SLR - September 2020 - Nick R. Thompson

Multidrug Resistant Organism Predicts Ulcer Recurrence Following Surgical Management of Diabetic Foot Osteomyelitis

Reference: Schmidt BM, Ye W, Zhou S. Multidrug Resistant Organism Predicts Ulcer Recurrence Following Surgical Management of Diabetic Foot Osteomyelitis. Int Wound J. 2020;1–8.

Scientific Literature Review

Reviewed By: Nick R. Thompson, DPM 
Residency Program: East Liverpool City Hospital – East Liverpool, OH

Podiatric Relevance: The necessity of obtaining proximal (clean) margin cultures intraoperatively is emphasized, as the majority of cultures obtained within this study were positive for microbiologic growth. Podiatric surgeons can appreciate the worse outcomes (recurrent ulceration, amputation, or death) found in patients with positive cultures obtained from the proximal (clean) bone margins following surgical debridement, most specifically in patients found to harbor multidrug resistant organisms (MRDO). 

Methods: This paper analyzed the outcomes amongst 223 diabetic patients undergoing surgical intervention for osteomyelitis  in relation with the bacterial species isolated from their proximal (clean) bone cultures at time of surgery. The proximal margin was sent for microbiologic evaluation of aerobic, anaerobic, fungal, and acid-fast bacilli. Surgical patients were followed for one year after initial surgery and checked at 3 month intervals for the recurrent ulceration, amputation, or death. The various culture results were then compared with outcomes of these surgical patients over one year to determine if individual bacterial species contributed to worsened outcomes. Multi-variate comparison of the study group was then made with a control group of diabetics with no history of diabetic foot ulceration or amputation. The study also looked to compare patient laboratory values with their outcomes. 

Results: The majority of patients within this study (79.2 percent) exhibited microbiologic growth of the proximal osseous margin, polymicrobial growth was found in abundance (39 percent), and MRDO’s were also routinely identified (13.9 percent). MRDO’s were found to be significantly associated with the development of recurrent ulceration, amputation or death in surgical patients after one year. Notably, amputation or death was significantly associated with the presence of P. aeruginosa (P < .01), E. coli (P < .01), E. faecium (P < .05), and E. faecalis (P<0.5). Comparison of the two groups (surgical vs control diabetics) found presence of painful peripheral neuropathy along with younger age (57.3 ± 10.1 vs 65.7 ± 14.8) to be significant predictors for contracting osteomyelitis. The rate of recurrent diabetic foot ulceration at one year following amputation in this study (44.5 percent) was consistent with a previously determined rate of 40 percent by Armstrong et. al in 2017. A weak statistical relationship was found between ESR, lymphocyte count, and immature granulocyte count with patient outcomes. No statistically significant predictors of outcome were found with evaluation of albumin, creatinine, CRP, HgA1c, and WBC.

Conclusions: The sheer percentage of microbiological growth within the perceived clean proximal osseous margins in this study shows how residual bacterial burden is often retained following debridement, and the necessity for collecting proximal cultures following surgical debridement of diabetic wounds with osteomyelitis. The direct correlation of worsened outcomes with MRDO’s also suggests more aggressive surgical debridement and screening for resistant infections in patients with history of MRDO’s, instead of reliance on more advanced ‘heavy-hitter’ antibiotics during the post-operative period. I will also follow patient wound cultures for isolated bacterial species in wounds without yet perceived osteomyelitis, as this could help predict the course if the patient were to continue breaking down and eventually contract osteomyelitis adjacent to a colonized wound. 

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