Infection- Classification, Types, Diagnosis, Features

Talks about different types of infections.

1. Immunology and Medical Microbiology

2. INFECTION Definition: The invasion and multiplication of microorganisms such as bacteria, viruses, and parasites that are not normally present within the host body. Vasculitis Bacterial infection Conjunctivitis Middle ear infection

3. HOST PATHOGEN/MICROBES INFECTION Interaction Microbes Saprophytes Parasites Free living microbes and live on dead and decaying matter Found in soil and water Play important role in degradation of organic matter in nature Don’t multiply on living animals Multiply and establish inside the host Pathogen Commensals Produces diseases in the host Does not Produce diseases in the host Produces disease when host immune system goes low Classification of microbes based on interactions

4. Classification of Infection 1. Primary Infection- Initial infection of a pathogen inside the host. Eg. , Typhoid 2. Reinfection- Subsequent infection by the same parasite in the host. Eg .,Typhoid 3. Secondary infection – New parasite sets up infection in a host whose resistance is lowered by a preexisting infectious disease Eg. , Amoebic dysentery in a patient with Typhoid 4. Focal Infection – Due to localized infection , a generalized effect is produced. Eg. , Sepsis in tonsils produce fever. 5. Cross Infection – When a patient is suffering from a disease and a new infection is set up from another host Eg. , Patient with Typhoid is getting infection from TB patient or a getting Malarial Infection

5. Classification of Infection 6. Nosocomial Infection – Cross infection occurring in the hospitals. Eg. , Typhoid patient gets TB from hospital 7. Iatrogenic Infection – Physician induced infection Eg. , Unhygenic practices 8. Endogenous or Exogenous Infection- Infection from the host’s own body or from external sources 9. Inapparent/ Subclinical Infection – Clinical effects are not apparent Eg. , Typhoid Mary who didn’t show any clinical symptoms though she carried the pathogen 10. Atypical Infection – Characteristic clinical manifestations of a particular infectious disease is not present Eg. , Walking pneumonia which is associated with not one single pathogen but many pathogens like Staphylococcus pneumoniae, Haemophilus influenzae and Moraxella sp. 11. Latent Infection – Parasite, after infection, remains hidden from proliferating and produces clinical disease when the host resistance is lowered. Eg. , HIV infection Abscess caused by Staphylococcus aureus

6. SOURCES OF INFECTION 1. Humans Human Carriers Person who harbour the pathogen Healthy Carrier Harbour the pathogen Never suffered from the disease caused by the pathogen Convalescent Carrier Recovered from the disease Continues to harbour the pathogen Contact Carrier Person who acquires the pathogen from a patient Paradoxial Carrier Carrier who acquires pathogen from another carrier Classification of carriers depending on the duration of carriage Temporary Carrier Carriage state lasts less than six months Chronic Carriage Carrier state lasts for several years even for the rest on one’s life

7. SOURCES OF INFECTION 2. Animals Maintain the parasite in nature Reservoir Host They carry the pathogen Symptomatic or Asymptomatic

8. ZOONOSES : Infectious diseases transmitted from animals to human Zoonotic diseases Bacterial: Plague from rats Viral: Rabies from dogs Protozoal: Toxoplasmosis from cats Helminthic: Hydatid disease from dogs Fungal: Zoophilic dermatophytes from cats and dogs Yersinia pestis rabies virus Echinococcus  granulosus (dog tapeworm) Toxoplasma Tinea corporis (ringworm) 

9. SOURCES OF INFECTION 3. insects Arthropod Diseases Diseases transmitted by insects which carry pathogens Insects are called VECTORS Transmission of Typhoid Bacilli by domestic fly Transmission of malaria though Anopheles mosquito

10. Extrinsic Incubation Period (EIP) The interval between the time of entry of the pathogen into the vector and the vector becoming infective is called EIP Dengue virus Transmission

11. 4. Soil & Water Clostridium tetani Neurotoxin tetanospasmin –enters through wound and causes muscle spasm Enterotoxin affects intestine and cause   diarrhoea Vibrio cholerae

12. 5. food External contamination Pre existing Infection Staphylococcal food poisoning Salmonellosis through infected animal or meat