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Emended description of porcine [Pasteurella] aerogenes, [Pasteurella] mairii and [Actinobacillus] rossii

Henrik Christensen¹, Peter Kuhnert², Magne Bisgaard¹, Reinier Mutters³, Francis Dziva^4, and John Elmerdahl Olsen¹

¹ Department of Veterinary Microbiology, The Royal Veterinary and Agricultural University, Stigbøjlen 4, 1870 Frederiksberg C, Denmark
² Institute of Veterinary Bacteriology, University of Bern, Laenggass-Strasse 122, Bern, Switzerland
³ Institut für Medizinische Mikrobiologie und Krakenhaushygiene, Philipps-Universität, Marburg, Germany
⁴ University of Zimbabwe, Harare, Zimbabwe

Correspondence
Henrik Christensen
henrik.christensen{at}vetmi.kvl.dk

The aim of this study was to improve the definition and identification of a group of veterinarily important bacteria referred to as the [Pasteurella] aerogenes–[Pasteurella] mairii–[Actinobacillus] rossii complex. These organisms have mainly been isolated from the reproductive and intestinal tracts of pigs and in most cases have been considered as opportunistic pathogens. A collection of 87 strains were characterized by phenotypic analysis from which 41 strains were selected for 16S rRNA gene sequence comparison, out of which 23 have been sequenced in the present study. One group of 21 strains phenotyped as biovars 1, 3–5, 9–11, 19 and 25–27, including the type strain of [P.] aerogenes, showed 16S rRNA gene sequence similarities of 99·6 % or higher; another group of 18 strains including biovars 2, 6–8, 12–15, 21, 23, 24 and 26A and the type strain of [A.] rossii showed 97·8 % or higher 16S rRNA gene sequence similarity. Between the two groups, 93·8–95·7 % 16S rRNA gene sequence similarity was observed. Strains of [P.] mairii showed 99·5 % similarity, with 95·5–97·2 and 93·8–95·5 % similarity to strains of [P.] aerogenes and [A.] rossii, respectively. Four strains could not be classified with any of these groups and belonged to other members of Pasteurellaceae. Comparisons were also made to DNA–DNA hybridization data. Biovars 1, 9, 10, 11 and 19, including the type strain of [P.] aerogenes, linked at 70 % DNA reassociation, whereas strains identified as biovars 2, 6, 7, 8, 12, 15 and 21 of [P.] aerogenes linked at 81 %. The latter group most likely represents [A.] rossii based on the 16S rRNA gene sequence comparisons. DNA reassociation between the [P.] aerogenes and [A.] rossii groups was at most 37 %, whereas 47 % was the highest DNA reassociation found between [P.] aerogenes and [P.] mairii. The study showed that [P.] aerogenes, [P.] mairii and [A.] rossii can not be easily separated and may consequently be misidentified based on current knowledge of their phenotypic characteristics. In addition, these taxa are difficult to separate from other taxa of the Pasteurellaceae. A revised scheme for separation based upon phenotypic characters is suggested for the three species [P.] aerogenes emend., [P.] mairii emend. and [A.] rossii emend., with the respective type strains ATCC 27883^T, NCTC 10699^T and ATCC 27072^T.

The GenBank/EMBL/DDBJ accession numbers of 16S rRNA gene sequences described in this report are AY465357–AY465374 and AY431030–AY431033, as listed in Table 1 and Fig. 2.

Supplementary tables showing the DNA reassociation data are available in IJSEM Online.

Present address: Institute for Animal Health, Compton, Newbury, Berks, UK.

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				H. Christensen, P. Kuhnert, H.-J. Busse, W. C. Frederiksen, and M. Bisgaard Proposed minimal standards for the description of genera, species and subspecies of the Pasteurellaceae Int J Syst Evol Microbiol, January 1, 2007; 57(1): 166 - 178. [Abstract] [Full Text] [PDF]