Antimicrobial resistance in mollicutes: known and newly emerging mechanisms

: This review is devoted to the mechanisms of antibiotic resistance in mollicutes (class Bacilli, subclass Mollicutes), the smallest self-replicating bacteria, that can cause diseases in plants, animals and humans, and also contaminate cell cultures and vaccine preparations. Research in this area has been mainly based on the ubiquitous mollicute and the main contaminant of cell cultures, Acholeplasma laidlawii. The omics technologies applied to this and other bacteria have yielded a complex picture of responses to antimicrobials, including their removal from the cell, the acquisition of antibiotic resistance genes and mutations that potentially allow global reprogramming of many cellular processes. This review provides a brief summary of well-known resistance mechanisms that have been demonstrated in several mollicutes species and, in more detail, novel mechanisms revealed in A. laidlawii, including the least explored vesicle-mediated transfer of short RNAs with a regulatory potency. We hope that this review highlights new avenues for further studies on antimicrobial resistance in these bacteria for both a basic science and an application perspective of infection control and management in clinical and research/production settings.