Chapter 1 - Bacteria

Question 1

Leading causes of death globally

Answer 1

non communicable disease accounted for 74% of deaths globally

Question 2

Most deadly communicable disease

Answer 2

Lower respiratory infections

Question 3

Neonatal

Answer 3

less than 28 days old

Question 4

Leading causes of death in low-income countries

Answer 4

People living in a low-income country are far more likely to die of a communicable disease than a non-communicable disease

Question 5

Bacterial diseases: Terminology

Answer 5

1. Encounter: the agent “meets” the host
2. Entry: the agent enters the host’s body (or remains on the skin)
3. Multiplication: the agent multiplies in the host
4. Spread:the agent spreads from the site of entry (for some)
5. Damage: the agent, the host response, or both cause damage
6. Outcome: the agent or host wins out, or they learn to co-exist

Question 6

Infection

Answer 6

pathogen colonizes the body (but not necessarily causes disease)

Question 7

Colonize

Answer 7

becomes part of the microbiota, maybe transient, maybe permanent

Question 8

Disease

Answer 8

overt symptoms caused by infection, impairment of the host - causes damage

Question 9

Pathogen

Answer 9

bacterium capable of harming a healthy host

Question 10

Opportunistic Pathogen

Answer 10

harms a weakened or immunocompromised host, but not a healthy host

Question 11

Pathogenicity

Answer 11

The ability of an organism to cause disease and represents a genetic component of the pathogen (qualitative). - cannot be calculated

The overt damage done to the host is a property of the host-pathogen interactions

Disease is not an inevitable outcome of the host pathogen-interaction

Pathogens can express a wide range of virulence

Question 12

Virulence

Answer 12

The degree of pathology caused by the organism (quantitative) - can be calculated

The extent of the virulence is usually correlated with the ability of the pathogen to multiply within the host and may be affected by other factors

Pathogens may exhibit different levels of virulence

Question 13

Virulence is a quantitative concept, so we must be able to quantify it in some way.

Answer 13

ID50 and LD50

Question 14

Virulence factors

Answer 14

Gene products that enable bacterium to establish itself within or on a host and enhance its potential to cause disease

eg toxins, flagella

Question 15

Would the same number of bacteria cause disease regardless of its portal entry into the body?? → aka does route of entry effect its virulence/matter

Answer 15

Not necessarily, if bacteria are ingested much more is sully needed to cause disease

If bacteria are injected into the blood steam, much less is needed to cause disease

The bacteria would have to overcome host’s physiological anatomical defences

Question 16

If a species of bacteria are pathogenic to mice, would they also be pathogenic to humans?

Answer 16

depends
- could cause different diseases or not at all

A bacterium may be a pathogen to mice, but be part of the microbiota of a different species of host.

Question 17

Host susceptibility

Answer 17

Host susceptibility varies between individuals:

• underlying disease/infection
• stress
• diet
• Age

altered immune system due to disease or therapy

Hosts genetics and resistance genes (eg TLRs

microbiota plays a role
- creates competition

Question 18

Risk factors for disease that you might have some control over include:

Answer 18

• nutritional status

- Environmental conditions

Question 19

Streptococcus pyogenes

Answer 19

Causes numerous disease in humans include:

Pharyngitis - strep throat
Tonsillitis
Scarlet fever
Cellulitis
Rheumatic fever

Question 20

Streptococcus pyogenes

Answer 20

This bacteria species is found on skin and mucous membrane of healthy people - thus an opportunistic pathogen

Question 21

What is Streptococcus pyogenesknown for?

Answer 21

Bacterium can cause both non-invasive and invasive types of infections

The bacterium causes skin diseases when there is a breach in the skin or mucus membrane and the bacteria enter the tissue

The other bacteria of the microbiota may keep it “in check”
-meaning that the number of bacteria present in the body is controlled
-

Question 22

Primary infection

Answer 22

Initial infection event, may or may not lead to disease

Question 23

Secondary Infection

Answer 23

Opportunistic organism causes a second infection following a primary infected
- infects weakened host

Question 24

Subclinical Infection

Answer 24

No obvious symptoms

Question 25

Nosocomial infection

Answer 25

Acquired in a hospital/medical clinic setting (e.g., a complication of a reason for being in the hospital)

eg C. difficile infections

Question 26

Local infection

Answer 26

Common type of infection

is restricted to a relatively small area of the body.

Non-invasive organisms usually cause these infections

These organisms express virulence factors –but tend to cause less severe disease (they may be highly contagious)

These infections are usually managed with antimicrobial compounds ( eg antibiotics)

Question 27

Systemic infection

Answer 27

Spread throughout the body. This is a less common types of infection

Invasive organisms usually cause these infections

The bacteria are found in normally sterile body fluids (e.g.,blood, joint fluid, cerebrospinal fluid) or a deep tissue abscess (e.g., muscle or fat)
- uses the circulatory system to spread

The pathogen possess (and expresses) virulence factors that enable it to spread throughout the body
These types of infections are extremely serious and sometimes difficult to treat (i.e.treatment might lead to complications for the patient)