Chapter 13: Other GramNegative Rods

1
Chapter 13 Other Gram-Negative Rods

• 2 significant features of structure physiology
  common to this group
• Gram-negative cell wall
• Contains LPS gt Virulence Factor!
• Growth in presence of O2 cause infections _at_
  sites where O2 tension is high
• Ex. lungs
• Pathogens of human Respiratory Tract
• Haemophilus
• Bordetella
• Legionella
• Opportunistic pathogen
• Pseudomonas
• Yersinia pestis causes bubonic plaque

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Haemophilus

• Family Pasteurellaceae
• Genus Haemophilus
• Species H. influenzae major disease-producing
  species of the genus only human pathogen!
  Misnamed Bacteria H.
  ducreyi an STD H. aegypticus
  causes pink eye
• Epidemiology
• H. influenzae normal component of Upper RT can
  colonize conjunctiva and genital tract
• Humans are the only natural hosts!
• Colonization begins shortly after birth

3
Haemophilus

• General Genus Characteristics
• Small Gram-negative pleomorphic bacilli
  (coccobacilli) pleomorphic in shape, ranging
  from short, flat rods to long, slender filaments
• Facultative anaerobe
• Non-motile
• Non-spore former
• May be encapsulated or unencapsulated
• Fastidious w/ regard to growth requirements

4
Haemophilus

• Growth Conditions
• Media Chocolate Agar or enriched media
  supplemented w/ _at_ nutritional (growth) factors
• X Factor Hemin (necessary component of
  cytochromes, catalase and peroxidase)
• V Factor Nicotinamide Adenine Dinucleotide (NAD)
  coenzyme of certain dehydrogenases
• Temperature - 37C Mesophile
• Gas elevated CO2 (5-10) enhances growth

5
Haemophilus

• Growth conditions
• Normal flora of Upper RT or vagina
• Reservoir human pathogen ONLY all serious H.
  influenzea infections are type b
• Type b polyribose-ribotol phosphate gt specific
  polysaccharide making up the capsule capsular
  component. Hib infections.
• H. influenzae is a secondary invader to the
  influenza virus!
• Virulence factors
• Capsule retards phagocytosis 6 subtypes (a-f)
• Type antigenic capsular polysaccharide
• IgA protease degrades host IgA
• Note the bacterium does NOT survive well outside
  the human body.

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Haemophilus

• Mode of Infection
• Inhalation respiratory droplets
• Attachment to respiratory epithelium
• Colonization of nasopharynx ? damage epithelial
  surfaces
• IgA protease degrades secretory IgA, facilitating
  colonization of RT mucosa
• Invade bloodstream ? bacteria multiply
  (bacteremia) ? cross BBB ? infection of meninges
  (most severe case)

7
Haemophilus

• Clinical
• Hib Disease (Opportunistic Disease)
• Initial clinical presentation nasopharyngitis
  (nose throat infection) that accompanies or
  follows a respiratory viral infection.
• Contiguous Spread of the infection to sinuses
  (sinusitis), and middle ear (otitis media),
  development of pneumonia (bronchopneumonia)
  severe cases - meningitis
• Systemic Infections- Disseminated spread via
  bloodstream
• epiglottitis, bronchitis, septic arthritis,
  meningitis

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Haemophilus

• Clinical
• Heamophilus meninigitis (b serotype)
• M/c cause of bacterial meningitis in US
• Similar to meningococcal meningitis
• Infection route
• Bacteria ? respiratory tract ? blood ? meninges
• Symptoms
• Fever, vomiting, stiff neck and neurological
  impairment
• Primary Risk group
• Children (6 months 3 yrs) NO Abs present
• Note lt 6 months protection for maternal
  immunity, which decreases there is a window of
  opportunity after 6 months no baby Abs made as
  maternal Ab titers decrease after 3 yoa, baby
  makes own Abs.
• Increased incidence in daycare centers

9
Haemophilus

• Clinical
• Heamophilus meninigitis (b serotype)
• Immunity
• Newborns have passive immunity from mother at
  birth for 6 months
• Maternal Abs decrease ? high risk group of
  children (6 months to 3 years)
• gt 3 yoa naturally acquired immunity after an
  infection
• Contrast newborn do NOT have any passive
  maternal immunity to B. pertussis therefore,
  must be immunized ASAP w/ DPT)
• Residual impairments
• w/ prompt tx mortality rate lt 10
• 33 of survivors suffer neurological disorders
  mental retardation, hearing loss, blindness
  convulsions
• Untreated fatality rate 90-100

10
Haemophilus

• Clinical
• Nonencapsualted H. influeanzae Infections
• Normal flora 75 of RT Haemophilus spp. are NOT
  encapsulated.
• Rarely cause systemic disease.
• Mucous membrane Infections
• Otitis media, sinusitis, bronchitis, pneumonia,
  conjunctivitis (pink eye)
• Adult Infections
• Hib infections are RARE adulthood already
  exposed at early age have acquired immunity
• Compromised adults respiratory problems,
  diabetes or alcoholism
• Clinical Infection Pneumonia

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Haemophilus

• Clinical
• Haemophilus ducreyi
• Disease Venereal Disease (STD)
• Symptom Chancroid (genital ulcers) mostly seen
  in men
• Infection is characterized by development of
  small papule or pustule _at_ point of infection,
  usu. Genitalia pustule ruptures and forms an
  ulcer similar to chancre observed w/ syphilis.
  Ulcer is painful and often accompanied by tender,
  swollen and suppurative regional lymph nodes.
• Transmission direct contact w/ infected lesions
• Risk group uncircumcised men
• Haemophilus aegypticus
• Disease Conjunctivitis (pink eye)
• Symptom Subconjunctival hemorrhage that
  accompanies infection imparts a bright pink tinge
  to sclera
• Transmission contaminated fingers
• Risk group children

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Haemophilus

• Laboratory Identification/Dx (Hib)
• Specimens blood, CSF, synovial fluid, throat or
  nasopharyngeal swabs
• Gram stain
• Pleomorphic, Gram (-) coccobacilli
• Culture
• Requirement for X and V factors use of chocolate
  agar
• Type b capsule may be demonstrated directly in
  CSF by Capsular swelling (Quelling rxn) or by
  immunofluorescent staining.
• Capsular Ag detected in CSF using immunologic
  tests
• Latex agglutination
• Countercurrent immunoelectrophoresis
• Radioimmune assay

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Haemophilus

• Treatment (Hib)
• Combination Antibiotic therapy
• Ampicillin/Chloramphenicol
• Rifampin close contact individuals (siblings or
  day care centers)
• Prevention/Control (Hib)
• Current vaccine is given to children lt 2 yoa
• Consists of Hib polyribose phosphate capsular CHO
  conjugated to protein
• Active immunization

14
Bordetella

• Genus Bordetella (very old geunus, early
  discovery)
• Species Bordetella pertussis
• Bordetella parapertussis
• General Genus Characteristics
• Small, Gram-negative pleomorphic bacilli
  (coccobacilli)
• Obligate aerobe
• Non-motile
• Encapsulated
• Growth Conditions
• Media Bordet-Gengou (potato-blood-glycerol agar)
• Colony smooth, tiny, glistening
• Appearance mercury-drop or pearl
• Normal flora human respiratory tract
• Reservoir human pathogen only

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Bordetella

• Clinical infection Pertussis or whooping
  cough causative agent B. pertussis
• Epidemiology
• Major route of transmission person-to-person
  via respiratory droplets
• Bacterium only survives a short time when
  expelled from body in respiratory secretions
• Incidence varies among different age-groups,
  depending on the active immunization of young
  children in a community
• In absence of active immunization program, dis.
  is m/c among young children (1-5 yoa)

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Bordetella

• Virulence Factors
• Filamentous Hemagglutinin (FHA) surface
  protein similar to pili
• Function adherence to URT ciliated epithelium
  specifically recognize and bind to ciliated
  respiratory cells
• Pertussis Toxin (PT) protein exotoxin (action
  is similar to Cholera toxin)
• Function stimulates activity of AC on surface of
  B. pertussis cells
• Location of Adenyl Cyclase surface of B.
  pertussis cells
• Bacterium contacts host cell ? host cell
  calmodulin ? activation of bacterial AC ? ?levels
  of cAMP ? impairs bacteriocidal activity of PMN
  leukocytes and M?s from the host
• Result Impairment of phagocytic activity of
  alveolar M?s
• Tracheal Cytotoxin (TC) induces hosts
  respiratory cells to produce IL-1 IL-1 triggers
  the production of NO ? destroys respiratory cells
• Result respiratory epithelial cell destruction
  w/ corresponding inhibition of ciliary movement

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Bordetella

• Virulence Factors
• Overall action of PT TC
• Destroy and dislodge ciliated epithelial cells ?
  loss of ciliary mechanism ? buildup of mucous
  blockage/obstruction of airways
• Transmission
• direct contact w/ droplets or inhalation of
  infectious aerosols no asymptomatic carriers
• B. pertussis is aerosolized from throat of person
  w/ whooping cough and is transmitted to others by
  air-borne route
• Mode of Attachment
• Bacterium selectively attaches to ciliated
  epithelial cells of URT

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Bordetella

• Three (3) Symptomatic Stages of Pertussis
• Catarrhal Stage or Prodrome Stage sxs similar
  to a cold (mis-diagnosis can occur _at_ this stage)
• Nasal drainage, congestion, sneezing, low-grade
  fever, occasional coughing
• Duration 1-2 weeks
• Paroxysmal Stage recurrent episodes (paroxysms)
  of uncontrollable coughs repetitive coughs
• Each paroxysm consists of 10-20 abrupt rapid
  coughs w/ inability to breathe between coughs
• Need for air stimulates a deep inspiration that
  draws air swiftly thru the narrowed larynx,
  producing the classic whooping
• Continued coughing ? anoxia ?O2 in the blood
  (hypoxia or hypemia) cyanosis is possible, too
• Disease progresses involvement of more
  respiratory tissue w/ blockage of bronchial
  passageways

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Bordetella

• Three (3) Symptomatic Stages of Pertussis
• Convalescent Stage mild to severe coughing,
  low-grade fever
• SLOW recovery gt 6 months
• Secondary complications may occur
• Otitis media, pneumonia
• Encephelopathy, seizures
• Risk Groups
• CHILDREN
• lt I yoa 45 of cases
• lt 10 yoa 80 of cases
• Serious disease of newborns b/c NO maternal
  immunity

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Bordetella

• Diagnosis
• Physician observation of pts clinical
  presentation BEST Dx
• During Paroxysmal phase leukocytosis total WBC
  count gt 50,000 cells/µL (normal 4500-11,000
  WBCs/µL
• Laboratory specimen from nasopharyngeal
  secretions
• Culture Media (Bordet-Gengou) colony
  appearance after 3 days mercury-drop or
  pearl
• Gram Stain
• Serological confirmation rapid specific ID
• Direct fluorescent AB (DFA) test looking for
  Abs to the toxins
• Immunity
• Limited secondary attacks possible, but less
  severe
• Treatment
• Combination antibiotic therapy - ? secondary
  pneumonia infections
• Aspiration of respiratory secretions
• O2 therapy
• Prevention/Control
• DPT vaccine killed whole pertussis vaccine

21
Legionella

• Family Legionellaceae
• Genus Legionella
• Species Legionella pneumophila
• General Genus Characterisitics
• Gram-negative rods stain faintly
• Slender rod in nature coccobacilli in clinical
  material
• Facultatitve aerobes intracellular parasites
• Unencapsulated
• Motile- monotrichous flagella
• Epidemiology
• Normal habitat soil and water, including
  cooling towers and water distribution systems
• 80-90 human disease caused by L. pneumophila
• Infections result from inhalation of aerosolized
  organisms
• Sporadic cases localized outbreaks may occur
• L. pneumophila is Cl tolerant survives H2O
  treatments

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Legionella

• Epidemiology
• Summer 1976 famous outbreak 5000 members of
  the American Legion _at_ convention in Philadelphia
• w/in 2 weeks many complained of chills, fever,
  and muscle aches
• 12 died of pneumonia-like illness w/in 3weeks
• Over ensuing weeks, 170 hospitalized 29 deaths
  occurred
• Investigations proved L. pneumophila to be the
  culprit in the ventilation/cooling sys.

23
Legionella

• Pathogenesis
• Organism gains entry into URT
• Aspiration of contaminated H2O
• Inhalation of contaminated aerosol
• Eventual entry to lung disruption of the
  alveolar M? system bacteria continue to
  multiply w/in the phagosome d/t failure of fusion
  to lysosomes.
• Clinical
• Respiratory tract infection w/ 2 distinct
  presentations
• Legionnaires Disease
• Atypical, acute lobar pneumonia w/ multisystem
  symptoms
• Symptoms develop after incubation period of 2-10
  days
• Early sxs fever, malaise, myalgia, anorexia, HA
• Cough develops watery diarrhea occurs in 25-50
  cases
• Nausea, vomiting, and neurologic sxs may also
  occur.

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Legionella

• Clinical
• Respiratory tract infection w/ 2 distinct
  presentations
• Pontiac Fever
• Mild Influenza-like illness
• Characteristically infects otherwise healthy
  individuals
• Mortality rate lt 1
• Occurs in epidemic outbreaks throughout the year
• Risk factors for Legionnaires disease
• Alcoholism
• Advanced age
• Smoking
• Immunosuppressive therapy
• Renal transplant cancer pts w/ most sporadic
  cases

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Pseudomonas

• Genus Pseudomonas
• Species Pseudomonas aeruginosa
• General Genus Characteristics
• Gram-negative bacilli
• Aerobic
• Non-fermentative (Lac-)
• Primary human pathogen P. aeruginosa
• Motile single polar flagella or polar tuft (1-6
  flagella)
• Encapsulated extracellular polysaccharide slime
  layer
• Cell wall similar to Enterobacteriaceae
• Pili for attachment purposes
• Obligate aerobe

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Pseudomonas

• Epidemiology
• Widely distributed in nature
• Most pseudomonas do not colonize humans, but some
  are important opportunisitc pathogens
• P. aeruginosa m/c human isolate
• Most frequently recovered pseudomonas from human
• Distinguishing characteristics odor
  pigmentation
• Significant opportunistic pathogen major cause
  of nosocomial infection
• Growth in laboratory water baths, hot tubs, wet
  IV tubing, other water-containing vessels
• Causes nosocomial pneumonia, UTIs, surgical site
  infection, infections of severe burns, infections
  of pts undergoing chemotx for neoplastic dis or
  antibiotic tx

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Pseudomonas

• Biochemical/Cultural Characteristics (P.
  aeruginosa)
• Grows well on variety of media
• Optimal growth _at_ 35ºC (can grow _at_ 42ºC)
• Only Gram-negative rod that produces pyocyanin
• Blue-green, H2O-soluble pigments - diffusible
• Characteristic grape-like (sweet) odor It
  smells!! dirty sneaker smell
• Oxidase ()
• Obtain E thru oxidative metabolism can grow
  anaerobically, too
• Non-lactose fermenter
• Use CHOs oxidatively w/out producing
  alcohols/acids as end products

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Pseudomonas

• Pathogensis
• Attachent to colonization of host tissue
• Pili mediate adherence
• Glycocalyx capsule ? effectiveness of normal host
  clearance mechanisms
• Does not typically invade healthy anatomical
  barriers
• Infections d/t iatrogenic/invasive procedures
  penetration into body scope, surgical blade,
  etc.
• Produces exotoxins
• Exotoxin A virulence factor same mechanism of
  action as Diphtheria toxin is able to prevent
  protein syn by infected host cells
• Produces enterotoxin (diarrheal disease)
• Produces hemolysins and variety of degradation
  enzymes

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Pseudomonas

• Clinical (P. aeruginosa)
• Localized Infections
• Eye (keratitis endophthalmitis, following
  trauma)
• Ear (external otitis swimmers ear invasive
  necrotizing otitis externa, esp. in diabetic pts
  or trauma pts)
• Skin wound sepsis, pustular rashes (contaminated
  whirlpools, hot tubs, swimming pools)
• Urinary Tract esp. hx pts subjected to
  catheterization, instrumentation, surgery, renal
  transplantation
• Respiratory Tract pneumonia in pts w/ chronic
  lung diseases, CHF, CF particularly in pts who
  have been incubated or on a ventilator
• GIT mild diarrhea ? severe, necrotizing
  enterocolitis
• CNS meningitis brain abscesses, particularly
  in association w/ trauma, surgery, tumors of head
  or neck
• Potential to lead to disseminated infection

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Pseudomonas

• Clinical (P. aeruginosa)
• Systemic Infections
• Bacteremia m/c in immunocompromised individuals
• Secondary pneumonia
• Bone joint infections
• IV drug users and pts w/ UT or pelvic infections
• Endocarditis
• IV drug users, prosthetic heart valves
• CNS when meninges affected
• Skin/soft tissue infections

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Pseudomonas

• Summary of Clinical Manifestations
• Typical opportunist
• Common nosocomial infections burn pts receiving
  hydro-tx, neoplastic disease, CF (thickening of
  sputum d/t pseudomonas)
• Found in 10 of stools
• Infects almost any tissue or body site
• Localized lesions site of burns, wounds,
  corneal/eye tissue (colonization w/ contact lens
  use serious consequences), UT, RT
• P. aeruginosa responsible for 10 of nosocomial
  infections, 11 of bacteremia cases, 30 of burn
  infections
• 80 mortality w/ bacteremia can die from the
  infection
• m/c host defense phagocytosis

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Pseudomonas

• Laboratory Identification/Dx
• Isolation Identification
• Noselective media blood agar
• Moderately selective media MacConkey agar
• Various biochemical tests
• Oxidase activity
• Pyocyanin production green or green-blue
  pigments
• Fruity odor characteristic

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Pseudomonas

• Treatment/Prevention
• Pseudomonas spp are among the most resistant
  vegetative bacterial cells to chemical
  disinfectants
• Infections are very resistant to therapy diverse
  plasmids have resulted in development of high
  level of resistance to broad range of
  antimicrobials
• Transmission enhanced by improper isolation
  procedures, lack of hand washing, poor
  disinfection so, proper aseptic techniques when
  dealing w/ burns open wounds is essential
• Most strains are susceptible to aminoglycoside
  antibiotics
• Combination antibiotic therapy usually
  effective

34
Yersinia pestis

• Genus Yersinia member of family
  Enterobacteriaceae
• Yersinia pestis causative agent for Bubonic
  Plague
• Epidemiology
• Zoonosis w/ worldwide distribution
• SW US 1 focus
• Rats common reservoir in urban areas (urban
  plague)
• In US, plaque found mostly in the wild prairie
  dogs ground squirrels common reservoirs
  (sylvatic plaque)

35
Yersinia pestis

• Epidemiology
• Transmission via fleas
• Fleas serve to maintain infection w/in animal
  reservoir
• Humans accidental dead-end hosts
• Transmission also by ingestion of contaminated
  animal tissue of via respiratory route (pneumonic
  plague)
• Latter case when organisms reach lungs est.
  2 pneumonia, of after exposure to respiratory
  secretions from pt. or animal w/ plague pneumonia.

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Yersinia pestis

• Pathogenesis
• From site of innoculation (i.e., bite of infected
  flea or lungs inhalation of infected human
  respiratory secretions) organisms carried by
  Lymphatic System to regional Lymph Nodes
• Ingestion by Phagocytes
• ORGANISMS ARE RESISTANT TO INTRACELLULAR KILLING
  MULTIPLY, INSTEAD.
• RLEASED BACTERIA MORE RESISTANT TO FURTHER
  PHAGOCYTOSIS
• Lymph Nodes display hemorrhagic necrosis w/ high
  PMN and EC bacteria
• Hematogenous spread to other organs/tissues may
  occur

37
Yersinia pestis

• CLINICAL SIGNIFICANCE
• m/c form Bubonic/Septicemic Plague
• Flea ingests blood from infected animal
• Y. pestis produces coagulase that causes blood to
  clot in fleas foregut, enhancing bacterial
  multiplication.
• Next flea feeding regurgitation of bacteria
  into new animals skin (i,e., human)
• Incubation period 2-8 days before onset of sxs
• Non-specific sxs high fever, chills, HA,
  myalgia and weakness proceeds to prostration
  (sudden)
• Then painful BUBO develops pronounced swelling
  of 1 or more infected lymph nodes w/ surrounding
  edema
• Groin (m/c), axillae, neck

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Yersinia pestis

• CLINICAL SIGNIFICANCE
• m/c form Bubonic/Septicemic Plague
• ?BP w/ disease progression ??? septic shock
  death (if not txed)
• Mortality rate of untxed Bubonic Plague gt50
• Other manifestations pustules/vesicles w/ WBCs
  and bacteria purpura necrosis of extremities
  w/ systemic disease
• Septicemic Plague variant pt. is overwhelmed
  by massive bacteremia BEFORE buboes develop

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Yersinia pestis

• CLINICAL SIGNIFICANCE
• Pneumonic Plague
• Plague bacilli in lungs ? purulent pneumonia
• Untxed rapidly fatal
• Highly contagious condition results directly
  when organism inhaled
• Plague Meningitis
• From hematogenous dissemination of organisms to
  meninges d/t inadequate tx or septicemic plague
• Plague bacilli found in CSF

40
Yersinia pestis

• Laboratory Identification/Dx
• Clinical presentation
• Lab ID gram stain culture of aspirate from
  bubo/CSF/Sputum cases of meningitis or
  pneumonic plague cases
• Grpwth on Maconkey Agar or Blood Agar
• Treatment/Prevention
• Streptomycin drug of choice
• For plague meningitis chloramphenical
• Supportive Tx for those pts. w/ signs of shock
• Minimize exposure to rodents fleas NEVER TOUCH
  SICK OR DEAD RODENTS W/ BARE HANDS

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Chapter 14 Clostridia

• Genus Clostriduim
• Species Clostridium perfringens
  Clostridium difficile
  Clostridium tetani
  Clostridium botulinum
• Miscroscopic Morphological Appearance
• Large, Gram-positive bacilli
• Endospore (spore) former
• Most are obligate anaerobes
• Obtain E exclusively by fermentation cannot use
  O2
• Damage from presence of 02
• Most are motile
• Epidemiology
• part of intestinal flora in human other animals
• Found in soil, sewage and aquatic settings (w/
  high organic content)
• Non-invasive, but produce destructive and
  invasion infections when introduced to
  traumatized tiss OPPORTUNISTIC infections

42
Clostridia

• Pathogenic Clostridia
• Histotoxic (tissue destructive) Clostridia Gas
  Gangrene
• Causative agent C. perfringens type A
• Opportunistic pathogens that require a special
  environment to initiate growth anaerobic
  conditions
• Traumatic tissue of lacerated/crushed wounds of
  muscle sustaining severe vascular damage ?results
  in impaired blood supply to area w/ corresponding
  ? in O2 tension ? anaerobic environment
  necrotic tissue stimulus for spore formation
• Traumatized tissue
• Vascular damage - ? blood perfusion
• Necrotic tissue
• ? O2

43
Clostridia

• Pathogenic Clostridia
• Histotoxic (tissue destructive) Clostridia (Gas
  Gangrene)
• C. perfringens produces large of exotoxins
  extracellular enzymes
• Collegenase breaks down CT in skin Muscle
• Proteinase degrages necrotic tiss proteins
• Deoxyribonuclease depolymerizes DNA
• atoxin (phospholipase C) ß-lecithinase
  hydrolyses lecithin in cell membranes ? osmotic
  imbalance ? edema
• ?-toxin (hemolysin) lyses host RBCs

44
Clostridia

• Pathogenic Clostridia
• Histotoxic (tissue destructive) Clostridia (Gas
  Gangrene)
• Clostridial wound infections
• Anaerobic myonecrosis (Gas Gangrene)
• Ever widening expansion of necrotic lesion to
  adjacent healthy muscle tissue.
• Spore introduction into host via traumatic
  incident/injuries necrotic tissue d/t ? blood
  supply (anaerobic)
• Symptoms
• Local edema d/t a- toxin
• Gas production H2 CO2 gt d/t fermentation of
  necrotic tiss
• ? of skin color to BLACK d/t lack of O2 supply
• Generalized fever
• pain in infected tissue

45
Clostridia

• Pathogenic Clostridia
• Histotoxic (tissue destructive) Clostridia Gas
  Gangrene
• Clostridial wound infections
• Anaerobic myonecrosis (Gas Gangrene)
• Risk Group Factors
• Traumatic injuries car, motorcycle
• Surgical procedures in close proximity to
  intestinal microflora bowel surgery, abortions
• Elderly poor circulation aeration to body
• Convalescence/Immunity
• NO host defense d/t the vascular damage
• Bacteria are localized in necrotic tissue
  phagocytic cells are useless
• Repeated infections do NOT cause immunity
• Treatment
• removal of dead tissue (debridement)
• Application of antiserum polyvalent antitoxin
  to neutralize toxins
• Broad spectrum antibiotic
• Hyperbaric O2 chamber ?O2 ? aerate the area ? ?
  of bacteria ? ? production of toxins
• Anaerobic Cellulitis - Localized infection of
  necrotic muscle ONLY
• Symptoms similar to above, but of a lesser
  severity

46
Clostridia

• Pathogenic Clostridia
• A. Enterotoxigenic Clostridia (food poisoning)
• Causative agent C. perfringenes type A
• Mode of infection
• Ingestion of viable vegetative cells
  undercooked meat products
• Synthesis of enterotoxin in SI
• Enterotoxin produced breaks down intestinal
  mucosa ? leakage of plasma membrane ? disruption
  of osmotic equilibrium (secretion of fluid
  electrolytes) ? watery diarrhea
• Symptoms (w/in 8-24 hrs)
• Watery diarrhea, abdominal cramps self-limiting
• Convalescence/Immunity
• NO immunity repeat attacks are possible
• Control/Prevention
• Cook food thoroughly destroys spores (121ºC)
• Food refrigeration after preparation prevents
  enterotoxin production
• Reheating food destroys toxin (80ºC)

47
Clostridia

• Pathogenic Clostridia
• B. Enterotoxigenic Clostridia (antibiotic-associat
  ed colitis or pseudomembranous colitis)
• Causative agent C. difficile drug-resistant
  normal flora of intestine
• Antibiotic therapy disrupts normal flora of
  intestine, allowing a superinfection or secondary
  infection w/ C. difficile
• Mode of infection
• Antibiotic therapy
• Colonization of intestine by C. difficile normal
  flora
• Toxins produced injure intestinal lining by
  inhibiting protein syn produced hemorrhagic
  necrosis
• Leukocyte infiltration into colon d/t toxin
  production
• Pseudomembrane gray-white patch on colon
  mixture of fibrin, mucus, leukocytes necrotic
  epithelial cells
• Symptoms abdominal pain, watery diarrhea, nausea
• Risk Group pts receiving antibiotic tx
  hospitalized pts
• Treatment discontinue antibiotics, maintain
  fluid/electrolyte balance administer Vancomycin
  kills C. difficile

48
Clostridia

• Pathogenic Clostridia
• Tetanus
• Causative agent C. tetani
• Normal inhabitants of soil
• Infection from puncture wound produced by nails
  and splinters
• Generalized Tetanus
• Initial involvement of neck jaw muscles w/
  progression to large muscle groups
• Neonatal Tetanus
• Initial infection of umbilical stump
• Progression to generalized tetanus
• Rare, except in 3rd world countries, where dung,
  ashes or mud maybe applied to umbilical stump to
  stop bleeding

49
Clostridia

• Pathogenic Clostridia
• Tetanus
• Conditions for infection favor spore
  germination
• Small puncture wounds
• Necrotic tissues _at_ wound site
• ? O2
• Variety of toxins produced
• Neurotoxin Tetanospasmin or Spasmogenic Toxin
• Accounts for the classic symptoms primary toxin
• Site of Action neurons in spinal cord
• Function of Toxin
• Toxin binds to gangliosides in neural tissue ?
  blocks release of inhibitory NTs (?-aminobutyric
  acid, glycine) ? resulting in unrestrained
  excitation of motor neurons, producing continual
  contraction of muscles (tetany)

50
Clostridia

• Pathogenic Clostridia
• Tetanus
• Initial Symptoms
• Cramping twitching of muscle around the wound
• Later Symptoms
• Sweating
• Pain around the area
• Lock-jaw (trismus) clenching of the jaw, muscle
  stiffness in neck and jaw muscles
• Risus sardonicus sarcastic grin (clenched teeth
  w/ parted lips)
• Opisthotonos a tetanus spasm in which head
  heels are bent backward and body is bowed forward
  (arched back)
• Extreme Symptoms
• Progression to other muscle groups
• Violent spasms of trunk and back ? bone fractures
  may result
• Death in violent, extreme cases d/t paralysis
  of respiratory muscles
• Risk Groups
• Elderly
• IV drug users
• Infants neonatal tetanus (tetanus neonatorum)

51
Clostridia

• Pathogenic Clostridia
• Tetanus
• Death
• Paralysis of respiratory muscles
• Convalescence/Immunity
• NO innate immunity toxin bind tightly and
  irreversibly to neural tissue very little freely
  circulating toxin once bound, it is not
  released.
• Repeated infection do NOT produce immunity
• Small amount of toxin in circulation only
• Toxins w/ strong affinity for neural tiss.
• Convalescence NO permanent damage to muscles
• only transient muscle stiffness
• Treatment
• Debridement of necrotic tissue
• Anti-toxin serum counteract the tetanus toxin
  bound to neurons
• Antibiotics
• Anti-spasmotic Rxs or muscle relaxants
• Control/Prevention
• Active immunization w/ DPT series (tetanus toxoid)

52
Clostridia

• Pathogenic Clostridia
• Botulism
• Causative agent C. botulinum
• Neurotoxins A, B, E and F cause human dis
• Neurotoxin A Neurotoxin Hemagglutinin
  conjugation
• Function of hemaglutinin prevents deactivation
  of neurotoxin by the destructive enzymes of GIT
  (gastric enzymes) and lowered (acid) pH of
  Stomach
• Importance in pathogenesis of dis process
  botulinum toxin is absorbed from SI, enters the
  blood, and is carried to peripheral nerves, where
  it binds specifically to receptor sites at NMJ

53
Clostridia

• Pathogenic Clostridia
• Three Types of Botulism
• Food-borne botulism (m/c form of botulism) Food
  poisoning or food intoxication
• Mode of infection
• 1. Ingestion of poorly preserved food containing
  Botulin (Botulinum Toxin)
• Spores not killed sufficiently
• Improper food preservation creates ideal
  environment for spores to germinate anaerobic
  environment created, storage _at_ room temperature,
  alkaline or low acid foods (i.e., canned beans)
  favor growth and spore production
• Botulin product of metabolism most potent
  toxin known lethal dose _at_ 1µ gram
• 2. GIT toxin absorption ? lymphatics
  circulation ? NMJ of skeletal muscle ( site of
  toxin action)
• Action of toxin Toxin binds to v.s. Ca2
  channels at NMJ ? blocks release of ACh (NT) ?
  prevents muscle contraction, resulting in Flaccid
  Paralysis

54
Clostridia

• Pathogenic Clostridia
• Three types of Botulism
• Food-borne Botulism
• Early Symptoms
• Gastrointestinal disturbance nausea, vomiting,
  abdominal pain, diarrhea
• Neuromuscular symptoms
• muscles of the head are affected 1st
• Diplopia blurred or double vision
• Dysphonia difficulty in speaking or slurred
  speech
• Dysphagia difficulty in swallowing
• Critical Symptoms
• Descending paralysis w/ involvement of
  respiratory muscles

55
Clostridia

• Pathogenic Clostridia
• Three types of Botulism
• Food-borne Botulism
• Convalescence/Immunity
• Repeated infections do NOT produce immunity
• Limited amount of toxin in circulation
• Strong affinity of toxin for neural tiss.
• Treatment
• Poly-valent antitoxin therapy neutralization of
  freely circulating toxin ONLY, no effect on bound
  toxin _at_ NMJ
• Gastric lavage (washing out of stomach using a
  stomach tube or catheter) enemas
• Control/Prevention
• Adequate food preservation kill spores (121ºC
  15min)
• Heat all canned food toxin inactivation at 80ºC
  20min

56
Clostridia

• Pathogenic Clostridia
• Three types of Botulism
• Infant Botulism (flaccid paralysis or floppy
  baby head syndrome) m/c form of botulism in US
• Often associated w/ SIDS
• Ingestion of spores from dietary supplement HONEY
• Spores multiply in colon d/t immature state of
  neonatal intestine and flora
• Not problematic in adults GI flora does not
  allow bacterium to grow proliferate
• Indicators of Illness
• Suck gag reflexes ? , drooling, head control
  lost
• Treatment Antibiotic therapy
• Control/Prevention vaccinate pregnant females
• Wound Botulism rare neuroparalytic disease
• Spores enter puncture wound ? in vitro toxin
  produced
• Symptoms similar to food-borne botulism
• Risk group IV drug abusers

57
Chapter 15 Spirochetes

• General Genus Characteristics
• Long, slender, motile, flexible, undulating
  Gram-negative bacilli
• Corkscrew or helical shape
• Can aerobic, anaerobic or facultatively anaerobic
• Some species free-living others normal flora
• 3 genera clinically important to humans
• Treponema (T. pallidum causes syphilis)
• Borrelia (B. burgdorferi Lyme disease B.
  recurrentis relapsing fever)
• Leptospira (L. interrogans casues leptospirosis)

58
Spirochetes

• Structural Features of Spirochetes (fig 15.2
  p.161)
• Unique structure for mobility
• Central protoplasmic cylinder bounded by plasma
  membrane
• Typical Gram (-) cell wall
• Cylinder enveloped by outer sheath composed of
  glycosaminoglycans
• Multiple periplasmic flagella (endoflagella)
• Located between cell wall outer sheath
• Do NOT protrude from cell axial orientation
• Bundles of the axial filaments span entire
  length of cell anchored _at_ both ends
• Rotate similar to external flagella
• Responsible for propelling cell in corkscrew-like
  fashion
• Invasion of host tissue by penetration

59
Treponema

• Family Spirochaetacae
• Genus Treponema
• Species T. pallidum
• General Genus Characteristics
• Corkscrew-type shape
• Thin, coiled spiochete
• 0.1 x 10 µm 5-15 µm
• Strict human pathogen
• Glucose oxidation
• Periplasmic flagella highly motile, twisting
  motion
• Extremely fastidious fragile
• Sensitive to disinfectants, heat drying
• Not routinely cultured in laboratory setting
• Requires immunofluorescent of dark-field
  techniques to observe

60
T. pallidum

• Etiological agent of Syphilis (STD)
• Transmission via sexual or intimate body contact
  (Primary Syphilis) also transplacentally
  (congenital syphilis)
• Mode of entry break in the skin or penetration
  of mucous membranes (i.e., those of genitalia)
• Clinical starts w/ small lesion (chancre)
  progression over 30 years to syphilitic dementia
  or cardiovascular damage

61
T. pallidum

• 3 Stages of Syphilis (fig 15.4 p. 162)
• Primary Stage (highly infectious)
• Inoculation ? 3 months avg. 3 wks. to 1st sx.
• Ulcerative lesions CHANCRE shallow, hard
  genital or oral ulcer w/ firm base develops _at_
  inoculation site PAINLESS
• Primary lesion heals after few weeks, but
  organism continues to spread thru-out body via
  Blood Lymph (pt may think disease is cured)
• Papule ? ulcer ? regional lymphadenopathy
• Asymptomatic period 24 weeks, followed by
  Secondary Stage or Secondary Syphilis

62
T. pallidum

• 3 Stages of Syphilis (fig 15.4 p. 162)
• Secondary Stage (highly infectious)
• Red, maculopapular rash (anywhere on body),
  fever, sore throat, alopecia (hair loss)
• Usually palms of hands, soles of feet, trunk
  (folds)
• Pale, moist, flat papules seen primarily in
  anogenital region Condylomata lata
• 3 months to 1 year
• untreated dis that appeared to resolve, but did
  NOT
• Disseminated disease organisms move thru-out the
  body gt Ag-Ab rxn takes place
• Hepatitis, meningitis, nephritis, chorioretinitis
• Possibilities following this stage
• Complete resolution w/ no further manifestation
  of disease
• Recurrence of secondary lesions
• Progression to latent or clinically inactive
  stage last for many years no sxs of dis.,
  but high levels of Abs 40 of cases ?
  progression to Tertiary Stage or Tertiary Syphilis

63
T. pallidum

• 3 Stages of Syphilis (fig 15.4 p. 162)
• Tertiary Stage (Late)
• Chronic inflammation
• After many years of having the bacteria
• Degeneration of the nervous system (CNS)
• Neurosyphilis may cause dementia or other mental
  changes a major cause of mental insanity
• Cardiovascular lesions, such as aneurysms
• Gramulomatous lesions (gummas) in the liver, skin
  and bones
• Organ system defines late syphilis

64
T. pallidum

• Congenital syphilis
• In utero infection T. pallidum can be
  transmitted thru placenta to fetus after 1st
  10-15 wks of pregnancy
• Can cause death spontaneous abortion of fetus
  stillborn
• If fetus lives, development of condition like
  Secondary Syphilis
• CNS structural abnormalities
• Antibiotic Treatment for pregnant mother
  prevention

65
T. pallidum

• Laboratory Identification/Diagnosis
• 2 general types of Serological tests are used
  Nontreponemal Treponemal
• Nontreponemal screening tests
• Detects nonspecific Ab, Reagin, that reacts with
  Ags from several sources and is produced by some
  diseases other than syphilis.
• Reagin reacts with Cardiolipin Ag (phospholipid
  found in beef heart tiss.) inexpensive, thus
  used in routine screening tests
• Flocculation tests consist of adding Cardiolipin
  Ag to test serum most frequently used VDRL
  (Venereal Disease Research Laboratory) Test
• Positive Cardiolipin forms into fine
  aggregates/floccules
• NOTE other diseases, such as Hepatitis, Diabetes
  and Malaria may give positive reactions to the
  VDRL screening test gt biological false
  positives
• All sera that are positive must be retested to
  confirm w/ specific serological test that detects
  Abs specific for T. pallidum

66
T. pallidum

• Laboratory Identification/Diagnosis
• 2 general types of Serological tests are used
  Nontreponemal Treponemal
• Treponemal specific test for screening result
• m/c FTA-ABS (Fluorescent Treponemal Ab -
  Absorbed) uses freeze-dried T. pallidum that are
  fixed to glass slide
• Test serum is then added if specific Abs are
  present, they react with the T. pallidum
• Slide is rinsed to remove any unattached Abs and
  then covered w/ fluorescent-labeled Abs against
  human ?-globulin
• If test is positive, the spirochete-fluorescent
  Ab complex fluoresces when examined under a
  fluorescence microscope
• Non-specific Abs must be removed from the pts
  sera before testing. Thus, the Absorbed part
  of the test name.

67
T. pallidum

• Laboratory Identification/Diagnosis
• Summary
• Body produces Abs against Syphilis organism
• Ab level ? thru 1º and 2º stages and remains
  thru-out life (treated or untreated)
• Non-Treponemal Test gt screening test for Ags,
  cheap all cases of syphilis will be (), but
  other organisms may show up if another infection
  present false positive Note if negative
  non-treponemal test gt no further testing (pt.
  does not have syphilis)
• Treponemal Test follows any () screening test
  all sera that are () in screening test must be
  retested w/ a more specific serological test that
  detects Abs specific for T. pallidum
• FTA-ABS () for syphilis only rules out false
  positives

68
T. pallidum

• Treatment Prevention
• Single treatment w/ penicillin curative for 1º
  and 2º syphilis alternatives available, too.
• No vaccination for prevention
• Prevention depends on safe sexual practices
• Note more than 1 STD can be passed on _at_ the same
  time

69
Borrelia

• Family Spirochaetaceae
• Genus Borrelia
• Species Borrelia burgdorferi Borrelia
  recurrentis
• General Genus Characteristics
• Relatively large, thin, coiled spirochetes
• Weak staining Gram-negative
• Periplasmic flagella (endoflagella) highly
  motile
• 0.4 x 25 µm
• Linear plasmid and chromosomal DNA

70
Borrelia burgdorferi

• Etiological agent of Lyme Disease
• m/c arthropod-transmitted disease in US
• Transmission via bite of small tick of genus
  Ixodes (Endemic Tickborne) Ixodes scapularis
  deer tick
• Tick must remain attached for 24 hrs before
  bacterial transmission
• Primary reservoir mice, small rodents
• Host animals deer, other mammals
• Occurrence seasonal parallels increased human
  outdoor activity Summer months
• Lyme Disease is present in all 50 states
• Increasing rapidly in recent years
• 40 more cases in 2002 than in 2001 as per CDC

71
Borrelia burgdorferi

• Clinical Disease Lyme Disease
• 2 distinct clinical stages (fig 15.9 p. 165)
• 1st stage (Early Disease) begins 3-32 days after
  tick bite
• Erythema chronicum migrans red, circular lesion
  w/ clear center gt appears at site of the bite
• Lasts from 2-4 wks often expands in circ