Secular trends in Acinetobacter baumannii resistance in respiratory and blood stream specimens in the United States, 2003 to 2012: A survey study.
BACKGROUND
Acinetobacter baumannii (AB) has evolved a variety of resistance mechanisms and exhibits unpredictable susceptibility patterns, making it difficult to select empiric therapy.


OBJECTIVE
To examine US secular trends in the resistance of AB in respiratory infections and blood stream infections (BSI) to antimicrobial agents whose effectiveness is supported in the literature


METHODS
Survey.


METHODS
We analyzed 3 time periods (2003-2005, 2006-2008, 2009-2012) in Eurofins' The Surveillance Network for resistance of AB to the following antimicrobials: carbapenems (imipenem, meropenem, doripenem), aminoglycosides (tobramycin, amikacin), tetracyclines (minocycline, doxycycline), polymyxins (colistin, polymyxin B), ampicillin-sulbactam, and trimethoprim-sulfamethoxazole. Resistance to ≥3 drug classes defined multidrug resistance (MDR).


RESULTS
We identified 39,320 AB specimens (81.1% respiratory, 18.9% BSI). The highest prevalence of resistance was to doripenem (90.3%) followed by trimethoprim-sulfamethoxazole (55.3%), and the lowest to colistin (5.3%). Resistance to carbapenems (21.0% in 2003-2005 and 47.9% in 2009-2012) and colistin (2.8% in 2006-2008 to 6.9% in 2009-2012) more than doubled. Prevalence of MDR AB rose from 21.4% in 2003 to 2005 to 33.7% in 2006 to 2008, and remained stable at 35.2% in 2009 to 2012. In contrast, resistance to minocycline diminished from 56.5% (2003-2005) to 30.5% (2009-2012). MDR organisms were most frequent in nursing homes (46.5%), followed by general ward (29.2%), intensive care unit (28.7%), and outpatient setting (26.2%).


CONCLUSIONS
Resistance rates among AB to such last-resort antimicrobials as carbapenems and colistin are on the rise, whereas that to minocycline has declined. Nursing homes are a reservoir of resistant AB. These trends should inform not only empiric treatment of serious infections, but also approaches to infection control.
EviMed Research Group, LLC, Goshen, Massachusetts.|School of Public Health and Health Sciences, University of Massachusetts, Amherst, Massachusetts.
Marya D
MD
Zilberberg
Barnes-Jewish Hospital, St. Louis, Missouri.
Marin H
MH
Kollef
Washington Hospital Center, Washington, DC.
Andrew F
AF
Shorr
D000151:Acinetobacter Infections / Q000188:drug therapy* / Q000382:microbiology; D040981:Acinetobacter baumannii / Q000187:drug effects* / Q000302:isolation & purification; D000667:Ampicillin / Q000627:therapeutic use; D000900:Anti-Bacterial Agents / Q000494:pharmacology / Q000627:therapeutic use*; D016470:Bacteremia / Q000188:drug therapy*; D015780:Carbapenems / Q000627:therapeutic use; D003428:Cross Infection; D024881:Drug Resistance, Bacterial; D006801:Humans; D007362:Intensive Care Units; D008826:Microbial Sensitivity Tests / Q000379:methods; D012141:Respiratory Tract Infections / Q000188:drug therapy*; D013407:Sulbactam / Q000627:therapeutic use; D011795:Surveys and Questionnaires; D015662:Trimethoprim, Sulfamethoxazole Drug Combination / Q000627:therapeutic use; D014481:United States
D000900:Anti-Bacterial Agents; D015780:Carbapenems; C035444:sultamicillin; D000667:Ampicillin; D015662:Trimethoprim, Sulfamethoxazole Drug Combination; D013407:Sulbactam