Episode 155: Diabetic Foot Infection Guidelines - a podcast by Rio Bravo Family Medicine Residency Program

Episode 155: Diabetic Foot Infection Guidelines

Future Dr. Perez presents the updates on lung cancer screening by the American Cancer Society. Future Dr. Danusantoso explains the classification, diagnosis, and treatment of diabetic foot infections according to the guidelines published by the International Working Group on the Diabetic Foot (IWGDF). Dr. Arreaza adds comments and anecdotes.  

You are listening to Rio Bravo qWeek Podcast, your weekly dose of knowledge brought to you by the Rio Bravo Family Medicine Residency Program from Bakersfield, California, a UCLA-affiliated program sponsored by Clinica Sierra Vista, Let Us Be Your Healthcare Home. This podcast was created for educational purposes only. Visit your primary care provider for additional medical advice.

Intro: Lung cancer screening update.
Written by Luz Perez, MSIII, Ross University School of Medicine. Editing by Hector Arreaza, MD.

Hello, my name is Luz Perez and today I will talk about lung cancer screening.

As a reminder, lung cancer is the top cause of cancer-related death in men and women worldwide. In the United States, lung cancer causes the death of about 154,000 people each year[4]. 

Smoking is the most significant risk factor for developing lung cancer, a risk that directly correlates to how much and how long a person has smoked[2]. Despite the efforts to decrease lung cancer-related deaths, which include screening of patients at risk and counseling on smoking cessation, many patients go undiagnosed in part because lung cancer can be asymptomatic but also because many people at risk did not meet the criteria for screening, according to previous guidelines… 

BUT On November 1, 2023, the American Cancer Society updated its guidelines for lung cancer screening to decrease mortality by lung cancer in the US. 

The updated lung cancer screening guidelines were published in November, which is Lung Cancer Awareness Month. This guideline aims to expand eligibility criteria for lung cancer screening. 

Previously, the guidelines covered people only between the ages of 55-74 who were current smokers or had quit within the past 15 years and had a 30 or more pack-year smoking history[3].

The new guidelines recommend annual screening with low-dose CT (LDCT) scan for people who are 50-80 years old who are current or former smokers and who have a 20 or more pack-year of smoking history [1]. 

This change means that about 5 million people who would previously not qualify for screening are now eligible for this potentially lifesaving screening exam.

Additionally, the American Cancer Society emphasizes the significance of shared decision-making between patients and healthcare providers on lung cancer screening and smoking cessation. This includes ways to help patients stop smoking by providing counseling and interventions including medications. 

For patients who are eligible for screening, having a full discussion of the lung cancer screening process including the purpose of the procedure, risks and benefits of low-dose CT, and recommendations from other organizations, is key in the shared decision-making process[1]. 

Perhaps, the most important step in the implementation of these new guidelines is ensuring that medical professionals talk to their patients about them and make them aware of the importance of screening for lung cancer. In this way, we can reduce mortality and other consequences of this devastating disease. 

Written by Maria Danusantoso, MSIV, Ross University School of Medicine. Editing by Hector Arreaza, MD.

Update to Guidelines for Treatment of Diabetic Foot Infections

Introduction

In October 2023, the International Working Group on the Diabetic Foot (IWGDF) and the Infectious Disease Society of America (IDSA) collaborated and published an update to the 2019 guideline on the diagnosis and management of infections of the foot in persons with diabetes mellitus.

The present guidelines include a list of 25 recommendations for diagnosis and management and clinically useful figures and tables including a treatment algorithm, a classification system for defining diabetic foot infections, and empirical antibiotic therapy according to clinical presentation and microbiological data.

The goal of this episode is not to provide an exhaustive review of the updated guidelines and algorithms but to highlight what I believe are the most important recommendations. I hope this brief presentation is viewed as an introduction and that this encourages you, the listener, to independently read the guidelines in full and implement them into your own clinical practice.

Wound Colonization Versus Wound Infection

Before jumping into some of the recommendations, I want to take some time to discuss briefly how to classify diabetic foot infections. Most clinicians, including myself, will see a patient with diabetes with a foot ulcer or wound and want to treat it with antibiotics or admit the patient to the hospital. However, the updated guidelines propose that antibiotics and/or admission are not always indicated. 

For clinicians, there needs to be an awareness that wound colonization and wound infection are not the same. Wound colonization by bacteria is defined by the presence of bacteria on a wound surface without evidence of invasion of the host tissues. Colonization, then, can be considered a constant phenomenon as we live in a bacteria-filled world. 

Comment: If we culture our intact skin, we may find pathogens, that’s why wound cultures even if they are positive, do not indicate there is infection. Tell us about infection.

In contrast, wound infection is a disease state caused by the invasion and multiplication of microorganisms in host tissues that induce an inflammatory response in the host, usually followed by tissue damage. Therefore, since all wounds are colonized – often with potentially pathogenic microorganisms – we cannot define wound infection using only the results of wound cultures. Instead, diabetic foot infections are a clinical diagnosis based on the presence of manifestations of an inflammatory process involving a foot wound located below the malleoli. These signs and symptoms of inflammation may be masked in persons with diabetes especially if they have some level of baseline peripheral neuropathy, peripheral artery disease, or immune dysfunction.

Classification of Diabetic Foot Infections.

To assist with the classification of diabetic foot infections, the updated guidelines include a table for defining the presence and severity of an infection of the foot in a person with diabetes. Again, diabetic foot infections are a clinical diagnosis, and the clinical classification of infection can be described as: 

1) uninfected, 2) mild, 3) moderate +/- O if osteomyelitis is present, 4) severe +/- O if osteomyelitis is present. 

Uninfected has no systemic or local symptoms or signs of infection. 

Mild infection is when at least two of the following are present: local swelling or induration, erythema between 0.5-2 cm around the wound in any direction, local tenderness or pain, local increased warmth, purulent discharge, and there is no other cause of an inflammatory response of the skin present (e.g., trauma, gout, acute Charcot neuro-arthropathy, fracture, thrombosis, or venous stasis).

Moderate infection is without systemic manifestations and involves erythema extending 2 cm or more from the wound margin and/or involves tissue deeper than skin and subcutaneous tissues (e.g., tendon, muscle, joint, and bone) +/- the presence of osteomyelitis. The surrounding erythema and the depth of wound are key element in the classification of the wounds. 

Severe infection is associated with systemic manifestations and meets systemic inflammatory response syndrome (SIRS) criteria as manifested by 2 or more of the following: temperature below 36°C or above 38°C, heart rate greater than 90 beats per minute, respiratory rate greater than 20 breaths per minute, white blood cell count greater than 12,000/mm3 or greater than 10% immature (band) forms +/- presence of osteomyelitis. 

Features of Osteomyelitis on Plain X-Ray

We have mentioned osteomyelitis quite a few times in this episode, so what are some ways we can diagnose osteomyelitis? Most commonly, osteomyelitis is diagnosed via imaging either with plain X-rays  or MRI. When looking at plain X-rays, there are a few features that are characteristic of diabetes-related osteomyelitis of the foot of which we should be aware regardless of our status as radiologists. 

Some of these features include bone sclerosis with or without erosion, abnormal soft tissue density or gas density in the subcutaneous fat, or new or evolving radiographic features on serial images spaced several weeks apart such as loss of bone cortex, focal demineralization, periosteal reaction or elevation. Changes in x-ray may be a late finding and indicate that the osteomyelitis is established.

General Treatment Recommendations for Diabetic Foot Infections

In the updated guidelines, recommendation 11 states to not treat clinically uninfected foot ulcers with systemic or local antibiotic therapy when the goal is to reduce the risk of new infection or to promote ulcer healing. 

As previously said, diabetic foot infections are a clinical diagnosis. So if clinically the wound does not meet criteria to be classified as a mild, moderate, or severe infection, this recommendation proposes that no antibiotic treatment is the best treatment so as not to expose patients to potentially unnecessary and harmful treatment and to not promote antibiotic resistance in patients, which would potentially make treating diabetic foot infections more challenging in the future. 

We still want to very closely monitor the wound every 2-7 days and promote wound healing with pressure offloading, keeping the wound and the surrounding skin clean and dry, and other non-antibiotic management for local wound care.

What are some common bacteria?.

When it is indicated to treat diabetic foot infections per the guidelines, recommendation 14 states to target aerobic gram positive pathogens only for people with a mild diabetes related foot infection. These pathogens include beta hemolytic streptococci and Staphylococcus aureus including methicillin-resistant strains if indicated. Additionally, recommendation 15 advises not to empirically target antibiotic therapy against Pseudomonas aeruginosa in cases of diabetes-related foot infection in temperate climates. However, it is appropriate to use empirical treatment of P. aeruginosa if it has been isolated from cultures of the affected site within the previous few weeks or in a person with moderate or severe infection who resides in tropical/subtropical climates.

Antibiotic Treatment Duration Recommendation

The final recommendation we have time to discuss in this episode is regarding antibiotic treatment duration. 

For mild infections, oral antibiotics (such as cephalexin or Bactrim) for a duration of 1-2 weeks is appropriate. However, if the infection is improving but is extensive and is resolving slower than expected or if the patient has severe peripheral artery disease, it is reasonable to consider extending treatment for up to 3-4 weeks.

For moderate or severe infections without osteomyelitis, a total treatment duration of 2-4 weeks is recommended starting initially with IV antibiotics before transitioning to oral antibiotics. Antibiotic selection will depend on multiple factors, such as recent antibiotic use, or MRSA risk factors. For example, if the patient took antibiotics recently, they could receive Zosyn® and ceftriaxone. 

If osteomyelitis is present, antibiotic treatment duration can be anywhere from 2 days to 6 weeks depending on the amount of source control achieved. Ideally, we should wait to have bone resection before giving antibiotics, but we know that antibiotics are given promptly in the ER.

In the cases of a resected infected bone or joint (when complete source control is achieved), a duration of 2-5 days is recommended, starting with IV antibiotics before transitioning to oral antibiotics. 

If there is minor amputation of the infected foot but there remains a positive wound culture or positive margins are seen on pathology (inflammatory cells are seen at the proximal margin of the amputated section), a 3-week antibiotic treatment duration is recommended, again starting with IV before transitioning to oral antibiotics.

For diabetes-related foot osteomyelitis without bone resection or amputation, a 6-week course of antibiotics is recommended, again initially with IV antibiotics before transitioning to oral. 

In all the situations where there is a transition from IV to oral antibiotics, this transition may only occur once there are clinical signs of improvement, for example, improving erythema surrounding the wound, resolution of tenderness or purulent drainage, or SIRS criteria is no longer met.

Summary: For more details regarding the 2023 update to the guidelines on the diagnosis and treatment of foot infection in persons with diabetes, please refer to the complete guidelines which can be accessed on the IWGDF Guidelines website and via the citations listed in the References. As a reminder, this podcast episode is not an exhaustive review of the guidelines, but, instead, a brief introduction to some of the recommendations. Thank you for listening and I hope you learned something new!

_____________________________

Conclusion: Now we conclude episode number 155 “Diabetic foot guidelines.” Future Dr. Perez started this episode with an introduction about the new guidelines to screen for lung cancer, then future Dr. Danusantoso gave an excellent summary about the classification and treatment of diabetic foot infections. Our patients with diabetes must have foot self-awareness and report any concerns to their family physicians or podiatrists so they can get prompt treatment.

This week we thank Hector Arreaza, Luz Perez, and Maria Danusantoso. Audio editing by Adrianne Silva.

Even without trying, every night you go to bed a little wiser. Thanks for listening to Rio Bravo qWeek Podcast. We want to hear from you, send us an email at RioBravoqWeek@clinicasierravista.org, or visit our website riobravofmrp.org/qweek. See you next week! 

_____________________

References:

1. McDowell, Sandy, New Lung Cancer Screening Guideline Increases Eligibility. American Cancer Society, published on November 1, 2023, Cancer.org. https://www.cancer.org/research/acs-research-news/new-lung-cancer-screening-guidelines-urge-more-to-get-ldct.html
2. Wolf AMD, Oeffinger KC, Shih TY, et al. Screening for lung cancer: 2023 guideline update from the American Cancer Society [published online ahead of print, 2023 Nov 1]. CA Cancer J Clin. 2023;10.3322/caac.21811. doi:10.3322/caac.21811. Link: https://pubmed.ncbi.nlm.nih.gov/37909877/
3. Moniuszko, Sara. Lung cancer screening guidelines updates by American Cancer Society to include more people. CBS News, updated on November 3, 2023. https://www.cbsnews.com/news/lung-cancer-screening-guideline-american-cancer-society-update/
4. Deffebach, M. E., & Humphrey, L. (2023). Screening for lung cancer. UpToDate. Retrieved November 6, 2023, UpToDate. https://www.uptodate.com/contents/screening-for-lung-cancer
5. Éric Senneville, Zaina Albalawi, Suzanne A van Asten, Zulfiqarali G Abbas, Geneve Allison, Javier Aragón-Sánchez, John M Embil, Lawrence A Lavery, Majdi Alhasan, Orhan Oz, Ilker Uçkay, Vilma Urbančič-Rovan, Zhang-Rong Xu, Edgar J G Peters, IWGDF/IDSA Guidelines on the Diagnosis and Treatment of Diabetes-related Foot Infections (IWGDF/IDSA 2023), Clinical Infectious Diseases, 2023; ciad527, https://doi.org/10.1093/cid/ciad527
6. Senneville, Éric et al. 2023. “IWGDF/IDSA Guidelines on the Diagnosis and Treatment of Foot Infection in Persons with Diabetes.” IWGDF Guidelines. Retrieved November 6, 2023 (https://iwgdfguidelines.org/wp-content/uploads/2023/07/IWGDF-2023-04-Infection-Guideline.pdf). 
7. Royalty-free music used for this episode: Gushito, “Gista Mista”, downloaded on November 16th, 2023, from https://www.videvo.net/ 

Further episodes of Rio Bravo qWeek

Further podcasts by Rio Bravo Family Medicine Residency Program

Website of Rio Bravo Family Medicine Residency Program