Effects of sub-inhibitory concentration of antibiotic and heat stress on the expression of type II TA system genes in Brucella spp.

Objective

Bacteria can react to stress conditions using the Toxin-Antitoxin (TA) system. This study investigated the expression of TA system genes under heat and antibiotic stresses in Brucella spp.

Methods

To determine the effects of sub-inhibitory concentration (sub-MIC) of rifampin on bacterial survival and growth, a colony-forming unit was quantitated, and turbidity was assessed following the treatment of Brucella isolates, with ½ minimum inhibitory concentration (MIC) of antibiotic at different time intervals. Also, Brucella isolates were exposed to heat stress (42 °C) compared to the control (37 °C). Finally, the expression of TA system genes in Brucella isolates was evaluated one hour after treatment using the quantitative reverse transcription PCR (qRT-PCR) method.

Results

Our results showed that the growth of the Brucella isolates reduced in the presence of the sub-MIC of antibiotics compared to the control. The results of the qPCR assay showed that, in the presence of rifampicin the expression of the TA system genes increased and, under the heat stress conditions, the expression of the TA system genes increased compared to controls expect brnT / brnA system.

Conclusion

Although the exact role of the TA system in response to various stresses is not yet fully understood, our study provided information on the effectiveness of the type II TA system under heat and antibiotic stress conditions by examining the gene expression of type II systems in Brucella isolates.