The categorization of prior antibiotic use: impact on the identification of risk factors for drug resistance in case control studies.
BACKGROUND
Analytic approaches to the identification of risk factors for the development of drug resistance vary and may affect study results. Using fluroquinolone-resistant Pseudomonas aeruginosa (FQRPA) and imipenem-resistant P. aeruginosa as models (IRPA), we aimed to examine the effect of different approaches to classification of prior antibiotic use (i.e., class versus spectrum) on the identification of risk factors for antibiotic resistance.


METHODS
Case-control studies to identify risk factors for FQRPA and IRPA were performed. In each, two analytic models were utilized. In the first, prior antibiotic use was classified by class, and in the other, prior antibiotic use was classified by spectrum of activity. Risk factors identified by the two models were compared qualitatively for each resistant organism.


RESULTS
879 isolates of P. aeruginosa were included in the case-control studies. Risk factors for FQRPA and IRPA identified in multivariable analyses differed based on which method of classification of prior antibiotic use was utilized.


CONCLUSIONS
The identification risk factors for the development of drug-resistant organisms could depend on the method of classification of prior antibiotic use. In studies of risk factors for resistant infections, the approach to classification of prior antibiotic use should be clearly stated and justified.
Division of Infectious Diseases of the Department of Medicine, University of Pennsylvania School of Medicine, Philadelphia, PA, USA. leanne.gasink@uphs.upenn.edu
Leanne B
LB
Gasink
Theoklis E
TE
Zaoutis
Warren B
WB
Bilker
Ebbing
E
Lautenbach
D000900:Anti-Bacterial Agents / Q000145:classification* / Q000627:therapeutic use; D016022:Case-Control Studies; D015331:Cohort Studies; D024901:Drug Resistance, Multiple, Bacterial / Q000187:drug effects*; D004363:Drug Utilization; D024841:Fluoroquinolones / Q000145:classification / Q000627:therapeutic use; D006785:Hospitals, University; D006801:Humans; D015378:Imipenem / Q000145:classification / Q000627:therapeutic use; D016017:Odds Ratio; D011552:Pseudomonas Infections / Q000188:drug therapy; D011550:Pseudomonas aeruginosa / Q000187:drug effects*; D012189:Retrospective Studies; D012307:Risk Factors
D000900:Anti-Bacterial Agents; D024841:Fluoroquinolones; D015378:Imipenem