Faculty of Veterinary, Department of Animal Health, Universidad Complutense de Madrid, Laboratory 206, Puerta de Hierro s/n, 28040 Madrid, Spain.
Servicio de Microbiología, Hospital Universitario La Paz, IdiPAZ, Madrid, Spain.
Int J Antimicrob Agents. 2017 Jun;49(6):727-733. doi: 10.1016/j.ijantimicag.2017.01.031. Epub 2017 Apr 21.
Acinetobacter baumannii is a highly versatile nosocomial pathogen. Multidrug resistance among A. baumannii isolates led to the use of colistin, subsequently giving rise to colistin-resistant strains. In this study, the genetic and phenotypic profiles of two colistin-resistant A. baumannii isolates were investigated. Two A. baumannii isolates were obtained from Patient 1 (C071 and C440) and three isolates were obtained from Patient 2 (C080, C314 and C428). Susceptibility profiles were determined by VITEK2 and Etest. Clonality was determined by RAPD analysis and trilocus multiplex PCR. The pmrCAB operon was sequenced and common carbapenemase genes were screened for by PCR. Doubling times, haemolysis, surface motility, biofilm formation, siderophore production and proteolytic activity were phenotypically determined. Finally, whole-genome sequencing was performed for all five isolates. Isolates C440 and C428 were resistant to colistin and were clonally identical to their sensitive counterparts. The cause of colistin resistance was traced to the previously described P233S mutation in pmrB of C440 and to a novel ΔI19 mutation in pmrB of C428. bla and bla from the strains of Patients 1 and 2, respectively, were also detected. C440 had attenuated proteolytic activity and was positive for siderophore production compared with C071. No difference in in vitro virulence was detected between isolates C080, C314 and C428. In conclusion, one common and one novel mutation were encountered in pmrB from two distinct colistin-resistant A. baumannii isolates. These mutations caused colistin resistance during therapy in two distinct clones, and only one of them had altered in vitro virulence.
鲍曼不动杆菌是一种高度多功能的医院病原体。鲍曼不动杆菌分离株的多药耐药性导致了黏菌素的使用，随后产生了黏菌素耐药株。在这项研究中，研究了两株耐黏菌素的鲍曼不动杆菌分离株的遗传和表型特征。从患者 1 中获得了两株鲍曼不动杆菌分离株（C071 和 C440），从患者 2 中获得了三株分离株（C080、C314 和 C428）。通过 VITEK2 和 Etest 测定药敏谱。通过 RAPD 分析和三基因多重 PCR 确定克隆性。测序 pmrCAB 操纵子并通过 PCR 筛选常见碳青霉烯酶基因。通过表型测定倍增时间、溶血、表面运动性、生物膜形成、铁载体产生和蛋白水解活性。最后，对所有五个分离株进行全基因组测序。分离株 C440 和 C428 对黏菌素耐药，与敏感株具有相同的克隆性。黏菌素耐药的原因可追溯到 C440 中 pmrB 的先前描述的 P233S 突变，以及 C428 中 pmrB 的新型 ΔI19 突变。还分别从患者 1 和 2 的菌株中检测到 blaOXA-23 和 blaOXA-58。与 C071 相比，C440 的蛋白水解活性减弱，且铁载体产生呈阳性。在体外毒力方面，C080、C314 和 C428 之间未检测到差异。总之，在两个不同的耐黏菌素鲍曼不动杆菌分离株的 pmrB 中发现了一个共同的和一个新的突变。这些突变导致了两种不同克隆在治疗过程中的黏菌素耐药性，只有其中一种改变了体外毒力。
