Comparative Assessment of Bacteriophage and Antibiotic Activity against Multidrug-Resistant Staphylococcus aureus Biofilms

Abstract

Problems connected with biofilm-related infections and antibiotic resistance necessitate the investigation and development of novel treatment strategies. Given their unique characteristics, one of the most promising alternatives to conventional antibiotics are bacteriophages. In the in vitro and in vivo larva model study, we demonstrate that phages vB_SauM-A, vB_SauM-C, and vB_SauM-D are effective antibiofilm agents. The exposure of biofilm to phages vB_SauM-A and vB_SauM-D led to 2–3 log reductions in the colony-forming unit number in most of the multidrug-resistant S. aureus strains. It was found that phage application reduced the formed biofilms independently of the used titer. Moreover, the study demonstrated that bacteriophages are more efficient in biofilm biomass removal and reduction in staphylococci count when compared to the antibiotics used. The scanning electron microscopy analysis results are in line with colony forming unit (CFU) counting but not entirely consistent with crystal violet (CV) staining. Additionally, phages vB_SauM-A, vB_SauM-C, and vB_SauM-D can significantly increase the survival rate and extend the survival time of Galleria mellonella larvae.

Activity of Phage–Lactoferrin Mixture against Multi Drug Resistant Staphylococcus aureus Biofilms

“…Bacteriophages are an effective tool against biofilms formed by nosocomial, which are often multi-drug-resistant, strains of bacteria [ 20 , 21 ]. This has been proven by numerous studies by various research groups [ 8 , 22 , 23 ]. However, even though phages were successful where antibiotics have failed, they also seem to have their limitations [ 24 , 25 , 26 ].…”

“…Bacteriophages vB_SenM-A, vB_SauM-C and vB_SauM-D have previously been characterized and have proven activity against MDRSA biofilms when used alone [ 8 , 18 ]. In order to assess if phage and lactoferrin can be used simultaneously in the form of a cocktail, the phage–lactoferrin mixture was stored at 4 °C for a period of 5 days, with titration performed every 24 h. The phage titer began to drop after 3 days of incubation in case of phages vB_SauM-C and vB_SauM-D ( Figure 1 ).…”

“…In order to assess if lactoferrin will influence phage anti-biofilm activity, a phage–lactoferrin mixture was prepared. The mixture consisted of one of three previously characterized phages (vB_SauM-A, vB_SauM-C and vB_SauM-D) with proven activity against MDRSA strains [ 8 , 18 ]. Based on our previous studies and presented data on lactoferrin activity, we have chosen the concentration of phage to be 10 9 PFU/mL and 1.0 mg/mL for lactoferrin.…”

“…Since we have observed that there was no significant difference in activity between 1.0 mg/mL and 10 mg/mL concentrations of lactoferrin, we have chosen to use the lower concentration for our studies. The phage concentration was chosen to be 10 9 PFU/mL based on our previous reports [ 8 ]. We have observed that the use of a mixture resulted in significant decrease in all parameters: biomass, metabolic activity and CFU/mL of S. aureus biofilms after just 4 h of incubation.…”

“…Furthermore, individual cells can detach from the original biofilm and establish new sites of infection or mediate an acute infection such as sepsis [ 7 ]. Bacteriophages, the viruses that infect bacteria, have been shown to be able to successfully eradicate biofilms [ 8 , 9 ]. Phages can prevent biofilm formation and maturation by destroying bacteria in the outer layer of biofilm and planktonic cells.…”