We examined the distribution of mutations in DNA gyrase A protein gene, which is considered to be especially important in the mechanism responsible for high-level quinolone resistance, in clinical isolates of Staphylococcus aureus. The rate of occurrence of mutations at serine-84 in the DNA gyrase A protein was investigated by polymerase chain reaction (PCR) and Hinf I digestion in 110 clinical isolates of Staphylococcus aureus from the Tohoku district, collected in 1992, and the following results were obtained.(1) Serine-84 mutations were very widely distributed among the isolates against which the MICs of ofloxacin were above 4μg/ml.(2) Serine-84 mutations were observed without exception in highly resistant strains (MIC≥16μg/ml).(3) The mutant/nonmutant strain ratios were essentially the same for ofloxacin and for 8 other quinolone agents, but the borderline MICs between the mutant and non-mutant strains varied from agent to agent.(4) There was no significant difference in the mutant/non-mutant strain ratios among MRSA, MSSA (without mecA gene), and MSSA (with mecA gene). So we concluded that there was no correlation between serine-84 mutations and methicillin resistance.

View full abstract

We investigated in vitro and in vivo antichlamydial activities of newly developed fluoroquinolones. The MICs of several quinolones; sparfloxacin (SPFX), tosufloxacin (TFLX), ofloxacin (OFLX), cipfloxacin (CPFX), DU-6859 a, AM-1155, minocycline (MINO) and clarithromycin (CAM), against the reference strains of Chlamydia pneumoniae TW-183, Chlamydia trachomatis D/UW-3/Cx and Chlamydia psittaci Budgerigar were determined. Among these fluoroquinolones, SPFX, DU-6859 a and AM-1155 showed potent in vitro activity against all three Chlamydia sp., with a MIC value of 0.063μg/ml, which was significantly superior to those of OFLX (0.5μg/ml) and CPFX (0.5-1.0μg/ml). Mice were infected with 10⁵ inclusion-forming units of C. psittaci by intranasal inoculation to establish the pneumonia. Test drugs were administered orally twice a day for 7 days from 24 h after infection. The therapeutic effects of eight compounds (SPFX, TFLX, OFLX, CPFX, DU-6859 a, AM-1155, MINO and CAM) were evaluated. Each drug was administered at one of 3 different doses, 1.25, 2.5 and 5 mg/kg, twice a day. The survival rates of mice with the experimental pneumoniae were 75% and 100% after treatment with SPFX at dosages of 1.25 and 2.5 mg/kg, respectively. The efficacy was equal to that of MINO and higher than that of the other quinolones tested. Based on the above results, we concluded that SPFX shows promise as a drug for the treatment of chlamydial infections.

View full abstract

A total of 188 Pseudomonas aeruginosa isolates from clinical specimens in the Showa University Fujigaoka Hospital during the 20 months from April 1992 to November 1993 were epidemiologically examined, by O-serotyping and determination of MICs of various anti-Pseudomonas β-lactam antibiotics. The following results were obtained.
1. Of the total isolates, 79 (42%), 55 (29%), and 38 (20%) were isolated from the respiratory tract, urinary tract, and pus specimens, respectively. Most of them were distributed in the wards of the emergency center, and department of urology, surgery, gastroenterology, and respiratory medicine.
2. Of the total isolates, 55 (29%), 34 (18%), and 19 (10%) were O-serotypes E, G, and A, respectively. These values were higher than those for the othter O-serotypes such as B, C, D, F. H, I, K, and M. No serotype J and L strains were isolated.
3. The MIC₅₀ of the carbapenems such as imipenem, panipenem, meropenem, and biapenem ranged from 0.39 to 1.56μg/ml. The MIC₅₀ and MIC₉₀ of cefclidin were 0.39 and 25μg/ml, and those of ceftazidime were 1.56 and 12.5μg/ml, respectively. These antibiotics had higher antibacterial activities against the isolates tested than cefotaxime, latamoxef, cefsulodin, cefoperazone, aztreonam, piperacillin, and ticarcillin.
4. Only 10 (5%) of the total isolates were resistant to the carbapenems. Six (60%) of these isolates were isolated from respiratory tract specimens.
5. Eighteen (64%) of the 28 strains resistant to cefclidin (14% of the total isolates) were isolated from the urinary tract specimens, and 3 (11%) were from the respiratory tract specimens.
6. Only 1 (3%) of the 37 strains resistant to the carbapenems or cefclidin was cross-resistant.
7. Twenty-one (38%) of the serotype E strains had a higher cefclidin-resistance rate than any other serotype strains. Two (11%) of the serotype A strains had a higher carbapenem-resistance rate.
8. No serotype G strain resistant to cefclidin was isolated.
9. All the cefclidin-resistant strains were significantly dissociated from the regression line for the relationship between the MICs of cefclidin and ceftazidime. The MICs of cefclidin against these isolates were lower than those of ceftazidime, suggesting that the mechanism of resistance to the two cephalosporins in P. aeruginosa was different.

View full abstract

The effficacy of 11 oral antimicrobial agents was determined by the micro broth dilution method against 91 penisillin-resistant and 210 penicillin-susceptible strains of Streptococcus pneumoniae isolated from various clinical specimens, from 1992 to 1993. The following drugs were tested: benzylpenicillin (PCG), ampicillin (ABPC), cefaclor (CCL), cefixime (CFIX), cefotiam (CTM), cefdinir (CFDN), cefpodoxime (CPDX), cefditoren (CDTR), cefcamate (CCMT), erythromycin (EM) and ofloxacin (OFLX). The medium used was cation-adjusted Mueller-Hinton broth supplemented with 0.5% yeast extract, 15μg of nicotinamide adenine dinucleotide (NAD) per ml and 2% lysed horse blood. Eight (2.7%) of the 301 strains were penicillin-resistant (MIC of PCG:≥2μg/ml), 83 (27.6%) were intermediate (MIC: 0.125-1μg/ml), and 210 (69.8%) were penicillinsusceptible (MIC:≤0.063μg/ml). The MIC₉₀ of PCG, ABPC, CCL, CFIX, CTM, CFDN, CPDX, CDTR, CCMT, EM, OFLX for penicillin-susceptible strains were ≤0.063μg/ml, ≤0.063μg/ml, 1μg/ml, 2μg/ml, 0.125μg/ml, 0.25μg/ml, 0.125μg/ml, 0.125μg/ml, 0.125 geml, >128μg/ml, 2μg/ml, respectively, and for penicillin-resistant and -intermediate strains they were 1μg/ml, 2μg/ml, 128μg/ml, 16μg/ml, 2μg/ml, 4μg/ml, 2μg/ml, 0.5μg/ml, 0.5μg/ml, >128μg/ml, 2μg/ml, respectively. According to the MIC breakpoint of cefaclor, which was determined by National Committee for Clinical Laboratory Standards (NCCLS), 80.7% of the 301 strains were cefaclorsusceptible (MIC of CCL:≤8μg/ml), 2% were intermediate (MIC: 16μg/ml) and 17.3% were cefaclor-resistant (MIC:≥32μg/ml). Among the oral cephem antibiotics tested, CCMT and CDTR showed the lowest MIC (≤4μg/ml). 33% of penicillin-susceptible strains and 67% of penicillinresistant strains showed resistance to erythromycin (≥1μg/ml), and 6% of penicillin-susceptible strains and 9% of penicillin-resistant strains showed resisntance to ofloxacin (≥4μg/ml). The isolates were distributed among 23 serotypes. Group 19, group 23, group 6 and type 14 strains frequently showed decreased penicillin susceptibility.

View full abstract

Both prompt initiation of chemotherapy with appropriate antimicrobial agents and augmentation of immunological host defense, in addition to nutritional improvement, have been accepted as favorable supportive countermeasures in managing septic patients with hematological malignancies. In the present study, we examined recent trends in the species of microorganism isolated and evaluated the usefulness of surveillance culture in the management of septic patients with hematological neoplasia. We also examined prognostic factors and risk factors for fatal sepsis. The study enrolled a total of 348 patients (15 to 90 years of age, median 55.5) who received antineoplastic agents from 1986 through 1992 in our institute, and a total of 660 of febrile episodes, which were considered to be definitely or highly suggestive of sepsis, were analyzed. The risk factors for fatal septic complication were determined by multivariate statistical analysis employing 187 patients who developed sepsis during or after anti-neoplastic chemotherapy. The rates of positive blood culture were high in the following six patient groups: patients with severe granulocytopenia and/or those who responded poorly to antineoplastic chemotherapy, those with indwelling central venous catheter and those with hypoalbuminemia, shock and DIC. The species of microorganisms isolated from the blood of septic patients consisted of aerobic gram-positive cocci (43.7%), gram-negative bacilli (38.7%), anaerobes (9.9%) and fungi (7.6%). The species of microorganism cultured from blood were in accordance with those detected by surveillance cultures; with the rates of agreement, 60.3% in throat swab culture, 56.0% in stool culture and 21.9% in urine culture. The number of cases in which the species of microorganism detected by blood culture agreed with those isolated from either of the three specimens used for surveillance culture was 253 among a total of 302 (83.8%). Among the cases with positive blood culture for Pseudomonas aeruginosa, the sum of rates of agreement with the results of surveillance cultures was highest, 55/57 (96.5%), followed by methicillin-sensitive Staphylococcus aureus (MSSA) 11/12 (91.7%), Enterococcus faecalis 28/31 (90.3%), methicillin-resistant Staphylococcus aureus (MRSA) 13/15 (86.7%) and Enterobacter cloacae 13/15 (86.7%). Statistical analysis demonstrated clearly that six clinical conditions, i. e., septic shock, poor responsiveness to anti-neoplastic chemotherapy, hypoalbuminemia, indwelling central venous catheter, fungemia and DIC, were statistically significant as facotrs indicating high risk for fatal septic complication in patients with hematological malignancies (P<0.05).

View full abstract

We investigated the susceptibity to quinolones and other antimicrobacterial agents of 1, 697 Staphylococcus aureus clinical isolates from the Tohoku district collected over the last eight years. The incidence of methicillin-resistant Staphylococcus aureus (MRSA) rose from 25.5% to 49.1% during the eight years. During the above period, susceptibity to ofloxacin remained at almost the same level for methicillin-susceptible Staphylococcus aureus (MSSA). On the other hand MRSA became more resistant year by year, and the MIC₉₀ of ofloxacin against MRSA rose from 0.78μg/ml in 1986 to 64μg/ml in 1993. This tendency was observed very frequently among isolates from all institutions and specimens, irrespective of whether they were from in- or out-patients. In was also found that these isolates were generally resistant to quinolones other than ofloxacin.

View full abstract

The antimicrobial activities of meropenem (MEPM), a new carbapenem antibiotic, were investigated and compared with those of imipenem (IPM), ceftazidime (CAZ) and ciprofloxacin (CPFX) against clinically isolated strains from patients with urinary tract infection (UTI) during the period from January to December in 1993. The antimicrobial activity of MEPM against Staphylococcus aureus was stronger than those of other three drugs and against Coagulase negative Staphylococci and Enterococcus faecalis were slightly lower than those of IPM. Against Escherichia coli, Klebsiella pneumoniae, Enterobacter spp., Citrobacter freundii, Proteus mirabilis, Serratia marcescens and Pseudomonas aeruginosa were lower than those of the other three drugs. MEPM and IPM showed correlation and cross resistance in a correlogram against Staphylococcus aureus, Coagulase negative Staphylococci, Enterococcus faecalis, Enterobacter spp., Serratia marcescens, Pseudomonas aeruginosa. The sensitivity of Proteus mirabilis against IPM was lower than against MEPM. The good antimicrobial activities of MEPM against new isolates from UTI indicates its usefulness as well as the potency.

View full abstract