Boyce J M
J Clin Microbiol. 1984 Jun;19(6):813-7. doi: 10.1128/jcm.19.6.813-817.1984.
To reevaluate the ability of the disk diffusion method to detect methicillin-resistant Staphylococcus aureus, 73 such isolates from 13 cities were tested for antimicrobial susceptibility with the standardized disk diffusion test. Duplicate plates were incubated at 30 and 35 degrees C and read after 18, 24, and 48 h. After incubation at 35 degrees C for 24 h, 97% of isolates appeared resistant to methicillin, and 99% appeared resistant to oxacillin. A significantly smaller proportion of isolates appeared resistant to cephalothin (P less than 0.001) and cefamandole (P less than 0.001). Isolates from some cities had no zones of inhibition around methicillin and oxacillin disks, whereas those from other cities had measurable zones of inhibition, with light growth inside the zones. Patterns of growth around cephalothin and cefamandole disks also varied among isolates from different cities. Incubation at 30 degrees C for 24 h did not result in better detection of methicillin or oxacillin resistance. All study isolates appeared resistant to methicillin and oxacillin after 48 h of incubation at 35 degrees C. The results suggest that methicillin-resistant S. aureus strains from many areas will be detected if standardized disk diffusion tests are incubated at 35 degrees C for 24 h.
为了重新评估纸片扩散法检测耐甲氧西林金黄色葡萄球菌的能力，对来自13个城市的73株此类分离株进行了标准化纸片扩散试验以检测其抗菌药敏性。将重复的平板分别在30℃和35℃下孵育，并在18、24和48小时后读取结果。在35℃下孵育24小时后，97%的分离株对甲氧西林耐药，99%的分离株对苯唑西林耐药。对头孢噻吩耐药（P<0.001）和对头孢孟多耐药（P<0.001）的分离株比例明显较小。来自一些城市的分离株在甲氧西林和苯唑西林纸片周围没有抑菌圈，而来自其他城市的分离株有可测量的抑菌圈，圈内有轻度生长。不同城市分离株在头孢噻吩和头孢孟多纸片周围的生长模式也有所不同。在30℃下孵育24小时并不能更好地检测甲氧西林或苯唑西林耐药性。在35℃下孵育48小时后，所有研究分离株均对甲氧西林和苯唑西林耐药。结果表明，如果标准化纸片扩散试验在35℃下孵育24小时，许多地区的耐甲氧西林金黄色葡萄球菌菌株将被检测出来。
