Mycobacterium

aerobic, non-endospore-forming rodsmyco = “fungus-like”

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

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?

What are its portals of entry?

MAC

• common bacteria• weakened immune system: “opportunistic”• blood infections, hepatitis, pneumonia• combination of antibiotics:– azithromycin (Zithromax)– clarithromycin (Biaxin)– 3 other drugs

Mycobacterium tuberculosis

• 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. tuberculosisattacking macrophages. When does the tubercleform? What happens when the macrophages die?Describe the process of liquefaction and its endresult. What is cavitation?

Ghon Complexes

dormant disease: lesions calcify

Miliary Tuberculosis

• cardiovascular and lymphatic systems

• defenses overwhelmed

• weight loss, coughing (blood), general malaise

Treatment

• 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

• 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

“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

• leptospirosis• domestic or wild• exceedingly fine spiral• obligate aerobe• animals shed bacteria in their urine• humans infected by contact with urine-

contaminated 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

• 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

• 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

• 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