Microbiology 6e

1
Chapter 21 Diseases of the Respiratory System
2
Components of the Respiratory System

• Consists of the upper respiratory tract (URT)
• Nasal cavity
• Pharynx
• Larynx
• Trachea
• Bronchi
• Lower respiratory tract
• Lungs
• Entire system is lined with moist epithelium and
  the URT epithelium contains mucus-secreting cells
  and is covered with cilia

3
(No Transcript)
4
Upper Respiratory Tract
5
Lower Respiratory Tract
Bronchioles terminate in alveoli
6
The Upper Respiratory Tract

• Moves oxygen from the atmosphere to the blood and
  removes carbon dioxide from the blood to the
  atmosphere
• Microbes in the air and suspended particles are
  removed by hairs and mucus through the nasal
  cavity
• Sinus infection can occur if microbes enter the
  nasal sinuses (hollow cavities lined with mucous
  membranes)
• Pharynx A common passageway for the respiratory
  and digestive systems

7

• From the pharynx, air and any remaining microbes
  pass through a series of rigid-walled tubes,
  larynx and the trachea
• Larynx (voice box) contains the vocal cords
• Epiglottis is a flap of tissue that prevents food
  and fluids from entering the trachea (windpipe)
• trachea branches into the primary bronchi, all of
  which are lined with cilia

8
The Lower Respiratory Tract

• From the bronchi, air passes into the lungs
• Secondary bronchi divide into smaller
  bronchioles, forming a branching structure known
  as the bronchial tree which greatly increases
  surface area exposed to oxygen and carbon dioxide
  flowing out of lungs
• From the terminal bronchioles, air enters the
  respiratory bronchioles which end in a series of
  saclike alveoli where gas exchange occurs
• Pleura a membrane that covers the surface of
  the lungs and cavities which is lubricated by
  watery serous fluid

9
The Ears

• Exposed to the environment and are subject to
  microbial attack, so they contain physical
  structures to prevent infection
• Each ear is divided into the
• Outer ear has a flaplike pinna (auricle),
  covered with skin, and an auditory canal (skin,
  hair), ceruminous glands are modified sebaceous
  glands that secrete cerumen (earwax)
• The middle ear small air-filled cavity
  containing small bones (ossicles) that transmit
  sound waves from tympanic membrane to the inner
  ear
• The inner ear converts sound waves into nerve
  impulses carried by vestibulocochlear cranial
  nerve (VIII)
• The tympanic membrane (eardrum) separates the
  outer and middle ears

10
Structure of the Ear
11
Normal Microflora of the Respiratory System

• Microbial colonization of lungs would hinder gas
  exchange and very likely damage delicate cells
• Healthy lungs are usually sterile and trachea,
  bronchi, and bronchioles have no microbiota,
  either
• Microbes here are transient and are removed by
  mucociliary escalator and macrophages in alveoli
• Some bacteria like Mycobacterium tuberculosis
  survive inside macrophages and cause infection
• Pharynx has a normal microflora similar to that
  of the mouth
• Upper respiratory tract forms the first line of
  defense against infection and have a normal
  microbiota like the skin
• Staphylococcus and corynebacterium are the most
  numerous

12
Diseases of the Upper Respiratory Tract

• Common and are acquired through the inhalation of
  droplet nuclei from infected persons
• Pharyngitis (sore throat) an infection of the
  pharynx and is frequently caused by a virus
• Laryngitis is an infection of the larynx, often
  with loss of voice
• Epiglottitis is an infection of the epiglottis
  can close the airway and cause suffocation

13
Streptococcal Pharyngitis

• Less than 10 of upper respiratory infections are
  caused by group A B-hemolytic Streptococcus
  pyogenes
• This infection, known as strep throat is most
  common in children 5-15 years old
• Acquired by inhaling droplet nuclei from active
  cases or healthy carriers
• Symptoms tender tonsils with white pus-filled
  lesions, high fever, acute throat soreness,
  chill, headache

14
Diphtheria

• Although fewer than 5 cases per year in the U.S.,
  this disease was once a feared killer
• Still a problem today in the former Soviet Union
• Sequelae (adverse signs that follow a disease)
  are common and include myocarditis,
  polyneuritis and neurologic problems
• Causative agent Corynebacterium diphtheriae
• Preventable through DTP vaccine
• Diphtheria, tetanus and pertussis

15
Corynebacterium diphtheriathe cause of diphtheria
16

• Diphtheroids are corynebacteria found in or on
  such body sites as nose, throat, nasopharynx,
  urinary tract and skin and are not toxin
  producers
• To produce toxin, the bacterium must be infected
  by an appropriate strain of bacteriophage in the
  lysogenic prophage state
• The toxin inhibits protein synthesis, leading to
  cell death
• Pseudomembrane damaged epithelial cells, fibrin
  and bloods cells combine and can block airway

17
Ear Infections

• Commonly occur as otitis media in the middle ear
  and otitis externa in the external auditory canal
• Streptococcus pneumoniae, Streptococcus pyogenes,
  and Haemophilus influenzae account for about half
  of the cases of otitis media and usually
  accompanied with a puslike exudate
• Staphylococcus aureus and Pseudomonas aeruginosa
  are the usual causative agents of otitis external
  
• Disease is treated with antibiotics (penicillin)
• Tubes may be added to prevent fluid accumulation
  and chronic infections

18
Treating middle ear infections
19
The Common Cold (Coryza)

• Probably causes more misery and loss of work
  hours than any other infectious disease, but is
  not life-threatening
• Rhinoviruses are the most common cause of colds
  and coronaviruses and the second most common
  cause of colds
• Ubiquitous and present year round, but most
  infections occur in early fall or spring
• 2-4 day incubation period and lasts about 1 week
• Signs and symptoms excessive mucus secretion,
  sneezing, inflammation of mucous membranes, sore
  throat, headache, cough

20
Para influenza

• Caused by 1 of 4 potential viruses
• 2 of them can cause croup
• acute obstruction of the larynx resulting in a
  cough like a seals bark
• Cough, hoarseness, nasal inflammation,
  pharyngitis, bronchitis and sometimes pneumonia
• No vaccine available, but humans produce IGA
  antibodies to aid in resistance
• Spread by direct contact

21
Bacterial Lower Respiratory Diseases (Whooping
Cough)

• Also called pertussis, is a highly contagious
  disease known only in humans
• Bordetella pertussis, a small, aerobic,
  encapsulated, gram-negative coccobacillus is the
  usual causative agent
• The disease progress through three stages
• Catarrhal characterized by fever, sneezing,
  vomiting, and a mild, dry persistent cough
• Paroxysmal begins as mucus and masses of
  bacteria fill the airway and immobilize the cilia
  with strong violent cough
• Convalescent enter this stage after 1-6 weeks.
  Secondary infections are common at this stage

22

• Preventable through DTP vaccine
• Diphtheria, tetanus and pertussis
• Major health problem in developing nations due to
  lack of immunizations
• Treated with antitoxins and erythromycin as well
  as suctioning, re-hydration and oxygen therapy

23
Whooping Cough Culturing Technique
24
Classic Pneumonia

• An inflammation of lung tissue, can be caused by
  various microorganisms/parasites
• Organisms initiate the disease process by
  colonizing the upper respiratory tract and enter
  the lower respiratory tract accidentally during a
  deep breath, suppressed cough or large amount of
  mucus
• Pneumonias are classified by site of infection as
  lobar or bronchial
• Pleurisy inflammation of the pleural membranes
  that causes painful breathing often accompanies
  lobar pneumonia

25

• Transmitted by respiratory droplets
• Violent chills, high fever, chest pain, cough
• Most cases have 5 mortality rate with treatment
• Klebsiella pneumonia has a 50 mortality rate
• Treatments are cephalosporin or penicillin
• Immunization is effective against 80 of
  pneumococcal
• Predisposing factors age, chilling, drugs,
  disease state, anesthesia, alcoholism

26
Pneumonia-causing bacteria
27
Mycoplasma Pneumonia

• One of the tiniest bacterial pathogens known
• Usually causes mild, and sometime inapparent,
  upper respiratory infections
• Primary atypical pneumonia 3-10 contract a
  mild pneumonia with an insidious onset (no
  respiratory signs, but fever and malaise)
• Walking pneumonia patients often remain
  ambulatory, unlike classic pneumonia cases
• Treated with erythromycin and tetracycline
• Penicillin has no effect due to lack of cell wall

28
Mycoplasma cells (151,000X)
29
Legionnaires Disease

• 1976 many war veterans attending a convention
  became victims of this mysterious ailment
• A weakly gram-negative, strictly aerobic bacillus
  with a fastidious nutritional requirement
• Doesnt ferment sugars and has an obscure life
  cycle
• Transmitted when organisms growing in soil or
  water become airborne and enter the patients
  lungs as an aerosol
• Air conditions, ornamental fountains and produce
  sprayers have been implicated in spread of disease

30

• Symptoms Fever, chills, headache, diarrhea,
  vomiting, chest and abdominal pain
• Treatment erythromycin
• Prevention chlorination of water and
  disinfection of equipment

31
Legionella pneumophilathe cause of Legionaires
disease
32
Tuberculosis (TB)

• Massive global health problem
• 3 million deaths annually with 10 million new
  cases
• 1/3 of the global population has TB
• Causative agent Mycobacterium
• primarily Mycobacterium tuberculosis
• Straight or slightly curved rods, slow-growing,
  that stain acid-fast because of the mycolic acid
  in their cell wall
• Acquired by the inhalation of droplet nuclei or
  respiratory secretions or particles of dry sputum

33
TB Disease

• Organisms multiply slowly inside white blood
  cells which eventually rupture
• As additional cells are infected, an acute
  inflammatory response occurs resulting in a large
  quantity of fluid producing pneumonia-like
  symptoms
• Tubercles massive tissue necrosis or solidify
  and form these chronic granulomas
• Treatment isoniazid and rifapin for 1 year or
  longer
• Vaccine is available for high risk individuals

34
Psittacosis and Ornithosis

• Parrot or bird fever
• Wild and domestic birds can be infected, often
  without symptoms
• Causative agent for both forms Chlamydia
  psittaci
• Sore throat, coughing, labored breathing, fever,
  headache and chills
• No vaccine available treated with tetracycline

35
Q (Query) Fever

• First described in Queensland, Australia
• Causative agent Coxiella burnetii, and
  organisms included among the rickettsias
• Cattle, sheep, domestic and wild animals are
  carriers
• Bacteria are transmitted via tick bites, feces,
  and respiratory droplets
• Fever, chills, headache, malaise and severe
  sweats
• Treated with tetracycline or floroquinoline
  vaccine is available
• Type of endospore may be formed giving it some
  resistance

36
Nocardiosis

• Characterized by tissue lesions and abscesses
• Causative agent Nocardia asteroides, an
  aerobic, acid-fast staining, filamentous
  bacterium
• Found in soil and water
• Disease initiated by inhalation of organisms
• Usually occurs in immunosupressed patients
• Treated with sulfa drugs combined with
  trimethoprim
• With treatment mortality is still around 50

37
Nocardia asteroides (1,400X)
38
Influenza

• The last great remaining great plague from the
  past
• Caused by orthomyxoviruses
• RNA viruses with an envelope surface antigen
  hemagglutinin responsible for their infectivity
• Neuraminidase helps virus penetrate mucus layer
  protecting the respiratory epithelium
• Influenza viruses have a tendency to under go
  antigenic variations or mutation of viral
  antigens

39
Swine Flu--the height of the great flu pandemic
of 1918
40
A colorized TEM of influenza virus type A
(85,243X)
41
Antigenic Variation in Influenza

• Occurs by two processes
• Antigenic drift results from mutations in genes
  that code for hemagglutinin and neuraminidase
  which change the configuration of the antigen
  that stimulates production of specific antibodies
• Antigenic shift results from gene reassortment,
  possibly after two different viruses infect the
  same cell (e.g. bird and human influenza virus
  infect a pig cell and exchange large segments of
  their genome)

42

• Transmitted through respiratory droplets and
  contaminated secretions
• Incidence increases from late Nov. to early April
  
• Symptoms occur within 48 hrs and last about 3
  days
• Fever, malaise, sore muscles, cough, sore throat,
  nasal discharge and gastroenteritis
• Secondary bacterial pneumonias are the most
  serious complication of a flu infection
• Vaccine is available and new drug treatments are
  being developed

43
Flu mist vaccine is inhaled, rather than injected
44
Severe Acute Respiratory Syndrome (SARS)

• 2002 people in China began falling sick of a
  new respiratory disease
• 305 cases of atypical pneumonia caused by a
  coronavirus
• By 2003 it had spread to 29 countries, infecting
  over 8000 people, killing over 700
• Symptoms high fever, dry cough, shortness of
  breath, difficulty breathing, and X-rays
  indicating pneumonia
• Virus spread by close contact with an infected
  person, usually by exhaled or coughed aerosol
  droplets

45
SARS virus (253,467X)
46
Pneumocystis Pneumonia

• Causative agent the opportunistic fungus
  Pneumocystis jiroveci
• Invades cells of the lungs and causes alveolar
  septa to thicken and the epithelium to rupture
• Result foamy exudate from cells collect in the
  alveoli
• Occurs in infants, elderly and immunocompromised
  such as AIDS patients
• Fungus can spread to other organs and cause
  extrapulmonary infections

47
Pneumocystis jiroveci in sputum--a frequent cause
of pneumonia in AIDS patients (353X)
48

• Aspergillosis farmers lung
• Caused by Aspergillus species when fungal spores
  are inhaled
• Results in large mycelium that may obstruct
  airflow
• Surgery may be required to remove fungus balls
• Also triggers asthma

49
Parasitic Respiratory Diseases

• Lung fluke Paragonimus westermani found in many
  parts of Asia and the South Pacific
• Life cycle starts when egg-laden feces are
  released into water
• Eggs hatch and invade a snail and then a crab or
  crayfish where larval or metacercariae develop
• Transmitted when humans ingest contaminated
  shellfish resulting in chronic cough, bloody
  sputum and difficulty breathing

50

• Larvae bores through digestive tract and through
  the diaphragm into the lungs
• Larvae mature and lay eggs which are coughed up
  and swallowed exiting the body in fecal material
• Human is the definitive host
• harbors sexually mature life stage
• Treated with praziquantel and prevented by
  thoroughly cooking shellfish

51
The lung fluke Paragonimus westermani (13X)