Eighteen isolates of Chlamydia pneumoniae from ill children with bronchitis and/or pneumonia and their families were tested in terms of susceptibility to antimicrobial agents. (These strains were isolated from May 1992 to December 1995.) The antibiotics used were doxycline (DOXY), erythromycin (EM), rokitamycin (RKM), azithromycin (AZM), clarithromycin (CAM), roxithromycin (RXM) and ofloxacin (OFLX). The MIC ranges of these antibiotics against the isolates were 0.03-0.125 μg/ml except OFLX (0.5-2.5 μg/ml), and the MICs were similar to those for C. pneumoniae11. W 183 and C. trachomatis serovar L2. The minimal chlamydiacidal concentration was also determined by using 10 isolates for which the concentration was about 10 times higher than the MIC. No difference was found among the isolates from the same patients.

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We determined the effects of the inoculum size of cefcapene (CFPN), a new oral cephalosporin, on its antibacterial and bactericidal activities against Haemophilus influenzae by simulation of human serum concentrations. The resulst were as follows. First, we compared the antibacterial activity of CFPN against H. influenzae with those of cefpodoxime, cefteram (CFTM), cefaclor and cefotiam. CFPN showed good activity, second to that of CFTM, at an inoculum size of 10⁶CFU/ml. But for an inoculum of 10⁸CFU/ml, the end-points of bacterial activity on high-dose plates of all experimental oral cephalosporines were difficult to judge. In the replica-plating method, the antibacterial activity of CFPN was close to the MICs for an inoculum of 10⁶CFU/ml. We next counted the viable cells on plates containing CFPN with an inoculum of 10⁸CFU/ml. On plates of over MIC with an inoculum of 10⁶CFU/ml, there were clearly fewer colonies than just after inoculation. Thus, CFPN showed an antibacterial effect against H. influenzae. We finally determined the bactericidal activity of CFPN against inocula of 10⁵CFU/ml and 10⁷CFU/ml of 4 H. influenzae strains (including β-lactamase-producing strain) by simulation of human serum concentrations after oral administration of 100mg of the drug 3 times/day. CFPN showed good bactericidal activity against H. influenzae. The viable cell number remained below detection levels for 10 hours after CFPN administration with 10⁵CFU/ml and 18 hours with 10⁷CFU/ml against all H. influenzae strains. We concluded that CFPN can be a highly useful antibiotic against H. influenzae infections.

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The sensitivity rate to cefpirome was surveyed, by the one-concentration, the three-concentration or the KB method, on various of 16, 861 strains belonging to various bacterial species. These strains were isolated at 51 hospitals all over Japan during the period from April, 1996 to March, 1997. Escherichia coli, methicillin-susceptible Staphylococcus aureus (MSSA) and Haemophilus influenzae were isolated in order from outpatients, whereas Pseudomonas aeruginosa, methicillin-resistant S. aureus (MRSA), and E. coli, were isolated in order from inpatients. Isolation frequencies of MRSA among all strains of S. aureus were 30.0% and 75.9% in outpatients and inpatients, respectively. Sensitivity rates to cefpirome were higher than 90% in MSSA, Streptococcus pneumoniae, Streptococcus pyogenes, Streptococcus agalactiae, Nisseria gonorrhoeae, H. influenzae, Moraxella subgenus Branhamella catarrhalis, E. coli, Klebsiella pneumoniae, Klebsiella oxytoca, Proteus mirabilis, Proteus vulgaris, Morganella morganii, Providencia rettgeri, Enterobacter aerogenes, Enterobacter cloacae, Serratia marcescens and Peptostreptcoccus spp. by all three methods. Sensitivity rates of cefpirome against P. aeruginosa were 72% by the one-concentration and the three-concentration method and 71% by the KB method. Sensitivity rates to cefpirome were lower than 50% in MRSA, E. faecium, X. maltophilia and A. xylosoxidans.

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Four subclasses of human IgG exhibit unique profiles and specific spectra against microbial antigens. Antibody titers of human intravenous immunoglobulin preparation (IVIG) including IgG subclasses against 18 clinical isolates of Streptococcus pneumoniae and pneumococcal polysaccharides were determined by enzyme-immunoassay. IgG2 was predominantly reactive against each antigen in comparison with IgGl, IgG3 and IgG4. Since S. pneumoniae SP-23 was an especially representative strain that is most reactive to IgG2, the opsonic activity of IgG2 was studied by using this strain. Binding of IgG2 to human neutrophils was recognized after incubation with FITC conjugated monoclonal anti-human IgG2 by flow cytometry. This binding was inhibited by the addition of anti-Fc γ RIII monoclonal antibody. Column chromatography using spherical adsorbent of magnesium pyrophosphate resulted in preparation of an IgG2-deficient fraction (IgG2-D) and an approximately 4-fold decrease in IgG2 from native IVIG. Opsonic activities of the two immunoglobulin preparations were subsequently compared after incubation with S. pneumoniae SP-23 and human neutrophils at 37°C. Ingested bacteria in neutrophils were counted by microscopy. IgG2-D showed lower opsonic activity against S. pneumoniae than IVIG at the same IgG concentrations of 0.17 and 0.33 mg/ml. Each of the two immunoglobulin fractions was incubated with S. pneumoniae SP-23 at 37°C for 1 h and inoculated into ICR mice intravenously. Viable bacteria were counted 20 minutes after infection. IgG2-D showed less activity against bacterial clearance in mice than WIG at the same concentrations. It is suggested that phagocytosis and subsequent intracellular killing of bacteria require the binding of IgG2 to S. pneumoniae, namely opsonization.

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