Nosocomial outbreak of Pseudomonas aeruginosa in adult inpatients: multidrug vs. nonmultidrug-resistant strains

Abstract number: R2400

Navarro J.L., Somodevilla A., Martínez M.C., Azcona J.M., Agudo S., Alarcón T., López-Brea M.

Objective:Pseudomonas aeruginosa (PA) is an emerging opportunistic pathogen that can easily exhibit multidrug-resistance (MDR). It is intrinsically resistant to many antibiotic classes and can readily acquire new mechanisms. Higher rates of death, prolonged hospitalization and rising costs have been associated with MDR-PA. Comparison of MDR rates among institutions is not always possible because there is no agreement to define MDR in PA. We use here a modified MDR criterion from Paterson et al. to make it more operational. The aim of this study was to compare epidemiological features between MDR and non-MDR-PA infection rates within an outbreak at a University Hospital in Madrid.

Methods: An observational retrospective study of 822 PA isolates from 369 adult inpatients was conducted for one year. All kind of samples were obtained. Colonization and infection were not distinguished. We studied 10 drugs: ceftazidime (CAZ), cefepime (CPE), piperacillin-tazobactam (TZP), imipenem (IMI), meropenem (MER), ciprofloxacin (CIP), gentamycin (GEN), tobramycin (TOB), amikacin (AKA) and colistin (COL). Susceptibility was tested by a broth microdilution method, using CLSI breakpoints to interpret. MDR was defined as a decreased susceptibility to two or more of the six following items: (1) CPE and/or CAZ; (2) IMI and/or MER; (3) TZP; (4) CIP; (5) AKA and/or [GEN and TOB]; (6) COL. Qualitative variables are expressed as proportions, compared using Chi-square test and quantified by odds-ratio (OR) with 95% confidence. P-values lower than 0.05 were considered significant.

Results: Globally, 296 (36.0%) isolates were considered MDR according to the MDR criterion. Among first isolates, 95 (25.7%) were MDR. No significant difference in gender was found between MDR and non-MDR-PA (p = 0.17). An increased rate of MDR-PA was shown in patients under 70 years (mainly in the 5th decade, p = 0.03). PA isolates were specially high at ICU, Neumology, Internal Medicine, Haematology and Nephrology departments, but only Haematology dpt. (OR = 5.55 [2.43–12.81], p < 0.0001) showed a statistically significant difference of MDR over the rest.

Conclusions: (1) A very high rate of MDR-PA isolates was found within the outbreak. (2) Although PA isolation rate is higher in males, no difference has been found between MDR and non-MDR. (3) Among patients infected by PA, young ones have a higher likelihood of being infected by a MDR-PA than older. (4) Haematology dpt. had the highest rate of MDR strains.

Session Details

Date: 07/05/2011
Time: 00:00-00:00
Session name: Abstracts of 21st ECCMID / 27th ICC
Location: Milan, Italy, 7 - 10 May 2011
Presentation type:
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