Mycobacteria/Spirochetes

Mycobacteria
What is the morphology of mycobacteria?
Chapter 20
Microbiology for Surgical
Technologists
Mycobacteria
An aerobic organism found in the soil and in warm and cold blooded animals such as humans, turtles, fish, snakes, and frogs
Non-motile and non-spore forming
Most commonly involve infections of the skin and respiratory system
Cultures can be taken from skin lesions, lymph nodes, eyes, and lungs

They are divided into three categories of growth
Slow growth: colonies are not visible until after seven days or more
Rapid growth: colonies are visible in less than seven days
Special growth: Organisms require special media and nutritional requirements
Mycobacterium tuberculosis
In 1882, Robert Koch isolated the organism responsible for tuberculosis
Eight years later he developed tuberculin
Prepared from killed tubercle bacteria cells
This was the basis for the development of the tuberculin skin test used today

Tuberculosis is a leading killer among infectious diseases
10 million new cases are reported each year, of which 3 million are fatal
They have a waxy cell wall that prevents phagocytosis
They need an environment high in oxygen concentration
Tend to infect the upper lobes of the lungs
Grow slowly with a doubling time of approx 20 hours
As opposed to Escherichia coli with a doubling rate of 20 minutes
Identification in the lab can take as long as 6 weeks
Highly contagious
Spread by droplets from sneezing, coughing or just talking
The health of the person inhaling the droplet determines if they will be infected
There has been an increase in the number of cases in the US
Mostly due to the AIDS epidemic

The bacteria establish themselves in the bronchioli or alveoli
Macrophages consume the tubercle cells but they not only survive but multiply inside the macrophages
Then the macrophages bursts releasing the incubated cells
Disease progression is in two paths
Primary path
Pulmonary lesions occur in the initial stage
Followed by an acute exudative stage that rapidly spreads via the lymphatic system
These lesions typically heal and leave scar tissue

Reflective path
Chronic form – new lesions continue to secrete the exudative fluid due to tubercle cells that survived the primary TB
Two types of lesions
Exudative lesion
Caused by the inflammatory response of the host
Contains liquid exudate
The lung tissue becomes necrotic
The lesions either heal or develop a small round nodule called a tubercle
Productive lesions
Do not have exudate
Consist of cells that surround the bacilli and form a granuloma
Eventually the inner part of the granuloma becomes calcified and the outside becomes a fibrous capsule
This is called a Ghon complex
It will die or will survive for many years
Diagnostic testing
Specimen collecting
Sputum : the most common method
Gastric aspiration
Bronchial washings or bx
Urine specimen
Cerebrospinal fluid
Bone marrow bx

Skin testing
Is a hypersensitivity test
Mantoux test, intradermal injection of antigen purified protein derivative (PPD)
Reaction occurs within 48 to 72 hours
Due to active macrophages responding
Produces redness and swelling at the injection site
A positive reaction indicates that the person has had a past TB infection, has been vaccinated, or has an active infection
X-rays, clinical examination, and specimen collection are scheduled
Individuals that test positive with no disease are treated with antibiotics for one year
Active infections can be treated for up to two years
There have been reports of multidrug-resistant cases
“strain W” is one of the more virulent strains
Some strains have emerged that cannot be treated with any antibiotics
A vaccine was developed in 1921
Bacille Calmette-Guerin (BCG)
Provides partial protection, of a duration unknown, and is not reliable
Made from the closely related M. bovis
Not routinely given in US because it interferes with the skin test that is relied upon for diagnosis
Mycobacterium leprae
The bacteria that causes leprosy
Formal name is Hansen’s disease
An ancient disease described in the bible and other literature
Individuals were often shunned and isolated from the society
Leper colonies
Closely related to M. tuberculosis
Both have the waxy cell wall, and grow slowly
It prefers cooler areas of the body
Fingers, toes, ears, nose
Infects both the skin and the peripheral nervous system
Resulting in severe, disfiguring skin rashes and loss of sensation
Most likely transmitted by direct contact or nasal secretions
Three to five years after infection the pt will develop indeterminate leprosy
A few indiscriminant skin lesions will form with no effect on the nerves
Bx reveals early nerve damage and infection
Untreated the infection progresses to either the tuberculoid form or the lepromatous form (the second causing severe defroming damage)
Skin lesion can be either flat or raised
Bone and cartilage are often damaged
Facial features become thickened and are referred to as leonine (lion like)
Toes and fingers may have to be amputated
For ages there was no progress in leprosy research because the organism could not be grown in vitro
Even with human tissue
It was found that it could be grown with the use of armadillos
Vaccines have been developed but are still in the experimental stages
Surgical Implications
All medical personnel are fitted with respirator masks to treat TB patients
Care must be taken in bronchoscopies to insure that brochial washings and bx are contained
Decontamination of the instrumentation must be thorough to prevent cross contamination with other patients
A small percentage of pts will require a thoracotomy for a lobectomy or complete pneumonectomy
Bronchoscopy
Spirochetes
Chapter 21
Microbiology for Surgical Technologists
Spirochetes
Are long, snakelike organisms that appear as tight coils under the microscope
Resemble a telephone cord or corkscrew
They are propelled through fluids by axial filaments attached to each pole of the cell
The filaments are encased in a G- outer sheath that surrounds the bacterium, making them internal flagella
Spirochetes
These filaments rotate under the sheath along the cells longitudinal axis spinning the cell like a corkscrew
This allows the cell to swim faster in high-viscosity liquids and penetrate tissues
Many spirochetes are saprophytes and can be found in soil, sewage,decaying matter, and standing water
Spirochetes
There are three species that cause disease in humans
Treponema
Borrelia
Leptospira
Treponema
Are a normal flora of the oral cavity
The diseases that it causes are called treponematoses
They are characterized by distinct primary, secondary, latency and tertiary clinical stages
They are delicate, requiring pH 7.2 – 7.4, temp range of 30 to 37 degrees Celsius, and a low oxygen environment
Treponema
Treponema are thin and coiled tightly
They cannot be grown in vitro
What does in vitro mean?
Treponema pallidum
There are four subspecies of T. pallidum
T. pallidum pallidum
T. pallidum pertenue
T. pallidum endemicum
T. pallidum carateum
Treponema pallidum pallidum
The most virulent of spirochetes
Causes
Syphilis is a slow-evolving disease with a short symptomatic period, due to the multiplication of the bacteria, and then a prolonged asymptomatic period
It needs a moist dark environment to survive
Which makes genitalia the perfect media for propagation
The main means of transmission is through sexual contact, but it can be transmitted through blood transfusions, needle sticks, transplacental transfer, mother’s milk and saliva
There are estimations that 50% of persons that are sexually exposed to the disease will not contract it
It cannot live outside of the body for longer than 2 hours

In the 1400’s syphilis was treated with mercury
This did not treat the patient, but it did poison them
They also used blood letting
This didn’t treat the disease either, and more than likely infected the practitioner

It is believed that Columbus and his crew brought the bacteria back from the new world, triggering the “Great Pox” epidemic in Europe in the sixteenth century
Each country blamed their neighbor for the disease
The English called it the “French pox”
The French called it the “Italian pox”
In 1910 Paul Ehrlich developed Salvarsan
An arsenic derivative that would destroy the pathogen
It was toxic and hard to administer
Today syphilis is treated with an injection of PCN, or a two week course of tetracycline
The first stages of the disease is curable, so early detection is crucial
Syphilis is introduced into the body through cuts in the skin or small abrasions of the mucous membranes.
Adults age 20 – 24 are most often affected
10% of pts also have gonorrhea
The use of a condom will prevent infection
Clinical Stages of Syphilis
Primary stage
Organism multiplication at the site of entry produces a localized infection
10 to 60 days later a hard ulcer (chancre) appears, that heals itself in 3 to 6 weeks
This is followed by painful, swollen lymph nodes
If untreated, will progress throughout the body into the secondary stage
Latent stage
Appears between the primary and secondary phases
No obvious symptoms are present
May experience vague discomforts as the spirochete burrows into the host’s tissues
Host may or may not be infectious during this period, but expectant mothers can pass the disease on to unborn children
Secondary Stage
Can involve any organ in the body
CNS is most often infected
One to six months after chancre heals, a pink rash appears on the palms, soles of feet, and genitals
Accompanied by fever, headaches, sore throat, joint pain, and weight loss
Tertiary stage
The spirochete inflicts serious damage to infected tissue forming gummas, or syphilomas
The bacteria can invade any part of the body and is labeled according to the system or organs that are affected
Neurosyphilis, manifests in the CNS
Resulting in dementia, or specific neurologic deficits depending on the area of the brain involved
Can involve the posterior sensory tracts of the spinal cord resulting in numbness of the extremities; called tabes dorsalis
Results in a characteristic gait, and deformed knees
Without feedback from the brain, the joints become malformed from the misuse

Cardiovascular syphilis creates similar symptoms as CV disease, can lead to misdiagnosis
Damages heart valves and the small vessels that feed the aorta
Can cause aortic aneurysms, aortic dilatation, or coronary arteries may become occluded and cause myocardial infarction
Clinical Stages of Syphilis
(continued)
Tertiary stage (continued)
The spirochetes may invade the skeletal system, destroying bone tissue
Pt may experience frequent fractures
Can damage the nasal and palate bones resulting in serious disfigurement requiring extensive facial reconstruction
Treponema pallidum pallidum
(continued)
Diagnosis of syphilis
In 1906, the Wasserman test was developed
Detected the presence of the bacteria through its reaction to substances in the blood
Today the Venereal Disease Research Laboratory (VDRL) test and the rapid plasma reagin test is used
Not completely reliable because it needs a high level of antibodies in the blood for diagnosis and they are not significantly high in the primary stage
Treponema pallidum pallidum
(continued)
The best diagnosis for syphilis is through in vivo culturing
Involves intratesticular inoculation of infected exudates into a rabbit
This is expensive and time consuming
Not to mention, it kills the rabbit
Treponema pallidum pertenue
Produces YAWS, which is similar to syphilis but is not sexually transmitted
Begins as an inflammatory lesion of the skin (mother yaws) then papules form and are scratched and the disease spreads
After latency phase internal and external lesions appear, destroying skin, bones, and other tissue
Treponema pallidum endemicum
Causes endemic nonvenereal syphilis
Affects children of poorer regions of Asia, Africa, and India
Can be transmitted by contaminated water or direct contact
The ability to maintain proper hygiene may prevent the spread of the disease
Treponema pallidum carateum
Causes disease known as pinta or caratae
Occurs primarily in tropical Central and South America
Begins as painless primary papules, followed by secondary papules on the hands, feet, and scalp
Is not fatal, but can cause disfigurement

Borrelia
Thicker and less curved than treponemes
Borrelia burgdorferi
Causes lyme disease
Transmitted by ticks
Ixodes
Scapularis
(Deer Tick)
First thought to be only one strain, it is now known to have at least 100 strains in the US alone
It is very large and highly motile
It differs from other strains of Borrelia in that it has a “slime layer” made of glycoproteins that protects it from the host’s immune system
The bacteria enter the healthy cell which then causes the digestive enzymes within that cell to dissolve the slime layer
It then drapes itself in a portion of the cell wall, which disguises it from the immune system of the host
It can remain inanimate for years, antibiotics will not destroy it, causing relapse of the victim
Symptoms
The disease affects many of the body systems
Pt can test negative for the disease and be misdiagnosed with fibromyalgia, chronic fatigue syndrome, or multiple sclerosis
Symptoms include skin lesions, muscle pain, headache, stiff neck, fatigue, and lymph node swelling
If symptoms are left untreated they can lead to complications such as meningitis, encephalitis, Bell’s palsy, myocarditis, or arthritis
Diagnosis
Small amounts of the spirochete in the blood stream usually prevent diagnosis
But unlike treponemes, in vitro culture is possible
The enzyme-linked immunosorbent assay (ELISA) Lyme test and Western blot test are the most common diagnostic tools
Treatment
Tetracycline and erythromycin are an effective treatment, especially in the early stages of the disease
Antibiotic treatment is usually effective in later stages, but damage to joints and nervous system may require further treatment

Leptospira
Are thin, flexible, tightly coiled, and curved at the end
Only visible using darkfield microscopy
Leptospira interrogans
Only one species with 180 strains
Most are harmless and live in sewage, stagnant water, and occasionally feces
The disease caused is called leptospirosis
An acute febrile disease passed to humans via contact with contaminated animal urine
Especially dogs, livestock or rodents

Drinking contaminated water from a stream is a common method of infection, but can also be contracted through a break in the skin
Walking barefoot in wet contaminated areas with standing water is not suggested

Homework
Questions for further study
Page 225, # 3 and 5
Page 237, # 2 and 4

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Elaine Maxwell