Ch 24: Microbial Diseases of the Respiratory System

1
Ch 24 Microbial Diseases of the Respiratory
System

• Infections of the upper respiratory system are
  the most common type of infection.
• Pathogens that enter the respiratory system can
  infect other parts of the body.

2
The Upper Respiratory System

• Consists of
• Nose
• Pharynx (throat)
• Middle ear
• Eustachian tubes

3
Structures of Upper Respiratory System

• Coarse hairs in the nose filter large particles
  from air entering the respiratory tract.
• The ciliated mucous membranes of the nose and
  throat trap airborne particles and remove them
  from the body.
• Lymphoid tissue, tonsils, and adenoids provide
  immunity to certain infections.

4
The Lower Respiratory System

• Consists of
• Larynx
• Trachea
• Bronchial tubes
• Alveoli
• Pleura

5
Structures of Lower Respiratory System
6
The Lower Respiratory System

• The ciliary escalator of the lower respiratory
  system helps prevent microorganisms from reaching
  the lungs.
• The normal microbiota of the nasal cavity and
  throat can include pathogenic microorganisms.
• Microbes in the lungs can be phagocytized by
  alveolar macrophages.
• Respiratory mucus contains IgA antibodies.

7
Mucocilary Escalator

• The lower respiratory system is usually sterile
  because of the action of the ciliary escalator.
• Microorganisms hoping to infect the respiratory
  tract are caught in the sticky mucus and moved up
  by the mucociliary escalator.

8
Upper Respiratory System Diseases

• Most respiratory tract infections are
  self-limiting.
• Often caused by bacteria viruses in combination

9
Upper Respiratory System Diseases

• Pharyngitis inflammation of the pharynx
• Laryngitis swelling and irritation
  (inflammation) of the voice box (larynx)
• Tonsillitis inflammation of the tonsils
• Sinusitis inflammation of the sinuses
• Epiglottitis inflammation of the cartilage that
  covers the trachea H. influenzae type b
  most threatening

10
Streptococcal Pharyngitis

• Also called strep throat
• Streptococcus pyogenes
• Gram positive cocci chains
• Resistant to phagocytosis
• Streptokinases lyse clots
• Streptolysins are cytotoxic
• Diagnosis by enzyme immunoassay (EIA) tests (have
  replaced latex agglutination tests)

Characterized by lack of cough
11
Scarlet Fever

• Streptococcus pyogenes
• Pharyngitis
• Erythrogenic toxin produced by lysogenized S.
  pyogenes
• Symptoms include a red rash (sandpaper), high
  fever, and a red, enlarged tongue.

12
Diphtheria

• Corynebacterium diphtheriae Gram-positive rods
• Diphtheria toxin produced by lysogenized C.
  diphtheriae

• A membrane, containing fibrin and dead human and
  bacterial cells, forms in the throat and can
  block the passage of air.

13
Diphtheria

• Diphtheria membrane Fibrin, tissue, bacterial
  cells

• Leading infectious killer of children in U.S. in
  1935

14
Diphtheria

• Still common in developing countries where
  immunizations aren't given routinely.
• Up to 40 to 50 of those who don't get treated
  can die.
• The exotoxin inhibits protein synthesis, and
  heart, kidney, or nerve damage may result.
• Prevented by DTaP vaccine
• Diphtheria toxoid
• Cutaneous diphtheria (esp. in persons gt30 yrs)
• Infected skin wound leads to slow-healing ulcer

15
Otitis Media

• Earache-can occur as a complication of nose and
  throat infections.
• Strep. pneumoniae (35)
• Hem. influenzae (2030)
• Moraxella catarrhalis (1015)
• Strep. pyogenes (810)
• Staph. aureus (12)
• Incidence of S. pneumoniae reduced by vaccine

Pus accumulation causes pressure on the eardrum.
16
The Common Cold

• Any one of approximately 200 different viruses
  can cause the common cold Rhinoviruses cause
  about 50 of all colds.
• Coronaviruses (1520)
• Symptoms include sneezing, nasal secretions, and
  congestion.

17
Rhinovirus

• Grow best slightly below body temperature.
• The incidence of colds increases during cold
  weather, possibly because of increased
  interpersonal indoor contact or physiological
  changes.
• Antibodies are produced against the specific
  viruses.

18
Diseases in Focus Diseases of the Upper
Respiratory System

• A patient presents with fever and a red, sore
  throat. Later, a grayish membrane appears in the
  throat. Gram-positive rods were cultured from the
  membrane.
• Can you identify infections that could cause
  these symptoms?

Diptheria
19
Lower Respiratory System Diseases

• Bacteria, viruses, and fungi cause
• Bronchitis
• Bronchiolitis
• Pneumonia

20
Pertussis (Whooping Cough)

• Bordetella pertussis
• Gram-negative coccobacillus
• Capsule
• Tracheal cytotoxin of cell wall damaged ciliated
  cells
• Pertussis toxin
• Prevented by DTaP vaccine (acellular Pertussis
  cell fragments)

21
Pertussis (Whooping Cough)

• Aerosal Transmission from human to human
• Stage 1 Catarrhal stage, like common cold
• Stage 2 Paroxysmal stageviolent coughing sieges
• Stage 3 Convalescence stage

22
Tuberculosis

• Mycobacterium tuberculosis
• Acid-fast rod transmitted from human to human
  via the gastrointestinal route

23
Tuberculosis

• M. bovis lt1 U.S. cases not transmitted from
  human to human usually affect the bones or
  lymphatic system.
• M. avium-intracellulare complex infects people
  with late-stage HIV infection
• The mycolic acids of the cell wall are an
  important factor in the pathogenicity
• Also gives it resistance to drying and
  disinfectants
• Lesions formed by M. tuberculosis are called
  tubercles dead macrophages and bacteria form the
  caseous lesion that might calcify and appear in
  an X-ray image as a Ghons complex.

24
Ghons complex
25
Tuberculosis

• Urease test for Mycobacterium tuberculosis

26
Tuberculosis
27
Worldwide Distribution of Tuberculosis
28
U.S. Distribution of Tuberculosis
29
The Pathogenesis of Tuberculosis
30
The Pathogenesis of Tuberculosis
31
The Pathogenesis of Tuberculosis
32
The Pathogenesis of Tuberculosis
33
The Pathogenesis of Tuberculosis
34
Treatment of Tuberculosis

• Treatment Prolonged treatment with multiple
  antibiotics
• Vaccines BCG, live, avirulent M. bovis not
  widely used in United States

35
A Positive Tuberculin Skin Test

• A positive tuberculin skin test can indicate
  either an active case of TB, prior infection, or
  vaccination and immunity to the disease.

36
Diagnosis of Tuberculosis

• Tuberculin skin test screening
• Positive reaction means current or previous
  infection
• Followed by X-ray or CT exam, acid-fast staining
  of sputum, culturing of bacteria

37
Pneumococcal Pneumonia

• Streptococcus pneumoniae
• Gram-positive encapsulated diplococci (lancet)

38
Pneumococcal Pneumonia

• Symptoms Infected alveoli of lung fill with
  fluids interferes with oxygen uptake
• Diagnosis Optochin-inhibition test or bile
  solubility test serological typing of bacteria
• Treatment Penicillin, fluoroquinolones
• Prevention Pneumococcal vaccine

39
Haemophilus influenzae Pneumonia

• Gram-negative coccobacillus
• Predisposing factors Alcoholism, poor nutrition,
  cancer, or diabetes
• Symptoms Resemble those of pneumococcal
  pneumonia
• Diagnosis Isolation special media for
  nutritional requirements (chocolate agar)
• Treatment Cephalosporins

40
Mycoplasmal Pneumonia

• Primary atypical pneumonia walking pneumonia
• Mycoplasma pneumoniae
• Pleomorphic, wall-less bacteria
• Common in children and young adults

41
Mycoplasma pneumoniae
42
Mycoplasmal Pneumonia

• Symptoms Mild but persistent respiratory
  symptoms low fever, cough, headache
• Diagnosis PCR and serological testing
• Treatment Tetracyclines

43
Legionellosis

• Legionella pneumophila Gram-negative rod
• Legionnaires' disease acquired its name in July
  1976 when an outbreak of pneumonia occurred among
  people attending a convention of the American
  Legion in Philadelphia.
• Found in water (its reservoir)
• Transmitted by inhaling aerosols not transmitted
  from human to human

44
Legionellosis

• Symptoms Potentially fatal pneumonia that tends
  to affect older men who drink or smoke heavily
• Diagnosis Culture on selective media, DNA probe
• Treatment Erythromycin

45
Psittacosis (Ornithosis)

• Chlamydophila psittaci
• Gram-negative intracellular bacterium
• Transmitted to humans by elementary bodies from
  bird droppings
• Seldom transmitted from human to human
• Reorganizes into reticulate body after being
  phagocytized

46
Psittacosis (Ornithosis)

• Symptoms Symptoms, if any, are fever, headache,
  chills
• Diagnosis Growth of bacteria in eggs or cell
  culture
• Treatment Tetracyclines

47
Psittacosis (Ornithosis)
48
Chlamydial Pneumonia

• Chlamydophila pneumoniae
• Transmitted from human to human

49
Chlamydial Pneumonia

• Symptoms Mild respiratory illness common in
  young people resembles mycoplasmal pneumonia
• Diagnosis Serological tests
• Treatment Tetracyclines

50
Q Fever

• Causative agent Coxiella burnetii, Intracellular
  bacteria
• Reservoir Large mammals
• Tick vector carries the bacteria
• Can be transmitted via unpasteurized milk

51
Coxiella burnetii, the Cause of Q Fever
52
Q Fever

• Symptoms Mild respiratory disease lasting 12
  weeks occasional complications such as
  endocarditis occur
• Diagnosis Growth in cell culture
• Treatment Doxycycline and chloroquine

53
Melioidosis

• Causative agent by Burkholderia pseudomallei
  gram negative rod
• Reservoir Soil
• Mainly in southeast Asia and northern Australia
• Symptoms Pneumonia, or tissue abscesses and
  severe sepsis
• Diagnosis Bacterial culture
• Treatment Ceftazidime

B. pseudomallei colonies on Ashdown's agar
showing the characteristic cornflower head
morphology.
54
Diseases in Focus Common Bacterial Pneumonias

• A 27-year-old man with a history of asthma was
  hospitalized with a 4-day history of progressive
  cough and 2 days of spiking fevers. Gram-positive
  cocci in pairs were cultured from a blood sample.
• Can you identify infections that could cause
  these symptoms?

Streptococcus pneumoniae was identified by the
Gram reaction, morphology, and the
optochin-inhibition test.
55
Viral Pneumonia

• Viral pneumonia occurs as a complication of
  influenza, measles, or chickenpox
• Viral etiology suspected if no other cause is
  determined

56
Respiratory Syncytial Virus (RSV)

• The most common viral respiratory disease in
  infants 4500 deaths annually
• Causes cell fusion (syncytium) in cell culture
• Symptoms Pneumonia in infants
• Diagnosis Serological test for viruses and
  antibodies
• Treatment Ribavirin, palivizumab

57
Influenza (Flu)

• Symptoms Chills, fever, headache, and muscle
  aches
• No intestinal symptoms
• 1 mortality, very young and very old
• Treatment Zanamivir and oseltamivir inhibit
  neuraminidase
• Prophylaxis Multivalent vaccine (currently grown
  in Embryonated egg cultures

58
The Influenza Virus

• Hemagglutinin (HA) spikes used for attachment to
  host cells
• Neuraminidase (NA) spikes used to release virus
  from cell

59
The Influenza Virus

• Antigenic shift
• Probably due to genetic recombination between
  different strains infecting the same cell
• Process by which at least two different strains
  of a virus, combine to form a new subtype having
  a mixture of the surface antigens of the two
  original strains.
• Changes in HA and NA spikes so is the cause of
  recurring epidemics
• Antigenic shift, however, occurs only in
  influenzavirus A because it infects more than
  just humans

60
Antigenic drift

• Natural mutation over time of known strains Point
  mutations in genes encoding HA or NA spikes
• Antigenic shift is important as it is a pathway
  that viruses may follow to enter a new niche, and
  so should not be overlooked in the emergence of
  new viral pathogens. May involve only 1 amino
  acid
• Antigenic drift occurs in all types of influenza

61
Influenza Serotypes
62
Fungal Infections

• Fungal spores are easily inhaled they may
  germinate in the lower respiratory tract.
• The incidence of fungal diseases has been
  increasing in recent years.
• The mycoses can be treated with amphotericin B.

63
Histoplasmosis

• Histoplasma capsulatum, dimorphic fungus
• Bird droppings provide nutrients, especially
  nitrogen, to the fungus
• Symptoms similar to tuberculosis (identify by
  microscopic exam of sputa serologic tests)

64
Histoplasmosis Distribution
65
Coccidioidomycosis

• Causative agent Coccidioides immitis
  (inhalation of arthroconidia)
• Reservoir Desert soils of Southwest U.S.
• Symptoms Fever, coughing, weight loss
• Diagnosis Serological tests
• Treatment Amphotericin B

66
The Life Cycle of Coccidioides immitis
67
U.S. Endemic Area for Coccidioidomycosis
Increased cases due to of increases in the
number of elderly residents, the number of
HIV/AIDS patients, and drought
68
Pneumocystis Pneumonia

• Causative agent Pneumocystis jirovecii , a
  parasite
• Reservoir Unknown possibly humans or soil
• Symptoms Pneumonia
• Diagnosis Microscopy
• Treatment Trimethoprim
• Pneumocystis is opportunistic pathogen
• It usually does not cause disease, but can if the
  hosts resistance is low

69
The rupture of a cyst results in the development
of trophozoites
70
Blastomycosis

• Causative agent Blastomyces dermatitidis
• Reservoir Soil in Mississippi valley area
• Symptoms Abscesses extensive tissue damage
• Diagnosis Isolation of pathogen
• Treatment Amphotericin B

71
Other Fungi Involved in Respiratory Disease

• Systemic
• Predisposing factors
• Immunocompromised state
• Cancer
• Diabetes
• Aspergillus fumigatus
• Mucor
• Rhizopus

72
Diseases in Focus Diseases of the Lower
Respiratory System

• A worker was hospitalized for acute respiratory
  illness. He had been near a colony of bats. The
  mass was surgically removed. Microscopic
  examination of the mass revealed ovoid yeast
  cells.
• Can you identify infections that could cause
  these symptoms?

The geographic location and presence of bats
strongly suggests histoplasmosis.