Microbiology: Yersinia Pestis Commonly Known as Pasteurella Pestis

MICROBIOLOGY

MICROBIOLOGY
Yersinia pestis
(commonly known as Pasteurella pestis)

Characteristics of Yersinia pestis
A plump, Gram-negative rod (1.0-2.0 x 0.5 µm)
Grows at 35-37C, faster at room temperature.
Catalase positive
Non-motile (37C and room temperature). Y. pestis is the only species of Yersinia that is non-motile at room temperature.
Oxidase negative
Biochemical characteristics: Included in the database of most enteric identification systems, but an identification of Y. pestis must be considered presumptive until confirmed by a reference laboratory.

Mode of reproduction and life cycle of Y. pestis
Y. pestis reproduce asexually through binary fission.
Yersinia pestis, maintain their existence in a cycle involving rodents and their fleas.

Host range
Humans
Over 200 mammalian species

Host entry
Result of human intrusion into zoonotic (sylvatic) cycle or by entry of rodents or infected fleas into human’s habitat and bite of infected fleas.
Domestic pets can carry plague-infected fleas.
Contact of commensal rodents and their fleas with sylvatic rodents may result in epizootic and epidemic plague.
Handling of infected tissues; airborne droplets from humans or pets with plague pneumonia
careless manipulation of laboratory cultures.
Person-to-person transmission by human fleas.

Physiological effects on the host
Y. pestis may invade directly into the host through the barrier structure of the host skin and encounter phagocytes such as polymorphonuclear leukocytes (PMNs) (predominantly neutrophils) and macrophages at the site of invasion. Most of them might be killed by neutrophils.
The facultative intracellular Y. pestis preferentially infects host macrophages, possibly via recognition of specific surface-associated CCR5 molecules, and survives inside of macrophages at the early stage of infection.
After proliferation and expression of various virulence determinants in macrophages, Y. pestis can be released into the extracellular compartment and spread systemically with acquisition of phagocytosis resistance. During this process, Y. pestis may circumvent destruction by the components of the host innate immune system.

Distribution and prevalence of Y. pestis in the world
Plague is infamous for killing millions of people in Europe during the Middle Ages.
Plague epidemics have occurred in Africa, Asia, and South America but most human cases since the 1990s have occurred in Africa.
Almost all of the cases reported in the last 20 years have occurred among people living in small towns and villages or agricultural areas rather than in larger towns and cities.

History of the disease
Yersinia pestis is the causative agent of the systemic invasive infectious disease often referred to as the plague.
The Y. pestis is an extremely virulent pathogen that is likely to cause severe illness and death upon infection unless antibiotics are administered.
In the past, Y. pestis has caused devastating epidemics during three periods of modern history; the Justinian Plague spread from the Middle East to the Mediterranean during the 6th-8th centuries AD and killed approximately 25% of the population below the Alps region.
Perhaps the most famous incidence of any disease was the devastating Black Plague of 8th-14th century Europe that eradicated 25 million people (nearly 25% of the population) and marked the end of the Dark Ages.
The third endemic began in 1855 in China and was responsible for millions of deaths.

Prevention and control of the disease
Reduce rodent habitat around your home, work place, and recreational areas. Remove brush, rock piles, junk, cluttered firewood, and possible rodent food supplies, such as pet and wild animal food. Make your home and outbuildings rodent-proof.
Wear gloves if you are handling or skinning potentially infected animals to prevent contact between your skin and the plague bacteria. Contact your local health department if you have questions about disposal of dead animals.
Use repellent if you think you could be exposed to rodent fleas during activities such as camping, hiking, or working outdoors. Products containing DEET can be applied to the skin as well as clothing and products containing permethrin can be applied to clothing (always follow instructions on the label).
Keep fleas off of your pets by applying flea control products. Animals that roam freely are more likely to come in contact with plague infected animals or fleas and could bring them into homes. If your pet becomes sick, seek care from a veterinarian as soon as possible.
Do not allow dogs or cats that roam free in endemic areas to sleep on your bed.

Current status of disease
Outbreaks in people still occur in rural communities or in cities.
In the United States, the last urban plague epidemic occurred in Los Angeles in 1924-25. Since then, human plague in the United States has occurred as mostly scattered cases in rural areas (an average of 10 to 15 persons each year).
Globally, the World Health Organization reports 1,000 to 3,000 cases of plague every year.
In North America, plague is found in certain animals and their fleas from the Pacific Coast to the Great Plains, and from southwestern Canada to Mexico.
Most human cases in the United States occur in two regions: 1) northern New Mexico, northern Arizona, and southern Colorado; and 2) California, southern Oregon, and far western Nevada.

References
Deng, W., Burland, V., Plunkett III, G., Boutin, A., Mayhew, G. F., Liss, P., … & Schwartz, D. C. (2002). Genome sequence of Yersinia pestis KIM. Journal of bacteriology, 184(16), 4601-4611.
Lukaszewski, R. A., Kenny, D. J., Taylor, R., Rees, D. C., Hartley, M. G., & Oyston, P. C. (2005). Pathogenesis of Yersinia pestis infection in BALB/c mice: effects on host macrophages and neutrophils. Infection and immunity, 73(11), 7142-7150.
Perry, R. D., & Fetherston, J. D. (1997). Yersinia pestis–etiologic agent of plague. Clinical microbiology reviews, 10(1), 35-66.
http://www.cdc.gov/plague/index.html

/docProps/thumbnail.jpeg