Propranolol, chlorpromazine and diclofenac restore susceptibility of extensively drug-resistant (XDR)-Acinetobacter baumannii to fluoroquinolones

Abstract

Nosocomial infections caused by extensively drug-resistant (XDR) or Pan-Drug resistant (PDR) Acinetobacter (A.) baumannii have recently increased dramatically creating a medical challenge as therapeutic options became very limited. The aim of our study was to investigate the antibiotic-resistance profiles and evaluate the various combinations of ciprofloxacin (CIP) or levofloxacin (LEV) with antimicrobial agents and non-antimicrobial agents to combat antimicrobial resistance of XDR A. baumannii. A total of 100 (6.25%) A. baumannii clinical isolates were recovered from 1600 clinical specimens collected from hospitalized patients of two major university hospitals in Upper Egypt. Antimicrobial susceptibility tests were carried out according to CLSI guidelines. Antimicrobial susceptibility testing of the respective isolates showed a high percentage of bacterial resistance to 19 antimicrobial agents ranging from 76 to99%. However, a lower percentage of resistance was observed for only colistin (5%) and doxycycline (57%). The isolates were categorized as PDR (2; 2%), XDR (68; 68%), and multi-drug resistant (MDR) (30; 30%). Genotypic analysis using ERIC-PCR on 2 PDR and 32 selected XDR isolates showed that they were not clonal. Combinations of CIP or LEV with antibiotics (including, ampicillin, ceftriaxone, amikacin, or doxycycline) were tested on these A. baumannii non-clonal isolates using standard protocols where fractional inhibitory concentrations (-FICs) were calculated. Results of the respective combinations showed synergism in 23.5%, 17.65%, 32.35%, 17.65% and 26.47%, 8.28%, 14.71%, 26.47%, of the tested isolates, respectively. CIP or LEV combinations with either chlorpromazine (CPZ) 200 μg/ml, propranolol (PR) in two concentrations, 0.5 mg/ml and 1.0 mg/ml or diclofenac (DIC) 4 mg/ml were carried out and the MIC decrease factor (MDF) of each isolate was calculated and results showed synergism in 44%, 50%, 100%, 100% and 94%, 85%, 100%, 100%, of the tested isolates, respectively. In conclusion, combinations of CIP or LEV with CPZ, PR, or DIC showed synergism in most of the selected PDR and XDR A. baumannii clinical isolates. However, these combinations have to be re-evaluated in vivo using appropriate animal models infected by XDR- or PDR- A. baumannii.

Fig 1. Frequencies of A. baumannii isolates from patients with different clinical samples.

CVC: Central Venus Catheters. ETT: Endotracheal tube, UTC: Urinary Tract Catheter.

Fig 2. PCR amplification of bla_OXA-51 like gene in some A. baumannii clinical isolates, lane M, a gene ruler 100 bp ladder; lane 1, a positive control; lane 2, a negative control; lanes 3 to 11, positive results with an expected size of 353 bp; lane 12, negative results.

Fig 3. Antimicrobial susceptibility testing of A. baumannii isolates (n = 100).

IMP: Imipenem, MEM: Meropenem, PRL: Piperacillin, TZP: Tazopactam/Piperacillin, SAM: Sulbactam/Ampicillin, CAZ: Ceftazidime, CTX; Cefotaxime, CRO: Ceftriaxone, FEP: Cefepime, AK; Amikacin, CN: Gentamicin, TOB: Tobramycin, CIP: Ciprofloxacin, GAT: Gatifloxacin, LEV: Levofloxacin, SXT: Sulfamethoxazole/Trimethoprim, CT: Colistin, TGC: Tigecycline, DO: Doxycycline.

Fig 4. Phenotypic analysis of the recovered A. baumannii isolates (n = 100).

MDR (Multi-Drug resistant), XDR; extensively–Drug-resistant and PDR (Pan-Drug resistant).

Fig 5. Antimicrobial agents resistance profiles scored for different A. baumannii isolates.

Fig 6. ERIC-PCR dendrogram analysis for 34 A. baumanni was constructed by the UPGMA clustering method.

Percent of similarity among the 34 isolates of A. baumannii were calculated by using Jaccard's Coefficient using Bionumeric program software.