Role of double strand DNA break repair for quinolone sensitivity in Escherichia coli: therapeutic implications

Quinolones are one of the types of antibiotics with higher resistance rates in the last years. At molecular level, quinolones block type II topoisomerases producing double strand breaks (DSBs). These DSBs could play a double role, as inductors of the quinolone bactericidal effects but also as mediators of the resistance and tolerance mechanisms. In this work we have studied the molecular pathways responsible for DSBs repair in the quinolone susceptibility: the stalled replication fork reversal (recombination-dependent) (RFR), the SOS response induction, the translesional DNA synthesis (TLS) and the nucleotide excision repair mechanisms (NER). For this reason, at the European University in Madrid, we analysed the minimal inhibitory concentration (MIC) to three different quinolones in Escherichia coli mutant strains coming from different type culture collections. recA, recBC, priA and lexA mutants showed a significant reduction on the MIC values for all quinolones tested. No significant changes were observed on mutant strains for TLS and NER. These data indicate that in the presence of quinolones, RFR mechanisms and the SOS response could be involved in the quinolone susceptibility.