Infection Prevention and Control Midterm Flashcards
Microorganism characteristics
- too small to be seen without a microscope
- less than 0.1mm
- usually unicellular
Another name for microorganisms?
- germs
- microbes
- bugs
Groups of microorganisms? (Largest to smallest)
- Protozoa
- Fungi
- Bacteria
- Viruses
What are protozoa?
Unicellular animals, move with flagella or ameboid motion
What are fungi? Types?
Primitive plants
- Yeasts: unicellular (yeast infections)
- Molds: multicellular (ringworm, athletes foot)
What is bacteria?
- unicellular
- no organized nucleus wall
- cause strep throat, staph infections, salmonella
What are viruses?
A bit of DNA or RNA surrounded by protein coat and sometimes lipid coat.
- grow only in other living cells
- influenza virus, mumps, measles, rubella
How are microbes measured?
Micrometer = 1/1000mm
Shapes of bacteria?
- round = cocci (coccus)
- rectangular = rod/bacilli (bacillus)
- spiral/curved = spirilla (spirillum)
Gram positive bacteria appear ?
Dark blue
Gram negative bacteria appear?
Red
Why is the gram reaction important?
- 1st step in identifying bacteria (look at shape and gram reaction)
- determines effectiveness of antibiotics
- determines effectiveness of disinfectants
How does bacteria reproduce?
Binary fusion: 1 splits into 2
Why are endospores bad?
They resist drying, head, and disinfectant (hard to kill)
- may take 121C to kill
- high level disinfectant and long exposure time
4 phases of bacteria growth curve?
- Lag: adapting to new environment (no symptoms, incubation)
- Log: max reproduction (full-blown symptoms, acute)
- Stationary: no change in #, decrease food, increase waste (no better, no worse)
- Death: spores may form (on the mend, covalence)
Distinctive features of viruses
- metabolically inert: can multiply only in living host cells
- contain DNA or RNA, not both
- have protein coat that surrounds nucleic acid +/- lipid envelope
are lipid or protein viruses more easy to destroy?
Lipid, except Hep B
Multiplication of animal viruses
- Attachment to complementary site on host cell membrane
- Penetration
- Viral nucleic acid: takes control of hose cell, direct synthesis
- Synthesis of viral components
- Assembly of viral components
- Release from host cell
2 effects of viruses on host cell
- Host cell dies (lysis, destroyed by hosts own lymphcytes)
2. Host cell may be transformed into tumour cell
How to control viruses?
- antiviral drugs: acyclovir, ZDV
- have to develop drugs that will destroy the viruses in host cells without destroying host cells
What are normal flora? Where are they found?
Microbes living in/on body, cause no harm as long as they stay in expected site
-found on skin and mucous membranes
Where in the body has the most normal flora?
Large intestine
Factors that affect NF?
- excessive moisture on skin = increased staphylococci (ring, watch, gloves
- antibiotic therapy: kills sensitive microbes, resistant microbes take over
Normally sterile areas in the body?
- blood
- CSF
- tissue
- fluids that surround organs
What is contamination?
-unexpected microbes at body site, do not grow, no harm (ex. Mouth bacteria on hands)
What is colonization?
Unexpected microbes at body site, DO grow, no harm initially, but maybe later
- if they go away = end of story
- if they dont go away = may cause disease
What is infection/disease?
Unexpected microbes, DO grow, DO cause harm
What is the difference between an infection and a disease?
Infection: host has pathogen, no symptoms
Disease: host had pathogen and symptoms
What is an exotoxin?
G+ bacteria released from intact bacteria and carried away from and infection site
-attack target tissue
What is an endotoxin?
G- bacteria, part of a cell wall and released when cell in interrupted, carries away from infection site
- nonspecific, effect more generalized
- can lead to destruction of organs and fatal shock
Chain of infection?
- reservoir
- means of transmission
- susceptible host
Reservoirs of infectious microorganisms?
- Humans: with infections or carriers, main reservoir for human infections
- Animals
- Nonliving: soil, H20,
- Carrier: person who harbors pathogenic microbes but show NO SIGNS of infection, can pass microbes on to others
Types of carriers?
- convalescent carrier: person had disease, symptoms now gone, microbes still in body
- chronic carrier: 6 months after symptoms gone, microbes still in body
Types of contact transmission?
- Direct: host (person to person) “touch”
- Indirect: reservoir-inanimate objects (fomite)-host
- Droplet: large “globs” of mucous that contains microorganisms
What is vehicle transmission?
Reservoir (air, food, H20, blood) hosts (usually more that one)
Types of vehicle transmission?
- food, H20: salmonella food poisoning
- droplet nuclei: very small, travel long way
- injected solutions: Hep C or AIDS from contaminated blood products used for transfusion in the past
What is vector transmission?
Reservoir to insect to host
Factors that influence host susceptibility to infectious diseases?
- age
- general health
- chemotherapy, radiation, antibiotics alter immune status
- surgery, anaesthesia, insertion of catheters
Portals of entry of infectious microorganisms?
- Skin: sweat glands, moist skin, broken skin
- Mucous membranes
- Placenta: fetus protected from moms bugs
- Parenteral: IV
Signs and symptoms of infection?
- fever: bacteria cant multiply under high temps, white blood cells more active
- lymph node swelling: traps microbes, infection causes lymphocytes to multiply, can be felt (cervical, axillary, inguinal)
- inflammation: histamine release, vasodilation, increased permeability, fluid leaks into tissues, increased phagocytes, leukocytes
4 signs of inflammation?
- heat
- redness
- pain
- swelling
What is a nosocomial infection?
Infection acquired as a result of stay in hospital or institution
5-15%
Contributing factors of nosocomial infections
- hospital microbes
- compromised patients
- transmission of microbes facilitated: patient in close proximity, catheters, incisions
Top 3 nosocomial infections in order of occurrence?
- Urinary tract infection
- Surgical wound infections
- Pneumonia
Surgical would are often infected with _________?
Staphylococcus aureus
What is an antibiotic?
Substance produced by a microorganism (often a fungus) that inhibits the growth of, or kills another microorganism (bacteria)
Current superbugs?
- MRSA
- VRE
- Clostridium difficle
Methods of controlling infection?
- silver impregnated bandages
- phages (viruses that infect specific bacterial cells and destroy them)
What do infection prevention and control practitioners do?
- specially trained staff
- develop policies and procedures both nationally and provincially
- implement policies and preventative measures
- determine patient placement
- educate staff
- monitor and report outbreaks
What is epidemiology?
The study of incidence, source, and spread of disease
What is immunization?
The process by which resistance to an infection in induced or augmented. Allows us to develop immunity without having the disease
What is immunity?
Resistance to a specific disease
What is an antigen?
A substance that indicated the immune response
What is an antibody?
Products of an immune response
Types of antibodies?
- IgM: first produced in an immune response
- IgG: second antibody produced in the immune response
What do IgM and IgG indicated?
IgM: current or recent infection or exposure to antigen
IgG: past infection (when IgM absent)
Antibody production?
- Antigenic stimulation of B lymphocytes: clone of antibody, clone of memory cell
- Immune response after primary immunization: no detectable antibodies for a week or longer, small burst of IgM then IgG
- Immune response after 2nd and 3rd booster: almost immediate` response, small burst of IgM, large burst of IgG provides protection
Amount of antibodies present in expressed as a _______?
Titer
Factors affecting response to immunization?
- Differences in immune response by host: inheritance, diseases, general health
- Site of injection: type of tissue, fat may absorb antigen
- Immunization product
- Product failure: bad batch, improper storage
Products used for immunization?
- Vaccine: suspension of bacteria or virus altered so not able to cause disease, but still antigenic
- Toxoid: bacterial exotoxin treated so no longer toxigenic, but still antigenic
Types of immunity?
- Artificially acquired: product given for the purpose of providing immunity
- Naturally acquired: such as having disease of antibodies transferred from mom to baby
- Passive immunity: host given preformed antibodies, immediate protection, used for treatment or short term prevention
- Active immunity: host makes own antibodies, used for prevention
Routine immunization schedule (after 2 months)
- DPT
- Polio
- Hib type B
- MMR
- Chicken pox
- Meningococcal conjugate
- pneumococcal conjugate
- hep B
- yearly infuenzae
- booster shots: diphtheria and tetanus every 10 yrs
Rubella symptoms
- mild infection
- rash
- or no symptoms
Danger of rubella during pregnancy?
- virus can cross placenta to infect fetus
- fetus may be aborted or stillborn
- may have defects if carried to term
Immunization for rubella
- vaccine contains MMR
- part of childhood series, before puberty
- do not immunize if pregnant of expecting to become pregnant within 3 months
- immunize males and females to eliminate viral reservoir
Who should be immunized against Hep B?
All health care workers at risk of exposure to blood or fluids capable of transmitting infection or who are at risk of sharps injuries
Hep B immunization schedule?
- 3 shots
- first two are a month apart, third six months after
What is the hepatitis immune globulin (HBIG)?
- passive immunization product with preformed antibodies
- given after a blood or mucous membrane exposure to hep B when there is no evidence of anti-HBs in health care worker
- short term protection, must be given within 24hrs
What are chicken pox (varicella-zoster)?
Generalized infection characterized by fever, malaise, and vesicular eruptions, spread by respiratory secretions or contact with vesicular fluid, 2-3 weeks incubation period, more sever in adults than children
What are shingles?
Reactivation of the latent virus in older and immunocompromised patients, cant get shingles without having had chicken pox
How to reduce risk of chicken pox?
- determine immune status
- immunization of non-immune healthcare workers
- non-immune healthcare workers exposed to chicken pox should not be around immunocompromised patients from day 10-21 following exposure
How is TB spread?
- direct contract with respiratory secretions
- droplet nuclei: greatest danger because they remain suspended in the air
Sequence of events following inhalation of TB?
- bacteria multiply slowly in lungs for 3-6 weeks
- cellular immune system become activated
- spread of bacteria inhaled-walled off by group of cells-granulonmata
- person infected but does not get disease and is not contagious
Symptoms of TB?
- initially vague: persistent cough, fever of unknown origin
- later: bloody sputum, organ dysfunction
When is the TB skin test performed?
- at start of employment
- on a regular basis following initial testing
- following a known exposure
Blood borne pathogens of greatest concern?
HIV: 0.3%
HCV: 3%
HBV: 30%
How do gloves reduce risk of infection from needle stick by 50%?
Blood wiped off outside glove as needle passes through it
Hepatitis A
- Previously called: infectious hepatitis, short incubation hepatitis
- Naked HAV
- typical symptoms, no permanent liver damage, no death
- no chronic carriers
- transmitted via food of H20 contaminated with feces or saliva
- keep stool and drool out of food
Hepatitis B
- Previously called: serum hepatitis, long incubation hepatitis
- HBV enveloped
- transmitted by blood or mucous membrane, replicated in liver, HBV in blood, semen, vaginal secretions, CSF…
- 5-10% chronic carriers even if asymptomatic
- increase chance of liver cancer, infectious for several years, serve as reservoir
- can survive for 1 week outside the body
- prevented by HBV vaccine, HBIG if exposed, passive immunity
Hepatitis C
- transmitted via blood, but poor sexual transmission
- chronic carriers common, high risk or liver cirrhosis
- no vaccine
- interferon and/or combination of new drugs, not suitable for all patients
HIV (AIDS)
- HIV enveloped, transmitted by blood, semen, vaginal secretions, mom to baby, not by kissing, touching
- Viral replication (read sheet)
- kills helper T lymphocytes, when number is significantly reduces you get clinical symptoms of AIDS
- testing no routine
- 4-12 weeks for antibodies to appear
- can get false positives
- do western blot to confirm
- ZDV slows viral replication and prolongs latent period, doesnt kill HIV
- moral, not legal responsibility to disclose if HIV positive
Progression of HIV infection?
- Contact
- Primary infection (1month): flu-like symptoms or no symptoms, HIV test may be negative
- Latent period (2yrs): no symptoms, but infectious, destruction of CD4 cells, HIV positive
- Clinical AIDS: opportunistic infection, cancers, fungal, shingles, CD4 count below 200, death
Viral infections of concern to canadians?
- SARS
- West Nile
- H1N1 flu
Where to look for information?
- WHO
- CDC
- Health canada
- IPAC Canada
- Alberta health
- your professional organization
- your local IPC departments
