Temporal trends and patterns in antimicrobial resistant Gram-negative bacteria implicated in intensive care unit-acquired infections: a cohort-based surveillance study in Istanbul, Turkey

Objectives: This study assessed trends and patterns in antimicrobial resistant intensive care unit (ICU)-acquired infections caused by Gram-negative bacteria (GNB) in Istanbul, Turkey.

Methods: Bacterial culture and antibiotic susceptibility data were collected for all GNB causing nosocomial infections in five adult ICUs of a large university hospital during 2012-2015. Multi-resistance patterns were categorised as multidrug (MDR), extensively-drug (XDR) and pandrug (PDR)-resistance. Patterns and trends were assessed using seasonal decomposition and regression analyses.

Results: Of 991 pathogenic GNB recorded, most frequent were Acinetobacter baumannii (35%), Klebsiella species (27%), Pseudomonas aeruginosa (18%), Escherichia coli (7%) and Enterobacter species (4%). The overall infection rate decreased by 41% from 18.4 to 10.9 cases per 1000 patient-days in 2012 compared to 2015 (p<0.001), mostly representing decreases in bloodstream infections and pneumonias by A. baumannii and P. aeruginosa. XDR proportion in A.baumannii increased from 52% in 2012 to 72% in 2015, but only one isolate was colistin-resistant. Multi-resistance patterns remained stable in Klebsiella, with overall XDR and possible PDR proportions of 14% and 2%, respectively. A back-to-susceptibility trend was noted for P. aeruginosa in which the non-MDR proportion increased from 53% in 2012 to 71% in 2015. 88% of E.coli and 40% of Enterobacter isolates were MDR, but none was XDR.

Conclusions: Antimicrobial resistance patterns in pathogenic GNB continuously change over time and may not reflect single-agent resistance trends. The proportionate amount of antimicrobial-resistant GNB may persist despite overall decreasing infection rates. Timely regional surveillance data are thus imperative for optimal infection control.