The F plasmid-carried bacterial toxin, the CcdB protein, is known to act on DNA gyrase in two different ways. CcdB poisons the gyrase-DNA complex, blocking the passage of polymerases and leading to double-strand breakage of the DNA. Alternatively, in cells that overexpress CcdB, the A subunit of DNA gyrase (GyrA) has been found as an inactive complex with CcdB. We have reconstituted the inactiv...

Background The interaction between different drug-resistant mutations is important to the development of drug resistance and its evolution. In this study, we aimed to reveal the potential relationships between mutations conferring resistance to two important antituberculosis drugs streptomycin (STR) and fluoroquinolones (FLQ). Materials and methods We used an in vitro competitive fitness assa...

We isolated mutant strains of the facultative anaerobe Salmonella typhimurium that grow either aerobically or anaerobically. Strict anaerobic mutants contained a defective DNA topoisomerase I gene (topI), while strict aerobic mutants contained a defective DNA gyrase subunit A gene (gyrA, also nalA). Topoisomerase I activity was detected in cell-free extracts of strict aerobic mutants but not of...

OBJECTIVES Quinolone resistance of chlamydiae is supposed to be extremely rare. To assess the risk for the emergence of chlamydial quinolone resistance, we analysed the occurrence of resistant mutants in a quantitative perspective. METHODS Infectious elementary bodies of Chlamydia trachomatis serovar L(2) (ATCC VR-902B) and D (ATTC VR-885) clones were purified on density gradients, and mutant...

Objective(s): Regarding the global burden of uropathogenic Escherichia coli (UPEC) infections, prevention and treatment of such infections play a significant role in healthcare management. The inordinate use of fluoroquinolones led to a worldwide spread of quinolone-resistant strains. Therefore, this study aimed to investigate mutations in codons 83 and 106 of gyrA gene in UPEC isolates in the ...

BACKGROUND This study aimed to analyze the association of mutation patterns in gyrA and gyrB genes and the ofloxacin resistance levels in clinical Mycobacterium tuberculosis isolates sampled in 2009 from East China. METHODS The quinolone resistance-determining region of gyrA/B were sequenced in 192 M. tuberculosis clinical isolates and the minimal inhibitory concentrations (MICs) of 95 ofloxa...

mecA, the gene that mediates methicillin resistance, and its accompanying mec locus DNA, insert near the gyrA gene in Staphylococcus aureus. To investigate whether there is a similar relationship between mecA and gyrA in coagulase-negative staphylococci (CNS), mecA- and gyrA-specific DNA fragments were used to probe methicillin-resistant isolates of Staphylococcus epidermidis (MRSE) (n = 11) an...