NURS 1160 Lab 1 Infection Control

Infection (definition)

A disease state resulting from the entry and multiplication of a pathogen in the tissues of a host, causing the body to show clinical signs and symptoms.

Microorganisms: what are they? Give examples

Typically single-celled organisms seen only with a microscope: bacteria, protozoa, certain algae, fungi (viruses are also covered under infectious agents). They live on objects, in air, water, food, soil, plants, animals and on/in people.

Nonpathogen vs pathogen

Nonpathogen = microorganism that does not cause illness (most microorganisms). Pathogen = microorganism that can cause disease.

Communicable (infectious, contagious) disease

An infection that can be transmitted from one person to another.

Chain of infection: the 6 links (in order)

1) Infectious agent (pathogen), 2) Reservoir, 3) Portal of exit, 4) Mode of transmission, 5) Portal of entry, 6) Susceptible host.

Why does the chain of infection matter to a nurse?

An infection develops only if the whole chain stays intact. Nurses use infection prevention and control practices to BREAK a link so infection does not develop.

Lab 1 rule about the chain

You need to know ALL the points. The chain can start at any link, but it must follow the next link in order.

Does the presence of a pathogen mean infection will start?

No. Infection only develops when every element in the chain is present and connected.

Link 1: Infectious agent

The pathogen: bacteria, viruses, fungi, protozoa.

Resident flora (resident microorganisms)

Permanent residents of the skin; survive and multiply without harm. NOT easily removed by plain soap and water unless there is considerable friction. Deep-layer residents are killed mainly by hand hygiene with antimicrobial products. Example: Staphylococcus aureus.

Transient flora (transient microorganisms)

Attach loosely to skin through contact with a person or object (e.g., touching a bedpan or contaminated dressing). Live in dirt, grease and under fingernails. Readily transmitted unless removed by proper handwashing/hand hygiene. Example: E. coli (from the bowel).

Resident vs transient: which is removed by regular handwashing?

Transient microorganisms. Resident ones need friction or antimicrobial products.

When can resident skin organisms cause serious infection?

When surgery or invasive procedures let them enter deep tissues, or when the patient is severely immunocompromised.

4 factors that decide whether a microorganism causes disease

1) Sufficient number of organisms, 2) Virulence (ability to produce disease), 3) Ability to enter and survive in the host, 4) Susceptibility of the host.

Virulence

The ability of a microorganism to produce disease.

Link 2: Reservoir

A place where a pathogen can survive but may or may not multiply (source for pathogen growth). The most common reservoir is the human body. Others: animals, food, water, insects, inanimate objects.

Reservoir: example where it survives but does NOT multiply

Hepatitis A virus survives in shellfish but does not multiply.

Reservoir: example where it survives AND multiplies

Pseudomonas in nebulizer reservoirs; Legionella pneumophila (Legionnaires' disease) in contaminated water systems.

Colonization

A pathogen is present on or in the body but does not cause harm (the pathogen is colonizing the site).

Carrier

A person or animal with no symptoms who has pathogens on/in their body that can be transferred to others (e.g., a hepatitis B carrier with no signs or symptoms).

What 6 things does a reservoir need for pathogens to thrive?

Food, oxygen (or no oxygen depending on the pathogen), water, appropriate temperature, appropriate pH, minimal light.

Lab 1 slide: what is the reservoir like?

Where microorganisms grow: a dark, moist area.

Reservoir need: food

Microorganisms need nourishment. C. perfringens (gas gangrene) thrives on organic matter; E. coli consumes undigested food in the bowel; CO2 and inorganic materials like soil feed others.

Reservoir need: oxygen (aerobic vs anaerobic)

Aerobic bacteria need oxygen (e.g., Staph aureus, Streptococcus) and cause more infections than anaerobes. Anaerobes survive only without oxygen (tetanus, gas gangrene, botulism; deep pleural, joint or sinus-tract infections; damaged bowel).

Reservoir need: water

Most organisms need moisture (e.g., moist surgical wound drainage). Spore-formers (anthrax, botulism, tetanus) survive without water and resist drying.

Reservoir need: temperature

Ideal for most human pathogens is 35 to 37 degrees C. Cold tends to prevent growth and reproduction.

Reservoir need: pH

Most prefer pH 5 to 8. Bacteria thrive in alkaline urine. Most cannot survive stomach acid. Acid-reducing meds (antacids, H2 blockers) can cause GI overgrowth and contribute to nosocomial pneumonia.

Reservoir need: minimal light

Microorganisms thrive in the dark (under dressings, in body cavities). UV light can kill some (e.g., Mycobacterium tuberculosis).

Link 3: Portal of exit

The path by which the pathogen leaves the reservoir.

Portals of exit in the human body

Body openings (mouth, nose, rectal, vaginal, urethral, artificial openings like ostomies), breaks in the skin (scrape, cut, wound), breaks in mucous membranes (mouth, eyes, nose, vagina, rectum).

What carries pathogens through portals of exit?

Blood, body fluids, excretions and secretions: urine, stool, vomitus, saliva, mucus, pus, vaginal discharge, semen, wound drainage, bile, sputum.

Portal of exit example: TB

M. tuberculosis leaves the respiratory tract through the mouth and nose when the person sneezes, coughs, talks or even breathes.

Portal of exit example: devices

Tracheostomy/endotracheal tubes (respiratory); urination or urinary diversions like ileal conduits, urostomies, suprapubic drains (urinary).

Lab 1 slide: how to break the portal of exit link

Put a bandage on an open wound (and wash hands, clean surfaces).

Link 4: Mode of transmission

How microorganisms get from the reservoir to the host. An organism can use more than one mode (e.g., chicken pox: airborne or direct contact).

Which mode is a major route of transmission in health care facilities?

Indirect contact. Health care workers' hands easily pick up microbes from one person/place/thing and transmit them to others. Even a stethoscope or thermometer can be a vehicle.

C. difficile in the environment

Spore-forming; can live in hospital environments for months. Spread by direct or indirect contact.

Link 5: Portal of entry

Where organisms enter the body: the same routes they use to exit (body openings, breaks in skin or mucous membranes).

Portal of entry examples

A needle piercing the skin (more organisms can enter as long as the device is in place); urinary catheter (any obstruction to urine flow lets organisms travel up the urethra).

Lab 1 slide: portal of entry example

An open cut is an entry point for microorganisms.

Link 6: Susceptible host

A person with low resistance to a pathogen. Susceptibility depends on resistance to the strength and number of microorganisms. More virulent organism = greater likelihood the person is susceptible.

What increases or builds a host's resistance?

An appropriate vaccine or actually contracting the disease.

Lab 1 slide: susceptible host examples

Having a compromised immune system. (Interventions: wash hands, clean surfaces, cover open wounds.)

Why are antibiotic-resistant organisms more common in acute care?

Believed to be associated with frequent and sometimes inappropriate antibiotic use.

Match the intervention to the link: wash hands, clean surfaces

Breaks the mode of transmission (and reduces the reservoir).

Match the intervention to the link: bandage an open wound

Breaks the portal of exit (and protects the portal of entry).

Match the intervention to the link: vaccination

Reduces the susceptible host link.

Match the intervention to the link: wearing PPE

Blocks the mode of transmission and the portal of entry.

Match the intervention to the link: cleaning equipment between patients

Eliminates the reservoir / breaks indirect contact transmission.

Contact transmission

Transfer of microbes by physical touch. Includes direct contact, indirect contact (and droplet is listed under contact in Table 34.2).

Direct contact

Skin-to-skin contact between an infected or colonized person and a susceptible host (e.g., touching the patient).

Direct contact organisms

C. difficile, Staphylococcus, herpes simplex virus, MRSA, VRE, CPO, Ebola.

Indirect contact

Contact between a susceptible host and a contaminated intermediate object (soiled linen, equipment, dressings) or via hands not washed between patients.

Indirect contact organisms

C. difficile, Staphylococcus, RSV, Pseudomonas, MRSA, VRE, CPO.

Droplet transmission

Large particles from the respiratory tract of an infected source, propelled up to 2 m through the air and deposited on a susceptible host (coughing, sneezing, talking).

Droplet organisms

Influenza virus, rubella virus, RSV, coronavirus, Neisseria meningitidis.

Airborne transmission

Small particles (droplet nuclei) with microbes stay suspended in air for long periods; air currents carry them long distances (more than 2 m); the susceptible host inhales them.

Airborne organisms

Mycobacterium tuberculosis, varicella-zoster virus (chicken pox), coronavirus, measles virus.

Vehicle transmission

A single contaminated source (water, medications, IV fluid, food, equipment) transmits infection to multiple hosts, possibly causing an outbreak.

Vehicle organisms

Pseudomonas (water, medications), E. coli (food, water), Enterobacter cloacae (IV fluid), Salmonella (food).

Vectorborne transmission

Insects (fleas, mites, ticks, mosquitoes) or pests (e.g., mice) transmit microbes to humans.

Vectorborne organisms

Vibrio cholerae, Plasmodium falciparum (malaria), West Nile virus, Lyme disease.

Droplet distance vs airborne distance

Droplet: up to 2 m. Airborne: more than 2 m.

Which diseases are airborne? (memory list)

TB, chicken pox (varicella), measles, coronavirus.

Which diseases are droplet? (memory list)

Influenza, rubella, RSV, coronavirus, Neisseria meningitidis.

Chicken pox is spread by which modes?

Airborne OR direct contact (a microorganism can use more than one mode).

A contaminated IV bag infects several patients: which mode?

Vehicle transmission.

A nurse touches a patient with MRSA, then another patient without washing: which mode?

Indirect contact (contaminated hands as the intermediate object).

A mosquito transmits West Nile: which mode?

Vectorborne.

Course (stages) of infection: the order

Incubation period, prodromal stage, illness stage, decline, convalescence. (Box 34.1 lists 4 stages: incubation, prodromal, illness, convalescence; the lab slides add Decline between illness and convalescence.)

Incubation period

Interval between entry of the pathogen into the body and appearance of the first symptoms (time from exposure until onset of symptoms).

Incubation period examples

Chicken pox 2 to 3 weeks; common cold 1 to 2 days; influenza 1 to 3 days; mumps 15 to 18 days.

Prodromal stage

Interval from onset of nonspecific signs and symptoms (malaise, low-grade fever, fatigue) to more specific symptoms. Organisms grow and multiply and the person can already spread the disease.

Can a person spread infection during the prodromal stage?

Yes. The infectious agent keeps replicating and the person may be more capable of spreading disease to others.

Illness stage

Interval when the patient shows signs and symptoms specific to the type of infection.

Illness stage: general symptoms

Fever, fatigue, headache, muscle aches, swollen lymph nodes.

Illness stage: respiratory symptoms

Persistent cough, runny nose, sneezing, sore throat, difficulty breathing.

Illness stage: GI symptoms

Diarrhea, nausea, vomiting, stomach pain, loss of appetite.

Illness stage examples (Box 34.1)

Common cold: sore throat, sinus congestion, rhinitis. Mumps: earache, high fever, parotid and salivary gland swelling.

Decline stage (lab slides)

Immune system mounts a successful defence; infectious particles decrease and symptoms gradually improve. Secondary infections can develop if the primary infection weakened the immune system. The virus can still be transmitted.

Convalescence

Acute symptoms disappear; the body replenishes resources and returns to homeostasis. Length depends on severity of infection and general health (days to months). Some people have permanent damage.

Which stage is the person symptom-free but already infected?

Incubation period.

Which stage has vague symptoms like malaise, low-grade fever, fatigue?

Prodromal stage.

Which stage has symptoms specific to the infection?

Illness stage.

Localized vs systemic infection

Localized = restricted to a limited area (e.g., wound infection: pain, tenderness at the site). Systemic = affects the entire body rather than a single organ or part; can be fatal.

Pathogenicity

The ability of a microorganism to cause disease. Severity of illness depends on extent of infection, pathogenicity, and susceptibility of the host.

Defences against infection

Normal flora, body system defences, inflammation (vascular and cellular responses, inflammatory exudate, tissue repair), and the immune response (nonspecific and specific).

Health care-associated infection (HAI)

An infection acquired after admission to a health care facility that was not present or incubating at admission. Also called nosocomial infection or iatrogenic infection.

Other names for HAI

Nosocomial infection, iatrogenic infection, hospital-acquired infection.

Community-acquired infection

An infection acquired outside the health care setting (contrasted with hospital-acquired infection on the lab slide).

Why are hospitalized patients at higher risk of infection?

High acuity of illness; aggressive treatments that compromise immunity; many susceptible people frequently receiving antibiotics in close proximity (antibiotic-resistant organisms spread).

Clostridioides difficile infection (CDI)

One of the most common and costly HAIs. Gram-positive, spore-forming, anaerobic bacillus producing toxins A and B that cause diarrhea and colitis in patients whose flora were disrupted by prior antibiotics.

Pseudomembranous colitis (PMC)

More severe form of CDI: colitis with pseudomembranes on the colon surface seen during endoscopy.

Preventing C. difficile transmission

Contact isolation; hand hygiene with soap and water (for patients with diarrhea); gloves and gown; thorough environmental cleaning; antibiotic stewardship.

Examples of procedure-related HAI

UTI after urinary catheter insertion.

Exogenous infection

Arises from microorganisms external to the person that are not normal flora. Examples: Salmonella, Clostridium tetani.

Endogenous infection

Occurs when the patient's own flora become altered and overgrow, or when enough organisms from one body site are transferred to another. Examples: enterococci, yeasts, streptococci.

Endogenous example

Enterococci (normally in feces) moved from hands to skin is a common cause of wound infections.

Factors that raise a patient's HAI risk

Number of health care workers with direct contact, type and number of invasive procedures, therapy received, length of hospitalization.

Major sites of HAI

Surgical and traumatic wounds, urinary tract, respiratory tract, bloodstream.