microbiology:

Question 1

classification of microorganisms

Answer 1

• NORMALFLORA:
  The microorganisms that establish permanent residence (colonise), but
  do not produce disease under normal
  conditions.

•TRANSIENT FLORA:
The microorganisms that are present on host for hours, days or months, then disappear.

• OPPORTUNISTIC PATHOGENS:
Do not cause disease in their normal habitat in a healthy person, but are ]potentially pathogenic organisms.

•PARASITISM: Microbes benefit at
the expense of the host.

Question 2

normal flora - a special relationship with human hosts:

Answer 2

Human bodies have up to 10 (14) microorganisms on external and internal surfaces
• Most are commensal bacteria (those that benefit from the host, but the host does not gain any advantage)
• Affected by illness, stress, diet, antibiotic therapy, immunosuppression etc

Question 3

opportunistic infections

Answer 3

Transient micro flora may cause infections
when:
• The host’s immune system is weakened
• They are present in unusual sites
• The normal flora of a site is disturbed

Compromised  Host-one  whose  resistance to infection is  impaired.
Four main conditions can compromise a
host:
•Broken skin or mucous membranes
• A suppressed immune system
• Impaired cell activity
• Extremes of age

Question 4

Pathogens, pathogenicity and virulence:

Answer 4

PATHOGEN: Disease causing
microorganism/s
• Pathogens have specific characteristics
that enable them to cause infections

PATHOGENICITY: The ability to cause disease
• Pathogenicity is the 
ability of a 
pathogen to disrupt 
the 
host’s  normal functions and invade, 
causing disease

VIRULENCE
:The measure of the degree to which a given pathogen is able to cause disease
- Virulence refers to the severity or intensity of the disease caused by the
pathogen

Question 5

Spread of infection:

Answer 5

• Reservoirs of Infection: A living organism
or inanimate object that provides adequate conditions for survival, multiplication and
the opportunity for transmission of a pathogen.

1. Human Reservoirs
2. Animal Reservoirs
3. Non-living Reservoirs

Question 6

Transmission of disease:

Answer 6

• Contact

• Direct: Requires close association between infected and susceptible host.
• Indirect: Spread by cloths, rags, mops
etc.
• Droplet: Transmission via airborne
droplet
• Vehicle
• Transmission by an inanimate reservoir (food,water)
• Vectors
• Anthropods, especially fleas, ticks and mosquitoe

Question 7

Bacteria:

Answer 7

• Bacteria is prokaryotic and single cellular
organism
• Produce disease in one of two general ways:
• Destroy living cells and tissues
of the infected organsm.
• Release toxins (poisons) that interfere with the normal activity of the host cell.

Question 8

viruses:

Answer 8

-Acellular, not living cell, extremely small, only see with an electron microscope, not with a light microscope.
- Can replicate (grow) only when inside host cell.
- Depend totally on
host cell formetabolism