Antibacterial activity of rokitamycin against fresh clinical isolates]

We obtained bacterial strains which were clinically isolated and identified from outpatients with various infections in medical institutions throughout Japan. Possible antibacterial activities of rokitamycin (RKM) were examined against these isolates. Minimum inhibitory concentrations (MICs) were determined through a comparative study with reference drugs. The results of the study are summarized as follows. 1. Resistance patterns of 400 isolates which were highly resistant to macrolides (MLs) with MIC values > 100 micrograms/ml were classified into 55 patterns. Staphylococcus spp. showed cross resistance to 14-membered ring MLs with 100% cross resistance observed between erythromycin (EM) and clarithromycin (CAM), and 85.2% between EM and oleandomycin (OL). Fewer isolates showed strong resistance to 16-membered ring MLs than to 14-membered ring MLs. Cross resistances observed among the Staphylococcus isolates were 100% between acetylmidecamycin (MDM-AC) and kitasamycin (leucomycin (LM)), 93.9% between MDM-AC and josamycin (JM), and 53.3% between MDM-AC and RKM. Streptococcus spp. and Peptococcus spp. showed very similar resistance patterns to both 14- and 16-membered ring MLs, but resistance patterns to RKM were quite different. Most of anaerobic streptococci and Bacteroides fragilis group had similar resistance patterns to 14- and 16-membered ring MLs, but in some cases a pattern similar to that of Staphylococcus spp. was observed. 2. When ML-resistant bacteria isolated during 1975 to 1980 were compared to those isolated in 1986 and 1989, it was observed that resistance of Staphylococcus aureus remained almost unchanged, that of Streptococcus pyogenes was lower in the later years than during 1975 to 1980, but that of Streptococcus pneumoniae increased. 3. Most of ML-resistances of the resistant isolates were inducible, but extents of induction varied depending on drugs tested. Strong inductions were observed when 14-membered ring MLs were used, but inductions were minimal with 16-membered ring MLs. RKM appeared to induce resistance to the least extent. From these results, it appears that the RKM is quite useful clinically even in the 1990s.     

Bacteriological, pharmacokinetic and clinical studies of a rokitamycin syrup in pediatrics

Rokitamycin (RKM) dry syrup was administered to a group of pediatric patients. The results obtained are summarized as follows. 1. Of the recent isolates of Streptococcus pyogenes, fewer strains were highly resistant to RKM than to josamycin (JM), midecamycin (MDM), erythromycin and lincomycin. Also, macrolides (MLs)-resistant strains proved to be susceptible to RKM. 2. Recent isolates of Staphylococcus aureus, Streptococcus agalactiae, group G Streptococci, S. pyogenes, Streptococcus pneumoniae and Haemophilus influenzae were more susceptible to RKM than to midecamycin acetate and JM. Oral administrations of 10-15 mg/kg of the drug were followed by its peak concentrations of 0.07-0.77 micrograms/ml in the blood at 30 minutes in many patients, and by an undetectable level at 6 hours also in many of them. T1/2 values were 1.2-2.6 hours, and first 6-hour urinary excretion rates were 1.26-1.74%. 3. Fifty-two patients with acute upper and lower respiratory tract infections, Campylobacter enteritis, etc. were treated with RKM at about 20-40 mg/kg daily for 4-14 days, with an overall efficacy rate of 88.5%. 4. An eradication rate of 81.4% was achieved for 43 strains of 7 species isolated from the patients. 5. No abnormal laboratory test values were observed after treatment with drug 4 approximately 14 days. A side effect, stomach discomfort, was observed in 1 patient.     

Antimicrobial activities of macrolides against recent clinical isolates,and analysis of resistant mechanisms

We examined antibacterial activities of 4 kinds of macrolides, erythromycin (EM), clarithromycin (CAM), azithromycin (AZM) and rokitamycin (RKM), against 6 bacterial species of clinical strains isoleted in 2002. Bacterial isolates used were each 50 strains of methicillin-susceptible Staphylococcus aureus (MSSA), Streptococcus pyogenes, Streptococcus agalactiae, Moraxella (Branhamella) catarrhalis, Haemophilus influenzae and 43 strains of Streptococcus pneumoniae. S. agalactiae were derived from gynecological samples, and other species were isolated from respiratory specimens. Antimicrobial activities against S. aureus, S. pyogenes, S. agalactiae, M. catarrhalis and H. influenzae of 14-membered macrolides, such as EM and CAM, were higher than those of 16-membered macrolide, RKM. By contrast, against S. pneumoniae, RKM was more effective than 14-membered macrolides. Six, three and four strains of S. aureus, S. pyogenes and S. agalactiae, respectively, were resistant to macrolides. Thirty-five among 43 pneumococcal isolates were resistant, and 15 of the 35 were highly-resistant, MIC of > 128 micrograms/ml, to any one of EM, CAM or AZM. Isolation frequency of resistant strains to RKM was lower than those to 14- and 15-membered macrolides: only one strain was highly-resistant and 12 were intermediately-resistant. No resistant strain was recognized in M. catarrhalis and H. influenzae. Further, we analyzed the resistant mechanisms, methylation or efflux, of macrolide resistant strains by the double-disk method. Methylation was major mechanism in S. aureus, and in S. pyogenes, all of the resistance was caused by methylation. In S. agalactiae and S. pneumoniae, methylation and efflux shared about half and half.     

Studies on susceptibility of isolated organisms from pediatric infections against various antimicrobial agents

Twelve oral antimicrobial agents were tested for their antimicrobial activities against causative organisms isolated from pediatric infections. Activities of these antimicrobial agents against Streptococcus pyogenes were also examined in relation to T-antigen typing of the species. The results of the investigation are summarized as follows. 1. Against Staphylococcus aureus, rokitamycin (RKM), josamycin, ofloxacin, minocycline exhibited strong antimicrobial activities, and few strains of S. aureus showed resistance to these antimicrobial agents. More strains exhibited resistance to erythromycin (EM) than to other macrolide antibiotics (MLs) examined. Amoxicillin (AMPC)-resistance was often observed also. 2. Against S. pyogenes, beta-lactam antibiotics (beta-lactams) and RKM had MIC80 of 0.20 microgram/ml or below, and no resistant strains of this organism were observed against these antibiotics. Only 2 resistant strains (2.0%) of S. pyogenes to MLs were detected, but resistance to tetracyclines (TCs) was observed at a high frequency, with 71.4% or more strains among T-4, T-6, T-12 and T-28 antigen types exhibited resistance to TCs. Among the 21 strains of T-12 antigen type examined, only one strain (4.8%) was found resistant to MLs. These observations suggested that the reduction in the frequency of ML-resistant strains was not due to the reduction in the number of T-12 antigen type strains but due to losses of resistance factors against MLs of plasmids. 3. Antibacterial activities of beta-lactams and MLs against Streptococcus pneumoniae strains were good, similarly to activities against S. pyogenes. But many strains of S. pneumoniae were resistant to TCs. 4. New quinolone antimicrobial agents (quinolones) showed excellent activities against Branhamella catarrhalis strains with EM and RKM showing the next best activities. The number of resistant strains against quinolones, however, seemed to be on an increase. 5. Quinolones had strong antimicrobial activities against Haemophilus influenzae, few strains of which showed resistance to quinolones. AMPC had the next best activity, but approximately 10% of H. influenzae exhibited resistance to this antibiotic. 6. Against Campylobacter spp., quinolones and MLs showed the best activities with MIC80 values at or below 0.25 microgram/ml, and no resistant strains of the species against these antimicrobial agents were observed. Fosfomycin and TCs showed somewhat inferior activities to quinolones and MLs, with beta-lactams showing still lower activities. 7. Only few strains of Mycoplasma pneumoniae and Chlamydia trachomatis were examined, but MLs and TCs appeared to be effective against these organisms.(ABSTRACT TRUNCATED AT 400 WORDS)     

Comparison of antimicrobial and bactericidal activities and postantibiotic effects of macrolides antibiotics against clinical isolates, and examination of shape alteration by scanning electron microscope

We examined antibacterial activities of 4 kinds of macrolides (MLs), erythromycin (EM), clarithromycin (CAM), azithromycin (AZM) and rokitamycin (RKM), against 4 bacterial species of clinical strains isolated in 2004. Bacterial isolates used were 51 strains of methicillin-susceptible Staphylococcus aureus (MSSA), 20 of Streptococcus pyogenes, 68 of Streptococcus agalactiae, and 120 of Streptococcus pneumoniae. Macrolide resistance genes, ermB and mefE, in macrolide-resistant S. pyogenes and S. agalactiae, and all of pneumococci were analyzed by PCR. Antimicrobial activities against macrolide-susceptible MSSA of EM and CAM, were more potent than those of RKM. By contrast, against S. pneumoniae, RKM was more effective than EM, CAM and AZM. Against S. pyogenes and S. agalactiae, 4 antibiotics showed similar antimicrobial activities. Twelve, 1 and 2 strains of MSSA, S. pyogenes and S. agalactiae, respectively, were resistant to EM, CAM and AZM, whereas RKM was active to almost, but not quite, of them. Among 120 strains of S. pneumoniae, 76 (63.3%) were resistant to EM (MIC; > or = 0.5 microg/mL), and 23, 15 and 28 strains were highly resistant (MIC; > 128 microg/mL) to EM, CAM and AZM, respectively. By contrast, for RKM, there were far fewer resistant strains, and there was no highly resistant strain. PCR analyses of macrolide-resistant genes revealed that 1 resistant strain of S. pyogenes and 2 of S. agalactiae carried mefE and ermB, respectively. In the case of S. pneumoniae, 59, 19 and 5 strains, respectively, carried ermB, mefE and both ermB and mefe. We also studied about bactericidal activities and postantibiotic effects (PAE) of MLs using macrolide-susceptible, and ermB- and mefE-carrying S. pneumoniae, and observed morphological alterations of the strains treated with the drugs by a scanning electron microscope. It was demonstrated that RKM had superior bactericidal activities and PAE than other 3 drugs, and potent destructive effects to all of 3 strains.     

Annual changes in susceptibility of clinical isolates to midecamycin acetate

To investigate annual changes in the susceptibility of clinical isolates to midecamycin acetate (MDM-AC), minimum inhibitory concentrations (MICs) of MDM-AC were determined for clinical isolates obtained from outpatients since 1985. MDM-AC-resistant strains of Staphylococcus spp. and Streptococcus spp. have shown similar degrees of resistance to midecamycin and josamycin. Regarding this as macrolide resistance, proportions of macrolide-resistant strains tended to increase for Staphylococcus aureus and Streptococcus pneumoniae but to decrease for Streptococcus pyogenes. 1. For S. aureus, 8% of the strains isolated in 1985, 20% in 1987 and 20% in 1989 were macrolide-resistant. Of these macrolide-resistant strains, 70% or more in 1987 and 80% or more in 1989 were methicillin-resistant S. aureus (MRSA). 2. For S. pneumoniae, 8% of the strains isolated in 1985, 12% in 1987 and 12% in 1989 were macrolide-resistant, indicating a tendency for resistant strains to increase annually. 3. For S. pyogenes, 8% of the strains isolated in 1985, 4% in 1987 and 0% in 1989 were macrolide-resistant, showing a decreasing tendency. 4. MDM-AC is still thought to be a clinically useful antibacterial agent because it still shows antibacterial activity against 80% or more of Gram-positive cocci clinically isolated in recent years and a low degree of induction of macrolide resistance in Staphylococcus spp.     

Antimicrobial activity in vitro of cefaclor, a new oral cephalosporin

The antimicrobial activity of cefaclor, a new orally administered cephalosporin derivative, was studied in vitro against a variety of Gram-positive and Gram-negative clinical isolates. Both penicillin-resistant and penicillin-susceptible strains of Staphylococcus aureus were susceptible to cefaclor, with mean MICs of 1.44 and 0.93 microgram/ml, respectively. However, the MBC for penicillin-resistant S. aureus was higher than that for the penicillin-susceptible strains. All strains of Streptococcus pyogenes, Streptococcus viridans, and Streptococcus pneumoniae tested were highly susceptible to cefaclor; all strains of Streptococcus faecalis were highly resistant to cefaclor. Strains of Escherichia coli, Klebsiella sp., Proteus mirabilis, and Hemophilus influenzae were susceptible to cefaclor. Eighty per cent of strains of H. influenzae were inhibited by 5 micrograms/ml of cefaclor. Most strains of Enterobacter sp., indole-positive Proteus, Pseudomonas sp., and Serratia sp. were resistant to cefaclor.     

Microbiological, pharmacokinetic and clinical studies of rokitamycin dry syrup in the pediatric field

Rokitamycin (RKM), a newly developed macrolide antibiotic with a 16-membered ring, dissolves well under acidic conditions. It has been improved over other macrolides to minimize individual variations in its absorbability. We measured, using the GA-test, variations in gastric acidities of 43 children with ages between 1 to 14 years, and investigated the relationship between gastric acidities and pharmacokinetic values. Also activities (expressed in MICs) of antimicrobial agents were studied against clinically isolated 229 bacterial strains using an inoculum size of 10(6) cells/ml. Tested organisms included Streptococcus pyogenes (77 strains), Streptococcus agalactiae (29), Streptococcus pneumoniae (2), as Gram-positive cocci, and Haemophilus influenzae (1), Haemophilus parainfluenzae (1), Bordetella pertussis (12), Salmonella sp. (4) and Campylobacter jejuni (103) as Gram-negative bacilli. Against stock strains of bacteria, MICs of 10 drugs (RKM, erythromycin (EM), josamycin (JM), midecamycin (MDM), midecamycin acetate (MOM), clindamycin (CLDM), amoxicillin (AMPC), cefaclor (CCL), minocycline, ofloxacin (OFLX] were determined. Against isolates from patients who underwent treatment with RKM, MICs of only 4 drugs (RKM, EM, JM, MOM) were determined. Measurements were made on plasma and urinary concentrations of RKM and its urinary recovery rates after patients including 6 boys with ages between 5 years 1 month and 11 years 6 months were administered with RKM (dry syrup). Two groups of 6 boys were administered between meals with RKM at dose levels of 5 and 10 mg/kg, respectively. Clinical and bacteriological effects of RKM were evaluated for 175 patients including 5 cases of pharyngitis, 3 tonsillitis, 32 pneumonia, 17 mycoplasmal pneumonia, 34 atypical pneumonia, 28 streptococcal infections, 29 Campylobacter enteritis, 4 Salmonella gastroenteritis, and 23 enteritis due to unknown organisms. Five drop-out cases were excluded from the evaluations. In the evaluable cases, an average dose level used was 31.8 mg/kg/day, with a daily dose divided into 3 to 4 administrations and with an average treatment duration of 9 days. Adverse reactions of RKM and its effects on laboratory test values were investigated in these patients including the drop out cases. Obtained results of these studies are summarized below. 1. The GA-test produced pH values indicating that amounts of gastric acid were mostly either normal or high in 42 of the 43 subjects tested (97.7%), and only one low acid case (2.3%) was observed.(ABSTRACT TRUNCATED AT 400 WORDS)     

Clinical studies of rokitamycin dry syrup on skin and soft tissue infections in the pediatric fields

Rokitamycin (RKM) dry syrup, a newly developed macrolide antibiotic, was administered to children with ages between 6 months and 15 years and 10 months suffering from skin and soft tissue infections including 41 cases of impetigo, one case of staphylococcal scalded skin syndrome (SSSS) and 2 cases of subcutaneous abscess totalling 44 cases. The average daily dose level used was 31.3 mg/kg divided into 3 or 4 doses, for an average of 6 days of treatment. MICs of 4 different macrolide antibiotics including RKM, erythromycin (EM), josamycin (JM) and midecamycin acetate (MDM acetate) were determined against 32 bacterial strains isolated from these cases including 30 strains of Staphylococcus aureus and 2 strains of Streptococcus pyogenes. The inoculum level used was 10(6) cells/ml. Among these strains of bacteria, 20 strains of S. aureus and 1 strain of S. pyogenes were also used, at the same inoculum size, for the determination of MICs of 4 beta-lactam antibiotics including 3 different penicillins such as ampicillin (ABPC), methicillin (DMPPC) and cloxacillin (MCIPC) and cefaclor (CCL), a cephem antibiotic. RKM was then evaluated through the above treatment for its clinical efficacy, bacteriological effects, side effects and effects on laboratory test values. Obtained results are summarized as follows. 1. Activities of drugs tested were compared to each other. MIC90 of RKM against S. aureus averaged 0.39 microgram/ml, and against no strains of S. aureus showed MIC values of higher than 25 micrograms/ml, thus, the antibacterial activity of RKM against S. aureus was the highest among the 8 drugs tested. The activity of MCIPC was next highest followed by that of DMPPC, MIC determination was done on only 2 strains, or, for some drugs, only one strain, of S. pyogenes, and RKM showed activities somewhat lower than ABPC and EM, and similar to JM and CCL within the limited testing. 2. Clinical efficacies of RKM determined by doctors in charge were 97.6% in the 41 cases of impetigo, with good or excellent efficacies were observed, 100% in the single case of SSSS and the 2 cases of subcutaneous abscess. Thus an overall efficacy on the 44 cases was rated very high, at 97.7%. 3. Clinical efficacy rating according to accumulated scores was determinable in 37 cases including all the 3 diseases on the third day of treatment with an efficacy rate of 89.2%. Ratings were determinable on the fifth and the seventh days of treatment in 24 and 21 cases, respectively, with all the cases judged good or excellent.(ABSTRACT TRUNCATED AT 400 WORDS)     

Bacteriological, pharmacokinetic and clinical studies on a rokitamycin dry syrup in the pediatric field

Bacteriological, pharmacokinetic and clinical studies were done on the effect of rokitamycin (RKM, TMS-19-Q) in the field of pediatrics. The results are summarized below. 1. Antibacterial activities Antibacterial activities of RKM against Staphylococcus aureus (including 50 methicillin-sensitive and 50 methicillin-resistant strains), 18 strains of Haemophilus influenzae and 50 strains of Campylobacter jejuni were studied comparatively with activities of josamycin (JM), midecamycin (MDM), erythromycin (EM) and cefaclor (CCL) or ampicillin. Minimum inhibitory concentrations (MICs) of the 5 antibiotics against methicillin-sensitive S. aureus showed a wide variation but RKM was somewhat superior among them. MIC80 of those antibiotics tested against methicillin-sensitive S. aureus were as follows; RKM 1.56, JM 12.5, MDM 12.5, EM 6.25, and CCL 3.13 micrograms/ml. Among methicillin-resistant S. aureus (MRSA), ratios of strains highly resistant to these antibiotics (MIC greater than or equal to 100 micrograms/ml) to total number of strains tested were: 18% to RKM, and 26%, 34% and 48% to JM, MDM and EM, respectively, again showing the superiority of RKM and the proliferation of resistant organisms to EM. MICs of RKM against H. influenzae were distributed in a range between 0.78 and 12.5 micrograms/ml, which were similar to MIC range of CCL, and approximately twice as high as that of EM, but 4 folds lower than those of JM and MDM. Against C. jejuni, the MIC range of RKM was quite broad, 0.10-12.5 micrograms/ml, with a peak value of 0.20 micrograms/ml. The cumulative number of strains vs. MIC curve was similar to that of EM, and RKM was approximately 4 to 8 folds more effective than the other 3 antibiotics. 2. Absorption and excretion The absorption and the excretion of RKM were studied with its dry syrup preparations. Dose levels examined were 5 mg/kg in 2 cases, 10 mg/kg in 7 cases, 15 mg/kg in 2 cases and 20 mg/kg in 1 case. Peak concentrations of RKM in blood were not dose-dependent and were 0.16-0.23, 0.29-0.91, 0.35-0.46 microgram/ml and 0.53 microgram/ml, respectively, for the 4 dose levels. Most of drug levels dropped below the detection limit in 4 hours after the administration when dose levels up to 10 mg/kg were used, and when dose levels were at or above 15 mg/kg, 0.07-0.09 microgram/ml of RKM was detected in blood at 6 hours after the administration. Urinary recovery rates in 6 hours were between 0.19 and 3.31%.(ABSTRACT TRUNCATED AT 400 WORDS)     

Antimicrobial activities of sultamicillin against clinical isolates from upper respiratory tract infections

Sultamicillin (SBTPC) is a mutual prodrug in which ampicillin (ABPC) and a potent beta-lactamase inhibitor sulbactam (SBT) are ester-bound in an equimolar ratio. SBTPC is hydrolyzed during absorption after oral administration to provide ABPC and SBT for systemic circulation. In the present study, the antimicrobial activities of SBTPC against 50 isolates each of 6 species (Staphylococcus aureus, Klebsiella pneumoniae subsp. pneumoniae, Branhamella catarrhalis, Haemophilus influenzae, Streptococcus pneumoniae and Streptococcus pyogenes) of bacteria freshly obtained from upper respiratory tract infections were examined in relation to their bacterial beta-lactamase producing abilities. beta-Lactamase producing strains were identified using the acidometry disc method with benzylpenicillin (PCG) of cefazolin (CEZ) as a substrate, and their frequencies of appearance were calculated as follows: S. aureus 86%; K. pneumoniae subsp. pneumoniae 100%; B. catarrhalis 68%; H. influenzae 24%. Fourteen per cent of S. aureus strains examined were beta-lactamase positive using both PCG and CEZ acidometry discs. SBTPC, however, demonstrated excellent antimicrobial activities even against these beta-lactamase producing strains. Good activities were observed especially against those bacterial strains producing penicillinase (PCase). Average MIC80 values of SBTPC were 3.13 micrograms/ml for S. aureus and K. pneumoniae subsp. pneumoniae, 0.39 micrograms/ml for B. catarrhalis and H. influenzae, 0.05 micrograms/ml for S. pneumoniae and 0.025 micrograms/ml for S. pyogenes. As SBTPC was shown to possess excellent antimicrobial activities against PCase producing strains, the enhancement in activities of SBTPC compared to ABPC alone can be attributed to the inhibition of beta-lactamase by SBT which, as noted above, is a component of SBTPC in an equimolar ratio to ABPC.     

Comparative in vitro activity of LY 127935 (6059-S), seven cephalosporins, three aminoglycosides, carbenicillin, and ticarcillin

LY 127935 (6059-S), a new semi-synthetic beta-lactam antibiotic was tested simultaneously with 6 cephalosporins, 3 aminoglycosides, carbenicillin and ticarcillin against 398 clinical isolates of Gram-negative bacilli and Gram-positive cocci. Many of the organisms were selected for study because of known resistance to one or more of the clinically available antibiotics tested. Escherichia coli, Klebsiella, Serratia and Providencia were susceptible to LY 127935. Some resistant strains of Enterobacter, Proteus, Pseudomonas aeruginosa and Acinetobacter were also resistant to LY 127935, but many of the strains resistant to other antibiotics were susceptible to LY 127935. The activity of LY 127935 against Staphylococcus aureus, Streptococcus pneumoniae, Streptococcus pyogenes, Streptococcus viridans and Streptococcus bovis was similar to that of cephalexin and cephradine. LY 127935 was not active against methicillin-resistant S. aureus nor enterococcus.     

Antibacterial activities of piperacillin in several fresh clinical isolates

We investigated activity of piperacillin (PIPC) in comparison with 8 antibacterial reference drugs against several fresh clinical strains isolated from patients with infectious diseases in the respiratory tract and after surgical interventions in 1999. The following results were obtained: 1. PIPC had its MIC90 of 0.12-6 micrograms/ml in Gram-positive bacteria (Methicillin susceptible Staphylococcus aureus, Staphylococcus epidermidis, Streptococcus pyogenes, Streptococcus agalactiae, Streptococcus pneumoniae, Enterococcus faecalis) and showed its MIC of 1 microgram/ml or higher in 9 possible PRSP strains out of 38 isolates of S. pneumoniae but there were no possible isolates with evident resistance in other species of bacteria. 2. PIPC showed favorable antibacterial activities as its MIC90 were 2-8 micrograms/ml in Gram-negative bacteria (Escherichia coli, Klebsiella pneumoniae, Serratia marcescens, Citrobacter freundii, Pseudomonas aeruginosa, Moraxella (Branhamella) catarrhalis, Haemophilus influenzae), except for P. mirabilis in which its MIC90 was as high as 64 micrograms/ml. 11 out of 39 isolates of P. mirabilis were resistant to other drugs such as PIPC, ABPC, CTM and CZOP. 3. PIPC had its MIC90 of > 128 micrograms/ml in Bacteroides fragilis. From these results, PIPC was considered highly effective in several infections in view of maintaining its favorable antibacterial activities in several causative bacteria even today when 20 years had passed since its first application to clinical practice.     

Antimicrobial activity of cefteram comparison with other oral antibiotics

Antimicrobacterial activities of cefteram (CFTM) against clinical isolates collected in 1988 were compared with those of new beta-lactams. 1. Antibacterial activities of CFTM against Streptococcus pneumoniae, Streptococcus pyogenes, Haemophilus influenzae, Branhamella catarrhalis isolated from acute respiratory tract infections were 8- to 16-fold higher than those of cefaclor (CCL). 2. Activities of cefixime (CFIX) were superior to those of CFTM against B. catarrhalis, Escherichia coli, Klebsiella pneumoniae, Proteus mirabilis, but were inferior to CFTM against S. pneumoniae, S. pyogenes, Staphylococcus saprophyticus and Staphylococcus aureus. 3. Activities of cefuroxime were superior to those of CCL against each of the 4 tested bacterial species from acute respiratory tract infection and S. aureus by 4-fold, but were inferior to CFTM and CFIX against most of Gram-negative rods. 4. Sultamicillin (SBTPC) is considered to have an activity to inhibit beta-lactamase, but its MICs did not exceed the MICs of ampicillin by itself. SBTPC showed poor antibacterial activities against methicillin-resistant S. aureus (MRSA). Considering these observations, it is apparent that we are faced with a variety of factors in selecting antibiotics for best results.     

Studies of isolated organisms from otorhinolaryngological infections and their susceptibilities to macrolide antibiotics

To study current situation of pathogenic bacteria and their drug resistance to macrolide antibiotics in the otorhinolaryngological infections, 609 strains diagnosed as pathogen derived from 463 patients were collected from cohospitals or institutions during the period of 1980-1983. The results obtained were as follows: Gram-positive cocci (GPC) was dominant (410 strains) and major species were S. aureus (135 strains), S. pneumoniae (81 strains), S. epidermidis (68 strains) and S. pyogenes (65 strains). In Gram-negative bacteria giving 147 strains and 43 strains, of anaerobes prevailing species were H. influenzae, P. aeruginosa and Peptostreptococcus spp. Representative species in the diseases were S. aureus (26.6%), S. epidermidis (24.5%), and P. aeruginosa (12.8%) in acute otitis media, S. aureus (34.4%), S. epidermidis (17.7%) and P. aeruginosa (14.6%) in acute exacerbation of chronic otitis media, S. epidermidis (17.0%), S. aureus (16.1%) and H. influenzae (13.4%) in acute paranasal sinusitis, S. pyogenes (29.1%), S. pneumoniae (19.6%) and S. aureus (15.1%) in acute tonsillitis. Although most of isolates were susceptible to macrolides, 62 resistant strains to macrolides were found in 501 strains and the resistant rates were 26.7% in S. aureus, 23.1% in S. epidermidis and 6.5% in S. pyogenes. The resistant pattern was somewhat different against each macrolides, resistant strains giving over 100 micrograms/ml in MIC were 55/62 in erythromycin, 35/62 in josamycin and midecamycin and 7/62 in TMS-19-Q, a new macrolide.     

The in vitro activity of some 14-, 15- and 16- membered macrolides against Staphylococcus spp., Legionella spp., Mycoplasma spp. and Ureaplasma urealyticum.

Erythromycin is a macrolide antimicrobial chemically comprised of a 14-membered lactone ring substituted with a neutral (cladinose) and an amino (desosamine) sugar. Recently, a number of new macrolide molecules have been identified containing either 14-, 15- or 16-membered substituted lactone rings. In this study the authors have determined the in vitro activity of roxithromycin and clarithromycin (both 14-membered macrolides), azithromycin (a 15-membered macrolide or azalide) and midecamycin acetate (a 16-membered macrolide) against clinical isolates of Staphylococcus spp., (including methicillin-susceptible and -resistant isolates), Legionella spp., Mycoplasma spp. and Ureaplasma urealyticum. Minimum inhibitory concentrations of the macrolides for the clinical isolates of Staphylococcus spp. examined were widely distributed. However, midecamycin acetate retained activity against those isolates of Staphylococcus spp. exhibiting inducible resistance to erythromycin and the other macrolides tested. Isolates characterised by constitutive resistance to erythromycin were also resistant to midecamycin acetate. All of the macrolides were very active against Legionella spp., with clarithromycin demonstrating the greatest potency (MIC range: less than or equal to 0.03-0.06 mg/l). Isolates of Mycoplasma pneumoniae and Ureaplasma urealyticum were susceptible to all of the macrolides tested. However, erythromycin, roxithromycin, clarithromycin and azithromycin were poorly active against isolates of Mycoplasma hominis. By contrast, the same isolates were susceptible (MIC range: 0.008-0.12 mg/l) to midecamycin acetate.     

Laboratory and clinical studies of rokitamycin dry syrup in the field of pediatrics

Laboratory and clinical studies on rokitamycin (RKM) dry syrup, a new macrolide antibiotic, were carried out in the field of pediatrics. The results are summarized as follows. 1. Plasma concentrations and urinary recovery rates after oral administration on fasting of RKM dry syrup at doses of 10 mg/kg and 20 mg/kg to 2 and 1 cases, respectively, were determined. Peak plasma levels were obtained in 30 minutes after administration of both dosages with half-lives of 1.5 to 2.2 hours. A clear-cut dose response was observed. Urinary recovery rates in the first 6 hours after administration ranged from 1.75 to 2.26%. 2. The MICs of RKM against 80 clinical isolates (Streptococcus pyogenes 9, Streptococcus pneumoniae 14, Branhamella catarrhalis 4, Haemophilus influenzae 27, Haemophilus parainfluenzae 9, Haemophilus haemolyticus 2, Haemophilus parahaemolyticus 14 and Campylobacter jejuni 1) were compared with MICs of midecamycin acetate (MOM), josamycin (JM) and erythromycin (EM). The antibacterial activity of RKM was superior to those of MOM and JM and slightly inferior to that of EM. 3. Twenty-eight pediatric patients with acute infectious diseases (acute tonsillitis 4, streptococcal infection 4, acute bronchitis 9, pneumonia 4, mycoplasmal pneumonia 2 and Campylobacter enteritis 5) were treated with RKM dry syrup at a daily dose of 12-42.9 mg/kg t.i.d. as a rule. Efficacy rates were 92.9% clinically and 58.6% bacteriologically. 4. No adverse reactions were observed. Abnormal laboratory findings were mild; thrombocytosis in 2 and eosinophilia in 1. 5. The taste and the odor of RKM dry syrup preparation were sufficiently tolerable for the pediatric patients to accept it.     

Clinical laboratory approach to estimate effective administrative dose of minocyclin. Reevaluation of in vitro MIC break points in disc susceptibility test

Antimicrobial activities of minocycline (MINO) against various clinical isolates, 270 strains obtained in 1988, were determined and the reliability of the MINO disc susceptibility test in estimating approximate values of MICs was studied. Clinical significance of a 4 category system for the interpretation of the disc tests, which is widely used in Japan, and that of a 3 category system used in the USA and Europe, were also evaluated to determine which system would be more suitable for the evaluation of proper dose levels of administration. In this study, MICs were determined using the agar dilution method at an inoculum level of 10(6) CFU/ml. MIC80 values of MINO against Staphylococcus aureus, Staphylococcus epidermidis and Streptococcus pneumoniae were all less than or equal to 0.78 micrograms/ml. Those against Haemophilus influenzae, Escherichia coli, Klebsiella pneumoniae, Proteus mirabilis and Proteus vulgaris were 0.39, 6.25, 3.13, 25, 50 micrograms/ml, respectively. MIC80 values against Pseudomonas aeruginosa, Serratia marcescens, Enterobacter spp., and Citrobacter spp. were 50, 100, 50 and 12.5 micrograms/ml, respectively. The inhibition zones obtained with the disc method were compared with MICs. The results of MINO disc susceptibility test either with 200 micrograms disc (Showa) or 30 micrograms disc (prepared in this laboratory) were well correlated with MICs, showing the reliability of the disc method in estimating approximate values of MICs. In the 4 category classification system currently used, break points in MIC values proposed are ( ) MIC less than or equal to 2 micrograms/ml, (++) MIC greater than 2-10 micrograms/ml, (+) greater than 10-50 micrograms/ml, (-) MIC greater than 50 micrograms/ml. The results obtained with 200 micrograms and 30 micrograms discs showed false positive in 26.6% and 20.5% of the samples, and false negative in 5.8% and 23.6% of the samples, respectively. The disc results of S. aureus, S. epidermidis, S. pneumoniae, etc. were relatively well classified, but those of E. coli, K. pneumoniae, Proteus spp. were not, showing more false positive results. Changing the lower 2 MIC break points in the 4 category system to: ( ) MIC less than or equal to 3 micrograms/ml and (++) MIC greater than 3-15 micrograms/ml, the false positive results with both 200 micrograms and 30 micrograms discs were reduced to 12% and 6.2%, respectively. The false negative results were 5.8% and 23.6%, respectively.(ABSTRACT TRUNCATED AT 400 WORDS)     

Comparative antimicrobial activity and post-antibiotic effect of azithromycin, clarithromycin and roxithromycin against some respiratory pathogens

Recent macrolide derivatives, roxithromycin, azithromycin and clarithromycin show more favourable pharmacokinetic characteristics in comparison to old ones and some differences in antibacterial activity. With the aim of improving our understanding of some aspects of their action against respiratory pathogens, we determined the MICs and MBCs of Streptococcus pneumoniae, Streptococcus pyogenes, Staphylococcus aureus, Moraxella catarrhalis and Haemophilus influenzae. Azithromycin was the most active agent against Haemophilus influenzae and Moraxella catarrhalis, while clarithromycin was more active against Streptococcus pneumoniae, Streptococcus pyogenes and Staphylococcus aureus with MICs similar to those of erythromycin. The bactericidal activity of all tested derivatives was weak against Staphylococcus aureus (MBC/MIC ratio approximately 16) and against Moraxella catarrhalis (MBC/MIC ratio, 8-16), but good against Staphylococcus pneumoniae, Streptococcus pyogenes and Haemophilus influenzae (MBC/MIC ratio, 2-4). The determination of killing curves in the presence of 2 MIC and 10 MIC of azithromycin, clarithromycin and roxithromycin confirmed their weak bactericidal activity against Staphylococcus aureus and Moraxella catarrhalis as well as their effective activity against Streptococcus pyogenes and Streptococcus pneumoniae. Azithromycin showed the highest bactericidal activity against Haemophilus influenzae. As expected, the three derivatives produced a quite prolonged PAE when exposed to 5 MIC for 1 h, ranging between 2-4 h. The bactericidal activity and the prolonged PAE of new macrolides for the most common respiratory pathogens should assure a good clinical activity in respiratory infections including those sustained by Haemophilus influenzae, which is less susceptible to erythromycin and other old macrolides.     

Fosfomycin susceptibility of clinical isolates from otorhinolaryngological infections

To investigate the clinical and bacteriological usefulness of orally administered fosfomycin calcium (FOM), the susceptibility of 558 strains to FOM was determined. These strains were isolated at our Center, between Feb. 1982 and Feb. 1983 from otorhinolaryngological infections. Several other drugs were also tested on the same strains for comparison. The results were as follows. The MIC80 of FOM was 6.25 micrograms/ml against each of aerobic Gram-positive cocci such as S. aureus, S. pyogenes, S. pneumoniae, anaerobic Gram-positive cocci such as Peptococcus spp., and H. influenzae. P. mirabilis, indole-positive Proteus spp., P. aeruginosa and K. pneumoniae were inhibited, respectively, at 3.13, 12.5, 12.5 and 50 micrograms/ml. Most of the MICs were between 3.13 and 12.5 micrograms/ml, and the difference between the MIC50 and the MIC90 was only 1 to 2 tubes since there were few resistant strains. With the comparative drugs, there was a reduction seen in the sensitivities of pipemidic acid (PPA), ampicillin (ABPC), and cephalexin (CEX) against, respectively, P. aeruginosa, beta-lactamase-producing H. influenzae and S. aureus. FOM showed good and constant sensitivity for the weakly PPA-sensitive P. aeruginosa, weakly ABPC-sensitive beta-lactamase-producing H. influenzae and weakly CEX-sensitive S. aureus. The MICs of FOM against the main problematic isolates from otorhinolaryngological infections were mostly between 3.13 and 12.5 micrograms/ml, including the above weakly PPA-, ABPC- and CEX-sensitive strains. Based on these values, FOM may be said to have moderate antibacterial efficacy when administered orally in the usual dose.(ABSTRACT TRUNCATED AT 250 WORDS)