Research Paper Outer membrane proteins of Fusobacterium necrophorum subsp. necrophorum and subsp. funduliforme Amit Kumar, Greg Peterson, Tiruvoor G. Nagaraja and Sanjeev Narayanan Department of Diagnostic Medicine/Pathobiology, College of Veterinary Medicine, Kansas State University, Manhattan, Kansas, USA Fusobacterium necrophorum, classified into subsp. necrophorum (Fnn) and subsp. funduliforme (Fnf), is frequently associated with necrotic infections of animals and humans. The outer membrane proteins (OMP) of many Gram negative bacteria play an important role in bacterial adhesion and establishment of infection. The OMP profile of F. necrophorum has not been well characterized. We analyzed OMP of bovine strains of Fnn and Fnf and human strains of F. necrophorum. Electrophoretic separations of extracted OMP of Fnn and Fnf strains of cattle showed a total of 19 and 20 protein bands, respectively. The most prominent protein band was 40 kDa in Fnn and 37.5 kDa in Fnf. The four human clinical strains examined had more heterogeneous banding patterns and had different profiles than those of bovine Fnf strains. A total of 11 protein bands in Fnn and 13 protein bands in Fnf were recognized by sera from cattle with liver abscesses. The intensities of many of the bands in Fnn were higher than that of Fnf. We conclude that the two subspecies of F. necrophorum differ in their OMP profiles and the difference may account for differences in their virulence and involvement in the pathogenesis of necrotic infections. Abbreviations: OMP – Outer membrane proteins; Fnn – Fusobacterium necrophorum subsp. necrophorum; Fnf – Fusobacterium necrophorum subsp. funduliforme Keywords: Fusobacterium necrophorum / Subspecies / Outer membrane proteins / Bovine strains / Human strains / Immunodominant proteins Received: November 30, 2012; accepted: February 3, 2013 DOI 10.1002/jobm.201200748 Introduction Fusobacterium necrophorum, a Gram negative and rod- shaped anaerobe, is associated with a variety of necrotic infections in animals and humans [1, 2]. The organism is a major pathogen of cattle and causes hepatic abscesses, foot rot, and necrotic laryngitis or calf-diphtheria [3]. In humans, F. necrophorum is associated with abscesses of internal organs [1] and also causes a condition called Lemierre’s syndrome, affecting young and healthy individuals, characterized by initial pharyngotonsillitis and peritonsillar abscess followed by septic thrombo- phlebitis of ipsilateral internal jugular vein and dissemi- nated metastatic abscesses [4]. F. necrophorum is classified into subsp. necrophorum and subsp. funduliforme [5], and the two subspecies differ in cell morphology, colony characteristics, growth pattern in broth, extracellular enzymes, hemagglutination, hemolytic and leukotoxic activities, chemical composition of LPS, and virulence in mice [3]. In liver abscesses of cattle, Fnn is found more frequently (71–95% of liver abscesses) and more often in pure culture (up to 75%) compared to Fnf [6]. The higher prevalence of Fnn is because of the increased virulence attributed to its higher leukotoxin production. Interest- ingly, strains associated with human infections that were examined by Tadepalli et al. [7] resembled bovine subsp. funduliforme. The outer membrane proteins (OMP) of many Gram negative bacteria play an important role in bacterial attachment to host cells, a key initial step in the Correspondence: Sanjeev Narayanan, Department of Diagnostic Medi- cine/Pathobiology, Mosier Hall, College of Veterinary Medicine, Kansas State University, Manhattan, Kansas 66506-5606, USA E-mail: sanjeev@vet.k-state.edu Phone: þ1 785 532 4430 Fax: þ1 785 532 4039 Environment  Health  Techniques Outer membrane proteins of Fusobacterium necrophorum 1 ß 2013 WILEY-VCH Verlag GmbH & Co. KGaA,Weinheim www.jbm-journal.com J. Basic Microbiol. 2013, 00,1–6