Leyla VATANSEVER, Murat GÜLMEZ, Çiğdem SEZER, Abamüslüm GÜVEN, Berna DUMAN

Use of salicin-rhamnose-cellobiose-4-methylumbelliferyl-Beta-D Glucuronide-sorbitol MacConkey (SRC-MUG-SMAC) differential agar for the presumptive identification of Escherichia coli 0157 from the primary isolation step

Bu çalışmada, sorbitoi negatif ve sefiksim-tellurite dirençli tipik suşlar arasından şüpheli Escherichia coli 0157 suşlarının izolasyonu için bir ayırıcı katı besiyeri araştırıldı. Bu amaç için, 8 referans suş kolonisine paralel olarak gıda örneklerine (beyaz peynir, çiğ süt ve kıyma) ait sefiksim-tellurit (CT) içeren sorbitoi MacConkey (CT-SMAC) besiyeri yüzeyinden seçilen 1130 şüpheli koloni ayırıcı katı besiyerine transfer edildi. Şalisin (S), ramnoz (R), sellobiyoz (C) hem ayrı ayrı, hem de üçü birlikte MUG ile kombine edilerek test edildi. SRC ve MUG içeren ve dıştan çizimle 25 numaralı bölmeye ayrılan ayırıcı katı besiyeri (SRC-MUG-SMAC) plaklarının (100 x 15 mm) 42 °C'de 6 saat inkübasyonundan sonra, 1130 susun sadece 47 (% 4,15)'sinin tipik E. Coli O157 özelliği gösterdiği gözlendi. Violet red bile lactose agar (VL) aynı tarzda kullanıldığında ise 1130 susun sadece 16 (% 1,41)'sı tipik özellik gösterdi. Bu prosedürde ileri identifikasyon için başka bir biyokimyasal teste ihtiyaç duyulmadı. Koloni seçim aşamasında SRC-MUG-SMAC katı besiyerinin kullanılmasının ilk izolasyon katı besiyerlerine bu şekerlerin ve MUG'un katılmasına kıyasla daha ayırıcı olduğu görüldü. Sonuç olarak, şüpheli E. coli 0157 identiftkasyonunda MUG ile birlikte susun fermente edemediği 3 veya daha fazla şeker içeren bir ayırıcı agar plağı kullanmanın hızlı, kolay, kesin ve göreceli olarak ucuz olması nedeniyle özellikle rutin tarama laboratuarları için ideal olduğu görüldü.

İlk izolasyon aşamasında escherichia coli 0157' nin şüpheli identifikasyonu amacıyla salisin-Ramnoz-Sellobiyoz-4-Metilumbelliferil-Beta-D Glukuronit-sorbitol MacConkey (SRC-MUG-SMAC) ayırıcı katı besiyerinin kullanılması

A differential agar for the further detection of presumptive Escherichia coli O157 strains among typical sorbitol negative and cefixime-tellurite resistant strains was investigated. For this purpose, in parallel to colonies of 8 reference strains, 1130 suspect colonies picked from the surface of cefixime-tellurite (CT)-sorbitol MacConkey (SMAC) (CT-SMAC) agar plates of food samples (white cheese, raw milk and ground beef) were transferred to differential agar plates. After a 6-h incubation period at 42 ºC, only 47 (4.15%) of the 1130 colonies appeared as typical E. coli O157 on the differential agar plates (100 x 15 mm) gridded into 25 numbered sections. Salicin (S), rhamnose (R) and cellobiose (C) were tested separately and together in combination with MUG. The best results were obtained from the combined use of the 3 in SMAC medium (SRC-MUG-SMAC). When violet red bile lactose agar (VL) was used in the same manner as SRC-MUG-SMAC, only 16 (1.41%) of the 1130 colonies remained typical. In this procedure, no biochemical test was required for further identification. The use of an SRC-MUG-SMAC plate immediately after the colony selection step appeared to be more discriminative than the addition of these sugars and MUG to the primary isolation media. As a result, the testing of presumptive E. coli O157 colonies using a differential agar plate including MUG and 3 (or more) sugars that are not fermented by this organism is a rapid, easy, precise and relatively inexpensive isolation procedure, and it is particularly ideal for use in routine screening laboratories.

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