The role of RND-type efflux pumps in multidrug-resistant mutants of Klebsiella pneumoniae

The emergence of multidrug-resistant Klebsiella pneumoniae is a worldwide problem. K. pneumoniae possesses numerous resistant genes in its genome. We isolated mutants resistant to various antimicrobials in vitro and investigated the importance of intrinsic genes in acquired resistance. The isolation frequency of the mutants was 10(-7)-10(-9). Of the multidrug-resistant mutants, hyper-multidrug-resistant mutants (EB256-1, EB256-2, Nov1-8, Nov2-2, and OX128) were identified, and accelerated efflux activity of ethidium from the inside to the outside of the cells was observed in these mutants. Therefore, we hypothesized that the multidrug efflux pump, especially RND-type efflux pump, would be related to changes of the phenotype. We cloned all RND-type multidrug efflux pumps from the K. pneumoniae genome and characterized them. KexEF and KexC were powerful multidrug efflux pumps, in addition to AcrAB, KexD, OqxAB, and EefABC, which were reported previously. It was revealed that the expression of eefA was increased in EB256-1 and EB256-2: the expression of oqxA was increased in OX128; the expression of kexF was increased in Nov2-2. It was found that a region of 1,485 bp upstream of kexF, was deleted in the genome of Nov2-2. K. pneumoniae possesses more potent RND-multidrug efflux systems than E. coli. However, we revealed that most of them did not contribute to the drug resistance of our strain at basic levels of expression. On the other hand, it was also noted that the overexpression of these pumps could lead to multidrug resistance based on exposure to antimicrobial chemicals. We conclude that these pumps may have a role to maintain the intrinsic resistance of K. pneumoniae when they are overexpressed. The antimicrobial chemicals selected many resistant mutants at the same minimum inhibitory concentration (MIC) or a concentration slightly higher than the MIC. These results support the importance of using antibiotics at appropriate concentrations at clinical sites

JCOG0911 INTEGRA study: a randomized screening phase II trial of interferonβ plus temozolomide in comparison with temozolomide alone for newly diagnosed glioblastoma

Purpose: This study explored the superiority of temozolomide (TMZ) + interferonβ (IFNβ) to standard TMZ as treatment for newly diagnosed glioblastoma (GBM) via randomized phase II screening design.Experimental design: Eligibility criteria included histologically proven GBM, with 50% of the tumor located in supratentorial areas, without involvement of the optic, olfactory nerves, and pituitary gland and without multiple lesions and dissemination. Patients in the TMZ + radiotherapy (RT) arm received RT (2.0 Gy/fr/day, 30 fr) with TMZ (75 mg/m², daily) followed by TMZ maintenance (100–200 mg/m²/day, days 1–5, every 4 weeks) for 2 years. Patients in the TMZ + IFNβ + RT arm intravenously received IFNβ (3 MU/body, alternative days during RT and day 1, every 4 weeks during maintenance period) and TMZ + RT. The primary endpoint was overall survival (OS). The planned sample size was 120 (one-sided alpha 0.2; power 0.8).Results: Between Apr 2010 and Jan 2012, 122 patients were randomized. The median OS with TMZ + RT and TMZ + IFNβ + RT was 20.3 and 24.0 months (HR 1.00, 95% CI 0.65–1.55; one-sided log rank P = 0.51). The median progression-free survival times were 10.1 and 8.5 months (HR 1.25, 95% CI 0.85–1.84). The incidence of neutropenia with the TMZ + RT and the TMZ + IFNβ + RT (grade 3–4, CTCAE version 3.0) was 12.7 versus 20.7% during concomitant period and was 3.6 versus 9.3% during maintenance period. The incidence of lymphopenia was 54.0 versus 63.8% and 34.5 versus 41.9%.Conclusions: TMZ + IFNβ + RT is not considered as a candidate for the following phase III trial, and TMZ + RT remained to be a most promising treatment. This trial was registered with the UMIN Clinical Trials Registry: UMIN000003466