alaura notes CH (mostly infection)

What are infectious agents?

Microorganisms that are ubiquitous; include bacteria, viruses, and fungi.

How are bacteria categorized?

By shape, gram stain, and oxygen need.

What is a virus?

The smallest microorganisms, categorized by a strain.

What are fungi?

Molds and yeasts; their role in infection depends on many factors.

What is an infection?

A disease that results from the presence of pathogens in or on the body.

What are infectious agents?

Pathogenic microorganisms capable of causing infection.

What is isolation?

Separation of patients with certain conditions from others (quarantine).

What is a pathogen?

A disease-producing microorganism.

What does pathogenicity mean?

The ability of a microorganism to produce disease.

What is colonization?

When pathogens become resident flora but do not cause disease.

What are healthcare-associated infections (HAIs)?

Infections acquired while in the hospital or while receiving healthcare.
MOST HAI ARE PREVENTABLE

What is the difference between endogenous and exogenous infections?

Endogenous: caused by the patient’s own microorganisms.
Exogenous: caused by microorganisms from another person.

What are transient bacteria?

Microorganisms that attach loosely to the skin and are removed with handwashing.

What are resident bacteria?

Microorganisms that live permanently in the skin/body and usually do not cause disease.

What are the stages of infection?

Incubation period
Prodromal stage
Full stage of illness
Convalescent period

Incubation period

between pathogen invasion and appearance of symptoms.

Prodromal stage

most infectious; early signs and symptoms appear

Full stage of illness

presence of infection-specific signs and symptoms

Convalescent period

recovery from infection.

What is iatrogenic infection?

An infection caused by medical therapy.

What is normal flora?

Resident microorganisms that normally do not cause disease and help maintain body balance.

What is the first component of the infection cycle?

Etiologic Agent (Microorganism)

How can the spread of the etiologic agent be prevented?

Hand hygiene, sterilization, antibiotics/antimicrobials

What is the second component of the infection cycle?

Reservoir (Source)

What are examples of controlling reservoirs (sources) of infection?

Transmission-based precautions, sterilization, use of disposable supplies

What is the third component of the infection cycle?

Portal of Exit (from reservoir)

How can the portal of exit from reservoirs be controlled?

Dry intact dressings, gloves, body coverings, mouth/covering when sneezing

What is the fourth component of the infection cycle?

Method of Transmission

How can the method of transmission be controlled?

Hand hygiene, use of pesticides to eliminate vectors, adequate refrigeration

What is the fifth component of the infection cycle?

Portal of Entry to the susceptible host

What is the sixth component of the infection cycle?

Susceptible Host

How can a susceptible host be protected?

Immunizations, screening health care staff

What are antimicrobials?

Drugs that treat infections by killing or slowing the growth of microbes; include antifungals.

What are antibiotics?

Drugs that treat bacterial infections.

What are antifungals?

Drugs that treat parasites and viruses.

What is asepsis?

The state of being free from disease-producing microorganisms.

What is medical asepsis?

Inhibits and prevents the spread of microorganisms; absence of almost all microorganisms (e.g., handwashing).

What is surgical asepsis?

A sterile technique that destroys ALL microorganisms; used in operating rooms, special procedures, urinary catheter insertion, and sterile body cavities.

What shape are cocci bacteria?

Circular

What shape are spirochetes?

Spiral (corkscrew).

What shape are bacilli bacteria?

Oblong

What arrangement does "strepto-" indicate?

Chains

What arrangement does "staphylo-" indicate?

Clusters.

What does aerobic mean?

Requires oxygen (O₂).

What does anaerobic mean?

Requires no oxygen.

What color do Gram-positive bacteria stain?

Purple

What color do Gram-negative bacteria stain?

Pink

Describe Gram-positive bacterial cell walls.

Thick cell wall, more susceptible to antibiotics.

Describe Gram-negative bacterial cell walls.

Thinner cell wall, contain protein A.

What makes spores significant in bacteria?

Encapsulation allows reproduction and makes them difficult to kill.

What stain is used for Acid-Fast Bacillus (AFB)?

Acid-fast stain (e.g., for TB).

Which bacterium is responsible for most diseases?

Streptococcus.

Where is Staphylococcus aureus found, and is it always pathogenic?

Found on skin; not always pathogenic.

What is MRSA?

Methicillin-resistant Staphylococcus aureus.

What is VRSA?

Vancomycin-resistant Staphylococcus aureus.

Where is E. coli found and what can it cause?

Found in the intestinal tract; causes urinary tract infections (UTIs).

What does “self-limited” mean in microbiology?

The condition goes away on its own.

What are viruses?

The smallest infectious agents, resistant to antibiotics; enter cells and reproduce.

Give examples of viral infections

Herpes, Influenza (flu), Human papillomavirus (HPV), Hepatitis A–E, COVID-19.

Which viral infections are self-limiting vs. non–self-limiting?

Self-limiting: Flu, Herpes

Non–self-limiting: HIV, Rabies

How does the immune system respond to viral infections?

It produces antibodies against viral antigens, which disable the virus.

What do vaccines contain and why?

They contain antigens that cause the body to respond and build immunity.

What is a test for viral infections such as HSV?

Viral cultures, Tzanck test (for herpes).

What are fungal (mycotic) infections?

Mold or yeast infections caused by pH changes, antibiotics, or diabetes mellitus.

Where do most fungal infections occur?

Superficial areas: skin, mucous membranes, nails, scalp.

Give examples of fungal infections.

• Tinea capitis, corporis (ringworm), cruris, pedis

• Vaginal yeast infections: Candida albicans

• Onychomycosis: nail fungal infection

• Systemic: Coccidioidomycosis (valley fever)

How are fungal infections diagnosed?

Fungal cultures and KOH slide.

How are fungal infections treated?

Antifungal drugs (topical or systemic).

What are protozoa?

Single-cell animal parasites that exist everywhere.

What are helminths?

Worms

What are arthropods in microbiology?

Mites, fleas, ticks, chiggers; can cause scabies.

Which diseases can protozoa cause?

Malaria, amebic dysentery, African sleeping sickness, trichomoniasis.

What is an infectious agent?

A pathogenic microorganism capable of causing disease (e.g., bacteria, fungus, virus).

What is a reservoir in the infection cycle?

The place where microorganisms grow, multiply, and live (natural habitat of organism).

Give examples of reservoirs.

Other people, animals, soil, food, water, milk, inanimate objects.

How can reservoirs be controlled?

Reduce mosquito population, use insect repellent.

What is the portal of exit in the infection cycle?

The path by which an organism escapes from its reservoir.

Give examples of portals of exit.

Respiratory tract, GI tract, GU tract, breaks in skin, blood, tissue.

How can portals of exit be controlled?

Wrapping wounds, wearing masks.

What is the means of transmission in the infection cycle?

The way the organism is transmitted from host to host.

Give examples of means of transmission.

• Direct contact: touching, kissing, sex, hugs

• Indirect contact: sneezing, coughing

• Vectors: insects

• Fomites: surfaces

• Airborne: droplets, dust particles

How can transmission be prevented?

Washing hands.

What is the portal of entry in the infection cycle?

The entry point where microorganisms infect a new host.

Give examples of portals of entry.

GU tract, skin, mouth, nasal cavity.

How can portals of entry be protected?

Avoid puncturing self with a needle.

Give examples of portals of entry.

GI tract, GU tract, skin, mouth, nasal cavity.

How can portals of entry be protected?

Avoid puncturing self with a needle.

What is a susceptible host?

The host most at risk for microorganism infection.

Who are the most susceptible hosts?

People with chronic illnesses or weakened immune systems.

How can susceptible hosts be protected?

Vaccines, patient skin preparation.

What is the inflammatory response?

A protective mechanism that helps the body neutralize, control, or eliminate an offending agent, and prepare for repair.

What are the hallmark signs of acute infection?

Redness, heat, swelling, pain, and loss of function.

Where do the hallmark signs of acute infection appear?

At the site of injury or invasion.

What happens in the vascular phase of inflammation?

• Small blood vessels constrict, then vasodilation of arterioles and venules occurs (causing heat and redness).

• Histamine is released, increasing vessel permeability and allowing protein-rich fluids to enter the area (causing swelling, pain, loss of function).

What happens in the cellular phase of inflammation?

• White blood cells (leukocytes), especially neutrophils (primary phagocytes), move to the area.

• Neutrophils engulf organisms and consume debris and foreign material.

• Exudate is released from the wound.

• Cells are repaired by regeneration or scar tissue formation (pus).

What is exudate?

A mass of cells and fluid that has seeped out of blood vessels or organs; can be clear, contain red blood cells, or contain pus.

What is regeneration in tissue repair?

When cells are replaced with identical cells.

What is the immune response?

A protective mechanism; the collective reaction of the immune system to an invading organism.

What is an antigen?

A foreign material that triggers an immune response.

What is an antibody?

The body’s response to antigens.