Oral Presentation Australian Society for Microbiology Annual Scientific Meeting 2019

Comparison of the role of extracellular vesicles (EVs) from methicillin-resistant Staphylococcus aureus (MRSA) isolated from ampicillin stressed and unstressed state on β-lactam antibiotics (#163)

Tae Sung Jung 1 2 , Si Won Kim 1 , Se Pyung Im 1 , Jung Suk Lee 1 , Jae Wook Jung 1 , Jin Honf Chun 1 , Wei Zhang 2 , Chris Franco 2
  1. Lab. of aquatic animal diseases, College of Veterinayr Medicine, Gyeongsang National University, Jinju, Gyeongnam, S. Korea
  2. Centre for Marine Bioproducts Development (CMBD), College of Medicine and Public Health, FLINDERS UNIVERSITY, Adelaide, SA, Australia

EVs produced by Gram-positive bacteria contain several bacterial compounds and play important roles in interbacterial communication to cope with the antibiotic condition. Roles of EVs isolated from MRSA grown on ampicillin stressed condition and normal condition on several β-lactam antibiotics were compared. The EVs of methicillin-resistant Staphylococcus aureus (MRSA) ST692 were isolated in an environment with no stressed and with stressed by adding ampicillin at a lower concentration than minimum inhibitory concentration (MIC). The isolated EVs were incubated with sensitive S. aureus in the presence of several β-lactam antibiotics. The several β-lactam antibiotics treated with EVs from the stressed condition and normal condition was measured with LC-QQQ. Each of EVs was analyzed using LC-ESI-MS/MS to compare their respective protein compositions.

 

The level of EVs production from MRSA under stressed conditions was increased to about 8.8 fold compared with that of EVs under unstressed condition. The growth kinetics and CFU counting results revealed that EVs from MRSA under stressed condition could protect susceptible S. aureus in the presence of several β-lactam antibiotics (ampicillin, cefoperazone, cefazolin, amoxicillin, cephalexin, and cloxacillin) better than EVs from MRSA under unstressed conditions. The result of LC-QQQ showed that several β-lactam antibiotics can be degraded by EVs. In protein analysis, several proteins related to β-lactam antibiotics were found in EVs. Especially, EVs isolated from stressed condition showed 5.4 times more β-lactamase than EVs isolated under normal condition.

 

In this study, the presence of ampicillin could increase the production of EVs from MRSA. The EVs from MRSA under stressed conditions have a potent ability in protecting susceptible S. aureus in the presence of β-lactam antibiotics compared with unstressed conditions. The difference in these roles seems to be due to different protein compositions of EVs. Our observation can serve as a caution on the abuse of β-lactam antibiotics in real life because this could lead to escalating antibiotics resistance, which is currently becoming a serious social problem.