Dondurulmufl k›ymalarda Escherichia coli O157:H7 araflt›rmada kullan›lan lauryl tryptose (LST) buyyon ve HC (Hemorrhagic colitis E. coli strains) agar›n selektivitesi art›r›lmaya çal›fl›ld›. LST buyyonun selektivitesi novobiyosin (20 mg/l) içeren LST (LST + n) buyyondan daha yüksek bulundu, fakat novobiyosin, sefiksim (0,05 mg/l) ve tellurit (2,5 mg/l) içeren LST (LST + nct) buyyon zenginlefltirme besiyeri olarak uygun bulunmad›. Sorbitol pozitif sufllar sorbitol negatif sufllara k›yasla novobiyosine anlaml› derecede daha dirençli bulundular (P < 0,05). Sonuç olarak, k›ymalar›n LST gibi saplementsiz uygun bir besiyerinde zenginlefltirilmesi, ve sonra da bu kültürden ve bu kültürün ilk üç ondal›k seri seyreltisinden yeteri miktarda al›narak ramnoz ve sorbitol bazl› sefiksim-telluritli HC agar gibi bir kat› besiyerine ekilmesi rutin bir kültür yöntemi olarak önerilebilir nitelikte bulunmufltur. Eosin methylene blue (EMB) agar›n metalik yans›ma özelli¤i CTR-HC agara transfer edilebilinirse analiz süresini bir gün k›saltacak olan bu besiyeri mevcut besiyerlerine alternatif olabilir. Salisin veya 4-methylumbelliferyl-β-D glucuronide (MUG)’in rutin kültür yöntemlerinde kullan›lmas› gerekli bulunmad›.

We aimed to improve the selectivity of lauryl tryptose (LST) broth and HC (hemorrhagic colitis Escherichia coli strains) agar for the detection of E. coli O157:H7 in frozen ground beef samples. The selectivity of LST broth was superior to that of LST containing novobiocin (20 mg/l) (LST + n), but LST containing novobiocin, cefixime (0.05 mg/l) and tellurite (2.5 mg/l) (LST + nct) was found to be unsuitable as an enrichment medium. The sorbitol positive strains were significantly more resistant to novobiocin than were the sorbitol negative strains (P < 0.05). As a result, the enrichment of ground beef samples in a selective broth without antibiotics such as LST, and then spread plating a subsequent amount from this original enrichment culture and the first three 10-fold serial dilutions onto a rhamnose and sorbitol based selective medium such as cefixime-tellurite HC medium (CTR-HC) was found to be recommendable as a routine cultural method. Transferring the metallic sheen property of eosin methylene blue (EMB) agar to CTR-HC agar can represent an alternative to the available media, and this will shorten the analysis time by 1 day. Use of salicine or 4-methylumbelliferyl-b-D glucuronide appears unnecessary in routine cultural techniques.