INFECTION

Definition :-

➡The lodgment and multiplication of a parasite in or on the tissue a host constitute.

• Infection :-

 Based on relationship of m. orgs & their host organism can be classified as.

               1] Saprophytes.

               2] Parasites.

• Related term’s :-

• Commensal’s :- No harm.

• Pathogen :- capable for producing disease.

• Opportunistic Pathogens :-

• Can produce disease when host resistance is lowered.

• Pathogenicity :-

• Ability of org’s to produce disease.

• Virulence :-

• Degree of pathogenicity of microbe.

• Types of Infection :-

1] Primary Infection – Initial infection.

2] Reinfection – Subsequent infection with same org’s.

3] Secondary Infection – Lower body resistance – new parasite set up.

4] Cross Infection – Already infected + New infection from another host / external source.

5] Nosocomial Infection – Cross infection acquired in hospital.

6] Iatrogenic Infection – Physical induced infection.

7] Subclinical Infection – Clinical symptom’s of an infection are not apparent.

8] Latent Infection – Parasite latent in host & clinical disease produce when host resistance lowered.

9] Reservoir – Any human being, animal, plant, soil in which parasite normally lives, multiplies & depends primary for its survival.

• Source of Infection –

1] Endogenous Source – Self body flora.

2] Exogenous Source – 

  a] Human

  b] Animal’s

  c] Insect

  d] Soil & wonder

  e] Food

 A] Human – Patient or carrier’s

• Carrier’s :- Person who harbor's the pathogenic micro – organism’s without suffering any ill effect because of it.

        i] healthy carriers 

       ii] convalescent carriers.

  B] Animal’s – Called zoonotic disease.

• Bacterial – Plague

• Viral – Rabbis

• Protozoal – Toxoplasmosis

• Helminthic – Hydatid disease

• Fungal – Zoophilic dermatophytes

 C] Insect’s – Blood sucking insect’s such as mosquito, mites, ticks, files, lice.

• Mosquito – malaria

• Tick – Relapsing fever etc.

 D] Soil & Water –

• Soil – Spore of Cl. tetani & Cl. perfrengens.

• Water – Hepatitis virus & V. cholera

 E] Food – Contaminated food acts as source of infection in case of food poisoning, gastroenteritis etc. diarrhea & dysentery.

• Method’s of transmission of disease –

 1] Contact –

            a] Direct – S.T.D. such as syphilis, gonorrhea.

            b] Indirect – Through agency of fomites, such as                                            clothing, toy’s etc.

 2] Inhalation – Influenza, Tuberculosis.

 3] Ingestion – By ingestion of food or drink contaminated by pathogen.

 4] Inoculation – Rabbis – bite of rabid animals.

 5] Insect’s – Mechanical & Biological vectors.

 6] Congenital – Some pathogen’s are able to cross the placental barrier & infect the fetus in uteri.

 7] Iatrogenic & Laboratory Infection – During administration of injection lumbar puncture, catheterization.

Factors Predisposing to Microbial Pathogenicity –

• Exaltation - Virulence

• Attenuation - Virulence

1. Adhesion – Attachment of bacteria to body surface. The adhesive structures are named adhesions. Adhesions usually occure as pili or colonisation factors.

2. Invasiveness – Reefer's to ability of an org’s to spread within the host tissue.

• High invasive – Generalised infection

• Less invasive – Localised infection

 3.Antiphagocytic Factors –

 1] Capsule -

 2] Streptococcal M protein— bind—Fibrinogen to fibrin –Mask bacterial receptors from compliment

 3] Cytotoxin –Haemolysin – damage RBC’s & WBC’s.

 4] Bacterial Surface Antigen’s – K Ag of E-coli resis phagocytosis.

Types of infectious disease :-

1] Localise – There is an acute inflammatory reaction at site of invasion.

2] Generalised –

a] Bacteremia – Circulation of bacteria

b] Septicemia – Circulation of bacteria & multiplication of bacteria & toxin production.

c] Pyaemia – Pyogenic bacteria produce septicemia.