[Identification of a novel lytic bacteriophage obtained from clinical MRSA isolates and evaluation of its antibacterial activity]

Multidrug-resistant bacteria particularly MRSA is well known as a worldwide problem. Since the rate of development of novel antimicrobial agents has been slowed down during the last years, there have been a need for the exploration of alternative solutions for the treatment of resistant bacterial infections. Treatment of infections by bacteriophages (phages) that specifically kill the infecting pathogen, i.e. by the process known as phage therapy, is considered as a possible approach to treat multidrug resistant bacteria. Phage treatment has also been considered to treat Staphylococcus aureus infections. This study was aimed to evaluate the antibacterial and cytotoxic activities of a new lytic phage obtained from clinical MRSA strains. This lytic phage named as f LizAnk was obtained during the phage infectivity studies performed with 13 lysogenic phages against MRSA strains. The antibacterial activity of the f LizAnk phage was determined in vitro in BHI (Brain Heart Infusion) and LB (Leuria Bertani) broths and the in vivo antibacterial activity against MRSA strains and possible cytotoxic effect against mammalian cells were tested on fibroblastic cell cultures (3T3). This study was conducted using 20 MRSA strains isolated from hospitalized patients. Identification of the isolates was performed by conventional methods and methicillin resistance was detected with oxacillin disk diffusion test and mecA gene detection by PCR. The method described by Kaneko et al. [Biosci Biotechnol Biochem 1997; 61(11): 1960-2] was used with some modifications, for induction and isolation of the phages. In vitro studies indicated that this phage killed the six different MRSA strains (in 107 cfu/ml concentrations) in 8 hours, and this powerful lytic effect was similar in both of the liquid media. In vivo studies were performed by using cell cultures prepared in microplates, and the wells have been inoculated with only phage, phage + MRSA mixture, and only MRSA. The cells were then evaluated microscopically as well as by MTT assay which detected alive cells colorimetrically, at 2nd and 24th hours. In our study, the f LizAnk phage did not cause any toxic effect on fibroblast cell cultures, in addition it was observed that the antibacterial effect of the phage against MRSA has proceeded in the cell culture. In conclusion, since the fLizAnk phage described in this study exhibited strong antibacterial activity against MRSA strains and no cytotoxic effect was detected against mammalian cells, it might be safely used alone or in a phage cocktail to treat skin infection caused by MRSA.

Detection of herpes simplex virus type 1 in addition to Epstein-Bar virus in tonsils using a new multiplex polymerase chain reaction assay

HSV-1, HSV-2, CMV, EBV, which are the members of the herpes virus family colonize and establish latent infection in human. Although EBV is a well known virus most involved in recurrent bouts of acute tonsillitis, the role and possibility of HSV-1, HSV-2, and CMV for establishing infection in tonsils are not clear. The purpose of this study is to verify whether the tonsils might harbor the HSV-1, HSV-2, and CMV, in addition to EBV, in chronically hyperplastic nasopharyngeal lymphoid tissue. To accomplish the purpose, we developed a new Multiplex Polymerase Chain Reaction (M-PCR) assay using a single consensus forward primer and virus specific reverse primers for DNA polymerase gene of HSV-1, and 2, EBV, and CMV, and investigated its efficiency for detecting HSV1, HSV2, CMV, and EBV. The sample of 52 patients underwent tonsillectomy or adenectomy because of chronic lymphoid hyperplasia without any evidence of acute infections and were investigated for presence of HSV-1, HSV-2, CMV, and EBV. Of the 54 samples, 11 (20.4%) of them were positive for EBV, 4 of them (7.4%) were positive for HSV-1, and none of the samples were positive for HSV-2 and CMV. To the best of our knowledge, this is the first report that tonsils may be the reservoir for HSV-1 in addition to EBV, and HSV-1 may have a role in recurrent tonsillitis and systemic diseases. The MC-PCR assay presented in this study can provide a rapid, sensitive, and economical method for detection of HSV-1, HSV-2, EBV, and CMV in a single PCR tube.