The relationship between antibiotic resistance phenotypes and biofilm formation capacity in clinical isolates of Acinetobacter baumannii

Abstract

Background: Understanding of the biological factors responsible for prevalence and persistence of Acinetobacter baumannii in hospital settings is critical to prevent and control the corresponding nosocomial infections. Objectives: This study was conducted to investigate whether the biofilm-forming ability is associated with the emergence of different antibiotic resistance phenotypes [multidrug resistance (MDR)/extensively drug resistance (XDR) and non-MDR] of A. baumannii. Methods: The capacities of biofilm formation in 80 clinical A. baumannii strains isolated from hospitalized burn patients in Bushehr, Iran, were assessed using the crystal violet staining. Results: The statistical analysis of the relationship between biofilm-forming ability and antibiotic resistance phenotypes among all clinical A. baumannii strains using one-way ANOVA test indicated that biofilm formation capacity of non-MDR A. baumannii isolates was significantly higher than that of MDR and XDR ones (P < 0.001), suggesting an inverse relationship between biofilm formation capacity and the acquisition of MDR/XDR phenotypes. Major international clonal types (ICI and ICII) also exhibited such a significant relationship (P < 0.0001). However, the investigation of A. baumannii IC variants showed no significant relationship between these phenotypes. Conclusions: Given that non-MDR A. baumannii isolates in major IC types were observed to form a strong biofilm compared to MDR/XDR ones, it seems that biofilm may play a key role in the persistence and survival of A. baumannii isolates with an inadequate level of antibiotic resistance. Furthermore, the results showed that the relationship between biofilm and antibiotic resistance phenotypes might be affected by the IC types (major IC types or IC variants).