Pasteurella multocida

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A Microbial Biorealm page on the genus Pasteurella multocida

Classification

Higher order taxa

Bacteria; Proteobacteria; Gammaproteobacteria; Pasteurellales; Pasteurellaceae; Pasteurella

Genus

Pasteurella multocida PM70

It is commonly known as avian cholera.

NCBI: Taxonomy

Description and significance

In 1878, Pasteurella multocida was discovered in birds infected with cholera. Then in 1880, Louis Pasteur isolated it. P. multocida is a small, Gram-negative bacterium. It is a non-motile coccobacillus and is penicillin-sensitive (7). It can cause infections in humans, as a result of cat or dog bites and scratches (12). Mammals and birds have it as part of their normal respiratory microbiota and display infections. P. multocida live in the upper respiratory tract of many vertebrate hosts. These include cats, dogs, rabbits, cows, pigs, and fowl. The host species provides these bacteria with nutrients, and if the bacteria are present in an external environment, it is only temporary. This bacterium is located in a wide range of environments. Cholera outbreaks are usually reported in the United States in north central California, the Mid-West, and the Muleshoe National Refuge in Texas.

Genome structure

This bacteria has 2,257,487 nucleotides, 2015 protein coding genes, and 77 RNA genes. It has a circular chromosome and a plasmid. The chromosome is 2,250 kb long (9).

P. multocida, Haemophilus influenza, and E. coli have many similarities in their genome sequences, so evolutionary analyses suggest that P. multocida and H. influenza most likely diverged about 270 million years ago. Microarray analyses show more than fifty Pm70 genes with the role of acquiring iron and metabolism (9).

Cell structure and metabolism

The P. multocida genome shows 129 lipo-proteins that are secreted and located in the outer membrane. Protein H has been found to be the major polypeptide in the outer membrane of the P. multocida (6). This bacteria has a capsule and lipopolysaccharides. The capsule helps to avoid phagocytosis. Lipopolysaccharides are important for survival of the bacteria in the host. The P. multocida toxin has surface adhesins and iron acquisition proteins for attachment and invasion of host cells and to survive in a hostile environment (7).

Iron is important in P. multocida energy metabolism and electron transport. By using whole-genome microarrays, gene expression response to low iron was monitored. It showed that gene expression for energy metabolism and electron transport decreased by 2-6 times, and genes for iron binding and transport increased by 2-7 times during growth for the first two hours (8).

Ecology

P. multocida causes disease in both wild and domesticated animals. If released into the environment by dead birds, it can infect healthy birds, so cholera in birds spreads quickly in wetlands. It can be spread through contaminated drinking water and waste. Inhalation is also another means of transmission of the bacteria. Disease outbreaks have been shown to follow bird migration routes, especially the snow geese. Wildlife biologists believe that these bacteria are transmitted by carrier birds or live in contaminated wetlands throughout the whole year (3).

P. multocida causes avian cholera. Once the outbreak starts, contamination of the wetlands will allow the disease to be transmitted more quickly. P. multocida serotype-1 is the most common serotype associated with bird cholera in central and western North America. Experiments show, however, that wetlands do not become a “long-term reservoir” for P. multocida because during the period after the cholera outbreak, the bacterium does not stay in the wetlands for long (3).

Pathology

P. multocida virulence is caused by a toxin, which is encoded by a bacteriophage. The toxin activates Rho GTPases, which hydrolyze GTP. This is needed for actin stress fiber formation, which aides in endocytosis of P. multocida. The host cell cycle is modulated by this toxin as well. The toxin acts as an intracellular mitogen. It is a facultative anaerobe, so it is oxidase and catalase-positive, and can ferment carbohydrates under anaerobic conditions. P. multocida live in a variety of animals and can be passed onto humans by oral and respiratory infections from animals (12). It can also cross the blood brain barrier and cause meningitis.

P. multocida is a group of bacteria that has a wide range of diseases and hosts. It can cause haemorrhagic septicaemia in cattle and fowl cholera in birds. It is a primary pathogen. Diseases can be spread to humans through dog and cat inflicted bites. Fowl cholera can be seen as being anywhere from acute to chronic. Its pathological manifestations are seen anywhere from acute infections to localized lesions. At this point in research, any species could be a possible host, but birds are the most susceptible. P. multocida is a parasite and is closely associated with its host. It can be isolated from the organs and mucus membranes of infected birds (12).

Application to Biotechnology

Vaccinations can be derived from P. multocida against the diseases that it can cause. P. multocida produces a 140 kDa protein toxin that activates signal transduction pathways, which activate phospholipase C beta, Rho A, Jun kinase, and ERK. Some vaccines are bacterins. These provide limited protection. More effective vaccines are needed for protection against diseases caused by P. multocida. In order to develop more vaccines, new immunogens are being identified using genomics. The results show that the genome of P. multocida has 120 secreted proteins, which are located in the outer membrane. 105 genes that encode these lipoproteins were then cloned and the recombinant proteins were expressed in E. coli. P. multocida-infected chickens produced polyclonal serum that reacted with these proteins. This showed that these immunogens were recognized by the immune system of the chicken, and this included the six new immunogens (1).

A recombinant subunit vaccine for P. multocida has also been developed by cloning and analyzing the gene for protein H on the outer membrane. Protein H had many similarities compared to other serotypes in its primary and secondary structure. Full length, as well as three fragments of protein H were expressed in E. coli. Recombinant proteins of protein H were then purified. These recombinant proteins were antigenic and “detectable with antisera produced by either immunization of commercial vaccine for respiratory disease or formalin-killed cell” (8). The antibodies that were raised against full length protein H protected against P. multocida very well, but the antibodies raised against the three fragments had less protection. This showed that recombinant protein H could prove to be a good vaccine for P. multocida.

Current Research

P. multocida mutants are being researched for their ability to cause diseases. In vitro experiments show that the bacteria responds to low iron. Vaccination against progressive atrophic rhinitis was developed by using a recombinant derivative of P. multocida toxin. The vaccination was tested on pregnant giltsn (sows without previous litters). The piglets that were born were inoculated. The piglets who had non-vaccinated mothers developed atrophic rhinitis, and only a few piglets with vaccinated mothers developed the disease (10).

Some other research is being done on the effects of protein, pH, temperature, NaCl, and sucrose on Pasteurella multocida development and survival. The research seems to show that the bacteria survive better in waters that are 18 degrees Celsius in comparison to 2 degrees Celsius. Adding NaCl by 0.5% also aided in P. multocida survival. The sucrose and pH had minor effects on the bacteria survival (5).

Ongoing research has been done on the response of P. multocida to the host environment. This has been tested using DNA microarrays and proteomics techniques. P. multocida-directed mutants have been tested for their capability to produce disease. It is seen that the bacteria are in host niches that force them to change their gene expression for central energy metabolism and for uptake of iron, amino acids, and other nutrients. In vitro experiments show the responses of the bacteria to low iron and to different kinds of iron sources, such as transferring and hemoglobin. P. multocida genes that are upregulated in times of infection are usually involved in nutrient uptake and metabolism. This shows that true virulence genes may only be expressed and upregulated during the first stages of infection (4).

References

1. Al-Hasani, K., Boyce, J., McCarl, VP., Bottomley, S., Wilkie, I., Adler, B. “Identification of novel immunogens in Pasteurella multocida.” Microbial Cell Factories, vol. 6, no. 3.

2. Basagoudanavar, S.H., Singh, D.K., Varshney, B.C. 2006. “Immunization with outer membrane proteins of Pasteurella multocida (6:B) provides protection in mice.” Journal of Veterinary Medicine, Vol. 53, no. 10. (524-530)

3. Blanchong, JA. “Persistence of Pasteurella multocida in wetlands following avian cholera outbreaks.” Journal of Wildlife Diseases, vol. 42, no. 1 (33-39)

4. Boyce, JD. “How does Pasteurella multocida respond to the host environment?” Current Opinion in Microbiology, vol. 9, no. 1 (117-122)

5. Bredy, JP. “The effects of six environmental variables on Pasteurella multocida populations in water.” Journal of Wildlife Diseases, vol. 25, no. 2 (232-239)

6. Chevalier, G., Duclohier, H., Thomas, D., Schechter, E., Wroblewski, H. “Purification and characterization of protein H, the major porin of Pasteurella multocida.” Journal of Bacteriology, vol. 175, no. 1 (266-276)

7. Harper, M., Boyce, J.D., Adler, B. “Pasteurella multocida pathogenesis: 125 years after Pasteur.” FEMS Microbiology Letters, vol. 265, no. 1. (1-10)

8. Lee, J. “Outer membrane protein H for protective immunity against Pasteurella multocida.” Journal of Microbiology, vol. 45, no. 2 (179-184)

9. May, BJ. “Complete genomic sequence of Pasteurella multocida, Pm70.” Proceedings of the National Academy of Sciences of the United States of America, vol. 98, no. 6 (3460-3465)

10. Nielsen, JP. “Vaccination against progressive atrophic rhinitis with a recombinant Pasteurella multocida toxin derivative.” Canadian Journal of Veterinary Research, vol. 55, no. 2 (128-138)

11. Paustian, ML. “Pasteurella multocida gene expression in response to iron limitation.” Infection and Immunity, vol. 68, no. 6 (4109-4115)

12. Petersen, KD. “Genetic diversity of Pasteurella multocida fowl cholera isolates as demonstrated by ribotyping and 16SrRNA and partial atpD sequence comparisons.” Microbiology, vol. 147 (2739-2748)

13. Yokose, N., Dan, K. “Pasteurella multocida sepsis, due to a scratch from a pet cat, in a post-chemotherapy neutropenic patient with non-Hodgkin lymphoma.” International Journal of Hematology, vol. 85, no. 2. (146-148)

Edited by Christina Fong student of Rachel Larsen and Kit Pogliano at UCSD.

KMG