Developed over 100 years ago, Koch's postulates is no longer used to determine etiologic agents of human infectious diseases. True False

True

Explanation:

Koch's postulates was proposed to show a causative relationship between a microbe and a disease.

Koch's postulates

•The microorganism must be present in large quantity in all organisms affected by the disease, but should not be seen in healthy organisms.

Koch abandoned this due to his discovery of asymptomatic carriers of cholera and of typhoid fever. Asymptomatic or subclinical infection carriers are seen in diseases, especially viral diseases.

•The microorganism must be seperated from a diseased organism and nutured in pure culture.

This can suspended for specific microorganisms or entities which(at the current time) can't be nutured in pure culture. Viruses uses host cells to grow and replicates and not in pure culture.

•The cultured microorganism should lead to disease when it infects a healthy organism.

It says "should", not "must".

NOTE: NOT ALL organisms introduced to an infectious agent will be infected which may be due to certain factors like general health and good immune functioning; vaccination; or genetic immunity. Its best explained using the resistance to malaria as a result of presence of at least one sickle cell allele.

•The microorganism must be reisolated from the inoculated, diseased experimental host and observed as being identical to the basic specific causative agent.

A single pathogen may lead to several disease conditions. A singualr disease infection may be due to several different microorganisms. While some pathogens cannot be cultured in a pure culture in the lab, others can infects humans.

blood enters the heart through two large veins, the inferior and superior vena cava, emptying oxygen-poor blood from the body into the right atrium of the heart. as the ventricle contracts, blood leaves the heart through the pulmonic valve, into the pulmonary artery and to the lungs where it is oxygenated.