Aerosolization triggers immediate antibiotic resistance in bacteria

Antibiotic resistance poses a threat in many institutions including hospitals, meat processing facilities and other agricultural and occupational entities. The goal of this research is to uncover how bacteria react to environmental conditions including aerosolization and delineate factors that trigger expression of antibiotic resistance genes (ARGs) using the laboratory strain Escherichia coli (E. coli) MG 1655 as surrogate bacterium. Fresh mid-log phase bacterial suspensions were aerosolized at different environmental conditions for 5 different time durations into a sterile chamber and collected using a bioaerosol collector. Each sample was analyzed based on its response to each environmental factor by antibiotic susceptibility testing and polymerase chain reaction (PCR) using specific primers to target ARGs. Strong resistance was detected to cell wall and protein synthesis inhibitors Cephalothin, and Gentamicin after 5 min compared to 30 min and 45 min of aerosolizations in reference to viable cell concentrations. Resistance to the highest number of antibiotics was detected in the shortest aerosolization samples while exposure for longer aerosolization durations caused an increased amount of stress which bacteria could not alleviate, indicating the involvement of different mechanisms to respond to short-term and long-term exposures. A small amount of resistance was detected after intermediate durations of aerosolization, maybe due to a transient response of the cells to compensate for mechanical, osmotic and other stresses during aerosolization. This study is the first to demonstrate that aerosolization triggers antibiotic resistance within minutes in E. coli.