TABLE 6.

Characteristics defining a new Qnr allele/gene

New Qnr element	Characteristic(s)
	Requisiteb	Discardc	Optionald	Not considered
Allelea	Natural source	Synthetic origin	Increase in MICe	Promoter alterations
	Full-length sequence	Partial sequence		Silent mutations
	Amino acid change
	Identity of >70% (same ancestor)f
Geneg	Identity of ≤70% (same ancestor)f	No effect on MIC		Promoter alterations
	Increase in MICe			Silent mutations

^aWithin a defined qnr gene. Allele numeration will be assigned after submission to the qnr repository (https://www.ncbi.nlm.nih.gov/pathogens/submit-beta-lactamase). Similarly, prior to defining a new qnr gene, it needs to be submitted to the qnr repository. Note that the website manager may not perform continuous surveillance of the thousands of new articles published monthly or the innumerable new sequences added to GenBank. Researchers need to act responsibly and ask for an allele assignation prior to any publication and should not pirate or appropriate an allele number in an irresponsible manner, which only contributes to increasing confusion and a lack of trust in publishing results. Similarly, it would be of great interest for journals to ask authors about previous submission to an internet repository to use the numeration provider by the curator, in order to reinforce the use of correct nomenclature.

^bAll these characteristics are needed to classify a new qnr allele/gene.

^cCharacteristics invalidating the description of a new qnr allele/gene.

^dDesirable but not essential.

^eEffect on any quinolone MIC.

^fTransferable Qnr genes are named “Qnr” followed by a letter (e.g., QnrA). Chromosomal Qnr should be named with the initials of the microorganism followed by “Qnr” (e.g., accordingly, qnr from Photobacterium profundum should be named Ppqnr for the DNA and PpQnr for the protein). In addition, it was proposed that if a chromosomal Qnr has at least 70% identity to one of the established transferable qnr families, it may be named according to transferable or chromosomal name rules (e.g., SaQnrA3, where Sa represents Shewanella algae). Usually, the latter consideration is applied only for proposed original bacterial sources of established transferable qnr families.

^gThe qnr nomenclature rules published in 2008 (319) considered the presence of either a DNA or amino acid identity difference of ≥30% as a requisite to define a new gene. While this has been considered a general rule, in 2017 qnrB88 was renamed qnrE1 because its original source (Enterobacter instead of Citrobacter) was taken into account (176), classifying a new gene irrespective of having an amino acid identity of ∼85% with established QnrB alleles, including QnrB1.