Isolation And Identification Of Staphylococcus Aureus Phage And Its Application In Dermatitis Treatment

Staphylococcus aureus is a primary bacterial pathogen of dermatitis and is also one reason for repeated dermatitis attacks.Antibiotics are commonly used as bacteriostatic agents to treat S.aureus induced or worsened dermatitis.Nevertheless,as the issue of antibiotic resistance has grown more and more severe in the last few years,it is of utmost importance to search for alternate antibacterial drugs.Bacteriophages were regarded as one of the most promising antibacterial drugs because of their specificity and the lack of toxicity or side effects on the human body.To investigate in a preliminarily way the possibility of applying bacteriophages in the treatment of dermatitis,we collected various S.aureus samples of healthy skin and dermatitis as test bacteria.Bacteriophages from environmental water were separated from the collected samples of S.aureus,and the bacteriostatic effect of single and mixed bacteriophages was investigated.The key results were as follows:(1)Ninety strains of Staphylococcus were isolated and purified in sample collection.By morphological,phenotypic,biochemical,and 16 S rDNA methods,ten different S.aureus strains were identified in the dermatitis group.The spa types and virulence genes were analyzed from the identified strains.Interestingly,all of these ten strains had been classified into ten different types of spa,and the Panton-Valentine leucocidin(pvl),the adhesion factor gene(clfa),and the exfoliative toxin gene(eta)had been all detected.The drug resistance test results showed that all isolates were resistant to at least one antibiotic,nearly 56% of the isolates were resistant to at least two antibiotics,and one strain was resistant to five antibiotics tested simultaneously.(2)Nine isolates with two control strains were used as host bacteria to isolate bacteriophages from environmental water samples.The 27 strains of bacteriophage were successfully identified after enrichment,purification,and identification.By measuring the lysis range of 27 bacteriophages against eleven host strains,we found six bacteriophages with the lysis range covering all strains tested and were selected to investigate bacteriophage cocktails.(3)The bacteriostatic effect of bacteriophage cocktails was better than that of a single bacteriophage and antibiotics.We determined the MOI of six bacteriophages to ten drugresistant host strains.To characterize the equal probability of infection of the host strains,we chose six different bacteriophage cocktails and eight types of antibiotics.The results showed that the mixed isolated S.aureus strains were resistant to 87% of the antibiotics.Meanwhile,the six cocktails could inhibit the growth of the mixed bacteria at a lower MOI ratio,and all showed a lysis effect.In addition,the cocktails had no significant inhibitory effect on Staphylococcus,which provided an essential reference for using bacteriophage cocktails in treating dermatitis.