Spirochaetes and Associated Diseases

Spirochaetes are a very unique group of bacteria but are responsible for a number of diseases, including dental conditions! This section will look at the basics of the bacteria as well as some examples of diseases.

Characteristics

• Anaerobic
• Gram-negative, however…
• No LPS!
• Spiral-shaped
• Variable genome
• Motility
  • Due to internal flagella – axial filaments are present within the periplasmic space (between the two membranes); the internal flagella are VITAL for the bacteria’ shape as well
  • Important virulence factor
• Slow growing and difficult to grow

Infections and Diseases

Lyme Disease (Borrelia burgdoferi)

Lyme disease is an example of a zoonotic infection. A zoonotic infection is one where there is an animal reservoir of infection which is then transmitted to humans via a zoonotic vector. Lyme disease is caused by the bacteria Borrelia Burgdoferi. The disease is transmitted by ticks. Ticks are ectoparasites and they feed on animals including birds, deer and rodents. When the ticks feed, they take in blood while releasing saliva in to the animal. The saliva is what contains the bacteria. Within the tick, the bacteria tends to replicate within the midgut until feeding. Ticks have 3 stages to their life cycles and they feed for up to 5 days in each stage. Therefore, a tick may then bite a human and pass on the disease (however, the disease can not be passed on from human to human).

Symptoms 

The disease has an acute and a chronic stage:

• Acute – these problems develop shortly after being bitten and include:
  • Flu-like illness
  • Development of erythema migrans (bulls eye rash) at the site of the bite
  • Development of other lesions distal to the site
• Chronic – these problems can develop anywhere between 1 week to 2 years post-infection and include:
  • Neurological problems: meningitis, encephalitis, motor nerve palsy, peripheral neuropathy
  • Cardiac problems
  • Arthralgia and arthritis
  • These symptoms are due to the bacteria spreading around the body

Borrelia burgdoferi has a number of virulence factors:

• Motility – the burrowing allows the bacteria to get around the body to numerous sites
• Surface lipoproteins (Osp A-D) – allowing antigenic shift (variation)
• Decorin-binding protein – allows host mimicry
• Manganese enzyme co-factor – allows survival in low iron environments

Treatment and Prevention 

The main method of treatment is by using doxycycline, however, if the infection becomes chronic then it can become a major problem and more difficult to treat. There is a vaccine developed against the OspA but it isn’t very effective and has many side effects. Prevention involves avoiding endemic areas as well as covering bare skin.

Leptospirosis and Weil’s Disease (Leptospira interrogans)

This bacteria is found in areas of stagnant water (rivers etc). The bacteria can be found in the urine of rats and dogs, which are the main reservoirs. The incubation period of the bacteria is around 1-2 weeks. Symptoms of Leptospirosis

• Febrile illness
• Flu-like illness
• Muscle pain
• Reddening of the eyes
• Diarrhoea

In a small percentage of cases, this condition can progress to Weil’s disease:

• Renal failure
• Jaundice and liver failure

The symptoms that develop are mainly due to the bacteria burrowing through blood vessels.

Treatment and Prevention

The main treatment is through the use of doxycycline. Avoiding areas of stagnant water are important for prevention.

Acute Necrotising Ulcerative Gingivitis/Periodontitis (Treponema vincentii)

A condition which involved Fusobacterium and Spirochaetes, which involves the spirochaete Treponema vincentii. It is often associated with individuals who are immunocompromised, e.g. HIV/AIDS. Symptoms

• Severe gingival pain
• Halitosis
• Gingival bleeding
• Interdental papillae ulcerated and necrosed

Treatment 

The main treatment is by using either metronidazole or hydrogen peroxide mouthwash.

Spirochaetes Summary

• Spirochaetes are gram-negative, anaerobic, motile bacteria WITHOUT an LPS.
• Zoonotic infections involve animal reservoirs of the bacteria with a zoonotic vector
• Lyme Disease is caused by Borrelia burgdoferi; spread by ticks; has both acute and chronic symptoms and is treated with doxycycline.
• Leptospirosis is caused by Leptospira interrogans; found in stagnant water; can lead to Weils Disease and is treated with doxycycline.
• ANUG is caused by Treponema vincentii amongst other bacteria and can be treated with metronidazole or hydrogen peroxide.

Quiz

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References and Recommended Reading

• Essentials of Microbiology for Dental Students
• Infectious Disease Essentials