A Longitudinal Evaluation of the Bacterial Pathogens Colonizing Chronic Non-Healing Wound Sites at a United States Military Treatment Facility in the Pacific Region

Abstract

Purpose

The biology of chronic wounds is complex and many factors act concurrently to impede healing progress. In this study, the dynamics of microflora changes and their antibiotic susceptibility patterns were evaluated longitudinally over 30 days using data from 28 patients with a total of 47 chronic lower extremity wounds.

Materials and Methods

In this study, colonized wound isolates were characterized using cultural, biochemical, and VITEK 2 methods. Antibiotic susceptibility patterns of the wound isolates were analyzed using various phenotypic assays. Furthermore, antimicrobial resistance patterns and the presence of mutations were evaluated by a genotypic assay, whole-genome sequencing (WGS).

Results

Staphylococcus aureus and Pseudomonas aeruginosa were found to be the most common strains at early time points, while members of Enterobacteriaceae were prevalent at later stages of infection. Antimicrobial resistance testing and whole-genome sequencing revealed that the molecular and phenotypic characteristics of the identified wound pathogens remained relatively stable throughout the study period. It was also noted that Enterobacter and Klebsiella species may serve as reservoirs for quinolone resistance in the Pacific region.

Conclusion

Our observations showed that wounds were colonized with diverse bacteria and interestingly their numbers and/or types were changed over the course of infection. The rapid genetic changes that accompanied the first 4 weeks after presentation did not directly contribute to the development of antibiotic resistance. In addition, standard wound care procedures did not appear to select for resistant bacterial strains. Future efforts should focus on defining those genetic changes associated with the wound colonizing microorganisms that occur beyond 4 weeks.

Keywords:

• anti-microbial resistance
• antimicrobial susceptibility profiling
• non-healing wound
• wound microflora
• wound healing

Acknowledgments

This work was supported by the US Department of Defense (DoD) Global Emerging Infections Surveillance (GEIS) program. We acknowledge the staff at the Walter Reed Army Institute of Research-Multidrug-Resistant Organism Repository and Surveillance Network (WRAIR/MRSN) for whole-genome sequencing and bioinformatics analyses, visualization, interpretation, and reporting. Opinions, interpretations, conclusions and recommendations are those of the author and are not necessarily endorsed by the US Army. This research protocol was approved by the Tripler Army Medical Center Scientific Review Committee. The views expressed in this manuscript are those of the author(s) and do not reflect the official policy or position of the US Military Academy, the Department of the Army, the Department of Defense, or the US Government.

Disclosure

The authors affirm that they have no competing interests in this work.