The last decades witnessed the emergence of several new mycobacterial species provoking severe infections, one of these ?New? mycobacterial pathogen species is: Mycobacterium abscessus has the notoriety of being the most chemotherapy resistant species within rapid growing mycobacteria (RGM), the first part of the work presented in this book is related to the mechanism of resistance of M. abscessus to one class of antibiotics ?the aminoglycoside antibiotics? whereas the second part, deal with the role of one component of the mycobacterial cell envelope namely ?the glycopeptidolipids? in conferring M. abscessus virulence. The work presented here will certainly help to a better understanding of the drugs resistance as well as M. abscessus virulence at cellular level, which will help towards the development of a better diagnosis strategies and potential drugs design.