Determination of fluoroquinolones concentration among biofilm-forming and non-forming uropathogenic Acinetobacter Calcoaceticus-Baumannii complex and their correlation to fluoroquinolone-resistant genes

Acinetobacter spp., the predominant cause of urinary tract infection (UTI), is increasingly resistant to fluoroquinolones. Resistance to fluoroquinolones poses a serious health problem in the treatment of urinary tract infections, which are mostly associated with chromosomal mutations encoded by topoisomerase IV. The objective of the study was to detect the blaOXA-23, qnrB, and acc(6l)-lb-cr genes in fluoroquinolone-resistant biofilm-producing ACB complex isolated from UTI-suspected patients.

A hospital-based cross-sectional study was carried out at the Nepal Police Hospital, Kathmandu, from April 2019 to January 2021. A total of 598 urine specimens were processed, and 78 ACB complex were isolated from a total of 366 positive cultures, which were identified based on colony morphology, Gram’s staining reaction, and various biochemical tests. The antimicrobial susceptibility pattern was determined by the modified Kirby-Bauer disk diffusion method, and the result was interpreted according to CLSI guidelines. The minimum inhibitory concentration (MIC) values of levofloxacin and ciprofloxacin for fluoroquinolone-resistant ACB were determined by the broth dilution method. The fluoroquinolone-resistant ACB was selected for blaOXA-23, qnrB, and acc(6l)-lb-cr gene detection by polymerase chain reaction.

ACB complex was isolated more in females 26 (55.31%); outpatients 42 (53.84); and in the age group of 21–40 years 27 (34.61%). The majority of ACB complex isolates were sensitive to Ciprofloxacin 5 (6.41%) and Levofloxacin 10 (12.82%). However, most of them were resistant to Ciprofloxacin 64 (82.05%) and Levofloxacin 60 (76.92%). A total of 78 (21.31%) ACB complex isolates were found to be multidrug resistant. The MICs of Ciprofloxacin and Levofloxacin ranged from 4 to 256 μl/ml. Among 78 (82.05%) fluoroquinolone-resistant ACB isolates, the blaOXA-23 gene was found on 32 (41.02%) isolates, the acc(6l)-Ib-cr gene on 3 (3.84%) isolates, and the qnrB gene on 1 (1.28%) isolates.

The presence of blaOXA-23, acc(6l)-Ib-cr, and qnrB genes and biofilm formation lead to the emergence of fluoroquinolone-resistant strains of the ACB complex. So, the identification of responsible genes is required for AMR surveillance and guidelines for empirical therapy, which aid in preventing the emergence of antibiotic-resistant isolates.