Study on susceptibilities of freshly isolated strains to macrolide antibiotics

Macrolide (ML) susceptibilities of clinically isolated bacteria obtained freshly during 1989 were determined and year to year differences in ML-resistances of the clinical isolates in our laboratory were examined with epidemiological consideration in mind. 1. The distribution of minimum inhibitory concentrations (MICs) of MLs against isolates of Staphylococcus aureus showed 2 peaks, one peak representing S. aureus isolates susceptible to MLs and the other peak representing those resistant to MLs. Proportions of resistant isolates to various MLs were 36% to erythromycin, 24% each to kitasamycin, josamycin, midecamycin and midecamycin acetate. MICs of rokitamycin (RKM), however, distributed themselves into 3 peaks of less than or equal to 0.39 micrograms/ml (76%), 1.56-3.13 micrograms/ml (12%) and greater than or equal to 100 micrograms/ml (12%). Staphylococcus spp. including Staphylococcus epidermidis showed different resistance characteristics to 14-membered ring MLs and to 16-membered ring MLs. Further, the proportion of resistant organisms to RKM was the smallest among proportions of resistant organisms to various 16-membered ring MLs tested. These differences in proportions of resistant organisms to different MLs may have resulted from differences in resistance induction activities of different MLs. The above described ratios of resistant organisms to MLs among S. aureus did not vary since 1975 among clinical isolates tested in our laboratory. 2. Four per cent (4%) of Streptococcus pyogenes isolates were MLs resistant, and 18% of Streptococcus pneumoniae isolates were resistant to MLs. Among the isolates tested in our laboratory since 1985, resistant isolates of S. pyogenes are clearly decreasing and those of S. pneumoniae seem to be increasing.(ABSTRACT TRUNCATED AT 250 WORDS)     

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.     

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.     

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.     

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)     

Study of macrolide, lincosamide, and streptogramin B antibiotics resistance in Staphylococcus aureus

Macrolide antibiotics (Mac) consist of a 12- to 16-membered lactone ring combined with a sugar moiety, and they inhibit protein synthesis via binding to 23S ribosomal RNA in bacteria. The 14- and 16-membered Mac are used for treating infectious diseases caused by Gram-positive and other bacteria; e.g., Haemophilus influenzae, Bordetella pertussis, Legionella pneumophila, Campylobacter, Treponema pallidum and Mycoplasma. Resistance to macrolide, lincosamide, and streptogramin-B (MLS) antibiotics in staphylococci is known to have the following mechanisms: 1) alteration of the target on ribosome due to dimethylation of a specific adenine residue in the 23S ribosomal RNA by the product of the erm gene, and consequently a decrease in binding of MLS antibiotics; 2) inactivation of streptogramin-B (STG-B) and lincosamide by the products of the sbh (encoding streptogramin B hydrolase) and linA' (encoding 3-lincomycin 4-clindamycin O-nucleotidyltransferase) genes, respectively; and 3) active efflux of Mac and STG-B antibiotics determined by the msrA and msrB genes in Staphylococcus epidermidis and Staphylococcus xylosus, respectively, both of which appear to act as an ATP-dependent efflux pump. I have shown that Staphylococcus aureus 8325(pEP2104) exhibits inducible resistance to PMS (partial macrolide and streptogramin B)-antibiotics [the 14-membered macrolides, erythromycin (EM), and oleandomycin (OL), and the 16-membered macrolide mycinamicin (MCM) and STG-B]. The sequence of the N-terminal amino acid residues of a 63 kDa protein (MsrSA) that appeared in the membrane of PMS-resistant strains was identical to that of an MsrA polypeptide related to enhanced efflux of [14C]EM. Ribosomes from PMS-resistant strains showed a similar affinity for EM to those from the PMS-sensitive host strain NCTC8325, and no inactivation of EM by 8325(pEP2104) was observed. In the present study, I showed the DNA sequence of the msrSA region on the constitutive PMS-resistant plasmid pMC38, PMS-inducible resistant plasmid pEP2104 and PMS-sensitive mutant plasmid pSP6, and the region that is essential for inducible expression in PMS resistance. In addition, I investigated the relationship between PMS resistance and intracellular accumulation of EM.     

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.     

Epidemiological survey of bacterial resistance in upper respiratory tract infections in italy

The vast majority of infections in the upper airways are caused by four bacterial species;, in Italy as elsewhere, antibiotics resistant strains are emerging. Enzymatic resistance to beta-lactams in Haemophilus influenzae is becoming more important and affects 15% of isolates. On the other hand less than 0.3% of H. influenzae strains are fluoroquinolone-resistant. The number of beta-lactamase-producing Moraxella catarrhalis strains in Italy has been thought to be lower than in other countries, but recent studies suggest 90% of strains are positive, a figure similar to figures reported in the international literature. The most recent data estimate high-level resistance to penicillin in pneumococci to be around 5%, but varies greatly in different geographical areas and with the different origins of the isolates. In spite of the low incidence of penicillin-resistant strains, the most recent figures for macrolide-resistance in Streptococcus pneumoniae range from 26.4 to 31.7%. More than 3 years after the dramatic increase in erythromycin-resistant Streptococcus pyogenes, the resistance levels in Italy are still among the highest in the world. Unlike the experience in other countries, resistance is often related not to the active efflux of antibiotic from the bacterial cell but to ribosomal methylation, thus affecting not only 14- and 15-membered macrolides, but also 16-membered compounds and lincosamides.     

Appraisal of rokitamycin in the pediatric field

In a study of rokitamycin (RKM) dry syrup for its usefulness in pediatric infections, the following results were obtained: 1. Frequencies of RKM-resistant strains among fresh isolates from sick children were very low, and 4.4% of 68 isolates of Staphylococcus aureus, 4.2% of 48 isolates of Streptococcus pneumoniae, and none of 96 isolates of Streptococcus pyogenes were found to be RKM-resistant. 2. Hypo- to achlorhydria was found in 2 (3.77%) of 53 children. 3. When children were administered once orally with 5, 10 and 15 mg/kg of RKM dry syrup at fasting, mean peak values of plasma concentration were 0.25, 0.55 and 0.74 micrograms/ml with a T1/2 (beta) of 2.18, 1.97 and 2.00 hours, respectively. Urinary recovery rates during the first 0-6 hours were quite low, and values were 1.21, 1.38 and 2.23%, respectively. 4. The clinical efficacy of RKM dry syrup was studied on children chiefly with acute pneumonia, mycoplasmal pneumonia and tonsillitis. Among 379 children from whom pathogens had been determined, responses to the treatment were excellent in 186, good in 144, fair in 24, poor in 20 and unknown in 5 patients, the overall efficacy rate being 88.2%. Among all 598 treated patients, including those with undetermined pathogens, responses were excellent in 247, good in 269, fair in 42, poor in 35 and unknown in 5 patients, the efficacy rate being 87.0%. 5. The clinical efficacy of the drug in treating Chlamydia infection in 12 patients including a Chlamydia carrier and the clinical efficacy in treating Campylobacter enteritis in 36 patients were studied. All the cases showed "good" responses. Among 66 patients with mycoplasmal pneumonia, responses were excellent in 33 and good in 27 patients, with an efficacy rate of 90.9%. 6. The optimal dose of RKM dry syrup seemed to be in the range between 20 and 40 mg/kg. It appeared, however, that a dose of about 40 mg/kg would be required to eradicate the pathogen from the pharynx in S. pyogenes infection. 7. Adverse reactions to RKM dry syrup were found in 9 (1.45%) of 622 patients. The reactions were gastrointestinal symptoms except eruption occurred in 1 patient, but they were all mild. Laboratory examinations revealed eosinophilia in 19 and abnormal hepatic enzyme activities in 8 of 455 patients studied, but such abnormalities were all transient and mild.     

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)     

Laboratory and clinical studies of rokitamycin in pediatric fields

We have carried out laboratory and clinical studies on rokitamycin (RKM, TMS-19-Q). The results are summarized as follows. Serum and urinary concentrations of RKM were determined in 6 children with ages between 6 and 12 years given single oral doses of 5, 10 and 15 mg/kg. Mean serum concentrations peaked at 30 minutes after administration of 5, 10 and 15 mg/kg, and respective peak values were 0.30 microgram/ml, 0.79 microgram/ml and 1.32 micrograms/ml. Biological half-lives for 5, 10 and 15 mg/kg were 2.0 hours, 1.65 hours and 1.36 hours. The 6-hour urinary recovery ranged from 1.11% to 2.58% after administration of 5 mg/kg, and the mean 6-hour urinary recoveries were 1.35% after administration of 10 mg/kg and 2.28% after administration of 15 mg/kg. Therapeutic responses were recorded as excellent or good in 22 (73.3%) of the children, comprising 6 with tonsillitis, 2 with pharyngitis, 4 with bronchitis, 1 with bronchopneumonia, 1 with Mycoplasma pneumonia, 2 with whooping cough, 5 with streptococcal infections, 5 with Campylobacter enteritis, 3 with impetigo and 1 with SSSS. The microbiological effectiveness of RKM on identified pathogens comprising 4 strains of Staphylococcus aureus, 1 strain of Streptococcus pneumoniae, 6 strains of Streptococcus pyogenes, 4 strains of Haemophilus influenzae and 5 strains of Campylobacter spp. was not so satisfactory as evidenced by a eradication rate of 50.0%. No significant side effect due to the drug was observed in any cases. In conclusion, RKM was found to be efficacious and safe for the treatment of bacterial infections in children.     

Clinical study on clarithromycin granule and tablet in the field of pediatrics

A newly developed macrolide clarithromycin (TE-031, A-56268), with antibacterial spectrum and antibacterial activity nearly equal to those of erythromycin (EM), shows beneficial characteristics such as a higher blood level, higher recovery rate in urine, and better penetration into each tissue than conventional macrolides (MLs). TE-031 has been studied in adults against various infections and proved to be useful. The present paper describes the results of a study in children to examine the usefulness of TE-031 granules and tablets with a potency of 50 mg. TE-031 granules were administered to 132 children with ages from 6 months to 13 years and 10 months. Excluded from the evaluation were 12 cases in which clinical effects were deemed unevaluable. The evaluable subjects consisted of 1 case with pharyngitis, 3 with tonsillitis, 9 with acute bronchitis, 19 with pneumonia, 19 with mycoplasmal pneumonia, 2 with scarlet fever, 20 with Campylobacter enteritis, 11 with impetigo, 2 with subcutaneous abscess, 18 with primary atypical pneumonia and 16 with acute enteritis of unidentified pathogens; a total of 120 subjects. An average daily dose of TE-031 was 25.9 mg/kg, divided into 3 doses except 1 case with 2 daily doses and lengths of the treatment averaged 7 days. TE-031 tablets each containing 50 mg potency, were administered to 49 subjects with ages from 3 year and a month to 14 years consisting of 8 cases with pharyngitis, 1 with tonsillitis, 1 with acute bronchitis, 4 with pneumonia, 14 with mycoplasmal pneumonia, 4 with scarlet fever, 5 with Campylobacter enteritis, 7 with impetigo, 1 with atypical pneumonia, 1 with Salmonella gastroenteritis and 3 with acute enteritis caused by unidentified pathogens, at an average daily dose of 13.5 mg/kg dived into 2-4 doses (2 doses/day for 12 cases, 3 doses for 32, 4 doses for 5) for 7 days on the average. In addition to examine the clinical and bacteriological effects of the 2 dosage forms of TE-031, minimum inhibitory concentrations (MICs) were determined for 9 antibiotics consisting of 5 MLs including TE-031, EM, josamycin (JM), midecamycin acetate (MDM acetate), and rokitamycin (RKM), 3 penicillins including ampicillin (ABPC), methicillin, cloxacillin and 1 cephem antibiotic, cefaclor (CCL), against 29 strains consisting of 12 strains of Staphylococcus aureus, 7 of Streptococcus pyogenes, 2 of Streptococcus pneumonia 2 of Haemophilus influenzae and 6 of Campylobacter jejuni, out of 71 strains of pathogens or possible pathogens that had been isolated from the cases given TE-031.     

Urinary tract infections in South Croatia: aetiology and antimicrobial resistance

The aim of this study was to determine the distribution of uropathogens isolated from outpatients living in South Croatia and the in vitro susceptibility of these organisms to antimicrobial agents. Of 5080 enrolled uropathogen isolates, 82.28% isolates were Gram-negative, the most frequent isolates being Escherichia coli (62.62%), enterococci (10.18%), Proteus mirabilis (5.31%), Streptococcus agalactiae (3.84%), Staphylococcus spp. (3.70%), Pseudomonas spp. (3.46%), Klebsiella spp. (2.38%). The E. coli resistance rate was 42.17% to amoxycillin, 20.59% to trimethoprim-sulphamethoxazole and 6.09% to norfloxacin. Almost all Klebsiella spp. isolates were resistant to amoxycillin and the resistance rate to trimethoprim-sulphamethoxazole was over 20%, and 14.15% to the fluoroquinolones. A high methicillin-resistance rate was found among S. aureus (61.22%) and coagulase negative staphylococci (41.48).     

Novel antibacterial activity of monolaurin compared with conventional antibiotics against organisms from skin infections: an in vitro study

OBJECTIVE: A cross-sectional laboratory study to determine the in vitro sensitivity and resistance of organisms in culture isolates from skin infections and mechanisms of action of monolaurin, a coconut lauric acid derivative, compared with 6 common antibiotics: penicillin, oxacillin, fusidic acid, mupirocin, erythromycin, and vancomycin. METHODS: Skin culture samples were taken from newborn to 18-year-old pediatric patients with primary and secondarily infected dermatoses. Samples were collected and identified following standard guidelines, then sent to the laboratory for sensitivity testing against the 6 selected antibiotics and monolaurin. RESULTS: Sensitivity rates of Gram-positive Staphylococcus aureus, Streptococcus spp., and coagulase-negative Staphylococcus, Gram-negative E. vulneris, Enterobacter spp., and Enterococcus spp. to 20 mg/ml monolaurin was 100% and of Klebsiella rhinoscleromatis was 92.31%. Escherichia coli had progressively less dense colony growths at increasing monolaurin concentrations, and at 20 mg/ml was less dense than the control. Staphylococcus aureus, coagulase-negative Staphylococcus, and Streptococcus spp. did not exhibit any resistance to monolaurin and had statistically significant (P <.05) differences in resistance rates to these antibiotics. CONCLUSIONS: Monolaurin has statistically significant in vitro broad-spectrum sensitivity against Gram-positive and Gram-negative bacterial isolates from superficial skin infections. Most of the bacteria did not exhibit resistance to it. Monolaurin needs further pharmacokinetic studies to better understand its novel mechanisms of action, toxicity, drug interactions, and proper dosing in order to proceed to in vivo clinical studies.     

New antibacterial agents derived from the DNA gyrase inhibitor cyclothialidine

Cyclothialidine (1, Ro 09-1437) is a potent DNA gyrase inhibitor that was isolated from Streptomyces filipinensis NR0484 and is a member of a new family of natural products. It acts by competitively inhibiting the ATPase activity exerted by the B subunit of DNA gyrase but barely exhibits any growth inhibitory activity against intact bacterial cells, presumably due to insufficient permeation of the cytoplasmic membrane. To explore the antibacterial potential of 1, we developed a flexible synthetic route allowing for the systematic modification of its structure. From a first set of analogues, structure-activity relationships (SAR) were established for different substitution patterns, and the 14-hydroxylated, bicyclic core (X) of 1 seemed to be the structural prerequisite for DNA gyrase inhibitory activity. The variation of the lactone ring size, however, revealed that activity can be found among 11- to 16-membered lactones, and even seco-analogues were shown to maintain some enzyme inhibitory properties, thereby reducing the minimal structural requirements to a rather simple, hydroxylated benzyl sulfide (XI). On the basis of these "minimal structures" a modification program afforded a number of inhibitors that showed in vitro activity against Gram-positive bacteria. The best activities were displayed by 14-membered lactones, and representatives of this subclass exhibit excellent and broad in vitro antibacterial activity against Gram-positive pathogens, including Staphylococcus aureus, Streptococcus pyogenes, and Enterococcus faecalis, and overcome resistance against clinically used drugs. By improving the pharmacokinetic properties of the most active compounds (94, 97), in particular by lowering their lipophilic properties, we were able to identify congeners of cyclothialidine (1) that showed efficacy in vivo.     

Patterns of isolation of common gram positive bacterial pathogens and their susceptibilities to antimicrobial agents in Jimma Hospital

Gram positive bacteria are frequently emerging as antibiotic resistant pathogens, causing serious infections than ever before in the ill and debilitated patients. The pattern of isolation and the antimicrobial susceptibilities of common Gram positive cocci including Staphylococcus aureus, coagulase negative staphylococcus (CoNS), Streptococcus pyogenes, Enterococcus species and Streptococcus pneumoniae was investigated between January 1997 and June 2000 in Jimma Hospital. Of the 500 specimens collected from children and adults, 116 (23.2%) consisted of one or more of the above organisms. The following strains: Staphylococcus aureus, 47 (40.5%), CoNS, 36 (31.0%), Streptococcus pneumoniae, 26 (22.4%) Streptococcus pyogenes, 5 (4.3%) and Streptococcus faecalis, 2(1.7%) were isolated from different specimens including pus, sputum, urine, stool, blood and oro/nasopharyngeal swabs of patients. The in vitro activities of 14 different antibiotics including penicillin G, ampicillin, cloxacillin, cephalothin, gentamicin, kanamycin, tetracycline, chloramphenicol, erythromycin, trimethoprim-sulfamethoxazole, streptomycin, methicillin, vancomycin and clindamycin was determined against the clinical bacterial isolates. The antimicrobial activities were evaluated by agar diffusion technique using Mueller-Hinton agar according to NCCLS recommendations. The majority of the pathogens, 59(50.9%) were recovered from upper respiratory tract infections and 17 (14.6%) from the lower respiratory tract. The resistance patterns of S. aureus, CoNS, S. pneumoniae and enterococci to penicillin was 91.5%, 94.4%, 7.7% and 100% respectively. Penicillin, ampicillin and cloxacillin showed low effects (< 60%) on both S. aureus and CoNS. Multi-drug resistance was observed in all the gram-positive isolates, especially higher in staphylococcus species. All isolates of S. aureus (100%) were susceptible to vancomycin, clindamycin and gentamicin. In order to reduce morbidity and mortality due to antibiotic resistance susceptibility testing should be performed for the proper management of bacterial infections. This entails the need for national surveillance to monitor antibiotic resistance in bacteria by susceptibility testing using reliable methods.     

The post-antibiotic effects of rokitamycin (a 16-membered ring macrolide) on susceptible and erythromycin-resistant strains of Streptococcus pyogenes

The post-antibiotic effects (PAEs) on susceptible and erythromycin-resistant strains of Streptococcus pyogenes (M phenotype and inducibly resistant) of rokitamycin and erythromycin were investigated in vitro using microbiological impedance measurement. Exposure of susceptible S. pyogenes strains to 1/4, 1/2, 1 and 2 MIC erythromycin and rokitamycin resulted in PAEs of rokitamycin in the same order of magnitude as those of erythromycin and that were dose dependent. The duration of rokitamycin PAEs in erythromycin-resistant S. pyogenes strains (M phenotype and those with inducible resistance) were comparable with those observed in susceptible strains. This was not the case for erythromycin. The investigation showed that a 16-membered ring macrolide such as rokitamycin has different PAEs from those of a 14-membered ring macrolide such as erythromycin. They also indicated that, as the PAEs of rokitamycin on the M phenotype and inducible resistant strains were comparable with those on susceptible strains, no re-evaluation of therapeutic dosing regimens was required.