Initial bactericidal activity was defined as log10 of bacteria killed in 1 hour of exposure to antibiotics. Initial bactericidal activity of carbapenems depended on substrate concentration, whereas the intitial bactericidal activity of ceftazidime (a cephem antibiotics) did not depend on concentration within tested concentrations (0.5 μ M to 80 μ M) Initial bactericidal activity of 4 carbapenems (imipenem, meropenem, panipenem, and biapenem) and 3 cephem antibiotics (ceftazidime, cefepime, and cefpirome) against Pseudomonas aeruginosa PAO1 was measured at 20μ M of each antibiotic. Carbapenems other than meropenem showed above 2 log reduction in viable count in 1 hour, but cephem antibiotics and meropenem showed under 0.5log reduction in viable counts in 1 hour. Imipenem showed exceptional initial bactericidal activity. Initial bactericidal activity of carbapenem and cephem antibiotics was assessed using 47 strains of P. aeruginosa clinical isolates. The rate of P. aeruginosa clinical isolates showing ≥2log10 reduction in viable counts per hour was 68.0% for imipenem, for panipenem, 36.2% for biapenem, 31.9% for meropenem, 23.4% for cefepime, 19.1% for cefpirome, and 0% for ceftazidime. The geometric MIC mean for 47 strains of P. aeruginosa was 0.612μg/mL for meropenem, 1.02μg/mL. for biapenem, 1.67 μg/mL for imipenem, 3.61μg/mL for cefepime, 4.12μg/mL for ceftazidinie, and 5.87 μg/mL for panipenem. Initial bactericidal activity did not correlate with MIC. This study thus requires further study of the relationship between initial bactericidal activity and clinical efficacy.

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We compared the sensitivity of methicillin-resistant Staphylococcus aureus (MRSA) to drugs such as arbekacin (ASK), vancomycin (VCM) and teicoplanin (TEIC) in β-lactam antibiotic-induced VCM-resistant MRSA (BIVR) and non-BIVR strains. MRSA clinical isolates (121 strains) were classified into 16 strains of BIVR and 105 strains of non-BIVR due to the existence of antagonism between ceftizoxime (CZX) and VCM in an Mu3 medium. There was a slight difference between the susceptibility of BIVR and non-BIVR to ABK. The antibacterial activity of ABK was also not affected in combination with low-concentrations of CZX (0.06 or 1μg/mL). On the other hand, the minimum inhibitory concentrations, MIC₅₀, and MIC₉₀, of VCM against BIVR strains were both twice higher than against non-BIVR strains, and were also 4 times higher thanagainst non-BIVR strains in cornbination with CZX. Although the antibacterial activity of TEIC against BIVR strains did not change in the presence of CZX, the MTC₅₀ and MIC₉₀ of TEIC alone were 8 and 4 times higher thanagainst non-BIVR strains, respectively. Next, the relationship between the MIC of TEIC and detection frequency of BIVR strains was investigated. As a result, the higher the MIC of TEIC, the more frequently BIVR strains were found. Furthermore, BIVR strains were isolated from non-BIVR sub-populations with diminished susceptibility to TEIC.
In conclusion, the antibacterial activity of ABK was not changed by the difference between BIVR and non-BIVR strains. On the other hand, VCM showed antagonistic effects in combination with CZX at low concentrations against BIVR strains. TEIC alone was less effective against BIVR strains, although TEIC did not reveal any antagonistic effect against BIVR strains in combination with CZX.

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According to the “Japanese Respiratory Society guidelines for the management of community-acquired pneumonia in adults”(hereinafter referred to as “the community-acquired pneumonia guidelines”), fluoroquinolones, such as tosufloxacin tosilate (TFLX) and sparfloxacin (SPFX), are recommended when Streptococcus pneumoniae (S. pneumoniae) is detected. Few clinical studies have been performed, however, of the efficacy and other characteristics of these antimicrobials.
This study examined the efficacy of the fluoroquinolone TFLX against S. pueumoniac-related pneumonia with reference to the community-acquired pneumonia guidelines.
This study included pneumonia patients where the presence of S. pneumoniae was suspected by smear staining (smear staining-positive patients) and, of these positive patients, where S. pneumoniae was actually detected (S. pneumoniae-detected patients). There was no difference in background characteristics between 68 smear staining-positive patients and 36 S. pneumoniae-detected patients. The efficacy rate was 92.6%(25/27 patients) at a daily dose of 450mg (450-mg group) and 100%(35/35 patients) at 600mg (600-mg group) in the smear staining-positive patients. The two non-responders at 450mg had moderate pneumonia. In S. pneurnoniae-detected patients, the efficacy rate was 93.6%(15/16 patients) in the 450-mg group and 100%(16, 16 patients) in the 600-mg group. S. pneumoniae disappeared in 94.1%(16/17 patients) in the 450-mg group and 93.8%(15/16 patients) in the 600-mg group. Against S. pneumoniae isolated in this study, MIC₉₀ of TFLX was 0.25μg/mL. Based on the daily AUC from TFLX concentration in blood from healthy adults, the AUC/MIC ratio was 46.4 in the 450-mg dose and 62.0 in the 600-mg dose.
TFLX was effective against S. pneumoniae-related pneumonia in terms of basic aspects of clinical, antimicrobial and pharmacokinetic properties, showing that TFLX is a respiratory quinolone.
In patients with S. pneumoniae-related pneumonia, TFLX should be administered to patients with mild and moderate pneumonia at a daily dose of 450 or 600mg. The higher dose of 600mg is probably preferable in moderate cases with more potent inflammatory responses according to clinical symptoms and laboratory findings.

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The in vitro virucidal efficacy of povidone-iodine products against avian influenza viruses was investigated. The viral infectious titers were reduced below the detection limit by incubation with the povidone-iodine products used in this study (PVP-I solution, PVP-I scrub, PVP-I palm, PVP-I gargle, PVP-I throat spray and PVP-I solution for animals) for only 10 seconds. These results indicate the virucidal efficacy of these povidone-iodine products against avian influenza viruses.

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