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African Journal of Microbiology Research
8, No. 10, 2014; Pages: 1080-1088

Antibacterial effects of pure metals on clinically important bacteria growing in planktonic cultures and biofilms

AL Quthami Khalid, Bassam O. AlJohny and Milton Wainwright

Regional Laboratory,MOH, Makkak, Saudi Arabia.


Antibiotic resistance in pathogenic bacteria is emerging as an issue of serious concern in bio-medical research as well as food  and health organizations. Metal complexes are currently being employed in medical devices for their inhibition to bacterial adherence and antibacterial activities. The primary aim of this study was to evaluate the antibacterial activities of pure metals, including selenium, germanium and lithium on  planktonic  cultures and  biofilms of three bacterial species: S. aureus  SH1000,  P. aeruginosa PA01 and E. coli. O157:H7. The antagonistic effects of selenium, germanium and lithium on these three bacterial species were examined using zone of inhibition assay. The minimum inhibitory concentrations and minimum bactericidal concentrations  of antibiotics (rifampicin, mupirocin and ciprofloxacin) and metals (selenium, germanium and lithium) were measured. The minimum  biofilm eradication concentrations (MBEC) of metals were determined against biofilms composed of S. aureus SH1000 and P. aeruginosa PA01. Metal susceptibility tests suggested that biofilms displayed increased resistance over their planktonic state. Differential inhibitory effects were observed for different strains of planktonic and biofilm bacteria in response to different metals and their varying concentrations. Amongst the three metals tested, selenium proved to be the most active against all three species, whereas lithium demonstrated the least inhibitory effects. Scanning electron microscope (SEM) image analysis revealed several detrimental structural changes in bacterial cells exposed to metals compared to those grown in the metal-free culture. In conclusion, the results demonstrate the antibacterial efficacy of pure metals against planktonic and biofilm bacteria paving the way for further similar investigations in search of alternative antibacterial agents. 

Keywords:Antibiotic resistance; antibacterial; metal; biofilm; planktonic.

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