Case Study: A Periodontal Infection Mystery
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Case study for patient with periodontal abscesses
Download a PDF of the full case study and the one-page summary below:

Case Study Summary

Background: A patient with extremely diligent oral hygiene and generally healthy lifestyle experiencing episodic periodontal abscesses with unknown etiology, along with bleeding during dental cleanings and heavy inter-dental plaque buildup. Discovery: - Multiple referrals to periodontal specialists, immunologists, and infectious disease experts - A salivary test analyzing only 13 common periodontal pathogens resulted in no significant findings - Bristle's comprehensive salivary test both detected and highlighted the offending pathogen. Serratia marcescens, a rare opportunistic pathogen, dominated over 75% of the patient’s oral microbiome - Existing research study showed potential viability of xylitol inhibiting Serratia marcescens Solution: - Patient incorporated xylitol in hygiene routine to reduce Serratia levels and oral probiotic to increase beneficial bacteria. Outcome: - Elimination of Serratia to undetected levels and no more abscesses, bleeding during cleanings, and inter-dental plaque, indicating a complete resolution of the disease.

Patient History

Gender & Age: Male in 40’s
Health History: No medications, monitoring glucose levels
Diet & Hygiene:
- Meticulous at-home hygiene including brushing 3x/day, floss 3x/day, and nightly waterpik - Diet without sugary substances
Clinical Assessment:
- No history of cavities - Severe bleeding during regular dental cleanings - Heavy inter-dental plaque buildup - Staining and calculus buildup
Periodontal Assessment:
- Generalized chronic moderate-advanced periodontitis with areas of 50% bone loss - Up to 5-7mm pockets
Primary Complaints:
- Episodic periodontal abscesses once every 1-2 months causing extreme pain - Water blisters in mouth that pop and ooze watery substance in extracted wisdom tooth areas
Other Notes:
- Mucosal sensitivity to Sensodyne and fluoride rinses

Seven Years of Diagnostic and Treatment Failure (2014 - 2021)

Patient completed Scaling & Root Planing therapy in 2014 and 2017 with no meaningful improvement in periodontal symptoms and abscessing.
In 2017, a salivary test was completed through the Temple University Kornberg School of Dentistry. The laboratory test resulted in no significant findings in analysis of 13 “Putative Periodontal Pathogens” (see Figure 1).
Patient was referred to a total of 4 periodontal specialists over the course of 4 years starting in 2018.
See Appendix A for periodontal charting over time.
Figure 1: No common periodontal pathogens were found in patient’s sample above critical percentage threshold level.
Figure 1: No common periodontal pathogens were found in patient’s sample above critical percentage threshold level.
“True long-lasting health is not achieved with crazy procedures and techniques. Often it's habit/lifestyle modulations. IFM - food is medicine comes to mind.” - Comments from Patient’s Dentist

A New Hope: Enter Bristle Salivary Testing (Nov. ’21)

General dentist referred patient to complete Bristle salivary oral microbiome test analyzing all 700+ bacterial species and fungi found in the oral cavity.
Summary of Test Results (see Figure 2):
  • Overall appears to have low scores in all oral health Condition Related categories
  • Commensal (beneficial) bacteria extremely low
  • Diversity score 0/10 signals a red flag to investigate
Individual Microbial Species Findings:
  • 86 total bacterial and fungal microbes detected
  • Out of all common periodontal pathogens, only F. nucleatum was detected in patient sample (comprising less than 0.01% of total microbiome)
  • Undetected: A. actinomycetemcomitans, C. rectus, E. corrodens, E. nodatum, P. micra, P. gingivalis, P. intermedia, T. forsythia, T. denticola
Figure 2: Note the Gum Inflammation score reported Low (0.4/10) on initial Bristle test because rare pathogens were not included in the scoring algorithm at the time (only common periodontal pathogens like red/orange complex bacteria)
Figure 2: Note the Gum Inflammation score reported Low (0.4/10) on initial Bristle test because rare pathogens were not included in the scoring algorithm at the time (only common periodontal pathogens like red/orange complex bacteria)

A Dysbiotic Nightmare: Single Pathogen Takeover

Upon reviewing the Raw Results breakdown of all 86 microbial species detected in Bristle’s report, one bacterial species was found in extraordinarily high abundance: Serratia marcescens (see Figure 3).
Bristle’s testing technology characterizes all bacterial species in a patient’s saliva, which allowed for the detection of the less common Serratia marcescens species. With an analysis of the complete oral microbiome, the Bristle report demonstrated not only the presence of Serratia, but also Serratia’s domination of the patient’s microbiome.
Figure 3: A snapshot of patient’s Raw Results from Nov. 2021 Bristle test
Figure 3: A snapshot of patient’s Raw Results from Nov. 2021 Bristle test
Relative Abundance: 78% of patient’s mouth is dominated by Serratia marcescens
Absolute Abundance: 100% percentile of Serratia marcescens levels compared to the general population pool

The Precision Medicine Journey (Nov. ’21 — May ’22)

Based on the initial Bristle test findings of low microbial diversity and high levels of Serratia marcescens, patient was referred to medical specialists for further evaluation.
Patient had multiple consultations with an Immunologist and an Infectious Disease Expert at the Sutter Health Palo Alto Medical Foundation. Evaluation included full blood panel and additional medical tests with no significant findings as to systemic health factors that could be influencing patient’s oral health symptoms.
Based on input from patient’s general dentist and specialist referrals, patient used Peridex rinse (Chlorexidine) for roughly 2 months beginning around December 2021.
Patient re-tested with Bristle in February 2022 — Serratia marcescens levels decreased but still comprised 56% of entire oral microbiome.
No change in periodontal abscessing, water blisters, and other clinical symptoms including bleeding and inter-dental plaque buildup.

Xylitol Discovery & Revised Treatment Plan (May 2022 Onwards)

In May 2022, Chief Scientific Officer of Bristle Dr. David Lin completed an exhaustive review of scientific literature related to Serratia marcescens and found:
  1. Studies from 2006 and 2016 showing Serratia marcescens as a rare pathogen in periodontal disease, found in fewer than 4% of individuals with severe disease (1, 2).
  1. Xylitol may be effective at inhibiting Serratia marcescens through a 2021 in vitro study (3).
Based on the literature, a revised treatment plan was formulated with two notable additions:
  1. Increasing commensal bacteria via oral probiotics with beneficial bacterial strains
  1. Reducing Serratia marcescens levels via xylitol
Updated Hygiene Routine (Starting June 2022):
  • Brush using hydroxyapatite toothpaste and floss 2x / day after breakfast and dinner
  • Before bedtime: use interdental cleaner, tongue scraper, and waterpik with warm water
  • Soak dental appliances including toothbrush, interdental cleaners, waterpik heads, and night guards in a dilute hydrogen peroxide and water solution 1 hour before use
  • Drink boiled water to reduce contamination
  • Increase intake of fermented foods like kefir
  • Take oral probiotics with L. reuteri 2x / day
  • Incorporate xylitol:
    • Initially: took xylitol mints several times a day which led to bloating and bowel irritation
    • Switched to: rinse with xylitol solution 3x / day after each meal which alleviated issues with no ingestion of xylitol

A Positive Shift to Health and Stabilized Oral Microbiome

“Dr. Lin and his team at Bristle have been instrumental in my journey to better oral health. Not only did they find out the pathogen - Serratia marcescens - through the Bristle testing, but they found one important part of my treatment regimen, which was to combat the pathogen with Xylitol. I no longer suffer from the constantly recurring gum abscesses which, before the Bristle testing, had puzzled the very best periodontists in the field.” - Patient Testimonial

Key Outcomes with Xylitol and Probiotics in June 2022:

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⭐ Serratia marcescens levels dropped to zero

Patient re-tested with Bristle in July 2022 only 1-2 weeks after starting to consume xylitol mints and Serratia abundance was still elevated at 61% of entire microbiome.
In follow-up tests after continued xylitol use, Serratia marcescens abundance dropped to 0 and was undetected in patient’s sample (October 2022, February 2023, April 2023).

⭐ No more abscesses & significant improvement in clinical symptoms

Frequent abscesses ~6-9x a year reduced to no abscesses since approximately January 2023.
No longer has bleeding during dental cleanings and very minimal inter-dental plaque, calculus and staining.
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⭐ Commensal bacteria increased dramatically & Diversity within range

Commensal (beneficial) bacteria scores on Bristle testing went from 0.3 out of 10 on initial test (November 2021) to 9.5+ in October 2022, February 2023, and April 2023 follow-up tests.
Bacterial diversity went from 0 out of 10 (extremely low) on initial test to 1.5+ (within healthy range) in last 3 follow-up tests.

⭐ Gum Inflammation score decreased from 9.9/10 to less than 5/10

Patient’s Gum Inflammation score on Bristle test was 9.9/10 in July 2022. Following xylitol and probiotic use, the score has come down to between 0 and 4.5 out of 10 over last 3 tests.
Note: the 0.4 and 2.6 out of 10 scores for patient’s initial 2 tests in November 2021 and February 2022 are due to Serratia marcescens not being included in Bristle’s Gum Inflammation scoring algorithm at the time (only common periodontal pathogens).

Concluding Remarks

Despite extreme dedication to improving their condition, this patient suffered for years without resolution. Traditional clinical diagnosis and treatments were unable to detect the root cause of the disease. Even existing salivary testing methods were unable to elucidate the underlying cause due to specific pathogen detection and problem-focused testing methods rather than holistic testing.
In addition to identifying the little known pathogen, Bristle's testing modality was also able to convict the pathogen as the exact source of the disease by showing how it caused dysbiosis in the entire oral microbiome.
Furthermore, the precise treatment was discovered and verified to have cured the disease by showing the elimination of the offending pathogen and the restoration of a healthy oral microbiome in subsequent tests.
This case highlights the breakthrough advantages for both diagnosis and treatment that Bristle’s comprehensive oral microbiome salivary testing provides.
“The Bristle tests help guide our efforts, as radiographic bone levels and perio charting couldn't capture what was happening nearly as clearly and quickly as his microbiome shifts did!” - Comments from Patient’s Dentist

Appendix A

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