4).

Likewise, the msbA transcript was not affected in the imp/ostA deletion mutant in comparison with the wild-type strain after glutaraldehyde treatment. This result indicated that imp/ostA and msbA were induced by glutaraldehyde through independent pathways. Figure 4 The effect of imp/ostA on the transcription of msbA after glutaraldehyde treatment and vice versa. Slot blots analysis of total RNA preparations of H. pylori NTUH-S1 wild-type and mutants after 0.5 μg/ml glutaraldehyde treatment for 48 h. Each well was loaded with 10 μg total bacterial RNA. The membrane was hybridized with DIG-labeled probes specific for H. pylori imp/ostA, msbA, and 23S rRNA. The MICs of glutaraldehyde in isogenic mutants We had previously observed that the imp/ostA mutant became more sensitive to glutaraldehyde than wild-type strain [14]. Southern blot hybridizations were performed to confirm that imp/ostA or msbA were absent in the see more mutants (Fig. 5). We further investigated whether the sensitivities to glutaraldehyde ofisogenic msbA and an imp/ostA, msbA double mutants were altered. The

MIC for the msbA single mutant (3.05 ± 0.27 μg/ml) was lower than for wild-type (5.45 ± 0.21 Sotrastaurin mw μg/ml) (wild-type vs.msbA single mutant, P = 2.84 × 10-7). For comparison, the MIC for the imp/ostA single mutant (1.40 ± 0.42 μg/ml) was also significantly lower than that of wild-type, as previously reported [14]. Furthermore, the MICs for imp/ostA and msbA double mutant (0.60 ± 0.14 μg/ml) was also significantly

lower than that of wild-type and showed the most significant difference (P = 5.77 × 10-10). Ruxolitinib mw Complementation of the msbA mutation significantly restored the resistance to glutaraldehyde (Fig. 6A). These results suggested that imp/ostA and msbA were both involved in glutaraldehyde resistance, and the deficiency of these two genes in H. pylori led to hypersensitivity to glutaraldehyde. Figure 5 Southern hybridization of Hind III-digested DNA from strains NTUH-S1 and mutants with imp/ostA (left) and msbA (right) probes. Approximately 5 μg of genomic DNA from O-methylated flavonoid H. pylori NTUH-S1 and the mutants was digested by Hind III. Hybridization and detection were performed with the DIG Luminescent Detection kit (Roche) according to the manufacturer’s instructions. The MICs of hydrophobic antibiotics in isogenic mutants According to previous reports [41, 45], MsbA interacts with multiple drugs, for example, multidrug resistance (MDR) substrates (doxorubicin, vinblastine, erythromycin, ethidium bromide) and non-MDR substrates (lipid A, Hoechst). In addition, MsbA increases resistance to erythromycin by 86-fold when it is expressed in L. lactis [22]. In contrast, expression of MsbA in Pseudomonas aeruginosa did not confer resistance to erythromycin, but introducing E. coli msbA into P. aeruginosa decreased the susceptibility of this bacterium to erythromycin by 4-fold [46].