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Susceptibility testing of mupirocin (MUP) was performed by an agar dilution method according to the National Committee for Clinical Laboratory Standard (NCCLS) to detect the MUP resistance. A total of 434 isolates of methicillin-resistant staphylococci were examined and all of 205 isolates of methicillin-resistant Staphylococcus aureus (MRSA) from 43 hospitals nationwide in 1993 were sensitive to MUP. However, MUP resistance emerged among 228 isolates [185 isolates (88 cases) of MRSA and 43 isolates (28 cases) of methicillin-resistant coagulase negative staphylococci (MR-CNS)] from nasal swabs of patients with MUP treatment between Sep 1996 and Feb 2000 in the Nagoya University Hospital. The high-level MUP resistance (MIC > or = 512 micrograms/mL) was isolated from two patients, one isolate of MRSA and four of S. hominis, respectively. Low-level MUP resistance (MIC 8-128 micrograms/mL) was isolated from three patients, 11 isolates of MRSA, one of S. chromogenes and five of S. epidermidis, respectively. The mupA which encodes the MUP resistant isoleucyl-tRNA synthetase (IRS) were investigated by PCR in these MUP resistant isolates. The mupA was detected only in high-level MUP resistant S. hominis, but not detected in high-level MUP resistant MRSA and low-level MUP resistant isolates. We also investigated the characteristics of the patients with MUP resistance. All of MUP resistant staphylococci were isolated after initiation of MUP treatment. Four patients with MUP resistant MRSA and low-level MUP resistant MR-CNS had MRSA infectious disease and MUP resistant strains were successfully eradicated with vancomycin treatment in two patients. MUP high-level resistant S. hominis, has emerged after MUP treatment for eradication of MRSA. Clinical guidelines for the prudent use of MUP should be generally adopted with careful monitoring of emergence of MUP resistance.

Penicillinase I-, II- and III-producing R-plasmid of Escherichia coli were transferred to Escherichia coli 177, KC-14, and 444. These strains are highly virulent in mice. This study was conducted to investigate the influence of conjugative R-plasmid on the virulence of its host strains. Escherichia coli 177 after penicillinase I- or III-producing R-plasmids transfer retained parental levels of virulence. On the other hand, penicillinase II-producing transconjugants showed reduced virulence in mice. The virulence of its revertants, in which R-plasmid was eliminated by heat, were equivalent to that of the host strain. It is suggested that the decrease in the virulence of transconjugants was not due to transferred R-plasmid. The reduced virulence of the these transconjugants may be due to alterations in their components such as the lipopolysaccharides in the cell envelope.

The virulence of Enterococcus faecalis in the urinary tract in mice was studied. Pyelonephritis was distinctly caused by E. faecalis which have a high affinity to mouse kidneys. This infection was continuous, but did not turn into sepsis. The relationship between the production of hemolysin or protease and the virulence in the urinary tract was investigated without finding any distinct association. It is concluded that E. faecalis is a pathogenic organism in the urinary tract and presumably induces a severe infection in the compromised host.

We determined the MICs of ampicillin, methicillin, cefaclor, cefixime, cefteram, ofloxacin and ciprofloxacin against a total of 1,448 strains from 11 species: 464 strains of Staphylococcus aureus, 306 strains of Streptococcus pneumoniae, 114 strains of Streptococcus pyogenes, 37 strains of Branhamella catarrhalis, 329 strains of Haemophilus influenzae, 32 strains of Escherichia coli, 66 strains of Klebsiella pneumoniae, 26 strains of Enterobacter cloacae, 20 strains of Serratia marcescens, 12 strains of Pseudomonas aeruginosa and 42 strains of Acinetobacter calcoaceticus, isolated from the throat swab and the sputum of 2,539 patients with respiratory infections who visited 21 private clinics in Tohoku district of Japan during the period from January to April in 1989. Ciprofloxacin and ofloxacin were more active against S. aureus, B. catarrhalis, P. aeruginosa and A. calcoaceticus than other antibiotics. Ampicillin and cefteram were more active against S. pneumoniae and S. pyogenes than other antibiotics. New-quinolones and cephems of new-generation were active against H. influenzae, E. coli, K. pneumoniae, E. cloacae and S. marcescens. Of 30 strains of S. aureus which were resistant (MIC greater than or equal to 12.5 micrograms/ml) to ampicillin, only one strain was resistant (MIC greater than or equal to 12.5 micrograms/ml) to methicillin. Twenty strains (6.5%) of S. pneumoniae and 49 strains (14.9%) of H. influenzae were resistant (MIC greater than or equal to 1.56 micrograms/ml) to ampicillin. Of 101 strains of H. influenzae of which their beta-lactamase activity was determined by Nitrocephin-method, 27 (26.7%) were beta-lactamase-positive strains. The above results indicated that MRSA is only rarely found in primary care clinics but the incidence of ampicillin-resistant H. influenzae in primary care clinics is almost the same as that of the intensive care clinic, i.e. medical school-affiliated hospitals. Therefore caution should be exercised as regards antibiotic resistance of the causative organism even in primary care clinics.

The effect of insulin on the incidence of experimental Serratia marcescens cystitis in alloxan-induced diabetic mice was studied. The symptoms in diabetes were improved by injection of insulin (1 I.U./b.i.d.) for 3 days. Diabetic mice treated with insulin showed lower susceptibility to cystitis with S. marcescens than non-treated diabetic mice, but slightly higher than normal mice. It was, therefore, suggested that the insulin treatment was important for prevention of S. marcescens cystitis. The prevention of cystitis in insulin-treated diabetic mice was possibly due to the increase of urea nitrogen that inhibits the growth of S. marcescens in urine.

Intravenous and intraperitoneal injections of slime from Acinetobacter calcoaceticus TMS266 induced leukopenia and death in mice. The leukopenia was characterized by a decrease in neutrophil count , followed by death of mice. This decrease of leukocytes was profound and supposed to contribute to the enhancement of virulence of other bacteria such as Escherichia coli. In mice treated with sublethal doses of the slime, the slime could not show its capacity to reduce circulating leukocytes . Introduction Acinetobacter calcoaceticus has been isolated from patients with urinary tract infectionsu , pneumonia2), or septicemia3). Although Acinetobacter calcoaceticus infections have been studied in recent years , relatively little is known about the pathogenesis concerned4)5). Previous studies concerning the pathogenicity of Acinetobacter calcoaceticus have confirmed the role of slime of this bacterial species6)7) . It has been demonstrated that the slime produces antiphagocytic and lethal effects in mice . In this study, the slime-induced leukopenic and lethal effects were further characterized . Materials and Methods Organism. Acinetobacter calcoaceticus TMS266, originally isolated from a human clinical specimen, was supplied by Prof. S. Goto (School of Medicine, Toho University , Tokyo). Bacterial slime. Slime was obtained from the strain as indicated and was purified by methods described previously6). Slime was extracted with saline from 48-hours bacterial cultures grown on sheets of cellophane overlying brain heart infusion agar (Difco). The crude slime was precipitated with cold ethanol . After treatment with chloroform-i-amylalcohol, 0.1 N sodium hydroxide, and cethylpyridinium chloride, in that order, the purified slime was obtained. Chemical components of the slime were determined by methods described previously6). The slime had high contents of sugar , protein, and orcinol reaction-positive substances. Animals. Four-week-old male mice of ddY strain weighing 17 to 18g were used and were supplied with water and laboratory chow ad libitum. Animal challenge. Groups of ten mice were injected intravenously or intraperitoneally with 0.2ml of twofold dilutions of the slime. Animals were observed daily for up to five days and the LD50 value was estimated by the Probit method. Leukocyte counts. Leukocyte counts were made on peripheral blood samples collected retroorbitally . The results are presented in terms of average of five mice per group .