Orth Dorothea, Grif Katharina, Dierich Manfred P, Würzner Reinhard
Department of Hygiene, Microbiology and Social Medicine, Innsbruck Medical University and Austrian Reference Laboratory for Enterohemorrhagic Escherichia coli, Schöpfstr. 41, A-6020 Innsbruck, Austria.
Res Microbiol. 2007 Mar;158(2):105-11. doi: 10.1016/j.resmic.2006.10.007. Epub 2006 Dec 20.
Tellurite-containing media are widely used for the screening and isolation of Shiga toxin-producing Escherichia coli (STEC) O157:H7, but tellurite resistance among non-O157 STEC is poorly characterized. Therefore, we investigated 202 STEC strains representing 61 different serotypes from humans, animals or food for the presence of ter genes by PCR and their correlation with tellurite resistance, by assessing growth on cefixime-tellurite sorbitol MacConkey agar. All strains were screened for terC, terE and terF as markers for the ter gene cluster. Of the 202 strains, 127 contained terC and terE and were tellurite-resistant, but only 121 of these also contained terF. All 72 non-sorbitol-fermenting O157:H7 and O157:NM (non-motile) strains contained terC, terE and terF and expressed tellurite resistance. In contrast, all eight sorbitol-fermenting STEC O157:NM were terC-, terE- and terF-negative and tellurite-sensitive. Among non-O157 STEC, terC, terE and terF were found in all seven O145:NM, four O111:H8/NM, 17 of 18 O26:H11/NM and in 21 strains of 14 other serotypes. The strong correlation between the presence of ter genes and the ability to grow on tellurite-containing media suggest that the ter genes encode tellurite resistance in the vast majority of these strains. The presence of the ter gene cluster was significantly (P<0.00001) associated with the presence of eae genes. We conclude that the use of tellurite-containing media in screening for STEC will allow the detection of STEC O26, O111, O145 and non-sorbitol-fermenting O157, but most strains (in this study 74.3%) from other serotypes will be missed.
含亚碲酸盐的培养基被广泛用于筛选和分离产志贺毒素大肠杆菌（STEC）O157:H7，但非O157 STEC中的亚碲酸盐抗性特征尚不明确。因此，我们通过PCR研究了202株代表61种不同血清型的来自人类、动物或食物的STEC菌株中ter基因的存在情况，并通过评估其在头孢克肟-亚碲酸盐山梨醇麦康凯琼脂上的生长情况，研究了它们与亚碲酸盐抗性的相关性。所有菌株均筛选了作为ter基因簇标记的terC、terE和terF。在202株菌株中，127株含有terC和terE且对亚碲酸盐具有抗性，但其中只有121株也含有terF。所有72株非山梨醇发酵的O157:H7和O157:NM（无动力）菌株均含有terC、terE和terF并表现出亚碲酸盐抗性。相比之下，所有8株山梨醇发酵的STEC O157:NM均为terC、terE和terF阴性且对亚碲酸盐敏感。在非O157 STEC中，在所有7株O145:NM、4株O111:H8/NM、18株O26:H11/NM中的17株以及14种其他血清型的21株菌株中发现了terC、terE和terF。ter基因的存在与在含亚碲酸盐培养基上生长的能力之间的强相关性表明，在绝大多数这些菌株中，ter基因编码亚碲酸盐抗性。ter基因簇的存在与eae基因的存在显著相关（P<0.00001）。我们得出结论，在筛选STEC时使用含亚碲酸盐的培养基将能够检测到STEC O26、O111、O145和非山梨醇发酵的O157，但其他血清型的大多数菌株（在本研究中为74.3%）将会被漏检。
