Learning medicine is hard work! Osmosis makes it easy. It takes your lectures and notes to create
a personalized study plan with exclusive videos, practice questions and flashcards, and so
much more. Try it free today! With Leptospira, “lepto” means thin, and
“spira” means coil. So Leptospira is a genus of spiral bacteria
known to cause leptospirosis, a zoonotic infection, meaning it can be transmitted from animals
such as rodents, to humans; especially people who work in sewers and waters contaminated
by these animals’ urine. The Leptospira genus has over 20 species,
and the most common species that causes leptospirosis in humans is Leptospira interrogans. Now, Leptospira is a tiny spiral bacteria,
that stains poorly with Gram staining, because it doesn’t retain the Gram dyes well, so
it’s classically considered gram-negative. It’s also too tiny to be seen with a light
microscope, so to visualize it, a darkfield microscope with use of immunofluorescence
is required. Leptospira is also a motile bacteria because
it has flagella that help it move around. Finally, it doesn’t form spores and it’s
aerobic, meaning it needs oxygen to grow. Currently, little is known about the pathogenesis
of this bacteria, but we do know that it possesses a number of virulence factors, which are like
assault weaponry that help it attack and destroy the host cells. These include toxins and some immunogenic
molecules such as lipopolysaccharide, or LPS, that triggers an immune response, causing
inflammation. For example, Leptospira interrogans, the most
common cause of leptospirosis, has adhesins, which are proteins that help this bacteria
attach to the host’s cells – usually epithelium, monocytes, and macrophages. It also releases Sphingomyelinase C toxin,
which destroys red blood cells as well as the endothelium of the capillaries, causing
hemorrhage. Most commonly, Leptospira gets into the host
system via abrasions or cuts on the skin. Alternatively, it can get in through the conjunctive
of the eyes, especially in people who go swimming in contaminated waters. Rarely, infection can follow eating contaminated
food. Serious problems start when this bacteria
gets into the bloodstream, from where it can move to infect other organs. This typically happens in two stages. In the first stage, there’s an immune response
to bacteremia, which clinically manifests as fever, but the bacteria are confined to
the bloodstream and there are no signs of end-organ damage. In the second stage, also known as Weil disease,
the infection becomes more severe, as the bacteria spread to almost all internal organs. Frequently affected organs include the liver,
where the bacterial toxins damage liver sinusoids and hepatocytes, causing bilirubin to spill
into the bloodstream – which clinically translates as jaundice. When the lungs are affected, the toxins damage
the alveolar-capillary membranes, which can result in bleeding within the alveoli. If Leptospira gets to the kidneys, it may
infect the interstitium, causing interstitial nephritis, or it may cause an inflammatory
reaction that damages the renal tubules, resulting in acute tubular necrosis. Finally, sometimes the bacteria can even migrate
from the bloodstream, and use its toxins to break through the endothelial cells that make
up the blood-brain barrier to get into the cerebrospinal fluids or CSF, causing meningitis. Risk factors for leptospirosis include some
professions, like people who work in rice-paddies, sugarcane plantations, or people who swim
or wade in waters contaminated by animal urines. Environmental risk factors include hazards
like floods, because contaminated waters are everywhere. OK, symptoms of leptospirosis depend on the
phase of the infection. In the first phase, there are non-specific,
flu-like symptoms like muscle pain, headache, chills, and fever. With conjunctivitis, there may be photophobia
and conjunctival suffusions, which is when the eyes gradually become red, but there’s
no tearing or discharge. In the second phase, signs and symptoms depend
on the affected organ. With liver damage, there may be jaundice. With kidney damage, there may be signs of
renal failure like reduced urine output and fluid retention, which leads to a puffy face
and swollen legs, ankles and feet. When the lungs are affected, symptoms include
a cough, dyspnea, which is difficulty breathing, as very as hemoptysis – or blood in the sputum. Finally, with meningitis, there may be headaches,
fever, and a stiff neck. Diagnosing leptospirosis is done with serologic
tests such as ELISA, that typically consists of detecting antibodies against leptospira
antigens in one’s serum. Another way to diagnose leptospirosis is by
identifying the bacteria in biological samples. This can be done using a darkfield microscope,
or with PCR, that detects bacterial DNA. Leptospirosis is treated with penicillin G,
and doxycycline can be used as an alternative. When multiple organs are affected, supportive
therapy may be required, like IV fluids, respiratory support, and possibly blood transfusions. Alright, as a quick recap, Leptospira is a
genus of tiny spiral gram-negative bacteria that can be seen under a darkfield microscope. It’s a motile and aerobic bacteria, and
it doesn’t form spores. Leptospira causes a zoonotic infection called
leptospirosis, which has two phases. During the first phase, there are non-specific
symptoms such as fever and headache. During the second phase, also called Weil
disease, there may be signs of end-organ damage like jaundice, a cough, dyspnea and hemoptysis,
reduced urine output and fluid retention, depending on the affected organs. Diagnosis is done with ELISA, by visualizing
the bacteria under darkfield microscopy, or with PCR to detect bacterial DNA. Treatment is done with penicillin G
or doxycycline.

Leave a Reply

Your email address will not be published. Required fields are marked *