MCEM Part A Study Guide/Microbiology/Principles of Microbiology/Principles of Investigation

Specimen Types

Specimen Culture Specimens are often "cultured" or grown in order to increase the quantity of pathogen and hence facilitate detection. The "media" that the pathogen is grown in can be either solid or liquid. Solid media facilitates the separation of different microbes, whereas liquid media will facilitate faster growth.

Specimen Examination Microbes can be detected by visualisation - usually aided by a microscope and possibly staining. Direct - Stool - parasites Gram - CSF - Bacteria Z-N - Sputum - Tuberculosis Giemsa - Blood - Malaria Fluorescent - Sputum - Respiratory Syncytial Virus

Serology Serological testing relies on detecting a host immune response to a pathogen. It relys on rising or falling levels of antibodies in serial specimens. Specific pathogen antigens can also be detected. eg. bacterial capsular antigens in CSF Nucleic Acid Amplification is also used to detect specific nucleic acid sequences present in slow growing pathogens.