Global infections with colistin-resistant Pseudomonas aeruginosa (CoR-PA) are increasing; there are currently very few studies focused on the antimicrobial susceptibility of CoR-PA isolates, and none from Thailand. Here, we investigated the impact of various antimicrobials, alone and in combination, via the in vitro testing of CoR-PA clinical isolates. Eighteen CoR-PA isolates were obtained from patients treated at Phramongkutklao Hospital from January 2010 through June 2019; these were classified into six different clonal types by using the enterobacterial repetitive intergenic consensus (ERIC)-PCR method, with a high prevalence of Group A (27.8%). The antimicrobial susceptibility was determined as the minimal inhibitory concentrations (MICs) using the epsilometer-test (E-test) method. The synergistic activities of six antimicrobial combinations were reported via the fractional-inhibitory-concentration index. All CoR-PA isolates were susceptible to amikacin, meropenem, and ceftolozane/tazobactam, but only 5.56% were susceptible to imipenem. In vitro synergistic activities were detected for amikacin with aztreonam, piperacillin/tazobactam, meropenem, and ceftazidime for 16.67%, 11.11%, 11.11%, and 5.55%, respectively. One CoR-PA isolate carried the bla_VIM metallo-β-lactamase gene; none carried mcr-1 genes or detected plasmid-mediated AmpC β-lactamase or an overproduction of chromosomal AmpC β-lactamase. Seven CoR-PA isolates (38.89%) were capable of biofilm formation. In conclusion, CoR-PA isolates are highly susceptible to antimicrobials; the synergy observed in response to the various agents should be examined in a clinical setting.

中文翻译：

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在泰国的大学医院中，抗细菌药作为单药和联合疗法用于抵抗共价霉素的铜绿假单胞菌。

大肠杆菌抵抗铜绿假单胞菌的全球感染（CoR-PA）在增加；目前，很少有研究针对CoR-PA分离物的抗菌敏感性，而泰国也没有。在这里，我们通过体外测试CoR-PA临床分离株，研究了单独使用或联合使用的各种抗菌药物的影响。从2010年1月至2019年6月在Phramongkutklao医院接受治疗的患者中获得了18株CoR-PA分离株。通过肠细菌重复基因间共有（ERIC）-PCR方法将它们分为六种不同的克隆类型，A组的患病率很高（27.8％）。抗菌药敏度通过最小二乘试验（E-test）方法确定为最低抑菌浓度（MIC）。通过分数抑制浓度指数报告了六种抗菌药物组合的协同活性。所有CoR-PA分离株均对丁胺卡那霉素，美洛培南和头孢洛赞/他唑巴坦敏感，但仅5.56％对亚胺培南敏感。阿米卡星与氨曲南，哌拉西林/他唑巴坦，美洛培南和头孢他啶的体外协同活性分别为16.67％，11.11％，11.11％和5.55％。一种CoR-PA分离株带有bla _VIM金属β-内酰胺酶基因；没有人携带mcr-1基因或检测到质粒介导的AmpCβ-内酰胺酶或染色体AmpCβ-内酰胺酶的过量生产。七个CoR-PA分离株（38.89％）能够形成生物膜。总之，CoR-PA分离株对抗生素高度敏感。在临床环境中应检查观察到的对各种药物反应的协同作用。