Studies on macrolide antibiotics I. Synthesis and antibacterial activity of erythromycin A 9-O-substituted oxime ether derivatives against Mycobacterium avium complex

A series of erythromycin A 9-O-substituted oxime ether derivatives have been synthesized and evaluated for antibacterial activity against Mycobacterium avium complex (MAC) and Staphylococcus aureus. These compounds possessed stronger in vitro activity against MAC including macrolide-resistant strains than clarithromycin (2), although in vitro antibacterial activities of these compounds were less than that of 2 against Staphylococcus aureus. Our studies found that several factors contribute to the antibacterial activity against MAC. The length and spatial orientation of the substituent at 9-position were found to significantly influenced the anti-MAC activity, especially against macrolide-resistant strains. Of all the compounds prepared, erythromycin A 9-[O-(4-phenylbutyl)oxime] (12q) and erythromycin A 9-[O-(3-phenoxypropyl)oxime] (12t) possessed 16 times stronger antibacterial activity than 2 against clarithromycin-resistant strains. Surprisingly, the minimum inhibitory concentrations (MICs) of 12q and 12t against the resistant strains were almost same as those against the susceptible strains. These results suggest that the erythromycin A 9-O-substituted oxime ether derivatives would be promising macrolide antibiotics.

High-performance liquid chromatographic analysis of chlorhexidine in saliva after mouthrinsing

A high-performance liquid chromatographic method was developed to quantify chlorhexidine in human saliva. After addition of an internal standard and acidic-deproteinization, saliva samples were chromatographed by the reversed-phase ion-pair system using pentanesulfonate as a counterion and the eluates were detected by a diode array detector. Under optimal conditions, the baseline separation of analytes was achieved within 4.5 min without interference from components in saliva matrix. The method showed high selectivity to salivary chlorhexidine, quantitative range (50. 0ng/ml-50.0 microg/ml), recovery (96.0-97.8%) and analytical precision (intra- and interassay CVs within 0.41%), permitting the effective application to both saliva and aqueous solutions. Chlorhexidine was found in saliva at microgram per milliliter levels for at least 8 h after mouthrinsing with 10 ml of an aqueous solution of chlorhexidine (0.1 or 1.0 mg/ml) for 1 min. The concentrations of salivary chlorhexidine were reduced by ingesting the acidic beverage and food, but not by ingesting the neutral beverage. The adsorption experiments in artificial saliva revealed that chlorhexidine was significantly adsorbed to saliva-coated hydroxyapatite, buccal epithelial cells and mucin. The proposed method will be a useful tool to study salivary chlorhexidine after oral application and its retention in the oral cavity.

Reversed-phase ion-pair chromatographic analysis of tetracycline antibiotics. Application to discolored teeth

A high-performance liquid chromatographic method with diode array detection was developed to simultaneously separate tetracycline antibiotics and applied to the analysis of discolored teeth. By a reversed-phase ion-pair chromatographic system using pentanesulfonate as a counter ion, minocycline, oxytetracycline, tetracycline and demeclocycline were eluted in this order, and they showed base-line separation within 9 min. When using oxytetracycline as an internal standard, the quantitative ranges were between 2.5 ng/ml and 7.5 microg/ml. Powdered dentine (10 mg) and enamel (40 mg) prepared from discolored primary teeth were sonicated in 0.25 ml of 10 mM HCl containing oxytetracycline (0.75 microg/ml) and 50 mM EDTA-2Na, thereafter the supernatants were chromatographed. Eluates from both discolored tooth samples were identified as minocycline based on diode array spectra of their peaks, while minocycline was not detected in any samples from nondiscolored normal teeth, indicating that discoloration of the tested teeth was due to minocycline incorporated into dentine and enamel. Replicate quantitative analyses of the identical tooth substances showed that intra- and inter-assay C.V.s were 2.63 and 4.95% for dentine, and 5.42 and 10.88% for enamel. Application of the developed method to nine discolored teeth revealed that the incorporated minocycline ranged from 20.13 to 84.62 ng/mg of dentine and 0.89 to 7.87 ng/mg of enamel.

Determination of human immunoglobulin A and secretory immunoglobulin A in bronchoalveolar lavage fluids by solid phase enzyme immunoassay

Solid phase enzyme immunoassay methods for the determination of secretory immunoglobulin A (IgA) and the total amount of serum and secretory IgA in bronchoalveolar lavage fluids (BALF) were developed. The solid phase was prepared by immobilizing rabbit anti-human IgA. Horseradish peroxidase-conjugated goat anti-secretory component or horseradish peroxidase-conjugated goat anti-human IgA (Fc) were used as labeled antibodies. The minimum detectable amounts of secretory IgA and total IgA were 2 and 0.5 ng/well, respectively. These assay methods were successfully applied to the determination of secretory and total IgA levels in BALF samples obtained from 44 subjects including healthy non-smokers, smokers and patients with the following lung diseases: idiopathic pulmonary fibrosis, sarcoidosis and hypersensitivity pneumonitis. The secretory and total IgA levels in BALF collected from healthy non-smokers (n = 9) were 10.5 +/- 3.6 and 25.4 +/- 15.5 (S.D.) micrograms/ml, respectively. In healthy smokers, the secretory IgA concentration was significantly decreased and in idiopathic pulmonary fibrosis, the total IgA was increased. These results indicate that the quantitation of secretory and total IgA may be useful for the investigation of lung disease.

Dilated cardiomyopathy in a patient receiving continuous ambulatory peritoneal dialysis

We describe a unique case of a 10 year old girl with dilated cardiomyopathy who has been receiving continuous ambulatory peritoneal dialysis. She responded to treatment with a beta 1-agonist. We note that electrocardiography and echocardiography are effective for early recognition of the onset of dilated cardiomyopathy and that a thallium scan should be performed to assess the severity of dilated cardiomyopathy in patients with chronic renal insufficiency.