Seikeikai Hospital (Director MAKOTO MINO) An outbreak of O-157: H7 diarrheal illnesses occurred in junior schools of Sakai-city, Osaka prefecture, in last July, 1996. At the beginning of the outbreak, many patients rushed to outpatient clinics. From the practical experiences, we examined the necessity of fluid therapy in patients regarding their initial clinical features. The risk factors for development of HUS were noted as presence of fever, WBC counts of more than 10,000/μl and more than 1.0mg/dl of CRP. During the prodoromal illness, administration with available antimicrobial agents would be advisable for high risk patients, while it would yet be remain to be further investigated. The majority of the patients with clinical manifestations showed neither signs for dehydration nor electrolyte abnormalities based on the blood examination data and biochemical analysis of the serum. Therefore, the fluid therapy did not appear necessary for majority of patients except a few high risk patients, when outpatient clinics were crowded with emergency patients.

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The drug susceptibility patterns were investigated for verotoxin-producing Escherichia coli (VTEC) including O-157, Salmonella spp., Vibrio parahaemolyticus and Campylobacter jejuni subsp. jejuni that were obtained in and after July 1996.
The results are summarized as follows;
1. We found highly resistant strains of VTEC to tetracycline (TC) and ampicillin (ABPC).
Minimum inhibitory concentrations (MIC) of some of the drugs against VTEC in an aerobic condition were significantly different from those in an anaerobic condition. For example, aerobic· anaerobic MIC ranges of the drugs tested were as follows: chroramphenicol (CP): 1.56-3.13μg/ ml·0.78-1.56μg/ml, TC: 1.56->100μg/ml·0.78->100μg/ml, minocycline (MINO): 1.56-12.5 μg/ml·0.78-3.13μg/ml, kanamycin (KM): 3.13-6.25μg/ml·25-100μg/ml, fosfomycin (FOM): 3.13-25μg/ml·0.78-6.25μg/ml, norfloxacin (NFLX): ≤0.025-0.2μg/ml·≤0.025-0.2μg/ml, ABPC: 1.56->100μg/ml·0.78->100μg/ml and cefaclor (CCL): 1.56-25μg/ml·1.56-12.5μg/ml. MICs of CP and tetracyclines (TCs) in an anaerobic condition were lower by twofold and the Oct. 1997 THE JAPANESE JOURNAL OF ANTIBIOTICS 50-10 843 (37) MIC of FOM was lower by fourfold, but the variabilities of MIC-ranges of NFLX, ABPC and CCL were small. The MIC of KM was high.
2. We observed that some of Salmonella spp. were highly resistant to CP, TCs and MINO, and some were moderately resistant to NFLX.
3. The detection frequency of TC-resistant strains and NFLX-insensitive or resistant strains were high among C. jejuni subsp. jejuni.
4. Strains of V. parahaemolyticus and C. jejuni subsp. jejuni were mostly resistant to ABPC and CCL, MICs of which were in high ranges.
5. Fecal concentrations in MINO, KM, FOM and NFLX reported in literatures are high enough to have some antimicrobial activities, leed dose of ABPC and CCL are quite low.

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RP 59500 (Quinupristin-Dalfopristin) is the first semisynthetic injectable streptogramin anti-microbial agent, which is a combination of quinupristin and dalfopristin in a 30: 70 ratio. The components of RP 59500 act synergically to provide bactericidal activity through action at different Oct. 1997 THE JAPANESE JOURNAL OF ANTIBIOTICS 50-10 853 (47) sites on bacterial ribosomes.
In the present study, the antimicrobial activity of RP 59500 was compared with those of four macrolides (erythromycin, clarithromycin, azithromycin, roxithromycin). Susceptibility testing was carried out by microdilution method on 303 strains of 10 species, especially antibiotic-resistant Gram-positive cocci.
RP 59500 was active against a wide range of Gram-positive cocci including methicillin-resistant Staphylococci and penicillin-resistant Streptococcus pneumoniae. The MICs90 of RP 59500 against methicillin-resistant Staphylococcus aureus (MRSA) and Staphylococcus epidermidis were both 0.25μ9/ml, although those of four macrolides were higher than 32μg/ml. The MICs90 of RP 59500 against penicillin-sensitive, -intermediate and -resistant S. pneumoniae were all 0.5μg/ml, although those of four macrolides against penicillin-resistant S. pneumoniae were higher than 32μg/ml. RP 59500 also exhibited equivalent activities to the four macrolides against strains of Streptococcus pyogenes, Streptococcus agalactiae and Moraxella catarrhalis. RP 59500 exhibited the highest activities against Enterococcus faecalis, Enterococcus faecium and Enterococcus avium strains which are intrinsically resistant to most antimicrobial agents.
No cross-resistance was observed between RP 59500 and the four macrolides, which will merit attention in future clinical trials of the agent.
The effect of human serum on the MIC of RP 59500 was studied with strains of S. aureus, S. epidermidis and E. faecalis. The presence of 20% (V/V) serum had little or no effect on the MIC, although 50% (V/V) serum increased MICs by 4-8 folds.
Laboratory-induced resistance to RP 59500 occurred in a stepwise fashion in broth cultures of S. aureus, S. epidermidis and E. facalis strains and the induction rate was slow and no more than four fold increases were observed.
Population analysis was performed on RP 59500 and the reference macrolides against S. aureus ATCC 25923 strain. Although low frequencies (less than 0.01%) of resistant sub-population were detected with EM, CAM, AZM and RXM, no RP 59500-resistant sub-population was detected in this study.

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