week 4: Ch. 6- Infection Flashcards
Pathogens:
Disease-causing microbes
Bacteria
Classified as:
Function:
Divide by:
Structure:
Appearance:
◦ Classified as prokaryotes
◦ No nuclear membrane—no nucleus
◦ Function metabolically & reproduce
◦ Divide by binary fission
◦ Complex cell wall structure
◦ Do not require living tissues to survive
◦ Vary in size and shape
Bacilli
Rod-shaped organisms
Spirochetes
Include spiral forms and Vibrio spp.
Cocci
Spherical forms
◦ Diplococci
◦ Streptococci
◦ Staphylococci
Two types of bacteria that differ in chemical composition:
◦ Gram-positive
◦ Gram-negative
External capsule or slime layer
◦ Found in some bacteria
◦ Outside the cell wall
◦ Offers additional protection
Flagellae
◦ One or more attached to cell wall
◦ Provide motility for some species
Pili or fimbriae
◦ Tiny hairlike structures—found in some bacteria
◦ Assist in attachment to tissue
◦ Transfer of DNA to another bacterium
Cell membrane
◦ Inside the bacterial cell wall
◦ Selectively permeable
Cytoplasm contains:
◦ Chromosome- One long strand of DNA
◦ Ribosomes and RNA
◦ Plasmids- DNA fragments; nonchromosomal; exchange DNA during conjugation
Exotoxins are usually produced by:
gram-positive bacteria
Endotoxins
Present in:
Released:
Can cause:
◦ Present in the cell wall of gram-negative bacteria
◦ Released on death of bacterium
◦ Vasoactive compounds that can cause septic shock
Spores
Formed by:
__________ form of bacterium
Can survive:
Highly resistant to:
◦ Formed by several species
◦ Dormant-latent form of bacterium
◦ Can survive long periods of time in spore state
◦ Highly resistant to heat and disinfectants
Viruses are small:
obligate intercellular parasites
Viruses structure
◦ Protein coat or capsid
-protein coat comes in various shapes and sizes
◦ Can change (mutate) quickly
◦ Nucleic acid - DNA or RNA
◦ Classification dependent on nucleic acid present
◦ Some RNA-containing viruses contain reverse transcriptase enzyme to convert RNA to DNA.
Active Viral Infection steps
◦ Virus attaches to ___________
◦ Viral ___________ material enters cell.
◦ Viral _______________ takes control of cell.
◦ Uses host’s cell to synthesize ____________________________________________
◦ New viruses are assembled in cytoplasm of cell.
◦ Viruses released by ____________________________ from host cell membrane
◦ Virus attaches to host cell.
◦ Viral genetic material enters cell.
◦ Viral DNA or RNA takes control of cell.
◦ Uses host’s cell to synthesize viral proteins & nucleic acids
◦ New viruses are assembled in cytoplasm of cell.
◦ Viruses released by lysis of host cell or by budding from host cell membrane
Latent Viral Infection steps
◦ Virus enters cell as with active infection.
◦ Viral _________ are produced and Inserted into [may stimulate an immune response and destruction of host cell]
◦ Virus may ____________________________ if immune system is depressed (e.g., herpesviruses)
◦ Virus enters cell as with active infection.
◦ Viral proteins are produced and Inserted into [may stimulate an immune response and destruction of host cell]
◦ Virus may reproduce actively if immune system is depressed (e.g., herpesviruses)
Describe characteristics of Chlamydia, Rickettsiae,
Mycoplasmas
◦ Obligate intercellular parasites.
◦ Do not grow on artificial media
◦ Some similarities with both bacteria and viruses
◦ Lack some basic components
◦ Classified as bacteria
◦ Replicate by binary fission within host cell
Chlamydia
~cause of? results in?
◦ Common cause of sexually transmitted disease
◦ Can result in infertility
Rickettsiae
~Gram? Transmitted by?
◦ Gram-negative
◦ Transmitted by insect vectors (lice, ticks)
Mycoplasmas
~Lack? Causes?
◦ Lack cell wall
◦ Cause of atypical type pneumonia
___________ (fungus) can cause neurologic disease and can be transmitted to embryo or fetus if mother is infected
Histoplasma
Fungi
◦ ________________ organisms (contain nucleus)
◦ Found throughout environment - On animals, plants, humans, food
◦ Fungal or mycotic infection
◦ From single-celled_________ or multicellular molds
◦ Only a few are _________________.
◦ Cause primary infection on skin or mucous membranes but may spread systemically particularly in immunosuppressed individual
◦ Eukaryotic organisms (contain nucleus)
◦ Found throughout environment - On animals, plants, humans, food
◦ Fungal or mycotic infection
◦ From single-celled yeast or multicellular molds
◦ Only a few are pathogenic.
◦ Cause primary infection on skin or mucous membranes but may spread systemically particularly in immunosuppressed individual
_______________ (fungus) is AKA athlete’s foot
Tinea pedis
Candida (fungus):
usually harmless, but opportunistic
◦ Causative agent of :
thrush and vaginitis
Protozoa
◦ Eukaryotic forms
◦ Unicellular, lack cell wall
◦ Many live independently, others are obligate parasites
◦ Pathogens are usually parasites.
◦ Examples of protozoal diseases:
-Trichomoniasis
-Malaria
-Amebic dysentery
Helminths (flatworms or roundworms)
◦ Are not microorganisms
◦ Parasites
◦ May be small or up to 1 m in length
◦ Life cycle with 3+ stages- Ovum, larva, adult
◦ Enter body through skin or by ingestion
◦ Infections more commonly found in young childs
◦ Infection can be life-threatening in an immunosuppressed client.
___________: ova inhaled in dust in fecally contaminated areas; common in children worldwide
Pinworms
__________: larvae enter skin from fecally contaminated soil in tropical areas
Hookworms
________________: most common form transmitted by larvae in undercooked pork
Tapeworms
___________—giant roundworm: ingested with food that has been grown in feces-contaminated soil or prepared with hands that have been in feces-contaminated soil
Ascaris
Prions
◦ Protein-like agents that change the shape of proteins within host cells
◦ Transmitted by contaminated tissues
~Ingestion of meat/ Infected blood or donor organs
◦ Cause degenerative disease of nervous system
◦ Human prion diseases
~Creutzfeldt-Jacob disease and variant Creutzfeldt-Jacob disease
~Both rapidly progressive and fatal
Many areas of the body have a resident population of mixed microorganisms termed ______________________ in the
◦ Skin
◦ Nasal cavity
◦ Mouth
◦ Gut
◦ Vagina
◦ Urethra
resident/normal flora.
Infection—organism is able to:
reproduce in or on body’s tissues
◦ Endemic VS
◦ Epidemic VS
◦ Pandemic
◦ Endemic: Continuous transmission within a population
◦ Epidemic: Higher than normal transmission or spread to new geographical area
◦ Pandemic: Transmission has occurred on most continents.
Reservoir
◦ Source of infection
◦ Person with active infection OR
◦ Person who is asymptomatic
◦ Environmental source such as contaminated soil, Infected person or animal
Carrier
◦ A person may never develop the disease but still is a carrier.
◦ A person with subclinical signs of the disease
_______: the microbe causing the infection
Agent
________ _____ ____: means whereby the agent leaves the reservoir
Portal of exit:
_________ ___ ______________: method whereby the agent reaches a new susceptible host
◦ Air
◦ Water
◦ Direct contact
◦ Food
Mode of transmission
________________: access to new host
Portal of entry
Susceptible host: susceptibility will depend on:
◦ Health status
◦ Immunity
◦ Age
◦ Nutrition
Transmission could be direct or indirect:
Direct contact
◦ No intermediary
◦ Touching infectious lesion, sexual activity
◦ Contact with infected blood or bodily secretions
Indirect contact
◦ Involves intermediary object or organism
◦ Contaminated hand or food
◦ Fomite—inanimate object
____________ transmission: Respiratory or salivary secretions are expelled from infected individual
Droplet
_________ transmission: Involve small particles from the respiratory tract; Suspended in air and can travel farther than droplets
Aerosol
__________: Insect or animal is an intermediate host
Vector-borne
Nosocomial Infections
◦ Occur in health care facilities- Hospitals, nursing homes, physician’s offices, dental offices
◦ 10% to 15% of patients acquire an infection in the hospital because of:
~Many microbes present
~Patients with undiagnosed infectious disease
~Shared environment
~Treatment that may cause weakened immune system
~Many health care workers and fomites act as reservoirs.
Factors That Decrease Host
Resistance
◦ Age (infants and older adults)
◦ Pregnancy
◦ Genetic susceptibility
◦ Immunodeficiency
◦ Malnutrition
◦ Chronic disease
◦ Severe physical or emotional stress
◦ Inflammation or trauma
◦ Impaired inflammatory responses
Pathogenicity:
capability of a microbe to cause disease
Virulence
◦ Degree of pathogenicity
◦ Invasive qualities (e.g., motility or enzymes)
◦ Toxins
◦ Adherence to tissue by pili, fimbriae, specific receptor sites
◦ Ability to avoid host defenses
Infection control requires two approaches:
◦ Standard Precautions used in all settings with all clients when body fluids may be exchanged.
◦ Specific Precautions in clients diagnosed with a particular infection—these are used in addition to standard precautions.
Incubation period
◦ Time between entry of organism into the body and appearance of clinical signs of disease
◦ Vary considerable with different organisms
Prodromal period
◦ Fatigue, loss of appetite, headache
◦ Nonspecific—“coming down with something”
◦ More evident in some infections than others
Acute period
Infectious disease develops fully
Sterilization of equipment by:
◦ Chemicals
◦ Heat in an autoclave
◦ NOTE: Equipment must be cleaned prior to sterilization or it will remain contaminated!
Use of chemicals:
◦ Antiseptics are used on the skin and tissues.
◦ Disinfectants are used on surfaces or objects.
Local VS system signs of inflammation
Local
◦ Pain, swelling, redness, warmth
◦ If bacterial—purulent exudate
◦ If viral—serous, clear exudate
Systemic
◦ Fever may be present.
◦ Fatigue and weakness
◦ Headache
◦ Nausea
Methods of Diagnosis
◦ Culture and staining techniques
◦ Blood tests
[Leukocytosis—bacterial infection]
[Leukopenia—viral infection]
~Differential count
~C-reactive protein
~Erythrocyte sedimentation rate (ESR)
◦ Immunological testing of body fluids
~Antigen identification/titer
If drug resistance is known to occur with infection, use:
multidrug therapy.
Antibiotic- Drugs derived from :
organisms
Bactericidal- drugs destroy :
organism
Bacteriostatic- decrease rate of :
reproduction
Broad VS narrow spectrum antimicrobials
broad spectrum- Effective against both gram-positive and gram-negative organisms
narrow spectrum- Effective against either gram-positive or gram-negative organisms
First- VS second-generation drugs
◦ 1st gen—original drug class
◦ 2nd gen—later version, which may be more effective, more tolerable/ easily administered
Mode of Actions of antibiotics with an example of each
◦ Interfere with bacterial cell wall synthesis- penicillin
◦ Increase permeability of bacterial cell membrane- polymyxin
◦ Interfere with protein synthesis- tetracycline
◦ Interfere with synthesis of essential metabolites- sulfonamides
Mode of Actions of Antivirals (3)
◦ Blocking entry into host cell
◦ Inhibiting gene expression
◦ Inhibiting assembly of the virus
Antifungal Agents
◦ May interfere with___________ in fungi
◦ May increase fungal membrane __________
◦ Most antifungal agents administered topically to skin or mucous membranes
◦ Fungi are eukaryotic cells and are therefore often toxic to animal and human cells.
~Treatment requires strict medical supervision
◦ May interfere with mitosis in fungi
◦ May increase fungal membrane permeability
◦ Most antifungal agents administered topically to skin or mucous membranes
◦ Fungi are eukaryotic cells and are therefore often toxic to animal and human cells.
~Treatment requires strict medical supervision
Antiprotozoal agents
◦ Similar characteristics to antifungal agents
◦ Protozoans are eukaryotic cells.
◦ Many pathogenic protozoa have several stages in their life cycles.
◦ Require treatment with different agents at different stages of the cycles
-Trichomoniasis
-Malaria
-Amebic dysentery
are all
protozoal diseases
