Norfloxacin Induced Cross-Resistance to Fluoroquinolones and Non fluoroquinolone Groups of Antimicrobial Agents in Pseudomonas aeruginosa

Abstract

Objective: To detect whether development of resistance to norfloxacin promotes development of resistance to other fluoroquinolones. Material and Methods: Four clinical and two environmental isolates of Pseudomonas aeruginosa susceptible to norfloxacin (Minimum Inhibitory Concentration in the range of 0.4µg/ml to 0.84µg/ml) were manipulated in vitro to induce resistance to norfloxacin by means of serial transfer up to 14 times through media containing increasing concentrations of norfloxacin. Results and Discussion: This in vitro manipulation of isolates of P. aeruginosa resulted in increase of MIC from 0.4µg/ml to 0.84µg/ml to 12.5µg/ml to 13.5µg/ml indicating development of resistance to norfloxacin. The antimicrobial susceptibility testing showed a major decrease in the zone diameters of pefloxacin and ofloxacin, and significant decrease in the zone diameters of ciprofloxacin indicating development of cross resistance to other fluoroquinolones. No appreciable change in the zone diameters of non fluoroquinolone groups of antimicrobial agents indicating no development of resistance to structurally unrelated antibiotics. Conclusions: These results indicate that development of resistance to norfloxacin promotes development of resistance to other fluoroquinolones.

A Newer in Vitro Model for the Study of Development of in vitro resistance to penicillin in a novel isolate of Streptococcus tigurinus

“…Development of resistance to penicillin and cross-resistance to other antibiotics during therapy has been frequently reported in viridans group streptococci (VGS) [4][5][6][7] but in vitro studies are mostly overlooked and rarely reported in VGS. However, in vitro studies on development of resistance are commonly reported in Staphylococcus aureus and Pseudomonas aeruginosa [8][9][10][11]. The in vitro development of resistance to penicillin has been reported in other species of VGS in our previous study [12] but the in vitro development of resistance to penicillin in S. tigurinus has not been studied and reported so far.…”

“…[4][5][6][7], but the reports on in vitro development of resistance to penicillin in VGS are very rare. Although commonly studied and reported in S. aureus and P. aeruginosa to a variety of antimicrobial agents [8][9][10][11], it is very rarely studied and reported in VGS. No previous reports are available on in vitro development of resistance in VGS except for one reported by us [12].…”