Pasteurella and Mannheimia PDF (Presentation)

Pasteurella and Mannheimia Dr. Nasr Jalboush  Characteristic Species of the genera Pasteurella and Mannheimia of the family Pasteurellaceae are small gram-negative rods or coccobacilli. They are nonmotile, non-spore-forming, facultatively anaerobic, oxidase positiv...

Pasteurella and Mannheimia Dr. Nasr Jalboush  Characteristic Species of the genera Pasteurella and Mannheimia of the family Pasteurellaceae are small gram-negative rods or coccobacilli. They are nonmotile, non-spore-forming, facultatively anaerobic, oxidase positive, and fermentative. Most are commensals on the mucous membranes of the upper respiratory and digestive tracts of domestic and wild animals.  Pasteurella multocida Three subspecies have been proposed, namely P. multocida subsp. multocida. Contains most of the strains that cause significant disease in domestic animals. P. multocida subsp. septica. Recovered from various sources, including dogs, cats, and human beings. Important in wound infections that result when people are bitten by dogs and cats. P. multocida subsp. gallicida. Recovered from avian species and may occasionally cause fowl cholera. These three subspecies are differentiated in the laboratory by minor differences in biochemical tests.  Pasteurella haemolytica P. haemolytica, biotype A. This important species has been moved to the genus Mannheimia and is now named Mannheimia haemolytica. P. haemolytica , biotype T. Renamed Pasteurella trehalosi.  SPECIES OF LESSER IMPORTANCE Pasteurella granulomatis. This species has been renamed Mannheimia granulomatis. It is associated with a severe, progressive, fibrogranulomatous disease of cattle. Pasteurella pneumotropica. recovered from the nasopharynx of some guinea pigs, rats, hamsters, mice, dogs, and cats. secondary invader in pneumonic disease in mice and rats. Pasteurella dagmatis. commensal of the oro- and nasopharynx of dogs and cats.  SPECIES OF LESSER IMPORTANCE Pasteurella gallinarum. Commensal in upper respiratory tract of chickens; occasionally causes low-grade respiratory infections in chickens. Pasteurella canis. canine mouths and dog-bite infections. Pasteurella stomatis. This species has been recovered from the respiratory tracts of dogs and cats. Pasteurella anatis (Gallibacterium anatis). recovered from the intestinal tracts of ducks. Pasteurella langaaensis. isolated from the respiratory tracts of normal chickens.  SPECIES OF LESSER IMPORTANCE Pasteurella avium and Pasteurella volantium recovered from respiratory tracts of normal chickens. Pasteurella caballi. It is a commensal of the upper respiratory tract of horses. Pasteurella lymphangititis. Causes lymphangitis in cattle. Pasteurella mairi. Recovered from porcine aborted fetuses. Pasteurella aerogenes. A commensal in the intestine of swine; rarely pathogenic. Pasteurella anatipestifer. renamed Riemerella anatipestifer. DISTRIBUTION AND HABITAT Pasteurella and Mannheimia organisms are distributed worldwide. Most occur as commensals on the mucous membrane of the upper respiratory and digestive passages of animals. The carrier rate of the more pathogenic species is usually lower than that of the less pathogenic species.  PASTEURELLA MULTOCIDA Infection may be acquired by direct or indirect contact, inhalation, ingestion, and via fomites and wounds.  Pathogenesis As in other gram-negative infection, endotoxins play a role in pathogenesis. Various environmental stresses are important in predisposition to infection Passage of the infecting agent from animal to animal results in enhancement of virulence. Pasteurella multocida is a frequent secondary invader in pneumonic disease it may also be a primary cause of disease, as in fowl cholera and epizootic hemorrhagic septicemia.  Pathogenesis Among the properties of the P. multocida toxin are the following: – It is mainly cell-associated and appears to be released when bacteria die. – It is a heat-labile polypeptide with molecular weight 125,000— 160,000. – It produces necrosis (dermonecrotic) when inoculated into the skin of the guinea pig. – It is immunogenic and lethal for mice.  Pathogenicity It may be a primary agent, but more frequently, it is a secondary invader when resistance of the animal is reduced by various stresses. Pasteurella multocida is a primary or, more frequently, a secondary invader in pneumonia of cattle, swine, sheep, goats, and other species. As a secondary invader, it is frequently involved in bovine pneumonic pasteurellosis and in enzootic pneumonia of pigs. Toxin-producing strains cause the important economic disease of swine, atrophic rhinitis.  Pathogenicity This is important disease characterized by an inflammation of the nasal mucosa, leading often to atrophy of the turbinate bones and distortion of the nasal septum that sometimes results in shortening or twisting of the upper jaw. Prognathism (jutting of the lower jaw) is a common sign. Other signs of this chronic infection are coughing, sneezing, and weight loss.  Pathogenicity It causes fowl cholera, a widespread, contagious disease of domestic and wild birds. It begins as a septicemia or bacterermia with a high mortality. Many surviving birds have localized infections (chronic fowl cholera) and serve as sources of infection for other birds. Turkeys are more susceptible than chickens, and losses in commercial flocks can be large.  Pathogenicity Two serotypes of P. multocida cause hemorrhagic septicemia, an acute disease principally of cattle and water buffalo in tropical and subtropical regions. The disease is an acute septicemia characterized by a rapid course, swollen and hemorrhagic lymph nodes, and numerous subserous petechial hemorrhages. The morbidity rate varies considerably, but the mortality is high. Pasteurella multocida is one of the causes of the pleuropneumonia form of “snuffles” in rabbits; it is a cause of severe mastitis of cattle and sheep, and it is responsible for a variety of sporadic infections in animals, including encephalitis, meningitis, and abortion.  Laboratory Diagnosis Specimens are selected according to the location of the infectious process. The organisms survive well in transport media and in refrigerated and frozen tissues. Definitive diagnosis is based on isolation and identification of P. multocida. Good primary growth requires media enriched with serum or blood. Colonies appear after Incubation for 24 hours at 37C in air or in an atmosphere of 6%-8% CO2. They are usually of moderate size, round, and grayish. Some strains produce large mucoid colonies. Fresh cultures have a characteristic odor.  Laboratory Diagnosis Smears reveal small, gram negative rods and coccobacilli. Of special significance are nonmotility, indole production, lack of hemolysis, and production of oxidase. In contrast, M. haemolytica is beta-hemolytic and indole-negative and grows on MacConkey agar. Definitive identification is based on biochemical tests. Mice and rabbits are susceptible to most strains. Lethal infections develop within one or several days. The laboratory diagnosis of other Pasteurella spp. is essentially similar to that just described for P. multocida.  Antigenic Nature Types A, B, D, E, and F have been identified on the basis of differences in capsular substances (polysaccharides). – Type A. Causes fowl cholera, pneumonia, and many other infections of various animals. – Type B. Causes epizootic hemorrhagic septicemia in Asia, the Middle East, and southern Europe. – Type D. Recovered relatively Infrequently from various infections in many animals, but frequently from pneumonia and atrophic rhinitis in swine. – Type E. Causes hemorrhagic septicemia in Africa. – Type F. Recovered from turkeys; its role in disease is not yet clear.  Antigenic Nature Capsular types may be subdivided further into somatic types on the basis of serologic differences In lipopolysaccharides (somatic or 0 antigens). A serotype is designated by the capsular type, followed by time number representing the somatic type; for example, serotype B:2 is the cause of hemorrhagic septicemia in many regions  PASTEURELLA TREHALOSI New name Bibersteinia trehalosi Formerly P. haemolytica, biotype T. Two different biotypes of P. haemolytica had been identified, biotype A and biotype T. They differed in several characteristics, including pathogenicity, antigenic nature, and biochemical activity. The name P. trehalosi has been proposed for P. haemolytica, biotype T.  MANNHEIMIA HAEMOLYTICA Formerly Pasteurella haemolytica, biotype A. Pathogenesis and Pathogenicity Pasteurella trehalosi and M. haemolytica elaborate a soluble cytotoxin (leukotoxin) that kills alveolar macrophages and other leukocytes of ruminants, thus breaching the lung’s primary defense mechanism.  Pathogenesis and Pathogenicity Some properties of the cytotoxin are the following: – It is produced by all strains of M. haemolytica and P. trehalosi – it is a thermolabile protein of relatively large molecular weight – it resembles the alpha-hemolysin of E. coli – it is immunogenic. There is considerable evidence that the cytotoxin plays an important role in the pathogenesis of pneumonia in ruminants.  Pathogenesis and Pathogenicity Mannheimia haemolytica has a primary or secondary role in pneumonia of cattle, goats, and sheep and is frequently recovered from the bronchopneumonic lungs of cattle with pneumonic pasteurellosis (shipping fever). Other important diseases in which this organism is involved are mastitis of ewes and septicemia of nursing lambs. Pasteurella trehalosi causes septicemia in feeder lambs. Laboratory animals are refractory to experimental infection.  Laboratory Diagnosis Media containing serum or blood are required for good growth of both species. Colonies are round, grayish, and usually somewhat smaller than those of P. multocida. They are usually surrounded by a zone of beta-hemolysis. This zone varies considerably and may be no larger than the colony, and thus, it is not apparent unless the colony is removed.  Laboratory Diagnosis Bovine blood is more suitable than that of sheep or horses for the demonstration of hemolysis. Smears from colonies disclose small gram-negative rods or coccobacilli. They are beta hemolytic, indole-negative, non- motile, and grow on MacConkey agar. Additional biochemical test are required for definitive identification (Table 19.2).  Antigenic Nature and Immunity Mannheimia haemolytica and P. trehalosi are antigenically heterogeneous and somewhat resemble P. multocida in that they have capsular and somatic varieties. The somatic antigens are so complex that serotypes are designated according to differences in capsular substances. Type 1 is the most common type encountered in bovine pneumonia. There are 16 serotypes of M. haemolytica based on capsular antigens. These antigens are recognized by an indirect hemagglutination procedure (Table 19.1).