Department of Microbiology and Samsung Medical Center, Sungkyunkwan University School of Medicine, Suwon, 16419, Republic of Korea.
Division of Infectious Diseases, Samsung Changwon Hospital, Sungkyunkwan University School of Medicine, Changwon, 51353, Republic of Korea.
J Microbiol. 2021 Jun;59(6):590-597. doi: 10.1007/s12275-021-0610-1. Epub 2021 Mar 29.
Although colistin is frequently regarded as the antibiotic of last resort in treating carbapenem-resistant Klebsiella pneumoniae, colistin heteroresistance may in part be associated with antibiotic treatment failure. However, we do not know how widespread the colistin heteroresistance is in carbapenem-resistant K. pneumoniae isolates. In this study, we performed colistin disc diffusion assays, E-tests, and population analysis profiling for KPC-2-producing K. pneumoniae isolates to identify colistin heteroresistance. Although no colistin-resistant colonies were detected by the disc diffusion test and E-test, a colistin-resistant subpopulation was identified in population analysis profiling in all colistin-susceptible, KPC-2-producing K. pneumoniae isolates. Colistin-resistant subpopulations were also identified even when isolates had no colistin exposure. The ratio of colistin-resistant subpopulations to the total population increased as the exposure concentration of colistin increased. In in vitro time-kill assays, regrowth was observed in all isolates after 2 h upon exposure to colistin. We identified common amino acid alterations in PhoQ, PhoP, and PmrB in colistin-resistant subpopulations from some isolates, but no substitutions were found in most resistant subpopulations from other isolates. In all colistin-resistant subpopulations, overexpression of PhoQ and PbgP was observed. In this study, we demonstrated that colistin heteroresistance may be common in KPC-2-producing K. pneumoniae isolates, which could not be detected in the disc diffusion method and E-test. Colistin heteroresistance may cause colistin treatment failure in part and may evolve into resistance. Thus, development of more reliable diagnostic methods is required to detect colistin heteroresistance.
虽然多黏菌素通常被认为是治疗碳青霉烯类耐药肺炎克雷伯菌的最后手段抗生素，但多黏菌素异质性耐药可能部分与抗生素治疗失败有关。然而，我们不知道碳青霉烯类耐药肺炎克雷伯菌分离株中的多黏菌素异质性耐药有多普遍。在这项研究中，我们对产 KPC-2 的肺炎克雷伯菌分离株进行了多黏菌素药敏纸片扩散法、E 试验和群体分析，以鉴定多黏菌素异质性耐药。尽管药敏纸片扩散法和 E 试验未检测到多黏菌素耐药菌落，但在所有多黏菌素敏感、产 KPC-2 的肺炎克雷伯菌分离株的群体分析中均鉴定出多黏菌素耐药亚群。即使在分离株没有接触多黏菌素的情况下，也鉴定出了多黏菌素耐药亚群。多黏菌素耐药亚群与总群体的比例随着多黏菌素暴露浓度的增加而增加。在体外时间杀伤试验中，在接触多黏菌素 2 小时后，所有分离株均观察到再生。我们在一些分离株的多黏菌素耐药亚群中鉴定出 PhoQ、PhoP 和 PmrB 的常见氨基酸改变，但在大多数其他分离株的耐药亚群中未发现取代。在所有多黏菌素耐药亚群中，均观察到 PhoQ 和 PbgP 的过度表达。在这项研究中，我们证明多黏菌素异质性耐药可能在产 KPC-2 的肺炎克雷伯菌分离株中很常见，这在药敏纸片扩散法和 E 试验中无法检测到。多黏菌素异质性耐药可能部分导致多黏菌素治疗失败，并可能演变为耐药性。因此，需要开发更可靠的诊断方法来检测多黏菌素异质性耐药。
