Activity of the lyases LysSSE1 and HolSSE1 against common pathogenic bacteria and their antimicrobial efficacy in biofilms

Characterization and application of LysSGF2 and HolSGF2 as potential biocontrol agents against planktonic and biofilm cells of common pathogenic bacteria

Antimicrobial resistance represents a global health emergency, necessitating the introduction of novel antimicrobial agents. In the present study, lysozyme and holin from Shigella flexneri 1.1868 phage SGF2, named LysSGF2 and HolSGF2, respectively, were cloned, expressed, and characterized. LysSGF2 and HolSGF2 showed lytic activities against S. flexneri 1.1868 cells at 4-55 °C and pH 3.1-10.3. LysSGF2 exhibited antimicrobial activity against five gram-negative and two gram-positive bacteria. HolSGF2 showed antimicrobial activity against four gram-negative and one gram-positive species. The antibacterial activities of LysSGF2 and HolSGF2 were determined in liquid beverages, including bottled water and milk. The relative lytic activity of LysSGF2 combined with HolSGF2 against the tested bacteria was approximately 46-77 % in water. Furthermore, the combination markedly decreased the viable counts of tested bacteria by approximately 3-5 log CFU/mL. LysSGF2 and HolSGF2 could efficiently remove biofilms on polystyrene, glass, and stainless-steel. The efficacy of the LysSGF2 and HolSGF2 combination against the tested bacteria on polystyrene was 58-71 %. Combination treatment effectively killed biofilm cells formed on stainless-steel and glass by 1-4 log CFU/mL. ese results indicate that LysSGF2 and HolSGF2 can successfully control both the planktonic and biofilm cells of common pathogenic bacteria, suggesting that the combined or single use of LysSGF2 and HolSGF2 may be of great value in food processing.

A Review of Phage Therapy for Bone and Joint Infections

There is a strong rationale for using phages in patients with bone and joint infections (BJIs). Indeed, specific phages can infect and replicate in bacterial pathogens and have also demonstrated their activity in vitro against biofilm produced by different bacteria. However, there is a high variability of the different clinical forms of BJI, and their management is complex and frequently includes surgery followed by the administration of antibiotics. Regardless of the availability of active phages, optimal ways of phage administration in patients with BJIs are unknown. Otherwise, all BJIs are not relevant for phage therapy. Except for diabetic foot infection, a BJI with bone exposure is potentially not a relevant indication for phage therapy. On the counterpart, prosthetic joint infections in patients for whom a multidisciplinary expert team judges a conservative approach as the best option to keep the patient's function seem to be a relevant indication with the hypothesis that phage therapy could increase the rate of infection control. The ESCMID Study Group for Non-traditional Antibacterial Therapy (ESGNTA) was created in 2022. One century after the first use of phages as a therapy, the phage therapy 2.0 era, with the possibility to evaluate personalized phage therapy in modern medicine and orthopedic surgery, is just open.

Synergistic action of phages and lytic proteins with antibiotics: a combination strategy to target bacteria and biofilms

BACKGROUND

Multidrug-resistant bacteria continue to emerge owing to the abuse of antibiotics and have a considerable negative impact on people and the environment. Bacteria can easily form biofilms to improve their survival, which reduces the efficacy of antibacterial drugs. Proteins such as endolysins and holins have been shown to have good antibacterial activity and effectively removal bacterial biofilms and reduce the production of drug-resistant bacteria. Recently, phages and their encoded lytic proteins have attracted attention as potential alternative antimicrobial agents. The aim of the present study was to investigate the sterilising efficacy of phages (SSE1, SGF2, and SGF3) and their encoded lytic proteins (lysozyme and holin), and to further explore their potential in combination with antibiotics. To the ultimate aim is to reduce or replace the use of antibiotics and provide more materials and options for sterilisation.

RESULTS

Phages and their encoded lytic proteins were confirmed to have great advantages in sterilisation, and all exhibited significant potential for reducing bacterial resistance. Previous studies on the host spectrum demonstrated the bactericidal efficacy of three Shigella phages (SSE1, SGF2, and SGF3) and two lytic proteins (LysSSE1 and HolSSE1). In this study, we investigated the bactericidal effects on planktonic bacteria and bacterial biofilms. A combined sterilisation application of antibiotics, phages, and lytic proteins was performed. The results showed that phages and lytic proteins had better sterilisation effects than antibiotics with 1/2 minimum inhibitory concentrations (MIC) and their effect was further improved when used together with antibiotics. The best synergy was shown when combined with β- lactam antibiotics, which might be related to their mechanism of sterilising action. This approach ensures a bactericidal effect at low antibiotic concentrations.

CONCLUSIONS

This study strengthens the idea that phages and lytic proteins can significantly sterilise bacteria in vitro and achieve synergistic sterilisation effects with specific antibiotics. Therefore, a suitable combination strategy may decrease the risk of drug resistance.