Name: Citrobacter koseri Frederiksen 1970 (Approved Lists 1980)

Category: Species

Proposed as: sp. nov.

Etymology: ko’se.ri. N.L. gen. masc. n. koseri, of Koser, named after Stewart A. Koser, an American bacteriologist

Pronunciation (Latin), gender: ki-tro-BAK-ter KO-se-ri, masculine

Type strain: ATCC 27028; CCUG 4859; CIP 105014; CIP 82.87; DSM 4570; DSM 4595; JCM 1658; LMG 5519; NCTC 10786

Conduct genome-based taxonomy at

16S rRNA gene: MN095273 Analyse FASTA

Effective publication: Frederiksen W. Citrobacter koseri (n. sp.), a new species within the genus Citrobacter, with a comment on the taxonomic position of Citrobacter intermedium (Werkman and Gillen). Publication of the Faculty of Sciences University, J.E. Purkyne, Brno 1970; 47:89-94.

IJSEM list: Skerman VBD, McGowan V, Sneath PHA. Approved lists of bacterial names. Int J Syst Bacteriol 1980; 30:225-420.

Nomenclatural status: validly published under the ICNP

Taxonomic status: correct name (and explicitly recommended for medical use)

Risk group: 2

• Synonyms:

  • Name	Kind
    "Aerobacter diversum" Burkey 1928	heterotypic synonym, not validly published, basonym of name in Approved Lists
    Citrobacter diversus corrig. (Burkey 1928) Werkman and Gillen 1932 (Approved Lists 1980)	heterotypic synonym, validly published under the ICNP, rejected name
    Levinea malonatica Young et al. 1971 (Approved Lists 1980)	heterotypic synonym, validly published under the ICNP
    Citrobacter diversum (Burkey 1928) Werkman and Gillen 1932 (Approved Lists 1980)	heterotypic synonym, inaccurate spelling and rejected

• Notes:
  • ⏰ According to Brenner et al. (1993), this species is an earlier heterotypic synonym of Levinea malonatica Young et al. 1971 (Approved Lists 1980). Publication: Brenner DJ, Grimont PA, Steigerwalt AG, Fanning GR, Ageron E, Riddle CF. Classification of citrobacteria by DNA hybridization: designation of Citrobacter farmeri sp. nov., Citrobacter youngae sp. nov., Citrobacter braakii sp. nov., Citrobacter werkmanii sp. nov., Citrobacter sedlakii sp. nov., and three unnamed Citrobacter genomospecies. Int J Syst Bacteriol 1993; 43:645-658. 🇺🇸
  • ⏰ According to Frederiksen (1990), this species is an earlier heterotypic synonym of "Aerobacter diversum" Burkey 1928. Publication: Frederiksen W. Correct names of the species Citrobacter koseri, Levinea malonatica, and Citrobacter diversus. Request for an opinion. Int. J. Syst. Bacteriol. 1990; 40:107-108.
  • ⏰ According to Frederiksen (1990), this species is an earlier heterotypic synonym of Citrobacter diversus corrig. (Burkey 1928) Werkman and Gillen 1932 (Approved Lists 1980). Publication: Frederiksen W. Correct names of the species Citrobacter koseri, Levinea malonatica, and Citrobacter diversus. Request for an opinion. Int. J. Syst. Bacteriol. 1990; 40:107-108.
  • ⏰ According to Frederiksen (1990), this species is an earlier heterotypic synonym of Citrobacter diversum (Burkey 1928) Werkman and Gillen 1932 (Approved Lists 1980). Publication: Frederiksen W. Correct names of the species Citrobacter koseri, Levinea malonatica, and Citrobacter diversus. Request for an opinion. Int. J. Syst. Bacteriol. 1990; 40:107-108.
  • 😷 The risk group for Belgium has been imported on 2024-02-05. The full classification is: risk group = 2, note = "human and animal pathogen - biological class of risk animal: 2". — The risk group for Canada has been imported on 2024-02-27. The full classification is: risk group = 2, note = "Animal classification RG: 2 - Security sensitive biological agent: No - Terrestrial animal pathogen under Canadian Food Inspection Agency authority: No - Containment level: Containment Level 2". — The risk group for Swiss Confederation has been imported on 2024-02-01. The full classification is: risk group = 2. — The risk group for Germany has been imported on 2026-08-13. The full classification is: risk group = 2. — The risk group for Taiwan has been imported on 2024-11-03. The full classification is: risk group = 2, note = "P650 = v". — If in doubt, use the risk group given in the regulations for your country and, if these are not available, use the risk group given in the catalogue of the culture collection from which you have obtained or intend to obtain the strain.
  • 🎓 Name mentioned 359 times in PubMed until 2026-06-11.
  • 🙆 This name is on the List of Recommended Names for bacteria of medical importance (LoRN) as the name to be applied to this species. The name is on LoRN because of the recorded risk group of the species itself.
  • 🧍 According to Bartlett et al. (2022), this species is an established human pathogen. Publication: Bartlett A, Padfield D, Lear L, Bendall R, Vos M. A comprehensive list of bacterial pathogens infecting humans. Microbiology (Reading) 2022; 168:0. 🇬🇧

Parent taxon: Citrobacter Werkman and Gillen 1932 (Approved Lists 1980)

Assigned by: Frederiksen W. Citrobacter koseri (n. sp.), a new species within the genus Citrobacter, with a comment on the taxonomic position of Citrobacter intermedium (Werkman and Gillen). Publication of the Faculty of Sciences University, J.E. Purkyne, Brno 1970; 47:89-94.

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Record number: 774752