جرثومة اللوائية
LEGIONELLA
| Legionella | |
|---|---|
| Legionella sp. under UV illumination. | |
| التصنيف الفهمي | |
| Domain: | Bacteria |
| Phylum: | Proteobacteria |
| Class: | Gammaproteobacteria |
| Order: | Legionellales |
| Family: | Legionellaceae |
| Genus: |
''Legionella'' Brenner et al. 1979 |
| Species | |
|
Legionella adelaidensis | |
==الاكتشاف:==
هذا الجرثوم حديث الاكتشاف فقد اكتشف من 15 سنة فقط، حيث اكتشفه CDC (مركز مراقبة الأمراض) فلكل إنسان لديه تقرير صحي موجود عن حالته الصحية نتيجة عمل رقابي. (حيث حتى محاربي USA الذين حاربوا في فيتنام كانوا يعقدون اجتماعات بين الحين والآخر، ومرة عقدوا اجتماع في فيلاديفيا، وبعده بدؤوا يموتون بأعداد لا بأس بها، حيث ماتوا بنسبة أعلى بعشر مرات من متوسط الأعمر العادي، وهذا تم فقط بعد الاجتماع). وبعد ذلك نتيجة عمل CDC اكتشف جرثوم لم يكن معروف في السابق يعيش في المكيفات واستطاعوا عزله من مياه المكيف التي تكيف الصالة التي عقد فيها الاجتماع، ومن هنا اتى اسم الجرثوم Legion (اللواء).
الصفات
الجرثوم سلبي الغرام يحتاج رطوبة عالية، ولا يعيش بالبيئة الجافة، بل بالبيئات ذات الرطوبة العالية، وفي دورات التكييف. يصيب غالباً الأشخاص بالجيل الثالث من العمر (الذين عمرهم فوق 65 سنة). الإصابة تكون بالجهاز التنفسي، حيث يسبب أعراض ذات رئة غير نموذجية pheumolhialike. الجرثوم هوائي يحتاج إلى السيستئين، فلذلك له شروط مغرسية خاصة حيث يحتاج بيئة رطبة ودرجة حرارة خاصة وفترة حضن طويلة ووجود السيستئين. وهي ليست معروفة بالمزارع قبل اكتشافه. من العناصر الإمراضية للجرثوم أنه قادر على منع التقاء الفاجوزوم phagosome مع الليزوزوم lysosome (الفاجوزوم هي فجوات تحوي الجرثوم، وهي تحوي أنزيمات أكسدة نازعة الهيدروجين، وعندما يصبح دخول الجرثوم، فالتقاء الفجوات يقتل الجرثوم ولكن هناك بعض الجراثيم طورت قدرات لمنع الالتقاء وإذا كانت لدى الجرثوم فيستطيع الجرثوم اغتال البالعات ويعيش فترة أطول).
التشخيص
Legionella is traditionally detected by culture on buffered charcoal yeast extract (BCYE) agar. Legionella requires the presence of cysteine to grow and therefore does not grow on common blood agar media used for laboratory based total viable counts or on site displides. Common laboratory procedures for the detection of Legionella in water concentrate the bacteria (by centrifugation and/or filtration through 0.2 micrometre filters) before inoculation onto a charcoal yeast extract agar containing antibiotics (e.g. glycine vancomycim polymixin cyclohexamide, GVPC) to suppress other flora in the sample. Heat or acid treatment are also used to reduce interference from other microbes in the sample.
After incubation for up toعشرة days, suspect colonies are confirmed as Legionella if they grow on BCYE containing cysteine, but not on agar without cysteine added. Immunological techniques are then commonly used to establish the species and/or serogroups of bacteria present in the sample.
Many hospitals use the Legionella Urinary Antigen test for initial detection when Legionella pneumonia is suspected. Some of the advantages offered by this test is that the results can be obtained in a matter of hours rather than the five days required for culture, and that a urine specimen is generally more easily obtained than a sputum specimen. One disadvantage is that the urine antigen test only detects anti-bodies towards Legionella pneumophila; only a culture will detect infection by the other Legionella species.
New techniques for the rapid detection of Legionella in water samples are emerging including the use of polymerase chain reaction (PCR) and rapid immunological assays. These technologies can typically provide much faster results.
السقم
5% من إصابات ذات الرئة عند الناس هي ناتجة عن هذا الجرثوم. يمكن حتى يسبب الجرثوم أعراض أخرى عامة مثل: ألم في الرأس ـ حرارة ـ وهن. أويسبب أعراض هضمية، أوأعراض عصبية نتيجة الذيفانات. إذا هذا السقم عرضه الرئيسي هوذات رئة غير نموذجية ولكن يوجد أعراض عامة وهضمية وعصبية.
المعالجة
بأحد الفلوروكينونات أوالماكروليدات.
Source control
Common sources of Legionella include cooling towers (used in industrial cooling water systems), large central air conditioning systems, domestic hot water systems, fountains, swimming pools (especially in scandinavian countries and northern ireland) and similar disseminators that draw upon a public water supply. Natural sources include freshwater ponds and creeks. Many governmental agencies, cooling tower manufacturers, and industrial trade organisations have developed design and maintenance guidelines for preventing or controlling the growth of Legionella in cooling towers.
Recent research in the Journal of Infectious Diseases provides evidence that Legionella pneumophila, the causative agent of Legionnaires' disease, can travel at least 6 km from its source by airborne spread. It was previously believed that transmission of the bacterium was restricted to much shorter distances. A team of French scientists reviewed the details of an epidemic of Legionnaires' disease that took place in Pas-de-Calais, northern France, in 2003–2004. There were 86 confirmed cases during the outbreak, of which 18 resulted in death. The source of infection was identified as a cooling tower in a petrochemical plant, and an analysis of those affected in the outbreak revealed that some infected people lived as far as 6–7 km from the plant.
Several European countries established the Infections (EWGLI) to share knowledge and experience about monitoring potential sources of Legionella. The EWGLI has published guidelines about the actions to be taken to limit the number of colony-forming units (CFU, that is, live bacteria that are able to multiply) of Legionella per litre:
| Legionella bacteria CFU/litre | Action required (35 samples per facility are required, including 20 water andعشرة swabs) |
|---|---|
| 1000 or less | System under control. |
| more than 1000 up to 10,000 |
Review program operation. The count should be confirmed by immediate re-sampling. If a similar count is found again, a review of the control measures and risk assessment should be carried out to identify any remedial actions. |
| more than 10,000 | Implement corrective action. The system should immediately be re-sampled. It should then be "shot dosed" with an appropriate biocide, as a precaution. The risk assessment and control measures should be reviewed to identify remedial actions. (150+ CFU/ml in healthcare facilities or nursing homes require immediate action.) |
انظر ايضا
- Brucella
- يرسينيا بستس
- FRANCISELLA TULARENSIS
- مطثية كزازية
- مكورات عنقودية
- مكورات عقدية
- Biocide
- European Working Group for Legionella Infections
- Environmental microbiology
- Nosocomial infection
الهامش
- ^ ISO 11731
- ^ Trends in legionnaires disease, 1980-1998: declining mortality and new patterns of diagnosis. Benin AL; Benson RF; Besser RE. Clin Infect Dis November 1, 2002;35(9):1039-46. Epub October 14, 2002.
- ^ Nguyen, T.; Ilef, D.; Jarraud, S.; Rouil, L.; Campese, C.; Che, D.; Haeghebaert, S.; Ganiayre, F.; Marcel, F.; Etienne, J.; Desenclos, J. (2006). "A community-wide outbreak of legionnaires disease linked to industrial cooling towers—how far can contaminated aerosols spread?". Journal of Infectious Diseases. 193 (1): 102–11. doi:10.1086/498575. PMID 16323138.CS1 maint: multiple names: authors list (link)
- ^ Infections".
روابط اضافية
- Legionella Experts
- CDC Division of bacterial and Mycotic Diseases: Legionellosis
- Directors of Health Promotion and Education page on Legionellosis
- European Working Group for Legionella Infections
- Legionnaires' disease outbreaks
صور
- http://newsimg.bbc.co.uk/media/images/38922000/jpg/_38922367_legionella203.jpg
- http://www.chemistryquestion.com/ / uestion/legionella.jpg
- Images
Maintenance guidelines
- Centers for Disease Control and Prevention - Procedure for Cleaning Cooling Towers and Related Equipment (pages 239 and 240 of 249)
- Cooling Technology Institute - Best Practices for Control of Legionella
- California Energy Commission - Cooling Water Management Program Guidelines For Wet and Hybrid Cooling Towers at Power Plants
- ASHRAE Guideline
- in Ornamental Fountains
