Pseudomonas aeruginosa is a leading cause of human morbidity and mortality, and it often targets epithelial surfaces. It procures pathogenicity by secreting outer membrane vesicles (OMVs) as a virulence factor. This study was aimed at determining the amount of OMVs of two strains of Pseudomonas aeruginosa, and evaluate the cytotoxicity of the isolated vesicles on human keratinocyte cell line (HaCaT). The results indicate that virulence factor of isolates from hospital strain was comparatively higher compared with the laboratory strain. This is consistent with earlier findings that the toxicity of hospital strain outweighed the laboratory strain. Laboratory strain that was treated with gentamicin showed a higher amount of OMVs compared with untreated strain. The antibiotic stimulated the bacteria to secrete more virulence factors seeking for protection. The number of bacteria (CFU) is inversely proportional to the release of OMVs. The toxic effect of outer membrane vesicles which acted as stress factor showed a loss of biomass in hospital strain and a moderate increase in the laboratory strain, and that supports earlier findings that hospital strains are more toxic. Cells biomass indicate the cells continue to grow rapidly even when they are treated with low concentrations of OMVs.

Using microwave oven nowadays has become necessary due to the need for speed in our daily activities. It is widely used in hating, thawing, and even cooking of food. It has been also used in sterilization and decontamination of food from microorganisms. This study aimed to evaluate thermal and non-thermal effect of a regular house holding microwave oven on Staphylococcus aureus and Escherichia coli. Bacterial suspension is exposed to microwave radiations in different strength and durations and compared to unexposed cultures. During microwave treatment, non-thermal effect is evaluated by putting the suspension crushed ice. The results indicate that the viability of both gram positive and negative was highly reduced with thermal effect of microwave radiations, leading to complete inactivation at three minutes. Non-thermal microwave radiations were also able to cause change in the microbial viability of both tested organisms on at least two-exposure occasion. The evaluation of antibiotic susceptibility before and after microwave radiations treatment indicate that antibiotic resistance was highly increased to tested antibiotics specially after three-minute exposure, except for Staphylococcus aureus to Amoxicillin, which became more sensitive. Microwave radiations reported to have a strong activity in eliminating the number of microbes but, it may have an important role in development of antibiotic resistance that should not be ignored.