Relationship between prior antibiotic exposure and multidrug-resistant Pseudomonas aeruginosa

Abstract number: p1365

Lodise  T.P., Patel  N., Graves  J., Lomaestro  B.M.


The increasing emergence of multi-drug resistant Pseudomonas aeruginosa (MDR-PA) infections (infx) is a major public health concern. Despite the rising rates, MDR-PA risk factors have not been well defined & quantitative evaluations of the relationship between prior antibiotic (abx) exposure & MDR-PA have not been performed in patients (pt).


To examine the risk factors for MDR-PA & to quantify the relationship between prior abx exposure & MDR-PA.


Study period: 1/02–4/04. Inclusion criteria: (1) >= 18 yrs, (2) PA respiratory culture (met CDC infx criteria), (3) non-cystic fibrosis. Demographics, co-morbid conditions, abx (30 days (d) prior PA) were recorded. Recursive partitioning (CART) was used to identify the duration of abx exposure for each antipseudomonal class that was associated with an increased probability of MDR-PA. MDR was defined as resistance to >= 4 anti-pseudomonal abx classes. Logistic regression was performed to identify the predictor variables that were independently associated with MDR-PA. Variables that were associated with MDR-PA in the univariate analysis were included in the logistic regression analysis at model entry and a stepwise process was used to identify independent predictors.


During study, 353 pts met criteria. Mean age: 60.6 ± 18.9. Median LOS prior PA: 24 d [0–178]. Mechanical ventilation at PA onset: 80.2%. MDR-PA: 34.6%. 30-day mortality: 8.8%

Note for Table: Data are number (%) of pts with MDR-PA or non-MDR-PA.

In logistic regression, prior carbapenem exposure >=3 d (OR = 1.9, 95% CI: 1.1–3.4), prior piperacillin/tazobactam exposure >=12 d (OR = 1.8, 95% CI: 1.1–3.1) & LOS prior PA >= 33 d (OR = 3.5, 95% CI; 2.2–5.8) were the only univariate predictor variables independently associated with MDR-PA.


Prior carbapenem exposure >=3 d, prior piperacillin/tazobactam >=12 d, & prolonged prior LOS were the strongest predictors of MDR-PA. Further epidemiologic and molecular studies are needed to ascertain the reasons for higher rates of MDR-PA associated with certain prior abx.

Session Details

Date: 01/08/2007
Time: 00:00-00:00
Session name: XXIst ISTH Congress
Location: Oxford, UK
Presentation type:
Back to top