Systematic Bacteriology 2

Question 1

What does a Microbiome include?

Answer 1

endogenous microorganisms
Exogenous - (not normal flora)
Includes potential pathogens
Community as a whole increasingly linked to health and disease.

Question 2

What is Pathogenesis?

Answer 2

Parasitic life cycle.
Adhere/Colonize and invade
Evade host defences
Multiply/Complete its life cycle
Exit the host
(host is damaged)
(Some are considered suicide pathogens as by killing their host, they destroy their habitat)
(Pathogens sometimes change the behaviour of their host to complete their life cycle).

Question 3

What it the definition of Virulence?

Answer 3

The capacity of a microbe to cause damage to the host.

Question 4

What is the definition of pathogen?

Answer 4

A harmful organism that produces a pathology

Virulence, and virulence factors.

Question 5

What is the definition of commensal?

Answer 5

An organism that is aprt of the normal flora.
Often mutualistc relationship.
Endogenous

Question 6

What is the definition of an opportunistic pathogen?

Answer 6

An organism that causes infection whenopportunity/ change in atural imuity arises.
E.g. in an immunocompromised individual.

Question 7

What is the definition of contaminant?

Answer 7

An organism that is growing in a culture by accident.

Question 8

What are the different types of infectious Agents?

Answer 8

Bacter
Viruses
Fungi
Protozoa
Parasites
Prions

Question 9

What are Bacteria?

Answer 9

Prokaryotic, single celled organisms

Question 10

What are viruses?

Answer 10

Non-living, obligate parasites

Question 11

What are Fungi?

Answer 11

Eukaryoic single to multi-cellular infectious agents

Question 12

What are Protozoa?

Answer 12

Amoeba, Plasmodium (malaria), Taxoplasma

Question 13

What are Prions?

Answer 13

Infectious proteins, nvCJD and BSE (cattle)

Question 14

How can fungal infections be treated?

Answer 14

Limited number of targets for anti-mycotic/fungal drugs.

Candida, linked with thrush, can be linked with antibiotic therapy.

Question 15

What are some examples of Protozoan diseases of man?

Answer 15

Leishmaniasis
- 150 million affected
Malaria
- 3.3 billion
Taxoplasma
- 2 billion
GI infections
- Cryptosporidiosis, EntAmeobosis

Question 16

What are common infectious gram negative bacteria Prokaryotic pathogens?

Answer 16

Neisseris spp

Escheria spp

Question 17

What are common infectious gram positive bacteria prokaryotic pathogens?

Answer 17

Streptococcus spp
Staphylococcus spp
Enterococcus spp.
Clostridium

Question 18

What are gram negative cocci and what are some examples and what infections are they responsible for?

Answer 18

Aerobic Gram negative cocci.
Appear in pairs (diplococci) on gram film.
10 species of which 2 pathogenic;
- Neisseria meningitidis. Commonest cause of bacterial meningitis
- Neisseria gonorrhoeae. Causes gonorrhoea, a sexually transmitted infection

Question 19

Why is Meningitis an important disease in my age group?

Answer 19

Meningitis C vaccine.
Increase in meninitis - 22 to 209 by 2015 (6yrs)
- MenACWY Vaccine introduced
Meningitis B significant
- Drop 74 to 37 cases in under 1 year olds in 10 months after new vaccine.

Question 20

What Gram-negative bacteria are associated with the GI tract?

Answer 20

Gut commensal coliforms (normal bowel flora)
- Most strains of Escherichia coli
- Klebsiella spp.
- Enterobacter spp.
- Proteus spp. and many others
Significant gut pathogens
- Salmonella app
- Shigella spp
- Verotoxin (VTEC) producing Escherichia coli
  -E.coli 0157
  - E.coli 0104

Question 21

What are Coliforms and how do they differentiate from each other?

Answer 21

(Sub group within the Enterobacteriaceae).
“Coliform”; term used to describe species of gram negative bacilli that look like Escherchia coli (E.coli) on gram film and when cultured on blood agar.
Grow best aerobically but can also grow anaerobically.
Many of them are par of normal bowel flora.
differentiate from each other by:
- Biochemical reactions
- Antigenic structure of cell wall (serotyping) - O antigens (cell wall) and H antigen (flagella)

Question 22

What is an example of a coliform that causes an infection in humans and what is the 1st line antibiotic used for the treatment of infections caused by coliforms?

Answer 22

N.B. any coliform that gets into a normally sterile site can cause serious infection, for example:
- urinary tract infection
- Peritonitis
- Biliary tract infection
Gentamicin is the 1st line antibiotic used for the treatment of infectious caused by coliforms.
Patients with coliform (gram-negative) sepsis become very unwell very quickly because of the endotoxin released from the gram negative cell wall when the bacteria die.

Question 23

What is the Mechanism of Fever Production?

Answer 23

Antigen (component of micro-organisms or lipopolysaccharide (endotoxin) interact with macrophages (WBC).
Macrophages release cytokines into the bloodstream.
Cytokines travel to the anterior hypothalamus (brain).
Cytokines also stimulate the adverse effects of sepsis or Prostoglandin E is released, which increases the body’s thermal set point.
After the Prostoglandin is released the body now perceives that it is cold and starts to “shiver” to conserve heat.
Fever.
Increased survival from infection.

Question 24

When is the boy considered to have a fever and what are the positives and negatives of fever?

Answer 24

“Normal” body (core) temperature is considered to be 37C.
Fever is defined as temp >38C.
Most human pathogens grow best at 37C -growth starts to slow if temp increases.
Raising the core temperature is an adaptive response and is considered to be beneficial in fighting infection.
However, harm may also result from fever - e.g. febrile convulsion in young children.

Question 25

What is sepsis and what is the process by which sepsis occurs?

Answer 25

A host response to severe infection. Small blood vessels become "leaky" and lose fluid into the tissues. Lower blood volume requires heart to work harder to maintain oxygenation of tissues (increases HR). Poor tissue oxygen perfusion mean blood supply to less essential organs (skin, kidneys, liver is shut down to try to maintin blood supply to brain). Blood clotting system is activated causing blood clotting in tiny blood vessels -> uses up all clotting factors -> increased risk of haemorrhage.

Question 26

What are some examples of Gram-positive pathogens?

Answer 26

``` Streptoccus - pneumonia, GAS Enterococcus - Enteric infections Staphylococcus - Nosocomial and community - skin infctions and biofilms Clostridia (Clostridioides) - Anaerobic bacilli ```

Question 27

What is Streptococcus pneumoniae "pneumococcus"?

Answer 27

Gram positive alpha-haemolytic cocci - short chains or pairs Part of normal upper respiratory tract flora in many people. Commonest cause of pneumonia - also causes severe form of meningitis. 90+ different capsular types - vaccine available that immunises against the commonest 23 types. Majority of UK strains are still sensitive to penicillin.

Question 28

What are examples of different infections and what are some signs of each?

Answer 28

``` S.aureus - 20% colonisation - anterior names and perimeum - nosocomial and community S.epidermidis - 100% colonisation - Skin and mucou membranes - nosocomial infection-immunocompromised - associated with foreing devices e.g. catheters MRSA - mainly nosocomial - elderly and immunocompromised - intensive care units - burns patients - surgical patients - intravenous lines - dialysis patients ```

Question 29

What are Clostridioides?

Answer 29

Gram positive anaerobic bacilli. Part of normal bowel flora of man and animals - found in faeces and in soil. - Produces spores that can survive outside the body for many months. - Produce (exo) toxins that cause severe tissue damage - Clostridium difficile- causes antibiotic-associated diarrhoea esp. in the elderly. - Clostridium pefringens - causes "gas" gangrene, a severe soft tissue infection following contamination of wound. - Clostridium tetani - causes tetanus, a usually fatal paralytic illness.

Question 30

What is Clostridium difficile?

Answer 30

Pseudomembraneous colitis. 1-3% adults carriers of organism or inactive spores. 20% of hospitalised patients are carriers. Link to antibiotic therapy - C. difficile proliferates in obsence of normal flora.

Question 31

what are Endotoxins and Cytokines?

Answer 31

Outer membrane of Gram negative bacteria - Assymetric membrane - Lipopolysaccharides (LPS) - Peptidoglycan - Lipoteichoic acid (LTA) - Lipoproteins - Bind to receptors on macrophages, B cells & other cells that stimulates release of acute phase cytokines.

Question 32

What is Endotoxin shock?

Answer 32

Systemic Inflammatory Response Syndrome (SIRS) Peptoglycan and Endotoxin or Lipopolysacharide (LPS) activate macrophages. Exotoxins Superantigens (e.g. TSST-1) activate T-cells. Macrohpages and T-cells release inflammatory cytokines.

Question 33

As the severity of the infection increases, how does the host's response adapt?

Answer 33

Infection Sepsis Severe sepsis Septic shock

Question 34

what is Streptococcal Haemolysis and what are the different types?

Answer 34

N.B. Haemolysis is ONLY important for the classification of Streptoccocci. Alpha-Haemolysis = partial haemolysis - Caused by enzymes that denature the haemoglobin inside the red blood cells causing greenish discolouration round the colony. Beta-haemolysis = complete haemolysis - Caused by enzymes that lyse (breakdown) red blood cells causing complete cleaning round the colony. The most pathogenic Streptococci are beta-haemolytic. Gamma-haemolysis = no haemolysis.

Question 35

What is Group A streptococcus and what diseases are associated with it?

Answer 35

(Most significant Pathogenic Streptococci) Numerous types of associated diseases - Steptococcus pyogenes - Beta-haemolytic - Streptococcal sore throat (Scarlet fever) - Invasive diseases e.g. necrotising fasciitis - Puerperal sepsis (infection of pregnant and post natal women) 700 million cases world wide

Question 36

What is the definition of Pneumonia?

Answer 36

An acute inflammation of the lungs, often caused by inhaled pneumococci of the species Streptococcus pneumoniae. The alveoli and bronchioles of the lung become plugged with a fibrous exudate.

Question 37

What is non-haemolytic Streptococci?

Answer 37

Most important group is the Enterococci - Enterococcus faecalis - Enterococcus faecium Part of the normal bowel flora. Not particularly pathogenic, but can cause problems if they get into a normally sterile site, e.g. - Common cause of urinary tract infection. Most strains of E.faecalis are sensitive to amoxicillin (but not to penicillin) Some very antibiotic-resistant strains of E.faecium "VRE" (vancomycin resistant enterococci) can cause "outbreaks" of infections in hospital.

Question 38

What rules do Staphylococci normally follow?

Answer 38

``` Gram +ve. Non-motile. Irregular grape like clusters. Aerobe + facultative anaerobe. Catalase +ve. (usually). Oxidase -ve. Coagulase +ve or -ve. Tolerate 15% NaCl ```

Question 39

What is S.aureus infections and what are it's classic signs ?

Answer 39

Commonest cause of skin, soft tissue and wound infection. Commonest cause of bone and joint infection. Food poisoning - enterotoxin-producing strains only. Multiples at site of acquisition, causing local infection and inflammation, e.g. abscess. Gets into bloodstream. Bacteraemia (SAB). Disseminates to distant sites in the body. Sepsis (septicaemia) life threatening. May cause abscesses in spleen, liver, kidneys etc.

Question 40

List of Pathogens, what is on the list?

Answer 40

``` Nomenclature - Pathogen, virulence, cycle o infection - Microbiome Pathogens - Viruses, Fungi (e.g. Candida), Protozoa (e.g. Malaria) Symptoms - Sepsis and Fever Key Gram-negative Pathogens - Neisseria spp (STD/STI & Meningitis) - Escherichia coli (GI Tract) Gram-positive Pathogens & GI Tract - Streptococcus spp., Staphylococcus spp. & C.difficile. ```