Change of bacterial pathogens in lower respiratory tract infection during 1995-2004

Objective To investigate the change of distribution and antibiotic susceptibility of pathogenic bacteria isolated from inpatients with lower respiratory tract infection in Department of Respiratory Medicine during 1995-2004. Methods All the clinical isolates from sputum or secretion of lower respiratory tract from 1995 to 2004 were analyzed retrospectively. Antibiotic susceptibility was tested by Kirby-Bauer method. Results were interpreted according to NCCLS breakpoints. Results A total of 2 158 clinical isolates were collected, including 1 832 (84.9%) strains of gram-negative bacilli and 326 (15.1%) strains of gram-positive cocci. The most important gram-negative pathogens were Pseudomonas aeruginosa, Klebsiella pneumoniae, Acinetobacter baumanii and Escherichia coli. The most common gram-positive cocci were Staphylococcus aureus and Streptococcus pneumoniae. The proportion of gram-positive microorganisms increased relatively since the year of 2000 as compared to the second half of 1990s, while the proportion of gram-negative microorganism decreased gradually. Most strains of gram-negative bacilli were susceptible to meropenem and cefoperazone-sulbactam. P. aeruginosa isolates were relatively susceptible to amikacin, but highly resistant to cefotaxime and ceftriaxone. The resistance of K. pneumoniae to ceftazidime, cefoperazone, cefotaxime and ceftriaxone were lower than that of P. aeruginosa. The major gram-positive isolates were highly resistant to azithromycin, erythromycin and clindamycin. All S. aureus isolates were susceptible to vancomycin. S. pneumoniae isolates were highly susceptible to meropenem and levofloxacin. Conclusions Gram-negative bacilli are still the leading pathogens in lower respiratory tract infection during the past 10 years in our Department of Respiratory Medicine, but there is a trend showing that the proportion of gram-negative isolates is decreasing. Antibiotic resistance becomes more prevalent in some major pathogens. Rational use of antibiotics is important for the containment of bacterial resistance.