Diabetes and necrotizing soft tissue infections-A prospective observational cohort study: Statistical analysis plan

Association of sarcopenia with a higher risk of infection in patients with type 2 diabetes

AIMS

This study aimed to determine whether patients with type 2 diabetes and sarcopenia had a higher risk of infection.

STUDY DESIGNS

A cross-sectional study and a follow-up study were performed.

METHOD

A total of 2562 patients were enrolled and assessed for body composition and infection status. They were classified into four groups according to body fat (BF) and muscle mass index (ASMI): obese, sarcopenic, sarcopenic obese, and normal. Among these, 275 patients were followed for a median follow-up period of 1.84 years to evaluate the relationship of changes in skeletal muscle with infection status.

RESULTS

The sarcopenic and sarcopenic obese groups showed a higher risk of infection, an increase by 49.6% (OR = 1.496, 95% CI 1.102-2.031) and 42.4% (OR = 1.424, 95% CI 1.031-1.967) compared with the normal group, and also had a higher risk of respiratory infection, an increase by 56.0% (OR = 1.560, 95% CI 1.084-2.246) and 57.4% (OR = 1.574, 95% CI 1.080-2.293), respectively. Patients with the increased ASMI (OR = 0.079, 95% CI 0.021-0.298) represented a lower risk of infection than those with the decreased ASMI. Even a minor change (OR = 0.125, 95% CI 0.041-0.378) against age was beneficial to lowering the risk of infection. However, no association was found in the changes of body mass index and BF with infection status.

CONCLUSIONS

Sarcopenia, especially in patients with diabetes who are also obese, increases the risk of infection. Maintaining or improving muscle mass is expected to reduce infections.

Necrotizing Soft Tissue Infection Staphylococcus aureus but not S. pyogenes Isolates Display High Rates of Internalization and Cytotoxicity Toward Human Myoblasts

BACKGROUND

Necrotizing soft tissue infections (NSTIs) caused by group A Streptococcus (GAS) and occasionally by Staphylococcus aureus (SA) frequently involve the deep fascia and often lead to muscle necrosis.

METHODS

To assess the pathogenicity of GAS and S. aureus for muscles in comparison to keratinocytes, adhesion and invasion of NSTI-GAS and NSTI-SA isolates were assessed in these cells. Bloodstream infections (BSI-SA) and noninvasive coagulase-negative staphylococci (CNS) isolates were used as controls.

RESULTS

NSTI-SA and BSI-SA exhibited stronger internalization into human keratinocytes and myoblasts than NSTI-GAS or CNS. S. aureus internalization reached over 30% in human myoblasts due to a higher percentage of infected myoblasts (>11%) as compared to keratinocytes (<3%). Higher cytotoxicity for myoblasts of NSTI-SA as compared to BSI-SA was attributed to higher levels of psmα and RNAIII transcripts in NSTI-SA. However, the 2 groups were not discriminated at the genomic level. The cellular basis of high internalization rate in myoblasts was attributed to higher expression of α5β1 integrin in myoblasts. Major contribution of FnbpAB-integrin α5β1 pathway to internalization was confirmed by isogenic mutants.

CONCLUSIONS

Our findings suggest a factor in NSTI-SA severity is the strong invasiveness of S. aureus in muscle cells, a property not shared by NSTI-GAS isolates.