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Journal of Medical Cases

Case Report

Volume 4, Number 2, February 2013, pages 69-71

Transient bacteraemia due to Treponema amylovorum in a Renal Transplant Patient

Odontogenic bacteraemia is transient and well described; such bacteraemia occurs after dental procedure, but also after daily life activities; it may lead to distant site infections, and is associated with the development of cardiovascular disease [1]. Streptococci are the predominant organisms with Fusobacteria, Actinobacteria or Bacteroidetes [1]. Montagner et al [2] showed that Treponema species are implicated in acute endodontic infections, especially T. amylovorum isolated in 5/20 patients with infected root canals and 9/20 patients with acute apical abscesses. Siqueira and Rocas [3] investigated occurrence of T. amylovorum and found it in 2 of 31 cases (7%; 5% asymptomatic and 10% symptomatic). Currently, there are no data in the literature describing the presence of Spirochaetes inhabiting the oral cavity in blood.

Here we report the first case of an immuno-compromised patient who presented a bacteraemia due to Treponema amylovorum; then we discuss the interpretation of the presence of such a bacteria in blood.

The patient is a 30-year-old woman, followed in nephrology for 27 years; her renal history began in 1984 with a typical hemolytic uremic syndrome, leading to hemodialysis since 1987. She underwent three renal transplants (in 1989, 1995 and 2006), resulting in three rejections. The last one occurred in 2006, with graft dysfunction and return in hemodialysis on Canaud’s catheter in August 2010, three times a week. The patient also presents a peripheral arterial disease. Her treatment included prednisone 5 mg per day and tacrolimus 1.5 mg per day, but she stopped by herself these drugs in February 2011.

Since March 8, 2011, she has complained of a left iliac fossa pain in the renal transplant area, with fever (38 °C) without chills. Clinical examination just confirmed the pain, without contracture; the patient did not present any dental pain. One blood culture was sampled on March 10, and she was discharged from the hospital. The blood culture became positive after a 7 day incubation period and microbial diagnosis led to identify Treponema amylovorum.

On 15 March, the patient was admitted in the emergency unit for renal transplant’s pain, and she received an antalgic treatment with morphine; the body temperature was 37.9 °C. Biological results showed an elevated C reactive protein (86 mg/L), a leucocytes count at 10.6 G/L with a majority of neutrophils, the presence of an anemia with hemoglobin at 9.2 g/dL, an elevated creatinine at 406 µmol/L, urea at 10.6 mmol/L and an elevated potassium rate at 5.9 mmol/L. Two blood cultures, sampled on 17 and 18 March, remained negative after 5 days of incubation, the urine culture revealed 10⁶ leucocytes/mL with a polymicrobial flora at 10⁴/mL.

The bacteraemia was considered as a transient bacteraemia, from a dental origin. An oral cavity examination was realized on 10 May: three distal caries were identified on teeth 27, 36 and 37 with endodontic infection. A dental panoramic showed a focus of periradicular infections (Fig. 1), requiring dental extractions of these three molars, under antibioprophylaxis, that were realized one month later.

Click for large image

Figure 1. Dental panoramic showing periradicular infections on teeth 26-27-36 and 37.

So far, she never presented any symptoms in relation with this bacteraemia, apart the first febrile episode which has been associated to the transplant rejection. The valid diagnosis was transplant rejection, requiring the reintroduction of 20 mg/d of prednisone and transplantectomy on 1st April. The patient did not receive any antibiotic treatment, clinical outcome was favorable with apyrexia and cessation of pain.

In the laboratory, the diagnosis was made by blood cultures using the Bactec® vials (Plus Aerobic/F; Lytic/10 Anaerobic/F; Becton Dickinson) incubated 7 days at 35 °C in an incubator-rocker compartment. After incubation, direct microscopic examination revealed Gram negative helically shaped bacteria (7 microns long), suggestive of Treponema genus. These strictly anaerobic, motile bacteria do not grow easily on commonly used media. When identification by conventional methods fails or in case of the suspicion of non-culturable bacteria, the molecular diagnosis can often achieve a result [3]. We used PCR amplification and sequencing of the rrs gene encoding 16S ribosomal RNA. Sequences were compared to a database to allow specific identification (NCBI Blast: http://www.ncbi.nlm.nih.gov/genome?term=blast, last accessed November 11, 2012).

Transient bacteraemia, not exceeding 60 minutes after the procedure at risk, are well described after dental treatment procedures, and also after daily life activities such as eating, chewing or tooth brushing in individuals with periodontal inflammation [4]. Odontogenic bacteraemia certainly results from a breach in the oral mucosal barrier allowing the penetration of bacteria into the bloodstream from oral niches; besides, innate microbial factors may play a role, such as virulence factors that mediate tissue penetration and vascular invasion. Lockhart et al [4] inventoried in the literature 126 bacterial species reported in blood cultures following dental extractions or tooth brushing. These bacteraemia were characterized by low concentrations of bacteria in the blood and a rapid clearance of the bacteria by host defenses; those arguments could explain the difficulties to isolate new species or fastidious organisms.

The oral cavity is intensively colonized by bacteria (bacterial plaque from 10¹¹ and 10¹² CFU/g). More than 700 bacterial species have been isolated in the mouth, and about 20 species are usually cultured on commonly used media. Dental abscess is usually polymicrobial, including facultative or strict anaerobes, and non cultivable bacteria as Treponema, detected with molecular techniques [5]. Oral Treponema species may represent more than 50% of the polymicrobial flora of the dental plaque (70% of species are non cultivable), but less than 1% of the microorganisms in oral cavity of a healthy subject. T. denticola has been associated with periodontitis, with expression of a wide range of virulence factors that mediate tissue penetration, destruction and evasion of host immune responses [6]. T. denticola has also been detected in cardiovascular specimens (cardiac valves, aortic aneurysms), as well as others oral bacteria [7]. For T. amylovorum, few data are available on its pathogenicity, except in periodontal diseases; one study even reported no relationship between the presence of T. amylovorum in dental plaque and associated periodontitis [8].

Direct examination is highly evocative of a Treponema species, cultivation is often difficult, but recent advances in bacterial identification methods, such as 16S rRNA gene sequencing, showed the diversity of bacteria inhabiting the oral cavity [3, 9].

We describe the first isolation of T. amylovorum in a blood culture, in an immuno-compromised patient. This transient bacteraemia is thought to come from oral origin, with no immediate severe clinical consequence. This case report highlights the probable underestimation of cases of bacteraemia due to oral Treponema species. Recently, a statistically significant association of oral invasive Treponema with Alzheimer's disease has been postulated, using detection of species specific PCR and antibodies in the brains of these patients [10]. Early detection of periodontal pathogens could be useful to better prevent these various diseases, especially in patients with risk factors.

Acknowledgments

We thank Philippe Gautier for technical assistance. The authors deny any conflicts of interest related to this study.

Conflict of Interest

None.

Declaration of Funding

None.

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