Synergism between Outer Membrane Proteins and Antimicrobials

Antibiotic-resistant bacteria are becoming one of the most important problems in health care because of the number of resistant strains and the paucity of new effective antimicrobials. Since antibiotic-resistant bacteria will continue to increase, it is necessary to look for new alternative strategies to fight against them. It is generally accepted that Gram-negative bacteria are intrinsically less susceptible than Gram-positive bacteria to antimicrobials. The main reason is that Gram-negative bacteria are surrounded by a permeability barrier known as the outer membrane (OM). Hydrophilic solutes most often cross the OM through water-filled channels formed by a particular family of proteins known as porins. This work explores the possibility of using exogenous porins to lower the required amounts of antibiotics (ampicillin, ciprofloxacin, cefotaxime, clindamycin, erythromycin, and tetracycline). Porins had a bactericidal effect on Escherichia coli cultures, mainly in the logarithmic phase of growth, when combined with low antibiotic concentrations. The use of different antibiotic-porin mixtures showed a bactericidal effect greater than those of antibiotics and porins when used separately. It was possible to observe different behaviors according to the antibiotic type used.