Isolation and Host Range of Lytic Staphylophages on Clinical Isolates of Methicillin-Resistant Staphylococcus aureus

Staphylococcus aureus (S. aureus) is a major cause of nosocomial infections in humans and animals. Because of the widespread resistance to antibiotics, microbiologists are trying to find other therapeutic interventions such as phage therapy for bacterial infections.

The present study aimed to isolate staphylophages with lytic effects on methicillin-resistant S. aureus (MRSA) clinical isolates as a potential alternative agent to antibiotic therapy.

This experimental, descriptive study is performed in the Microbiology Laboratory of Shahrekord University (Iran) from September 2018 to March 2019. Two cocktails of staphylophages were isolated from Isfahan (Iran) urban sewage samples. The double-layer agar method was used to detect lytic phages. Morphology characteristic by transmission electron microscopy (TEM) images was used to identify staphylophages. One hundred and thirty three S. aureus were isolated from clinical samples of two teaching hospitals in Isfahan and Shiraz, Iran. Methicillin resistance and the presence of the mecA gene were determined by the disk diffusion method and polymerase chain reaction (PCR) assay, respectively. The phage susceptibility of mecA positive isolates was determined by plaque assay.

Two staphylophage cocktails were prepared, which had lytic effects on forty-four MRSA isolates. Cocktails 1 and 2 lysed 19 (14.2%) and 25 (18.7%) isolates, respectively. Of 133 S. aureus isolates, 88.7% carried the mecA gene.

Different bacteriophages in two phage cocktails had relatively good lytic effects on S. aureus clinical isolates. Therefore, phage cocktails may be an appropriate alternative to antibiotics against S. aureus.