Unit F: Infectious Diseases
Competency BT06.00:
Objective
Analyze issues of public health, infectious diseases, and bioterrorism.
BT06.01:
Discuss the infectious disease process.
Review of Microorganisms or Microbes
A. Microbes –
1.small living organisms
a. not visible to the naked eye
b. must be viewed under a microscope
2. Found everywhere in the environment, including the human body. On it and in it.
3. Many microorganisms are part of the bodies’ normal body flora
a. Beneficial in maintaining certain body processes
b. Called non-pathogens
4. Other microbes cause disease and infection and called pathogens or germs
5. Microbes that are beneficial in one body system can be pathogenic in another body system
a. Escherichia Coli ( E Coli) bacteria is part of the natural flora of the large intestine
b. If E Coli enters the urinary tract it causes an infection
B. Classes of Microbes
1. Bacteria
a. simple one-celled organism that multiplies rapidly
b. Classified by shape and arrangement
1. Cocci – round or spherical. Micrococci ( small and circular or diplococcic(present in
pairs)
a. Diplococci causes diseases such as gonorrhea, meningitis, pneumonia
b. Streptococci presents in chains. Causes severe sore throat (Strep)
c. Staphylococci presents in clusters or groups. Is a pus producing bacteria.
Causes infections such as boils, wound infections and toxic shock
2. Bacilli are rod shaped and occur as one in pairs or chains
a. Many contain flagella which are small threadlike projections allowing the
organism to move
b. Have the ability to form spores which are thick walled capsules and extremely
difficult to kill in this form.
c. Causes TB, Tetanus, Pertussis(Whooping Cough), Botulism, Diphtheria and
Typhoid
3. Spirilla are spiral or corkscrew shape
a. Causes Syphilis and Cholera
4. Antibiotics are used to kill bacteria
a. Some strains of bacteria have become antibiotic resistant (antibiotic no longer
effective
2. Protozoa – one celled animal like organism that have Flagella for movement
a. Often found in decayed materials and contaminated water
b. some are pathogenic and cause Malaria, Amebic Dysentery, Trichomoniasis and African
Sleeping Disease
3.Fungi – simple plant like organism that lives on dead organic matter
a. Yeasts and Mold are 2 common forms of fungi that can be pathogenic
b. Causes diseases like Ringworm, Athletes Foot, Histoplasmosis, Yeast Vaginitis and Thrush
c. Antibiotics do not kill fungi
d. Anti-fungal medications are prescribed but are expensive, must be taken for a long period of
time and may cause liver damage
4. Rickettsiae – these are parasitic microorganisms that cannot live outside the cells of another
organism
a. Commonly found in fleas, lice, ticks, mites and transmitted to humans via bites from these
insects
b. Causes Typhus Fever and Rocky Mountain Spotted Fever
c. Antibiotics are effective against Rickettsiae
5. Viruses – the smallest microorganism only visible with an electron microscope
a. requires host to reproduce
b. spread from human to human by blood and body secretions
c. very difficult to kill. Antibiotics are not effective and are Resistant to many disinfectants
d. Causes the common cold, measles, mumps, chicken pox, herpes, warts, influenza and polio
C. Diseases of Major Concern to Health Care Providers
1. Hepatitis B or serum hepatitis – caused by HBV virus and transmitted through blood and body
secretions
a. Can lead to scarring and destruction of liver cells
b. Vaccine available – involves a series a 3 injections and must be offered free of charge to
employees
2. Hepatitis C – caused by the Hepatitis C virus or HCV and damages the liver
a. Transmitted by blood and body fluids containing blood
b. Many with the disease are asymptomatic or have mild symptoms that resemble the flu
c. Both HBV and HCV are extremely difficult to destroy and may remain active for several days
in dried blood
3. Acquired Immune Deficiency Syndrome (AIDS)
a. Caused by HIV (human immunodeficiency virus) and suppresses the immune system
b. Infected Individual prone to opportunistic infections
c. No cure No Vaccine Medications prescribed to treat symptoms
D. Conditions Required for Growth
1. Bacteria require a warm, dark, moist place to grow and reproduce and need a source of
2. The human body is an excellent medium for bacterial growth. The human body is moist and warm.
Some bacteria are killed quickly by light.
3. Oxygen Need
a. aerobic – requires O2
b. anaerobic – does not require O2
E. Types of Infection
1. Endogenous – infection originated within the body. E.g. metabolic disorders, congenital
abnormalities, tumors, and infections caused by microorganisms w/in the body
2. Exogenous – infection or disease originates outside the body. E.g. pathogenic organisms that invade
the body, radiation, chemical agents, trauma, electric shock, and temperature extremes.
3. Nosocomial Infection – hospital acquired infection. Usually transmitted by healthcare provider to
patient. Many of these pathogens are antibiotic resistant and are serious or life threatening.
a. Common Examples:
1. Staphylococcus
2. Pseudomonas
3. Enterococci
4. Opportunistic Infection – infections that occur when the bodies’ defenses are weak
a. These diseases do not usually present in people with intact immune systems
b. Examples
1. Kaposi’s Sarcoma – a rare form of cancer
2.Pneumocystis Carinii - a form pneumonia
F. Chain of Infection – conditions that exist for disease to occur and spread from one individual to another
1. Causative Agent – pathogen (bacterial or viral) that causes a disease
2. Reservoir- Place where causative agent can live
a. Common Reservoirs
1. Human Body
2. Animals
3. Environment
4. Fomites – objects contaminated with infectious material that contain pathogens e.g.
doorknobs, bedpans, urinals, linens, instruments, specimen containers
3. Portal of Exit - way for causative agent to escape from the reservoir
a. Pathogens can leave the body through urine, feces, saliva, blood, tears, mucous discharge, sexual secretions
and draining wounds
4. Mode of Transmission – the way the causative agent can be transmitted to another reservoir or host where
it can live through direct or indirect contact
a. Direct Contact –
1. person to person, spread by physical or sexual contact
2. contact with body secretions containing pathogen
3. contaminated hands are one of the most common sources of direct transmission
b. Indirect Contact
1. pathogen is transmitted from contaminated substances such as food, air, soil, insects, feces,
clothing, instruments, equipment
2. touching contaminated equipment and spreading the pathogens on the hands
3. breathing in droplets carrying airborne infections
4. getting bitten by an insect carrying the pathogen
5. Portal of Entry – the way the causative agent enters a new reservoir or host
a. Different portals of entry
1. Breaks in the skin of mucous membrane
2. Respiratory Tract
3. Digestive Tract
4. Genitourinary Tract
5. Circulatory System
6. Susceptible Host – an individual who can contract the disease
a. The human body can fight off causative agents and not contract a disease if their defense
mechanisms are intact and their immune system is strong
b. Body Defenses
1. Mucous Membranes – line the respiratory tract, digestive tract and reproductive tract
and trap pathogens
2. Cilia – tiny hair-like structures that line the respiratory tract to propel pathogens out
of the body
3. Coughing and sneezing
4. Hydrochloric acid – destroys pathogens in the stomach
5. Tears contain bactericidal chemicals
6. Fever
7. Inflammation – leukocytes or WBC’s destroy pathogens
8. Immune response – body produces antibodies/ protective proteins that combat
pathogens
c. Humans become susceptible host when
1. large numbers of pathogens attack the body
2. the bodies’ defenses are compromised or weak
7. Health care workers must be aware of the parts in the chain of infection because if any part of the
chain can be eliminated, then the spread of the disease or infection can be stopped
G. Aseptic Techniques – directed toward maintaining cleanliness and eliminating or preventing contamination
1. Common aseptic techniques
a. Handwashing
b. Good personal hygiene
c. using disposable gloves when in contact with body secretions or contaminated objects
d. Proper cleaning of instruments and equipment
e. Thorough cleaning of the environment
2. Levels of aseptic control
a. Antisepsis – preventing or inhibiting the growth of pathogenic organisms
1. not usually effective against spores or viruses
2. can be used on the skin e.g. alcohol, betadine
b. Disinfection – process that destroys or kills pathogenic organisms
1. not always effective against spores and viruses
2. chemicals are used
3. used mainly on objects and not people as they can irritate or damage skin
c. Sterilization – process that destroys all microorganisms both pathogenic and non-pathogenic
1. Includes spores and viruses
2. Steam under pressure, gas, radiation and chemicals can be used to sterilize objects
3. Methods of aseptic control
a. Ultrasonic
1. sound waves are used to clean instruments
2. not a method of sterilization only removes dirt and residue
3. does not kill spores or viruses
b. Chemical Disinfection
1. very few chemicals effective against spores or viruses but instruments must be
submerged in chemical for 10+ hours
2. Common solutions are 90% isopropyl alcohol, formaldehyde alcohol, 10% bleach
solution, Lysol
c. Autoclave – equipment that uses steam under pressure, gas, or dry heat to sterilize
instruments and supplies
1. items must be clean thoroughly and free of residue
2. kills all microorganisms
3. instruments and supplies must be wrapped prior to autoclaving to maintain sterility
4. Wrapped items are sterile for 30 days if wrapped tightly, kept dry and stored
correctly.
Competency BT06.00:
Analyze issues of public health, infectious diseases, and bioterrorism.
Objective
Discuss the infectious disease process.
BT06.01:
A. Nature of infectious diseases
1. Pathogens-microorganisms that is capable of causing disease
2. Infection-results when a pathogen invades and begins growing within the host
3. Disease-results only if and when tissue function is impaired (i.e. burns, skin lesions)
4. The body has defense mechanisms to prevent infection
5. In order to cause disease, pathogens must be able to enter, adhere, invade, colonize, and inflict
damage
6. Entrance to the host-mouth, eyes, genital openings, wounds
7.Growth of pathogens or the production of toxins/enzymes cause disease
8.Some normal flora prevent diseases
B. Microbes that cause infectious diseases
1. Bacteria-Salmonella Typhi, Staphylococcus Aureus
a. aerobic vs. anaerobic
b. gram negative vs. gram positive
c. any form – bacillus, coccus, or spirillum
2. Viruses-apart from the host cell, have no metabolism and cannot reproduce
a. Retroviruses – cause HIV and certain types of cancer
b.Herpes virus – chickenpox, cold sores, smallpox
c.Rhino virus – common cold, many mutations
d.Myxoviruses – influenza, meales
e. Rotaviuses- gastroenteritis
3. Fungi-form spores
a. E.g. Ringworm & Histoplasmosis
b.Yeasts of Candida are opportunistic
c. Antibiotics reduce normal flora allowing yeast to grow
4. Protozoa-acquired through contaminated food or water, or bite of an arthropod (mosquito)
a. Diarrheal disease in the US – Giardia Lammblia
b.Malaria – Plasmodium occurs in the Tropics
5. Helminths-simple, invertebrate animals, some infectious parasites – symptoms: abd. pain and
diarrhea
a.Swimmer’s Itch in US –flatworm, Schistosoma
b. Trichnella Spiralis- roundworm ingested in undercooked pork from infected pigs causes
respiratory paralysis which leads to death
6. Prions-Creutzfeldt-Jakob disease neurodegenerative disorder. Abnormal proteins attack the brain.
Spongey appearance observed during autopsy
C. Occurrence of infectious diseases
1. Epidemiology –study of the occurrence of disease in populations
2. Disease reservoirs-where the infectious agent survives (humans, rodents) Example = Yersinia Pestis
3. Modes of transmission
a. Direct contact occurs when one is infected by contact with the reservoir, inhaling infectious
droplets.
1. Examples: AIDS, rabies, malaria, influenza, ringworm, trichninosis
b. Indirect Contact – the pathogen is transmitted from contaminated substances such as food,
soil, water (Hepatitis A) clothing, equipment(Tetanus)
c.Horizontal vs. Vertical Transmission
1. horizontal transmission is the transmission of a bacteria, fungus, or virus between
members of the same species that are not mother and child
2. vertical transmission is the transmission of a bacterial or viral infection directly from
the mother to the embryo, fetus or baby during pregnancy or childbirth. Transmission
can occur across the placenta and in breast milk. Example: HIV is a vertically
transmitted pathogen aka perinatal transmission.
D. Host defenses against infectious diseases
1. Nonspecific mechanisms are the body’s primary defense against disease-anatomical barriers,
physiological deterrents and presence of normal flora (skin, low pH and high alkalinity)
a. Anatomical barriers – nasal opening, skull, vertebral column, skin
b.Physiological deterrents - tears, vaginal secretions, saliva, blood, sweat
c. Normal flora successfully compete with pathogens
2. Specific mechanisms-immunity
a.T lymphocyte cells
b. Antibody production
3. Vaccination-produces immunity
Competency BT06.00:
Objective
Analyze issues of public health, infectious diseases, and bioterrorism.
BT06.02:
Analyze the role of public health in the prevention of infectious diseases.
A. Public health measures toward prevention
1. Safe water-US water is purified through settling, filtration, and chlorination
a.Private wells must follow certain guidelines
b. Municipal water is usually tested
2. Sewage treatment and disposal is mandated by US government
3. Food safety-US has many standards, inspection plans and regulations dealing food
preparation, handling, and distribution
a.Milk is pasteurized,dated and analyzed periodly
b. Restaurants, meat packing plants, supermarkets are inspected regu;arly
4. Animal control programs-Domestic herds are inspected, rabid animals are destroyed, rat control
programs in place in urban areas
5. Vaccination programs mandate that children be vaccinated prior to school
6. Pesticides to block vector-borne disease – those carried by mosquitoes
B. Public health organizations enforce regulation, provide public health services
1. National Institutes of Health (NIH)-supports health-related research
2. Centers for Disease Control (CDC)-investigates disease outbreaks, publishes reports, sponsors
education/ research, reference labs
3. Food and Drug Administration (FDA)-monitors safety of food, medicines and other products
4. World Health Organization (WHO)-provides international surveillance and control of disease
C. Benefits of public health research
1. New research techniques-rapid identification
2. HIV protease inhibitors
3. Vaccine research
4. Identification of better preventative measures
Objective
BT06.03: Investigate the treatment of infectious diseases.
A.Drugs used to treatment of bacterial diseases can be grouped into
categories based on their modes of action
1. Penicillins/cephalosporins interfere with certain layers of cell wall
2. Chloramphenicol, tetracyclines, erythromycins-may be toxic when
used in high doses or prolonged periods of time
3. Rifampin-used for treatment of TB
B. Drugs that effectively inhibit viral infections are highly toxic to host cells because viruses use the host’s
metabolic enzymes in reproduction
1. Antiviral drugs target virus-specific enzymes
2. Acyclovir-used in treatment of genital herpes
3. Amantadine-used to prevent or moderate influenza
4. AZT-inhibit replication of HIV genome
C. Development of drugs used to treat fungal, protozoan, and helminthic diseases are also highly toxic to
mammals
1. Azole derivatives inhibit sterol synthesis
2. Amphotericin B-disrupts cell membrane
D. Antimicrobial resistance presents ongoing problems in the fight against infectious diseases
1. Penicillin resistance noted as early as 1943
2. Mycobacterium tuberculosis-some strains resistant to all drugs
3. Resistance to antibiotics-result of changes in genetic information
a. initially as mutations to existing genes
b. many bacteria acquire these genes
c. Resistant gene are transferred to other members of same species.
Competency BT06.00:
Analyze issues of public health, infectious diseases, and bioterrorism.
Objective
Analyze emerging and re-emerging infectious diseases.
BT06.04:
* Globally, infectious diseases remain the leading cause of death, and they are the 3rd leading cause of death
in the US
A. Emerging infectious diseases1. Have not occurred in humans before,
2. Have occurred previously but affected only small numbers,
3. Or have occurred throughout human history, but only recently recognized as disease due to
infectious agent
4. Examples and contributing factors
a. Ebola, recognized in 1977 unknown reservoir; nosocomial
b. Legionnaire, 1977- cooling and plumbing systems
c. Lyme , 1982 – conditions favoring tick vector and deer
d. Aids, 1983 – migration to cities, global travel, tranfusions, organ transplants, IV drug use,
multiple sex partners
e. cholera, 1992 evolution of new strain bacteria
f. Sars – recognized in 2003 Severe acute respiratory syndrome, is a serious form of pneumonia.
It is caused by a virus that was first identified in 2003. Infection with the SARS virus causes
acute respiratory distress (severe breathing difficulty) and sometimes death.
B. Re-emerging infectious diseases
1. Once were major health problems globally or in a particular country, then declined dramatically,
but are again becoming health problems for a significant proportion of the population.
2. Examples and contributing factors
a. TB- new strain and standard treatment of Rifampin is not always effective.
b. Malaria- drug resistance and favorable condiions for mosquitos
c. Pertussis- refusal to vaccinate based on fear and decreased vaccine efficacy
d. Rubeola- failure to vaccinate or receive 2nd dose
e. Yellow fever- insecticide resistance, increase urbanization,
Competency BT06.00:
Analyze issues of public health, infectious diseases, and bioterrorism.
Objective
Examine the containment of bioterrorism agents.
BT06.05:
Examine the containment of bioterrorism agents
A. Agents
1. Bacterial – Anthrax and Plague
2. Viral - Smallpox
3.Toxins – Botulism and Ricin
B. Containment of bioterrorism agents
1.Isolation practices
a. Standard Precautions
b. Additional Precautions for Smallpox and the Plague
2. Patient placement
a. Routine if small scale
b. If large scale infection, patients are group
3. Patient transport – limited to movement that is essential
4. Cleaning, disinfection and sterilization of equipment and environment – follow standard
precautions
5.Discharge management
a. Discharge when no longer infectious
b. Home- care is provided if large numbers are affected with instructions on barrier
precautions, handwashing
6. Post-mortem care
a. Notify pathology
b. Provide instructions to funeral director
7. Handwashing Handwashing Handwashing
Proper Technique