Nr. 19(3)/2011

Adriana Hristea, Ioana D. Olaru, Olga Dorobat, Maria Nica, Mihaela Ion, Ruxandra Moroti, Victoria Arama, Alexandru Rafila, Emanoil Ceausu, Lee W. Riley

Objectives: (1) To describe the resistance patterns of Gram negative bacilli (GNB) isolated from blood cultures and (2) identify the epidemiological characteristics associated with multi-drug resistance (MDR). Materials and methods: We performed a retrospective study of the susceptibility profile of GNB strains isolated from blood stream infections (BSI) from patients admitted to two tertiary infectious diseases facilities between January 2009 and January 2011. Bacteria were isolated in BacT/ALERT and identified by classic techniques or automated methods. Susceptibility testing was done by disk-diffusion and automated methods according to CLSI guidelines. Clavulanic acid synergy test was performed to identify extended spectrum beta-lactamase (ESBL) production. Multidrug-resistance (MDR) was defined as resistance to 3 or more classes of antimicrobial agents. Results: From 116 patients, 222 non-duplicate isolates were identified. The isolates included: 120 E. coli (54%), 38 Klebsiella spp. (17%), 16 P. aeruginosa (7%), 11 Acinetobacter spp. (5%), 30 other Enterobacteriaceae (14%) and, 7 other non-fermenters (3%). The prevalence of resistance to one, two, and three classes of drugs were 17.6%, 18.3% and 31.7%, respectively. ESBL production was detected in 12 (10%) of E. coli and 10 (26%) of Klebsiella spp. Carbapenem resistance was identified in 8 (73%) of Acinetobacter spp. and 10 (63%) of P. aeruginosa isolates as compared with 4 (2.1%) in Enterobacteriaceae isolates. Clinical and epidemiological data were available for 142 (64%) patients. The primary source of bacteraemia were suspected to include: urinary tract (43%), gastrointestinal (13%), pulmonary (11%), others (6%), and unknown sites (27%). BSI were hospital associated (HA), health care associated (HCA) and community acquired (CA) in 50.7%, 17.6% and 31.7%, respectively. There was no statistical difference regarding the origin, underlying conditions and epidemiology of the three different epidemiological types of BSI. MDR was more frequently seen in HA (37.5%) and HCA infections (44%) than in CA (15.6%). Prior hospitalization, recent urinary tract infection, antimicrobials use, recent surgery and death were each associated with MDR BSI. In multivariate analysis, only prior use of antimicrobials was associated with MDR BSI (p=0.001). Conclusions: High MDR prevalence (31.7%) was observed in patients with BSI in our study. Combined resistance to third-generation cephalosporins, aminoglycosides, and quinolone was considerably higher than that reported from other European countries, especially in patients with hospital associated infections. Antimicrobial use within the past 3 months was associated with MDR BSI in our patient population.

Keywords: Bloodstream infections,Gram negative bacilli,multi-drug resistance