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

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Microbiology for the Health SciencesChapter
14.Pathogenesis of Infectious Diseases
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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)

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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.

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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.

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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.

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Four Periods or Phases in the Course of an
Infectious Disease

• The incubation period
• The prodromal period
• The period of illness
• The convalescent period

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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.

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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.

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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.

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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.

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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).

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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).

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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.

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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.

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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.

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Virulence Factors
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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.

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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.

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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).
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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

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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.

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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.

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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.

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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.

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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.

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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.

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Microbiology for the Health SciencesChapter
17.Major Viral, Bacterial,and Fungal Diseases
of Humans
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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

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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.

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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)

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Infectious Diseases of the Skin
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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

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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

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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.

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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.

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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

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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).

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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.

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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

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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.

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Infectious Diseases of the Respiratory System
(cont.)

• Terms relating to infectious diseases of the
  respiratory system
• Bronchitis Bronchopneumonia
• Epiglottitis Laryngitis
• Pharyngitis Pneumonia
• Sinusitis

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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.

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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.

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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.

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Gram-positive Streptococcus pneumoniae in a
Gram-stained smear of a purulent sputum. Note the
diplococci.
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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.

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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.

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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.

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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).

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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.

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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.

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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).

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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.

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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.

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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).

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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.

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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.

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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.

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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.

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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.

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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.

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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).

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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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.)

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Selected Arthropodborne Viral Encephalitides of
the United States.
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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.