Comparative analysis of drug resistance rate between colonized bacteria and pathogenic bacteria isolated from respiratory tract

Objective To compare the different resistance rate to commonly used an- tibiotics between typical colonized bacteria and pathogenic bacteria isolated from respiratory tract. Methods According to certain stantard, 392 strains of typical colonized bacteria (219 strains of enterobactericaeae, 173 strains of non -fermenter) and 504 strains of typical pathogenic bacteria (323 strains of enterobactericaeae, 181 strains of non-fermenter) were se- lected from 1486 strains of gram-negative bacilli isolated from respiratory tract. Antimicrobial susceptibility of the two kinds of bacilli was tested by Kirby-Bauer method. For Escherichia coli., Klebsierlla pneumonia and Proteus mirabillis, ESBL confirmatory test was performed ac- cording to the guidelines of CLSI (2006). Results Compared with pathogenic bacteria, colo- nized bacteria had significant higher resistance rate with the exception to imipenem (enter- obactericaeae) and levofloxacin (non-fermenter), colonized bacteria showed sighificant higher ESBL positive rate than pathogenic bacteria among 426 strains of Escherichia coli., Klebsier- lla pneumonia and Proteus mirabillis. Conclusions Colonized bacteria of respiratory tract had higher ersistance rate than pathogenic bacteria. For conditioned pathogen isolated from sputum, laboratory should discriminate pathogenic bacteria from colonized bacteria.