Editing Infection (section)

===Microbial culture===
[[File:K pneumoniae M morganii providencia styphimuriuma.JPG|thumb|200px|Four [[nutrient agar]] plates growing colonies of common [[Gram negative]] bacteria]]
Many diagnostic approaches depend on [[microbiological culture]] to isolate a pathogen from the appropriate clinical specimen.<ref>{{cite book |last1=Murray |first1=Patrick R. |title=Medical Microbiology |date=2021 |publisher=Elsevier |location=Philadelphia |isbn=978-0-323-67450-8 |edition=9th |chapter=Laboratory Diagnosis of Bacterial Diseases}}</ref> In a microbial culture, a [[growth medium]] is provided for a specific agent. A sample taken from potentially diseased tissue or fluid is then tested for the presence of an infectious agent able to grow within that medium. Many pathogenic [[bacteria]] are easily grown on nutrient [[Agar#Microbiology|agar]], a form of solid medium that supplies carbohydrates and proteins necessary for growth, along with copious amounts of water. A single bacterium will grow into a visible mound on the surface of the plate called a [[Colony (biology)|colony]], which may be separated from other colonies or melded together into a "lawn". The size, color, shape and form of a colony is characteristic of the bacterial species, its specific genetic makeup (its [[Strain (biology)|strain]]), and the environment that supports its growth. Other ingredients are often added to the plate to aid in identification. Plates may contain substances that permit the growth of some bacteria and not others, or that change color in response to certain bacteria and not others. Bacteriological plates such as these are commonly used in the clinical identification of infectious bacterium. Microbial culture may also be used in the identification of [[virus]]es: the medium, in this case, being cells grown in culture that the virus can infect, and then alter or kill. In the case of viral identification, a region of dead cells results from viral growth, and is called a "plaque". [[Eukaryotic]] [[parasites]] may also be grown in culture as a means of identifying a particular agent.<ref>{{Cite journal |last1=Joyce |first1=Bradley R. |last2=Queener |first2=Sherry F. |last3=Wek |first3=Ronald C. |last4=Sullivan |first4=William J. |date=2010-10-05 |title=Phosphorylation of eukaryotic initiation factor-2α promotes the extracellular survival of obligate intracellular parasite Toxoplasma gondii |journal=Proceedings of the National Academy of Sciences of the United States of America |volume=107 |issue=40 |pages=17200–17205 |doi=10.1073/pnas.1007610107 |issn=0027-8424 |pmc=2951449 |pmid=20855600|bibcode=2010PNAS..10717200J |doi-access=free }}</ref>

In the absence of suitable plate culture techniques, some microbes require culture within live animals. Bacteria such as ''[[Mycobacterium leprae]]'' and ''[[Treponema pallidum]]'' can be grown in animals, although serological and microscopic techniques make the use of live animals unnecessary. Viruses are also usually identified using alternatives to growth in culture or animals. Some viruses may be grown in [[embryo]]nated eggs. Another useful identification method is Xenodiagnosis, or the use of a vector to support the growth of an infectious agent. [[Chagas disease]] is the most significant example, because it is difficult to directly demonstrate the presence of the causative agent, ''[[Trypanosoma cruzi]]'' in a patient, which therefore makes it difficult to definitively make a diagnosis. In this case, [[xenodiagnosis]] involves the use of the [[Vector (epidemiology)|vector]] of the Chagas agent ''T. cruzi'', an uninfected [[Triatominae|triatomine]] bug, which takes a blood meal from a person suspected of having been infected. The bug is later inspected for growth of ''T. cruzi'' within its gut.<ref>{{Cite journal |last1=Elliot |first1=Simon L. |last2=Rodrigues |first2=Juliana de O. |last3=Lorenzo |first3=Marcelo G. |last4=Martins-Filho |first4=Olindo A. |last5=Guarneri |first5=Alessandra A. |date=2015 |title=Trypanosoma cruzi, etiological agent of Chagas disease, is virulent to its triatomine vector Rhodnius prolixus in a temperature-dependent manner |journal=PLOS Neglected Tropical Diseases |volume=9 |issue=3 |pages=e0003646 |doi=10.1371/journal.pntd.0003646 |issn=1935-2735 |pmc=4368190 |pmid=25793495 |doi-access=free }}</ref>