Infections Flashcards
What are healthcare-associated infections (HCAIs)?
infections caused by contact with the healthcare environment and personnel
the nature of the setting and the staff can lead to an increased risk of already vulnerable patients acquiring infections
these can be avoided in most cases through appropriate general and/or specific infection control measures
Name the three most common bacterial HCAIs.
Clostridium difficile (C. difficile) methicillin-resistant Staphylococcus aureus (MRSA) Escherichia coli (E. coli)
What are bacteria?
the largest group of microorganisms of medical significance
Name the three main shapes of bacteria.
coccus (circular)
bacillus (rod)
spiral
Name two other shapes of bacteria.
coccobacillus
vibrio (spiral and bacillus)
List the main structural features of bacteria.
flagella fimbriae pili outer capsule cell wall plasma membrane cytoplasm
What is the function of flagella?
thin rigid filament allows movement
What is the function of fimbriae?
hair-like appendage
contributes to the bacteria’s ability to cause disease by binding onto a cell surface
What is the function of pili?
shorter hair-like appendage
help attachment to mucosal cells
involved in bacterial conjugation
What is the function of the outer capsule containing polysaccharides?
to allow the bacteria to bind to cell surfaces
to evade phagocytosis
What is the function of the plasma membrane?
phospholipid bilayer
partially permeable
allows transportation of substances into and out of the cell
What is the function of the cell wall?
complex semi-rigid structure
enables bacteria to be classified into gram-positive or gram-negative
What are the differences in cell wall composition between gram-positive and gram-negative bacteria?
gram-positive has a thicker peptidoglycan layer than gram-negative
gram-negative has an extra plasma membrane above the thin peptidoglycan layer
gram-positive has a lipoteichoic acid, gram-negative has lipoproteins and lipid A (toxin)
How can you distinguish between gram-positive and gram-negative bacteria?
when dyed, the different colour of the bacteria is due to a different cell wall composition
gram-positive stain crystal violet
gram-negative stain pinkish-red
What does the cytoplasm in bacteria contain?
water, enzymes, ribosomes, circular DNA, plasmids
What are viruses?
the smallest type of infectious particle
10-300nm in diameter (average 100)
List the main structural features of viruses.
capsid
envelope (not always present)
virulence factors
What is the function of the capsid?
made of capsomere proteins
contains the genetic material of the virus - ssRNA, dsRNA, ssDNA, OR dsDNA
viruses can also contain partial strands
Name the two types of shape that the capsid can form.
icosahedral
helical
What is the function of the viral envelope?
carries the capsid of genetic material
composed of a lipid bilayer which helps the virus attach to the host cell and release the genetic material inside the cell
What is the function of virulence factors?
receptors allow the virus to target certain cell types
Name some examples of types of viruses.
bacteriophage - infects bacteria
herpesvirus
picornavirus
Viruses are classified into groups/families based on which characteristics?
type of nucleic acid (DNA or RNA)
shape
structure
method of replication
How do viruses infect specific living cells?
based on the presence of suitable receptors
HIV only infects T-helper cells because the HIV virulence factors have a complementary shape to that of the T-helper CD4 receptor
Where do all viruses replicate?
inside another living cell
How does a bacteriophage replicate?
bacteriophage binds to cell
releases phage (virus) DNA
the viral infection then enters the lytic or lysogenic cycle
What happens in the lytic cycle?
phage DNA takes over the cell machinery
the cell starts to synthesise new phage DNA and proteins to create new bacteriophages
the synthesis and accumulation of new bacteriophages cause the bacteria to lyse
bacteriophages are released out and can then infect other bacteria
What happens in the lysogenic cycle?
bacteriophage binds to cell
releases phage (virus) DNA
phage DNA incorporates into the bacterial chromosome which creates a prophage (provirus)
the viral infection is latent and will cause no damage
when the bacteria divide, the phage DNA is also copied
the prophage may eventually excise from the bacterial chromosome and enter the lytic cycle
What is specialised transduction?
the lysogenic cycle gives rise to this pathway
bacterial chromosomes are transferred with the phage DNA to other bacteria through conjugation
Name the six stages of infection.
infectious agent reservoir portal of exit mode of transmission portal of entry susceptible host
What is the ‘infectious agent’?
e.g. bacterium, virus, parasite, fungus
What is the ‘reservoir’?
the place where the microorganism resides, thrives and reproduces
e.g. food, water, environmental surfaces, humans, animals
What is the ‘portal of exit’?
the way the microorganism leaves the reservoir
What is the ‘mode of transmission’?
how a microorganism transfers from one carrier to another by direct or indirect transmission
What is the ‘portal of entry’?
the entry point where the microorganism enters the host’s body
e.g. cuts in the skin, open wounds, tubes such as urinary catheters
What is the ‘susceptible host’?
the person who is at risk of developing an infection
e.g. age, underlying chronic disease, certain medication, invasive devices, malnutrition
How can you break the chain of infection at the ‘infectious agent’ stage of transmission?
improve knowledge about gram-negative bacteria
How can you break the chain of infection at the ‘reservoir’ stage of transmission?
understand reservoir (GI tract, food, environmental)
How can you break the chain of infection at the ‘portal of exit’ stage of transmission?
hand hygiene, aseptic technique, safe handling of body fluids, environmental cleaning
How can you break the chain of infection at the ‘mode of transmission’ stage?
decontamination of instruments and equipment, environmental cleaning, isolation of patients with transmissible infections, safe handling of linen
How can you break the chain of infection at the ‘portal of entry’ stage of transmission?
delivery of safe practices at every patient intervention for device and procedures
How can you break the chain of infection at the ‘susceptible host’ stage of transmission?
perform and act on risk assessment
ensure good patient hydration and nutrition
What is pneumonia?
a form of acute respiratory infection that affects the lungs
caused by bacteria, viruses or fungi
accounts for 22.8% of respiratory infections
What are the most common causes of pneumonia?
Streptococcus pneumoniae
Haemophilus influenzae type b (Hib)
the respiratory syncytial virus
Pneumocystis jiroveci
What is Streptococcus pneumoniae?
the most common cause of bacterial pneumonia in children
What is Haemophilus influenzae type b (Hib)
the second most common cause of bacterial pneumonia
What is the respiratory syncytial virus?
the most common viral cause of pneumonia
What is Pneumocystis jiroveci?
one of the most common causes of pneumonia in infants infected with HIV
accounts for at least 25% of all pneumonia-related deaths in HIV-infected infants
What are the common characteristics of the lung in a patient with pneumonia?
alveoli with fluid
inflammation of lung tissue
blockage of the bronchiole
List some of the main causes of urinary tract infections (UTIs).
catheter in situ that has bypassed the body’s defences
medication (e.g. antibiotics) that decrease the body’s ability to fight infection
Urinary tract infections can be divided into which two categories?
upper tract and lower tract
What are the two types of upper tract infection?
pyelonephritis (kidney infection)
ureteritis (ureter infection)
What are the two types of lower tract infection?
cystitis (bladder infection)
urethritis (urethra infection)
What is the most common cause of upper tract infection?
Proteus
due to the presence of bladder or kidney stones
What is the most common cause of lower tract infection?
E. coli
What is the risk of acquiring a surgical site infection (SSI) following replacement surgery?
hip replacement 0.4% in 2018/19
knee replacement 0.4% 2018/19
What is the risk of acquiring an SSI following a long bone fracture
inpatient/readmission 1.0% in 2018/19
repair of neck of femur 0.9% in 2018/19
What is the risk of acquiring an SSI following GI surgery?
large bowel surgery 9.0% in 2018/19
small bowel surgery 5.6% in 2018/19
What is the risk of acquiring an SSI following cardiac surgery?
coronary artery bypass graft (CABG) 2.3% in 2018/19 this included infections at vein harvesting sites and the sternum
What is the risk of acquiring an SSI following vascular surgery?
3.3% in 2018/19
What is the risk of acquiring an SSI following spinal surgery?
1.5% in 2018/2019
What is the risk of acquiring an SSI following breast surgery?
0.8% in 2018/19
What is the risk of acquiring an SSI following cranial surgery?
1.3% in 2018/19
What is the most common cause of SSIs?
Enterobacterales 30.0% in 2018/19
What are the three most prevalent species that make up the Enterobacterales?
E. coli (30.2%)
coliforms (19.6%)
Proteus mirabilis (13.3%)
Which other bacterium is a common cause of SSIs?
Staphylococcus aureus (22.1%) the methicillin-resistant S. aureus (MRSA) and methicillin-sensitive form increased by 1.0% from 2017/18 to 2018/19
What is Streptococcus pneumoniae?
gram-positive spherical bacteria
alpha-haemolytic (under aerobic conditions)
beta-haemolytic (under anaerobic conditions)
How does Streptococcus pneumoniae gain entry into a person?
spreads by direct person-to-person contact via respiratory droplets and by autoinoculation in people carrying the bacteria in their upper respiratory tracts
List the common signs and symptoms associated with a Streptococcus pneumoniae infection.
pneumonia - fever and chills, cough, rapid breathing, difficulty breathing, chest pain
elderly - confusion, low alertness
pneumococcal meningitis - stiff neck, fever, headache, confusion, photophobia
sepsis - confusion, shortness of breath, elevated heart rate, pain or discomfort, over-perspiration, fever, shivering, feeling cold
What is respiratory syncytial virus (RSV)?
negative-sense, single-stranded RNA virus that causes infections of the respiratory tract
How does RSV gain entry into a person?
via the eyes, nose or mouth
spreads easily through the air on infected respiratory droplets
List the common signs and symptoms associated with an RSV infection.
runny nose decreased appetite coughing sneezing fever wheezing
What is Escherichia coli (E. coli)?
gram-negative, facultative anaerobic, rod-shaped, coliform bacterium
How does E. coli gain entry into a person?
primarily through consumption of contaminated foods (e.g. raw/undercooked ground meat products, raw milk, contaminated raw vegetables and sprouts)
List the common signs and symptoms associated with an E. coli infection.
stomach pains and cramps diarrhoea that may range from watery to bloody fatigue loss of appetite or nausea vomiting fever <38.5
What are enterobacterales?
an order of gram-negative bacteria
How do enterobacterales gain entry into a person?
person-to-person contact with infected or colonised people, particularly contact with wounds or stool
List the common signs and symptoms associated with an enterobacterales infection.
high temperature aches and pains chills tiredness weakness confusion
What tests can be used to identify the cause of infection?
blood tests swabs sputum sample urine sample imaging
How can blood tests be used to identify the cause of infection?
to detect raised white cell counts and specific lymphocytes
How can swabs be used to identify the cause of infection?
taken from orifices or open wounds to undergo growth cultures to establish bacterial pattern
How can a sputum sample be used to identify the cause of infection?
taken and sent for culture growth to establish the cause of the respiratory infection
How can a urine sample be used to identify the cause of infection?
urinalysis can be undertaken at the bedside, or a specimen (midstream) can be sent for specific culture growth
How can imaging be used to identify the cause of infection?
X-ray taken for the detection of pneumonia
What factors determine which antimicrobials a patient is prescribed?
pathogen’s response to the medication
patient tolerance to the medication
Which publication can health professionals use to understand the most effective antimicrobial to prescribe for a patient?
NICE Summary of antimicrobial prescribing guidance - managing common infections (2020)
What type of antibiotic is recommended for catheter-associated UTIs?
non-pregnant women and men - nitrofurantoin
What are the pharmacodynamics and pharmacokinetics of nitrofurantoin?
synthetic compound active against range of Gram-positive and Gram-negative organisms
damages bacterial DNA
given orally and rapidly absorbed from GIT and rapidly excreted by kidneys
clinical use in treatment of urinary tract infections
Why are patients with a catheter in situ at greater risk of UTIs?
the invasive tube bypasses the body’s natural defences against infection
What vaccines are given at eight weeks old?
DTaP/IPV/Hib/HepB - Infanrix hexa
MenB - Bexsero
rotavirus - Rotarix
What does the DTaP/IPV/Hib/HepB vaccine protect against?
diphtheria, tetanus, pertussis (whooping cough), polio, Haemophilus influenzae type b (Hib) and hepatitis B
What does the MenB vaccine protect against?
Meningococcal group B (MenB)
What does the rotavirus vaccine protect against?
rotavirus gastroenteritis
Where is the DTaP/IPV/Hib/HepB vaccine usually inserted?
thigh
Where is the MenB vaccine usually inserted?
left thigh
Where is the rotavirus vaccine usually inserted?
by mouth
What vaccines are given at 12 weeks old?
DTaP/IPV/Hib/HepB - Infanrix hexa
pneumococcal conjugate vaccine (PCV) - Prevenar 13
rotavirus - Rotarix
What does the PCV vaccine protect against?
pneumococcal (13 serotypes)
Where is the PCV vaccine usually inserted at 12 weeks old?
thigh
What vaccines are given at 16 weeks old?
DTaP/IPV/Hib/HepB - Infanrix hexa
MenB - Bexsero
What vaccines are given at one year old?
Hib/MenC - Menitorix
PCV booster - Prevenar 13
MMR - MMR VaxPRO2 or Priorix
MenB booster - Bexsero
What does the Hib/MenC vaccine protect against?
Hib and MenC
What does the MMR vaccine protect against?
measles, mumps and rubella (German measles)
Where is the Hib and MenC vaccine usually inserted?
upper arm/thigh
Where is the PCV vaccine usually inserted at one year old?
upper arm/thigh
Where is the MMR vaccine usually inserted?
upper arm/thigh
What vaccine is given to eligible paediatric age groups each year from September?
live attenuated influenza vaccine (LAIV) - Fluenz Tetra
What does the LAIV protect against?
influenza
Where is the LAIV usually inserted?
both nostrils
What vaccines are given at three years four months old or soon after?
dTaP/IPV - Repevax or Boostrix-IPV
MMR (check first dose given) - MMR VaxPRO2 or Priorix
What does the dTaP/IPV vaccine protect against?
diphtheria, tetanus, pertussis and polio
Where is the dTaP/IPV vaccine usually inserted?
upper arm
Where is the MMR vaccine usually inserted at three years four months old?
upper arm
What vaccines are given to boys and girls aged 12-13 years?
HPV (two doses 6-24 months apart) - Gardasil
What does the HPV vaccine protect against?
cancers caused by human papillomavirus (HPV) types 16 and 18 (and genital warts caused by types 6 and 11)
Where is the HPV vaccine usually inserted?
upper arm
What vaccines are given at 14 years old?
Td/IPV (check MMR status) - Revaxis
MenACWY - Nimenrix or Menveo
What does the Td/IPV vaccine protect against?
tetanus, diphtheria and polio
What does the MenACWY protect against?
meningococcal groups A, C, W
and Y disease
Where is the Td/IPV vaccine usually inserted?
upper arm
Where is the MenACWY vaccine usually inserted?
upper arm
What vaccine is given at 65 years old?
Pneumococcal Polysaccharide Vaccine (PPV) - Pneumococcal Polysaccharide Vaccine
What does the PPV protect against?
pneumococcal (23 serotypes)
Where is the PPV usually inserted?
upper arm
What vaccine is given at 65 years and older each year from September?
inactivated influenza vaccine - Multiple
Where is the inactivated influenza vaccine usually inserted?
upper arm
What vaccine is given at 70 years old?
shingles - Zostavax
Where is the shingles vaccine usually inserted?
upper arm
What vaccine is required for Babies born to hepatitis B infected mothers?
Hepatitis B (Engerix B/HBvaxPRO) at birth, four weeks and 12 months old
What vaccine is required for Infants in areas of the country with TB incidence >= 40/100,000?
BCG
tuberculosis
at birth
What vaccine is required for Infants with a parent or grandparent born in a high incidence country?
BCG
tuberculosis
at birth
What vaccine is required for at-risk children
LAIV or inactivated flu vaccine if contraindicated to LAIV or under 2 years of age
from 6 months to 17 years of age
What vaccines are required for pregnant women?
inactivated flu vaccine - during flu season, at any stage of pregnancy
dTaP/IPV (Boostrix-IPV or Repevax) - pertussis, from 16 weeks gestation
What vaccines are required for patients with asplenia or splenic dysfunction (including due to sickle cell and coeliac disease)?
MenACWY MenB PCV13 (up to ten years of age) PPV (from two years of age) annual flu vaccine
What vaccines are required for patients with cochlear implants?
PCV13 (up to ten years of age)
PPV (from two years of age)
What vaccines are required for patients with chronic respiratory and heart conditions (e.g. severe asthma, chronic pulmonary disease, and heart failure)?
PCV13 (up to ten years of age)
PPV (from two years of age)
annual flu vaccine
What vaccines are required for patients with chronic neurological conditions (e.g. Parkinson’s or motor neurone disease, or learning disability)?
PCV13 (up to ten years of age)
PPV (from two years of age)
annual flu vaccine
What vaccines are required for patients with diabetes?
PCV13 (up to ten years of age)
PPV (from two years of age)
annual flu vaccine
What vaccines are required for patients with chronic kidney disease (CKD) (including haemodialysis)?
PCV13 (up to ten years of age)
PPV (from two years of age)
annual flu vaccine
hepatitis B
What vaccines are required for patients with chronic liver conditions?
PCV13 (up to ten years of age) PPV (from two years of age) annual flu vaccine hepatitis A hepatitis B
What vaccines are required for patients with haemophilia?
hepatitis A
hepatitis B
What vaccines are required for patients with immunosuppression due to disease or treatment?
PCV13 (up to ten years of age)
PPV (from two years of age)
annual flu vaccine
What vaccines are required for patients with complement disorders (including those receiving complement inhibitor therapy)?
MenACWY MenB PCV13 (up to ten years of age) PPV (from two years of age) annual flu vaccine
What are the five types of vaccines?
live attenuated (LAV) inactivated (killed antigen) subunit (purified antigen) toxoid (inactivated toxins) RNA-based
List some examples of LAV vaccines?
TB oral polio vaccine (OPV) measles rotavirus yellow fever
List some examples of inactivated vaccines?
whole-cell pertussis (WCP)
inactivated polio virus (IPV)
List some examples of subunit vaccines?
acellular pertussis (aP) Haemophilus influenzae type B (Hib) pneumococcal (PCV-7, PCV-10, PCV-13) hepatitis B (HepB)
List some examples of toxoid vaccines?
tetanus toxoid (TT) diphtheria toxoid
List some examples of RNA-based next-generation vaccines?
non-replicating
in vivo self-replicating
in vivo dendritic cell non-replicating
What is a DNA or RNA vaccine?
uses DNA or RNA molecules to teach the immune system to target key viral proteins
What are the advantages of a DNA or RNA vaccine?
easy and quick to design
What are the disadvantages of a DNA or RNA vaccine?
never been done before
there are no licensed DNA or RNA vaccines currently in use
What is a live attenuated vaccine (LAV)?
a weakened version of the actual virus
What are the advantages of a LAV?
stimulates a robust immune response without causing serious disease
What are the disadvantages of a LAV?
may not be safe for those with compromised immune systems
List some existing examples of LAVs.
measles, mumps and rubella
chickenpox
What is an inactivated vaccine?
uses the whole virus after it has been killed with heat or chemicals
What are the advantages of an inactivated vaccine?
safe because the virus is already dead and is easy to make
What are the disadvantages of an inactivated vaccine?
not as effective as a live virus
some previous inactivated vaccines have made the disease worse
Name an existing example of an inactivated vaccine.
polio
What is a subunit vaccine?
uses a piece of a virus’ surface to focus the immune system on a single target
What are the advantages of a subunit vaccine?
focuses the immune response on the most important part of the virus for protection and cannot cause infection
What are the disadvantages of a subunit vaccine?
may not stimulate a strong response
other chemicals may need to be added to boost long-term immunity
List some existing examples of subunit vaccines.
pertussis
hepatitis B
HPV
What is a viral vector vaccine?
takes a harmless virus and uses it to deliver viral genes to build immunity
What are the advantages of a viral vector vaccine?
live viruses tend to elicit stronger immune responses than dead viruses or subunit vaccines
What are the disadvantages of a viral vector vaccine?
important to pick a viral vector that is truly safe
an immune response to the viral vector could make the vaccines less effective
List some examples of viral vector vaccines.
ebola
veterinary medicine
What percentage of a population must be immune to a pathogen to achieve herd immunity?
60%
What are the pharmacodynamics and pharmacokinetics of the live attenuated influenza vaccine and MMR vaccine?
MOA - specific B-cells against an antigen are formed
oral vaccine or subcutaneous/intramuscular injection in children > 12 months
usually lifelong immunisation
What are the pharmacodynamics and pharmacokinetics of the inactivated influenza vaccine and hepatitis B vaccine?
subunit vaccines
MOA - mostly humoral immune response, the number of circulating antibodies decreases over time
usually injected into the deltoid muscle
multiple doses required
