DQ-113 is a new quinolone with potent activity against gram-positive pathogens. The in vivo activity of DQ-113 against Streptococcus pneumoniae was compared with those of gatifloxacin and ciprofloxacin in a mouse model. For this purpose, two strains of S. pneumoniae were used: penicillin-susceptible S. pneumoniae (PSSP) and penicillin-resistant S. pneumoniae (PRSP). The survival rates of mice infected with PSSP and PRSP at 14 days after infection were 80% in the DQ-113-treated group and 0 to 10% in the other three groups. In murine infections caused by PSSP, the 50% effective doses (ED 50 s) of DQ-113, gatifloxacin, and ciprofloxacin were 6.0, 41.3, and 131.6 mg/kg, respectively. Against PRSP-caused pneumonia in mice, the ED 50 s of DQ-113, gatifloxacin, and ciprofloxacin were 7.6, 64.7, and 125.9 mg/kg, respectively. Compared with the other drugs, DQ-113 showed excellent therapeutic efficacy and eradicated viable bacteria in both PSSP-and PRSP-infected mice. The means ؎ standard errors of the means of viable bacterium counts in the lungs of gatifloxacin-treated, ciprofloxacin-treated, and untreated control mice infected with PSSP were 2.91 ؎ 0.34, 3.13 ؎ 0.48, and 3.86 ؎ 0.80 log 10 CFU/ml, respectively. The same counts in mice infected with PRSP treated with the same three agents were 6.57 ؎ 0.99, 6.54 ؎ 0.40, and 7.17 ؎ 0.43 log 10 CFU/ml, respectively. DQ-113 significantly decreased the number of viable bacteria in the lungs compared with gatifloxacin and ciprofloxacin. Of the drugs analyzed, the pharmacokinetic-pharmacodynamic parameter of area under the concentration-time curve (AUC)/MIC ratio for DQ-113 was significantly higher than those for gatifloxacin and ciprofloxacin. Our results suggest that DQ-113 has potent in vivo efficacy against both PSSP and PRSP.

Background S. pneumoniae is the leading cause of morbidity and mortality worldwide. -lactam antibiotics were very effective against S. pneumoniae, however resistance to this class of antibiotic has become an increasing problem.Objectives To assess the clinical differences between penicillin-sensitive and penicillin-resistant pneumococcal pneumonia.Methods The medical records of 306 patients with pneumococcal pneumonia who visited Nagasaki University Hospital or affiliated institutions between January 1997 and December 2001 were retrospectively reviewed. The Pneumonia Severity Index (PSI), sensitivity of S. pneumoniae, antibiotic choices and information on clinical outcome were evaluated.Results Penicillin sensitive and resistant organisms were responsible for 177 (57.7%) and 129 (42.0%) cases of pneumonia, respectively. The median age of patients was 65.5 years, and 72.3% (222) were males. There were no significant differences in the resistance rate between elderly (>65 years) and young patients. The median PSI score was 76. No significant association was observed between the severity of illness and sensitivities of S. pneumoniae. Previous use of beta-lactams in the last 3 months and chronic obstructive pulmonary disease were associated with penicillin resistance. The failure rate of first line antibiotics was significantly higher in the resistant group (22.5%) than in the sensitive group (9.0%). Four of 306 patients died (mortality, 1.3%).Conclusion There were no significant differences clinically between the penicillin-sensitive and penicillinresistant groups. The failure rate of first line antibiotics was higher in the resistant than in the sensitive group. Thus, the selection of antimicrobial agents should be carefully considered in the context of the patient's risk factors.

We have reported two orthopedic patients with Methicillin-resistant Staphylococcus aureus (MRSA) infections successfully treated with linezolid. The first case was a 64-years-old man with bacteremia, spondylitis and psoas abscesses caused by MRSA. He was treated with arbekacin (ABK) and vancomycin (VCM), and then became afebrile. However he complained of a recurrence of fever and oliguria, we administered linezolid for two weeks intravenously because of fluctuating renal dysfunction. Thereafter his clinical conditions improved. The second case was a 26-years-old man with MRSA infection of the pelvis after a trauma. He was treated with teicoplanin (TEIC) for two weeks. However the minimum inhibiratory concentrations (MICs) of TEIC and VCM against MRSA, isolated from the wounds, were 4 micrograms/ml each, we administered linezolid intravenously and the patient was successfully treated in four weeks. Linezolid has been proven to have high efficacy against MRSA by some trials abroad. But the agent has the indication only for VRE by the Medical Insurance in Japan. These cases also suggest that linezolid is useful for MRSA infections in these cases.

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