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Published on: July 25, 2017
Bacitracin-resistant Staphylococcus aureus induced in chicken gut and in vitro under bacitracin exposure
Fan Zhang1, Fangjia Liu1, Xijing Sheng1
1The Cooperative Innovation Center for Sustainable Pig Production, Huazhong Agricultural University, Wuhan, 430070, China; MOA Key Laboratory of Food Safety Evaluation/National Reference Laboratory of Veterinary Drug Residue (HZAU), Huazhong Agricultural University, Wuhan, 430070, China.
Abstract:
It is common knowledge that prolonged and excessive use of antibiotics can lead to antimicrobial resistance. However, the characteristics and mechanism of resistant-bacteria induced by clinically recommended and prophylactic dose drugs remain largely unclear. This study aimed to observe the trends of drug resistance of the bacitracin-susceptible Staphylococcus aureus strain FS127 under exposure to bacitracin (BAC), which were induced in vitro and in chicken gut. Antimicrobial susceptibility testing was used to detect the susceptibility of S. aureus induced in vitro and in the chicken gut to gentamicin, chloramphenicol, tetracycline, doxycycline, penicillin and chloramphenicol. The research results showed that bacitracin could induce drug resistance in S. aureus both in vitro and in vivo. The bacitracin-resistance rate of S. aureus isolated from chicken gut was positively correlated with the dose and time of bacitracin administration. The findings revealed that bacitracin-resistant S. aureus induced in vivo had enhanced susceptibility to chloramphenicol but no such change in vitro. Meanwhile, RT-qPCR assay was used to detect the expression levels of vraD, braD, braR and bacA in typical strains with different bacitracin-resistance levels. It was found that BacA may play a key role in the bacitracin resistance of S. aureus. In conclusion, this work reveals the characteristics and mechanism of bacitracin-resistant S. aureus induced by bacitracin in vivo and in vitro respectively.
Insights
Bacitracin (BAC) exposure can induce drug resistance in Staphylococcus aureus, both in lab settings and within chicken guts. This resistance correlates with BAC dose and duration, with potential implications for antibiotic efficacy.
Area of Science:
- Microbiology
- Antimicrobial Resistance
- Bacterial Genetics
Background:
- Antibiotic overuse is a known driver of antimicrobial resistance.
- Mechanisms of resistance induced by clinically relevant antibiotic doses are not well understood.
Purpose of the Study:
- To investigate the development of bacitracin resistance in Staphylococcus aureus.
- To elucidate the characteristics and mechanisms of bacitracin-induced resistance in vitro and in vivo.
Main Methods:
- Induction of bacitracin resistance in Staphylococcus aureus (S. aureus) in vitro and in chicken gut models.
- Antimicrobial susceptibility testing against multiple antibiotics.
- RT-qPCR to analyze gene expression (vráD, braD, braR, bacA).
Main Results:
- Bacitracin (BAC) successfully induced resistance in S. aureus both in vitro and in vivo.
- In vivo resistance rates correlated positively with BAC dose and administration time.
- In vivo-induced resistant strains showed increased susceptibility to chloramphenicol, unlike in vitro strains.
- BacA gene expression was identified as potentially crucial for bacitracin resistance.
Conclusions:
- Bacitracin administration can lead to the emergence of resistant Staphylococcus aureus strains.
- In vivo resistance development exhibits distinct characteristics compared to in vitro induction.
- The BacA protein is implicated as a key factor in bacitracin resistance mechanisms.
