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Bacterial structure and functions
Streptococcus pyogenes (Group A Strep)
Streptococcus agalactiae (Group B Strep)
Clostridium botulinum (Botulism)
Clostridium difficile (Pseudomembranous colitis)
Clostridium tetani (Tetanus)
Bacillus cereus (Food poisoning)
Corynebacterium diphtheriae (Diphtheria)
Bacillus anthracis (Anthrax)
Salmonella typhi (typhoid fever)
Legionella pneumophila (Legionnaires disease and Pontiac fever)
Yersinia pestis (Plague)
Vibrio cholerae (Cholera)
Francisella tularensis (Tularemia)
Bordetella pertussis (Pertussis/Whooping cough)
Haemophilus ducreyi (Chancroid)
Mycobacterium tuberculosis (Tuberculosis)
Mycobacterium avium complex (NORD)
Borrelia burgdorferi (Lyme disease)
Borrelia species (Relapsing fever)
Treponema pallidum (Syphilis)
Rickettsia rickettsii (Rocky Mountain spotted fever) and other Rickettsia species
Coxiella burnetii (Q fever)
Ehrlichia and Anaplasma
Gardnerella vaginalis (Bacterial vaginosis)
Borrelia species (Relapsing fever)
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animal transmission p. 147
lice p. 158
Alexandru Duhaniuc, MD
Borrelia is a genus of spirochetes, which are long, thin, spiral shaped bacteria, that spin or twist to move around.
The genus has two major groups. The first one is associated with Lyme disease and the most common species is Borrelia burgdorferi.
The second group is associated with relapsing fever and the most common species are Borrelia hermsii, Borrelia turicatae, Borrelia parkeri and Borrelia recurrentis.
Of the second group, the first three species cause tick-borne relapsing fever, while Borrelia recurrentis causes louse-borne relapsing fever.
By the way, you may know this already, but “louse” is actually singular for “lice” - so body lice are the vector that transmits Borrelia recurrentis.
Now, all Borrelia species have an outer membrane that contains a substance similar to lipopolysaccharides, an inner membrane, and a layer of peptidoglycan in a periplasmic space, which is the space between the inner and the outer membrane.
Since the peptidoglycan layer is thin, it doesn’t retain the purple dye used during Gram staining, so they’re classified as Gram-negative.
However, they can’t be easily visualized with Gram staining. Instead, they’re best seen with the Wright or Giemsa stain, which make the bacteria appear purple, and with dark-field microscopy, which make the bacteria appear white against a dark background.
Now, Borrelia species are motile, which means they can move around using long, thin filaments called endoflagella, which are located in their periplasmic space.
The filaments rotate in this space, between the outer membrane and the peptidoglycan layer, propelling the bacterium forward in a corkscrew-like motion.
Finally, the bacteria can be cultivated on Barbour-Stoenner-Kelly medium or by intraperitoneal inoculation of immature laboratory mice, but these tests are not widely available.
Now, Borrelia can enter the body one of two ways, depending on the type of relapsing fever.
So, in tick-borne relapsing fever, or TBRF, the bacteria enters the bloodstream through the bite of an infected tick.
Borrelia species are gram-negative spirochetes that cause relapsing fever. The characteristic feature of relapsing fever is the cyclical pattern of fever and afebrile periods. Transmission of Borrelia to humans generally occurs through the bite of an infected vector, commonly a tick or a louse. Lyme disease is the most common presentation of Borreliosis. Symptoms can include fever, headache, myalgia, and arthralgia. Borrelia burgdorferi is the primary causative agent of Lyme disease. Untreated Lyme disease can lead to neurologic sequelae, including meningitis and encephalitis.
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