Normal Flora

Question 1

How do humans associate with microorganisms?

Answer 1

– Colonization: host tolerates the microbe, Normal Flora

– Elimination: killing or removal of the microbe, requires a defence system (immune system)

– Infection: pathological harm to the host becomes evident as microbes invades host tissue- Pathogenesis/Pathology

Question 2

What is COLONIZATION and how does it develop?

Answer 2

– the presence of microorganisms at any body site without evident disease
– Starts at birth
– Follows:
•contact with the birth canal & feeding •contact with others, environment & surfaces

Question 3

What are Normally Colonized Body Sites and examples?

Answer 3

• surface tissues constantly in contact with the environment eg. skin
• Surfaces lined with mucous membranes:
  – conjunctiva
  – nose
  – external ear
  – nasopharynx
  – axilla
  – mouth
  – large intestine
  – anterior urethra
  – vagina

Question 4

What are Body Sites that are not Normally Colonized?

Answer 4

• internal tissues not in contact with the environment
– blood
– brain
– muscle
– bone

Question 5

What are normal body flora?

Answer 5

Aka colonizers

• NORMAL BODY FLORA is the mixture of microorganisms regularly found at certain anatomical sites in the body of all healthy /normal person

• The microbes are not associated with diseases
• They colonize certain anatomical body sites
• aka-
– normal microbial flora
– indigenous microbiota

Question 6

How can normal flora be classified?

Answer 6

CLASSIFCATION OF NORMAL FLORA

1. Based on duration of association with the anatomical site
   a. Transient b. Permanent

Based on relationship to the host:
2.a) Mutualism (Symbiotic)-Both host and bacteria are thought to derive benefit from each other

b) Opportunistic- normal flora in their host cause endogenous diseases as a result of weakness in the host defences or transfer to a different body site

c) Commensal- no apparent benefit or harm to either organism following their association

Question 7

How can normal flora be classified?

Answer 7

CLASSIFCATION OF NORMAL FLORA

1. Based on duration of association with the anatomical site
   a. Transient b. Permanent

Based on relationship to the host:
2.a) Mutualism (Symbiotic)-Both host and bacteria are thought to derive benefit from each other

b) Opportunistic- normal flora in their host cause endogenous diseases as a result of weakness in the host defences or transfer to a different body site

c) Commensal- no apparent benefit or harm to either organism following their association

Question 8

What are the FACTORS INFLUENCING THE TYPE OF MICROBES AT ANY ANATOMIC SITE?

Answer 8

FACTORS INFLUENCING THE TYPE OF MICROBES AT ANY ANATOMIC SITE
Human factor:
– genetics
– age
– Sex
– Stress
– nutrition and diet
– Temperature
–pH
– Hormonal state

Microbial factor:
– Tissue tropism (Lactobacilus)
– Specific adherence
– Biofilm formation

Question 9

Q BENEFICIAL EFFECTS OF NORMAL BODY FLORA

Answer 9

1. Synthesis vitamins-enteric bacteria secrete Vitamin K and Vitamin B12, and lactic acid bacteria produce certain B-vitamins
2. Prevention of colonization by pathogens
3. Antagonism & killing of other
   bacteria-Bacteriocin production
4. Stimulation of the development of certain tissues-caecum and certain lymphatic tissues (Peyer’s patches) in the GI tract
5. Stimulation of the production of natural antibodies.- IgA, cross-reacting

Question 10

What is cross reaction?

Answer 10

A situation here an antibody produced in response to a specific antigen binds sign another antigen

Question 11

Q What are the HARMFUL EFFECTS OF NORMAL BODY FLORA?

Answer 11

1. Bacterial synergism
2. Competition for nutrients
3. Induction of a low grade toxaemia
4. Agents of disease= Opportunistic Pathogens
5. Transfer to susceptible hosts

Question 12

Q What is the CLINICAL SIGNIFICANCE OF NORMAL FLORA?

Answer 12

• Difficulty in interpretation of culture results
• Applicable specimens
– throat swab
– eye swab
– urogenital specimens
– skin and ulcer specimen
– sputum
– nasopharygeal and nasal specimen
– faeces and rectal swabs
– Urine
• Knowledge of patients clinical condition is vital

Question 13

What is Pathogenesis?

Answer 13

Pathogenesis is a series of changes occurring between contact with an infective agent and manifestation of a disease

Question 14

What is Pathogenicity?

Answer 14

• Pathogenicity is the ability to produce disease in a host organism

Question 15

What is a Pathogen?

Answer 15

• is a microorganism, macroorganism or foreign body capable of infecting & inducing a disease upon contact with a susceptible host

Question 16

What is Pathology?

Answer 16

Pathology
– Morphological changes, indicative of deviation from normal, seen in an infected/diseased tissues/organ

– A branch of medicine, study of processes and changes seen in an infected/diseased tissues/host

Question 17

Virulence

Answer 17

is the degree of pathogenicity of the microbe

Question 18

Invasiveness

Answer 18

Invasiveness is the ability of microbes to penetrate deep into host cell/tissues

Question 19

Toxigenesis

Answer 19

Toxigenesis is the ability to produce toxins

Question 20

Q Attributes of Pathogenic Organisms

Answer 20

1. Transmittability
2. Adhesiveness
3. Invasiveness
4. Toxigenicity
5. Host immune system evasion
6. Production of host tissue degrading enzymes

Question 21

Q What is Transmittability?

Answer 21

The ability of infectious microorganisms to move from a colonized, infected or reservoir host to a new susceptible host

Question 22

What are the modes of transports for pathogens?

Answer 22

Contact
Direct
Indirect

Droplet
large particle droplets (> 5 microns) generated during coughing, sneezing, talking or tracheal suctioning,
pneumonias, pertussis, diphtheria, influenza type B, mumps, and meningitis

Airborne
Evaporated droplet <5 micron, remain suspended in the air for long periods of time
Pulmonary tuberculosis (TB), measles, chicken pox, pulmonary plague and haemorrhagic fever with pneumonia

Common vehicle transmission
food, water, therapeutic devices, hospital equipment

Question 23

Maintenance of Transmittability

Answer 23

1. Animal Reservoir
2. Common vehicle-water, food, fomites
3. Human carrier-asymptomatic state
4. Common portal of entry-mouth, ears, airways, genitalial opening
5. Clinical symptom-sneezing, coughing

Question 24

What is ADHERENCE?

Answer 24

Ability of the micro organisms to attach to host cells and tissue

Question 25

TYPES OF ADHERENCE

Answer 25

Nonspecific adherence Specific adherence

Question 26

Nonspecific adherence

Answer 26

reversible attachment of the bacterium to the eucaryotic cell surface (sometimes called "docking") involves nonspecific attractive forces which allow approach of the bacterium to the eucaryotic cell surface hydrophobic interactions electrostatic attractions atomic and molecular vibrations resulting from fluctuating dipoles of similar frequencies Brownian movement recruitment and trapping by biofilm polymers interacting with the bacterial glycocalyx (capsule)

Question 27

Specific adherence

Answer 27

Irreversible, permanent attachment of the microorganism to the eucaryotic cell surface (sometimes called "anchoring") involves permanent formation of specific lock-and-key bonds between complementary molecules on each cell surface Complementary receptor and adhesin molecules must be accessible and arranged in such a way that many bonds form over the area of contact between the two cells.

Question 28

What is INVASIVENESS?

Answer 28

The ability of microorganisms to penetrate the host cells or tissues, penetration beyond the point of attachments

Question 29

Types of invasiveness?

Answer 29

Active - induced by the pathogen: Neisseria gonorrhoea Passive- induced by the host cell/ tissue: Listeria monocytogen Actin internalin

Question 30

What is TOXIGENICITY?

Answer 30

The ability to produce toxins

Question 31

Toxin

Answer 31

substances produced by microbes with lethal effects on eukaryotic cells

Question 32

Types of Bacterial Toxins

Answer 32

Exotoxins are released from bacterial cells and may act at tissue sites or remote from the site of bacterial growth Endotoxins (aka- Endotoxin, LPS ) are cell-associated substance.    released from growing bacterial cells and lysed cells (lysozyme, antibiotics)

Question 33

What is HOST IMMUNE SYSTEM EVASION?

Question 34

Possible Q Types of HOST IMMUNE SYSTEM EVASION

Answer 34

1. Antigenic heterogeneity 2. Antigenic variation a. Antigenic drift b. Antigenic shift 3. Capsule production 4. IgA protease production 5. Prevention of intracellular killing a. Avoiding entry into vagosome b. Avoiding phagosome-lysosome fusion c. Inactivation of lysosomal enzymes d. Development of resistance to lysosomal enzymes