Isolation of a potent antibiotic producer bacterium, especially against MRSA, from northern region of the Persian Gulf.

Nowadays, emergence and prevalence of MRSA (Methicillin Resistant Staphylococcus aureus) strain have become a great global concern in 21st century, so, it is necessary to discover new antibiotics against this pathogen. The aim of this study was isolation and evaluation marine bacteria from the Persian Gulf in order to finding antibiotic compounds against some pathogenic bacteria. For this purpose, water and sediment samples were collected from the Persian Gulf during March to October 2009. The antibacterial activity of the isolated bacteria was assessed using disc diffusion method. The Growth Curve Interference (GCI) parameter against MRSA was determined for the high potential antibiotic producing strain. The most important factors affecting fermentation conditions in antibiotic production were also optimized. Definite identification of intended isolate was confirmed by 16S rRNA sequencing. Altogether, 51 bacterial colony was isolated and among them only 3 bacterium showed antibacterial activity. Pseudoalteromonas piscicida PG-01 isolated from a sediment sample was chosen as the best antibiotic producing strain. This strain was effective against all tested Gram-positive bacteria, had good anti-MRSA activity and also GCI value against MRSA was two times lower than MIC value. Among the optimized fermentation parameters, carbon and nitrogen sources play major role in efficacy of optimized antibiotic production. Ultrastructural study on the effect of intended antibiotic compounds on MRSA using TEM revealed that the target site for this compound is cell wall. Considering the antibacterial effect of PG-01 strain especially against MRSA, intended antibiotic compounds can gives hope for treatment of diseases caused by multi-drug resistant bacteria.