Microbiology: Unit I

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Microbiology Unit I

• By Julie E. Davis BSN, RN
• 2008-2009

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Historical Development

• Disease has been around since beginning of
  mankind
• Many theories of disease have developed over the
  centuries

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Demonic Theory

• Attributed disease illness to being possessed
  by devil or demons
• Punishment for sins
• Failure to perform rites
• Failure to provide offerings
• Trepanning or trephination
• Perforation of the skull to relieve pressure on
  the brain
• Used a type of drill bit

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Theory of Four Humors

• Blood- hot wet
• Black bile-cold dry
• Yellow bile- hot dry
• Phlegm- cold wet
• Disease was caused by an imbalance of these
• Treatment was to restore the balance of head/cold
  or dryness/wetness

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Four Humors (cont)

• These concepts are still found today in certain
  cultures around the world
• Asian
• Latin
• Mexican
• Muslim
• Arab
• African
• South American

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Four Humors (cont)

• Cold Excess
• Chest cramps, earaches, paralysis, stomach
  cramps, rheumatism, and TB
• Heat Excess
• Dysentery, abscessed teeth, sore throat, kidney
  ailments, rashes

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Early Microbiology

• Current knowledge of germs is only about 100
  years old
• Ancient Egyptians Chinese believed in bathing
  to prevent disease
• Ancient Egypt used biological warfare
• Used bodies blood of diseased to contaminate
  water supplies of enemies

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Early Microbiology

• Ancient Romans Greeks had sewers hospitals
• Most of the knowledge of public sanitation
  transmission of disease was lost in the Dark
  Ages.
• Renaissance brought epidemics of smallpox,
  syphilis rabies
• Bubonic Plague prompted a search for explanations
  as to how disease was contracted transferred.

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Invention of the Microscope

• Robert Hooke
• Discovered cells with magnifying lens
• Leeuwenhoek
• First scientific use of single lens microscope
• Compound Microscope
• Early 1800s
• Microbiology became new field of study
• Electron Microscope
• Currently used
• 30,000 times more powerful than the first
  microscopes

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Spontaneous Generation

• Living things created themselves from nonliving
  matter
• Prevalent before mid-19th century
• Flies came from rotten food
• Lice came from dirty clothes linen

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Biogenesis

• Is the idea that living cells can only come from
  living cells
• Louis Pasteur
• Proved the theory of biogenesis through idea that
  bacteria must be present for milk to spoil

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Pasteurization

• Pasteurization
• Rapid heating of fluids like milk kills
  disease-causing bacteria
• Pasteurs efforts contributed to the germ
  theory of disease
• He thought life must arise from pre-existing life
• NOT usually given credit for work on germ theory
  of disease

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Aseptic Technique

• Joseph Lister
• Used antiseptic-soaked dressings to kill
  disease-causing microorganisms.
• Significantly reduced wound infections.
• Used antiseptics in surgery
• Sprayed diluted carbonic acid on hands,
  instruments dressings
• Prior to Lister 50 of surgery patients died

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Handwashing

• Semmelweiss
• Performed autopsies delivered babies (w/o
  washing his hands in between)
• High mortality rate for mothers/babies
• Discovered that washing hands w/ chlorinated lime
  drastically decreased number of deaths

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Robert Koch

• Actually credited with germ theory of disease
• The first to conclusively show that bacterium
  caused disease

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Kochs Postulates

• 1. Causative agent must be present in every case
  of disease
• 2. Pathogen must be isolated from host grown in
  STERILE environment
• 3. Same disease must be produced when culture is
  inoculated into healthy, susceptible animal
• 4. Same pathogen must be recoverable again from
  the infected animals

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Other Contributions

• Edward Jenner
• First immunization for small-pox
• Dairy maids exposed to cowpox did not get
  smallpox (vacca is Latin for cow)
• Sir Alexander Fleming
• Discovered the first antibiotic
• PENICILLIN
• Derived from mold

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Binomial Nomenclature

• Refers to all living things using two names
• Genus species
• Genus is first, always capitalized is largest
  of the two groups
• Species is second, lower case, smaller category
• Genus name is often abbreviated with the first
  letter capitalized
• Homo sapien (H. sapien) Escherichia coli (E.
  coli) Staphylococcus aureus (S. aureus)

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Microorganisms

• Tiny living bodies that are visible only w/ a
  microscope
• Characteristics are almost the same as other
  living things
• Microbiology-study of very small living things

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Microorganisms

• Present in environment on body surfaces (skin,
  intestines, mouth, respiratory tract, urinary
  tract reproductive tract)
• We often refer to them as germs most are
  harmless some are helpful

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Types

• Bacteria-most common type of disease causing
• Viruses-smallest cannot survive outside of a
  living host
• Fungi-yeasts/molds
• Parasites-must live on other living organisms
  (protozoa helminths)

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Normal Flora

• Normal Flora-natural population of organisms
  living on or within each of us (Ramont, pg. 150)
• Types
• (AKA)Resident Flora- species that live on or in
  everyone almost all the time (E. coli in the
  intestine)
• Opportunistic Flora-causes disease in a
  susceptible person (weakened immune system)

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Normal Flora (cont)

• Beneficial to us inhibiting the growth of
  pathogens pathogens are disease causing
  microorganisms
• Skin normally has large bacterial population
• Cilia sweep pathogens mucous out of trachea
• Normal vaginal flora maintains acidic pH
  (lactobaccilus) ATB can disrupt this
• Bacteria in colon produce Vitamin K
• Normal flora can be disturbed by taking
  antibiotics

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Examples of Normal Flora

• Skin
• Staph epidermidis
• Propionibacterium acnes
• Staphylococcus aureus
• Coagulase negative staph
• Bacillus species
• Pityrosporum ovale (yeast)

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Examples of Normal Flora

• Nasal Passages, oropharynx mouth
• Coagulase negative staph
• Staphyloccus epidermidis
• Neisseria species
• Haemophilus species
• Streptococcus pneumoniae
• Lactobaccillus

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Examples of Normal Flora

• Intestine
• Lactobacillus
• Streptococcus
• Enterobacteriaceae
• Escherichia coli
• Klebsiella species

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Examples of Normal Flora

• Urethra vagina
• Staphylococcus epidermidis
• Proteus
• Lactobacillus
• Bacteroides
• Clostridium
• Candida albicans

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Examples of Normal Flora

• THE FOLLOWING AREAS SHOULD NOT HAVE
  MICROORGANISMS
• BLOOD LYMPH SYSTEM
• BLADDER, URETER, KIDNEYS
• LUNGS ( BRONCHI)
• STOMACH ESOPHAGUS

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Harmful Actions ofMicroorganisms

• Infection invasion of body by disease causing
  organisms a.k.a. infectious agent or pathogen
• Pathogen- microorganisms that cause disease
• Disease- a detectable change in the way the body
  functions

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Infectious Disease

• Caused by microorganisms or by the products
  (toxins) of microorganisms
• Factors influencing development of infectious
  disease
• Virulence
• Ability of the pathogen to cause disease its
  ability to survive
• Resistance
• Total of bodys defenses against disease

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Infectious Disease (cont)

• Clinical Infection
• Pt is symptomatic (or showing symptoms)
• Symptoms of a common cold
• Subclinical Infection
• Asymptomatic (symptoms are NOT apparent or
  inapparent)
• Gonorrhea in women initial HIV infection
• BLOOD SHOULD BE FREE OF ORGANISMS (STERILE).
  When organisms grow in blood, the pt becomes
  septic. (usually fatal if untreated)

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Communicable Diseases

• Communicability- how easily they can be spread
• Communicable Disease- one that is spread or
  transmitted by direct or indirect contact.
• Vector-something that can carry a disease
  help aid in its transmission (i.e. mosquito, tick)

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Communicable Diseases

• Some communicable diseases are spread by vectors
  (i.e. West Nile virus)
• Some are airborne (i.e. tuberculosis)
• Microorganisms often develop a resistance to
  antibiotics (i.e. MRSA)
• World Health Organization
• Center of Disease Control

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Infectious Disease (cont)

• Incubation Period
• Time allowed before symptoms appear once a
  pathogen has established itself in a host
  (infecting agent is present, but no symptoms have
  appeared yet)
• Prodromal Period
• Short time after incubation period when vague,
  non-specific symptoms may begin
• Ex Herpes outbreaks-often preceded by tingling
  itching at the site prior to the appearance of
  blisters
• Invasion Period
• Specific symptoms of the illness appear
• Ex high fever, rash, swollen lymph nodes,
  cough, diarrhea, or the gradual paralysis that
  occurs with botulism

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Infectious Diseases (cont)

• Acme-height or worst of the disease
• Self-limiting diseases-typically last a certain
  length of time then they resolve
• Common cold
• Chicken pox
• Mumps

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Infectious Diseases (cont)

• Etiology the cause
• Idiopathic undetermined cause
• Primary infection the original outbreak of an
  infection the original illness
• Secondary infectiona new infection superimposed
  on a pre-existing infection

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Types of Infection

• Localized-pathogen in one area of the body
• Systemic-pathogen spread throughout the body by
  blood or lymph
• Septicemia (Bacteremia)-bacteria in the blood
• Acute-usually severe or of abrupt onset
• Chronic-progresses slowly or is prolonged
• Secondary-made possible by a primary infection
  that lowered resistance
• Nosocomial hospital acquired infection
• Endogenous-caused by the persons own normal
  flora in an abnormal site

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Example

• Types of infection can be combined
• Acute Systemic
• Chronic localized inflammation

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Examples of Nosocomial Infections

• Urinary Tract Infections (UTI)
• Caused by E. coli, enterococcus or pseudomonas
  species
• Due to poor catheterization technique,
  contamination of closed drainage system or
  inadequate handwashing
• Surgical sites
• Caused by staph, pseudomonas, or enterococcus
• Due to poor handwashing, poor dressing change
  technique environmental contamination

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Examples of Nosocomial Infections

• Bloodstream
• Caused by staph enterococcus species
• Due to inadequate handwashing, improper IV
  therapy, technique site care
• Pneumonia
• Caused by staph, pseudomonas, enterobacter
• Due to poor handwashing, improper suctioning
  positioning, or lack of respiratory care after
  anesthesia

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Epidemiology

• Study of patterns spread of disease within a
  population
• Epidemic-outbreak of disease
• Endemic-present within a population, with an
  expected usual of cases (ex flu)
• Pandemic epidemic that has spread throughout
  several countries

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Chain of Infection

• Portal of Entry
• The way a pathogen enters a host
• Through any body opening
• Can cross the placenta to fetus
• Ex nose, reproductive tract, mouth
• UNBROKEN skin is NOT a portal of entry.
• Portal of Exit
• The way a pathogen leaves a host

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Spread of Infection (cont)

• Reservoirs-persons with the disease, carriers
  after recovery, or animal hosts (typhoid Mary)
• Zoonoses-really animal diseases that people
  acquire in certain circumstances (rabies)
• Noncommunicable cannot be directly or indirectly
  transmitted from host to host (diabetes)

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Communicable Diseases

• May be transmitted directly from host to host by
• Respiratory droplets
• Cutaneous
• Sexual contact
• Placental transmission
• Blood contact
• Also by food, water, vectors, or fomites
• A vector is an organism such as a mosquito, tick,
  or flea that spreads disease to other organisms
• A fomite is an inanimate object that carry the
  pathogen (ex doorknob, water fountain)

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Chain of Infection

• Infectious Agent-microorganism causing disease
• Reservoir-infected patient (or a place where
  organisms can pool reproduce)
• Exit Route (from reservoir)-secretions (feces,
  blood, urine, sputum)
• Method of Transmission-hands, contaminated food,
  supplies or objects, droplet
• Entrance-mouth, break in skin, or mucous
  membranes
• Susceptibility of the Host-susceptible
  person/compromised host
• MOST EFFECTIVE WAY TO BREAK THE CHAIN OF
  INFECTION IS TO WASH YOUR HANDS.
  

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Contagious Diseases

• Are communicable diseases that are EASILY spread
  from person to person by CASUAL cutaneous contact
  or respiratory droplets
• All communicable diseases are NOT contagious,
  but all contagious diseases ARE communicable.
• EX. AIDS is NOT contagious but it is
  communicable
• Rememberthe best prevention of the spread of
  disease is good HANDWASHING. Good handwashing
  technique includes running water, soap friction.

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Relating Microbiology to the Nursing Process

• Assessment-examining pt., collecting data (ex
  removing a dressing to look at drainage)
• Diagnosis-formulated by nurse according to actual
  potential problems
• Planning-how will you care for pt.
• Intervention-putting your plan in action (ex
  cleaning wound, frequent dressing changes,
  medicating)
• Evaluation-determine if plans interventions
  have been effective (has infection improved?)

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Other Risk Factors for Disease

• Genetic predisposition
• Age (Very young elderly)
• Lifestyle (Smoking, alcoholism)
• Stress
• Environmental Factors (climate or injury)
• Pre-existing conditions (diabetes)
• Malnutrition
• Altered defense mechanisms (low WBC), chronic
  illness, immunosuppressive therapy, use of ATBs
  or steroids)

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Cultural Considerations

• Native Americans, Vietnamese refugees
  Mexican-Americans have higher incidence of TB
  Hep. B
• Africans w/ sickle cell trait have increased
  immunity to malaria
• In America, racial/ethnic minorities suffer
  higher rate if HIV infections

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Supplemental Reading

• Ramont, R. Niedringhaus, D. (2008). Fundamental
  nursing care. (2nd Ed.). Upper Saddle River, New
  Jersey Pearson Prentice Hall.
• Chapter 9, pp. 150-154.