Hallander H O, Laurell G
Antimicrob Agents Chemother. 1972 May;1(5):422-6. doi: 10.1128/AAC.1.5.422.
Methicillin-resistant strains of Staphylococcus aureus, in total 84, representing 16 laboratories in 8 different countries were all resistant to 32 mug of cephalothin per ml with the same typical heteroresistant pattern. With the disc diffusion method, they were easily detected when cephalexin discs were used. With cephalothin discs, on the other hand, 26 to 49% would have been falsely categorized as Group I or II after 24 hr. It is recommended that susceptibility testing of S. aureus to cephalosporins by using the paper disc method be performed with 30-mug cephalexin discs on Mueller-Hinton agar without blood. With an inoculum of 10(6) bacteria/ml, an incubation temperature of 30 C, and an incubation time of 24 hr, a zone of less than 10 mm indicates presumptive heteroresistance. This corresponds to the international recommendation with a minimal inhibitory concentration of 32 mug/ml as the upper limit of Group II.
总计84株耐甲氧西林金黄色葡萄球菌菌株，代表8个不同国家的16个实验室，均对每毫升含32微克头孢噻吩呈现耐药，且具有相同的典型异质性耐药模式。采用纸片扩散法时，使用头孢氨苄纸片很容易检测到它们。另一方面，使用头孢噻吩纸片时，24小时后26%至49%的菌株会被错误分类为I组或II组。建议在不含血的Mueller-Hinton琼脂上，使用含30微克头孢氨苄的纸片，通过纸片法对金黄色葡萄球菌进行头孢菌素敏感性试验。接种量为每毫升10(6)个细菌，培养温度为30℃，培养时间为24小时，抑菌圈直径小于10毫米表明可能存在异质性耐药。这与国际上以最低抑菌浓度32微克/毫升作为II组上限的建议一致。
