大环内酯类抗生素对革兰氏阳性球菌的体外抗菌活性评价

Evaluation of invitro activities of macrolides against Grampositive cocci

以２４４株革兰氏阳性球菌为实验菌株，红霉素、罗红霉素、ａｚｉｔｈｒｏｍｙｃｉｎ（ＡＺＭ）、交沙霉素为代表药物，通过试管对倍稀释法测定大环内酯类抗生素对革兰氏阳性球菌的最低抑菌浓度，评价其体外抗菌活性。结果显示：大环内酯类抗生素对葡萄球菌属细菌的ＭＩＣ５０为０．５～２μｇ／ｍｌ，ＭＩＣ９０为２～１６μｇ／ｍｌ，对链球菌属细菌的ＭＩＣ５０为０．１２５～２μｇ／ｍｌ，ＭＩＣ９０为０．２５～４μｇ／ｍｌ，ＡＺＭ对葡萄球菌属细菌的ＭＩＣ９０为２～４μｇ／ｍｌ，对链球菌属细菌的ＭＩＣ９０为０．５μｇ／ｍｌ，罗红霉素则分别为４和０．１２５～０．２５μｇ／ｍｌ，红霉素分别为８～１６及０．５～１μｇ／ｍｌ，交沙霉素则分别为４～１６及０．５～４μｇ／ｍｌ，表明ＡＺＭ、罗红霉素抗菌活性相似，优于红霉素及交沙霉素，但ＡＺＭ、罗红霉素与红霉素存在交叉耐药性，而交沙霉素对部分耐红霉素的菌株仍有抗菌活性，大环内酯类抗生素对链球菌属细菌的抗菌活性强于对葡萄球菌属者，肠球菌对大环内酯类抗生素呈现耐药性。

The minimal inhibitory concentration values of erythromycin, josamycin, roxithromycin and azithromycin against 244 strains of Grampositive cocci have been determined by twofold tube dilution method. Results showed that MIC50 of macrolides against staphylococci were 0.5￣2μg/ml, MIC90 were 2￣16μg/ml; the MIC50 against streptococci were 0.125￣2μg/ml, MIC90 were 0.25￣4μg/ml, MIC90 of azithromycin against staphylococci were 2￣4μg/ml, that against streptococci were 0.5μg/ml, the MIC90 and MIC90 of roxithromycin were 4μg/ml and 0.125￣0.25μg/ml, that of erytyromycin were 8￣16μg/ml and 0.5￣1μg/ml, that of josamycin were 4￣16μg/ml and 0.5￣4μg/ml. Results suggested that the in vitro activity of roxithromycin against Grampositive cocci was similar to that of azithromycin and much higher than those of erythromycin and josamycin. However, roxithromycin and azithromycin had crossresistance with erythromycin. Some strains resistant to erythromycin were still sensitive to josamycin. The invitro activities of macrolides against staphylococci were significantly lower than that against streptoccocci. Macrolides have no invitro activities against enterococcus.