Burkholderia mallei
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Burkholderia mallei colonies on blood agar |
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| ( Zopf 1885) Yabuuchi et al. 1993 |
Burkholderia mallei is a gram-negative , rod-shaped, aerobic bacterium . It is a pathogen Burkholderia - type that the disease in humans and animals snot can trigger that leads humans to pneumonia, sepsis and skin and mucosal infections. The Latin name of this reportable disease, malleus, gaveits name to the pathogenpreviously known as Malleomyces mallei . Burkholderia mallei differs from all other representatives of the genus Burkholderia in its true parasitism , immobility and slow growth in culture. Like B. pseudomallei, B. mallei ison the list of potential bio-weapons agents.
Taxonomy
Since its discovery, the pathogen has been classified into numerous systematic groups: Bacillus , Corynebacterium , Mycobacterium , Peifferella , Loefflerella , Malleomyces , Actinobacillus , Pseudomonas . The bacterium has only been assigned to the genus Burkholderia since the early 1990s.
morphology
Due to the lack of flagellation , B. mallei is the only member of its genus that is immobile. Its variable shape ( pleomorphism ) is a mixture between rods and spheres. The bacterium measures 1.5–3 μm in length and 0.5–1 μm in width, the ends are blunt or rounded. The rod shape is straight or slightly curved. In sample material and young bacterial cultures the pathogen occurs predominantly in the form of rods, in older cultures a pleomorphic picture dominates. B. mallei does not form endospores . The bacterium has a capsule-like structure ( exopolysaccharide capsule ) that is only visible in an electron microscope image .
Color behavior and microscopic evidence
Coloring according to Gram is possible. The bacterium often stains only weakly or shows gram-labile behavior (simultaneous occurrence of gram-positive and gram-negative germs in the same preparation). Stored poly-β-hydroxybutyrate in the cytoplasm makes the bacterium appear granular and bipolar (difference in color between the middle and ends of the bacterium). Alternative staining methods are Wright, Giemsa or methylene blue staining . The capsule cannot be visualized with a light microscope.
The microscopic detection of B. mallei from tissue sections is difficult because the pathogen can be present in spherical form. In sample material from secondary infected or contaminated areas, the red pathogen cannot be distinguished from other bacteria microscopically.
Occurrence in the organism
As an organism living as an obligate parasitic organism, the pathogen can only multiply in infected hosts. In clinical sample material, the pathogen is often found outside the body cells ( extracellular ). It can be isolated well from fresh skin lesions, while it occurs only sparsely in older lesions (especially in chronic snot). Sputum , saliva, tears, urine, feces, milk and semen can also contain pathogens. It can only be detected in blood during the phase of disseminated infection ( bacteremia ).
Growth demands
Optimal growth takes place in the neutral pH range, at mesophilic temperatures (37 ° C) and in the presence of oxygen ( aerobes ). With the simultaneous presence of nitrate, growth can also take place under anaerobic conditions (facultative anerobia). At temperatures below 5 ° C and above 42 ° C, the pathogen no longer multiplies.
Cultural cultivation
The pathogen can be grown on conventional, blood-containing culture media . The growth is slow (48-72 h incubation ) and there is a risk of overgrowth by faster growing accompanying germs. The addition of glycerine accelerates growth, so that pre-enrichment with glycerine can be useful. On culture media containing glycerine, the germ grows as a soft, moist, pale cream-colored veil in which the size-variable individual colonies tend to melt away. As the culture ages , the bacterial layer becomes thicker, amber-colored and has a tough, sticky consistency . Glycerine potato medium or glycerine broth are also suitable for cultivation. There is only sparse growth on simple nutrient agar or in gelatin cultures . B. mallei was traditionally grown on potato slices. An aromatic smell is characteristic of the bacterial cultures . To suppress unwanted accompanying flora, clinical samples are pretreated with penicillin or bacteria-inhibiting substances ( proflavine , crystal violet ) are added to the culture media. A selective medium based on glycerine, serum (horse or donkey) and tryptose was developed for the cultivation of the pathogen , to which polymyxin E , bacitracin and actidion are added.
Biochemical properties
B. mallei is chemo-organotrophic . No hemolysis is observed on nutrient media containing blood . The pathogen has the enzymes oxidase and catalase . The indole test and Voges-Proskauer reaction are negative. The pathogen can reduce nitrate . Photosynthetic color pigments are not formed during growth. The breakdown of glucose is mainly oxidative . Although the genus Burkholderia is assigned to the non-fermenters (no degradation of substrate through fermentation), there are indications of isolated fermentation of glucose , mannose , arabinose and fructose . The precise determination of the species Burkholderia mallei on a biochemical basis is not possible with the use of commercially available test systems ( Bunte range ).
Resilience in the environment
In the free environment, B. mallei is neither viable nor capable of reproduction, the resistance ( tenacity ) to external influences is low. It is sensitive to dehydration, heat and sunlight. Direct sunlight kills the pathogen within 24 hours. In dried-up secretions, it loses its infectivity after a few days . However, it can survive for up to 3 months in damp, dark places; in drinking water it remains contagious for 1 month.
The pathogen is inactivated in urine within 40 minutes and in gastric juice within half an hour. Putrefaction does not destroy it until 2–4 weeks.
The bacterium is sensitive to many disinfectants, including formaldehyde (2%), glutaraldehyde (2%), benzalkonium chloride , iodine , lead chloride , potassium permanganate , sodium hypochlorite (1%) and ethanol (70%). In contrast, agents containing phenol show little effectiveness. Historically significant disinfectants were chlorinated lime and phenol.
The microorganisms are inactivated by heat. One-time boiling, temperatures of 80 ° C for 5 minutes or 55 ° C for 10 minutes are sufficient. UV radiation also kills the bacterium. The cold does not eliminate the pathogen.
The natural growth limit of the pathogen is between 20 ° C and 45 ° C.
Antibiotic resistance
Antibiotics such as ceftazidime , imipenem , aminoglycosides such as streptomycin , amikacin , tetracycline , doxycycline, and sulfathiazole were at least effective in vitro . An (eight-week) antibiotic therapy of snot in humans can be carried out with imipenem and doxycycline.
Web links
Bioinformatics Resource Center: Pathema- Burkholderia
Sources / literature
- Wolfgang Bisping & Gunter Amtsberg: Color Atlas for the diagnosis of bacterial infectious agents in animals. , bilingual (German / English), Paul Parey Scientific Publishers, Berlin and Hamburg (1988), ISBN 3-489-50716-9
- Martina B. Oberdorfer: Phenotypic characterization of the species of the genus Burkholderia by means of biochemical fine-tuning and in vitro resistance testing. Diss. (Med.vet.), University of Gießen (2007)
- E. Lührs: 'Rotz' in: Tierheilkunde und Tierzucht. An encyclopedia of practical animal science. ed. Valentin Strang & David Wirth. Urban and Schwarzenberg Berlin, Vienna (1930). Volume 8, pp. 641-662.
- Franz Friedberger & Eugen Fröhner: 'The snot.' in: Textbook of the special pathology and therapy of domestic animals. Ferdinand Enke, Stuttgart (1904), Volume 2, pp. 437-469.
- World Organization for Animal Health: Glanders (PDF file; 80 kB; English)
- Center for Food Security & Public Health: Glanders (PDF file; 118 kB; English)
- Bridget Carr Gregory & David M. Waag: Glanders in: Medical aspects of biological warfare. Borden Institute (2007)
Individual evidence
- ^ Marianne Abele-Horn: Antimicrobial Therapy. Decision support for the treatment and prophylaxis of infectious diseases. With the collaboration of Werner Heinz, Hartwig Klinker, Johann Schurz and August Stich, 2nd, revised and expanded edition. Peter Wiehl, Marburg 2009, ISBN 978-3-927219-14-4 , p. 218 f.
- ↑ a b See Lührs, p. 644
- ↑ See Oberdorfer, p. 7.
- ↑ a b See Friedberger & Fröhner, p. 440.
- ^ See Friedberger & Fröhner, p. 439.
- ↑ Marianne Abele-Horn (2009), p. 219.