Major article
Distribution of resistant gram-positive organisms across the census regions of the United States and in vitro activity of tigecycline, a new glycylcycline antimicrobial

https://doi.org/10.1016/j.ajic.2006.11.004Get rights and content

Background

Gram-positive isolates were collected from 76 medical centers within the 9 census regions across the United States.

Methods

Antimicrobial susceptibilities were determined according to Clinical and Laboratory Standards Institute guidelines.

Results

Vancomycin resistance among Enterococcus faecium isolates varied from 45.5% (New England) to 85.3% (East South Central). The lowest concentrations at which 90% of the isolates were inhibited (MIC90) were for tigecycline (0.06-0.12 μg/mL) and for linezolid (2-4 μg/mL). Methicillin-resistant Staphylococcus aureus (MRSA) varied from 27.4% (New England) to 62.4% (East South Central). All MRSA were susceptible to tigecycline, linezolid, and vancomycin. Penicillin-nonsusceptible Streptococcus pneumoniae ranged from 23.3% in the Pacific region to 54.5% in the East South Central region. Tigecycline, imipenem, levofloxacin, linezolid, and vancomycin all maintained MIC90 of ≤1 μg/mL against penicillin-nonsusceptible S pneumoniae in vitro, irrespective of region.

Conclusion

This study demonstrates the variable rate of antimicrobial-resistant gram-positive organisms in the United States. Tigecycline may make a useful addition to the antimicrobial armamentarium.

Section snippets

Bacterial isolates

Isolates were collected between January 2004 and September 2005 from 76 medical centers within the 9 census regions across the United States: Pacific (5 centers), Mountain (4 centers), West North Central (5 centers), East North Central (12 centers), Middle Atlantic (14 centers), New England (6 centers), South Atlantic (17 centers), East South Central (6 centers), and West South Central (7 centers). Medical centers were selected based on demographic and geographic diversity, and all centers

E faecalis

Of the 740 E faecalis isolates collected as part of the T.E.S.T. study, a total of 35 (4.7%) were identified as vancomycin resistant. These 35 isolates were collected from 8 of the 9 census regions (none collected from the Pacific region; Fig 1).

Enterococcus faecium

A total of 280 isolates of E faecium were collected across the United States, of which 67.9% were vancomycin resistant. Vancomycin-resistant E faecium were identified in each of the census regions, ranging from 45.5% (New England) to 85.3% (East South

Discussion

The percentage of resistant organisms, such as VRE, MRSA, and penicillin-nonsusceptible S pneumoniae, has been tracked by surveillance studies both in the United States and globally for more than a decade. Such continued surveillance is vital because the presence of an infection caused by MRSA and VRE has been shown to result in increased mortality, length of stay, and hospital costs when compared with infections caused by susceptible organisms.8, 9, 10, 11, 12, 13

This T.E.S.T. study adds to

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    Supported by Wyeth Pharmaceuticals and by Micron Research Ltd. with editorial support and assistance with data analysis.

    Statement of proprietary interest: Gerald A. Denys and Kim M. Koch have no proprietary interest. Michael J. Dowzicky is an employee of Wyeth Pharmaceuticals.

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