Infection Control: Chain of Infection Flashcards
What are the elements required for an infection to develop?
- An infectious agent (pathogen)
- A reservoir for pathogen growth
- A portal of exit from the reservoir
- A mode of transmission
- A portal of entry to a host
- A susceptible host
What must occur for an infection to develop?
- The chain of infection must remain intact with all elements present
How can nurses prevent infections?
- Follow infection prevention and control practices
- Break the chain of infection by eliminating one or more elements
What types of microorganisms can cause infections?
- Bacteria
- Viruses
- Fungi
- Protozoa
What are resident microorganisms?
- Permanent residents on the skin
- Survive and multiply without causing harm
- Not easily removed by handwashing with plain soap
- Example: Staphylococcus aureus
What are transient microorganisms?
- Attach to skin from contact with people or objects
- Loosely attached in dirt, grease, under nails
- Can be readily transmitted without proper handwashing
- Example: Escherichia coli
What factors determine a microorganism’s ability to cause disease?
- Sufficient number of organisms
- Virulence (ability to produce disease)
- Ability to enter and survive in the host
- Host susceptibility
What is a reservoir?
- A place where a pathogen can survive but may or may not multiply
- Examples: Hepatitis A virus in shellfish, Pseudomonas in nebulizers
What is the most common reservoir?
- The human body (skin, body cavities, fluids, discharges)
What is colonization?
- When a pathogen is present on/in the body but does not cause harm
What is a carrier?
- A person/animal with pathogens that can be transferred but no symptoms
- Example: Hepatitis B virus carrier
Other then the body what other reservoirs exist for pathogens?
- Animals, food, water, insects, inanimate objects
- Example: Legionella in contaminated water systems
What conditions allow pathogens to thrive in a reservoir?
- Food, oxygen/anaerobic, water, proper temperature, pH, minimal light
What do microorganisms require for nourishment?
- Organic matter
- Undigested food in the bowel
- Carbon dioxide
- Inorganic materials like soil
What microorganism thrives on organic matter and causes gas gangrene?
- Clostridium perfringens
What microorganism consumes undigested food in the bowel?
- Escherichia coli
What do aerobic bacteria require to survive and cause disease?
- Oxygen
Which type of organisms cause more infections, aerobic or anaerobic?
- Aerobic organisms cause more infections
Give examples of aerobic organisms.
- Staphylococcus aureus
- Strains of Streptococcus
Where are anaerobic bacteria commonly found colonizing?
- The gastrointestinal tract
What conditions allow anaerobic bacteria to cause infections?
- If the bowel is damaged
What types of infections are typically caused by anaerobes?
- Deep infections in the pleural cavity, joints, or sinus tracts
Name some diseases caused by anaerobic bacteria.
- Tetanus
- Gas gangrene
- Botulism
What do most organisms require for survival?
- Water
- Moisture
Give an example of where microorganisms thrive due to moisture.
- Moist drainage from a surgical wound
What form do some bacteria assume to survive without water?
- Spore form
What property allows bacterial spores to live without water?
- Spores remain viable when deprived of water
- Spores are resistant to drying
Name some spore-forming bacteria that can live without water.
- Bacteria causing anthrax
- Bacteria causing botulism
- Bacteria causing tetanus
What temperature range can most pathogens in humans live in?
- 35°C to 37°C
Can some microorganisms survive temperature extremes fatal to humans?
- Yes
How do cold temperatures affect bacterial growth and reproduction?
- Cold temperatures tend to prevent growth and reproduction of bacteria
What pH range do most microorganisms prefer?
- pH range of 5 to 8
In what environment do bacteria particularly thrive?
- Urine with an alkaline pH
What environment most organisms cannot survive in?
- The acidic environment of the stomach
What medications can cause an overgrowth of gastrointestinal organisms?
- Acid-reducing medications like antacids and histamine 2 blockers
What condition can gastrointestinal organism overgrowth contribute to?
- Development of nosocomial (hospital-acquired) pneumonia
In what environments do microorganisms thrive?
- Dark environments
- Under dressings
- Within body cavities
What type of light may be effective in killing certain bacteria?
- Ultraviolet light
Give an example of a bacteria that ultraviolet light can kill.
- Mycobacterium tuberculosis
What is a portal of exit?
- The path by which a pathogen leaves the reservoir/host
- Necessary for pathogens to enter another host and cause disease
What are some examples of portals of exit in the human body?
- Body openings (mouth, nose, rectum, vagina, urethra)
- Artificial openings like ostomies
- Breaks in the skin (scrapes, cuts, wounds)
- Breaks in mucous membranes
How are pathogens carried through portals of exit?
- Blood
- Body fluids
- Excretions (urine, stool, vomit)
- Secretions (saliva, mucus, pus, vaginal discharge, semen)
Give an example of a pathogen exiting through the respiratory tract.
- M. tuberculosis exits through coughing, sneezing, talking, breathing
- Pathogens exit artificial airways like tracheostomies
Give an example of a pathogen exiting through the urinary tract.
- Microorganisms from a urinary tract infection exit during urination
- Microorganisms exit through urinary diversions like ileal conduits, urostomies
How can microorganisms be transmitted from the reservoir to the host?
- Through various modes of transmission
- A microorganism may transmit through multiple modes
Give examples of microorganisms that can spread by airborne route.
- Measles virus
- Varicella-zoster virus (chickenpox)
- Mycobacterium tuberculosis (tuberculosis)
- Influenza viruses
- Severe acute respiratory syndrome coronavirus (SARS-CoV)
- Middle East respiratory syndrome coronavirus (MERS-CoV)
- SARS-CoV-2 (COVID-19 virus)
- Rubella virus
- Adenoviruses
- Aspergillus fumigatus fungus
- Coccidioides immitis fungus
- Certain types of meningitis bacteria like Neisseria meningitidis
- Smallpox virus
- Anthrax spores
Give examples of microorganisms that can spread by direct route.
- Staphylococcus aureus
- Clostridium difficile
- Norovirus
- Hepatitis B virus
- Human immunodeficiency virus (HIV)
What is a major mode of transmission in healthcare facilities?
- Indirect contact
- Healthcare workers’ hands can pick up and transmit microbes
What objects can be modes of indirect pathogen transmission?
- Any object in the environment like stethoscopes or thermometers
- Some organisms like C. difficile can live on surfaces for months
What groups must follow practices to minimize infection spread?
- All healthcare workers providing direct care or support services
- Each group follows procedures for handling patient equipment/supplies
Give an example of how respiratory therapists prevent transmission.
- Perform hand hygiene before working with each patient
- Properly dispose of contaminated therapy equipment
How do invasive diagnostic procedures increase infection risk?
- Provide avenues for pathogen spread
- Example: Cystoscopy to visualize the bladder
What must all healthcare workers do to prevent patient infection?
- Be conscientious about infection control practices
- Perform proper hand hygiene
- Ensure equipment is adequately cleaned/disinfected/sterilized
What is contact transmission & provide examples?
- Transfer of microbes by physical touch
- Can be direct contact, indirect contact, or droplet
- Examples: Clostridioides difficile, Staphylococcus, herpes simplex virus, MRSA, VRE, CPO, Ebola
What is direct contact transmission & provide examples?
- Physical skin-to-skin contact between infected/colonized person and susceptible host
- Examples: Clostridioides difficile, Staphylococcus, herpes simplex virus, MRSA, VRE, CPO, Ebola
What is indirect contact transmission & provide examples?
- Contact between susceptible host and contaminated object
- Examples: Clostridioides difficile, Staphylococcus, RSV, Pseudomonas, MRSA, VRE, CPO
What is droplet transmission & provide examples?
- Large respiratory droplets propelled up to 2m, deposited on susceptible host
- Examples: Influenza virus, rubella virus, RSV, coronavirus, Neisseria meningitidis
What is airborne transmission & provide examples?
- Small airborne droplet nuclei remain suspended in air, transmitted long distances
- Examples: M. tuberculosis, varicella-zoster virus, coronavirus, measles virus
What is vehicle transmission & provide examples?
- Single contaminated source transmits to multiple hosts, can cause outbreaks
- Examples: Pseudomonas (water, meds), E. coli (food, water), Enterobacter (IV fluids), Salmonella (food)
What is vectorborne transmission & provide examples?
- Insects or pests transmit microbes to humans
- Examples: Vibrio cholerae, P. falciparum (malaria), West Nile virus, Lyme disease
What are some portals of entry for organisms into the body?
- Body openings (mouth, nose, rectum, vagina, urethra)
- Breaks in the skin (cuts, scrapes, wounds)
- Breaks in mucous membranes
Give an example of how organisms can enter through the skin.
- When a needle pierces the skin
- As long as the device remains, more organisms can enter
How can organisms enter through a urinary catheter?
- Any obstruction to urine flow allows organisms to travel up the urethra
What factors enhance the chances of pathogens entering the body?
- Factors that reduce the body’s defenses
- Breaks in the skin or mucous membrane barriers (cuts, wounds, invasive procedures)
- Compromised immune system (due to conditions like HIV/AIDS, cancer treatment, aging)
- Presence of indwelling medical devices (catheters, IV lines)
- Poor hygiene practices (lack of handwashing, improper wound care)
- Exposure to contaminated surfaces, food, or water
- Lack of vaccinations against preventable infectious diseases
- Crowded living conditions or high-risk environments (healthcare facilities)
- Certain lifestyle factors (smoking, poor nutrition, excessive stress)
What determines whether a person acquires an infection?
- Pathogen factors: Virulence, infectious dose, ability to adhere and invade host cells
- Host factors: Immune status, age, underlying medical conditions, genetic factors
- Environmental factors: Exposure to contaminated sources, hygiene practices, crowding
- Route of transmission: Airborne, droplet, contact, vector-borne
- Integrity of host defenses: Intact skin/mucous membranes, normal microbiome
Why doesn’t everyone develop an infection despite constant microorganism exposure?
- An infection only develops when an individual becomes susceptible
- To the strength and numbers of microorganisms capable of causing infection
How does organism virulence affect susceptibility?
- The more virulent an organism, the greater the likelihood of susceptibility
Why are antibiotic-resistant organisms becoming more common?
- Believed to be associated with frequent and inappropriate antibiotic use
How can a person’s resistance to an infectious agent be enhanced?
- By receiving an appropriate vaccine
- By actually contracting the disease
How can nurses intervene to prevent infections?
- Understand the chain of infection
- Observe for signs and symptoms of infection
- Take appropriate actions to prevent spread
What factors determine the severity of a patient’s illness from infection?
- Pathogen virulence
- Infectious dose
- Route of infection
- Host immune system
- Age
- Underlying conditions
- Timeliness of treatment
- Extent of the infection
- Pathogenicity of the microorganism
- Susceptibility of the host/patient
What is a localized infection?
- Restricted to a limited area (e.g. wound infection)
- Proper care controls spread and minimizes illness
- May cause localized symptoms like pain, tenderness
What is a systemic infection?
- Affects the entire body instead of just one area
- Can be fatal
How does the course of infection influence nursing care?
- Nurses administer and monitor antibiotics
- Provide supportive therapy like nutrition and rest
- Complexity depends on body systems affected
How can nurses minimize infection spread?
- Use proper technique (e.g. dressing changes)
- Control transmission if they have breaks in skin
What are some mechanisms that protect the body against infection?
- Normal body flora inside and outside the body
- Defense mechanisms of each organ system
- Immune response that neutralizes pathogens and repairs cells
What composes the immune system?
- Cells and molecules that help resist disease
- Some responses are nonspecific (normal flora, body defenses, inflammation)
- Others are specific defenses against particular pathogens
What happens if the body’s defenses fail?
- An infection can quickly progress to a serious health problem
