Genteluci Gabrielle Limeira, de Souza Paula Araujo, Gomes Daniela Betzler Cardoso, Sousa Verônica Santos, de Souza Maria José, Abib José Roberto Lannes, de Castro Eduardo Almeida Ribeiro, Rangel Karyne, Villas Bôas Maria Helena Simões
Department of Microbiology, National Institute of Quality Control in Heath, Fiocruz, Rio de Janeiro, Brazil.
Post-Graduation Program in Health Surveillance, National Institute of Quality Control in Heath, Fiocruz, Rio de Janeiro, Brazil.
Curr Microbiol. 2020 Sep;77(9):2300-2306. doi: 10.1007/s00284-020-02064-6. Epub 2020 Jun 3.
Acinetobacter baumannii is an emerging pathogen associated with nosocomial infections and multidrug resistance. Polymyxin B has been used to treat infections caused by multidrug-resistant (MDR) A. baumannii but an increase in polymyxin B resistance has been observed. We aimed to determine the diversity, antimicrobial susceptibility, presence of polymyxin B heteroresistance and adaptive resistance in 72 A. baumannii clinical isolates from two public hospitals in Rio de Janeiro. The isolates were identified by sequencing of rpoB gene. Determination of the genetic diversity of isolates was performed by pulsed-field gel electrophoresis and oxacillinases genes were detected by polymerase chain reaction. The polymyxin B heteroresistance was analyzed by population analysis profile and adaptive resistance was evaluated after serial daily passages of isolates in broth containing increasing polymyxin B concentrations. The results showed that 49% of the isolates were collected from respiratory system and 62% were MDR, while 35% were extensively drug resistant. Additionally, all the isolates carried bla, bla genes and ISAba1, while 1% had bla gene. The association of ISAba1-bla was found in 96% of the isolates. Polymyxin B heteroresistance was found in 36% of the isolates and polymyxin B adaptive resistance was not found in the isolates. Our study demonstrated the high resistance to antimicrobials used in clinical practice and the spread of oxacillinases genes and insertion sequence (IS). We also reported the presence of heteroresistance to polymyxin B used as a last-resort therapy for MDR A. baumannii.
鲍曼不动杆菌是一种与医院感染和多重耐药性相关的新兴病原体。多粘菌素B已被用于治疗由多重耐药（MDR）鲍曼不动杆菌引起的感染，但已观察到多粘菌素B耐药性有所增加。我们旨在确定来自里约热内卢两家公立医院的72株鲍曼不动杆菌临床分离株的多样性、抗菌药物敏感性、多粘菌素B异质性耐药和适应性耐药情况。通过rpoB基因测序鉴定分离株。通过脉冲场凝胶电泳确定分离株的遗传多样性，并通过聚合酶链反应检测青霉素酶基因。通过群体分析图谱分析多粘菌素B异质性耐药，并在含有递增多粘菌素B浓度的肉汤中对分离株进行每日连续传代后评估适应性耐药。结果显示，49%的分离株来自呼吸系统，62%为多重耐药，而35%为广泛耐药。此外，所有分离株均携带bla、bla基因和ISAba1，而1%携带bla基因。96%的分离株中发现了ISAba1-bla的关联。36%的分离株中发现了多粘菌素B异质性耐药，分离株中未发现多粘菌素B适应性耐药。我们的研究证明了临床实践中使用的抗菌药物存在高耐药性以及青霉素酶基因和插入序列（IS）的传播。我们还报告了作为治疗多重耐药鲍曼不动杆菌的最后手段的多粘菌素B存在异质性耐药。
