Rokitamycin Research Articles

Rokitamycin uptake by alveolar macrophages.

The ability of antibiotics to enter cells, especially phagocytic cells, may be an important factor affecting therapy for infections caused by organisms which survive and proliferate intracellularly. It is well known that macrolides and clindamycin have high intracellular penetration ability. We studied the uptake of rokitamycin (RKM), a new oral macrolide, using rabbit alveolar macrophages and 2 other macrolides for comparison. Intracellular concentrations of erythromycin and josamycin were, respectively, approximately 20 and 40 times higher than extracellular concentrations when they were incubated at an initial extracellular concentration of 5 micrograms/ml (I/E = 20.1 +/- 2.6, 40.8 +/- 7.4). In comparison to these 2 macrolides, the uptake of RKM was massive and very rapid. The cellular concentration of RKM was approximately 120 times higher than the extracellular concentration. Uptake of the 3 macrolides by rabbit alveolar macrophages at 4 degrees C was approximately 10% of that at 37 degrees C. This study demonstrated that RKM was rapidly and massively accumulated by alveolar macrophages, and that the drug accumulation depends on temperature. These observations suggest that RKM therapy may be very effective for the treatment of some infectious diseases.

Influence of Chitosan Glutamate on the in vivo Intranasal Absorption of Rokitamycin from Microspheres

Intranasal delivery is an alternative method to target therapeutics to the central nervous system. In the present study, chitosan glutamate (CG)-based mucoadhesive microspheres containing rokitamycin (RK) were prepared by spray-drying and in vitro characterization. Moreover, the influence of CG on RK absorption in bloodstream and cerebrospinal fluid (CSF) was evaluated after nasal administration to rats. The in vivo results were compared with those obtained after nasal administration of chitosan (CH)-based microparticles containing RK and after intravenous (IV) administration of the free drug. The in vitro results indicate that the concentrations of feed solution or kind of CH influence the RK entrapment and size of microspheres. All formulations increase the solubility of this poorly water-soluble drug, but CG is more able to increase the in vitro dissolution rate of RK than CH. CG microspheres absorb water quickly and then dissolve, whereas CH particles need more volume of water for swelling and gelling. In vivo studies showed that, after IV administration, RK is not able to cross the blood-brain barrier and to reach the CSF from the bloodstream. On the contrary, drug goes to the CSF and the bloodstream only after nasal administration of CG microparticles.

Sinergismo in vitro tra rokitamicina e cotrimossazolo in S. pyogenes e S. pneumoniae

Background: Synergism between cotrimoxazole (SXT) and rokitamycin (ROK) was observed carrying out antimicrobial susceptibility tests on S. pyogenes and S. pneumoniae with the disk diffusion method (CLSI, 2005). The aim of this study was to confirm this phenomenon on a large number of isolates displaying different macrolide resistance phenotypes. Methods: Synergism between SXT and ROK on 104 S. pyogenes and 102 S. pneumoniae recently isolated was detected by a double-disk screening test.Time kill experiments were also performed on representative strains adopting standard procedures (CLSI 2005). Results: The combination of SXT plus ROK was synergistic against 93% S. pyogenes strains and 51% S. pneumoniae strains. On pneumococci SXT-S this percentage arise to 64%, while, on SXT-R it was 29%. In no instances antagonism was demonstrated. Synergism was not observed against S. pyogenes strains showing cMLSB phenotype. In S. pneumoniae no relationship between different mechanisms of macrolide resistance and the results of interactions was found. Results of time-kill experiments confirmed those obtained with double-disk assay in all the strains tested. Conclusion: Synergism between SXT and ROK was more frequently encountered among S. pyogenes than S. pneumoniae strains.This drug association may be synergistic or not when acting on different strains of the same bacterial species. Different macrolide-resistance mechanisms (reduced binding due to modification of the 50S subunit or efflux pump) among the various bacteria may eplain the observed differences.

P736 In vitro synergism between rokitamycin and cotrimoxazole against S. pyogenes and S. pneumoniae

P736 In vitro synergism between rokitamycin and cotrimoxazole against S. pyogenes and S. pneumoniae

In Vitro and In Vivo Antibacterial Activities of the Tricyclic Ketolide TE-802 and Its Analogs

The in vitro and in vivo antibacterial activities of tricyclic ketolides (TKs: TE-802, TE-806, TE-935, TE-943) have been compared with those of clarithromycin (CAM), azithromycin (AZM) and rokitamycin (RKM). TKs were active against not only erythromycin (EM)-susceptible organisms; aerobic gram-positive bacteria, some gram-negative bacteria, anaerobic bacteria and Mycoplasma pneumoniae, but also EM-resistant Staphylococcus aureus (inducible macrolide-resistant strains) as well as EM-resistant Streptococcus pneumoniae (efflux-resistant strains). The therapeutic efficacies of TKs against systemic infections and respiratory tract infection (RTI) caused by gram-positive bacteria in mice are superior to those of CAM and AZM. The peak plasma levels (Cmax, p.o.) of TE-802 in mice were equal to that of CAM, but the plasma area under the concentration-time curve (AUC(24 hours)) was 4.7 times that for CAM. The plasma Cmax (p.o.) value for TE-802 in monkey was equal to that of CAM, whereas the AUC(8 hours) value was three-fourths that of CAM. The pharmacokinetics of TE-802 are similar to those of AZM in mice and monkeys, suggesting the potential for once-daily administration in humans.

Treatment with rokitamycin suppresses the lethality in a murine model of Escherichia coli O157:H7 infection

The effects of rokitamycin (ROK) and levofloxacin (LEVX) were investigated in a murine model of enterohaemorrhagic Escherichia coli (EHEC) infection. After C3H/HeN mice were inoculated intragastrically with E. coli O157:H7, ROK (20mg/kg) or LEVX (1.2 mg/kg) was administered intragastrically. The death rate of the mice was noted and the faeces were collected to determine viable cell counts of EHEC and for Shiga-like toxins (SLTs) assays. After the mice were sacrificed, the kidneys and colons of some of the mice were removed for histopathological examination. The death rate of mice administered ROK (19%) was significantly lower than that of the control and LEVX-treated groups (80, 93%, respectively). Viable cell counts of EHEC in the faeces of the control and ROK-treated groups were 10 7 and 10 6 CFU/g at day 5 after the infection, respectively. LEVX reduced the bacterial count by less than 100 CFU/g at day 5. The level of SLTs in the faeces from the ROK group were lower than the LEVX-treated and control groups at day 5. The histopathological findings in the kidneys treated with LEVX showed necrotic tubular epithelial cells and those in the colon, inflammatory infiltrates. These were not seen in the ROK-treated group. These results suggested that ROK suppressed release of SLTs from the EHEC and could be useful in the treatment of EHEC infection.

Macrolide antibiotics directly reduce active oxygen generation by neutrophils in human peripheral blood.

Since a "low-dose and long-term" administration of erythromycin (EM) was reported to be effective in patients with chronic respiratory diseases, including diffuse panbronchiolitis (DPB), the modulation of host defense responses by EM has attracted much attention. Despite considerable controversy, it was recently demonstrated that macrolides reduced neutrophil function. In this study, we investigated the effects of EM, a 14-membered ring macrolide, azithromycin (AZM), a 15-membered ring macrolide, and rokitamycin (RKM), a 16-membered ring macrolide, on neutrophil function in terms of active oxygen generation of neutrophils in the absence and presence of mononuclear cells in vitro. EM and AZM significantly suppressed active oxygen generation by neutrophils in the absence of mononuclear cells at low concentration (0.5 microgram/ml. p < 0.05). At the next step, to confirm that EM and AZM directly reduced active oxygen generation by neutrophils, we investigated whether mononuclear cells affected this effect of EM and AZM. In the presence of mononuclear cells pretreated with EM or AZM, both antibiotics suppressed active oxygen generation at concentrations ranging from 0.5 to 20 micrograms/ml. However, the inhibition rates induced by EM and AZM at low concentrations were not so different between the absence and the presence of mononuclear cells. These results indicated that EM and AZM have direct effects on the active oxygen generation by neutrophils and those effects that were not influenced by mononuclear cells. This inhibitory effect may be responsible for the therapeutic efficacy of these 14-membered and 15-membered ring macrolides in patients with DPB.

Macrolides and clindamycin suppress the release of Shiga-like toxins from Escherichia coli O157:H7 in vitro

We investigated the effects of antimicrobial agents fosfomycin (FOS), cefdinir (CDIN), levofloxacin (LEVX), rokitamycin (ROK), roxithromycin (ROX), and clindamycin (CLI) on the release of Shiga-like toxins (SLTs) by enterohaemorrhagic Escherichia coli (EHEC). EHEC was cultured for 14 h in the presence of ROX, ROK or CLI at sub-minimum inhibitory concentrations (subMICs) of 1.56–6.25 mg/l, followed by assay of the level of SLTs in the supernatants using cytotoxicity assay and reversed passive latex agglutination method. Exposure to ROX, ROK or CLI reduced the amount of released SLTs compared with untreated control cultures ( P<0.05). These agents however, did not decrease the number of viable EHEC, indicating the importance of bactericidal agents. When the bacteria was exposed to CDIN, FOS or LEVX, the level of SLTs in the culture supernatant increased with the destruction of bacterial cells in the order of CDIN, FOS, LEVX. When 0.5 mg/l of LEVX was added to cultures with or without pretreatment using ROX, ROK, or CLI, the release of SLTs was reduced by this pretreatment ( P<0.05). These results may have clinical implications for the treatment of EHEC infection.

慢性副鼻腔炎に対するロキタマイシン療法

Fifty patients with chronic sinusitis were treated with rokitamycin (RKM), a 16-member macrolide, for durations ranging from 2 to 12 weeks. Improvement in both subjective symptoms and objective findings increased with the progress of the treatment. After 12 weeks of treatment, the improvement rates for 5 subjective symptoms ranged between 56.5-85.7%, and the rates for 5objective findings ranged between 56.3-77.8%, the overall efficacy rate was 52.8%. The average efficacy rate on the final day of observation was 50.0%, and the rate for patients who had 3 or more of the symptoms at the start of the treatment was 53.8% on the final day of observation. The rates of improvement on the radiographic findings were 59.4%-66.7% for the maxillary sinuses and 64.3-70.0% for the ethmoidal sinuses. With regard to safety, there were 6 cases of abnormal laboratory data, including 4 cases of abnormal hepatic function and 1 case each of elevated amylase and occult blood in the urine. It was concluded from these results that RKM therapy is as useful as other 14member macrolides in the treatment of chronic sinusitis.

Phagocytosis and Intracellular Killing of Rokitamycin-Exposed Staphylococci by Human Polymorphonuclear Leukocytes

The exposure of bacteria to antibiotics at even sub-minimum inhibitory concentrations (sub-MICs) induces physicochemical and biochemical modifications that facilitate phagocytosis and intracellular killing by polymorphonuclear leukocytes (PMNs). These PMN functions were investigated by exposing Staphylococcus aureus strains to different sub-MICs (¹/₂ to ¹/₃₂ MIC) of rokitamycin (RKM). Although phagocytosis and the index of phagocytosis of the antibiotic-exposed staphylococci were not significantly modified with respect to controls, the percentage of killing significantly increased after exposure to ¹/₂ and ¹/₄ MIC by 31 and 22%, respectively. Taking into consideration the other aspect of a possible direct interaction between RKM and PMNs, it was observed that up to 10 µg/ml of RKM did not interfere with phagocytosis but significantly enhanced killing activity by up to 33%. This effect can be correlated with the high uptake of RKM by PMNs (cellular/extracellular ratio ≃30.5). The relevance of these in vitro observations to clinical situations remains to be further investigated.

Effects of Rokitamycin on Phagocytosis and Release of Oxidant Radicals of Human Polymorphonuclear Leukocytes

A rational choice of an antimicrobial agent must take into account not only the activity against the specific pathogen but also any possible negative or positive effects on the host defense system. Rokitamycin (RKM) is an orally active 16-membered-ring macrolide; there are no reports of specific investigations of these activities in the literature. Polymorphonuclear neutrophils (PMNs) from healthy adult donors were incubated in medium alone or in medium containing increasing concentrations (1, 10, 50, 100 micrograms/ml) of RKM. In unwashed PMNs phagocytosis was unaffected by RKM, while luminol-amplified chemiluminescence (LACL) was significantly reduced by 50 and 100 micrograms/ml. When PMNs were washed after incubation phagocytosis was not modified but LACL was significantly restored. These characteristics of RKM were similar to those of roxithromycin and can be put in correlation with the cellular/extracellular ratio (30.5 for PMNs and 120 for macrophages) that was similar to that of roxithromycin but higher than of other macrolides. The molecular mechanisms by which high concentrations of these two macrolides produce such an impairment of LACL are still unclear. RKM has no unwanted effects on PMNs because the serum concentrations that can be obtained with the highest doses administered to man are lower than the concentrations which did not affect PMN functions in our study.

Macrolides reduce the expression of surface Mac-1 molecule on neutrophil.

Several reports described a favorable effect of "low-dose and long-term" erythromycin (EM) on chronic obstructive pulmonary diseases including diffuse panbronchiolitis (DPB), although its mechanism still remains obscure. We investigated the effect of some macrolides, erythromycin (EM), rokitamycin (RKM), midecamycin (MDM) on the expression of neutrophil adhesion molecule Mac-1 using LPS-stimulated human whole blood as an experimental vivo model. Samples from six healthy volunteer were treated with various concentrations (0.02 ug/ml-20 ug/ml) of EM, RKM and MDM for 1 to 3 hs. Surface expression of Mac-1 antigen was determined by use of flow-cytometry. When pretreated with EM and MDM for 1 and 3 hs, significant reduction in Mac-1 expression was observed, but with RKM no substantial reduction. These findings indicate that some macrolides such as EM suppress the surface expression of Mac-1 on neutrophil and may alleviate local alveolar injury in chronic pulmonary diseases.

マクロライド系抗生物質の好中球機能に対する影響

Since "small-dose and long-term" administration of erythromycin (EM) was shown to be efficacious in the treatment of chronic respiratory disease, the modulation of host defense responses by EM has attracted much attention. Although there is considerable controversy, it was recently demonstrated that EM activity reduces neutrophil function. In this study, we investigated the in vitro effects of the macrolides erythromycin (EM), a 14-membered ring, azithromycin (AZM), a 15-membered ring and rokitamycin (RKM), a 16-membered ring macrolide, on neutrophil function. The DCFH-DA method and cytochrome C method were used for assay of active oxygen generation and the Boyden-chamber method was used for assay of chemotaxis. EM and AZM, both of which have been shown to be clinically effective in the treatment of Diffuse panbronchiolitis (DPB), significantly suppressed active oxygen generation and chemotaxis of neutrophils at low concentrations equivalent to therapeutic doses (0.5 approximately 1.0 microgram/ml, p < 0.05), whereas the clinically ineffective RKM did not. The in vitro inhibitory effects of EM and AZM on active oxygen generation and chemotaxis of neutrophils demonstrated in the present study may be responsible for the therapeutic efficacy of these 14-membered and 15-membered ring macrolides in the treatment of DPB patients.

In vitro and in vivo antibacterial activities of clarithromycin.

The in vitro and in vivo antibacterial activities of clarithromycin (CAM), a new oral macrolide antibiotic, were compared with those of erythromycin (EM), josamycin (JM) and rokitamycin (RKM). The antibacterial spectrum and in vitro activities of CAM were similar to those of EM. Therapeutic efficacies of CAM against various experimental infections in mice--including systemic infections caused by gram-positive bacteria such as Staphylococcus aureus, Streptococcus pyogenes and Streptococcus pneumoniae, and subcutaneous abscess due to S. aureus, and bacterial pneumonia caused by S. pneumoniae--were superior to those of EM, JM and RKM. CAM exhibited higher serum levels than EM in mice after a single oral dose of 50 mg/kg.

A quantitative determination of inducibility by 14 membered ring macrolide antibiotics in inducible resistant Staphylococcus aureus to macrolide-lincosamide-streptogramin B antibiotics

Using Staphylococcus aureus ISP447 strain, which shows inducible resistance to macrolide-lincosamide-streptogramin B (MLS) antibiotics, the extent of MLS-resistance induced by several macrolide antibiotics [erythromycin (EM), oleandomycin (OL), or roxithromycin (RXM)] was determined in terms of a relative ratio of a growth rate of the induced cells in the presence of a challenging drug, rokitamycin (RKM), to that of uninduced cells in the absence of RKM. The ratio was referred to as a relative inducibility (%). The inducibility was obtained at an optimum-induced condition by considering the following factors: (1) exponentially growing cells, (2) the optimum concentration of an inducer drug, i.e., 50, 150, and 150 ng/ml for EM, OL, and RXM, respectively, (3) a 3-h previous incubation at 37 degrees C in the presence of the inducer, and (4) 300 ng of RKM/ml, which is found to be optimum for induced cells to challenge, because of having no inducer activity. Using these qualification methods, inducibilities of EM, OL, and RXM as an inducer were 100.4, 27.9 and 81.1%, respectively. This method is allowed to be useful for the analysis of a structure-inducibility relationship.

Labile 50S ribosome from partial macrolide-resistant Staphylococcus aureus.

Staphylococcus aureus S704 and 8325MMT7 show constitutive resistance to macrolide antibiotics such as erythromycin (EM), oleandomycin, spiramycin, rosamicin and josamycin, except for tylosin, rokitamycin (RKM), and mycinamicin as well as lincosamide and streptogramin type B antibiotics (PM-resistance). Whenever 70S ribosomes from either of them were dissociated into 30S and 50S subunits in a 10-28%(W/W) linear sucrose gradient, the latter subunit was further cleaved into two small apparently equal particles (about 40S). RKM could no longer bind to either of the small particles. A prior exposure of 8325MMT7's 50S subunit to RKM (except EM) did not cause cleavage in any small particles. The largest component (M.W. 33.0kDa) of 50S ribosomal proteins was absent in at least the small particles. The first finding suggests that the lability of the 50S ribosome may be responsible for PM-resistance.

カンピロバクター腸炎に対するRokitamycin (RKM, TMS-19-Q) とOfloxacinの二重盲検比較試験

The clinical efficacy, safety and usefulness of Rokitamycin (RKM), a new macrolide antibiotic, were compared with those of Ofloxacin (OFLX) for the treatment of Campylobacter enteritis by a double blind method. The daily dose level of RKM or OFLX was 600 mg. They were orally administered in three divided doses for 5 days. Of 223 cases studied, 106 cases were diagnosed as Campylobacter enteritis. Ninety cases (RKM group: 50, OFLX group: 40) except for 16 excluded or drop-out cases were analysed. There was no significant difference between the two groups in any background factors. The effectiveness and usefulness was evaluated in 88 cases (RKM group: 48, OFLX group: 40). The results obtained were as follows: 1. In a total of 82 strains of Campylobacter jejuni/coli (RKM group: 42, OFLX group: 40), the bacteriological efficacy rate of RKM (95.2%) was superior to that of OFLX (70.0%) with a significant difference (p = 0.006). 2. In 76 symptomatic patients (RKM group: 42, OFLX group: 34) on the day of the beginning of drug administration, the clinical efficacy rate was 97.6% in the RKM group and 85.3% in the OFLX group with no significant difference between the two groups. 3. In 88 evaluable patients, the global clinical efficacy rate of RKM (95.8%) was superior to that of OFLX (67.5%) with a significant difference (p = 0.001). 4. Side effect was observed in 1 (1.9%) of the 54 patients in the RKM group and none of the 44 patients in the OFLX group. Slightly abnormal laboratory findings were seen in 4 (10.8%) of the 37 patients treated with RKM and 3 (9.7%) of the 31 patients treated with OFLX, but there was no significant difference between the two groups. 5. In 88 evaluable patients, the clinical usefulness of RKM (91.7%) was superior to that of OFLX (67.5%) with a significant difference (p = 0.01). From these results, RKM is considered to be a very useful agent for the treatment of Campylobacter enteritis.

カンピロバクター腸炎に対するRokitamycin (TMS-19-Q) の臨床的検討

Rokitamycin, a newly developed macrolide, was administered to a total of 107 cases, 16 years old or more, in order to evaluate its clinical efficacy, safety and usefulness on Campylobacter enteritis. Daily dosage of 600 mg of rokitamycin was administered orally in three divided doses for 5 days. Bacteriological and clinical efficacies were judged by the attending doctors from the evaluation criteria made by the committee and from the days required for improvement of diarrhea, defervescence and so on, respectively. Antibacterial activities against the isolates were tested of rokitamycin (RKM), erythromycin (EM), josamycin (JM) and ofloxacin (OFLX). The results were as follows; 41 symptomatic patients and 5 carriers were evaluated. Clinical efficacy (n = 41) was 100% (excellent; 34.1%, good; 65.9%). Bacteriological efficacy (n = 41) was 97.6%. Eight of the 9 cases with consecutive stool cultures were free of the bacteria on and after one day of the drug administration. Clinical usefulness (n = 46) was 97.8%. Slight epigastric pain was seen in only one as a side effect. The items of abnormal laboratory findings were 4 elevated GPT and/or GOT and one increased number of WBC in 4 cases. MIC90 of RKM, EM, JM and OFLX against 41 clinical isolates of C. jejuni were 1.56, 3.13, 3.13 and 0.78 micrograms/ml, respectively. Rokitamycin was considered clinically useful to treat Campylobacter enteritis.

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Adhesive binding of rokitamycin to Staphylococcus aureus ribosomes

Rokitamycin (RKM), a ″- O-propionyl derivative of leumycin A 5, is bactericidal against staphylococci near the minimum inhibitory concentrations. RKM bound to ribosomes before hand is only slightly displaced by erythromycin or josamycin, or even by RKM itself. The adhesive binding of the RKM-ribosome complex might prove to be the lethal event for susceptible staphylococci.