systemic bacteriology 2

Question 1

what is a microbiome

Answer 1

community or its associated genetic material associated with host during health or disease. Includes potential pathogens

Question 2

what is pathogenesis

Answer 2

endogenous bacteria shifting to a parasitic lifecycle requires adaptation. Colonize and invade – evade host defences – complete life cycle – exit host. Host is damaged

Question 3

what is a pathogen

Answer 3

a harmful organism that produces a pathology. Virulence, & virulence factors

Question 4

commensal/mutualism/symbiosis

Answer 4

an organism that is part of the normal flora. often mutualistic relationship. endogenous

Question 5

opportunistic pathogen

Answer 5

an organism that causes infection when opportunity/change in natural immunity arises

Question 6

what is containment

Answer 6

an organism that is growing in a culture by accident

Question 7

what is virulence

Answer 7

the capacity of a microbe to cause damage to the host

Question 8

aerobic gram negative cocci

Answer 8

appears in pairs (diplococci) on gram film. 10 species, 2 pathogenic. N.meningitidis and N.gonnorrhoea

Question 9

which gram negative bacteria is normal bowl flora in GI tract

Answer 9

escherichia coli

Question 10

definition of coliforms

Answer 10

term used to describe species of Gram-negative bacilli that look like Escherichia coli (E. coli) on Gram film and when cultured on blood agar. part of normal flora

Question 11

characteristics of coliforms

Answer 11

• Grow best aerobically but can also grow anaerobically
• Many of them are part of normal bowel flora

Question 12

how do coliforms cause infection

Answer 12

• Any coliform that gets into a normally sterile site can cause serious infection for example; UTI, peritonitis, biliary tract infection

Question 13

where are endotoxins and cytokines present

Answer 13

outer membrane of gram -ve bacteria

Question 14

what is sepsis

Answer 14

a host response to severe infection

Question 15

how does sepsis occur

Answer 15

• Small blood vessels become “leaky” and lose fluid into the tissues
• Lower blood volume requires heart to work harder to maintain oxygenation of tissues (↑HR)
• Poor tissue oxygen perfusion means blood supply to less essential organs (skin, kidneys, liver is shut down to try to maintain 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
• Symptoms include fever production

Question 16

how does fever effect pathogens

Answer 16

• Fever is defined as temp >38oC
• Most human pathogens grow best at 37oC * growth starts to slow if temp increases
• Raising the core temperature is an adaptive response and is beneficial in fighting infection
• However, harm may also result from fever

Question 17

range of host response to infection

Answer 17

Infection > sepsis > severe sepsis > septic shock

Question 18

common gram positive pathogens

Answer 18

• Streptococcus, enterococcus, staphylococcus, clostridia
• Streptococcus is the most significant

Question 19

how is pneumonia caused

Answer 19

• 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 20

what is Streptococcus pneumoniae

Answer 20

• Gram positive haemolytic cocci
• Part of normal upper respiratory tracts flora in many people
• Most common cause of pneumonia
• 90+ different types, vaccine available to fight 23
• Majority of strains are sensitive to penicillin

Question 21

what is non haemolytic streptococci

Answer 21

• Most important group is the Enterococci
• Part of the normal bowel flora
• Not particularly pathogenic, but can cause problems if they get into a normally sterile site,
• Common cause of urinary tract infection
  Most strains sensitive to amoxicillin