OXA-1 is OXA-30 is OXA-1

Sir, Recently while perusing articles on the Journal of Antimicrobial Chemotherapy Advance Access web page (Author Webpage) the correspondence from Mendonça et al.,1 ‘CTX-M-15, OXA-30 and TEM-1-producing Escherichia coli in two Portuguese regions’, caught our attention. The authors point out that apart from their report, this particular combination of β-lactamase genes had only been reported in Salmonella strains from Senegal.2 Mendonça et al. also referenced reports of the combination of blaCTX-M-15, blaOXA-1 and blaTEM-1 having been found in strains from the UK, India and Canada. When blaOXA-30 was initially characterized in 2000 a single amino acid difference was noted between the presumptive enzyme and OXA-1, and hence the authors correctly named it OXA-30.3,4 OXA-30 contained a Gly-128 whereas OXA-1 contained an Arg-128.3,4 In Canada it was the plasmid pC15-1a characterized in our lab that contained the blaCTX-M-15, blaOXA-1 and blaTEM-1 combination.5 During our characterization of pC15-1a, BLAST searches of the GenBank database with our sequence data revealed the presence of the blaCTX-M-15, blaOXA-30 and blaTEM-1 genes. When we received the editor's and reviewer's responses to the original manuscript describing the characterization of pC15-1a, one reviewer pointed out that OXA-30 is in fact identical to OXA-1 and referred us to Sun et al.6 (published in 2003) in which the crystallographic structure of OXA-1 was presented. Admittedly, we had no knowledge of that report. In that work the data did not support the presence of Arg-128 and they reported that the authors of the original report on the sequence of blaOXA-1 confirmed a sequence error in the originally published DNA sequence, such that OXA-1 did in fact contain a Gly-128.6 The crystallographic data were generated from an enzyme produced from a cloned blaOXA-1 gene from plasmid RGN238 which was also the source of the original DNA sequence data; hence, together these data confirm a Gly-128 in OXA-1.4,6 Thus, the originally published sequence of blaOXA-30 was in fact blaOXA-1 though Siu et al.3 could not have known this at the time. We note that of a total of 11 entries in the GenBank database containing blaOXA-1, blaOXA-1-like or blaOXA-30, the cognate enzymes are all identical and contain a Gly-128 except for the originally published OXA-1 sequence (accession no. J02967), which surprisingly has not been updated. Thus, even if the genes contain sequence variations, which we did not check for, they are all blaOXA-1 variants. The appearance in the literature of two enzyme names for an identical enzyme is confusing and we encourage all authors to update their GenBank submissions that refer to blaOXA-30. In this way, future occurrences of OXA-1 will be correctly identified. Undoubtedly, as was the case for us, many molecular biologists may not regularly read papers concerned with the crystallographic structure of proteins, and as far as we can discern the paper by Sun et al. is the only source in which the correct sequence of blaOXA-1 is referenced. None to declare.

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