Miscellaneous Bacterial Agents of Disease

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Miscellaneous Bacterial Agents of Disease
Chapter 21
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spirochetes

• Gram negative human pathogens
• Treponema
• Leptospira
• Borrella

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Treponema

• thin, coiled cells
• live in the oral cavity, intestinal tract,
  perigenital regions of humans animals
• Pathogenic species are strict parasites

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Treponema pallidum

• human is the natural host
• extremely fastidious sensitive, cannot survive
  long outside of the host
• causes syphilis
• Primary syphilis
• Secondary syphilis
• Tertiary syphilis
• Congenital syphilis nasal discharge, skin
  eruptions, bone deformation, nervous system
  abnormalities
• treatment penicillin G

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Chancre
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Darkfield Microscopy
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Leptospira

• tight, regular individual coils with a bend or
  hook at one or both ends
• L. biflexa harmless, free-living saprobe
• L. interrogans causes leptospirosis, a zoonosis
• bacteria shed in urine infection occurs by
  contact targets kidneys, liver, brain, eyes
• sudden high fever, chills, headache, muscle
  aches, conjunctivitis, vomiting
• 50-60 cases a year in US

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Borrella

• large, 3-10 coils
• Borrelioses transmitted by arthropod vector
• B. hermsii - relapsing fever
• B. burgdorferi - Lyme disease

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B. hermsii - relapsing fever

• mammalian reservoirs squirrels, chipmunks, wild
  rodents
• tick-borne
• after 2-15-day incubation, patients have high
  fever, shaking, chills, headache, fatigue
• nausea vomiting, muscle aches, abdominal pain
  extensive damage to liver, spleen, heart,
  kidneys, cranial nerves
• parasite changes immune system tries to control
  it- recurrent relapses
• tetracycline

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B. burgdorferi - Lyme disease

• transmitted by ticks
• complex 2-year cycle involving mice deer
• nonfatal, slowly progressive syndrome that mimics
  neuromuscular rheumatoid conditions
• 70 get bulls eye rash
• fever, headache, stiff neck, dizziness
• if untreated can progress to cardiac
  neurological symptoms, polyarthritis
• tetracycline, amoxicillin
• vaccine for dogs, human vaccine discontinued
• Prevention-insect repellant containing DEET

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Life Cycle of Ixodes
Figure 21.18
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Lyme disease
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Vibrio cholera

• comma-shaped
• One of top 7 causes of morbidity mortality
• ingested with food or water
• infects surface of small intestine, noninvasive
• cholera toxin causes electrolyte water loss
  through secretory diarrhea (rice-water stool),
  resulting dehydration leads to muscle,
  circulatory, neurological symptoms
• treatment oral rehydration, tetracycline
• vaccine

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Vibrio cholera
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Action of Cholera Toxin
Figure 21.25
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other Vibrio

• salt-tolerant inhabitants of coastal waters,
  associate with marine invertebrates
• Vibrio parahaemolyticus gastroenteritis from raw
  seafood
• Vibrio vulnificus - gastroenteritis from raw
  oysters

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Campylobacter jejuni

• important cause of bacterial gastroenteritis
• transmitted by beverages food (poultry most
  common)
• reach mucosa at the last segment of small
  intestine near colon adhere, burrow through
  mucus and multiply
• symptoms of headache, fever, abdominal pain,
  bloody or watery diarrhea that is self-limiting
• heat-labile enterotoxin

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Campylobacter jejuni
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Helicobacter pylori

• Curved cells discovered in 1979 in stomach
  biopsied specimens
• Slightly helical, highly motile bacterium that
  colonizes the stomach of its hosts
• Causes gastritis and most (if not all) peptic
  ulcers
• H. pylori produces numerous virulence factors
  that enable it to colonize the stomach

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H. pylori and Peptic Ulcers
Figure 21.27.1
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H. pylori and Peptic Ulcers
Figure 21.27.2
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H. pylori and Peptic Ulcers
Figure 21.27.3
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Diagnosis, Treatment, and Prevention

• Diagnosis
• Presence of H. pylori can be demonstrated by a
  positive urease test
• Biochemical tests provide a definitive
  identification
• Treatment
• Antimicrobial drugs are used in combination with
  drugs that inhibit acid production
• Prevention
• Prevention involves good hygiene, adequate sewage
  treatment, water purification, and proper food
  handling

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Rickettsia

• obligate intracellular parasites
• gram-negative cell wall
• among the smallest bacteria
• nonmotile pleomorphic rods or coccobacilli
• ticks, fleas louse are involved in their life
  cycle
• bacteria enter endothelial cells cause necrosis
  of the vascular lining vasculitis, vascular
  leakage thrombosis
• treat with tetracycline chloramphenicol

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4 types of rickettsioses

• epidemic typhus R. prowazekii carried by lice
  starts with a high fever, chills, headache, rash
  May have a chronic, recurrent form
• endemic typhus R. typhi, harbored by mice
  rats occurs sporadically in areas of high flea
  infestation milder symptoms
• Rocky Mountain spotted fever R. rickettsii
  zoonosis carried by dog wood ticks most cases
  on eastern seaboard distinct spotted rash may
  damage heart CNS
• Ehrlichia genus contains 2 species of
  rickettsias tickborne bacteria cause human
  monocytic granulocytic ehrlichiosis

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Rocky Mountain Spotted Fever
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Rocky Mountain Spotted Fever Rickettsia
rickettsii
Distribution of cases over a 4-year period
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Coxiella burnetti

• causes Q fever
• intracellular parasite
• produces an unusual resistant spore
• harbored by a wide assortment of vertebrates
  arthropods
• transmitted by air, dust, unpasteurized milk,
  ticks
• usually inhaled causing pneumonitis, fever,
  hepatitis
• tetracycline treatment
• vaccine available

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Coxiella burnetti
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Bartonella

• small gram-negative, fastidious, cultured on
  blood agar
• Bartonella-caused diseases
• trench fever, spread by lice
• cat-scratch disease, a lymphatic infection
  associated with a clawing injury by cats.
• Organism carried by 40 of cats
• Most infections localized and resolve a a couple
  weeks
• bacillary angiomatosus in AIDS patients
• tetracycline, erythromycin rifampin

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Cat-scratch disease
Bartonella henselae
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Chlamydia

• obligate intracellular parasites
• small gram-negative cell wall
• C. pneumoniae causes an atypical pneumonia that
  is serious in asthma patients
• C. psittaci causes ornithosis, a zoonosis
  transmitted to humans from bird vectors highly
  communicable among all birds pneumonia or
  flulike infection with fever, lung congestion

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Chlamydia trachomatis

• human reservoir
• 2 strains
• trachoma strain attacks the mucous membranes of
  the eyes, genitourinary tract lungs
• ocular trachoma uncommon in U.S. but common in
  Africa and Asia. Severe infection, deforms eyelid
  cornea, may cause blindness
• inclusion conjunctivitis occurs as babies pass
  through birth canal prevented by prophylaxis
• STD urethritis, cervicitis, salpingitis
  (PID),infertility, scarring
• lymphogranuloma venereum strain disfiguring
  disease of the external genitalia pelvic
  lymphatics

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Chlamydia trachomatis
Lymphogranuloma venereum lesion
Trachoma
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Mycoplasma

• naturally lack cell walls, highly pleomorphic
• treated with tetracycline, erthyromycin
• M. pneumoniae primary atypical pneumonia
  pathogen slowly spreads over interior respiratory
  surfaces, causing fever, chest pain sore
  throat.
• M. hominis Ureplasma urealyticum weak
  sexually transmitted pathogens

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Bacteria in dental disease

• oral cavity is a complex, dynamic ecosystem,
  containing 400 species
• dental caries slow progressive infection of
  irregular areas of enamel surface
• begins with colonization by slime-forming species
  of Streptococcus cross adherence with
  Actinomyces
• process forms layer of thick, adherent material
  (plaque) that harbors masses of bacteria which
  produce acid that dissolves enamel
• If plaque is allowed to stay, secondary invaders
  appear Lactobacillus, Bacteroides,
  Fusobacterium, Porphyromonas, Treponema.
• Acid dissolves tooth enamel

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Thin mucous coating of salivary proteins
Streptococcus mutans
Secondary invaders
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Peridontal disease

• soft tissue disease
• when plaque becomes calcified into calculus above
  and below the gingiva
• this irritates tender gingiva causing
  inflammation gingivitis
• pockets between tooth gingiva are invaded by
  bacteria (spirochetes gram-negative bacilli)
• tooth socket may be involved (peridontitis)
• tooth may be lost