The research study aims at finding out the different intercellular pathways that are adopted by bacterium to offer resistance against antimicrobial agents. For this research study they specifically used proteomic methodologies to find out characteristics of outer membrane proteins of E.coli K-12 and their response against two drugs tetracycline and ampicillin.
The antibiotics has been using for the resistibility against harmful bacterial organisms which infect the human or animal pathogens. It is true that bacterial organisms are not fully affected by use of antibiotic as there are almost five methods for a bacterium to get antimicrobial resistance. There is reduced permeability of antimicrobial agents which may have efficacy of antimicrobial in cell which may cause of mutation or enzymatic modification of antimicrobial. There is a need of exclusive explanation of molecular details of drug resistance which is the main instrument of understanding the entire mechanism of antibiotics. The efficacy of current antimicrobials is very significant for drug-resistant mechanism of multiple kinds of pathogens which disseminate into the cell so easily to achieve certain targets.
The gram-negative cell boundary is thinner than the gram-positive or mycobacterial cell wall, having double membrane (external membrane and cyto-plasmic membrane). The external membranes are workable for high intrinsic resistance of gram-negative bacteria to antimicrobial elements. For instance, the existence of Pseudomonas aeruginosa resistant to b-lactam antibiotics is the basic resistible material of b-lactamase, but low solute permeability across the external membrane. In fact, there are numerous methods for gram-negative bacteria to decrease anti-microbial efficacy and to enhance antimicrobial transportation via outer membrance proteins (Omps).
In the modern postgenomic era, proteomics has been considering as the big challenge for the biologists. The modern research & study of bacterial physiology and gene expression is related with really pathogenic bacterium.
E.coli K-12 strains were used for the study and cultured at 37oC overnight. Four different isolates were prepared. Minimum Inhibitory concentrations (MICs) for both anitibiotics, tetracycline and ampicillin were determined. Different bacterial isolates growth was observed in different MICs concentrations. Four strains were ampicilline MIC10, tetracycline MIC10, control10, and control10. With 2-DE and MALDI-TOF/MS methods, E.coli K-12 outer membrane proteome was characterized and identified. After treating the outer membrane proteins with tetracycline or ampicillin and determining the differential properties for resistance offered at different concentrations of tetracycline minimum inhibitory concentration (MIC)10 and ampicillin (MIC)10. These are compared with the controls (control10).
MICs were used at varying different concentrations of 3.125mg/mL to 25mg/mL for tetracycline and between 6.25 mg/mL to 200 mg/mL for ampicillin in 10 different series. Results showed at the MICs of 10, strains were resistant to both tetracycline and ampicillin.
The results showed only the difference of 1 protein between the two antibiotics, the outer membrane of E.coli had 11 altered spots with 9 proteins for tetracycline and 9 altered spots with 8 proteins for ampicillin. Three proteins were identified antibiotic resistant TolC, OmpC and YhiU. In addition, the antibiotic-resistant related proteins were reported as FimD precursor, LamB, Tsx, YfiO, OmpW, and NlpB. Results also suggest that bacterial strains survive more in ampicillin MIC10 as compared to tetracycline MIC10. In addition, the changes in outer membrane proteome were greater in tetracycline MIC10 as compared to corresponding ampicillin MIC10. Their study confirmed that combinations of various OMP purification methods are much useful in determining OMP sensitivity.
The current study employed the proteomic methods to determine OMPs in relation to resistance against tetracycline and ampicillin. The antibiotics were used at different concentrations in order to get better understanding of underlying pathways for resistance offered against antibiotics.
References
Changxin Xu2, Xiangmin Lin1, Haixia Ren2, Yueling Zhang2, SanyingWang2 and Xuanxian Peng (2006). Analysis of outer membrane proteome of Escherichia colirelated to resistance to ampicillin and tetracycline. Proteomics 2006, 6, 462–473