Fusobacterium necrophorum hemolysin in bovine hepatic abscess

Shotgun proteomic analysis of plasma from dairy cattle suffering from footrot: characterization of potential disease-associated factors

The plasma proteome of healthy dairy cattle and those with footrot was investigated using a shotgun LC-MS/MS approach. In total, 648 proteins were identified in healthy plasma samples, of which 234 were non-redundant proteins and 123 were high-confidence proteins; 712 proteins were identified from footrot plasma samples, of which 272 were non-redundant proteins and 138 were high-confidence proteins. The high-confidence proteins showed significant differences between healthy and footrot plasma samples in molecular weight, isoelectric points and the Gene Ontology categories. 22 proteins were found that may differentiate between the two sets of plasma proteins, of which 16 potential differential expression (PDE) proteins from footrot plasma involved in immunoglobulins, innate immune recognition molecules, acute phase proteins, regulatory proteins, and cell adhesion and cytoskeletal proteins; 6 PDE proteins from healthy plasma involved in regulatory proteins, cytoskeletal proteins and coagulation factors. Of these PDE proteins, haptoglobin, SERPINA10 protein, afamin precursor, haptoglobin precursor, apolipoprotein D, predicted peptidoglycan recognition protein L (PGRP-L) and keratan sulfate proteoglycan (KS-PG) were suggested to be potential footrot-associated factors. The PDE proteins PGRP-L and KS-PG were highlighted as potential biomarkers of footrot in cattle. The resulting protein lists and potential differentially expressed proteins may provide valuable information to increase understanding of plasma protein profiles in cattle and to assist studies of footrot-associated factors.

Human infection with Fusobacterium necrophorum (Necrobacillosis), with a focus on Lemierre's syndrome

Human infection with Fusobacterium necrophorum usually involves F. necrophorum subsp. funduliforme rather than F. necrophorum subsp. necrophorum, which is a common pathogen in animals. Lemierre's syndrome, or postanginal sepsis, is the most common life-threatening manifestation. Tonsillitis is followed by septic thrombophlebitis of the internal jugular vein and then a septicemia with septic emboli in lungs and other sites. Recent evidence suggests that F. necrophorum can be limited to the throat and cause persistent or recurrent tonsillitis. F. necrophorum is unique among non-spore-forming anaerobes, first for its virulence and association with Lemierre's syndrome as a monomicrobial infection and second because it seems probable that it is an exogenously acquired infection. The source of infection is unclear; suggestions include acquisition from animals or human-to-human transmission. Approximately 10% of published cases are associated with infectious mononucleosis, which may facilitate invasion. Recent work suggests that underlying thrombophilia may predispose to internal jugular vein thrombophlebitis. Lemierre's syndrome was relatively common in the preantibiotic era but seemed to virtually disappear with widespread use of antibiotics for upper respiratory tract infection. In the last 15 years there has been a rise in incidence, possibly related to restriction in antibiotic use for sore throat.

Fusobacterium necrophorum infections in animals: Pathogenesis and pathogenic mechanisms

Fusobacterium necrophorum, a Gram-negative, non-spore-forming anaerobe, is a normal inhabitant of the alimentary tract of animals and humans. Two subspecies of F. necrophorum, subsp. necrophorum (biotype A) and subsp. funduliforme (biotype B), have been recognized, that differ morphologically, biochemically, and biologically. The subsp. necrophorum is more virulent and is isolated more frequently from infections than the subsp. funduliforme. The organism is an opportunistic pathogen that causes numerous necrotic conditions (necrobacillosis), either specific or non-specific infections, in a variety of animals. Of these, bovine liver abscesses and foot rot are of significant concern to the cattle industry. Liver abscesses arise with the organisms that inhabit the rumen gaining entry into the portal circulation, and are often secondary to ruminal acidosis and rumenitis complex in grain-fed cattle. Foot rot is the major cause of lameness in dairy and beef cattle. The pathogenic mechanism of F. necrophorum is complex and not well defined. Several toxins or secreted products, such as leukotoxin, endotoxin, hemolysin, hemagglutinin, proteases, and adhesin, etc., have been implicated as virulence factors. The major virulence factor appears to be leukotoxin, a secreted protein of high molecular weight, active specifically against leukocytes from ruminants. The complete nucleotide sequence of the leukotoxin operon of F. necrophorum has been determined. The operon consists of three genes (lktBAC) of which the second gene (lktA) is the leukotoxin structural gene. The leukotoxin appears to be a novel protein and does not share sequence similarity with any other leukotoxin. F. necrophorum is also a human pathogen and the human strains appear to be different from the strains involved in animal infections.

Differentiation of Fusobacterium necrophorum subspecies from bovine pathological lesions by RAPD-PCR

Nineteen strains from bovine abscesses identified as Fusobacterium necrophorum by the VPI method were examined by other methods. The API 20A test kit characterized all 19 strains as F. necrophorum. Seven of the strains had haemagglutinating activity and were classified as F. necrophorum subspecies necrophorum, and the remaining, 12 nonhaemagglutinating strains, were classified as F. necrophorum subspecies funduliforme. We used RAPD-PCR with a 10-mer oligonucleotide primer, W1L-2, to confirm this differentiation of the two subspecies. These results suggest that random amplified polymorphic DNA polymerase chain reaction (RAPD-PCR) with a suitable primer can be used as a new tool for the differentiation of F. necrophorum subspecies isolated from bovine pathological lesions.

Fusobacterium necrophorum haemolysin stimulates motility of ileal longitudinal smooth muscle of the guinea-pig

Fusobacterium necrophorum haemolysin (0.5-3.1 mg protein/mL) dose-dependently induced contractions of the isolated ileal longitudinal smooth muscle of the guinea-pig. The haemolysin (3.1 mg protein/mL) -induced maximum contraction of 75% of the response to 60 mM K+ declined within 17 min and the muscles then demonstrated rhythmic contractions. Tetrodotoxin (3.1 x 10(-6) M) had no effect on the contraction due to the haemolysin. After incubation in Ca(2+)-free medium, the ileal response to the haemolysin was lost. Verapamil, a Ca2+ channel blocker, dose-dependently inhibited the contraction to the haemolysin. The rabbit anti-serum against F. necrophorum haemolysin inhibited the haemolysin-induced contraction of ileal muscle. The bacterial haemagglutinin and the lipopolysaccharide had no effect on the response of ileal muscle. These findings suggest that the haemolysin-induced direct stimulation of ileal motility dependant on Ca2+ influx will increase the probability of contact of F. necrophorum and ileal mucosa and could increase the chances of colonization for F. necrophorum.

The effects of physical and chemical agents on the secretion and stability of a Fusobacterium necrophorum hemolysin

The effect of various agents as enhancers or inhibitors of hemolysin secretion by Fusobacterium necrophorum was investigated. The hemolysin secreted in phosphate buffered saline (PBS) alone was inactivated shortly after secretion. Tween-80 or albumin preserved the hemolytic activity in PBS in which cultures of F. necrophorum had been suspended. Hemoglobin was found to enhance hemolysin secretion. However, higher concentrations diminished secretion. Chloramphenicol, an inhibitor of protein synthesis, exhibited no effect on the hemolytic activity. However, the addition of sodium azide, an energy metabolic inhibitor, significantly reduced the hemolytic activity. Lower temperatures and pH above 9 and below 6 all yielded a low hemolytic activity. Cells suspended in Tween-80 prior to sonication yielded a substantial amount of extracellular hemolytic activity with low intracellular activity detected. However, cells suspended in PBS alone yielded a low extracellular activity but rather a high intracellular activity. The same spectrum of red blood cells of different species were found to be sensitive to both the extracellular and intracellular hemolysins.

Stability and stabilization of Fusobacterium necrophorum hemolysin

The stability and stabilization of the hemolytic activity of Fusobacterium necrophorum subsp. necrophorum and Fusobacterium necrophorum subsp. funduliforme were monitored over a period of four weeks using culture supernatants. The hemolytic activity was completely lost after one week at room temperature and 37 degrees C. After a two-week storage at 4 degrees C and -80 degrees C only trace activity was detected with -80 degrees C being the better of the two conditions. The addition of cysteine monohydrochloride, bovine serum albumin or Tween 80 as stabilizers, however, led to the detection of a considerable amount of the hemolytic activity in the sample stored at 4 degrees C and - 80 degrees C throughout the period investigated. The hemolytic activity appeared to be more stable in the presence of Tween 80 at -80 degrees C. Cysteine monohydrochloride was found to crystallize at - 80 degrees C and was therefore ineffective as a stabilizer at this temperature. Hemoglobin was also ineffective as a stabilizer.

Fusobacterium necrophorum infections: virulence factors, pathogenic mechanism and control measures

Fusobacterium necrophorum, a Gram-negative, non-spore-forming anaerobe, is a normal inhabitant of the alimentary tract of animals and humans. Two types of F. necrophorum, subspecies necrophorum (biotype A) and funduliforme (biotype B), have been recognized, which differ morphologically, biochemically, and biologically. The organism is an opportunistic pathogen that causes numerous necrotic conditions (necrobacillosis) such as bovine hepatic abscesses, ruminant foot abscesses and human oral infections. The pathogenic mechanism of F. necrophorum is complex and not well defined. Several toxins, such as leukotoxin, endotoxin, haemolysin, haemagglutinin and adhesin, have been implicated as virulence factors. Among these, leukotoxin and endotoxin are believed to be more important than other toxins in overcoming the host's defence mechanisms to establish the infection. F. necrophorum is encountered frequently in mixed infections and, therefore, synergisms between F. necrophorum and other pathogens may play an important role in infection. Several investigators have attempted to induce protective immunity against F. necrophorum using bacterins, toxoids, and other cytoplasmic components. Generally, none of the immunogens has afforded satisfactory protection against Fusobacterium infections. Because of the unavailability of suitable immunoprophylaxis, the control of F. necrophorum infection has depended mainly on the use of antimicrobial compounds.

Studies on the factors affecting the hemolytic activity of Fusobacterium necrophorum

The in vitro activity of the hemolysin of Fusobacterium necrophorum was determined using the hemolysis of horse erythrocytes as an assay. The effects of medium composition and pH on hemolysin production were investigated. Calf serum and casitone stimulated a comparatively higher hemolytic activity in F. necrophorum subsp. necrophorum and F. necrophorum subsp. funduliforme, respectively. However, sugars, such as glucose, galactose and fructose were inhibitors of hemolytic activity. The spectrum of erythrocyte sensitivity to the hemolysin indicated that horse and quail erythrocytes were more sensitive to the hemolysin of both F. necrophorum subsp. necrophorum and subsp. funduliforme, than were cat, dog, rabbit, pigeon and human erythrocytes. Cat erythrocytes were however insensitive to the hemolysin of subsp. funduliforme. Cattle, sheep and chicken erythrocytes were insensitive to the hemolysin of the two subspecies. Medium pH near neutral were more effective in enhancing hemolytic activity, and hemolytic activity was positively correlated with growth. In general, F. necrophorum subsp. necrophorum was more hemolytic than subsp. funduliforme.