View source for Medicine:Citrobacter koseri

{{Short description|Species of bacterium}}
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| genus = Citrobacter
| species = koseri
| authority = Frederiksen 1970<ref name=Citrobacter-koseri>{{cite web|title=Species ''Citrobacter koseri'' |url=https://lpsn.dsmz.de/species/citrobacter-koseri|website=LPSN|access-date=21 April 2023}}</ref>
| synonyms = * ''Citrobacter diversus''<br />{{small|(Burkey 1928)<br />Werkman & Gillen 1932}}<ref name=Citrobacter-koseri/>
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'''''Citrobacter koseri''''', formerly known as '''''Citrobacter diversus''''', is a Gram-negative non-spore forming, rod-shaped bacterium.  It is a facultative anaerobe capable of aerobic respiration. It is motile via peritrichous flagella.<ref name="pmid20576143">{{cite journal |vauthors=Ong CL, Beatson SA, Totsika M, Forestier C, McEwan AG, Schembri MA |title=Molecular analysis of type 3 fimbrial genes from Escherichia coli, Klebsiella and Citrobacter species |journal=BMC Microbiol. |volume=10 |pages=183 |year=2010 |pmid=20576143 |pmc=2900259 |doi=10.1186/1471-2180-10-183 |doi-access=free }}</ref>  It is a member of the family of [[Biology:Enterobacteriaceae|Enterobacteriaceae]]. The members of this family are part of the normal flora and commonly found in the digestive tracts of humans and animals.{{ref}}  ''C. koseri'' may act as an opportunistic pathogen in individuals who are immunocompromised.<ref>{{Cite journal |last1=Pennington |first1=Kelly |last2=Van Zyl |first2=Martin |last3=Escalante |first3=Patricio |date=6 October 2016 |title=Citrobacter koseri Pneumonia as Initial Presentation of Underlying Pulmonary Adenocarcinoma |journal=Clinical Medicine Insights: Case Reports |language=en |volume=9 |pages= 87–89|doi=10.4137/CCRep.S40616 |issn=1179-5476 |pmc=5054941 |pmid=27746678}}</ref>

It rarely is community-acquired and mainly occurs as [[Medicine:Hospital-acquired infection|hospital-acquired infection]]s. Infections caused by C. koseri can lead to various symptoms, including fever, chills, diarrhea, and abdominal pain. In severe cases, the bacterium can cause sepsis, meningitis, or brain abscesses. [[Medicine:Brain abscess|Brain abscess]]es have a high rate of mortality and complications, particularly in neonates. The transmission of'' C. koseri'' could be [[Biology:Vertical transmission|vertical]] from mother to fetus, and other sources can be [[Medicine:Horizontal transmission|horizontal]] by asymptomatic nursery staff.<ref>{{cite book |first1=David |last1=Greenwood |first2=Richard C. B. |last2=Slack |first3=John F. |last3=Peutherer |first4=Michael R. |last4=Barer |title=Medical Microbiology: A Guide to Microbial Infections: Pathogenesis, Immunity, Laboratory Diagnosis and Control |url=https://books.google.com/books?id=CLauNkxnSgsC&pg=PT1264 |date=2007 |publisher=Elsevier |isbn=978-0-7020-4009-2 |pages=1264–6 |edition=17th}}</ref>

==Signs and symptoms==
Neonates infected with ''C. koseri'' usually present with sepsis, meningitis, seizures, apnea, and a bulging fontanelle. No evidence of a stiff neck or high-grade fever is present.<ref name=Babyn11/>

===Complications===
Occasionally, it causes meningitis, but it can cause sepsis and [[Medicine:Ventriculitis|ventriculitis]].<ref name=Babyn11>{{cite book |first=Paul S. |last=Babyn |title=Teaching Atlas of Pediatric Imaging |chapter=Section I: Neuroradiology: Case 3 |chapter-url=https://books.google.com/books?id=3Aisi2p9J9IC&pg=PT44 |date=2011 |publisher=Thieme |isbn=978-1-60406-494-0 |pages=44–7}}</ref>

Arterial and venous infarctions are possible because of the bacterial infiltration along the main vessel; exudates within the ventricles and ventriculitis may obstruct the ventricular foramina and result in multicystic hydrocephalus with consequent long-lasting shunting difficulties and necrotizing meningoencephalitis with pneumocephalus has been reported.<ref name=Babyn11/>

===Pathogenicity===
The pathogenic mechanism is poorly understood. ''C. koseri'' may uniquely penetrate, survive, and replicate into vascular endothelial cells and macrophages. Furthermore, it survives in phagolysosomal fusion and replicates within macrophages, which may contribute to the establishment of chronic abscesses.<ref name=Babyn11/><ref name=Doran99>{{cite journal |author=Doran TI |title=The role of Citrobacter in clinical disease of children: review |journal=Clin. Infect. Dis. |volume=28 |issue=2 |pages=384–94 |year=1999 |pmid=10064257 |doi=10.1086/515106 |doi-access=free }}</ref>

==Diagnosis==

===Medical imaging===
Early and massive tissue necrosis is a specific feature of ''C. koseri'' brain infection. The early stage of the disease predominates in the white matter, causing cerebritis; the later stage is marked with necrotic cavities in multiple locations. The cavities are initially square and not tense, but when pus forms and collects in these cavities, they tend to become more rounded; a persisting cavity leads to septated ventriculitis that may result in multicystic hydrocephalus.<ref name=Babyn11/>

Early cerebritis is seen, and multiple large cavities can be seen in the late stage of the disease; abscesses formation, contraction of the cavities, and hydrocephalus due to ventriculitis are observed in the late follow-up.<ref name=Babyn11/><ref name=Doran99/>

===Pathology===
Macroscopic findings include purulent exudates, opaque leptomeninges (thinning of meninges), pus, and ventriculitis/ ependymitis.

===Microbiology===
In samples collected from cerebrospinal fluid, ''C. koseri'' grows well on any ordinary medium; they produce unpigmented, colorless mucoid colonies. If incubated for 24 hours in other media such as indole, citrate, and adonitol, ''C. koseri'' will be positive, hydrogen sulfide negative in Kligers’ iron agar, and negative results in lactose, salicin, and sucrose broth as well.<ref name=Babyn11/><ref name=Feferbaum00>{{cite journal |vauthors=Feferbaum R, Diniz EM, Valente M, Giolo CR, Vieira RA, Galvani AL, Ceccon ME, Araujo MC, Krebs VL, Vaz FA |title=Brain abscess by ''Citrobacter diversus'' in infancy: case report |journal=Arq Neuropsiquiatr |volume=58 |issue=3A |pages=736–40 |year=2000 |pmid=10973119 |doi=10.1590/s0004-282x2000000400023|doi-access=free }}</ref>

===Histology===
''Citrobacter koseri'' may be identified in the walls of congested vessels; the presence of the cavities resulting from the infection does not develop a well-formed fibrotic wall.<ref name=Babyn11/>

===Differential diagnosis===
The differential diagnosis of ''C. koseri'' brain abscesses can be confused with other related diseases, so diagnostic imaging is essential to confirm this bacterium. The significant feature of ''C. koseri'' is the necrotic cavity which cannot be misidentified as an earlier ischemic or hemorrhagic insult or other mass lesions; congential/neonatal tumors are uncommon (choroid plexus papillomas, craniopharyngiomas, teratomas); even when they present, they are different from the inflammatory ring of cerebral infection. Early cerebritis should not be mistaken for normal, immature white matter, nor cicatricial leukomalacia.<ref name=Babyn11/><ref name=Doran99/>

==Treatment==
A broad spectrum  [[Chemistry:Cephalosporin|cephalosporin]] and [[Chemistry:Meropenem|meropenem]]  are often used because of the good penetration into the central nervous system. If the response to the antibiotic is poor, the surgical aspiration of the collected pus reduces the mass effect and enhances the efficacy of the antibiotics.<ref name=Babyn11/><ref name=Feferbaum00/><ref>{{cite journal |vauthors=McPherson C, Gal P, Ransom JL |title=Treatment of ''Citrobacter koseri'' infection with ciprofloxacin and cefotaxime in a preterm infant |journal=Ann Pharmacother |volume=42 |issue=7 |pages=1134–8 |year=2008 |pmid=18577764 |doi=10.1345/aph.1L008 |s2cid=12607380 }}</ref>

==Prognosis==
The prognosis of the ''C. koseri ''infection is 20 to 30% of neonates die, and 75% of survivors have significant neurologic damage such as complex hydrocephalus, neurologic deficits, mental delay, and epilepsy.<ref name=Babyn11/>

==Control==
The most effective way to reduce transmission of organisms is regular handwashing.<ref name=Babyn11/>

==References==
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* {{cite web |title=''Citrobacter koseri'' |work=NCBI Taxonomy Browser |url=https://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Info&id=545 |id=545}}
* [http://bacdive.dsmz.de/index.php?search=4329&submit=Search Type strain of ''Citrobacter koseri'' at Bac''Dive'' -  the Bacterial Diversity Metadatabase]

{{Gram-negative proteobacterial diseases}}
{{Taxonbar|from=Q5122841}}

[[Category:Citrobacter|koseri]]

{{Sourceattribution|Citrobacter koseri|1}}