Editing Shigella (section)

== Classification ==
''Shigella'' species are classified by three [[serotype|serogroups]] and one [[serotype]]:
* Serogroup ''A'': ''[[Shigella dysenteriae|S. dysenteriae]]'' (15 serotypes)<ref>{{cite journal |last1=Ansaruzzaman |first1=M |last2=Kibriya |first2=AK |last3=Rahman |first3=A |last4=Neogi |first4=PK |last5=Faruque |first5=AS |last6=Rowe |first6=B |last7=Albert |first7=MJ |title=Detection of provisional serovars of ''Shigella dysenteriae'' and designation as ''S. dysenteriae'' serotypes 14 and 15 |journal=Journal of Clinical Microbiology |volume=33 |issue=5 |pages=1423–5 |year=1995 |pmid=7615772 |pmc=228185 |doi= 10.1128/JCM.33.5.1423-1425.1995}}</ref>
* Serogroup ''B'': ''[[Shigella flexneri|S. flexneri]]'' (9 serotypes)<ref>{{cite journal |last1=Knirel |first1=Y. A. |last2=Sun |first2=Q |last3=Senchenkova |first3=SN |last4=Perepelov |first4=AV |last5=Shashkov |first5=AS |last6=Xu |first6=J |s2cid=7360433 |title=O-Antigen Modifications Providing Antigenic Diversity of Shigella flexneri and Underlying Genetic Mechanisms |journal=Biochemistry (Moscow) |volume=80 |pages=901–914 |year=2015 |issue=7 |doi=10.1134/S0006297915070093 |pmid=26542003 |doi-access=free }}</ref>
* Serogroup ''C'': ''[[Shigella boydii|S. boydii]]'' (19 serotypes)<ref>{{cite journal |last1=Yang |first1=Z |last2=Hu |first2=C |last3=Chen |first3=J |last4=Chen |first4=G |last5=Liu |first5=Z |title=A new serotype of Shigella boydii |language=zh |journal=Wei Sheng Wu Xue Bao |volume=30 |issue=4 |pages=284–95 |year=1990 |pmid=2251827 }}</ref>
* Serogroup ''D'': ''[[Shigella sonnei|S. sonnei]]'' (one serotype){{citation needed|date=May 2021}}

Groups ''A''–''C'' are physiologically similar; ''S. sonnei'' (group ''D'') can be differentiated based on biochemical metabolism assays.<ref name=Baron>{{cite book |last1=Hale |first1=Thomas L. |last2=Keusch |first2=Gerald T. |year=1996 |chapter=Shigella |chapter-url=https://www.ncbi.nlm.nih.gov/books/NBK8038/ |editor1-last=Baron |editor1-first=Samuel |title=Medical microbiology |publisher=University of Texas Medical Branch |location=Galveston, Texas |pmid=21413292 |isbn=978-0-9631172-1-2 |edition=4th }}</ref> Three ''Shigella'' groups are the major disease-causing species: ''S. flexneri'' is the most frequently isolated species worldwide, and accounts for 60% of cases in the developing world; ''S. sonnei'' causes 77% of cases in the developed world, compared to only 15% of cases in the developing world; and ''S. dysenteriae'' is usually the cause of epidemics of dysentery, particularly in confined populations such as refugee camps.<ref name="WHO shigellosis">{{cite book |title=State of the art of new vaccine research and development |series=Immunization, Vaccines and Biologicals |publisher=World Health Organization |year=2006 |chapter-url=http://apps.who.int/iris/bitstream/10665/69348/1/WHO_IVB_06.01_eng.pdf |archive-url=https://web.archive.org/web/20150927050701/http://apps.who.int/iris/bitstream/10665/69348/1/WHO_IVB_06.01_eng.pdf |archive-date=2015-09-27 |url-status=live |chapter=Shigellosis |pages=10–2 }}</ref>

Each of the ''Shigella'' genomes includes a virulence [[plasmid]] that encodes conserved primary virulence determinants. The ''Shigella'' [[chromosome]]s share most of their genes with those of ''E. coli'' K12 strain MG1655, a well-studied model strain.<ref name=Yang2005>{{cite journal |first1=Fan |last1=Yang |first2=Jian |last2=Yang |first3=Xiaobing |last3=Zhang |first4=Lihong |last4=Chen |first5=Yan |last5=Jiang |first6=Yongliang |last6=Yan |first7=Xudong |last7=Tang |first8=Jing |last8=Wang |first9=Zhaohui |last9=Xiong |first10=Jie |last10=Dong |first11=Ying |last11=Xue |first12=Yafang |last12=Zhu |first13=Xingye |last13=Xu |first14=Lilian |last14=Sun |first15=Shuxia |last15=Chen |first16=Huan |last16=Nie |first17=Junping |last17=Peng |first18=Jianguo |last18=Xu |first19=Yu |last19=Wang |first20=Zhenghong |last20=Yuan |first21=Yumei |last21=Wen |first22=Zhijian |last22=Yao |first23=Yan |last23=Shen |first24=Boqin |last24=Qiang |first25=Yunde |last25=Hou |first26=Jun |last26=Yu |first27=Qi |last27=Jin |title=Genome dynamics and diversity of ''Shigella'' species, the etiologic agents of bacillary dysentery |journal=Nucleic Acids Research |volume=33 |issue=19 |pages=6445–58 |year=2005 |pmid=16275786 |pmc=1278947 |doi=10.1093/nar/gki954 }}</ref>

[[Phylogenetics|Phylogenetic]] studies indicate ''Shigella'' is more appropriately treated as a subgroup of ''[[Escherichia]]''<ref>{{Cite journal |last1=Chaudhuri |first1=Roy R. |last2=Henderson |first2=Ian R. |date=2012-03-01 |title=The evolution of the Escherichia coli phylogeny |url=https://www.sciencedirect.com/science/article/pii/S1567134812000068 |journal=Infection, Genetics and Evolution |language=en |volume=12 |issue=2 |pages=214–226 |doi=10.1016/j.meegid.2012.01.005 |pmid=22266241 |bibcode=2012InfGE..12..214C |issn=1567-1348}}</ref> (see ''[[Escherichia coli#Diversity]]'' for details).