Post Neurosurgical Meningitis due to Colistin Heteroresistant Acinetobacter baumannii

Abstract

Introduction:Recently Acinetobacter baumannii isolates have emerged as a problematic infectious agent that causes meningitis in neurosurgical patients. Colistin has been used successfully for the treatment of A. baumannii meningitis but colistin resistant isolates have been reported worldwide.Case Presentation:Two isolates of A. baumannii were cultured during a five-day period from cerebrospinal fluid (CSF) samples of a 20-year-old man with a gunshot trauma in the abdomen, which had exited from his back. Antimicrobial susceptibility tests of isolates were performed. Multiplex PCR was performed for detection of blaOXA-23-like, blaOXA-24-like and blaOXA-58-like genes. Metallo-β-lactamase genes such as: blaVIM, blaIMP, blaSPM and blaNDM were sought by singleplex PCR. In order to evaluate the genetic relationship, two isolates were examined by the repetitive extragenic palindromic-polymerase chain reaction (REP_PCR) method.Conclusions:E-test results showed that the isolates were sensitive to colistin and tigecycline with minimum inhibitory concentration of (MIC) 0.25 µg/mL and 1.5 µg/mL, respectively. Secondly the isolates were resistant to colistin with MIC > 256 µg/mL but remained sensitive to tigecycline with MIC 1.5 µg/mL. On the basis of the multiplex PCR, both of the isolates were positive for blaOXA-23-like. Other investigated genes such as blaOXA-24-like, blaOXA-58-like, blaVIM, blaIMP, blaSPM and blaNDM were negative. REP-PCR results showed that two isolates were derived from a single strain and both were the same. The results of our study revealed that the firs isolate of A. baumannii was colistin heteroresistant and was changed to completely resistant during therapy. Diagnosis and treatment of A. baumannii meningitis is very important and to avoid treatment failure we suggest that all A. baumannii isolates obtained from CSF should be evaluated properly for colistin heteroresistance.

Acquisition of Colistin Resistance Links Cell Membrane Thickness Alteration with a Point Mutation in the lpxD Gene in Acinetobacter baumannii

“…A similar phenotype has also been described in clinical isolates of Stenotrophomonas maltophilia [29] and carbapenem-resistant A. baumannii [30]. Curiously, this phenomenon has enhanced colistin resistance in A. baumannii [31], an issue that is now of great interest, since colistin is the drug of choice for A. baumannii therapy [32][33][34] To answer the question of whether this phenotypic manifestation has a genetic basis, further investigation is required, including genomic sequencing. Choi and Ko stated that the two-component gene system PmrA/B is associated with the emergence of colistin heteroresistance in A.baumannii [35].…”

Investigation of Colistin Heteroresistance and Some Factors Affecting Heteroresistance in Carbapenem-Resistant A. baumannii Strains

“…Later, in their studies in Argentine, Rodriguez et al [19] Rodriguez et al [20] have found 46% and 43% heteroresistance rates in 2009 and 2010, respectively. In their case report, Moosavian et al [10] have recently demonstrated post neurosurgical meningitis due to colistin heteroresistant A. baumannii. They have also reported the generation of colistin resistant A. baumannii from colistin susceptible-heteroresistant strains during colistin therapy.…”

“…Heteroresistance to carbapenems has been reported in A. baumannii, and it is believed to be the cause of increasing CR A. baumannii in Greece [1,9] . Recently, Moosavian et al [10] have reported a case of meningitis due to colistin heteroresistant A. baumannii and observed colistin resistance development during treatment with colistin.…”

In vitro activity of methylene blue and EMB agar on colistin-resistant A.baumannii: An experimental study

“…Various studies from clinical settings throughout the world have indicated the emergence of colistin-resistant AB as an important healthcare problem [10,14]. Colistin-susceptible AB strains can easily transform into colistin-resistant or heteroresistant clones, or colistin heteroresistant strains can transform into colistin-resistant clones via exposure to colistin [15][16][17][18]. In 2016, the emergence of plasmid-mediated colistin resistance in an E. coli strain by the MCR-1 mechanism was reported from China, which made scientists focus on the urgent need for global action in the fight against pan-drug-resistant Gram-negative bacteria [19].…”