Evaluation of different API systems for identification of porcine Pasteurella multocida isolates Y.A. Vera Lizarazo, E.F. Rodrı ´guez Ferri, C.B. Gutie ´rrez Martı ´n * Department of Animal Health, Section of Microbiology and Immunology, Faculty of Veterinary Medicine, University of Leo ´ n, 24007 Leo ´ n, Spain Accepted 5 February 2008 Abstract An exhaustive biochemical characterisation of 60 porcine Pasteurella multocida clinical isolates recovered from lesions indicative of pneumonia, previously confirmed by PCR and all belonging to the capsular serogroup A, was performed by means of four commercial systems. The API 20NE correctly identified almost all isolates (95%), but only 60% could be ascribed to this species by the API 20E method. The high diversity exhibited by the API 50CHB/E system, with six different patterns, does not advise its use as additional system for a definitive identification at the species level, but this method could be a potential tool for characterising P. multocida isolates below this level. The more uniform reactions yielded by the API ZYM test make this system helpful in the confirmatory identification of this organism. The high variability (20 profiles) obtained when the four systems are taken together also suggests their usefulness for epide- miological purposes in order to sub-type P. multocida isolates. Ó 2008 Elsevier Ltd. All rights reserved. Keywords: Pasteurella multocida; Swine; Biochemical characterisation; Identification Although Pasteurella multocida is part of the commensal flora of the upper respiratory tract of swine, it may induce pneumonia in growing and finishing pigs to the extent that pneumonic pasteurellosis is one of the most common dis- eases of intensively housed pigs. The disease is often asso- ciated with other important bacterial respiratory infections (enzootic pneumonia caused by Mycoplasma hyopneumo- niae and pleuropneumonia caused by Actinobacillus pleuro- pneumoniae), and results in a disease condition described as chronic respiratory disease. In this disorder, P. multocida usually acts as a secondary pathogen, invading lungs injured by other organisms (Pijoan, 1992). In contrast, sys- temic pasteurellosis is not a frequently diagnosed disease in pigs, although outbreaks of acute septicaemia have been reported (Blackall et al., 2000). In addition, P. multocida may induce progressive atrophic rhinitis in association with Bordetella bronchiseptica (De Jong, 1992). In this study, we report an exhaustive biochemical char- acterisation of P. multocida clinical isolates recovered from porcine lungs, and evaluate the accuracy of API 20E in their identification, as well as the capacity of API 50CHB/E and API ZYM as additional systems for a con- firmatory identification. The API 20NE, used as routine system in clinical laboratories, was also included. A total of 60 P. multocida isolates were recovered from swine with lesions indicative of pneumonia coming from 23 farms in northeastern, northwestern and central Spain between 2003 and 2004. The bacteria were first isolated on Columbia agar with 5% sheep blood (bioMe ´rieux, Lyon, France), and the mucous non-haemolitic colonies were further plated on a selective medium for P. multocida (Avril et al., 1990): Mu ¨ eller-Hinton agar (Pronadisa, Spain) with 5% defibrinated horse blood (bioMe ´rieux), amikacin (2 mg/l) (Sigma Chemical Co., St. Louis, Mo), vancomycin (4 mg/l) (Sigma), and amphotericin B (4 mg/ l) (Sigma). The isolates were genetically confirmed by use of a multiplex PCR assay (Townsend et al., 2001), and all of them were found to belong to capsular serogroup A. 0034-5288/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved. doi:10.1016/j.rvsc.2008.02.002 * Corresponding author. Tel.: +34 987 291 203; fax: +34 987 291 304. E-mail address: cbgutm@unileon.es (C.B. Gutie ´rrez Martı ´n). www.elsevier.com/locate/rvsc Available online at www.sciencedirect.com Research in Veterinary Science xxx (2008) xxx–xxx ARTICLE IN PRESS Please cite this article in press as: Vera Lizarazo, Y.A. et al., Evaluation of different API systems for identification of porcine ..., Res. Vet. Sci. (2008), doi:10.1016/j.rvsc.2008.02.002