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  • Bacteriology Bacteriology Bacteriology

    ByBy Dr. Carmen RexachDr. Carmen Rexach

    Mt San Antonio CollegeMt San Antonio College MicrobiologyMicrobiology

  • Bergey’s manual 4 divisions based on cell wall structure: divided into sections

    • Spirochetes • Aerobic-microaerophilic • Gram neg rods & cocci • Facultative anaerobic

    gram negative rods • Anaerobic gram negative

    helical rods • Dissimilatory sulfide

    reducing • Anaerobic gram neg cocci • Rickettsias and Chlamydias • Mycoplasmas • Gram positive cocci

    • Endospore forming gram positive rods & cocci

    • Regular nonsporing gram positive rods

    • Irregular nonsporing gram positive rods

    • Mycobacteria • Nocardioforms • Gliding, sheathed, budding

    bacteria • Chemoautotrophic bacteria • Archaeobacteria • Phototrophic bacteria • actinomycetes

  • Spirochetes

    Borrelia burgdorferi

    Treponema pallidum Borrelia recurrentis

    Leptospira interrogans

  • General characteristics • Habitat

    – soil, contaminated water, animal parasites • Motility

    – Axial filament generates quick corkscrew like motion

    • Shape – Can be tightly coiled or curved like R. rubrum

    • Examples – Treponema pallidum – Borrelia recurrentis – Borrelia burgdorferi – Leptospira interrogans

  • Treponema pallidum: causative agent of syphilis

    • 5-20μm long, 0.2μm wide • Cannot be cultured in medium

    – Humans only natural host – Rabbit testes used for diagnostic or

    experimental work • Very fragile

    – Not viable for long outside of the body – Easily killed by disinfectants – Very susceptible to antibiotics, including


  • Pathogenesis and clinical dz

    • STD • Second only to gonorrhea in frequency of

    reporting • Very dangerous because of four stages

    – 1o, 2o, latent, 3o

    • Congenital transmission • Clinical symptoms largely due to immune

    response • Transmission is primarily sexual

  • Primary syphilis • Lesion at site of entry forms between 10-70

    days post infection = chancre • Relatively painless • Especially problematic for females • Disappears spontaneously within 3-6 weeks

    giving illusion of a cure

  • Primary syphilis

  • Secondary syphilis • 2wks to 6 months later • Systematic spread of spirochetes • Generalized rash and lesions (highly infective) • Fever, headaches, sore throat • Symptoms gradually subside over many years

    with three possible outcomes – 1) Complete remission (30-40% untreated) – 2) recurrence 2o lesions at 3-12 month

    intervals – 3) progression into latent and then 3o

    • Latent = high serum titers • No clinical symptoms • 50% of these individuals develop no further


  • papulosquamous rash

    Secondary syphilis

  • Tertiary syphilis • Occurs 3 to 30 years after secondary • Develops rapidly in immunocompromised

    individuals • Gummas = lesions develop due to hypersensitivity

    to spirochetes in many body tissues • CNS lesions = neurosyphilis

    – Mental changes, major cause of insanity • Aortic aneurysms • Number of tertiary syphilis cases has doubled

    since 1986

  • Tertiary syphilis

  • Late syphilis: ulcerating gumma

  • Borrelia recurrentis relapsing fever

    • Tick borne disease • Can be cultured in vitro • Also called epidemic relapsing fever = campers • Symptoms

    – Sudden fever, headache, muscle pain, sometimes rash, then nausea, vomiting, prostration

    – Patient appears to recover, then relapses to initial symptoms 4-10 times

    • Treat with broad spectrum antibiotics, such as tetracyclines

  • Borrelia burgdorferi Lyme disease

    • First American case 1975, reported in Europe in 1900’s

    • Reported from most states • Vector = Ixodes • Seasonal occurrence due to increased

    outdoor activity • Can be cultured in vitro

  • Lyme disease • Two distinct clinical stages

    – Early • Flu-like symptoms • Swollen lymph nodes, fever, headache, stiff neck,

    arthralgias, myalgias, fatigue • Erythema migrans

    – Site of inoculation 2-4 wks post – Late

    • One month to several years post early symptoms • Neurologic, cardiac, arthritic symptoms • 6% develop chronic arthritis

  • Lyme disease

    Erythema migrans Ixodes scapularis

  • Leptospira interrogans Leptospirosis, “rat fever”

    • Water contaminated with urine from infected animals

    • Common in vets, abattoir workers, farmers, dog owners

    • Increased prevalence summer months • Entry: breaks in skin and mucosa • Spread through blood leading to kidney infection,

    flu-like symptoms • 4days post-infection

  • Leptospirosis

    Weil’s syndrome: severe leptospirosis

  • Leptospira: favelas in Brazil

  • Aerobic/microaerophilic, motile, helical/vibrioid gram negative bacteria

    • Not included in spirochetes because no axial filament

    • Contain single flagellum at one or both poles, sometimes tufts, rigid

    • Habitat – Most aquatic (Spirillum volutans) – Soil

    • Nitrogen fixing bacteria such as Asospirillum associated with tropical grasses, corn, sugar cane

    Helical bacteria

  • Helical pathogens • Campylobacter: microaerophilic normal inhabitants

    of intestinal flora of domestic animals and poultry – Campylobacter fetus

    • Abortion in domestic animals • Acute gastritis in immunocompromised

    – Campylobacter jejuni • Acquired from food, milk, contact with infected

    animals • Symptoms: bloody diarrhea, fever, headache,

    abdominal pain, self limiting (6-10 days) – Helicobacter pylori

    • Culture on chocolate agar under microaerophilic conditions

    • Gastritis, stomach and duodenal ulcers • Chronic infections associated with stomach cancer

  • Vibrioids • Bdellovibrio

    – Preys on gram negative bacteria

    – Reproduces in periplasmic space by fragmentation

    • Vampirovibrio – Parasitic bacterium

    Bdellovibrio attacking S. serpens

  • Pseudomonads • Common soil inhabitants • Can also be pathogenic • Large variety of enzymes

    – Important decomposers of unusual substances including pesticides

    – Some can grow in antiseptics – Some show tendency toward plasmid mediated

    antibiotic resistance – Aerobic, but may also use N as final electron

    acceptor – Can cause N depletion of the soil

    Gram negative aerobic rods and Gram negative aerobic rods and coccicocci

  • Medically important pseudomonads

    • Pseudomonas pseudomallei – Extremely virulent, endemic in Southeast Asia

    • Pseudomonas aeruginosa * • Legionella * • Neisseria gonorrhoeae • Moraxella • Francisella tularensis * • Bordetella pertussis * • Brucella *

  • Pseudomonas aeruginosa • Obligate aerobe can be

    cultured in vitro • Produce blue green water

    soluble pigment called pycocyanin that diffuses into culture medium

    • Produces exotoxin which prevents protein synthesis in infected host cells

    • Ubiquitous in the environment, found on plants

  • Pseudomonas aeruginosa • First observed on

    bandages covering infected wounds = sweet grape-like odor

    • Nosocomial infections, especially in patients with CF, burns, urinary catheters, cancer chemo

    • 60-70% mortality, very resistant to therapy

    • Pseudomonas skin infections in people using contaminated hot tub

    P. aeruginosa in a biofilm from catheter

  • Pseudomonas aeruginosa • Mariana Bridi da Costa, 20 yo

    Brazilian model and participant in Miss World

    • Septicemia due to Ps aeruginosa UT infection

    • Misdiagnosed as kidney stones on late Dec, 2008

    • Admitted to hospital on Jan 3, 2009 in septic shock – Septicemia decreases O2 supply

    to extremities = necrosis of tissue

    – BT = O neg, difficulty in finding donors

    • Both arms and both legs amputated, stomach removed, both kidneys removed

    • Died Feb 24, 2009 at 3:30am

  • Legionella pneumophila: Legionnaire’s disease

    • Pleomorphic, cultured in guinea pigs, embryonated eggs, nutrient media

    • Natural habitat: water and soil, intracellular parasite of protozoa

    • Initial occurrence – Summer 1976 American

    Legion convention in Philadelphia with 5000 attendees

    – 2 week incubation period – 221 cases, 170

    hospitalized, 41 deaths

  • Legionnaire’s disease • Two forms of disease

    – 1) mild flu-like with year round occurrence called Pontiac Fever

    – 2) Legionnaire’s—more severe, most common in immunocompromised individuals (age, respiratory illness)

    • Symptoms – Signs of lobar pneumonia 2-10 days post-

    exposure – Diarrhea, weakness, headache, muscle aches,

    malaise, anorexia, dry cough, increase tempera