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Objectives: Solithromycin is a fluoroketolide that is considered to be a noninducing antibiotic for macrolide–lincosamide–streptogramin B resistance mediated by erm genes. The exact activity of sol...

To assess whether gene methylation in peritoneal fluid (PF) is clinically feasible for determining micrometastasis to the peritoneum in gastric cancer. The gene methylation of BNIP3, CHFR, CYP1B1, MINT25, SFRP2, and RASSF2 were analyzed in 107 specimens of PF by quantitative methylation-specific polymerase chain reaction. All patients were placed into one of 3 groups: group A (n = 42), patients with depth of cancer invasion at muscularis propria (MP) or less than MP; group B (n = 45), depth of cancer invasion beyond the MP; and group C (n = 20), histologically diagnosed peritoneal metastasis or cancer cells cytologically defined in the peritoneal cavity. Patients in both groups A and B were diagnosed as having no cancer cells by peritoneal cytology and histology. The methylation status of the 6 genes was found to be significantly different among the 3 groups (group A, 0–5%; group B, 0–15%; group C, 15–45%; P

Macrolides are a well-known family of oral antibiotics whose antibacterial spectrum of activity covers most relevant bacterial species responsible for respiratory infectious disease. In recent years, it has been reported that macrolides have not only bactericidal activity but also direct immunomodulating activity in mammals. In this study, we observed new physiological activity of macrolides and examined whether various macrolides induce apoptosis in human leukemia cell lines. We investigated the effects of 13 different macrolides on the viability of Jurkat and HL-60 cells. Among all the macrolides used in this study, rokitamycin, a semisynthetic macrolide with a 16-member ring, effectively induced cell death. Rokitamycin induced DNA fragmentation and caspase activation, resembling the progression of apoptosis. Moreover, rokitamycin reduced the mitochondrial transmembrane potential and released cytochrome c from mitochondria to the cytosol, suggesting that mitochondrial perturbation is involved in rokitamycin-induced apoptosis. These results suggest that rokitamycin possesses not only bactericidal activity but also pro-apoptotic activity in human leukemia cells. Keywords:: macrolide, rokitamycin, apoptosis, mitochondria, caspase

Inhalation of freshwater containing the free-living amoeba Naegleria fowleri leads to a potentially fatal infection known as primary amoebic meningoencephalitis (PAME). Amphotericin B is the only agent with clinical efficacy in the treatment of PAME in humans, however this drug is often associated with adverse effects on the kidney and other organs. In an attempt to select other useful therapeutic agents for treating PAME, the amoebicidal activities of antibacterial agents including clarithromycin, erythromycin, hygromycin B, neomycin, rokitamycin, roxithromycin and zeocin were examined. Results showed that the growth of amoeba was effectively inhibited by treatment with hygromycin B, rokitamycin and roxithromycin. Notably, when N. fowleri trophozoites were treated with rokitamycin, the minimal inhibitory concentration was 6.25 microg/mL on Day 2. In the treatment of experimental meningoencephalitis due to N. fowleri, survival rates of mice treated with roxithromycin and rokitamycin were 25% and 80%, respectively, over 1 month. The mean time to death for roxithromycin and rokitamycin treatment was 16.2 days and 16.8 days, respectively, compared with 11.2 days for control mice. Finally, rokitamycin showed both in vitro and in vivo therapeutic efficacy against N. fowleri and may be a candidate drug for the treatment of PAME.

Miocamycin (midecamycin acetate), an oral macrolide, has a 16-membered ring and, in vitro, a similar or greater spectrum of activity to that of erythromycin. It is active against erythromycin-resistant staphylococcal and streptococcal species that express inducible-type resistance, has rapid and extensive penetration into body tissues and fluids, a low potential for drug interactions and is well tolerated.

The present study demonstrates the in vitro effectiveness of the macrolide rokitamycin and the phenothiazine compound chlorpromazine against Acanthamoeba castellanii . Growth curve evaluations revealed that both drugs inhibit trophozoite growth in dose- and time-dependent ways. The effects of both drugs when they were used at the MICs at which 100% of isolates are inhibited were amoebistatic, but at higher doses they were amoebicidal as well as cysticidal. Experiments showed that when rokitamycin was associated with chlorpromazine or amphotericin B, rokitamycin enhanced their activities. Furthermore, low doses of rokitamycin and chlorpromazine, alone or in combination, blocked the cytopathic effect of A. castellanii against WKD cells derived from the human cornea. These results may have important significance in the development of new anti- Acanthamoeba compounds.

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.

Streptococcus pyogenes isolates with the same pulsed-field patterns were recovered from the throat cultures of a child with tonsillopharyngitis before and after treatment with miocamycin, a 16-membered macrolide. The initial isolate was macrolide-susceptible, but the isolates after the treatment were resistant to 14 and 15-membered macrolides and had two amino acid (65WR66) deletions in ribosomal protein L4.

In 1998 we conducted a multicentre study in Spain on the susceptibility of Streptococcus pyogenes isolates to different 14-, 15- and 16-membered macrolides and clindamycin, in which the number of strains examined was proportional to the number of inhabitants in each geographical area. The aim of the present work was to re-examine the antimicrobial susceptibility of S. pyogenes in 2001, using the same methodology and centres as in 1998, to determine the different susceptibility phenotypes to macrolides-lincosamides, and to compare the results from the 2 years by statistical tests. A total of 529 unique isolates of S. pyogenes, collected in 21 laboratories, were studied. Throat swabs provided 417 isolates (78.8%), and the remaining 112 were from other sources. Four hundred and thirty-five (82.2%) were isolated from children and 94 (17.8%) from adults. One hundred and fifty-seven (29.7%) of the isolates were resistant to erythromycin and azithromycin, whereas resistance to miocamycin, a 16-membered macrolide, was 1.5%. The prevalence of resistance to clindamycin was 1.3%. The majority (98.7%) of the 157 erythromycin-resistant strains presented the M phenotype. When we compared the results obtained in 1998 and 2001, we observed a statistically significant increase in resistance to erythromycin and azithromycin (P = 0.02, chi(2) test), but not to clindamycin or miocamycin (P = 0.47, chi(2) test with Yates' correction). The significant increase in the prevalence of resistance to some macrolides of S. pyogenes in Spain underscores the need for continuous surveillance of antimicrobial resistance in this species.

This study aimed to evaluate the bactericidal rates of levofloxacin, gatifloxacin, penicillin, meropenem and rokitamycin against seven isolates of Bacillus anthracis clinically isolated between 1960 and 1970. After determination of MIC and MBC, time-kill experiments were carried out. Antimicrobial activity was evaluated at concentrations equal to 1 x, 2 x, 4 x and 8 x MIC after 0, 3, 6, 12 and 24 h of incubation with the drugs. Bactericidal activity was defined as a decrease in bacterial count of at least 3 log10. All the isolates were susceptible to all the antibiotics, by considering the antistaphylococcal breakpoints. Levofloxacin was bactericidal at 1 x MIC after 24 h and at 4 x MIC after 12 h, and gatifloxacin was bactericidal at 2 x MIC after 24 h and at 8 x MIC after 12 h. Meropenem, rokitamycin and penicillin also showed bactericidal activity at concentrations of 4 x and 8 x MIC, respectively, but only after 24 h incubation; after the same time, meropenem and rokitamycin showed a more marked killing than penicillin at 2 x MIC.

This in-vitro study was designed to identify the enzyme(s) involved in the major metabolic pathway of rokitamycin, i.e. the formation of leucomycin A7, and to assess possible interactions of the drug with rat liver microsomes. Formation of leucomycin A7 was NADPH-independent and was not appreciably inhibited by anti-rat NADPH cytochrome P-450 reductase serum or cimetidine, a nonspecific inhibitor of cytochrome P-450 isoforms. Eadie-Hofstee plots for the formation of leucomycin A7 were indicative of apparently monophasic behaviour for six rat liver microsomes tested. The mean (± s.d.) kinetic parameters, Km, Vmax and Vmax/Km, for the formation of leucomycin A7 from rokitamycin were 47 ± 13 μm, 390 ± 56 nmol min−1 (mg protein)−1 and 8.6 ± 1.6 mL min−1 (mg protein)−1, respectively. Three esterase inhibitors (100 μM), bis-nitrophenylphosphate, physostigmine and metrifonate inhibited the formation of leucomycin A7 by more than 60%. Metabolism of rokitamycin was inhibited by terfenadine, but not by mequitazine, whereas chlorpheniramine and theophylline activated the formation of leucomycin A7. Rokitamycin, leucomycin A7, leucomycin V, erythromycin and clarithromycin were weak inhibitors of CYP3A-catalysed 3-hydroxylation of quinine with mean IC50 values ranging from 71 to > 100 μM. It is concluded that in rat liver microsomes the formation of leucomycin A7 from rokitamycin is catalysed mainly by an esterase (possibly cholinesterase, EC3.1.1.8), but not by cytochrome P-450 enzyme(s). Although in this in-vitro animal study CYP3A activity was barely inhibited by rokitamycin, the possibility cannot be totally discounted in man when rokitamycin is co-administered with drugs metabolized by CYP3A.

The purpose of this study was to evaluate possible interaction of nifedipine with erythromycin or rokitamycin in the intestinal mucosa. Male beagle dogs were orally administered nifedipine (10 mg), with or without oral pre-medication with erythromycin (300 mg), and 300 mg erythromycin or rokitamycin twice a day for 3 days. The experiments were of randomized cross-over design with a two-week wash-out period between dosing regimens. Erythromycin pre-medication for 3 days resulted in a significant increase in the area under the serum nifedipine concentration-time curve (AUC), whereas the curve for one nifedipine metabolite (M-2) decreased significantly. When the effects of erythromycin on the metabolism of nifedipine were studied using dog liver microsomes it was found that erythromycin significantly inhibited formation of M-2 but not of the metabolite M-1. These results indicate that formation of M-2 from M-1 in the liver might be reduced by erythromycin premedication. To avoid possible metabolism in the gut, the dogs were then administered 8 mg nifedipine into the peritoneal cavity, with or without multiple dose pre-treatment with erythromycin for 3 days. After intraperitoneal administration of nifedipine, the maximum concentration (Cmax) of nifedipine increased significantly. After pre-administration of erythromycin the relative bioavailability of nifedipine after oral administration was increased compared with injection into the peritoneal cavity. In-vitro study using rat intestinal microsomes and the in-vivo rat intestinal loop technique also showed that pre-administration of erythromycin inhibits nifedipine metabolism in the small intestine.

The effects of erythromycin, clarithromycin and rokitamycin on the metabolism of nifedipine were studied in vitro and in situ. Erythromycin, clarithromycin or rokitamycin added to nifedipine did not inhibit the formation of metabolite, M-1, of nifedipine, whereas pretreatment with erythromycin or clarithromycin significantly (p < 0.05) inhibited its formation. Only erythromycin significantly (p < 0.05) inhibited the formation of M-2 from M-1. These observations agreed with the results obtained using an in situ rat intestinal loop technique. As assessed by the concentrations of nifedipine and M-2 in jugular and portal vein blood, the inhibition of nifedipine metabolism by erythromycin was greater after multiple doses than after a single dose. Moreover, our results suggest that rokitamycin is a less potent inhibitor of nifedipine metabolism.

Introduction In Northern Sardinia, one-week triple standard therapies containing a proton-pump inhibitor and two antibiotics for H. pylori infection have an average cure rate of 57% largely due to a high prevalence of antimicrobial resistance. The efficacy of miocamycin-containing treatment for 10 days was evaluated. Materials and Methods Patients referred to the endoscopy service for dyspeptic symptoms were enrolled. H. pylori infection was defined as a positive rapid urease test, presence of the bacteria on gastric biopsies, and a positive 13C-UBT. Treatment consisted of 10 days with omeprazole 20 mg, miocamycin water-soluble 900 mg, and tinidazole 500 mg all bid. Success was evaluated 40–50 days after the end of therapy and defined by a negative 13C-UBT. Compliance was considered good if at least 90% of the total number of the pills were taken. Fluorescent in situ hybridization (FISH) technique was applied on paraffin-embedded gastric tissue sections to test susceptibility to clarithromycin of the bacteria. Results 50 patients were enrolled (mean age; 52, 36% men). Miocamycin-containing therapy cured 86% (42/49; 95% CI = 72–94%) of infected patients by PP analysis. Susceptibility data (FISH) was available for 38 patients. Cure rates for the 28 with clarithromycin-susceptible infection was 96% vs 50% for those with resistant or mixed infection, (p = .003). Good compliance was recorded in 48 patients. None of the patients discontinued therapy. Conclusions Miocamycin appears to be a valid alternative for clarithromycin for H. pylori eradication. Head-to-head studies will be needed to ascertain whether it is superior.

Macrolide antibiotics can interact adversely with commonly used drugs, usually by altering metabolism due to complex formation and inhibition of cytochrome P-450 IIIA4 (CYP3A4) in the liver and enterocytes. In addition, pharmacokinetic drug interactions with macrolides can result from their antibiotic effect on microorganisms of the enteric flora, and through enhanced gastric emptying due to a motilin-like effect. Macrolides may be classified into 3 different groups according to their affinity for CYP3A4, and thus their propensity to cause pharmacokinetic drug interactions. Troleandomycin, erythromycin and its prodrugs decrease drug metabolism and may produce drug interactions (group 1). Others, including clarithromycin, flurithromycin, midecamycin, midecamycin acetate (miocamycin; ponsinomycin), josamycin and roxithromycin (group 2) rarely cause interactions. Azithromycin, dirithromycin, rikamycin and spiramycin (group 3) do not inactivate CYP3A4 and do not engender these adverse effects. Drug interactions with carbamazepine, cyclosporin, terfenadine, astemizole and theophylline represent the most frequently encountered interactions with macrolide antibiotics. If the combination of a macrolide and one of these compounds cannot be avoided, serum concentrations of concurrently administered drugs should be monitored and patients observed for signs of toxicity. Rare interactions and those of dubious clinical importance are those with alfentanil and sufentanil, antacids and cimetidine, oral anticoagulants, bromocriptine, clozapine, oral contraceptive steroids, digoxin, disopyramide, ergot alkaloids, felodipine, glibenclamide (glyburide), levodopa/carbidopa, lovastatin, methylprednisolone, phenazone (antipyrine), phenytoin, rifabutin and rifampicin (rifampin), triazolam and midazolam, valproic acid (sodium valproate) and zidovudine.

In an open, randomized, crossover trial, the clinical efficacy and effect on total serum immunoglobulin E (IgE) levels of a macrolide—miocamycin—and of a beta-lactam—amoxicillin/clavulanate—were compared in patients with infectious exacerbations of bronchial asthma. Of the 42 patients admitted, 33 were evaluated for efficacy and tolerability of the treatments and 16 for the effect on serum IgE levels. Both treatments were effective in treating infectious exacerbations. Mild side effects (gastralgia) occurred in 19% of the miocamycin-treated patients, compared with 32% (generally, worsening of the asthma attacks) in the amoxicillin/clavulanate-treated patients. Total IgE serum levels were not affected by miocamycin, whereas they increased after treatment with amoxicillin/clavulanate (statistically significant difference). It would thus appear reasonable to prefer macrolides to beta-lactams in the treatment of asthmatic patients (at least as far as the tested drugs are concerned).

The efficacies of macrolide antibiotics, rokitamycin, leukomycin, josamycin and erythromycin were investigated against 63 strains of M. pneumoniae included FH strain which were isolated from clinical specimens obtained in 1986-1987, 1991, 1992-1993. Values of MICs and MBCs of these antibiotics were evaluated by two methods, broth dilution method and M. pneumoniae L cell infection system. In broth dilution method, MIC50 and MBC50 of rokitamycin were 0.0063-0.025 microgram/ml and 0.025-0.2 microgram/ml respectively. The ratios of MBC50/MIC50 were 1-32. MIC50 of leukomycin, josamycin and erythromycin were 0.0063-0.05 micrograms/ml, 0.0025-0.05 microgram/ml, and 0.0125-0.05 microgram/ml respectively. MBC50 of these drugs were 0.0125-50 micrograms/ml, 25-50 micrograms/ml, and 25-50 micrograms/ml respectively. The ratios of MIC50/MBC50 were 2-800, 500-2000, 500-4000. MIC50 of rokitamycin and leukomycin to the isolates during period from 1992-1993 were higher as compare to those of isolates during 1986 to 1991. On the other hand, rokitamycin markedly reduced the numbers of CFU in the growth phase when added at the concentrations of 16 and 4 times the MIC, but the other macrolides were reduced slightly CFU at the concentrations of 4 times, the MIC. In L cell infectious system, MIC50 and MBC50 of rokitamycin were 0.005-0.0125 microgram/ml and 0.05-0.1 microgram/ml respectively. The ratios of MBC50/MIC50 were 1-2 Ratios of leukomycin, josamycin, and erythromycin were 0.05-0.1 microgram/ml, 0.05-0.2 microgram/ml and 0.050-0.1 microgram/ml respectively. The MBC50 of these drugs were 0.2-0.4 micrograms/ml, 0.8-1.6 microgram/ml, 0.8-1.6 microgram/ml. Ratios of MBC50/MIC50 were 2-8, 4-32, 8-32.(ABSTRACT TRUNCATED AT 250 WORDS)

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.

The renewed interest in macrolide antibacterials with expanded indications for clinical use, as well as their markedly increased usage, justifies the continuous search for new compounds designed to offer the patient not only enhanced bioavailability but also a reduced incidence of adverse effects. Macrolides are an old and well established class of antimicrobial agents that account for 10 to 15% of the worldwide oral antibiotic market. Macrolides are considered to be one of the safest anti-infective groups in clinical use, with severe adverse reactions being rare. Newer products with improved features have recently been discovered and developed, maintaining or significantly expanding the role of macrolides in the management of infection. This review deals with the tolerability of the clinically available macrolide antibacterials. With the exception of drug interactions, adverse effects have been analysed during the last 40 years in many thousands of adult and paediatric patients. Recently developed derivatives have been compared with the older compounds, and the expected and well assessed adverse effects have been set apart from those which are unusual, very rare or questionable. Gastrointestinal reactions represent the most frequent disturbance, occurring in 15 to 20% of patients on erythromycins and in 5% or fewer patients treated with some recently developed macrolide derivatives that seldom or never induce endogenous release of motilin, such as roxithromycin, clarithromycin, dirithromycin, azithromycin and rikamycin (rokitamycin). Except for troleandomycin and some erythromycins administered at high dose and for long periods of time, the hepatotoxic potential of macrolides, which rarely or never form nitrosoalkanes, is low for josamycin, midecamycin, miocamycin, flurithromycin, clarithromycin and roxithromycin; it is negligible or absent for spiramycin, rikamycin, dirithromycin and azithromycin. Transient deafness and allergic reactions to macrolide antibacterials are highly unusual and have definitely been shown to be more common following treatment with the erythromycins than with the recently developed 14-, 15- and 16-membered macrolides. There have been case reports in the literature of 51 patients during the last 30 years who experienced uncommon or dubious adverse effects after treatment with older compounds and in which there appears to be strong evidence of a causal relationship with the drug. Only 3 cases had an unfavourable outcome, and these were patients administered erythromycin lactobionate intravenously too rapidly or at high dose. Targets of these occasional reactions are generally the heart, liver and central nervous system. Other unusual organ pathologies are related to immunomediated disorders more than to primary parenchymal toxicity, or to the rarely serious consequences of macrolide-induced alterations in intestinal microflora.(ABSTRACT TRUNCATED AT 400 WORDS)

The pharmacokinetic and microbiological data of roxithromycin, an oral semisynthetic macrolide, and its clinical use in respiratory infections in Japanese patients are reviewed. In healthy men the maximum plasma concentration (Cmax) and area under the plasma concentration-time curve (AUC) of roxithromycin increase with increasing dosage, as does urinary drug excretion. The drug’s Cmax and half-life are increased compared with erythromycin, josamycin and miocamycin. Maximum sputum and plasma drug concentrations were higher in patients with chronic bronchitis receiving roxithromycin 150mg than in those receiving erythromycin 400mg. Uptake of roxithromycin into polymorphonuclear cells was proportionally greater than that of erythromycin and josamycin. Roxithromycin showed good in vitro activity against respiratory pathogens, including intracellular pathogens such as Legionella pneumophila and Mycoplasma pneumoniae, although it had only about one-quarter of the activity of erythromycin against Staphylococcus aureus and Streptococcus pneumoniae. High success rates were obtained in patients with acute pneumonia (79%) and chronic obstructive airways disease (75%) receiving roxithromycin in a noncomparative trial in 378 patients with respiratory tract infection, and roxithromycin and miocamycin showed similar efficacy in a double-blind study.

The 16-membered macrolide miocamycin (MOM) has been compared with the 14-membered compounds erythromycin and roxithromycin in terms of causing post-antibiotic effects (PAE). Five strains of methicillin-resistant Staphylococcus aureus , 3 Streptococcus pyogenes , 3 S. agalactiae and 3 enterococci, of differing phenotypes of resistance to erythromycin, were tested. PAE were measured follwonig exposure of cocci to 1 ×, 3 × and 10 × MICs of each antibiotic. Against the staphylococci and group A streptococci the three macrolides gave similar results, PAE of 1– h at 1 × MIC, 2–4 h at 3 × MIC and > 4 h at 10 × MIC being observed. For group B streptococci and the only erythromycin-sensitive enterococcus tested, PAE due to MOM were at least double those due to erythromycin or roxithromycin, at each concentration tested. MOM produced significant PAE for the strains that were inducibly resistant to erythromycin and roxithromycin.

A multicentre trial was carried out to compare the efficacy and safety of dirithromycin with miocamycin in the treatment of patients with acute bronchitis or acute exacerbations of chronic bronchitis. The study was a single-blind, randomized, parallel-group study. Dirithromycin was administered orally at a dosage of 500 mg once daily and miocamycin was administered orally at a dosage of 600 mg twice daily; the duration of therapy was five to seven days for both drugs. The results, in 161 assessable patients (78 taking dirithromycin; 83 taking miocamycin), show that dirithromycin and miocamycin have comparable efficacy and safety in the treatment of bronchitis caused by susceptible bacterial pathogens.

Amorphous 16-membered macrolide compounds were prepared by spray drying, and the physicochemical stability of the amorphous states has been investigated. Josamycin, rokitamycin, midecamycin, 3-O-acetyl-4"-O-isovaleryltylosin, miocamycin and 4"-O-(4-methoxyphenyl)acetyltylosin were used as macrolide compounds. From X-ray powder diffractometry and differential scanning calorimetric (DSC) measurements, all the spray dried compounds were recognized to be in a glassy state. Miocamycin and 4"-O-(4-methoxyphenyl)acetyltylosin glasses showed crystallization and fusion peaks on DSC thermograms, and were crystallized after 6 months of storage at 313 K and 75% relative humidity. Other compounds showed only a glass transition peak on each DSC thermogram, and the glassy state was maintained stably against humidity. It was found that the physicochemical stability of the glassy state of miocamycin was closely related to the inlet temperature of the spray drying process.

The efficacy and safety of dirithromycin were compared with those of erythromycin or miocamycin for the treatment of skin and/or skin structure infections in two double-blind, double-dummy, randomized, parallel group, multicentre studies conducted in North America and in Europe, and one single-blind, randomized, parallel group study conducted in Italy. The US and European study patients, in which bacterial infection was confirmed by culture, received either dirithromycin 500 mg once daily or erythromycin base 250 mg four times daily for seven days. Patients in the Italian trial were treated with either 500 mg dirithromycin once daily or with 600 mg miocamycin twice daily for seven days. A total of 156 of the 304 US patients treated with dirithromycin and 127 of the 274 patients treated with erythromycin qualified for efficacy analysis post-therapy. At the post-therapy evaluation, 112 (71.8%) dirithromycin-treated patients were cured and 34 (21.8%) improved compared with 94 (74.0%) and 25 (19.7%) patients treated with erythromycin. The pathogen was eliminated or presumably eliminated in 136 (87.2%) and 110 (86.6%) dirithromycin- and erythromycin-treated patients, respectively. A total of 100 of the 193 dirithromycin-treated patients qualified for efficacy analysis, as did 99 of the 198 erythromycin-treated patients in the European study at post-therapy. Favourable clinical responses (cure or improvement) at the post-therapy visit were recorded in 96 (96.0%) dirithromycin- and 98 (99%) erythromycin-treated patients, and pathogens were eliminated or presumed to have been eliminated in 87 (87.0%) and 88 (88.9%) patients respectively, in the dirithromycin and erythromycin treatment groups. Efficacy analysis was performed in 56 of the 70 Italian patients treated with dirithromycin and in 62 of the 71 patients treated with miocamycin. At post-therapy evaluation, a favourable clinical response was observed in 98.2% of the dirithromycin-treated patients compared with 95.1% of miocamycin-treated patients, whereas a favourable bacteriological response was observed in 52 (92.9%) dirithromycin- and 52 (83.9%) miocamycin-treated patients respectively. In all studies no serious treatment-related events were noted. Events most frequently reported were gastrointestinal in nature. Overall in the three studies, no statistically significant differences were observed between two treatment groups in the clinical and bacteriological outcomes.

Macrolides are the primary drugs of choice for a number of clinically significant infections in children. The clinical aspects of newer macrolides such as roxithromycin, clarithromycin, dirithromycin, flurithromycin, miocamycin, rokitamycin, azithromycin and RP 59500 are discussed in different pediatric infections including streptococcal infections (e.g. pharyngitis, otitis, pneumonia, skin infections), staphylococcus soft tissue infections, mycoplasma pneumonia, chlamydial infections as well as legionellosis and campylobacter enteritis. Also, incidences of adverse events in pediatric patients receiving different macrolides are indicated as well as the dosages in children. The advantages of newer macrolides are: lower dosages, b.i.d. or once daily dosage regimens, good intracellular and tissue penetration, better activity against gram-negative microorganisms (some) and a low rate of adverse reactions.

The activity in vitro of clarithromycin, a new macrolide, was compared to that of various antibiotics in tests using 3,880 clinical isolates. Clarithromycin was two times more active than erythromycin againstStaphylococcus aureus, Enterococcus faecalis, Enterococcus faecium, streptococci of groups C, G and F,Brucella melitensis, Legionella pneumophila andMycoplasma spp., 16 times more active againstUreaplasma urealyticum and 2 to 4 times less active againstCampylobacter spp. In general, clarithromycin showed intrinsic activity 2 to 4 times higher than that of roxithromycin and 4 to 8 times higher than that of miocamycin. Cross-resistance was found between the macrolides. Clarithromycin was bactericidal againstStreptococcus spp. andHaemophilus influenzae.

Rokitamycin and josamycin were successfully derivatized with dansylhydrazine in 20 min at 60°C. Rokitamycin and josamycin levels were determined in plasma after ion-pair extraction into hexane—isoamyl alcohol with lauryl sulphate and precolumn derivatization. Resolution was obtained by liquid chromatography with fluorescence detection ( 352 537 nm) in 12 min. The limit of detection was 20 ng/ml macrolide starting from 1 ml of plasma, and linearity was demonstrated between 50 and 400 ng/ml. Inter-run coefficients of variation were 10.2% at 100 ng/ml and 9.1% at 300 ng/ml. The system was reliably used for pharmacokinetic studies in plasma.

RP 59500 is a 30:70 mixture of RP 57669 and RP 54476. The activity of RP 59500 and its two components against Gram-positive and Gram-negative organisms was compared with that of clarithromycin, roxithromycin, azithromycin and rokitamycin. RP 59500 inhibited 90% of erythromycin-susceptible and resistant Staphylococcus aureus and coagulase-negative staphylococci at less than or equal to 1 mg/L (range 0.06-2 mg/L). Both inducibly and constitutively-resistant strains of S. aureus, as well as strains resistant to rifampicin, gentamicin and ciprofloxacin, were inhibited. Streptococcus pyogenes, including erythromycin-resistant isolates, and group C and G streptococci were inhibited by 0.5 mg/L. Streptococcus pneumoniae and viridans group streptococci were inhibited by 1 mg/L. The MIC90 was 4 mg/L for Haemophilus influenzae and 1 mg/L for Moraxella catarrhalis. RP 59500 did not inhibit Enterobacteriaceae or Pseudomonas aeruginosa. The activity of RP 59500 against streptococci was less than that of the four other macrolides. Clostridium perfringens strains were highly susceptible, as were Bacteroides spp. RP 59500, when combined with ciprofloxacin, cefotaxime or gentamicin, did not have altered activity against susceptible species or alter the activity of the other component of the combination against susceptible species. MBCs in serum were increased two- to four-fold for S. pyogenes, S. pneumoniae and S. aureus, compared with MBCs in broth, but RP 59500 was as active at pH 6 as at pH 7, and there was not an appreciable inoculum effect. RP 59500 has potential use as an agent against inducibly and constitutively erythromycin-resistant isolates of Gram-positive species and selected anaerobic organisms.

Acanthamoeba spp. are the causative agents of granulomatous amoebic encephalitis (GAE) and amoebic keratitis. Recent studies performed by Rassu et al. showed that, compared with the free drug, the loading of rokitamycin in chitosan microspheres improves and prolongs the in vitro antiamoebic activity of rokitamycin. This could be useful in transporting the drug for either ocular application to treat amoebic keratitis or nasal administration as an alternative route for the administration of the drug to the brain in GAE therapy. Starting from the previous study, our goal was to optimize the technological parameters in order to obtain chitosan microparticles loaded with rokitamycin and to evaluate the use of new quaternary ammonium chitosan derivatives in the preparation of spray dried microspheres containing the macrolide; these derivatives showed better characteristics (solubility, penetration enhancement) compared with chitosan itself. Toxicity studies on new polymers were performed. Spray dried loaded microspheres based on chitosan or chitosan derivatives were obtained by using appropriate preparative parameters. Microparticles containing chitosan derivatives showed similar or often better properties than formulations made of chitosan with respect to size, in vitro release behaviour and mucoadhesiveness thus making them more suitable for ocular or nasal administration. New polymers did not demonstrate cytotoxicity. © 2009 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 98:4852–4865, 2009

Macrolides are considered one of the safest anti-infective groups in clinical use and are well-tolerated as alternative antibiotics in patients with a previous adverse reaction to other classes of antibiotics. However there is scarce information in the literature about their long-term tolerability. The present study was performed to determine whether the results of a challenge test with rokitamycin could predict the response to ingestion of rokitamycin during illness. The study was carried out on 335 patients, who experienced adverse reactions to one or more antibiotics. All patients received peroral challenges with rokitamycin (granules or capsules). On the first day patients received a number of placebo doses equivalent to the rokitamycin doses. One week later, the test was administered by increasing doses of rokitamycin at 60 min intervals until the common daily therapeutic dose of 406.25mg was reached (31.25-93.75-125-156.25mg). A questionnaire was distributed to all subjects. In particular, subjects were asked to clarify any reactive symptom they had developed after ingestion of the drug. It was found that only 3.1% (4/129) of subjects, who used this drug, reported adverse reactions: three experienced urticaria/angioedema and one patient experienced erythema multiforme during treatment. This study, points out a low percentage of adverse reactions to rokitamycin after a negative challenge test, thus, emphasizing both safety and good predictive value as a challenge test.

Side effects have been observed when 14-membered macrolides, erythromycin and troleandromycin, have been prescribed concurrently in patients receiving therapeutic doses of theophylline. Rokitamycin is a new 16-membered macrolide antibiotic. We have evaluated its effect on theophylline serum concentrations in 12 adult patients suffering from chronic obstructive pulmonary disease. Initially, six patients were treated for four consecutive days with theophylline as sustained-release formulation in the amount of 600 mg daily; six other patients received for four consecutive days a short term intravenous infusion of 240 mg aminophylline, given over a period of 30 min twice daily. On the last day, blood samples were taken for theophylline determination. Theophylline concentrations were measured serially for 12 hours after oral formulation and 4 hours after aminophylline by enzyme immunoassay technique. Subsequently, while theophylline and aminophylline treatments were continued at the same dosage, each patient received in addition rokitamycin tablets, 400 mg every 12 hours. After seven days of this combined medication, the serial assays of serum theophylline were repeated at the same time intervals as before. Concomitant administration of therapeutic doses of rokitamycin did not affect significantly the steady-state pharmacokinetics of oral theophylline and did not alter the (pseudo-) steady-state pharmacokinetics of intravenous aminophylline, showing that the two drugs may be coadministered without any theophylline dose adjustment.

The activity of rokitamycin, a 16-membered macrolide, was compared with other macrolides and agents used to treat respiratory infections. Rokitamycin had in vitro activity against streptococci and Streptococcus pneumoniae comparable to the other macrolides, inhibiting most organisms at less than 0.03 to 0.5 microgram/ml. It was the most active macrolide agent against Staphylococcus aureus, inhibiting 90% at 1 microgram/ml. Macrolide-resistant streptococci and staphylococci in which resistance was inducible were inhibited, but constitutively resistant Gram-positive bacteria were resistant. Rokitamycin was less active than erythromycin against Haemophilus influenzae, but had activity comparable to erythromycin against Moraxella catarrhalis and Neisseria gonorrhoeae. It inhibited Clostridium spp. and peptostreptococci, but had poor activity against Bacteroides species. Rokitamycin was bactericidal for streptococci and staphylococci, but not for enterococci. Overall rokitamycin has in vitro activity comparable to currently available 14-membered macrolides. Its clinical utility will be influenced by the degree of metabolism to less active metabolites since 70% is rapidly metabolized.

The pharmacokinetics of rokitamycin tablets were studied in 12 healthy volunteers in a randomized cross-over design. The doses tested were 200 mg, 300 mg, 400 mg and 600 mg, as single oral administration. Rokitamycin was absorbed quickly with Tmax for all doses around 30 min after drug intake. Total AUC and Cmax values were linearly related to the administered dose. The buffer formulation determined a low interindividual variation. The overall findings show a good similarity with the data obtained in Japanese subjects. Tolerability was very good.

A group of 18 patients, before undergoing otoplastic surgery, was treated with miocamycin 600 mg in a single dose; middle ear tissue samples were collected at 2, 3, 4 and 6 h. A group of 20 patients suffering from secretory otitis media (SOM) was also treated with 600 mg of miocamycin in a single dose; collections of middle ear fluid (MEF) were performed at 1, 2, 4 and 6 h. Blood withdrawals from all patients occurred at the same time intervals. The miocamycin determination was performed by means of a microbiological method employing Sarcina lutea ATCC 9341. The highest serum levels (1.06 +/- 0.13 mg/l) were found at 2 h in the group from which middle ear mucosa had been withdrawn and at 1 h (2.2 +/- 0.5 mg/l) in the group from which the MEF had been collected; at 6 h miocamycin could be determined in both groups, with values ranging from 0.1 to 0.2 mg/l. In middle ear mucosa the miocamycin concentration was 1.52 +/- 0.27 mg/kg at 2 h and 0.2 +/- 0.09 mg/kg at 6 h. In MEF, the miocamycin concentration was 2.1 +/- 0.27 mg/l at 1 h and 0.24 +/- 0.05 mg/l at 6 h. The miocamycin concentration determined at 1 h in MEF was virtually equal to that in serum at the same time. At the following experimental times of withdrawal, the miocamycin concentration in mucosa specimens, as well as in MEF samples, proved to be markedly higher than values simultaneously found in serum.

The design and synthesis of 16-membered macrolides modified at the C-3 position are described. Starting from fully protected intermediate ( 5 ), appropriate modifications including Heck reaction were performed to furnish 3- O -(3-aryl-2-propenyl)leucomycin A 7 analogues ( 9a – 9m ). These leucomycin A 7 derivatives showed improved in vitro antibacterial activities against clinically important pathogens including erythromycin-resistant Streptococcus pneumoniae (ERSP). SAR analysis of derivatives modified at the C-3 and C-3″ positions suggested that single modification at C-3 or C-3″ was effective for in vitro antibacterial activity.

Twenty patients undergoing tonsillectomy were treated with a peroral administration of 600 mg of miocamycin every 12 hours for 4 days. On the 5th day, after a last administration of a dose of 600 mg the ablation of the tonsils was carried out on groups of 4 subjects, each one at the following times after oral intake of the drug: 2, 4, 6, 8, 12 h. Twenty-nine patients, admitted to hospital to undergo lung resection were treated with peroral administration of miocamycin in accordance with the above mentioned dose scheme. The operation was carried out on groups of 5 subjects, each on the fifth day at the following times after the last administration: 2, 3, 4, 6, 8 and 12 h (4 subjects). Simultaneously blood was withdrawn for the determination of miocamycin in serum. Miocamycin was measured by a microbiological procedure using Sarcina lutea ATCC 9341. The highest levels of miocamycin were observed after 2h in tonsils (3.2 +/- 0.82 mg/kg) and serum (1.3 +/- 0.33 mg/l). After 12h miocamycin proved to be still measurable in the tissue (0.12 +/- 0.05 mg/kg), whereas it was not detected in serum. In pulmonary tissue, the highest levels of miocamycin were likewise identified at the 2nd hour (2.82 +/- 0.59 mg/kg), simultaneously with the highest serum levels (2.3 +/- 0.61 mg/l). At the 12th hour miocamycin could still be dosed in 3 tissue samples, with values between 0.1 and 0.2 mg/kg and was found just at dosing limits in only one serum sample.

Pharmacokinetic interaction between ponsinomycin-nicoumalone was studied in six subjects who received an 8 mg oral dose of racemic nicoumalone alone and 4 days into an oral regimen of ponsinomycin 800 mg twice daily. The concentrations of R(+) and S(-)-nicoumalone in plasma were measured using a stereospecific h.p.l.c. assay. The disposition characteristics of nicoumalone enantiomers in the control phase of this study were similar to those reported previously with the exception of the data for one subject whose oral clearance for S(-)-nicoumalone was seven times lower than those in the other subjects. A statistically significant effect of ponsinomycin on the kinetics of R(+) and S(-)-nicoumalone was not demonstrated.

The effect of ponsinomycin (or miocamycin), a new macrolide antibiotic, was investigated on the pharmacokinetics of carbamazepine (CBZ) administered as a single dose in healthy volunteers. Disposition of the active 10,11 epoxycarbamazepine (ECBZ) was investigated as well. For each compound both total and free plasma concentrations were measured. A moderate (+13%) but statistically significant (p less than 0.05) increase of CBZ total area under the curve (AUC), was observed in the presence of ponsinomycin, accompanied by a 26% decrease (p less than 0.01) in the AUC of its metabolite. There was a tendency toward an increase in AUC of unbound CBZ, although it was not statistically significant. Together these data suggest that formation of ECBZ is inhibited in the presence of ponsinomycin. The relative importance of the epoxy-diol metabolic pathway being increased at steady state due to autoinduction, results of this study suggest that CBZ plasma levels should be carefully monitored in patients receiving ponsinomycin.

Tonsillitis is the most common disease in the otorhinolaryngeal location. For most patients, tonsillitis is attributed to a group A streptococcal infection if the throat culture is positive for that organism or to a viral infection if the throat culture is negative. However, recent studies have shown that Chlamydia trachomatis can produce tonsillar infection. In this study, we evaluated the efficacy of Rokitamycin, a 16-membered ring macrolide antibiotic agent, in the treatment of tonsillitis associated with C. trachomatis. In 26 of 28 (92.9%) patients from whom C. trachomatis was isolated, the organism was eradicated by antimicrobial treatment with Rokitamycin of five days to three weeks' duration. In 25 of the 26 patients, they were totally free of tonsillar symptoms.

No statistically significant changes in the chemiluminescence response of the whole blood were noted following in vitro treatment with 0, 2, 10, 25, or 50 micrograms/ml of erythromycin, josamycin, miomycin, roxithromycin, and spiramycin. These results suggest that these macrolide antibiotics are unlikely to impair the phagocytizing abilities of human neutrophils, in agreement with previous findings indicating their lack of influence upon neutrophil chemotaxis.

Design and synthesis of 16-membered macrolides modified at the C-12 and 13 positions are described. The compounds we report here have an arylalkylamino group attached to the C-12 position of the macrolactone. Both types of derivatives, 12,13-cyclic carbamates and non-carbamate analogues, were synthesized via 12-amino-13-hydroxy intermediates derived from 12,13-epoxide that was prepared by selective epoxidation at the C-12 and C-13 positions. 4′-Hydroxyl analogues were also prepared by acidic hydrolysis of a neutral sugar. These compounds were evaluated for in vitro antibacterial activity against respiratory tract pathogens. Some of these analogues exhibited an improved activity compared with the corresponding parent compound.

To study the antimicrobial susceptibility and prevalence of the different phenotypes and genotypes of macrolide resistance in group A streptococci isolated in Spain in 2004, and to compare the results with those obtained in 1998 and 2001 using the same methodology and centres.A total of 530 unique isolates of Streptococcus pyogenes collected in 21 laboratories from 16 geographic areas (regions) in Spain were used. Antimicrobial susceptibility testing was performed using the agar dilution method. Discs containing erythromycin or clindamycin were used to recognize the phenotypes of macrolide-lincosamide-streptogramin (MLS) resistance. Genes encoding macrolide-lincosamide resistance were detected by PCR.Resistance to erythromycin was 21.7% [95% confidence interval (CI) 16.5-26.3]. The resistance to azithromycin was 21.5%, whereas the resistance to miocamycin and to clindamycin was 6.6% (95% CI 3.0-8.9). Thirty-one (5.8%) of the isolates were resistant to telithromycin. Of the 115 erythromycin-resistant isolates, 67.8% had the M phenotype, representing 14.7% of all the isolates tested. Thirty-five isolates (30.5% of the erythromycin-resistant strains and 6.6% of all the isolates) had the MLS(B) constitutive phenotype. There was a high prevalence of resistance to telithromycin (88.6%) among the 35 strains with the MLS(B) constitutive phenotype. When we compared these results with those from previous studies (1998 and 2001), we found a significant increase in the MLS(B) constitutive phenotype (P0.001), and a significant decrease in the M phenotype (P0.005) was noted.The significant increase in the prevalence of resistance to clindamycin and miocamycin, and the prevalence of resistance to telithromycin reached in a short period of time from the introduction of its use, underscore the need for continuous surveillance of antimicrobial resistance in S. pyogenes in Spain.

Background Although it is well known that a variety of antibacterials may incidentally cause malignant arrhythmia, the list of drugs causing arrhythmia and the impact of these adverse effects are still uncertain. We investigated on this topic by using a large prescription database with different observational designs. Methods Prescription data on all incident users of several antibacterial and antiarrhythmic drugs over the period July 1997 through December 1999 were retrieved from the Drug Prescription Database (DPD) of the Italian Province of Varese. The association between the use of antibacterial and antiarrhythmic drugs was investigated by applying prescription sequence symmetry, cohort and nested case-control designs. Results Lower proarrhythmic effects were on an average obtained from prescription sequence symmetry approach with respect to both cohort and nested case-control. Evidence of association between exposure to drugs (erythromycin and ciprofloxacin) and the risk of arrhythmia was consistently found by the three approaches. No other signals were generated from the prescription sequence symmetry analysis. Two drugs (clarithromycin and levofloxacin) showed patterns compatible with an arrhythmic effect according to both cohort and nested case-control designs. Conclusions Prescription databases are useful tools to explore drug safety through both conventional and emerging observational designs. In spite of its appealing features, prescription sequence symmetry design shows lower sensitivity with respect to conventional designs. Evidence about the association between the use of certain macrolides and fluoroquinolones and the onset of arrhythmia is confirmed by this study. Copyright © 2004 John Wiley & Sons, Ltd.

Erythromycin-resistant Streptococcus pneumoniae isolates from young carriers were tested for their antimicrobial susceptibility; additionally, inducibility of macrolide and clindamycin resistance was investigated in pneumococci carrying erm (A), erm (B), or mef (A). Of 125 strains tested, 101 (81%) were multidrug resistant. Different levels of induction were observed with erythromycin, miocamycin, and clindamycin in erm (B) strains; however, in erm (A) strains only erythromycin was an inducer. Induction did not affect macrolide MICs in mef (A) strains.

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.

The effects of erythromycin (a 14-membered ring macrolide) and rokitamycin (a 16-membered ring macrolide) on the viability of the Streptococcus pyogenes M phenotype were studied by means of flow cytometry and fluorescence microscopy by using a combination of two fluorochromes (syto 9 and propidium iodide) that stains live bacteria green and dead bacteria red. In order to apply the flow cytometry, a bacterial sonication procedure was expressly set up to separate single cells from the long, intralaced S. pyogenes chains of up to 30 to 40 cells that have previously prevented the application of flow cytometry to this type of bacteria. The association of flow cytometry using an appropriate sonication procedure, together with a combination of fluorescent probes, offered the possibility of very quickly investigating the different microbiological effects of rokitamycin at 2 μg/ml, which was active on the S. pyogenes M phenotype, and of erythromycin at doses of up to 32 μg/ml, which was not.

The Group B streptococcus (Streptococcus agalactiae) is a pathogen of increasing importance in human disease. We therefore studied the susceptibility of clinical isolates of S. agalactiae to penicillin G, erythromycin, azithromycin and clindamycin using National Committee for Clinical Laboratory Standards methodology, and we also determined the phenotypes of macrolide-lincosamide susceptibility and the resistance genes implicated in a group of selected isolates of the different phenotypes. We used 221 isolates collected between 1997 and 1999 in two Health Authority Areas in Móstoles and Granada, Spain. The minimal concentration for 90% inhibition (MIC90) for penicillin G was 0.12 mg/L and all the isolates tested were susceptible. One hundred and eighty-five (83.7%) were susceptible to erythromycin and azithromycin and 191 (86.4%) were susceptible to miocamycin and clindamycin. Twenty-three isolates (10.4%) had a constitutive MLSB phenotype, seven (3.2%) an inducible phenotype, and six (2.7%) an M phenotype. All except one of the MLSB phenotype isolates tested (n = 23) carried erm genes; in two strains with the mef (A) gene, all the M phenotype (n = 6) isolates tested carried mef genes, while erm and mef (A) genes were absent in all the macrolide-lincosamide-susceptible (n = 12) isolates tested. In our environment, resistance to macrolide and lincosamide in S. agalactiae was present in 10-16% of the isolates. The majority of resistant strains had the MLSB phenotype.

The aim of this study was to use atomic force microscopy (AFM), an innovative type of micro- scopy, to investigate the different behaviours of erythromycin A (a 14-membered ring) and rokitamycin (a 16-membered ring) in disrupting the morphology of Streptococcus pyogenes with the M phenotype. AFM scanning and sensing of the topography of a sample makes it possible to obtain simultaneous high-resolution digital measurements of the x, y and z coordinates at any point on the bacteria surface. The images obtained before and 2, 4 and 6 h after incubation with erythromycin A (32 mg/L) and rokitamycin (2 mg/L) clearly show that not even high concentrations of erythromycin A interfere with the M phenotype of S. pyogenes, whereas rokitamycin has a progressive action that leads to the formation of abnormally large cells, the loosening of chain structure and the formation of clusters.