Molecular characterization and antibiotic resistance of Acinetobacter baumannii in cerebrospinal fluid and blood.

Xiaohong Shi,Huaiqi Jing,Zhenzhou Huang,Shuai Qin,Xin Wang,Yufeng Fan,Jiazheng Wang,Ran Duan,Kyle Stirling,Dongyue Lv,Hong Wang,Lei Zhang,Iddya Karunasagar

doi:10.1371/journal.pone.0247418

Abstract

The increasing prevalence of carbapenem-resistant Acinetobacter baumannii (CRAB) caused nosocomial infections generate significant comorbidity and can cause death among patients. Current treatment options are limited. These infections pose great difficulties for infection control and clinical treatment. To identify the antimicrobial resistance, carbapenemases and genetic relatedness of Acinetobacter baumannii isolates from cerebrospinal fluid (CSF) and blood, a total of 50 nonrepetitive CSF isolates and 44 blood isolates were collected. The resistance phenotypes were determined, and polymerase chain reaction (PCR) was performed to examine the mechanisms of carbapenem resistance. Finally, multilocus sequence typing (MLST) was conducted to determine the genetic relatedness of these isolates. It was observed that 88 of the 94 collected isolates were resistant to imipenem or meropenem. Among them, the blaOXA-23 gene was the most prevalent carbapenemase gene, with an observed detection rate of 91.5% (86/94), followed by the blaOXA-24 gene with a 2.1% detection rate (2/94). Among all carbapenem-resistant Acinetobacter baumannii (CRAB) observations, isolates with the blaOXA-23 gene were resistant to both imipenem and meropenem. Interestingly, isolates positive for the blaOXA-24 gene but negative for the blaOXA-23 gene showed an imipenem-sensitive but meropenem-resistant phenotype. The MLST analysis identified 21 different sequence types (STs), with ST195, ST540 and ST208 most frequently detected (25.5%, 12.8% and 11.7%, respectively). 80 of the 94 isolates (85.1%) were clustered into CC92 which showed a carbapenem resistance phenotype (except AB13). Five novel STs were detected, and most of them belong to CRAB. In conclusion, these findings provide additional observations and epidemiological data of CSF and blood A. baumannii strains, which may improve future infection-control measures and aid in potential clinical treatments in hospitals and other clinical settings.

Highlights

Acinetobacter baumannii is a non-fermentative, Gram-negative opportunistic pathogen that often causes disease among immunocompromised patients [1]
Microbiological results identifying bacteria in cerebrospinal fluid (CSF) and blood [4, 5] are referred to as critical values because these laboratory values may indicate a possibly urgent and life-threatening situation for patients in which treatment protocols indicate a need for immediate therapy
The changes in resistance rates of imipenem were observed to decrease from 89.7% in 2016 to 89.3% in 2017, and increased to 93.8% in 2018 and 2019

Summary

Introduction

Acinetobacter baumannii is a non-fermentative, Gram-negative opportunistic pathogen that often causes disease among immunocompromised patients [1]. A. baumannii has become an important bacterium to identify when treating and controlling infectious diseases because of its remarkable ability to evolve and develop extensive drug resistance to many antibiotics [2]. The increase in the number of carbapenem-resistant Acinetobacter baumannii (CRAB) isolates has recently become a global concern. The production of carbapenemase is one of the most common and important mechanisms for A. baumannii resistance to carbapenems. Because the related coding genes are located in transferable genetic elements and can spread among A. baumannii and even into other bacteria [12, 13], New Delhi metallo-β-lactamase (NDM) and Klebsiella pneumoniae carbapenemase (KPC) producers have shown significant importance for worldwide prevalence [14, 15]

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