Characterization of Pseudomonas aeruginosa and Acinetobacter calcoaceticus-baumannii complex traumatic wound isolates

Healing of traumatic wounds is complicated by infecting pathogens, with Pseudomonas aeruginosa and members of the Acinetobacter calcoaceticus-baumannii complex among the most common infectious agents. However, a full understanding of genotypic and phenotypic differences between circulating wound isolates is lacking. To address this, traumatic wounds were sampled at Emory University Hospital, and 24 isolates were characterized; we focused on P. aeruginosa and Acinetobacter due to their prevalence and tendency for antibiotic resistance. Even though these species are renowned for antibiotic resistance, only two of the tested isolates could be classified as multidrug resistant. Whole-genome sequencing and analysis revealed that isolates from different patients were genetically distinct; however, longitudinal isolates from the same patient were closely related and appeared to represent chronic colonization by the same strain. Phylogenetic analysis revealed that laboratory strains (PAO1 and AB5075) that were isolated decades previously and from different locations grouped closely to subsets of the recent wound isolates. Given the importance of biofilm formation in infection, the ability of the isolates to form biofilms was assessed; all isolates formed biofilms but showed temporal and magnitude differences. Analysis of a subset of isolates revealed that planktonic P. aeruginosa was resistant to human serum-mediated killing. While the same was true for the majority of Acinetobacter isolates, one showed planktonic sensitivity that was abrogated when grown in a biofilm. Taken together, these data reveal genotypic and phenotypic differences in circulating isolates of P. aeruginosa and A. baumannii. IMPORTANCE The presence or absence of bacterial virulence factors and antibiotic resistance genes can greatly alter disease progression in a traumatic wound as well as the best course of treatment. Therefore, there is a need for a greater understanding of the genotypic and phenotypic differences between circulating wound isolates. Characterization of clinical isolates of P. aeruginosa and the A. calcoaceticus-baumannii complex obtained from traumatic wounds at Emory University Hospital revealed genotypic and phenotypic differences that resulted in variation in antibiotic resistance, biofilm formation, and the presence of potential virulence factors. A greater understanding of wound isolates may provide avenues for better therapies for the treatment of future infections. Taken together, these data reveal genotypic and phenotypic differences in circulating isolates of P. aeruginosa and A. baumannii. These studies were supported by Military Infectious Diseases Research Program awards #W0267_18_WR and MIC-73-10881.