The authors isolated two strains of an unnamed bacterial biotype with characteristics intermediate between those of Enterobacter and Citrobacter. The organisms did not produce acetyl-methyl carbinol, but decarboxylated lysine. Apart from the latter trait, they most closely resemble H2S-negative Citrobacter freundii. They differ biochemically from all other currently accepted species of enterobacteriaceae. Their pathogenic significance appears similar to that of the two genera they most closely resemble. Only by recognition and study of additional strains can their identity be more definitively delineated and their significance more fully assessed.
Eight novel chromogenic substrates were evaluated for their efficacy in detecting lipase activity in clinical isolates of Staphylococcus aureus from the United Kingdom and Malta. All isolates metabolized the chromogenic lipase substrates 5-(4-hydroxy-3,5-dimethoxyphenylmethylene)-2-thioxothia-zolidin-4-one-3-ethanoic acid (SRA)-propionate, SRA-butyrate, SRA-octanoate and 2-[2-(4-hydroxy-3,5-dimethoxyphenyl)-vinyl]-3-methy-benzothiazolium salt (SBZTM)-acetate. Over 90% of the isolates metabolized the lipase substrates SRA-decanoate and SRA-laurate. However, only 0.6% of UK isolates and 2% of Maltese isolates metabolized the lipase substrate SRA-myristate; none of the isolates tested metabolized SBZTM-butyrate. Traditional Tween 80 assays showed that over 73% of the UK methicillin-resistant Staphylococcus aureus (MRSA) isolates and 83% of the UK methicillin-sensitive Staphylococcus aureus (MSSA) isolates demonstrated lipolytic activity. In contrast, Maltese isolates showed lipase activity in 94% and 88% of the MRSA and MSSA strains, respectively. Lipases in MRSA and MSSA demonstrated substrate specificity whose activity appeared dependent upon hydrocarbon chain length of the chromogen. These novel chromogens can be used for lipase enzyme detection and have application for full characterization of numerous S. aureus lipases.
Fucoidan is a sulfated polysaccharide found in brown seaweed. Due to its reported biological activities, including antiviral, antibacterial and anti-inflammatory activities, it has garnered significant attention for potential biomedical applications. However, the direct relationship between fucoidan extracts' chemical structures and bioactivities is unclear, making it extremely challenging to predict whether an extract will possess a given bioactivity. This relationship is further complicated by a lack of uniformity in the recent literature in terms of the assessment and reporting of extract properties, yield and chemical composition (e.g., sulfate, fucose, uronic acid and monosaccharide contents). These inconsistencies pose significant challenges when directly comparing extraction techniques across studies. This review collected data on extract contents and properties from a selection of available studies. Where information was unavailable directly, efforts were made to extrapolate data. This approach enabled a comprehensive examination of the correlation between extraction techniques and the characteristics of the resulting extracts. A holistic framework is presented for the selection of fucoidan extraction methods, outlining key heuristics to consider when capturing the broader context of a seaweed bioprocess. Future work should focus on developing knowledge within these heuristic categories, such as the creation of technoeconomic models of each extraction process. This framework should allow for a robust extraction selection process that integrates process scale, cost and constraints into decision making. Key quality attributes for biologically active fucoidan are proposed, and areas for future research are identified, such as studies for specific bioactivities aimed at elucidating fucoidan's mechanism of action. This review also sets out future work required to standardize the reporting of fucoidan extract data. Standardization could positively enhance the quality and depth of data on fucoidan extracts, enabling the relationships between physical, chemical and bioactive properties to be identified. Recommendations on best practices for the production of high-quality fucoidan with desirable yield, characteristics and bioactivity are highlighted.
ABSTRACT The BACTEC MGIT 960 system, a fully automated, nonradiometric, noninvasive system for detection and drug susceptibility testing of mycobacteria, was evaluated for the ability to test susceptibilities to second-line drugs. In this study, which was carried out in three phases (phase I, mostly susceptible strains; phase II, mostly resistant strains; phase III, final testing of the optimal drug concentrations found in phases I and II), we established the critical concentrations for seven drugs to be tested in the BACTEC MGIT 960 system compared to the BACTEC 460TB system. The critical concentrations for the seven drugs used in the MGIT 960 system are as follows: amikacin, 1.0 μg/ml; capreomycin, 2.5 μg/ml; ethionamide, 5.0 μg/ml; protionamide, 2.5 μg/ml; ofloxacin, 2.0 μg/ml; rifabutin, 0.5 μg/ml; linezolid, 1.0 μg/ml. Our results demonstrate that the BACTEC MGIT 960 system is an accurate method for rapid testing of the susceptibilities of Mycobacterium tuberculosis to second-line drugs.
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