Upregulation of the clpB gene in response to heat shock and beta-lactam antibiotics in Acinetobacter baumannii
The role of the clpB gene encoding HSP/chaperone ClpB was evaluated in the multiresistant antibiotic cells of Acinetobacter baumannii (RS4 strain) under stress-induced heat shock and different beta-lactams. The expression of the clpB gene was assessed by qPCR during heat shock at 45 °C and subinhibitory concentrations of ampicillin (30 μg mL−1), amoxicillin + sulbactam (8/12 μg mL−1), cefepime (30 μg mL−1), sulfamethoxazole + trimethoprim (120/8 μg mL−1) and meropenem (18 μg mL−1). The results indicated a transient increase in clpB transcription in all treatments except cefepime. Both in the presence of ampicillin and amoxicillin/sulbactam for 20 min, the mRNA-clpB synthesis was 1.4 times higher than that of the control at time zero. Surprisingly, the mRNA-clpB levels were more than 30-fold higher after 10 min of incubation with meropenem and more than eightfold higher in the presence of trimethoprim/sulfamethoxazole. In addition, western blot assays showed that the RS4 strain treated with meropenem showed a marked increase in ClpB protein expression. Our data indicate that during exposure to beta-lactams, A. baumannii adjusts the transcription levels of the clpB mRNA and protein to respond to stress, suggesting that the chaperone may act as a key cellular component in the presence of antibiotics in this bacterium.
KeywordsClpB Stress response Antibiotics Heat shock proteins Multidrug resistance
W. Y. Lazaretti is a professional funded by the Brazilian National Health Surveillance Agency (ANVISA). E. L. Santos was a fellow of the Brazilian National Council for Scientific and Technological Development (CNPq).
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Conflict of interest
All the authors declared that they have no conflict of interest.
The authors declare that the research was performed in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.
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