Sang Hyub Lee

Despite the need for new antibiotics to treat drug-resistant bacteria, current clinical combinations are largely restricted to β-lactam antibiotics paired with β-lactamase inhibitors. We have adapted a Staphylococcus aureus antisense knockdown strategy to genetically identify the cell division Z ring components-FtsA, FtsZ, and FtsW-as β-lactam susceptibility determinants of methicillin-resistant S. aureus (MRSA). We demonstrate that the FtsZ-specific inhibitor PC190723 acts synergistically with β-lactam antibiotics in vitro and in vivo and that this combination is efficacious in a murine model of MRSA infection. Fluorescence microscopy localization studies reveal that synergy between these agents is likely to be elicited by the concomitant delocalization of their cognate drug targets (FtsZ and PBP2) in MRSA treated with PC190723. A 2.0 Å crystal structure of S. aureus FtsZ in complex with PC190723 identifies the compound binding site, which corresponds to the predominant location of mutations conferring resistance to PC190723 (PC190723(R)). Although structural studies suggested that these drug resistance mutations may be difficult to combat through chemical modification of PC190723, combining PC190723 with the β-lactam antibiotic imipenem markedly reduced the spontaneous frequency of PC190723(R) mutants. Multiple MRSA PC190723(R) FtsZ mutants also displayed attenuated virulence and restored susceptibility to β-lactam antibiotics in vitro and in a mouse model of imipenem efficacy. Collectively, these data support a target-based approach to rationally develop synergistic combination agents that mitigate drug resistance and effectively treat MRSA infections.

BACKGROUND AND AIM: The aim of this study was to determine the accuracy of endoscopic ultrasonography (EUS) and multidetector-row computed tomography (MDCT) for the locoregional staging of gastric cancer. EUS and computed tomography (CT) are valuable tools for the preoperative evaluation of gastric cancer. With the introduction of new therapeutic options and the recent improvements in CT technology, further evaluation of the diagnostic accuracy of EUS and MDCT is needed. METHODS: In total, 277 patients who underwent EUS and MDCT, followed by gastrectomy or endoscopic resection at Bundang Hospital, Seoul National University, from July 2006 to April 2008, were analyzed. The results from the preoperative EUS and MDCT were compared to the postoperative pathological findings. RESULTS: Among the 277 patients, the overall accuracy of EUS and MDCT for T staging was 74.7% and 76.9%, respectively. Among the 141 patients with visualized primary lesions on MDCT, the overall accuracy of EUS and MDCT for T staging was 61.7% and 63.8%, respectively. The overall accuracy for N staging was 66% and 62.8%, respectively. The performance of EUS and MDCT for large lesions and lesions at the cardia and angle had significantly lower accuracy than that of other groups. For EUS, the early gastric cancer lesions with ulcerative changes had significantly lower accuracy than those without ulcerative changes. CONCLUSIONS: For the preoperative assessment of individual T and N staging in patients with gastric cancer, the accuracy of MDCT was close to that of EUS. Both EUS and MDCT are useful complementary modalities for the locoregional staging of gastric cancer.