Assessment of antibiotic resistance in bacteriophage-insensitive Klebsiella pneumoniae.

This study was design to evaluate the physiological properties of bacteriophage-insensitive Klebsiella pneumoniae (BIKP) mutants in association with the antibiotic cross-resistance, β-lactamase activity, and gene expression. Klebsiella pneumoniae ATCC 23357(KP), ciprofloxacin-induced antibiotic-resistant K. pneumoniae ATCC 23357 (KP), and clinically isolated antibiotic-resistant K. pneumoniae 10263 (KP) were used to isolate BIKP mutants against KPB1, PBKP02, PBKP21, PBKP29, PBKP33, and PBKP35. PBKP35-induced mutants, including bacteriophage-insensitive K. pneumoniae ATCC 23357 (BIKP), ciprofloxacin-induced K. pneumoniae ATCC 23357 (BIKP), and clinically isolated antibiotic-resistant K. pneumoniae CCARM 10263 (BIKP). BIKP, BIKP, and BIKP were resistant to Klebsiella bacteriophages, KPB1, PBKP02, PBKP21, PBKP29, and PBKP33. The antibiotic cross-resistance to cefotaxime, cephalothin, chloramphenicol, ciprofloxacin, erythromycin, kanamycin, levofloxacin, and nalidixic acid was observed in BIKP. The relative expression levels of vagC was increased by more than 8-folds in BIKP, corresponding to the increased β-lactamase activity. The aac(6')-Ib-cr was overexpressed in BIKP mutants, responsible for aminoglycoside and quinolone resistance. The phage-resistant mutants decreased the antibiotic susceptibilities in association with β-lactamase activity and antibiotic resistance-related gene expression. The results pointed out the cross-resistance of BIKP mutants to antibiotics, which might be considered when applying for the therapeutic use of bacteriophage.