Department of Clinical Microbiology, Rigshospitalet, Copenhagen, Denmark.
Institute of Immunology and Microbiology, Panum Institute, University of Copenhagen, Copenhagen, Denmark.
APMIS. 2024 Dec;132(12):985-991. doi: 10.1111/apm.13405. Epub 2024 Apr 2.
Antibiotic susceptibility testing (AST) by agar diffusion has been repeatedly standardized and, in most cases, gives results which predict clinical success when antibiotic treatment is based on such results. The formation of the inhibition zone is due to a transition from planktonic to biofilm mode of growth. The kinetics of the interaction of antibiotics with bacteria is similar during AST by agar diffusion and during administration of antibiotics to the patients. However, the Mueller-Hinton agar (MHA) recommended for AST agar diffusion test is fundamentally different from the composition of the interstitial fluid in the human body where the infections take place and human cells do not thrive in MH media. Use of RPMI 1640 medium designed for growth of eucaryotic cells for AST of Pseudomonas aeruginosa against azithromycin results in lower minimal inhibitory concentration, compared to results obtained by MHA. The reason is that the RPMI 1640 medium increases uptake and reduces efflux of azithromycin compared to MHA. During treatment of cystic fibrosis patients with azithromycin, mutational resistance occur which is not detected by AST with MHA. Whether this is the case with other antibiotics and bacteria is not known but it is of clinical importance to be studied.
琼脂扩散法的抗生素药敏试验（AST）已经被反复标准化，并且在大多数情况下，当抗生素治疗基于这些结果时，会给出预测临床成功的结果。抑制带的形成是由于从浮游生长模式向生物膜生长模式的转变。在琼脂扩散法 AST 中抗生素与细菌相互作用的动力学与在给患者施用抗生素时相似。然而，推荐用于 AST 琼脂扩散试验的 Mueller-Hinton 琼脂（MHA）与发生感染的人体间质液的组成在根本上不同，人体细胞在 MH 培养基中无法茁壮成长。对于铜绿假单胞菌对抗阿奇霉素的 AST，使用为真核细胞生长设计的 RPMI 1640 培养基会导致比使用 MHA 获得的最小抑菌浓度更低。原因是 RPMI 1640 培养基与 MHA 相比，增加了阿奇霉素的摄取并减少了其外排。在使用阿奇霉素治疗囊性纤维化患者期间，会发生突变耐药性，而 MHA 的 AST 无法检测到这种耐药性。对于其他抗生素和细菌是否也是如此尚不清楚，但值得研究，因为这具有临床重要性。
