Tetracycline activation cascade of <i>E. coli</i> resistance physiological adaptation.

<p>Broken arrows indicate the activation in 1 and 2 over-expression of specific gene (direct TET pressure effect), in 3, the regulation by induced regulators (second level of control), in 4 the effect of activated genes coding for membrane proteins (third level of effect). Thick arrows (5) illustrate the effect of over-production of OMPs and proteases.</p

Relative expression of outer membrane proteins, regulators and inner membrane transporter genes.

<p>Data from three independent total mRNA extractions of <i>E. coli</i> AG100 physiologically adapted to increasing concentrations of TET compared to its parental non-induced strain grown in the absence of TET as described in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0000365#s3" target="_blank">Materials and Methods</a>. A ratio of 1 corresponds to no alterations in expression compared with untreated control cells. Values were corrected for standard deviation range.</p

Relative quantification of the expression level of the protease genes.

<p>Data from three independent total mRNA extractions of <i>E. coli</i> AG100 physiologically adapted to increasing concentrations of TET compared to its parental non-induced strain grown in absence of TET as described in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0000365#s3" target="_blank">Materials and Methods</a>. A ratio of 1 corresponds to no alterations in expression compared with untreated control cells. Values were corrected for standard deviation range.</p

Primers used in this study.

<p>Primers used in this study.</p

Immunodetection of the outer membrane proteins.

<p>The detections were carried out using antisera prepared against OmpC porin (A), OmpF porin (B), antigenic peptide located inside the internal loop 3 porin (C), OmpA (D) and OmpX (E) respectively. Immunodetection were carried out with total cell extracts from non-induced AG100 (1, 2) and 10 mg/mL TET-induced (3, 4) strains grown in LB and MH media (odd and even lanes respectively).</p

Antibiotic Uptake through Membrane Channels: Role of <i>Providencia stuartii</i> OmpPst1 Porin in Carbapenem Resistance

The role of major porin OmpPst1 of <i>Providencia stuartii</i> in antibiotic susceptibility for two carbapenems is investigated by combining high-resolution conductance measurements, liposome swelling, and microbiological assays. Reconstitution of a single OmpPst1 into a planar lipid bilayer and measuring the ion current, in the presence of imipenem, revealed a concentration-dependent decrease in conductance, whereas meropenem produced well-resolved short ion current blockages. Liposome swelling assays suggested a small flux of imipenem in contrast to a rapid permeation of meropenem. The lower antibiotic susceptibility of <i>P. stuartii</i> to imipenem compared to meropenem correlated well with the decreased level of permeation of the former through the OmpPst1 channel