Normal Flora Flashcards
(34 cards)
How do humans associate with microorganisms?
– 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
What is COLONIZATION and how does it develop?
– 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
What are Normally Colonized Body Sites and examples?
- 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
What are Body Sites that are not Normally Colonized?
• internal tissues not in contact with the environment
– blood
– brain
– muscle
– bone
What are normal body flora?
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
How can normal flora be classified?
CLASSIFCATION OF NORMAL FLORA
- 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
How can normal flora be classified?
CLASSIFCATION OF NORMAL FLORA
- 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
What are the FACTORS INFLUENCING THE TYPE OF MICROBES AT ANY ANATOMIC SITE?
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
BENEFICIAL EFFECTS OF NORMAL BODY FLORA
- Synthesis vitamins-enteric bacteria secrete Vitamin K and Vitamin B12, and lactic acid bacteria produce certain B-vitamins
- Prevention of colonization by pathogens
- Antagonism & killing of other
bacteria-Bacteriocin production - Stimulation of the development of certain tissues-caecum and certain lymphatic tissues (Peyer’s patches) in the GI tract
- Stimulation of the production of natural antibodies.- IgA, cross-reacting
What is cross reaction?
A situation here an antibody produced in response to a specific antigen binds sign another antigen
What are the HARMFUL EFFECTS OF NORMAL BODY FLORA?
- Bacterial synergism
- Competition for nutrients
- Induction of a low grade toxaemia
- Agents of disease= Opportunistic Pathogens
- Transfer to susceptible hosts
What is the CLINICAL SIGNIFICANCE OF NORMAL FLORA?
• 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
What is Pathogenesis?
Pathogenesis is a series of changes occurring between contact with an infective agent and manifestation of a disease
What is Pathogenicity?
- Pathogenicity is the ability to produce disease in a host organism
What is a Pathogen?
- is a microorganism, macroorganism or foreign body capable of infecting & inducing a disease upon contact with a susceptible host
What is Pathology?
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
Virulence
is the degree of pathogenicity of the microbe
Invasiveness
Invasiveness is the ability of microbes to penetrate deep into host cell/tissues
Toxigenesis
Toxigenesis is the ability to produce toxins
Attributes of Pathogenic Organisms
- Transmittability
- Adhesiveness
- Invasiveness
- Toxigenicity
- Host immune system evasion
- Production of host tissue degrading enzymes
What is Transmittability?
The ability of infectious microorganisms to move from a colonized, infected or reservoir host to a new susceptible host
What are the modes of transports for pathogens?
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
Maintenance of Transmittability
- Animal Reservoir
- Common vehicle-water, food, fomites
- Human carrier-asymptomatic state
- Common portal of entry-mouth, ears, airways, genitalial opening
- Clinical symptom-sneezing, coughing
What is ADHERENCE?
Ability of the micro organisms to attach to host cells and tissue
