Fluoroquinolone antibiotics: in vitro antibacterial and time-kill bactericidal evaluation against etiology of bacteremia in human immunodeficiency virus (HIV)-infected patients

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Background Bacteremia constitutes a significant public health challenge and represents a vital cause of morbidity and mortality in HIV-infected patients, and fluoroquinolones are commonly prescribed antibiotics due to their range of activities and pharmacokinetic profiles. This study the evaluated antibacterial activities and time-kill kinetics of fluoroquinolone antibiotics: Ofloxacin (OFL), Ciprofloxacin (CIP) and Levofloxacin (LEV) against the etiology of bacteremia of genera Staphylococcus, Streptococcus, Acinetobacter, Pseudomonas, Klebsiella, Haemophilus, Enterobacter , and Salmonella using disc diffusion, micro-broth dilution and plate count techniques. Results The lowest mean growth inhibition zones (mm ± SD) of OFL, LEV, and CIP against the isolates were 10.5 ± 0.0, 10.1 ± 0.1 and 9.6 ± 0.3, respectively. The MIC values of OFL, LEV and CIP on isolates ranged from 6.25 to > 50 µg/mL, MBC ranged from 12.5 to > 50 µg/mL, while MBC/MIC ratios were ≤ 2. The time-kill assay revealed that logarithmic reductions in viable cell counts (Log 10 CFU/mL) of bacteria exposed to OFL, LEV and CIP ranged from 0.17 to 2.14 for P. aeruginosa ; 0.13 to 1.31 for H. influenzae ; 0.04 to 2.23 for Acinetobacter spp; and 0.08 to 2.08 for K. pneumoniae. LEV and OFL (1 × MIC concentration) achieved bactericidal effects on S. typhi ST07 and E. aerogenes EA01 at 30 h post-inoculation, respectively, while ≥ 99.9% reduction in the number of viable K. pneumoniae cells exposed to CIP was achieved at 24 h post-inoculation. Conclusion The fluoroquinolones demonstrated higher inhibitory activities at higher concentrations against the etiology of bacteremia in HIV-infected patients, signifying a concentration-dependent inhibition of bacterial growth. The MIC-based time-kill curve analyses showed that LEV achieved 3 Log 10 -fold reduction (≥ 99.9% reduction) in CFU/mL of most etiology of bacteremia faster compared with the other two fluoroquinolones.