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