Isolation and characterization of the yeast mRNA capping enzyme beta subunit gene encoding RNA 5'-triphosphatase, which is essential for cell viability

The yeast Saccharomyces cerevisiae mRNA capping enzyme is composed of two subunits of alpha (52 kDa, mRNA guanylyltransferase) and beta (80 kDa, RNA 5'-triphosphatase). We have isolated the alpha subunit gene (CEG1) by immunological screening. In this report, with the aid of partial amino acid sequences of purified yeast capping enzyme, we isolated the gene, designated CET1, encoding the S. cerevisiae capping enzyme beta subunit. Amino acid sequence analysis revealed that the gene encodes for 549 amino acids with a calculated M(r) of 61,800 which is unexpectedly smaller than the size estimated by SDS-PAGE. Gene disruption experiment showed that CET1 is essential for yeast cell growth. The purified recombinant CET1 gene product, Cet1, exhibited an RNA 5'-triphosphatase activity which specifically removed the gamma-phosphate from the triphosphate-terminated RNA substrate, but not from nucleoside triphosphates, confirming the identity of the gene. Interaction between the Cet1 and the Ceg1 was also studied by the West-Western procedure using recombinant Ceg1-[32P]GMP as probe.

Isolation of a novel human gene from the Down syndrome critical region of chromosome 21q22.2

Down syndrome is the most common birth defect, and is caused by trisomy 21. We identified a novel gene in the so-called Down syndrome critical region by means of computer-aided exon prediction and subsequent cDNA cloning. The gene, designated as DCRA (Down syndrome Critical Region gene A), consists of eight exons of 3,252 bp in total and encodes a large open reading frame of 297 amino acid residues. The open reading frame shows significant homology to Hbeta58, a mouse gene essential for embryogenesis, PEP8, a yeast homologue of Hbeta58, and an expressed sequence tag of Arabidopsis thariana, suggesting that DCRA has some important function that has been conserved during the course of evolution. DCRA is expressed in most tissues examined, including fetal and adult brain, heart, lung, liver, and kidney. The cDNA of the DCRA mouse homologue, Dcra, was also cloned. It is 2,157 bp long and has an open reading frame of 297 amino acid residues, which shows 92% identity to human DCRA. Dcra is expressed in all the embryo and adult tissues examined.

N-oxidation of irsogladine by the CYP2C subfamily in the rat, dog, monkey and man

1. The metabolism of irsogladine (ISG) was studied in hepatic microsomes from the rat, dog, monkey and man, and marked species differences were observed in N-oxidation of ISG. The rank order of the activity of the N-oxidation was shown to be man < monkey < dog < rat. 2. Anti-NADPH-P450 reductase antibody inhibited the formation of the N-oxidized metabolite of ISG (ISG-N-oxide) in hepatic microsomes from rats by 74%. Anti-CYP2C11 antibody also inhibited the formation of ISG-N-oxide in hepatic microsomes from rat by 73%, whereas anti-CYP2E1, 3A2 and 4A1 antibody did not inhibit N-oxidation. Thus, CYP2C11 in the rat is at least partially responsible for the N-oxidation of ISG in the rat. 3. Anti-CYP2C11 antibody also inhibited the formation of ISG-N-oxide in hepatic microsomes from the dog and monkey by 61 and 46% respectively. Therefore, a isoform(s) similar to CYP2C11 partially contributed to the N-oxidation of ISG in the dog and monkey. In contrast, human CYP2C9, a member of the human CYP2C subfamily, did not catalyse the N-oxidation of ISG. 4. These findings show that the marked species difference in the N-oxidation of ISG is caused by the difference in the catalytic properties of CYP2C among the species examined.

Upper gastrointestinal bleeding arising from metastatic testicular tumor

We report a young man with a testicular tumor in whom the first symptom was upper gastrointestinal bleeding. This was caused by invasion of the duodenum by a metastatic lesion in a retroperitoneal lymph node. Metastatic testicular tumor is a rare cause of upper gastrointestinal bleeding. Diagnosis was difficult because the primary lesion could not be found initially. In young men with upper gastrointestinal bleeding, the possibility of metastatic testicular tumor should be investigated.

[A case of pneumoconiosis (welder's lung) suspected to be lung cancer]

A 60-year-old man, employed as a welder for 25 years, was admitted with an abnormal shadow on chest X-ray. An ill-defined and solitary mass shadow 3 cm in diameter was subsequently detected in the left upper lung field. The mass shadow exhibited high attenuation on chest CT scan. Transbronchial lung biopsy (TBLB) revealed an organized lesion possessing a large quantity of iron. Although pneumoconiosis was suspected, the possibility of lung cancer could not be dismissed. Pneumoconiosis (welder's lung) was diagnosed after thoracotomy and examination of the resected mass. Pneumoconiosis (welder's lung) rarely presents as a solitary mass lesion.

[Trend of bacterial meningitis in children over a 14 year period (1981 through 1994) in Japan--an analysis based on studies in 27 institutions]

We observed 266 children with purulent meningitis in 27 institutions in Japan during the 14 years from 1981 on dividing these years into 3 periods, 1981-1985, 1986-1990 and 1991-1994, and studied the trend of causative organisms identified in 254 among the 266 patients. Their ages were less than 3 months after birth in 50 children and 3 months or older in 216: there were 141 boys and 125 girls. The causative organisms were H. influenzae in 134 patients and S. pneumoniae in 50, most of them being aged 3 months or older. Next to the above bacteria ranked S. agalactiae in 29 and E. coli in 12, many of the patients were aged less than 3 months. Staphylococcus spp. was found in 7 patients and about 70% of them were aged 3 months or older. L. monocytogenes was found in 4 patients and N. meningitidis in 3 and they were aged 3 months or older in both patient groups. S. pyogenes, Enterococcus spp., Peptostreptococcus spp., P. Mirabilis and Enterobacter spp. were detected each in 1 patient. The causative organism was unknown in 21 patients and there was no double infection. H. influenzae were detected in 18 patients in 1981-1985 period (36.7%), in 56 in 1986-1990 (54.9%) and in 60 in 1991-1994 (63.8%) showing an increasing tendency, but S. pneumoniae exhibited neither an increasing nor decreasing tendency. There was a decreasing tendency with S. agalactiae and E. coli, but the details were not clear because there were few patients aged less than 3 months. Although the period of coexistence of 4 main bacterial species was not made clear in this study. Listeria is considered to develop mainly in the early childhood, and we believe that the conventional way of using a cephem preparation and ampicillin combined for patients under 6 years need not be altered. However, panipenem (phonetic) is likely to be effective for insensible S. pneumoniae for the time being.

Generation of reactive oxygen species by raphidophycean phytoplankton

Chattonella marina, a raphidophycean flagellate, is one of the most toxic red tide phytoplankton and causes severe damage to fish farming. Recent studies demonstrated that Chattonella sp. generates superoxide (O2-), hydrogen peroxide (H2O2), and hydroxyl radicals (.OH), which may be responsible for the toxicity of C. marina. In this study, we found the other raphidophycean flagellates such as Heterosigma akashiwo, Olisthodiscus luteus, and Fibrocapsa japonica also produce O2- and H2O2 under normal growth condition. Among the flagellate species tested, Chattonella has the highest rates of production of O2- and H2O2 as compared on the basis of cell number. This seems to be partly due to differences in their cell sizes, since Chattonella is larger than other flagellate species. The generation of O2- by these flagellate species was also confirmed by a chemiluminescence assay by using 2-methyl-6-(p-methoxyphenyl)-3,7-dihydroimidazo[1,2-a]pyrazin++ +-3-one (MCLA). All these raphidophycean flagellates inhibited the proliferation of a marine bacterium, Vibrio alginolyticus, in a flagellates/bacteria co-culture system, and their toxic effects were suppressed by the addition of superoxide dismutase (SOD) or catalase. Our results suggest that the generation of reactive oxygen species is a common feature of raphidophycean flagellates.

New xenograft model of multiple myeloma and efficacy of a humanized antibody against human interleukin-6 receptor

A new xenograft model of multiple myeloma (MM), where growth is strongly regulated by interleukin-6 (IL-6), was established in severe combined immunodeficiency (SCID) mice. In this model, endogenous IL-6 from SCID mice was ineffective at eliciting growth of the established human MM cell line KPMM2; these cells achieved autonomous growth through their autocrine secretion of IL-6. The etiopathology in this disease model is consistent with that of human MM. When greater than 3 x 10(6) KPMM2 cells were injected intravenously (IV), tumors developed in all mice and were predominantly localized in their bone marrow. Tumors were also apparent in the lymph nodes, but absent from other organs. Immunostaining of cell surface antigen (CD38) showed that more than 40% of bone marrow cells in femur were of myeloma origin in the advanced stage of tumor progression (day 37). Histologic analysis of these mice show that bone marrow was largely occupied by plasmablastic cells and bones had developed osteolytic lesions at multiple sites. Concurrently, there was a decrease in bone density throughout the body and a significant increase in ionized plasma calcium. M-protein was detected in the serum within 10 days after transplantation, which correlated with the tumor progression. Between 30 and 40 days after the transplantation, mice presented with a rapid and severe loss of body weight, hind leg paralysis, and fatigue. Subsequently, the mice died within a week. A single IV injection of 0.2 mg humanized anti-IL-6 receptor antibody (hPM1) into mice on the day after tumor transplantation substantially suppressed the elevation of serum M-protein and development of the tumor-associated abnormalities and significantly increased in the life span of tumor-bearing mice. Our data show the usefulness of this model to analyze the pathologic role of IL-6 in MM and the efficacy of targeting the IL-6 receptor in IL-6-dependent KPMM2 cells.

Quantitative assays for hepatitis C virus in serum as predictors of the long-term response to interferon

BACKGROUND/AIMS

Interferon therapy has a beneficial effect in patients with chronic hepatitis C who have a low viral load. The aim of this study was to compare the core protein level with HCV RNA levels and to analyze whether virus quantitation predicts the efficacy of interferon therapy.

METHODS

HCV core protein level assessed by the recently developed assay was compared with HCV RNA levels measured by three different methods (Amplicor-HCV monitor, competitive RT(CRT)-PCR, and bDNA probe assay) in 352 patients with chronic hepatitis C in relation to viral serotype.

RESULTS

From 91% (320/352) to 93% (299/322) of patients with viremia were detected by Amplicor-monitor and CRT-PCR, in contrast to 60% (187/312) and 74% (191/258) by bDNA and HCV core protein assay, respectively. The HCV core protein level was positively correlated with HCV RNA levels measured by the three assays (r = 0.680 to 0.731). Serum HCV RNA and core protein levels were significantly lower in patients with serotype 2 than in those with serotype 1. Viral eradication after interferon therapy was observed in 60-70% of the patients with < 1 x 10(4) copies/ml of HCV RNA by Amplicor-monitor assay, < 2 x 10(5) copies/ml by CRT-PCR, < 0.5 Meq/ml by bDNA assay, and < 20 pg/ml of core protein by HCV core protein assay. Viral eradication was uncommon (< 11%) among the patients with higher viral loads. Bivariate analysis revealed that the outcome of interferon therapy was more closely associated with both HCV core protein and RNA levels than the HCV serotype.

CONCLUSIONS

Quantitation of HCV core protein and HCV RNA in useful for prediction of the interferon response.

Influence of ETR-p1/f1 antisense peptide on endothelin-induced constriction in rat renal arcuate arteries

1. This study set out to examine the endothelin receptor subtypes mediating vasoconstriction in the rat renal arcuate artery. This was done in isolated vessels 120-200 microns in diameter, incubated with a selective agonist and the novel 'antisense' peptide to part of the human endothelinA receptor. 2. Groups of vessels (n = 6) were incubated with increasing concentrations of endothelin-1 (ET-1), from 1 to 100 nM, which caused a 65% maximal contraction at the highest dose with an pEC50 of 8.16 +/- 0.11 M. By contrast, in six other vessels sarafotoxin 6c over the same dose range gave a minimal contraction (around 5% of maximum). 3. Preincubation of six vessels with the antisense peptide ETR p1/f1 at 1 microM had no effect on the ET-1 induced vasoconstriction, in terms of displacement of the concentration-response curve or the maximal tension achieved by the agonist. In the six vessels exposed to 4 microM ETR p1/f1, there was a significant shift of the concentration-response curve and a lower pEC50 at 7.78 +/- 0.09 M (P < 0.05). At the highest concentrations of ETR p1/f1, there was a marked suppression of all responses to ET-1, which at the maximal concentrations tested, 0.1 microM, only reached some 10% of the maximal achievable contraction. 4. Increasing ET-1 concentrations up to 2 microM in vessels incubated with 40 microM ETR-p1/f1 showed that the blockade could be overcome and that the relationship was shifted to the right (P < 0.001) by approximately one log unit with a pEC50 of 7.13 +/- 0.11 M. A Schild plot of the data indicated the antagonist to be acting competitively at a single population of receptors. 5. At the highest concentrations tested, 40 microM, ETR-p1/f1 had no effect on noradrenaline-induced contractions, indicating a lack of non-specific actions. 6. Together, these data suggest that at the rat renal arcuate artery the endothelinA receptor is the predominant functional receptor mediating contraction. Furthermore, this study has shown the potential usefulness of this novel type of 'antisense' peptide in blocking receptor activation.

Disposition of ampicillin in honeybees and hives

Disposition profile of ampicillin (ABPC) among honeybees, larvae, honey and royal jelly in a hive after oral dosing to adult bees was studied. Four honeybee colonies were administered the single dose of ABPC at the rate of 30 mg/hive by addition to sugar syrup or pollen substitute (paste) for 1 day intake. The colonies received ABPC in syrup showed high drug residue levels in honey and it lasted over 14 days beyond the detection limit of residual analysis. In the hives given ABPC in paste, relatively low honey residues were found, however, the distributions of the drug in young larvae and jelly which was the food of the larvae were very low. ABPC was considered to be a promising drug for the control of American foulbrood, an important bacterial disease of honeybee larvae, because of its high antibacterial activity to the pathogen, Paenibacillus larvae, and instability of residue in honey as human food. The low distribution in young larvae, the target of the disease, threw a doubt on the efficacy of ABPC for American foulbrood control.

Cloning of a gene encoding a putative xylanase with a cellulose-binding domain from Humicola grisea

We have isolated a genomic clone of a putative xylanase gene (xyn1) from Humicola grisea by using the DNA fragment encoding a cellulose-binding domain of H. grisea cellobiohydrolase 1 as a probe. The translation product of the xyn1 gene predicts a xylanase of 429 amino acids in length, with a cellulose-binding domain in the C-terminus.

Vocal identification of speaker and emotion activates different brain regions

Regional cerebral blood flow was measured in six healthy volunteers by positron emission tomography during identification of speaker and emotion from spoken words. The speaker identification task activated several audio-visual multimodal areas, particularly the temporal poles in both hemispheres, which may be involved in connecting vocal attributes with the visual representations of speakers. The emotion identification task activated regions in the cerebellum and the frontal lobe, suggesting a functional relationship between those regions involved in emotion. The results suggest that different anatomical structures contribute to the vocal identification of speaker and emotion.

[Combination effect of fosfomycin to beta-lactam, aminoglycoside, and macrolide antibiotics against clinical isolates of Klebsiella pneumoniae]

It is well known that fosfomycin (FOM) shows the combination effects with some other antibiotics. Suck effects have not been known against Klebsiella pneumoniae, however. In this report, combination effects of FOM with beta-lactam, aminoglycoside, and macrolide antibiotics were investigated against clinical isolates of both FOM-susceptible and resistant Klebsiella pneumoniae. FOM had synergistic activities with beta-lactams such as ampicillin (ABPC) and cefminox (CMNX), and macrolide antibiotics as erythromycin (EM) and midecamycin (MDM) against all strains tested. Among beta-lactams, penicillin V showed synergistic actions against FOM-susceptible strain of Tf341A and additive actions against FOM-resistant 3 strains with FOM. Pheneticillin was synergistic with FOM against FOM-highly susceptible strain Tf341A and the additive or nearly synergistic effects against other strains. FOM with amoxicillin was synergistic against Tf341A, and FOM-resistant strain of Tf170B and additive against other strains. While the activities of combination of FOM with kanamycin or dibekacin against FOM-susceptible 2 strains were additive, those with amikacin were synergistic. Five different aminoglycosides tested showed antagonistic activities with FOM against 3 FOM-resistant strains. From these results, FOM appears to be clinically useful in treating FOM-susceptible and resistant strains of Klebsiella pneumoniae in combination of 4 antibiotics such as ABPC, CMNX, EM, and MDM.

Predictors of the efficacy of interferon therapy in chronic hepatitis C virus infection. Tokyo-Chiba Hepatitis Research Group

BACKGROUND & AIMS

The relative role of virus load and hepatitis C virus (HCV) subtype as predictor of the efficacy of interferon (IFN) therapy is still in dispute. To resolve this issue, a multicenter, randomized, prospective study of 272 patients with chronic hepatitis C but without cirrhosis was conducted.

METHODS

The patients were randomly assigned to two different dose groups: 6 million units (MU) or 9 MU IFN three times a week for 6 months. Serum HCV RNA levels and HCV subtypes were determined.

RESULTS

HCV RNA negativity rate at the completion of treatment with 9 MU IFN was higher than that with 6 MU (75% vs. 44%; P < 0.05). Virus eradication at 12 months after completion of treatment was higher in the 9 MU group than in the 6 MU group (36% vs. 25%; P < 0.05), especially in patients who had an intermediate virus load (10(4)-10(5) copies/mL by Amplicor monitor assay) (52% vs. 19%; P = 0.029). Virus eradication rate in patients with serotype 2 was higher than in those with serotype 1 for both regimens (6 MU, 53% vs. 15%; 9 MU, 76% vs. 29%; each P < 0.05).

CONCLUSIONS

This prospective study showed that virus load, HCV serotype, and IFN dose are important predictors of the virological response to IFN therapy but virus load is the most important factor influencing the efficacy of IFN.

[Biochemical and molecular characterization of Salmonella serovar enteritidis phage type 4 isolated from food poisoning outbreaks in Tokyo]

Since 1989, outbreaks of Salmonella ser. Enteritidis (S. Enteritidis) food poisoning have dramatically increased in Tokyo, and a total of 31 outbreaks has been reported in 1989. Twenty-one of these 31 outbreaks were caused by S. Enteritidis PT34, but 8 outbreaks were caused by S. Enteritidis PT4. After 1990 instead of SE PT34, food poisoning due to PT4, which was a very common phage type in the UK, has increased in Tokyo. Between 1989 and 1995, there were 144 food poisoning outbreaks caused by S. Enteritidis, and 64 of these outbreaks were by due to S. Enteritidis PT4, which was one of the main phage types in Tokyo. To characterize these strains of phage type (PT) 4,293 isolates from patients, and vehicle foods, eggs and environment in Tokyo were examined for plasmid DNA profiles, acid productivity from glycols (propylene and ethylene) and antimicrobial resistance patterns. Plasmid DNA was extracted by Kado's method, and analyzed by agarose gel electrophoresis. The acid productivity from propylene glycol or ethylene glycol were tested using Barsicow medium with 1% propylene glycol or ethylene glycol. Antimicrobial susceptibility to AM, CP, TC, SM, KM, NA, ST, FOM and NFLX was tested by the K-B disc method. The strains of PT4 were further subdivided into 9 types by those epidemiologic marker analysis. The prevalent pattern of PT4 strains was type A plasmid profile carrying only one plasmid (60 kb) and there were 2 kinds of antibiograms. One was SM resistant, while the other was susceptible. A total of 56 (87.5%) of 64 outbreaks was found to have been caused by these types of S. Enteritidis. Several kinds of egg-related foods were suspected as the vehicles of transmission among 24 outbreaks. Especially, in 5 outbreaks, S. Enteritidis strains were isolated both from patients and suspected food which were cooked with egg. This strongly suggests that these foods may be the potential source of infection in S. Enteritidis PT4 outbreaks.

Bh (black at hatch) gene appears to be expressed in melanocytes of feather germs in the Japanese quail (Coturnix coturnix japonica)

The Bh (black at hatch) gene was examined to determine whether it is expressed in plumage melanocytes by analyzing pigmentation patterns of Bh melanocytes placed in the micro-environment of the feather germs of quail embryos with pink eyes. These host quails genetically lack a large part of plumage melanin. The Bh locus in these almost white quails is wild-type. When Bh neural crest cells were transplanted orthotopically into the host embryos, wild-type and Bh/+ melanocytes, which differentiated from the transplanted neural crest cells, formed plumage pigmentation patterns characteristic of each genotype in the micro-environment of the host feather germs. Brown plumage pigmentation, which was very similar to that of 10-day Bh/Bh embryos, was also observed in the feather germs of host embryos that received Bh neural crest cells, although the genotype of the donors could not be determined. These donors died before pigmentation of their feather germs occurred. The results demonstrate that pigmentation patterns of Bh melanocytes are not altered in the micro-environment of the host germs, suggesting that the Bh gene is autonomous in Bh melanocytes and is expressed in melanocytes of both Bh and the host feather germs, and that it causes the normal pigmentation pattern to be altered.

Risperidone in the elderly: a pharmacoepidemiologic study

BACKGROUND

The possibly limited adverse effects of risperidone encourage interest in its use in geriatric patients.

METHOD

Medical records of 122 hospitalized psychogeriatric patients (> or = 65 years old) newly treated with risperidone were reviewed and scored for indications, doses, and effects of this novel neuroleptic.

RESULTS

Subjects (83 women, 39 men), mean +/- SD age = 76.5 +/- 6.8 years (range, 65-95), were given risperidone for agitation or psychosis associated with dementia (53%), a major mood disorder (29%), or other disorders (18%). Most (77%) were also medically ill and received other psychotropic (76%) or cardiovascular agents (70%). Daily doses of risperidone averaged 1.6 +/- 1.1 mg (range, 0.25-8.0) (0.025 mg/kg body wt.); 78% received 2.0 mg. Risperidone appeared to be effective in 85% of cases, but 18% were discontinued due to intolerability (11%) or inefficacy (7%). Adverse events occurred in 32% of the patients (36% of those discontinued). These adverse events included hypotension (29%) or symptomatic orthostasis (10%), cardiac arrest (1.6%) with fatality (0.8%), and extrapyramidal effects (11%) or delirium (1.6%). Benefits were associated with younger age and male gender, but not risperidone dose. Adverse effects were associated with cardiovascular disease and its treatment, cotreatment with an SRI antidepressant or valproate, and relatively rapid dose increases.

CONCLUSION

Risperidone appeared to be effective and may be safe for many elderly psychiatric patients with comorbid medical conditions provided that doses are low and increased slowly. Particular caution is advised in the presence of cardiovascular disease or cotreatment with other psychotropic agents.

Visual evoked cortical magnetic fields to pattern reversal stimulation

We studied visual evoked magnetic fields to pattern reversal stimulation in six healthy subjects. Similar to the N75-P100-N145 components in visual evoked potentials, triphasic deflections, N75m-P100m-N145m, were clearly observed around the midoccipital position. A very small component, P50m, was occasionally observed preceding the N75m. Equivalent current dipoles (ECDs) of the main deflection, P100m, to quadrant-field stimulation were estimated near or around the calcarine fissure contralateral to the stimulation. The vertical ECD location of the P100m to the upper quadrant-field stimulation was estimated significantly lower (0.81 +/- 0.45 cm) than those to lower stimulation. These results were compatible with the retinotopic organization of the visual cortex (cruciform model) and suggested that the P100m originated in the striate cortex. The small P50m, although only a small number of ECDs could be estimated reliably, was located in the contralateral visual cortex. ECDs of the N75m were estimated mainly near or around the contralateral calcarine fissure. ECDs of the N145m were estimated also retinotopically, but with a greater vertical distance (2.90 +/- 1.09 cm) between upper and lower quadrant-field stimulation. MR-overlaid ECDs of the N145m suggested that these originated in the extrastriate cortex. No ECD was estimated when a probe was placed at the midfrontal position.

[Antimicrobial activities of roxithromycin against recently obtained clinical isolates]

The purpose of our investigation was to monitor current trends in the susceptibility patterns of clinical bacterial isolates to roxithromycin (RXM). We measured the MICs of macrolide antibiotics, such as RXM, erythromycin (EM), clarithromycin (CAM), rokitamycin (RKM) and midecamycin (MDM), and other classes of antibacterial compounds against various clinical isolates at seven institutions between October and December in 1994 and 1995. RXM had excellent antibacterial activities for S. pyogenes, S. agalactiae, M. (B.) catarrhalis and methicillin sensitive S. aureus. Against methicillin sensitive S. epidermidis, RXM activity was fairly good but about 20% of the strains had MIC > or = 128 micrograms/ml. The activity against S. pneumoniae was not so potent and similar to activities of EM, CAM, MDM, and clindamycin. The vast majority of methicillin resistant S. aureus and S. epidermidis were also resistant to macrolide antibiotics and other classes of compounds tested. In conclusion, RXM is an unique macrolide antibiotic by retaining potent activity against S. pyogenes, S. agalactiae, S. aureus except MRSA, M. (B.) catarrhalis and M. pneumoniae.