Objective To investigate the condition of common Gram-negative bacilli producing
AmpC β-lactamases or AmpC β-lactamases
plus extended-spectrum β-lactamases (ESBLs) in the lower respiratory tract infection, and to detect the
antibacterial activity in vitro of 13 antibiotics against them, for guiding the rational use of antibiotics.Methods
AmpC β-lactamases and were detected by three-dimensional extraction test, and the minimal inhibitory concentrations (MICs) were determined by standard agar dilution method. Results Among 266 isolates resistant to the first, second and at least one third-generation cephalosporins from clinical sputum samples, including E.cloacae, C.freundii, K.penumoniae, E.coli, A.baumannii and P.aeruginosa, producing AmpC β-lactamases and AmpC β-lactamases plus ESBLs were 34 strains (15.0%) and 15 strains (6.6%) respectively. The susceptible rate of producing either AmpC β-lactamases or AmpC β-lactamases plus ESBLs strains to the third-generation cephalosporins, aztreonam and cefmetazole were 0～14.7%; to those of antibiotics combined with inhibitors such as piperacillin/tazobactam, amoxicillin/clavulanic acid and cefoperazone/sulbactam were 0～29.4%; to ciprofloxacin and levofloxacin all were 71.4% except E.coli; to imipenem was 97.1% except one strain P.aeruginosa. The susceptible rate of AmpC β-lactamases and AmpC β-lactamases plus ESBLs producing strains to cefepime and amikacin were 97.1% and 64.7%, 66.7% and 26.7% respectively. Conclusion The antibacterial activity of imipenem against AmpC β-lactamases and/or AmpC β-lactamases plus ESBLs producing strains is strong, and also those of ciprofloxacin and levofloxacin are better except E.coli. As to cefepime, the antibacterial activity against which only producing AmpC β-lactamases is also strong, and amikacin has displayed a moderate activity.