Respiratory tract pathogens isolated from patients hospitalized with suspected pneumonia: frequency of occurrence and antimicrobial susceptibility patterns from the SENTRY Antimicrobial Surveillance Program (United States and Canada, 1997)

Thirty-seven sentinel hospitals (29 in the United States [US]; eight in Can ada) collected bacterial isolates from hospitalized patients with a diagnos is of pneumonia. The antimicrobial susceptibility patterns of these pathoge ns were determined to more than 60 agents (40 reported) using the reference broth microdilution method described by the National Committee for Clinica l Laboratory Standards. The five most frequently recorded species among the 2757 isolates collected during the study were (no. tested/%): Staphylococc us aureus (632/22.9%), Pseudmonas, aeruginosa (498/18.1%), Haemophilus infl uenzae (284/10.3%), Klebsiella spp. (240/8.7%), and Streprococcus pneumonia e (213/7.7%). There was a significant difference in the susceptibility to a ntimicrobials between the US and Canada for S. aureus to oxacillin (50.1% v ersus 93.8% susceptible. respectively), gentamicin (78.7% versus 97.8%), an d fluoroquinolones (49.5 to 53.0% versus 89.8 to 94.9%). Amikacin (92.8% su sceptible) was the most active antimicrobial agent against P. aeruginosa, a nd meropenem was the most potent beta-lactam. Against H. influenzae, most d rugs retained a high level of activity, whilst against the S. pneumoniae, o nly the newer fluoroquinolones (gatifloxacin, levofloxacin, sparfloxacin) r emained highly effective in vitro. Only two antimicrobial agents (imipenem and meropenem) were >99% active against the Klebsiella spp, and Enterobacte r spp. isolated in this survey (possess extended spectrum beta-lactamases o r hyperproduction of Amp C cephalosporins); cefepime (95.6-100.0% susceptib le) was significantly more active than other cephalosporins tested. Clonal, epidemic outbreaks of multiply resistant strains were very rare in monitor ed hospitals. In conclusion, important differences exist between the US and Canada in the susceptibility patterns of some respiratory tract pathogens to commonly used antimicrobial agents with Canadian strains generally being more susceptible tn currenty available antimicorbial agents. (C) 2000 Else vier Science Inc. All rights reserved.