Multidrug-ResistantAcinetobacter baumanniiHarboring OXA-24 Carbapenemase, Spain

In February 2006, a patient colonized with a multidrugresistant sequence type 56 Acinetobacter baumannii strain was admitted to a hospital in Madrid, Spain.This strain spread rapidly and caused a large outbreak in the hospital.Clinicians should be alert for this strain because its spread would have serious health consequences. T he increasing resistance of Acinetobacter baumanniito antimicrobial drugs, including carbapenems (1-3), and resistance to desiccation and disinfectants (4) contribute to its persistence in hospital environments and propensity to cause outbreaks (5,6).In February 2006, a patient colonized with a multidrug-resistant A. baumannii strain was admitted to the medical-surgical intensive care unit (ICU) of a hospital in Madrid, Spain.This strain then spread rapidly, persisted for >30 months, and caused a large outbreak in the hospital.We report details of this outbreak. The StudyWe conducted a retrospective longitudinal study at 12 de Octubre University Hospital, Madrid, Spain, of patients colonized/infected with A. baumannii during January 2006-May 2008.We also conducted a cohort study of patients with A. baumannii bacteremia during January 2002-May 2008.MICs of drugs were confi rmed by using Etest strips (AB Biodisk, Solna, Sweden) according to the manufacturer's criteria.Multidrug-resistant (MDR) phenotypes were defi ned as resistance to 5 classes of drugs: antipseudomonal cephalosporins (ceftazidime, cefepime), carbapenems (imipenem, meropenem), piperacillin/tazobactam, fl uoro-quinolones, and aminoglycosides (gentamicin, tobramycin, amikacin).Isolates were classifi ed on the basis of antimicrobial susceptibility patterns: antibiotype 1, MDR isolates; antibiotype 2, isolates resistant to carbapenems but not MDR; and antibiotype 3, isolates susceptible to carbapenems.Colonization was defi ned as isolation of A. baumannii from >1 clinical specimen in the absence of clinical symptoms consistent with infection.Bacteremia was determined by application of criteria proposed by the Centers for Disease Control and Prevention (Atlanta, GA, USA) (7).Clonal relatedness between clinical isolates was determined by using pulsed-fi eld gel electrophoresis (PFGE) and the CHEF DRIII system (Bio-Rad Laboratories, Hercules, CA, USA) according to reported techniques (8).Migration of DNA fragments was normalized, and computer-assisted analysis of PFGE patterns was conducted by using Bionumerics software (Applied Maths, Sint-Martens-Latem, Belgium).Multilocus sequence typing (MLST) was performed according to published protocols (9).Isolates were assigned to a sequence type according to the allelic profi les database (http://pubmlst.org/abaumannii/).Univariate analysis was performed by using the t test for continuous variables and the χ 2 or Fisher exact tests for categorical variables.Adjusted odds ratios (ORs) were calculated by using logistic regression analysis.Data were analyzed by using SPSS software (SPSS Inc., Chicago, IL, USA).A p value <0.05 was considered signifi cant.During January 2006-May 2008, a total of 377 patients were colonized/infected with A. baumannii.Mean age of the patients was 57 years and 63.4% were men.Patients were hospitalized mostly in ICUs (184, 48.8%), and in surgical (100, 26.5%), medical (85, 22.5%), and pediatric (8, 2.1%) wards.A total of 76.9% (290/377) of the isolates were antibiotype 1, 9.0% (34/377) were antibiotype 2, and 14.1% (53/377) were antibiotype 3. Temporal distribution of cases is shown in Figure 1, panel A. Bacterial isolates of antibiotype 1 were assigned to the major clonal type (clone AbH12O-A2) by PFGE.Of 290 patients with A. baumannii antibiotype 1 isolates (clone AbH12O-A2), 165 patients were infected (57%) and 125 (43%) were colonized.MLST analysis of 3 isolates belonging to clone AbH12O-A2 was performed to determine the relationship between these isolates and other described strains.The 3 isolates showed the same allelic profi le of 7 housekeeping genes (allele no. in brackets; gltA [1], gyrB [18], gdhB [18], recA [10], cpn60 [14], gpi [29], and rpoD [18]) and were identifi ed as sequence type 56 according to the MLST database (http://pubmlst.org/abaumannii/).A. baumannii clone AbH12O-A2, which showed a broad antimicrobial drug-resistance profi le, resistance to carbapenems, and susceptibility only to tigecycline and colistin, was present throughout the entire 30-month study