Antimicrobial susceptibility to azithromycin among Salmonella enterica isolates from the United States.

Abstract

Due to emerging resistance to traditional antimicrobial agents, such as ampicillin, trimethoprim-sulfamethoxazole, and chloramphenicol, azithromycin is increasingly used for the treatment of invasive Salmonella infections. In the present study, 696 isolates of non-Typhi Salmonella collected from humans, food animals, and retail meats in the United States were investigated for antimicrobial susceptibility to azithromycin. Seventy-two Salmonella enterica serotype Typhi isolates from humans were also tested. For each isolate, MICs of azithromycin and 15 other antimicrobial agents were determined by broth microdilution. Among the non-Typhi Salmonella isolates, azithromycin MICs among human isolates ranged from 1 to 32 μg/ml, whereas the MICs among the animal and retail meat isolates ranged from 2 to 16 μg/ml and 4 to 16 μg/ml, respectively. Among Salmonella serotype Typhi isolates, the azithromycin MICs ranged from 4 to 16 μg/ml. The highest MIC observed in the present study was 32 μg/ml, and it was detected in three human isolates belonging to serotypes Kentucky, Montevideo, and Paratyphi A. Based on our findings, we propose an epidemiological cutoff value (ECOFF) for wild-type Salmonella of ≤16 μg/ml of azithromycin. The susceptibility data provided could be used in combination with clinical outcome data to determine tentative clinical breakpoints for azithromycin and Salmonella enterica.

• Authors: Maria Sjölund-Karlsson, Kevin Joyce, Karen Blickenstaff, Takiyah Ball, Jovita Haro, Felicita M Medalla, Paula Fedorka-Cray, Shaohua Zhao, John A Crump, Jean M Whichard
• Journal: Antimicrobial agents and chemotherapy (Antimicrob Agents Chemother) Vol. 55 Issue 9 Pg. 3985-9 (Sep 2011) ISSN: 1098-6596 [Electronic] United States
• PMID: 21690279 (Publication Type: Journal Article, Research Support, U.S. Gov't, Non-P.H.S., Research Support, U.S. Gov't, P.H.S.)

Chemical References

• Anti-Bacterial Agents
• Azithromycin

Topics

• Animals
• Anti-Bacterial Agents (pharmacology)
• Azithromycin (pharmacology)
• Humans
• Microbial Sensitivity Tests
• Salmonella enterica (drug effects)
• United States