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Title: Microbiology for the Health Sciences Chapter 14' Pathogenesis of Infectious Diseases


1
Microbiology for the Health SciencesChapter
14.Pathogenesis of Infectious Diseases
2
Chapter 14 Outline
  • Introduction
  • Infection Versus Infectious Disease
  • Why Infection Does Not Always Occur
  • Four Periods or Phases in the Course of an
    Infectious Disease
  • Localized Versus Systemic Infections
  • Acute, Subacute, and Chronic Diseases
  • Symptoms of a Disease Versus Signs of a Disease
  • Latent Infections
  • Primary Versus Secondary Infections
  • Steps in the Pathogenesis of Infectious Diseases
  • Virulence
  • Virulence Factors (Attributes That Enable
    Pathogens to Attach, Escape Destruction, and
    Cause Disease)

3
Introduction
  • The prefix path refers to disease.
  • Pathogenicity means the ability to cause disease.
  • Pathogenesis refers to the steps or mechanisms
    involved in the development of a disease.

4
Infection Versus Infectious Disease
  • An infectious disease is a disease caused by a
    microbe, and the microbes that cause infectious
    diseases are collectively referred to as
    pathogens.
  • Infection is commonly used as a synonym for
    infectious disease (e.g., an ear infection is an
    infectious disease of the ear).
  • Microbiologists reserve the word infection to
    mean colonization by a pathogen the pathogen may
    or may not go on to cause disease.
  • A person can be infected with a pathogen, but not
    have an infectious disease.

5
Why Infection Does Not Always Occur
  • The microbe may land at an anatomic site where it
    is unable to multiply.
  • Many pathogens must attach to specific receptor
    sites before they are able to multiply and cause
    damage.
  • Antibacterial factors may be present at the site
    where the pathogen lands.
  • Indigenous microflora of that site may inhibit
    growth of the foreign microbe (i.e., microbial
    antagonism).
  • The indigenous microflora may produce
    antibacterial factors (i.e., bacteriocins) that
    destroy the pathogen.
  • The individuals nutritional and overall health
    status often influences the outcome of the
    pathogen-host encounter.
  • The person may be immune to that particular
    pathogen.
  • Phagocytes present in the blood may destroy the
    pathogen.

6
Four Periods or Phases in the Course of an
Infectious Disease
  • The incubation period
  • The prodromal period
  • The period of illness
  • The convalescent period

7
Localized Versus Systemic Infections
  • Localized Infections
  • Once an infectious process is initiated the
    disease may remain localized or it may spread
    examples of localized infections are pimples,
    boils and abscesses.
  • Systemic Infections
  • When the infection spreads throughout the body it
    is said to have become systemic or generalized
    an example is miliary tuberculosis caused by
    Mycobacterium tuberculosis.

8
Acute, Subacute, and Chronic Diseases
  • An acute disease is one that has a rapid onset,
    and is usually followed by a relatively rapid
    recovery examples are measles, mumps and
    influenza.
  • A chronic disease has a slow onset and lasts a
    long time examples are tuberculosis, leprosy and
    syphilis.
  • A subacute disease is one that comes on more
    suddenly than a chronic disease, but less
    suddenly than an acute disease an example would
    be bacterial endocarditis.

9
Symptoms of a Disease Versus Signs of a Disease
  • A symptom of a disease is defined as some
    evidence of a disease that is experienced by the
    patient something that is subjective for
    example, aches or pains, ringing in the ears,
    blurred vision, nausea, dizziness, etc.
  • There are symptomatic and asymptomatic diseases.
    In a symptomatic disease, the patient is
    experiencing symptoms. In an asymptomatic
    disease, the patient is not experiencing any
    symptoms.
  • A sign of a disease is defined as some type of
    objective evidence of a disease for example,
    elevated blood pressure, abnormal heart sounds,
    abnormal pulse rate, abnormal laboratory results,
    etc.

10
Latent Infections
  • Latent infections are infectious diseases that go
    from being symptomatic to asymptomatic, and then,
    later, go back to being symptomatic.
  • Examples include syphilis and herpes virus
    infections such as cold sores, genital herpes,
    and shingles.

11
Primary Versus Secondary Infections
  • One infectious disease may commonly follow
    another in such cases, the first disease is
    referred to as a primary infection and the second
    disease is referred to as a secondary infection.
  • Example serious cases of bacterial pneumonia
    frequently follow mild viral respiratory
    infections.
  • During the primary infection, the virus causes
    damage to the ciliated epithelial cells of the
    respiratory tract these cells are then unable to
    clear opportunistic bacterial pathogens from the
    respiratory tract, leading to the secondary
    infection (pneumonia).

12
Steps in the Pathogenesis of Infectious Diseases
  • A common sequence of steps in the pathogenesis of
    infectious diseases is
  • Entry of the pathogen into the body.
  • Attachment of the pathogen to some tissue(s)
    within the body
  • Multiplication of the pathogen.
  • Invasion or spread of the pathogen.
  • Evasion of host defenses.
  • Damage to host tissue(s).

13
Virulence
  • The term virulent is sometimes used as a
    synonym for pathogenic.
  • There may be virulent (pathogenic) strains and
    avirulent (nonpathogenic) strains of a particular
    species.
  • Virulent strains are capable of causing disease
    avirulent strains are not.
  • For example, toxigenic (toxin-producing)strains
    of Corynebacterium diphtheriae can cause
    diphtheria, but nontoxigenic strains of C.
    diphtheriae cannot. Thus, the toxigenic strains
    are virulent, but the nontoxigenic strains are
    not.

14
Virulence (cont.)
  • Sometimes, virulence is used to express the
    measure or degree of pathogenicity.
  • Example It only takes 10 Shigella cells to cause
    shigellosis, but it takes between 100 and 1,000
    Salmonella cells to cause salmonellosis! Thus,
    Shigella is more virulent than Salmonella.
  • Example Some strains of Streptococcus pyogenes
    (e.g., the flesh-eating strains) are more
    virulent than other strains of S. pyogenes.
  • Example Some strains of S. aureus produce toxic
    shock syndrome, but other strains of S. aureus do
    not. Those that do are considered more virulent.

15
Virulence Factors
  • Virulence factors are attributes that enable
    pathogens to attach, escape destruction, and
    cause disease.
  • Virulence factors are phenotypic characteristics
    that are dictated by the organisms genotype.
    Examples
  • Adhesins (ligands) - special molecules on the
    surface of pathogens - are considered to be
    virulence factors because they enable pathogens
    to recognize and bind to particular host cell
    receptors.
  • Pili (bacterial fimbriae) are considered to be
    virulence factors because they enable bacteria to
    attach to surfaces, like tissues within the human
    body.

16
Virulence Factors
17
Obligate Intracellular Pathogens
  • Pathogens that must live within host cells in
    order to survive and multiply, are referred to as
    obligate intracellular pathogens (examples
    Rickettsia and Chlamydia spp.).
  • Intraleukocytic pathogens (e.g., Ehrlichia spp.
    and Anaplasma phagocytophilum) live within white
    blood cells, causing diseases known as
    ehrlichiosis and anaplasmosis.
  • Plasmodium spp. (which cause malaria) and Babesia
    spp. (which cause babesiosis) are examples of
    intraerythrocytic pathogens.

18
Facultative Intracellular Pathogens
  • Facultative intracellular pathogens are capable
    of both an intracellular and extracellular
    existence.
  • Intracellular Survival Mechanisms
  • A cell wall composition that resists digestion
    (e.g., Mycobacterium tuberculosis).
  • Fusion of lysosomes with phagosomes is prevented.
  • Production of phospholipases that destroy the
    phagosome membrane, thereby preventing
    lysosome-phagosome fusion.
  • Other unknown mechanisms.

19
Capsules and Flagella
  • Capsules and flagella are considered to be
    virulence factors.
  • Examples of encapsulated bacteria S. pneumoniae,
    K. pneumoniae, H. influenzae and N. meningitidis.
  • Flagella are virulence factors because they
    enable flagellated bacteria to invade aqueous
    areas of the body may also help the bacterium to
    escape phagocytosis.

Photomicrograph of Streptococcus pneumoniae
showing capsules (the unstained halos that
surround the bacteria).
20
Exoenzymes
  • The major mechanisms by which pathogens cause
    disease are the exoenzymes or toxins that they
    produce.
  • Exoenzymes released by bacteria include
  • Necrotizing enzymes Coagulase
  • Kinases Hyaluronidase
  • Collagenase Hemolysins
  • Leithinase

21
Toxins
  • Toxins are poisonous substances released by
    various pathogens. There are 2 kinds
  • Endotoxins
  • Produced by Gram-negative bacteria as a part of
    their cell wall structure.
  • Can cause serious, adverse, physiologic effects
    such as fever and shock.
  • Exotoxins
  • Poisonous proteins secreted by a variety of
    pathogens.
  • Types of exotoxins include neurotoxins,
    enterotoxins, exfoliative toxin, erythrogenic
    toxin, and leudocidins.

22
Mechanisms by Which Pathogens Escape Immune
Responses
  • Antigenic Variation
  • Some pathogens evade the immune system by
    changing their surface antigens antigenic
    variation examples, Neisseria gonorrhoeae and
    Borrelia recurrentis.
  • Camouflage and Molecular Mimicry
  • Some organisms conceal their foreign nature by
    coating themselves with host proteins like
    camouflage (e.g., adult schistosomes).
  • Destruction of Antibodies
  • Some pathogens produce IgA protease, an enzyme
    that destroys some of the hosts antibodies
    example, Haemophilus influenzae.

23
Review of Key Points
  • Microbiologists define infection as colonization
    by a pathogen once colonized, the person is said
    to be infected with the pathogen, regardless of
    whether the pathogen is causing disease.
  • When individuals are exposed to a pathogen, the
    pathogens may or may not cause disease, depending
    on a number of factors (e.g., nutritional status
    and health of the host, virulence of the
    pathogen).
  • Pathogenicity is the ability of a microbe to
    cause disease, whereas pathogenesis refers to the
    actual steps that are involved in the development
    of a disease.

24
Review of Key Points (cont.)
  • Signs of a disease are various types of objective
    evidence of a disease, such as blood pressure,
    pulse, etc. Symptoms of a disease are various
    types of subjective evidence of a disease
    experienced by the patient.
  • Some pathogens manifest themselves periodically,
    remaining dormant between episodes latent
    infections.
  • An infection may be acute, subacute or chronic
    localized or systemic and symptomatic or
    asymptomatic.
  • The 4 phases of an infectious disease are the
    incubation period, prodromal period, period of
    illness, and convalescent period.

25
Review of Key Points (cont.)
  • Virulence is a measure or degree of
    pathogenicity.
  • Virulence factors are phenotypic characteristics
    of a microorganism that enable it to cause
    disease. Examples of virulence factors include
    capsules, flagella and pili.
  • The two major virulence factors by which bacteria
    cause disease are exoenzymes and toxins.
  • Toxins include endotoxins and exotoxins.
  • The 2 most important categories of phagocytes in
    the human body are macrophages and neutrophils.

26
Review of Key Points (cont.)
  • Some pathogens are able to escape immune
    responses.
  • Mechanisms used to evade immune responses
    include antigenic variation, camouflage,
    molecular mimicry, and destruction of antibodies.

27
Microbiology for the Health SciencesChapter
17.Major Viral, Bacterial,and Fungal Diseases
of Humans
28
Chapter 17 Outline
  • Introduction
  • Infectious Diseases of the Skin
  • Infectious Diseases of the Ears
  • Infectious Diseases of the Respiratory System
  • Infectious Diseases of the Oral Region
  • Infectious Diseases of the Gastrointestinal (GI)
    Tract
  • Infectious Diseases of the Genitourinary (GU)
    System
  • Infectious Diseases of the Circulatory System
  • Infectious Diseases of the Central Nervous System
    (CNS)
  • Appropriate Therapy for Viral, Bacterial, and
    Fungal Infections

29
Introduction
  • There are 2 general categories of diseases
  • Microbial intoxications
  • Infectious diseases
  • This chapter (Chapter 17) describes various
    infectious diseases by anatomic site.
  • IMPORTANT! Be able to associate a particular
    infectious disease with the appropriate pathogen!
  • Also, be able to identify the type of organism
    (e.g., Gram-negative bacillus) and any vector
    that might be involved in the transmission of the
    pathogen.

30
Infectious Diseases of the Skin
  • General Information Terms relating to skin and
    infectious diseases of the skin
  • -Epidermis -Dermis
  • -Dermatitis -Sebaceous glands
  • -Folliculitis -Sty (also spelled stye)
  • -Carbuncle -Furuncle (boil)

31
Infectious Diseases of the Skin
32
Viral Infections of the Skin
  • Smallpox
  • 2 strains of variola virus, variola minor and
    variola major, DNA virus
  • Warts
  • At least 70 different types of human
    papillomaviruses (HPV), DNA viruses
  • Chickenpox and Shingles
  • Varicella-zoster virus (a DNA virus which is also
    known as herpesvirus 3)
  • German Measles, Rubella
  • Rubella virus, RNA virus
  • Measles, Hard Measles, Rubeola
  • Measles (rubeola) virus, RNA virus
  • Monkeypox
  • Monkeypox virus, DNA virus

33
Bacterial Infections of the Skin
  • Acne
  • Propionibacterium acnes and other
    Propionibacterium spp., anaerobic G bacilli
  • Anthrax, Woolsorters Disease
  • Bacillus anthracis, spore-forming, G bacillus
  • Gas Gangrene, Myonecrosis
  • Anaerobic bacteria in the genus Clostridium,
    especially C. perfringens
  • Leprosy, Hansen or Hansens Disease
  • Mycobacterium leprae, acid-fast bacillus
  • Staphylococcal Skin Infections Folliculitis,
    Furuncles, Abscesses, etc.
  • Staphylococcus aureus, G coccus
  • Streptococcal Skin Infections Scarlet Fever,
    Erysipelas, etc.
  • Streptococcus pyogenes, G coccus

34
Bacterial Infections of the Skin (cont.)
  • Wound Infections
  • Result when protective skin barrier is broken as
    a result of burns, punctures, surgical procedures
    or bites.
  • Opportunistic indigenous microflora and
    environmental bacteria can invade and cause local
    or deep tissue infections.
  • Pathogens may spread through blood or lymph,
    causing serious systemic infections.

35
Fungal Infections of the Skin
  • Dermatophytosis, Tinea (Ringworm) Infections,
    Dermatomycosis
  • Caused by various species of filamentous fungi,
    including Microsporum, Epidermophyton, and
    Trichophyton spp.
  • These fungi are collectively referred to as
    dermatophytes.

36
Infectious Diseases of the Ears
  • General Information
  • Three pathways for pathogens to enter the ear
  • Via the eustachian (auditory) tube, from the
    throat and nasopharynx
  • Via the external ear canal
  • Via the blood or lymph
  • Otitis media infection of the middle ear
  • Otitis externa infection of the outer ear canal

37
Viral and Bacterial Ear Infections
  • Otitis Externa, External Otitis, Ear Canal
    Infection, Swimmers Ear
  • Escherichia coli, Pseudomonas aeruginosa, Proteus
    vulgaris, Staphylococcus aureus rarely caused by
    a fungus such as Aspergillus.
  • Otitis Media, Middle Ear Infections
  • Bacterial causes Streptococcus pneumoniae, G
    diplococcus Haemophilus influenzae, G- bacillus
    and Moraxella catarrhalis, G- diplococcus.
  • Viral causes measles, parainfluenza and
    respiratory syncytial viruses (RSV).

38
Infectious Diseases of the Eyes
  • General Information
  • Important terms relating to the eye and
    infectious diseases of the eye conjunctiva,
    conjunctivitis, keratitis, keratoconjunctivitis.
  • Viral Infections of the Eyes
  • Adenoviruses, enteroviruses, and herpes simplex
    viruses can cause conjunctivitis, keratitis, and
    keratoconjunctivitis.
  • Individuals with viral infections (e.g, cold
    sores) should wash their hands thoroughly.

39
Bacterial Infections of the Eyes
  • Bacterial Conjunctivitis, Pinkeye
  • Haemophilus influenzae biogroup aegyptius and
    Streptococcus pneumoniae are the most common
    causes.
  • Chlamydial Conjunctivitis, Inclusion
    Conjunctivitis, Paratrachoma
  • Certain serotypes (serovars) of Chlamydia
    trachomatis
  • Trachoma, Chlamydia Keratoconjunctivitis
  • Certain serotypes of Chlamydia trachomatis
  • Gonococcal Conjunctivitis, Gonorrheal Ophthalmia
    Neonatorum
  • Neisseria gonorrhoeae G- diplococci also called
    gonococcus or GC

40
Infectious Diseases of the Respiratory System
  • General Information
  • Respiratory system can be divided into
  • upper respiratory tract (URT) paranasal
    sinuses, nasopharynx, oropharynx, epiglottis, and
    larynx.
  • lower respiratory tract (LRT) trachea,
    bronchial tubes, and alveoli of the lungs.
  • Microflora of URT may cause opportunistic
    infections of the respiratory system.
  • LRT infections are the most common cause of death
    from infectious diseases.

41
Infectious Diseases of the Respiratory System
(cont.)
  • Terms relating to infectious diseases of the
    respiratory system
  • Bronchitis Bronchopneumonia
  • Epiglottitis Laryngitis
  • Pharyngitis Pneumonia
  • Sinusitis

42
Viral Infections of the Upper Respiratory Tract
  • The Common Cold, Acute Viral Rhinitis, Acute
    Coryza
  • Many different viruses cause colds.
  • Rhinoviruses (more than 100 serotypes) are the
    major causes in adults.
  • Other cold-causing viruses include coronaviruses,
    parinfluenza viruses, RSV, influenza viruses,
    adenoviruses, and enteroviruses.
  • Transmission occurs via respiratory secretions by
    way of hands and fomites.

43
Bacterial Infections of the Upper Respiratory
Tract
  • Diphtheria
  • Corynebacterium diphtheriae pleomorophic, G
    bacillus.
  • Transmission occurs via airborne droplets, direct
    contact, contaminated fomites and raw milk.
  • Streptococcal Pharyngitis, Strep Throat
  • Streptococcus pyogenes beta-hemolytic,
    catalase-negative, G cocci in chains.
  • Transmission is human-to-human by direct contact,
    usually hands also via aerosol droplets.

44
Infections of the Lower Respiratory Tract Having
Multiple Causes
  • Pneumonia
  • May be caused by G or G- bacteria, mycoplasmas,
    chlamydias, viruses, fungi, or protozoa.
  • Community-acquired bacterial pneumonia is most
    frequently caused by Streptococcus pneumoniae.
  • S. pneumoniae is the most common cause of
    pneumonia in the world.
  • Transmission, in most cases, occurs via infected
    humans.

45
Gram-positive Streptococcus pneumoniae in a
Gram-stained smear of a purulent sputum. Note the
diplococci.
46
Viral Infections of the Lower Respiratory Tract
  • Acute, Febrile, Viral Respiratory Disease
  • Parainfluenza viruses, respiratory syncytial
    virus (RSV), adenovirus, rhinoviruses, certain
    coronaviruses, coxsackieviruses, and echoviruses
    transmission occurs via direct oral contact or by
    droplets.
  • Avian Influenza (Bird Flu)
  • Avian influenza viruses, 3 prominent subtypes
    H5, H7, H9 transmission via infected wild and
    domesticated birds.
  • Hantavirus Pulmonary Syndrome (HPS)
  • At least 5 different hantaviruses (Sin Nombre,
    Bayou, Black Creek Canal, New York-1
    Monongahela) transmission occurs via inhalation
    of aerosolized rodent feces, urine, and saliva.

47
Viral Infections of the Lower Respiratory Tract
(cont.)
  • Influenza, Flu
  • Influenza viruses, types A, B, and C, RNA
    viruses transmission is via infected humans
    pigs and birds also serve as reservoirs.
  • Severe Acute Respiratory Syndrome (SARS).
  • SARS-associated coronavirus (SARS-CoV)
  • Transmission occurs via infected individuals by
    respiratory droplets, or by touching the mouth,
    nose, or eye after touching a contaminated
    surface or object.

48
Bacterial Infections of the Lower Respiratory
Tract
  • Legionellosis, Legionnaires Disease, Pontiac
    Fever
  • Legionella pneumophila, poorly staining, G-
    bacillus transmission is via environmental water
    sources ponds, air-conditioning systems, hot
    tubs, etc.
  • Mycoplasmal Pneumonia, Primary Atypical Pneumonia
  • Mycoplasma pneumoniae, tiny, G- bacteria, lacking
    cell walls transmission occurs via droplet
    inhalation, direct contact with an infected
    person or contaminated articles.

49
Bacterial Infections of the Lower Respiratory
Tract (cont.)
  • Tuberculosis, TB
  • Primarily Mycobacterium tuberculosis (a
    slow-growing, acid-fast, Gram-positive to
    Gram-variable bacillus), occasionally other
    Mycobacterium spp. transmission occurs primarily
    via infected humans (airborne droplets).
  • Whooping Cough, Pertussis
  • Bordetella pertussis, a small, encapsulated,
    nonmotile, G- coccobacillus that produces
    endotoxin and exotoxins transmission occurs via
    infected humans (i.e., droplets by coughing).

50
Fungal Infections of the Lower Respiratory Tract
  • Coccidioidomycosis
  • Coccidioides immitis, a dimorphic fungus
    transmission occurs via inhalation of
    arthrospores.
  • Cryptococcosis
  • 2 subspecies of Cryptococcus neoformans, an
    encapsulated yeast transmission occurs via
    inhalation of yeasts.
  • Histoplasmosis
  • Histoplasma capsulatum var. capsulatum, dimorphic
    fungus transmission occurs via inhalation of
    conidia from soil.

51
Fungal Infections of the Lower Respiratory Tract
(cont.)
  • Pneumocystis Pneumonia (PCP), Interstitial
    Plasma-Cell Pneumonia
  • Pneumocystis jiroveci, has both protozoal and
    fungal properties.
  • Was classified as a protozoan, now classified as
    a fungus.
  • Mode of transmission is unknown perhaps direct
    contact, transfer of pulmonary secretions from
    infected to susceptible persons or perhaps
    airborne.

52
Infectious Diseases of the Oral Region
  • General Information
  • The oral cavity is a complex ecosystem, suitable
    for growth of many types of microorganisms.
  • The microflora of the mouth varies from one
    person to the next about 300 identified species
    of bacteria, both aerobes and anaerobes.
  • Viral Infections of the Oral Region
  • Cold Sores, Fever Blisters, Herpes labialis
  • Usually caused by herpes simplex virus type 1
    (HSV 1), but also herpes simplex type 2 (HSV 2).

53
Bacterial Infections of the Oral Cavity
  • Terms relating to infectious diseases of the oral
    cavity dental caries, gingivitis, periodontitis.
  • Acute Necrotizing Ulcerative Gingivitis (ANUG),
    Vincents Angina, Trench Mouth
  • A synergistic infection involving 2 or more
    species of anaerobic bacteria of the indigenous
    oral microflora most commonly, Fusobacterium
    nucleatum and Treponema vincentii.

54
Fungal Infections of the Oral Cavity
  • Thrush
  • A yeast infection of the oral cavity.
  • Common in infants, elderly patients, and
    immunosuppressed individuals.
  • White, creamy patches occur on the tongue, mucous
    membranes and the corner of the mouth.
  • Caused by Candida albicans and related species.

55
Infectious Diseases of the Gastrointestinal (GI)
Tract
  • General Information
  • Transient and resident microbes continuously
    enter and leave the GI tract.
  • Most microorganisms are destroyed in the stomach
    and duodenum.
  • Terms relating to infectious diseases of the GI
    tract colitis, diarrhea, dysentery, enteritis,
    gastritis, gastroenteritis and hepatitis.
  • Infections of the GI Tract Having Multiple Causes
  • Diarrhea can have many causes (e.g., foods,
    drugs, viruses, bacteria, protozoa or helminths).

56
Viral Infections of the GI Tract
  • Viral Gastroenteritis, Viral Enteritis, Viral
    Diarrhea
  • The most common viruses infecting children in
    their first years of life are enteric
    adenoviruses, astroviruses, caliciviruses and
    rotaviruses.
  • Viruses infecting children and adults include
    Norwalk virus, certain Norwalk-like viruses and
    rotaviruses.
  • Transmission occurs via infected humans, most
    often by way of the fecal-oral route possibly
    from contaminated water and shellfish.

57
Most Common Types of Viral Hepatitis
  • Type C Hepatitis HCV Infection Non-A Non-B
    Hepatitis
  • Hepatitis C virus HCV, enveloped, linear ssRNA
  • Primarily parenterally transmitted rarely
    sexually.
  • Type D Hepatitis HDV Infection Delta Hepatitis
  • Hepatitis D virus HDV delta virus, enveloped,
    circular ssRNA viral satellite.
  • Exposure to infected blood and body fluids, etc.
  • Type A Hepatitis HAV Infection Infectious
    Hepatitis Epidemic Hepatitis
  • Hepatitis A virus HAV linear ssRNA virus.
  • Fecal-oral transmission.
  • Type B Hepatitis HBV Infection Serum Hepatitis
  • Hepatitis B virus HBV, enveloped, circular dsDNA
    virus.
  • Sexual transmission or household contact with an
    infected person.

58
Most Common Types of Viral Hepatitis (cont.)
  • Type E Hepatitis
  • Hepatitis E virus HEV, nonenveloped, ssRNA
    virus.
  • Fecal-oral transmission primarily fecally
    contaminated drinking water also
    person-to-person.
  • Type G Hepatitis
  • Hepatitis G virus HGV, a linear ssRNA virus.
  • Parenteral transmission.

59
Bacterial Infections of the GI Tract
  • Bacterial Gastritis and Ulcers
  • Helicobacter pylori, a curved, microaerophilic,
    capnophilic, G- bacillus.
  • Transmission occurs via infected humans probably
    by ingestion presumed to be either oral-oral or
    fecal-oral.
  • Campylobacter Enteritis
  • Campylobacter jejuni (less common C. coli),
    curved, S-shaped or spiral G- bacillus.
  • Transmission occurs via animals, including
    poultry, cattle, sheep, swine, rodents, birds,
    kittens, puppies and other pets.

60
Bacterial Infections of the GI Tract (cont.)
  • Cholera
  • Certain biotypes of Vibrio cholerae serogroup 01,
    curved, G- bacillus that secretes enterotoxin.
  • Transmission occurs via infected humans and
    aquatic reservoirs fecal-oral route.
  • Salmonellosis
  • Members of the family Enterobacteriaceae, G-
    bacilli that invade intestinal cells, release
    endotoxin and produce cytotoxins and
    enterotoxins.
  • Transmission occurs via domestic and wild
    animals contaminated food, fecal-oral, food
    handlers, contaminated water.

61
Bacterial Infections of the GI Tract (cont.)
  • Typhoid Fever, Enteric Fever
  • Salmonella typhi, G- bacillus that releases
    endotoxin and produce exotoxins.
  • Transmission occurs via infected humans for
    typhoid and paratyphoid some people become
    carriers after infection (e.g., Typhoid Mary).
  • Shigellosis, Bacillary Dysentery
  • Shigella dysenteriae, S. flexneri, S. boydii and
    S. sonnei nonmotile, G- bacilli, members of the
    family Enterobacteriaceae.
  • Transmission occurs via infected humans.

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Enterovirulent Escherichia coli
  • Enterohemorrhagic E. coli (EHEC) Diarrhea
  • Escherichia coli O157H7 most commonly involved
    others include O26H11, O111H8 and O104H21 G-
    bacillus that produces potent cytotoxins.
  • Transmission occurs via cattle feces also
    infected humans, fecal-oral route.
  • Enterotoxigenic E. coli (ETEC) Diarrhea,
    Travelers Diarrhea
  • Many different serotypes of enterotoxigenic E.
    coli.
  • Transmission is via infected humans, fecal-oral
    route.

63
Infectious Diseases of the Genitourinary (GU)
System
  • Urinary Tract Infections (UTIs)
  • UTIs can be divided into upper UTIs (infections
    of the kidneys and ureters) and lower UTIs
    (infections of the bladder, urethra and
    prostate).
  • Terms relating to infectious diseases of the
    urinary tract include cystitis, nephritis,
    ureteritis, urethritis, prostatitis,
    pyelonephritis.

64
Many Gram-negative bacilli and many pink-staining
PMNs can be seen in this Gram-stained urine
sediment from a patient with cystitis.
PMNs
Gram-negative bacilli
65
Infectious diseases of the Genitourinary (GU)
System (cont.)
  • Infections of the Genital Tract
  • Terms relating to infectious diseases of the
    genital tract bartholinitis, cervicitis,
    endometritis, epididymitis, pelvic inflammatory
    disease (PID), vaginitis, vulvovaginitis.
  • Sexually Transmitted Diseases of the Genital
    Tract
  • Sexually transmitted diseases (STDs) includes
    any of the infections transmitted by sexual
    activities.
  • Includes diseases of not only the genital and
    urinary tracts, but other body areas (e.g., skin,
    mucous membranes).

66
Viral STDs
  • Anogenital Herpes Viral Infections, Genital
    Herpes
  • Usually herpes simplex virus, type 2 (HSV-2)
    occasionally HSV-1
  • Transmission occurs via infected humans by direct
    sexual contact oral-genital, oral-anal, or
    anal-genital contact when lesions are present.
  • Genital Warts, Genital Papillomatosis, Condyloma
    Acuminatum
  • Human papillomaviruses (HPV), DNA viruses.
  • Transmission occurs via infected humans by direct
    contact, usually sexual.

67
Bacterial STDs
  • Syphilis
  • Treponema pallidum, Gram-variable, tightly-coiled
    spirochete too thin to be seen by brightfield
    microscopy can be seen by darkfield microscopy.
  • Transmission via infected humans, by direct
    contact with lesions, body secretions, mucous
    membranes, blood, semen, etc. usually sexual
    contact also blood transfusions and
    transplacentally from mother to fetus.
  • Genital Chlamydial Infections, Genital
    Chlamydiasis
  • Certain serotypes of Chlamydia trachomatis,
    obligate intracellular, G- bacteria.
  • Transmission via infected humans, direct sexual
    contact or mother-to-neonate during birth.
  • Gonorrhea
  • Neisseria gonorrhoeae, G- diplococcus.
  • Transmission via infected humans, usually sexual
    contact or direct mucous membrane-to-mucous
    membrane contact.

68
Other Bacterial STDs
  • Bacterial STDs that occur more frequently in
    parts of the world other than the United States
  • Chancroid Haemophilus ducreyi, G- bacterium.
  • Granuloma inguinale Calymmatobacterium
    granulomatis, G- bacterium.
  • Lymphogranuloma venereum certain serotypes of
    Chlamydia trachomatis.
  • STDs may be transmitted simultaneously if a
    patient is diagnosed with one particular type of
    STD, other types should be sought.

69
Infectious Diseases of the Circulatory System
  • The circulatory system consists of the
    cardiovascular system (the heart and various
    vessels) and the lymphatic system (lymphatic
    vessels, lymphoid tissue and lymph).
  • Terms relating to infectious diseases of the
    cardiovascular system include endocarditis,
    myocarditis, pericarditis.
  • Blood is normally sterile.
  • Terms relating to the lymphatic system include
    lymphadenitis, lymphadenopathy, lymphangitis.

70
Viral Infections of the Circulatory System
  • Human Immunodeficiency Virus (HIV) Infection,
    Acquired Immunodeficiency Syndrome (AIDS)
  • Human immunodeficiency virus (HIV), HIV-1 and
    HIV-2, RNA viruses.
  • Transmission occurs via infected humans, by
    direct sexual contact, contaminated
    needles/syringes, transfusion of contaminated
    blood, transplacental transfer from mother to
    child, transplantation of HIV-infected tissues or
    organs, needlestick, scalpel and broken glass
    injuries.

71
Viral Infections of the Circulatory System (cont.)
  • Infectious Mononucleosis, Mono, Kissing
    Disease
  • Epstein-Barr virus (EBV), also known as human
    herpesvirus 4, DNA virus.
  • Transmission occurs via infected humans,
    person-to-person, direct contact with saliva.
  • Mumps, Infectious Parotitis
  • Mumps virus, RNA virus.
  • Transmission occurs via infected humans by
    droplet spread and direct contact with saliva.

72
Viral Hemorrhagic Fevers
  • Viral Hemorrhagic Disease
  • Ebola virus and Marburg virus, filamentous
    viruses.
  • Transmission occurs via infected humans infected
    African green monkeys in Marburg infection.
    Transmission is person-to-person via direct
    contact with infected blood, secretions, internal
    organs or semen also needlestick.

73
Rickettsial and Ehrlichial Diseases of the
Cardiovascular System
  • Rocky Mountain Spotted Fever, Tickborne Typhus
    Fever
  • Rickettsia rickettsii, G- bacterium, obligate
    intracellular pathogen.
  • Transmission occurs via infected ticks on dogs,
    rodents and other animals.
  • Endemic Typhus Fever, Murine Typus Fever,
    Fleaborne Typhus
  • Rickettsia typhi, G- bacterium, obligate
    intracellular pathogen.
  • Transmission occurs via rats, mice, possibly
    other mammals, infected rat fleas.

74
Rickettsial and Ehrlichial Diseases of the
Cardiovascular System (cont.)
  • Epidemic Typhus Fever, Louseborne Typhus
  • Rickettsia prowazekii, G- bacterium, obligate
    intracellular pathogen.
  • Infected humans and body lice.
  • Erlichiosis
  • Gram-negative coccobacilli, closely related to
    rickettsias obligate intraleukocytic pathogens.
  • Reservoir unknown transmission is via tick bite.

75
Bacterial Infections of the Cardiovascular System
  • Lyme Disease, Lyme Borreliosis
  • Borrelia burgdorferi, G-, loosely coiled
    spirochete.
  • Transmission is via tick bite.
  • Plague, Black Death, Bubonic Plague, Pneumonic
    Plague, Septicemic Plague
  • Yersinia pestis, non-motile, bipolar-staining, G-
    coccobacillus.
  • Transmission is via wild rodents and their fleas
    (flea bite).
  • Tularemia, Rabbit Fever
  • Francisella tularensis, pleomophic, G-
    coccobacillus.
  • Transmission is via tick bite associated with
    rabbits.

76
Infectious Diseases of the Central Nervous System
(CNS)
  • General Information
  • The nervous system is composed of the CNS (brain
    and spinal cord and 3 membranes) and the
    peripheral nervous system (nerves that branch
    from the brain and spinal cord).
  • There are no indigenous microflora of the nervous
    system.
  • Terms relating to infectious diseases of the CNS
    include encephalitis, encepahlomyelitis,
    meningitis, meningoencephalitis and myelitis.

77
Infections of the CNS Having Multiple Causes
  • Meningitis inflammation of the meninges
  • Many causes, including the ingestion of poisons,
    ingestion or injection of drugs, reaction to a
    vaccine or a pathogen (i.e., a virus, bacterium,
    fungus or a protozoan).
  • 3 major causes of bacterial meningitis
  • Hemophilus influenzae
  • Neisseria meningitidis
  • Streptococcus pneumoniae.

78
Viral Infections of the CNS
  • Lymphocytic Choriomeningitis
  • Lymphocytic choriomeningitis virus (LCMV).
  • Transmission occurs via exposure to mouse urine,
    droppings, saliva or nesting materials.
  • Poliomyelitis, Polio, Infantile Paralysis
  • Polioviruses, RNA virus
  • Transmission is person-to-person, primarily via
    the fecal-oral route also throat secretions.

79
Viral Infections of the CNS (cont.)
  • Rabies
  • Rabies virus bullet-shaped, enveloped RNA virus.
  • Transmission occurs via the bite of a rabid
    animal (by virus-laden saliva) airborne
    transmission from bats in caves.
  • Viral Encephalitis, Arthropodborne Viral
    Encephalitis
  • (See next slide.)

80
Selected Arthropodborne Viral Encephalitides of
the United States.
81
Bacterial Infections of the CNS
  • Listeriosis
  • Listeria monocytogenes G coccobacillus.
  • Transmission occurs via ingestion of raw or
    contaminated milk, soft cheeses and vegetables.
  • Tetanus, Lockjaw
  • Clostridium tetani, motile, G anaerobic,
    spore-forming bacillus.
  • Transmission occurs via spores of C. tetani
    entering a puncture wound, burn, or needlestick
    by contamination with soil, dust, or feces.
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