Behaviors of Gram-Positive and Gram-Negative Bacteria after Exposure to Aerosolization Stress

BROOKE SMITH, Maria King, Texas A&M University

     Abstract Number: 223
     Working Group: Bioaerosols

Abstract
This study aimed to investigate the behavior of Bacillus globigii, a simulant for the gram-positive pathogen Bacillus anthracis, in response to environmental conditions during aerosolization. This study was conducted to build upon previous work by the authors which showed that aerosolization triggered antibiotic resistance in Escherichia coli (E. coli) MG1655, a gram-negative pathogen simulant. B. globigii spore suspensions were aerosolized at different environmental conditions for 5 different time durations into a sterile, air-tight chamber and collected using a wetted-wall cyclone bioaerosol collector (WWC). Each sample was analyzed based on its response to each environmental factor using antibiotic susceptibility testing and polymerase chain reaction (PCR). In comparison to E. coli the B. globigii behaved similarly with a decrease in development of resistance during 10-minute testing versus shorter and longer durations. These results were also consistent with culturability, showing that the environmental conditions during 10 minutes of aerosolization could be optimal for gram-positive and gram-negative bacteria to decrease the amount of resistance. The B. globigii showed a 28% increase in resistance for samples aerosolized for shorter and longer times compared to the optimal time of 10-minute aerosolization. B. globigii showed resistance mostly to cell wall synthesis inhibitors ampicillin, cephalothin and imipenem which increased nearly 100% after aerosolization. This is an important study to delineate and compare the response of gram-positive and gram-negative bacteria to aerosolization stress and determine which mechanisms are deployed by antibiotic resistant bacteria.