Pathogens Causing Diabetic Foot Infection and the Reliability of the Superficial Culture

Prevalence of S. aureus and/or MRSA in hospitalized patients with diabetic foot and establishment of LAMP methods for rapid detection of the SCCmec gene

BACKGROUND

Patients with diabetic feet are prone to be infected due to the impaired immune system. However, the prognostic outcome of different microbial infections remains controversial. Identification and rapid screening of the pathogenic microorganisms that pose the greatest threat to the prognosis of patients with diabetic foot infections (DFIs) is critical.

METHODS

Clinical data were statistically analyzed, which were obtained from 522 patients with DFIs, including pathogenic bacterial culture results and treatment outcomes at the last return visit. In addition, a loop-mediated isothermal amplification (LAMP) detection method was developed to identify the prevalent subtype of methicillin-resistant Staphylococcus aureus (MRSA) in DFIs patients. This study was approved by the Ethics Committee of Nanfang Hospital (NFEC-202012-K6) and registered on ClinicalTrials.gov (NCT04916457) on June 1, 2021.

RESULTS

We found that the proportion of patients with infections of Staphylococcus aureus (S. aureus) and MRSA was 27.7% (145/522) and 33.7% (49/145), respectively. Additionally, the incidence of osteomyelitis was 46.9% (23/49) and amputation/disability was 40.8% (20/49) in patients with MRSA infection, which were significantly higher compared to patients with other types of bacterial infections such as methicillin-susceptible Staphylococcus aureus (MSSA). Notably, we demonstrated that the main prevalent subtype of MRSA in DFIs patients in our hospital was Staphylococcal chromosomal cassettes mec (SCCmec) type II. In addition, it only takes 1.5 h to complete the entire experimental procedure in this LAMP assay, providing high sensitivity (100%) and specificity (77.8%) in hospitalized patients with DFIs.

CONCLUSIONS

We demonstrated there is a very high rate of MRSA isolation in patients with DFIs and revealed that patients infected with MRSA are at a higher risk of developing osteomyelitis, and amputation or disability. Importantly, we have developed a method for quickly screening newly admitted patients for MRSA.

Major Amputation Profoundly Increases Mortality in Patients With Diabetic Foot Infection

Introduction: An acute diabetic foot infection (DFI) is a serious condition and a leading cause of hospitalization and major amputation in patients with diabetes. Aim of this study was to evaluate the long term survival and risk factors for death and amputation after the DFI requiring hospital treatment.

Materials and Methods: A retrospective study included all adult patients hospitalized for DFI treatments during 2010–2014. Overall survival (OS) and amputation free survival (AFS) (without major amputation) was calculated. We performed a Cox regression analysis of several clinical parameters to evaluate the effects of clinical parameters on overall and amputation-free survival.

Results: Total of 324 patients with mean age of 66.8 (SD 12.8) years were included. The one- and five-year OS after DFI 81.2% (95%CI 77.5–84.9%) and 49.7% (95%CI 44.8–54.6%), respectively. Major amputation, wound ischemia, older age, and a low glomerular filtration rate reduced the OS after DFI. After a major amputation, the one- and five-year OS was 41.7% (95%CI 13.9–69.5) and 8.3% (95%CI 0.0–24.0%), respectively. Wound ischemia, older age, and elevated C-reactive protein reduced AFS. In contrast, hypertensive medication use was identified as a protective factor.

Conclusion: Mortality after a DFI remains high and is significantly increased after a major amputation. Findings highlight the importance of early wound and ischemia management for DFI prevention.