Lyme disease is an infection caused by Borrelia burgdorferi, a spirochete that is found in deer ticks of genus Ixodes. Lyme disease was named in 1977 after arthritis was observed in clusters in children in Lyme, Connecticut. An infected tick can transmit B. burgdorferi to the humans and animals that it bites. If left untreated, the B. burgdorferi can cause a systemic infection by traveling through the bloodstream and establishing itself in various body tissues. Lyme disease is most prevalently found in north-eastern United States.
Microbial Characteristics and Virulence:
Borrelia burgdorferi is not classified as either Gram-positive or Gram-negative. When B. burgdorferi is Gram-stained, the cells stain a weak Gram-negative by default, as safrin is the last dye used. B. burgdorferi has an outer membrane that contains an LPS-like substance, an inner membrane, and a periplasmic space which contains a layer of peptidoglycan. They have endoflagella which are contained within the periplasmic space. It can be cultivated on a modified Kelly medium called BSK (Barbour-Stoenner-Kelly). BSK solidified with 1.3% agarose allows the production of colonies from single organisms. The spirochete grows more slowly than most other bacteria dividing once after 12-24 hours. B. burgdorferi resembles other spirochetes in that it is a highly specialized, motile, two-membrane, spiral-shaped bacteria which lives primarily as an extracellular pathogen. One of the most striking features of B. burgdorferi as compared with other eubacteria is its unusual genome, which includes a linear chromosome approximately one megabase in size and numerous linear and circular plasmids. Long-term culture of B. burgdorferi results in a loss of some plasmids and changes in expressed protein profiles. Associated with the loss of plasmids is a loss in the ability of the organism to infect laboratory animals, suggesting that the plasmids encode key genes involved in virulence.
Lyme disease usually presents with a characteristic “bull’s eye rash”, erythema migrans, along with fever, fatigue, headache, muscle aches, and joint aches. The incubation period from infection to onset of the rash is typically 1-2 weeks. Some patients may be asymptomatic and present with only non-specific symptoms. B. burgdorferi disseminate from the site of the tick bite through the blood stream. There are three clinical stages of Lyme disease: 1) the Localized Early (Acute) Stage, 2) the Early Disseminated Stage and 3) the Late Stage. The acute stage is characterized by solid red or bull’s eye rash at the site of the bite, swelling of the lymph glands near the bite, generalized achiness and headache. The early disseminated stage is characterized by two or more rashes not at the site of the bite,...