Download Mycobacterium

Mycobacterium
aerobic, non-endospore-forming rods
myco = “fungus-like”
Page 355
Mycobacterium
• distinctive cell wall: waxy, water-resistant
layer
• resistant to stress: e.g. drying
• few antimicrobial drugs can enter the cell
• nutrients enter slowly = slow growth rate
Mycobacterium avium
• Second most common Mycobacterium infection
• Readings question #1:
What is MAC? Who is susceptible to this
infection? What are the common symptoms?
What organism is responsible? Where is it found?
 portal of entry: respiratory tract
 Transmission: inhalation
MAC
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common bacteria
weakened immune system: “opportunistic”
blood infections, hepatitis, pneumonia
combination of antibiotics:
– azithromycin (Zithromax)
– clarithromycin (Biaxin)
– 3 other drugs
Mycobacterium tuberculosis
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“opportunistic”
slender rod, obligate anaerobe
rods grow slowly and tend to grow in clumps
resistant to conventional staining
Mode of Transmission
• fine particles: 1-3 bacilli reach the lungs
Readings question #2:
Explain the process of M. tuberculosis
attacking macrophages. When does the tubercle
form? What happens when the macrophages die?
Describe the process of liquefaction and its end
result. What is cavitation?
Ghon Complexes
dormant disease: lesions calcify (Figure 25-3)
Miliary Tuberculosis
• cardiovascular and lymphatic systems
• defenses overwhelmed
• weight loss, coughing (blood), general malaise
Treatment
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streptomycin
multiple drugs
chemotherapy for months
tubercle bacillus grows slowly
hidden by macrophages or other locations
difficult to reach with antibiotics
Diagnosis
• Tuberculin Skin Test: purified protein derivitive
• Mantoux Test: most accurate tuberculin test
• Induration
induration
Tuberculosis Vaccines
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BCG: live culture of Mycobacterium bovis
avirulent culture
available since the 1920’s
certain children at high risk
positive reaction to tuberculin skin tests
not effective for adolescents and adults
Spirochetes
(Page 356)
“a genus of bacteria having a flexible cell
wall but no flagella in the traditional sense.
Movement occurs by contractions
(undulating) of long filaments (endoflagella)
that run the length of the cell.”
Spirochetes
• human oral cavity
• Among first organisms described by
van Leewenhoek in the 1600’s that he found
in saliva and tooth scrapings.
• 3 common genera: Borrelia
Leptospira
Treponema
Leptospira interrogans
(Page 357)
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leptospirosis
domestic or wild
exceedingly fine spiral
obligate aerobe
animals shed bacteria in their urine
humans infected by contact with urinecontaminated water or soil, or animal tissue
Leptospirosis
Portal of Entry
• minor abrasions
• when ingested: mucosa of upper digestive
system
• incubation period of 1-2 weeks
• acute symptoms subside
• second episode of fever: Weil’s Disease
• kidney failure is the most common COD
Borrelia burgdorferi
• tick-borne disease: seasonal occurrence
lack of contagiousness
unusual skin rash
• bacterial pathogen: penicillin
• 1983: spirochete identified as the cause
• Lyme Disease most prevalent on Atlantic coast
Tick Feeding Cycle
• first and second feedings: larva and nymph
• third feeding: adult
Deer Tick
Erythema Migrans
• 75% of all cases
• 15 cm and resembles “bull’s eye”
Second Phase
(Page 358)
• heart: pacemaker
• chronic neurological symptoms: facial
paralysis, meningitis, encephalitis
• arthritic symptoms
• diagnosis: symptoms, geographic area
• no laboratory test for Lyme’s disease
• several antibiotics are effective
Removing a Tick
Treponema pallidum
(Page 358)
• gram-negative spirochete, thin and tightly
coiled
• Stains poorly
• Greek: “twisted thread” “pale”
Primary Stage of Syphilis
• Readings question #3: What is the most
notable sign for the primary stage of syphilis?
Secondary Stage of Syphilis
(Page 360)
• Readings question #4: List 3 signs and
symptoms that an individual may experience
during the secondary stage of syphilis.
Secondary Stage of Spyhilis
mucous patches
anal warts
Tertiary Stage of Syphilis
Readings question #5: During the tertiary
stage of syphilis, what distinguishing sign
occurs?
• lesions may ulcerate and cause extensive
tissue damage
Congenital Syphilis
• transmitted across the placenta
• damage to mental development and other
neurological symptoms
• pregnancy during the primary or secondary
stage is likely to produce a still birth
Treatment for Syphlis
• benzathine penicillin: effective in the body for
2 weeks
• doxycycline for penicillin-sensitive people
• Antibiotic therapy must be administered for a
longer period of time due to the slow-growing
spirochete.