This document defines various microbiology terms related to infection. It discusses pathogens, opportunistic pathogens, parasites, commensals, and saprophytes. It also describes different types of infections like primary, secondary, focal, nosocomial, and iatrogenic infections. Modes of transmission are discussed including contact, inhalation, ingestion, and inoculation. Sources of infection from humans, animals, insects, soils, water, and food are outlined. Finally, it briefly touches on types of infectious diseases like endemic, epidemic, pandemic, and sporadic.

1. INFECTIONA MICROBIOLOGY TOPIC

2. DEFINITIONS INFECTIONINFECTIOUS DISEASEPARASITECOMMENSALSPATHOGENOPPORTUNISTIC PATHOGEN

3. SAPROPHYtEFree-living microbes that live on dead or decaying matter.PARASITEMicrobes that can establish themselves and multiply in hostsCommensalMicrobes that live with the host in complete harmony without causing any damage.Eg: streptococcus salivarius E. coli

4. Opportunistic pathogenPathogen that is normally safe but when host’s immunity is lowered, thay can be dangerous.Eg: bacilllusbactillus streptococcus sp.

5. Types of infectionPrimaryReinfectionSecondaryFocal infectionNosocomial infectionIatrogenic infectionEndogenous ExogenousInapparent/subclinicalAtypicalLatentLocalSystemic

6. Primary infectionExposure of pathogen for the first timeReinfectionExposure of the same pathogen for second or many times.SecondaryInfected by a pathogen, immunity lowered and cause invasion by other pathogen

7. Focal infectionLocalised infectionNosocomial infectionA person make a hospital visit, immunity is low, and get infected by hospital microbes.Eg: wound sepsis

8. Iatrogenic infectionDrug induced infection during course of treatmentEg: muscle sepsis caused by unsterilized equipment used.Endogenous infectiomWhen a commensal enter places it should not be.Eg: entrance of E. coli to urinary tract cause infection.Exogenous infectionWhen a pathogen comes from other sourceEg: soil

9. Inapparent /subclinicalAsymptomaticAtypical infectionSymptoms are atypicalLatent infectionParasites remains in tissues in latent or hidden form, proliferating and producing clinical disease when the host resistance is lowered.Eg: herpes infection

10. Systemic infectionSpread throughout the bodyEg: streptococcus infection

11. Source of infectionHumanAnimalVectorsInsects Food, water, soil

12. From humanCarrier- a person who harbours the pathogenic microorganism without suffering any ill effect because of it.Types of carrierHealthy carrier- never get infected.Convalescent carrier- the one that recovered from the disease.Temporary carrier- <6 monthsChronic carrier- several years or the rest of the life

13. PatientContact carrier- someone who acquires pathogen from a patient.Paradoxical carrier-someone who acquires pathogen from a carrier.AnimalsZoonoses-infectious disease transmitted from animals to humansZoonoses could beBacterial (plague from rats)Viral (rabies from dogs)Protozoal (toxoplasmosis from cats)Helminthic (hydatid disease from dogs)Fungal (zoophilicdermatophytes from cats and dogs)

14. InsectsArthropod-borne disease-disease cause by blood sucking insects.Vectors- insects like mosquitoes, ticks, mites, flies, fleas, and lice.Types of vectorsMechanical vectors- transmission of dysentry by fliesBiological vectors- anopheles mosquito in malaria“Extrinsic incubation period”Time of entry of the pathogen into the vector and the vector becoming infective.

15. SoilsHas fungi(eg: histoplasmacapsulatum) and parasites(eg: hookworm, roundworm)WaterContaminated with pathogenic microbesEg: cholera vibrio, infective hepatitis virusFoodContaminated due to external contamination or pre-existent infection in meat or othe animal product.

16. Modes of infectionContactDirectIndirectInhalationIngestionInoculationCongenital transmission

17. Types of infectious diseaseEndemic-constantly present in particular areaEpidemic- spreads rapidly and infect many persons in an area at a time.Pandemic- epidemic that spreads through many areas of the world, very large number of persons in short period.Prosodemic- creeping and smouldering epidemicsSporadic