MP321 Master Deck

What is an example of a bacteria that causes skin infection?

• staphylococcus aureus

What is an example of a bacteria that causes upper respiratory tract infection?

• streptococcus pyogenes

What is an example of a bacteria that causes urinary tract infection?

• Escherichia coli

What are differences between eukaryotes and prokaryotes?

EUKARYOTES	PROKARYOTES
Large cell	Small cell
Organelles present	Organelles absent - genetic info loose in cytoplasm (no nucleus)
Multiple linear chromosomes	1 circular chromosome (+plasmids)
No cell wall (except for FUNGI)	Cell wall (BACTERIA)
80S ribosomes	70S ribosomes

What part of bacteria do antibiotics target (in order to kill the cell)?

• primarily the cell wall

What does a colony on an agar plate consist of?

• one colony consists of many bacteria cells which is why its visible to the naked eye (one cell requires a microscope to be seen)

What does MacConkey agar consist of?

• peptones

• lactose

• bile salts and crystal violet (inhibit gram +ve bacteria)

• neutral red (pH indicator)

What colour does MacConkey agar turn into when bacteria ferment lactose?

Why does it turn that colour?

• turns red

• due to the bacteria (E.coli or klebsiella) turning lactose → lactic acid

  • this lowers pH

  • pH indicator causes red medium and red colonies with a surrounding zone of precipitated bile salts (haziness)

  • 

What colour does MacConkey agar turn into when bacteria does not ferment lactose?

Why does it turn that colour?

• yellow medium agar with colourless colonies

• uses peptone instead of lactose which causes ammonia to be formed → higher pH (more alkali)

What are some bacteria that turn MacConkey agar red?

What are some bacteria that turn MacConkey agar yellow?

• Escherichia Coli and Klebsiella as they both ferment lactose

• Salmonella and Pseudomonas Aeruginosa 

What is a round bacteria cell called?

• coccus (singular) or cocci (plural) shaped

What is a rectangular/oblong bacteria cell called?

• rod shaped

What does strep cells look like (in terms of arrangement)?

• look like they are arranged in a line

What do staph cells look like (in terms of arrangement)?

• are stacked together

What is the difference between streptococci and staphylococci shaped cells?

• strep = line, staph = stacked

  

What shape would a bacillus cell be?

• rod shaped 

  

What colour would gram +ve bacteria be?

• purple

What colour would gram -ve bacteria be?

• pink

What is the gram staining process steps for bacteria?

• crystal violet used first (turns +ve and -ve purple at first)

• iodine

• decolourisation (if +ve remains purple, if -ve goes back to clear)

• safranin is used as a counter stain = binds to gram -ve 

  • turns gram -ve pink

Does gram +ve bacteria have thicker or thinner cell wall?

• has a thicker cell wall

What part of bacterial cell dictated whether the cell is gram -ve or +ve?

• the cell wall

What is the bacterial cell wall composed of?

What characteristics does this cell wall have? 

• peptidoglycan layers (sugar and peptide layers)

• results in a very rigid structure

Does gram +ve or gram -ve have thinner cell wall?

• gram -ve 

Why are gram -ve bacteria harder to treat?

• because has 2 membranes that drug needs to be able to go through and the lipopolysaccharides on outer membrane acts as a barrier

  

What do gram -ve bacteria have that gram +ve bac do not?

What is it for?

• has an extra layer made up of lipopolysaccharides

• is an extra layer of protection

  

What are porins, where are they located and what do they do?

• are channels located in gram -ve bacteria in the outer membrane that let small hydrophilic molecules go past the outer membrane and into the cell

  

What are 3 gram +ve cocci?

• Staphylococcus aureus

• Streptococcus pyogenes

• Enterococcus faecalis

	Cocci	Rods
Gram +	Staphylococcus aureus Streptococcus pyogenes Enterococcus faecalis	Clostridioides botulinum Clostridioides difficile Clostridioides perfringens Clostridioides tetani
Gram -	Neisseria gonorrhoeae Neisseria meningitidis	Escherichia coli Pseudomonas aeruginosa Klebsiella pneumoniae Haemophilus influenza

What are 2 gram -ve cocci?

• Neisseria gonorrhoeae

• Neisseria meninigitis

	Cocci	Rods
Gram +	Staphylococcus aureus Streptococcus pyogenes Enterococcus faecalis	Clostridioides botulinum Clostridioides difficile Clostridioides perfringens Clostridioides tetani
Gram -	Neisseria gonorrhoeae Neisseria meningitidis	Escherichia coli Pseudomonas aeruginosa Klebsiella pneumoniae Haemophilus influenza

What are 4 gram+ rods?

• Clostridioides botulinum

• Clostridioides difficlle

• Clostridioides perfringens

• Clostridioides tetani

	Cocci	Rods
Gram +	Staphylococcus aureus Streptococcus pyogenes Enterococcus faecalis	Clostridioides botulinum Clostridioides difficile Clostridioides perfringens Clostridioides tetani
Gram -	Neisseria gonorrhoeae Neisseria meningitidis	Escherichia coli Pseudomonas aeruginosa Klebsiella pneumoniae Haemophilus influenza

What are 4 examples of gram -ve rods?

• Escherichia coli

• Pseudomonas aeruginosa

• Klebsiella pneumoniae

• Haemophilus influenza

	Cocci	Rods
Gram +	Staphylococcus aureus Streptococcus pyogenes Enterococcus faecalis	Clostridioides botulinum Clostridioides difficile Clostridioides perfringens Clostridioides tetani
Gram -	Neisseria gonorrhoeae Neisseria meningitidis	Escherichia coli Pseudomonas aeruginosa Klebsiella pneumoniae Haemophilus influenza

What problems does Escherichia coli cause?

• gastroenteritis, UTI, neonatal meningitis

What bacteria causes 90% of UTIs?

• Escherichia coli

What problems does Pseudomonas aeruginosa cause?

• pneumonia and infections in cystic fibrosis, burn injuries and nosocomial infections

Where do people tend to contract Pseudomonas Aeruginosa?

• in the hospital a lot of the time

What problems does Staphylococcus aureus cause?

• skin and soft tissue infections, bone/joint infections, endocarditis, toxic shock syndrome and food poisoning

What problems does Streptococcus pyogenes cause?

• skin/throat infections e.g. → erysipelas/cellulitis and pharyngitis

What are mycobacteria?

• neither gram +ve or -ve.

• myco = like a fungus

What are examples of mycobacteria?

• mycobacterium tuberculosis

• mycobacterium avium complex → pulmonary infection in immunocompromised people

• mycobacterium leprae → leprosy

What stain is used for mycobacteria?

What is the colour change?

• Ziehl-Neelson’s (ZN) stain used

• goes from purple → red

What is a capsule?

What is the benefit in a capsule for bacteria?

what is the benefit in a capsule for us?

• some bacteria have a capsule 

• extra protection against drugs, phagocytosis etc

• highly antigenic → used to develop vaccines

What are pilli?

What do flagellum aid bacteria in?

• parts of bacteria that are the sticky outy bits and they are important for adhesion to surfaces/cells

• allows bacteria to be motile

What is an endospore and what can it do?

• an endospore is like a miniature bacterium that is not a full bacteria cell but under the right conditions can convert into an active bacterial cell

  • endospores can lay dormant for a long time

What do fungi have instead of cholesterol in their cytoplasm?

What does this help indicate?

• ergosterol

• indicates cell to be fungi if ergosterol is present

What is a large spread of mould called

• mycellium

What is penicillium mould?

What does penicillium look like under a microscope?

• a multicellular organism that releases fungal spores

• a little brush (penicillium means little brush in Latin)

What is candida albicans and what does it cause?

Why is it considered opportunistic?

• yeast = causes oral/genital infections in immunocompromised individuals

• it is part of human gut flora and normally doesn’t cause problems unless someone is immunocompromised

What are signs of infections?

• redness/ change in skin colour (especially around a wound)

• pain or tenderness

• heat

• swelling

• loss of function

What does tachypnoea mean?

• fast breathing rate

What is sputum?

• similar to mucus

• green-yellow indicates infection

• red = blood in sputum

What are clinical signs related to specific infections?

• increased sputum volume / increased sputum purulence

• pus

• rashes

• cough

• pain on urination

• nasal congestion

• sore throat

What is SIRS criteria used to determine?

• criteria to help determine whether patient has inflammation

What are the SIRS criteria?

• temperature <36 or >38

• Pulse > 90bpm

• respiratory rate > 20 breaths per min

• White cell count <4 or >11

  • useful for bacterial infection, less so for viral/fungal

What does SIRS stand for?

• systemic inflammatory response syndrome

Is SIRS specific to infection?

• no as it just used to determine inflammation (nothing to do with infection although inflammation often due to infection)

What are exogenous sources of infection?

What are endogenous sources of infection?

• exogenous → from the host or environment = food, water, soil, coughing and sneezing

• endogenous → normal flora from another part of the body = skin pathogens, gut pathogens

Do you wait for outcome of cultures to start treatment?

• mostly, no → required to clinically diagnose and give a best guess as to what patient has and then treat based on the empirical evidence 

What part of urine stream is used for sample?

• mid stream sample → pee pot midway through stream

What can be sampled for bacteriological assessment?

• blood cultures

  • different sites, taken when patient is pyrexial

• sputum

• urine

• pus

• bone samples

• surgical samples

• nail clippings

• swabs

  • wounds

  • eyes

  • throat

  • nose

What is MEWS used for?

• Is the Modified Early Warning System and is used to note observations of patient

• if the total is 4 or more across parameters then the ward doctor is informed

• Parameter	Score
  	3	2	1	0	1	2	3
  Respiratory rate		< 8		9 – 14	15 – 20	21 – 29	> 29
  Heart rate		< 40	41 – 50	51 – 100	101 – 110	111 – 129	> 129
  Systolic BP (mmHg)	< 70	71 – 80	81 – 100	101 – 199
  Urine output (ml/kg/hr)	Nil	<0.5
  Temperature		< 35	35.1 – 36	36.1 – 38	38.1 – 38.5	> 38.6
  Neurological				Alert	React to voice	React to pain	Unresponsive

What is SEWS used for?

• Is the Surgical Early Warning System

• Parameter	Score
  	3	2	1	0	1	2	3
  RR	> 36	31 – 35	21 – 30	9 – 20			< 8
  SpO2 (%)	< 85	85 – 89	90 – 92	> 93
  Temperature (oC)		> 39	38 – 38 .9	36 – 37.7	35 – 35.9	34 – 34.9	< 33.9
  Systolic BP (mmHg)		> 200		100 – 199	80 – 99	70 – 79	< 69
  HR	> 130	110 – 129	100 – 109	50 – 99	40 – 49	30 – 39	< 29
  Response				Alert	Verbal	Pain	None

-Similar to MEWS but 4 or more = contact doctor for review, 6 or more = urgent review

What are other parameter that can be used to indicate infection?

What is CURB 65?

• stands for confusion, urea, respiratory rate, blood pressure and over 65 y/old.

  CURB 65
  Symptom	Points
  Confusion	1
  BUN > 7mmol/L	1
  Respiratory rate > 30	1
  SBP < 90mmHg DBP < 60mmHg	1
  Age > 65	1

CURB 65
Symptom	Points
Confusion	1
BUN > 7mmol/L	1
Respiratory rate > 30	1
SBP < 90mmHg DBP < 60mmHg	1
Age > 65	1

What is CRB 65?

• a version of CURB 65 that can be done in a pharmacy

• 0 = low risk of death, normally don’t require hospitalisation

• 1 or 2 = increased risk of death → hospitalisation considered

• 3+ = high risk of death → urgent hospital admission

  CRB 65
  Symptom	Points
  Confusion	1
  Respiratory rate > 30	1
  SBP < 90mmHg DBP < 60mmHg	1
  Age > 65	1

What are societal and behavioural barriers to disease?

• societal = clean water, waste disposal

• behavioural = hand washing, condoms, hospital sterilisation

What are some physiological barriers to disease and what line of defence are they?

• skin - physical barrier

• mucus membranes e.g. → mouth, nose, eyelids

• eyes - lysozymes (provide antimicrobial protection)

• 1st line of defence

What is the respiratory tract’s physiological barriers to disease?

What is the digestive tract’s physiological barriers to disease?

What is the urogenital tract’s physiological barriers to disease?

• mucus and cilia

• stomach acid, pancreatic enzymes, bile, peristalsis

• urethra, flushing, acidity

What is the second line of defence?

What is part of this defence?

• non specific immunity

• pyrogens → peptides secreted by leukocytes that act on the hypothalamus to induce fever

• interferons → proteins that interfere with viral replication

• complement → plasma proteins that destroy cells

• phagocytes _. immune cells that engulf foreign particles and act as omnivorous scavengers

What are pyrogens, what do they act on and what do they do?

• a peptides that are secreted by leukocytes, act on the hypothalamus and induce fever

• non-specific immunity (second line of defence)

What are interferons and what do they do?

• proteins that interfere with viral replication

• non-specific immunity (second line of defence)

What is complement in non-specific immunity?

• plasma proteins that destroy cells

What are the types of phagocytes?

• neutrophils - found in blood and tissue, first responders at site of infection

• monocytes - roaming phagocytes in the blood that differentiate into macrophages in tissues

• fixed phagocytes - organ/ tissue specific e.g. osteoclasts

• microglia - CNS resident

• dendritic cells - derived from monocytes, often found in tissues in contact with external environment - major role in antigen presentation

What and where are neutrophils?

• neutrophils - found in blood and tissue, first responders at site of infection

What and where are monocytes?

• monocytes - roaming phagocytes in the blood that differentiate into macrophages in tissues

What and where are dendritic cells?

• dendritic cells are  derived from monocytes,

• often found in tissues in contact with external environment (e.g. skin)

• are early warning cells - major role in antigen presentation

How do phagocytes destroy pathogens?

• The phagocytic cell is attracted to and recognises microbes as being foreign via surface receptors. It extends filopodia, engulfs the microbe, and early phagosomes begin to form. Once contained in a phagosome, fusion with a digestive enzyme containing lysosome occurs and then breakdown occurs

  

What is chemotaxis?

• chemical attractants (think like signals) released from invading bacteria and tissue leukocytes attract neutrophils, and monocytes from blood stream to go to site of infection

What is diapedesis?

• mast cells and basophils release histamine resulting in blood vessel becoming more permeable allowing for more phagocytes to rush to site of infection

How does diapedesis occur in local infection (example)?

• Example – pathogenic bacteria have evaded the first line of defence and entered tissue. Tissue resident immune cells respond first, releasing chemicals that cause inflammation. Mast cells and basophils release histamine, which increases the permeability of the endothelium. This allows circulating monocytes to follow a chemotactic gradient towards the site of infection (chemotaxis), and reach the tissue by squeezing through small gaps in fine blood vessels (diapedesis). The monocytes can rapidly differentiate into phagocytic tissue macrophages.

What is dendritic cell role in response to infection?

• constantly sample milieu (their local environment) for presence of any foreign antigens

  • use pattern recognition receptors (PPRs) and toll-like receptors (TLRs) to do this

• engulf and digest foreign pathogens that can then be captured by MHC-II proteins that are within the cell

• The MHC-II/pathogen complex travels to the cell surface of the dendritic cell

• the dendritic cell travels to the lymph node where it then interacts with B and T cells

Why did Von Behring win a Nobel prize 1901?

• discovered exposure to toxin = immunity

• serum from B to C = transferred immunity 

• discovered that immunity is only specific to that specific toxin and not to an alternative (animal D)

• mans discovered antibodies and antigens

What is specific immunity?

What are the stages of immune response when immune system comes across pathogen?

• third line of defence

• challenge → recognition → activation → elimination

What is an epitope of an antigen?

How many antibodies can recognise an epitope?

• it is the antigenic determining site that the antibodies can act on

• 1

Are antigens made up of high or low molecular substances

• usually high MW substances e.g. - proteins

What are haptens?

Why do haptens illicit immune response when bound to a carrier molecule?

• Are low MW compounds that can bind to antibodies but don’t illicit an immune response unless they are bound to a carrier molecule

• Because the molecular weight increases

What is urushiol?

How does it illicit a T-cell response?

• it is a hapten from poison ivy

• When urushiols oxidises → product attaches to skin proteins = T-cell reaction results in severe blistering

What antibiotic can act as a hapten to susceptible patients?

• penicillin → leads to anaphylaxis reaction

What is humoral immunity?

Does it act directly or indirectly?

• it is antibody mediated (immunoglobulins and B cells)

• Acts indirectly

Does cell mediated immunity act directly or indirectly?

• acts directly

What is the structure of an antibody?

• variable region (binds specific antigens fragments) (fab)

• Constant region (our cells recognise quickly so don’t get mistaken as pathogens)

• 4 polypeptide chains cross-linked by disulphide bridges

Describe the differences between MADGE immunoglobulins?

How do antibodies eliminate antigens?

• opsonisation → promotion of phagocytes

• Neutralisation

• Complement activation

What does opsonisation result in (in steps)?

• pathogen gets coated by antibodies causing them to be targeted for destruction by macrophages and other cytotoxic cells

• Variable region of antibody binds to pathogen, constant region free

• Constant region Binds to receptors on macrophages and indicate that the pathogen is to be phagocytosed

What does neutralisation result in?

• When serum from a survivor gets transferred to someone else, it allows for the binding and neutralisation of the venom molecules

How do complement proteins get activated to destroy pathogens?

Why does high conc of Ca2+ destroy the cell?

• complement cascade where predecessor cleaves its successor in a chain

• The cleaved pieces assemble together to form a pore, the pore allows high conc of Ca 2+ to accumulate in the cells and destroy them

• Causes an increase in osmotic pressure resulting in cell bursting

What are the 3 lymphocytes involved in cell mediated immunity?

• B cells

  • Stimulated to produce antibodies

  • Can differentiate into plasma cells

  • Mature in the bone marrow

• T cells

  • 2 subtypes → cytotoxic and helper T-cells

  • Mature in the thymus

• Nature killer cells

  • NK cells

  • Kill virus infected/ cancerous cells

Where do B cells mature?

• in the bone marrow (B cell = bone)

Where do T cells mature?

• In the thymus (T = thymus)

What do plasma B-cells produce?

What do memory B-cells lead to?

How are B-cells activated?

• produce antibodies

• Secondary immune response

• Are activated when antigens bind to immunoglobulin receptors on the B cell surface