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''Burkholderia pseudomallei'' (also known as ''Pseudomonas pseudomallei'') is a Gram-negative, bipolar, aerobic, motile rod-shaped bacterium.〔(【引用サイトリンク】 work=VirginiaTech Pathogen Database )〕 It infects humans and animals and causes the disease melioidosis. It is also capable of infecting plants. ''B. pseudomallei'' measures 2–5 μm in length and 0.4–0.8 μm in diameter and is capable of self-propulsion using flagellae. The bacteria can grow in a number of artificial nutrient environments, especially betaine- and arginine-containing ones. ''In vitro'', optimal proliferation temperature is reported around 40 °C in neutral or slightly acidic environments (pH 6.8–7.0). The majority of strains are capable of fermentation of sugars without gas formation (most importantly, glucose and galactose, older cultures are reported to also metabolize maltose and starch). Bacteria produce both exo- and endotoxins. The role of the toxins identified in the process of melioidosis symptom development has not been fully elucidated. == Identification == ''B. pseudomallei'' is not fastidious and will grow on a large variety of culture media (blood agar, MacConkey agar, EMB, etc.). Ashdown's medium (or ''Burkholderia cepacia'' medium) may be used for selective isolation. Cultures typically become positive in 24 to 48 hours (this rapid growth rate differentiates the organism from ''B. mallei'', which typically takes a minimum of 72 hours to grow). Colonies are wrinkled, have a metallic appearance, and possess an earthy odour. On Gram staining, the organism is a Gram-negative rod with a characteristic "safety pin" appearance (bipolar staining). On sensitivity testing, the organism appears highly resistant (it is innately resistant to a large number of antibiotics including colistin and gentamicin) and that again differentiates it from ''B. mallei'', which is in contrast, exquisitely sensitive to a large number of antibiotics. For environmental specimens only, differentiation from the nonpathogenic ''B. thailandensis'' using an arabinose test is necessary (''B. thailandensis'' is never isolated from clinical specimens). The laboratory identification of ''B. pseudomallei'' has been described in the literature. The classic textbook description of ''B. pseudomallei'' in clinical samples is of an intracellular, bipolar-staining, Gram-negative rod, but this is of little value in identifying the organism from clinical samples.〔 Some suggest the Wayson stain is useful for this purpose, but this has been shown not to be the case. Laboratory identification of ''B. pseudomallei'' can be difficult, especially in Western countries where it is rarely seen. The large wrinkled colonies look like environmental contaminants, so are often discarded as being of no clinical significance. Colony morphology is very variable and a single strain may display up multiple colony types, so inexperienced laboratory staff may mistakenly believe the growth is not pure. The organism grows more slowly than other bacteria that may be present in clinical specimens, and in specimens from nonsterile sites, is easily overgrown. Nonsterile specimens should, therefore, be cultured in selective media (e.g., Ashdown's or ''B. cepacia'' medium).〔 For heavily contaminated samples, such as faeces, a modified version of Ashdown's that includes norfloxacin, amoxicillin, and polymyxin B has been proposed. In blood culture, the BacT/ALERT MB system (normally used for culturing Mycobacterium) by bioMérieux has been shown to have superior yields compared to conventional blood culture media. Even when the isolate is recognised to be significant, commonly used identification systems may misidentify the organism as ''Chromobacterium violaceum'' or other nonfermenting, Gram-negative bacilli such as ''Burkholderia cepacia'' or ''Pseudomonas aeruginosa''. Again, because the disease is rarely seen in western countries, identification of ''B. pseudomallei'' in cultures may not actually trigger alarms in physicians unfamiliar with the disease. Routine biochemical methods for identification of bacteria vary widely in their identification of this organism: the API 20NE system accurately identifies ''B. pseudomallei'' in 99% of cases, as does the automated Vitek 1 system, but the automated Vitek 2 system only identifies 19% of isolates.〔 The pattern of resistance to antimicrobials is distinctive, and helps to differentiate the organism from ''P. aeruginosa''. The majority of ''B. pseudomallei'' isolates are intrinsically resistant to all aminoglycosides (via an efflux pump mechanism), but sensitive to co-amoxiclav: this pattern of resistance almost never occurs in ''P. aeruginosa'' and is helpful in identification. Unfortunately, the majority of strains in Sarawak, Borneo, are susceptible to aminoglycosides and macrolides, which means the conventional recommendations for isolation and identification do not apply there. Molecular methods (PCR) of diagnosis are possible, but not routinely available for clinical diagnosis. Fluorescence ''in situ'' hybridisation has also been described, but has not been clinically validated, and it is not commercially available. In Thailand, a latex agglutination assay is widely used,〔 while a rapid immunofluorescence technique is also available in a small number of centres. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Burkholderia pseudomallei」の詳細全文を読む スポンサード リンク
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