Antimicrobial susceptibility among Acinetobacter calcoaceticus-baumannii complex and Enterobacteriaceae collected as part of the Tigecycline Evaluation and Surveillance Trial.
OBJECTIVE
To measure the in vitro activity of a panel of antimicrobial agents against gram-negative pathogens collected from the nine census regions of the USA.


METHODS
Isolates were collected from 76 centers between January 2004 and September 2005. In vitro activity was assessed using CLSI guidelines and CLSI or FDA interpretive criteria.


RESULTS
The lowest overall antimicrobial susceptibilities for Acinetobacter calcoaceticus-baumannii complex isolates (n=851) were detected in the Middle Atlantic and East South Central regions. Overall, 29.3% of A. calcoaceticus-baumannii complex isolates were multidrug-resistant (resistant to > or =3 antimicrobial classes). Tigecycline (2 microg/mL) had the lowest MIC90 against this organism. Imipenem, tigecycline, and levofloxacin had low MIC90s (0.25-4 microg/mL) against Enterobacter spp. (n=1557), although the MIC90 for levofloxacin was elevated for East South Central region isolates (> or = 16 microg/mL). Susceptibility to levofloxacin among the E. coli isolates (n=1785) ranged from 71.7% (Pacific) to 88.5% (New England). The prevalence of ESBL-producing K. pneumoniae (126/1460) varied from 1.7% of isolates (Pacific) to 21.2% (Middle Atlantic). ESBL-producing K. pneumoniae MICs were lowest for imipenem and tigecycline.


CONCLUSIONS
Antimicrobial susceptibility varies among the census regions of the USA. The broad-spectrum in vitro activity of tigecycline may make it a suitable candidate for use in the empiric treatment of serious infections.
Halstead
Diane C
DC
Jacksonville Pathology Associates, P.A., Jacksonville, FL, USA. diane.halstead@bmcjax.com
Abid
Joan
J
Dowzicky
Michael J
MJ
D040981:Acinetobacter baumannii / Q000145:classification / Q000187:drug effects*; D016954:Acinetobacter calcoaceticus / Q000145:classification / Q000187:drug effects*; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D024881:Drug Resistance, Bacterial; D004755:Enterobacteriaceae / Q000145:classification / Q000187:drug effects*; D006801:Humans; D008826:Microbial Sensitivity Tests / Q000379:methods / Q000592:standards; D008911:Minocycline / Q000031:analogs & derivatives* / Q000494:pharmacology; D011159:Population Surveillance; D000078304:Tigecycline
D000900:Anti-Bacterial Agents; D000078304:Tigecycline; D008911:Minocycline