In order to get inside the cell, these molecules must pass through porins, which are protein channels that span the outer membrane. Antimicrobial resistance mechanisms in Pseudomonas aeruginosa Gram-negative bacteria possess proteins called porins in their outer membranes that, when altered, reduce or halt drug absorption.
The Code of Federal Regulations (CFR) is a codification (arrangement of) the general and permanent rules published in the Federal Register by the executive departments and agencies of the Federal Government. e-CFR Updated Daily; Beta Site.
In an effort to standardize safety, it is likely that stricter regulation of e-cigarettes is coming. A crackdown will force many e-cigarette companies out of business as they lack the resources to abide by new rules, leaving the market to big tobacco.