Impact of triclosan adaptation on membrane properties, efflux and antimicrobial resistance of Escherichia coli clinical isolates.

AIM: Analysing the effect of step-wise exposure of Escherichia coli isolates to sublethal concentrations of triclosan (TCS) that is widely used as an antiseptic, preservative and disinfectant. METHODS AND RESULTS: Changes in the tolerance to the biocide itself and the cross-resistance to clinically important antibiotics were analysed. The involvement of efflux mechanism was studied as well as the possible implication of modifications in cytoplasmic membrane properties including integrity, permeability, potential and depolarization in the resistance mechanisms. Most of E. coli isolates that were adapted to TCS showed increased antimicrobial resistance, lower outer and inner membrane permeability, higher membrane depolarization, more negative membrane potential and enhanced efflux activity using qRT-PCR. Nonsignificant change in membrane integrity was found in the adapted cells. CONCLUSION: This study suggests that the extensive use of TCS at sublethal concentrations contributed to the emergence of antibiotic resistance in E. coli clinical isolates, by inducing changes in bacterial membrane properties and enhancing the efflux system. SIGNIFICANCE AND IMPACT OF THE STUDY: The extensive usage of TCS has a deleterious effect on the spread of antibiotic resistance, and more studies are needed to investigate the molecular mechanisms underlying the effects of TCS.

The role of some agricultural practices and fertilizer type on both the incidence of stem borers infestation and corn yield in Egypt.

Maize, Zea mays, L. is one of the most important field crops in Egypt. It is used mainly for human, animal and poultry feeding. Corn plants are usually attacked by several injourious insect pests at different stages of development. Out of them, the pink stem borer, Sesamia cretica (Led.), the purple lined borer, Chilo agamemnon (Bles.), and the European corn borer Ostrinia nubilalis (Hb.); which cause great damage and yield losses. It is profitable to adopt an effective and sustainable strategy for controlling these insect-pests. In this concern, sowing dates, planting spaces, foliar fertilizers (macro and micro-nutrients), mineral and/or biofertilization, were investigated to evaluate their role as tools in the so-called Integrated Pest Management (IPM) program of corn pests. In general, the used planting spaces of 60 and 70 cm apart between furrows insignificantly affected the level of stem borers infestation. It was clearly observed that the sowing dates have a role in the incidence of stem borers infestation throughout the corn growing seasons of 1994 and 1995. Moreover, The biofertilized corn plants were more tolerant to the infestation by the stem borers than the minerally fertilized ones. Application of Polytrin significantly decreased the mean numbers of larvae. The tested nutrients preparations affected to less extent, the infestation levels. Concerning the interaction effect of applied nutrients preparations, used sowing dates and/or fertilizer type on the deduced means of larval numbers, it was revealed that: (i) the application of the nutrients preparations decreased to a great extent the effect of the studied sowing dates on the stem borers infestation; particularly in case of spraying ascorbic acid alone or in sequence with Polymex, coppersulphate & Potasin-F, (ii) the dressing of corn grains with the biofertilizers Phosphorin & Rhizobacterin before sowing, lowered to some extent the levels of infestation by Ch. agamemnon and O. nubilalis, in comparison to the minerally fertilized corn plants, especially in case of spraying Potasin-F, copper sulphate and scorbic acid followed by Polymex for Ch. agamemnon. Spraying Ascorbic acid alone or in sequence with Polymex; Potasin-F followed by Copper sulphate gave promising results for the control of O. nubilalis. In comparison to insecticide treatment, the used foliar nutrients & fertilizer type in both sowing dates gave positive interaction effects in decreasing levels of stem borers infestation and greatly improved the yield and yield characteristics of corn plants. Such agricultural practices enabled corn plants to tackle the going on infestation; thus crop loss due to the attack of the stem borers could be compensated.