 against Staphylococcus aureus and Staphylococcus epidermidis biofilms was confirmed. LysH5 reduced staphylococcal sessile cell counts by 1–3 log units, compared with the untreated control, and sub-inhibitory concentrations of this protein did not induce biofilm formation. LysH5-surviving cells were not resistant to the lytic activity of this protein, suggesting that no persister cells were selected. Moreover, to prove the lytic ability of LysH5 against this subpopulation, both S. aureus exponential cultures and persister cells obtained after treatment with rifampicin and ciprofloxacin were subsequently treated with LysH5. The results demonstrated that besides the notable activity of endolysin LysH5 against staphylococcal biofilms, persister cells were also inhibited, which raises new opportunities as an adjuvant for some antibiotics.

Identification of Peptidoglycan Hydrolase Constructs with Synergistic Staphylolytic Activity in Cow's Milk

“…Peptidoglycan hydrolases (PGHs) and bacteriophage endolysins in particular represent such novel types of antimicrobials and have received increasing attention due to their high killing efficacy, high specificity for the target pathogen, low chance of resistance development, and activity against dormant bacteria (9)(10)(11)(12). Endolysins are enzymes encoded by bacteriophage and produced inside the bacterial host cell at the end of the phage's lytic cycle, from which they get access to the cell wall and degrade their peptidoglycan (PG) substrate, ultimately resulting in cell lysis and release of progeny virions.…”

The Behavior of Staphylococcus aureus Dual-Species Biofilms Treated with Bacteriophage phiIPLA-RODI Depends on the Accompanying Microorganism

“…Serial dilutions of these suspensions were plated on selective medium for bacterial counting. Alternatively, the total biomass adhered to the well was determined by crystal violet (0.1%, wt/vol) staining as described previously (20). Each experiment was repeated at least three times.…”

“…Moreover, numerous studies have already shown the ability of phages to remove biofilms formed by a variety of bacteria, including staphylococcal species (15)(16)(17)(18). Additionally, phage-encoded proteins, such as endolysins and exopolysaccharide depolymerases, can also be used for biofilm removal (19)(20)(21). Nevertheless, most studies available to date have focused on single-species communities, while only limited work has tackled the elimination of polymicrobial biofilms with phage-based products (22)(23)(24)(25)(26).…”

Two Phages, phiIPLA-RODI and phiIPLA-C1C, Lyse Mono- and Dual-Species Staphylococcal Biofilms

“…Alternatively, the biomass adhered to the well was observed by staining with crystal violet (0.1% [wt/vol]) as described previously (25).…”