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Injection site microflora in persons with diabetes: why needle reuse is not associated with increased infections?
Sofia Wareham-Mathiassen1,2, Lene Bay1, Vera Pinto Glenting3
1Department of Immunology and Microbiology, Copenhagen University, Copenhagen, Denmark.
Abstract:
Needle reuse is a common practice and primary cause of customer compliance issues such as pain, bruising, clogging, injection site reactions (ISR), and associated lipodystrophy. This study aimed to characterize skin microflora at injection sites and establish microbial contamination of used pen injectors and needles. The second objective was to evaluate the risk of infections during typical and repeated subcutaneous injections. 50 participants with diabetes and 50 controls (n = 100) were sampled through tape strips and skin swabs on the abdomen and thigh for skin microflora. Used pen injectors and needles were collected after in-home use and from the hospital after drug administration by health care professionals (HCPs). Samples were analyzed by conventional culture, matrix-assisted laser desorption/ionization-time of flight (MALDI-TOF), mass spectrometry (MS), confocal laser scanning microscopy (CLSM), and 16S/ITS high throughput sequencing (HTS). A mathematical model simulated the risk of needle contamination during injections. Injection site populations were in 102 cells/cm2 order, with increased viable bacteria and anaerobic bacteria on the skin in persons with diabetes (p = 0.05). Interpersonal variation dominated other factors such as sex or location. A higher prevalence of Staphylococcus aureus on abdominal skin was found in persons with diabetes than control skin (p ≤ 0.05). Most needles and cartridges (95% and 86%) contained no biological signal. The location of the device collection (hospital vs home-use) and use regimen did not affect contamination. CLSM revealed scarcely populated skin microflora scattered in aggregates, diplo, or single cells. Our mathematical model demonstrated that penetrating bacteria colonies during subcutaneous injection is unlikely. These findings clarify the lack of documented skin infections from subcutaneous insulin injections in research. Furthermore, these results can motivate the innovation and development of durable, reusable injection systems with pharmacoeconomic value and a simplified and enhanced user experience for patients.
Insights
Needle reuse in diabetes care is common, but this study found minimal microbial contamination on used needles and low infection risk. Findings support developing durable, reusable injection systems for better patient experience and cost savings.
Area of Science:
- Microbiology
- Dermatology
- Medical Devices
Background:
- Needle reuse is prevalent, leading to injection site reactions (ISR) like pain, bruising, and lipodystrophy.
- Understanding skin microflora and needle contamination is crucial for assessing infection risks associated with repeated subcutaneous injections.
Purpose of the Study:
- To characterize skin microflora at injection sites.
- To determine microbial contamination levels on used pen injectors and needles.
- To evaluate the risk of infections from subcutaneous injections.
Main Methods:
- Collected skin microflora samples using tape strips and swabs from participants with and without diabetes.
- Analyzed used pen injectors and needles from home-use and hospital settings.
- Employed techniques including MALDI-TOF MS, CLSM, and 16S/ITS high throughput sequencing (HTS).
- Developed a mathematical model to simulate contamination risks.
Main Results:
- Injection site microflora density was ~10^2 cells/cm^2, with higher bacterial presence in individuals with diabetes.
- Staphylococcus aureus was more prevalent on the abdomen of individuals with diabetes.
- The vast majority of needles (95%) and cartridges (86%) showed no biological signal.
- Mathematical modeling indicated a low probability of bacterial penetration during injections.
Conclusions:
- Subcutaneous insulin injections carry a low risk of skin infection, contrary to concerns about needle reuse.
- The study supports the development of reusable injection systems, potentially offering pharmacoeconomic benefits and improved patient experience.
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