Ana Isabel Barnes

Sublethal ciprofloxacin treatment leads to resistance via antioxidant systems in Proteus mirabilis

This study investigates new aspects of the possible role of antioxidant defenses in the mechanisms of resistance to ciprofloxacin in Proteus mirabilis. Four ciprofloxacin-resistant variants (CRVs), selected in vitro by repeated cultures in a sub-minimum inhibitory concentration (MIC) concentration of ciprofloxacin, attained different levels of antibiotic resistance and high Ferric reducing antioxidant power, with 10(-6) frequencies. However, no mutations occurred in positions 83 or 87 of gyrA, 464 or 466 of gyrB, or 78, 80 or 84 of parC, suggesting that resistance took place without these typical mutations in DNA gyrase or topoisomerase IV. Assays with ciprofloxacin and the pump inhibitor carbonyl cyanide m-chlorophenylhydrazone showed that in addition to the antioxidant mechanisms, the influx/efflux mechanism also contributed to the increase in the resistance to ciprofloxacin in one CRV. Moreover, lipid oxidation to malondialdehyde and protein oxidation to carbonyls and advanced oxidation protein products were higher in sensitive than in the resistant strains, as a new factor involved in the mechanisms of resistance in P. mirabilis. The oxidative stress cross-resistance to telluride in CRVs enhanced the role of the antioxidants in the ciprofloxacin resistance of P. mirabilis, which was reinforced during the assays of reduction of susceptibility to ciprofloxacin by glutathione and ascorbic acid.

Macromolecular Oxidation in Planktonic Population and Biofilms of Proteus mirabilis Exposed to Ciprofloxacin

Diverse chemical and physical agents can alter cellular functions associated with the oxidative metabolism, thus stimulating the production of reactive oxygen species (ROS). Proteins and lipids may be important targets of oxidation, and this may alter their functions in planktonic bacterial physiology. However, more research is necessary to determine the precise role of cellular stress and macromolecular oxidation in biofilms. The present study was designed to evaluate whether ciprofloxacin (CIP) could oxidize the lipids to malondialdehyde (MDA) and the proteins to carbonyl residues and to advanced oxidation protein products (AOPP) in planktonic populations and biofilms of Proteus mirabilis. Incubation with CIP generated an increase of lipid and protein oxidation in planktonic cells, with a greater effect found in sensitive strains than resistant ones. Biofilms showed higher basal levels of oxidized macromolecules than planktonic bacteria, but there was no significant enhancement of MDA, carbonyl, or AOPP with antibiotic. The results described in this article show the high basal levels of MDA, carbonyls, and AOPP, with aging and loss of proliferation of biofilms cells. The low response to the oxidative stress generated by CIP in biofilms helps to clarify the resistance to antibiotics of P. mirabilis when adhered to surfaces.

Diagnóstico bacteriológico de tuberculosis renal: experiencia del Laboratorio Regional de Tuberculosis de la provincia de Córdoba

Resumen es: Dada la considerable incidencia de tuberculosis renal entre enfermos con tuberculosis pulmonar, nos propusimos estudiar la frecuencia de esta asociacion ...

In vitro oxidant effects of D-glucosamine reduce adhesión and biofilm formation of Staphylococcus epidermidis

Staphylococcus epidermidis is a common pathogen in medical device-associated infections. Its major pathogenic factor is the ability to form adherent biofilms. In this work, three S. epidermidis strains isolated from infected catheters were chosen with the objective of investigating the effect of D-glucosamine (D-Glu) on reactive oxygen species (ROS) production, adhesion and biofilm formation. The chemiluminescence and nitroblue tetrazolium reduction assays were used to determine ROS production by planktonic S. epidermidis and the microtiter plate assay to quantify in vitro biofilm formation. D-Glu generated a dose-dependent increase in ROS in planktonic cells with maximum stimuli at a concentration of 0.05 mM, and reduced adhesion and biofilm formation. On the other hand, glucose showed an antioxidative stress action and promoted biofilm adhesion and growth. This study suggests a potential application of D-Glu against infections associated with indwelling medical devices, since the oxidative stress caused by this hexosamine in planktonic S. epidermidis contributed to reducing biofilm formation.