Hirschl A, Stanek G, Rotter M
Zentralbl Bakteriol A. 1980;248(3):304-13.
Coagulase-positive staphylococci (41 methicillin-resistant strains, 28 penicillinase-positive and 12 penicillinase-negative strains) were tested against most types of penicillines commercially available on the Austrian market using both broth-dilution test (incubated during 48 hours at 35 degrees C) and agardiffusion tests (incubated during 24 hours at 30, 35 and 37 degrees C) employing Mueller-Hinton-broth and -agar, respectively, in order to find out the most convenient way of detecting methicillin-resistant strains. Consecutively, the conclusions drawn from these experiments were verified for tests on Isosensitest-agar (Oxoid). It was demonstrated that methicillin-resistant strains could be detected easily with discs of methicillin and oxacillin at 30 degrees C (Fig. 1). At 35 degrees C this was nearly as easily possible for methicillin but oxacillin discs had to be used at amounts of 1 microgram instead of 5 microgram. Excepting penicillin G-discs with the other penicillines differing numbers of methicillin-resistant strains would have been missed at 37 degrees C (Fig. 1, 2). Only with discs containing 6 microgram penicillin G methicillin-resistant strains were unequivocally identifiable in the agardiffusion test at all 3 incubation-temperatures (Fig. 3), the largest inhibition zone diameter being 12 mm. Penicillinase-positive but methicillin-sensitive strains always produced larger inhibition zones up to 30 mm. From these strains again penicillinase-negative strains were equally well distinguishable by much larger inhibition zones. So, the conclusion was drawn that on Mueller-Hinton agar one disc loaded with 6 microgram of penicillin G allows proper distinction not only of methicillin-resistant and -sensitive but also of penicillinase-positive and -negative strains of staphylococci. On Isosensitest-agar this is true for an incubation-temperature of 35 but not 37 degrees C (Tab. 1).
对凝固酶阳性葡萄球菌（41株耐甲氧西林菌株、28株青霉素酶阳性菌株和12株青霉素酶阴性菌株），使用肉汤稀释试验（在35℃孵育48小时）和琼脂扩散试验（分别在30、35和37℃孵育24小时），采用穆勒-欣顿肉汤和琼脂，检测奥地利市场上大多数市售类型的青霉素，以找出检测耐甲氧西林菌株的最便捷方法。随后，在异感试琼脂（Oxoid）上进行的试验验证了从这些实验得出的结论。结果表明，在30℃时，用甲氧西林和苯唑西林纸片可轻松检测出耐甲氧西林菌株（图1）。在35℃时，用甲氧西林检测几乎同样容易，但苯唑西林纸片的用量必须为1微克而非5微克。除青霉素G纸片外，在37℃时，使用其他青霉素纸片会遗漏不同数量的耐甲氧西林菌株（图1、2）。只有含6微克青霉素G的纸片，在所有3个孵育温度下的琼脂扩散试验中都能明确鉴定出耐甲氧西林菌株（图3），最大抑菌圈直径为12毫米。青霉素酶阳性但对甲氧西林敏感的菌株始终产生更大的抑菌圈，可达30毫米。从这些菌株中，青霉素酶阴性菌株同样可通过大得多的抑菌圈很好地区分出来。因此得出结论，在穆勒-欣顿琼脂上，一张加载6微克青霉素G的纸片不仅能正确区分葡萄球菌的耐甲氧西林和敏感菌株，还能区分青霉素酶阳性和阴性菌株。在异感试琼脂上，在35℃而非37℃孵育时情况也是如此（表1）。
