Sub-inhibitory doses of antibiotics have been shown to cause changes in bacterial cell morphology, biofilm formation, and resistance to antibiotics. In this study, the effects of sub-inhibitory doses of aminoglycoside antibiotics on M. abscessus were investigated. Treatment of M. abscessus cells with sub-inhibitory doses of amikacin was found to change their colony morphology from a smooth to a rough morphotype and increase their ability to form biofilms, aggregate in culture, and resist phagocytosis and killing by macrophages. M. abscessus cells treated with a sub-inhibitory dose of amikacin also became more potent in TLR-2 stimulation, leading to increased TNF-a production by macrophages and severity of lung inflammation. The mab_3508c gene was shown to play a major role in mediating these phenotypic changes as its expression in M. abscessus cells was increased when they were treated with a sub-inhibitory dose of amikacin. In addition, over expression of mab_3508c in M. abscessus cells caused changes similar to those induced by sub-inhibitory doses of amikacin, including smooth to rough switching in colony morphology, increased ability to aggregate in liquid culture, decreased motility, and increased resistance to killing by macrophages.