METHODS: B. subtilis was exposed to 5 to 150 μg/mL of ZnO NPs for 24 h. The parameters employed to evaluate the antimicrobial potential of ZnO NPs were the growth inhibitory effect on B. subtilis, the surface interaction of ZnO NPs on the bacterial cell wall, and also the morphological alterations in B. subtilis induced by ZnO NPs.
RESULTS: The results demonstrated a significant (p <0.05) inhibition of ZnO NPs on B. subtilis growth and it was in a dose-dependent manner for all the tested concentrations of ZnO NPs from 5 to 150 μg/mL at 24 h. Fourier transformed infrared (FTIR) spectrum confirmed the involvement of polysaccharides and polypeptides of bacterial cell wall in surface binding of ZnO NPs on bacteria. The scanning electron microscopy (SEM) was used to visualize the morphological changes, B. subtilis illustrated several surface alterations such as distortion of cell membrane, roughening of cell surface, aggregation and bending of cells, as well as, the cell rupture upon interacting with ZnO NPs for 24 h.
CONCLUSION: The results indicated the potential of ZnO NPs to be used as an antibacterial agent against B. subtilis. The findings of the present study might bring insights to incorporate ZnO NPs as an antibacterial agent in the topical applications against the infections caused by B. subtilis.
Methods: A total of 11 isolates from respiratory cultures in intensive care unit of a 24 bed tertiary hospital obtained over a one months period and one isolate obtained from the nebuliser during environmental screening were investigated. The bacteria were identified by Phoenix 100 system. The clonal relatedness was evaluated by PFGE and semi-automated repetitive sequence-based PCR. Genotyping tests were repeated for 10 serial subcultures.
Results: PFGE and DiversiLab yielded 10 genotypic profiles for 12 isolates. Four to eight different genotypes were observed from 10 subcultures of the same isolate.
Conclusion: We conclude that, high genetic diversity and supposed multiclonal appearance of the outbreak isolates may be due to changing profiles during subcultures most probably depending on hypermutation.