Brook I, Coolbaugh J C, Walker R I, Weiss E
Antimicrob Agents Chemother. 1984 Jan;25(1):71-7. doi: 10.1128/AAC.25.1.71.
Clinical isolates of the Bacteroides melaninogenicus and Bacteroides fragilis groups were tested for in vitro and in vivo susceptibility to penicillin, clindamycin, and metronidazole, used singly or in combination with gentamicin. The in vitro tests consisted of determinations of minimal inhibitory concentrations (MICs) carried out with or without constant amounts of gentamicin. When used alone, gentamicin had negligible effects on the bacteria but significantly reduced the MICs of penicillin, clindamycin, and metronidazole against 11, 10, and 3, of the 15 strains of the B. melaninogenicus group, respectively. The 15 strains of the B. fragilis group were all beta-lactamase producers and were highly resistant to penicillin or the combination of penicillin and gentamicin. However, gentamicin reduced the MICs of clindamycin and metronidazole against 1 and 7 strains of this group, respectively. The in vivo tests were carried out in mice and consisted of measurements of the effects of the antimicrobial agents on the sizes and bacterial content of abscesses induced by subcutaneous injection of bacterial suspensions. The results of the in vivo tests were generally consistent with those obtained in vitro with strains of the B. melaninogenicus group. Synergism between gentamicin and penicillin, clindamycin, or metronidazole was shown in 13, 10, and 3 strains of this group, respectively. In vivo synergism was not clearly demonstrated with the strains of the B. fragilis group, possibly because clindamycin and metronidazole used alone were highly efficacious. We suggest that the synergistic effect of gentamicin is due to its increased transport into the bacterial cell in the presence of penicillin and, possibly, other antimicrobial agents. The newly recognized in vitro and in vivo synergism between penicillin and other antimicrobial agents and an aminoglycoside in B. melaninogenicus may have clinical implications that deserve to be investigated.
对产黑色素拟杆菌和脆弱拟杆菌群的临床分离株进行了体外和体内对青霉素、克林霉素和甲硝唑（单独使用或与庆大霉素联合使用）敏感性的测试。体外试验包括在有或无恒定剂量庆大霉素的情况下测定最低抑菌浓度（MIC）。单独使用时，庆大霉素对这些细菌的影响可忽略不计，但分别显著降低了青霉素、克林霉素和甲硝唑对15株产黑色素拟杆菌群中11株、10株和3株的MIC。15株脆弱拟杆菌群均为β-内酰胺酶产生菌，对青霉素或青霉素与庆大霉素的联合用药高度耐药。然而，庆大霉素分别降低了克林霉素和甲硝唑对该菌群中1株和7株的MIC。体内试验在小鼠中进行，包括测量抗菌药物对皮下注射细菌悬液诱导的脓肿大小和细菌含量的影响。体内试验结果与产黑色素拟杆菌群菌株的体外试验结果总体一致。庆大霉素与青霉素、克林霉素或甲硝唑之间的协同作用分别在该菌群的13株、10株和3株中得到体现。对于脆弱拟杆菌群的菌株，体内协同作用未得到明确证实，可能是因为单独使用克林霉素和甲硝唑就具有高效性。我们认为庆大霉素的协同作用是由于在青霉素及可能的其他抗菌药物存在的情况下，其进入细菌细胞的转运增加。产黑色素拟杆菌中青霉素与其他抗菌药物和氨基糖苷类药物新发现的体外和体内协同作用可能具有值得研究的临床意义。
