ABSTRACT
 
Pseudomonas species are prominent opportunist pathogens. The present study was undertaken to detect the prevalence of Pseudomonas spp. in cheese and focused on the antibacterial effect of onion peel extract (Allium Cepa) and its nano-emulsion against Pseudomonas aeroginosa. One hundred and fifty samples of kareish, tallaga and cheddar cheese (50 samples each) were collected from dairy shops and supermarkets. The prevalence of the organism was 40%, 30% and 24% in the examined samples, respectively. The most prominent species were P. aeruginosa, P. fluorescens, P. fragi, P. putrefaciens, P. proteolytica and P.alcaligenes. The isolates of P. aeruginosa were confirmed by PCR utilizing the 16S rRNA gene. The results of antibiotic sensitivity revealed that the highest antimicrobial resistance was recorded for Ampicillin (100%) and the highest sensitivity was reported for Cefotaxin (100%). AC and AC nano-emulsions were added at a concentration of 3.12 and 1.56 % in the laboratory-made kareish cheese. There was an evident antimicrobial effect on P. aeruginosa growth particularly for AC nano-emulsion, where, complete inhibition of the organism was observed on the 5th day. The prepared AC nano-emulsion had a Z-average diameter of 178.32± 65.73 nm and a polydispersity index (PDI) of 0.223. In examining the prepared nano-emulsion by Transmission Electron Microscope (TEM), the spherical shape was revealed and the size was 48.78 nm and the flow of active functional groups was clarified by Fourier-transform infrared spectroscopy (FTIR). Utilizing nano AC at a concentration of 1.56 % ensured its antibacterial activity on P.aeroginosa and did not affect on OAA of cheese.
 
Keywords: Allium Cepa, nano-emulsion, kareish cheese, cheddar cheese, Pseudomonas aeruginosa