Soner YILMAZ, Serhat DUYAN, CUMHUR ARTUK, Hüsrev DİKTAŞ

Mikrobiyoloj ik Tanımlamada MALDI-TOF MS Uygulamaları

MALDI-TOF MS (Matriks assisted laser desorption ionization time of flight mass spectrometry) günümüzde mikroorganizma tanımlanmasında kullanılan yeni bir yöntemdir. Bu yöntem, mikroorganizmaların protein yapılarını iyonize ettikten sonra elektrik alandan geçirerek protein profillerinin çıkarılması esasına dayanır. Elde edilen profiller sistemin kütüphanesindeki verilerle karşılaştırılarak tanımlama yapılır. Tanımlama için temel alınan mikroorganizma proteinleri ise esasen çevresel koşullardan az etkilenen ribozomal proteinlerden oluşmaktadır. MALDI-TOF MS ile yapılacak tanımlama çalışmaları tercihen taze kültürlerden yapılmalıdır. Eski kültürlerde ribozomal proteinlerde bozulmalar meydana gelmektedir. Rutin bakteri izolatlarında %84,1 ile %95,2 arasında değişen oranda doğru tanımlama yapmaktadır. Maya tanımlamasında da başarı oranı %85 ile %100 arasında değişmektedir. Pozitif kan kültür şişelerinden, subkültüre gerek olmadan tanımlama yapabilmektedir. İdrar örneklerinde mikrolitrede 105 ve üzeri bakteri olduğunda da direkt örnekten tanımlama yapabilmektedir. Konvansiyonel ve moleküler tanımlama yöntemleri ile kıyaslanacak olursa MALDI-TOF MS örnek başı maliyeti ve tanımlama için geçen süre yönünden çok daha etkin görülmektedir.

Applications of MALDI-TOF MS in Microbiological İdentification

MALDI-TOF MS (Matriks assisted laser desorption ionization time of flight mass spectrometry) is a new metohod for identification of microorganisms nowadays. This method is based revealing of microorganisms protein profile with ionization of protein structure and these ionized mass pass through the electrical field. Profiles which were obtained from microorganisms compare with database of system thus identification is made by this way. Ribosomal proteins are used in identification which are less affected by enviromental conditions. Fresh culture should preferably use in MALDI-TOF MS identification. Ribosomal proteins can be deteriorate in old cultures. The correct identification rates are changing between 84,1% to 95,2% in routine bacterial isolates. The correct identification rates in yeasts are changing between 85% to 100%. It makes identification in positive blood culture bottles without the need of subculture, also makes identification on urine samples without the need of culture which has greater than 105 microorganisms in a microliter. When it compared with conventional and molecular identification methods, it is more effective on per sample costs and elapsed time on working.

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