''Brucella melitensis'' is a

Gram-negative Gram-negative bacteria are bacteria that do not retain the crystal violet stain used in the Gram staining method of bacterial differentiation. They are characterized by their cell envelopes, which are composed of a thin peptidoglycan cell wa ...

coccobacillus

bacterium Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were amon ...

from the Brucellaceae family. The bacterium causes ovine

brucellosis Brucellosis is a highly contagious zoonosis caused by ingestion of unpasteurized milk or undercooked meat from infected animals, or close contact with their secretions. It is also known as undulant fever, Malta fever, and Mediterranean fever. The ...

, along with '' Brucella ovis''. It affects primarily

sheep Sheep or domestic sheep (''Ovis aries'') are domesticated, ruminant mammals typically kept as livestock. Although the term ''sheep'' can apply to other species in the genus '' Ovis'', in everyday usage it almost always refers to domesticated ...

and

goat The goat or domestic goat (''Capra hircus'') is a domesticated species of goat-antelope typically kept as livestock. It was domesticated from the wild goat (''C. aegagrus'') of Southwest Asia and Eastern Europe. The goat is a member of the a ...

s, but cases have also been observed in

cattle Cattle (''Bos taurus'') are large, domesticated, cloven-hooved, herbivores. They are a prominent modern member of the subfamily Bovinae and the most widespread species of the genus ''Bos''. Adult females are referred to as cows and adult ma ...

yaks The domestic yak (''Bos grunniens''), also known as the Tartary ox, grunting ox or hairy cattle, is a species of long-haired domesticated cattle found throughout the Himalayan region of the Indian subcontinent, the Tibetan Plateau, Kachin St ...

water buffalo The water buffalo (''Bubalus bubalis''), also called the domestic water buffalo or Asian water buffalo, is a large bovid originating in the Indian subcontinent and Southeast Asia. Today, it is also found in Europe, Australia, North America, So ...

, Bactrian and

dromedary The dromedary (''Camelus dromedarius'' or ;), also known as the dromedary camel, Arabian camel, or one-humped camel, is a large even-toed ungulate, of the genus ''Camelus'', with one hump on its back. It is the tallest of the three species of ...

camels,

alpaca The alpaca (''Lama pacos'') is a species of South American camelid mammal. It is similar to, and often confused with, the llama. However, alpacas are often noticeably smaller than llamas. The two animals are closely related and can success ...

dog The dog (''Canis familiaris'' or ''Canis lupus familiaris'') is a domesticated descendant of the wolf. Also called the domestic dog, it is derived from the extinct Pleistocene wolf, and the modern wolf is the dog's nearest living relative. Do ...

horse The horse (''Equus ferus caballus'') is a domesticated, one-toed, hoofed mammal. It belongs to the taxonomic family Equidae and is one of two extant subspecies of ''Equus ferus''. The horse has evolved over the past 45 to 55 million yea ...

s and

pig The pig (''Sus domesticus''), often called swine, hog, or domestic pig when distinguishing from other members of the genus '' Sus'', is an omnivorous, domesticated, even-toed, hoofed mammal. It is variously considered a subspecies of ''Sus ...

s. Humans can become infected if they have contact with an infected animal or its byproducts. Animals acquire ''B. melitensis'' by venereal transmission and contact with the

placenta The placenta is a temporary embryonic and later fetal organ that begins developing from the blastocyst shortly after implantation. It plays critical roles in facilitating nutrient, gas and waste exchange between the physically separate mate ...

, fetus, fetal fluids, and vaginal discharges from infected animals. The organism is found in blood, urine, milk, and semen. It is

zoonotic A zoonosis (; plural zoonoses) or zoonotic disease is an infectious disease of humans caused by a pathogen (an infectious agent, such as a bacterium, virus, parasite or prion) that has jumped from a non-human (usually a vertebrate) to a human. ...

, unlike ''B. ovis'', causing

Malta fever Brucellosis is a highly contagious zoonosis caused by ingestion of unpasteurized milk or undercooked meat from infected animals, or close contact with their secretions. It is also known as undulant fever, Malta fever, and Mediterranean fever. The ...

or localized

in humans. BrucellaMelitensis

Clinical manifestation

The bacterium causes severe inflammation of the epididymis, with formation of spermatocoeles and fibrinous adhesions. This disease is known as ovine brucellosis, and is a reportable disease in the USA. In goats and sheep, ''B. melitensis'' can cause

abortion Abortion is the termination of a pregnancy by removal or expulsion of an embryo or fetus. An abortion that occurs without intervention is known as a miscarriage or "spontaneous abortion"; these occur in approximately 30% to 40% of pre ...

, stillbirth, and weak offspring for the first gestation after the animal is infected.

Mastitis Mastitis is inflammation of the breast or udder, usually associated with breastfeeding. Symptoms typically include local pain and redness. There is often an associated fever and general soreness. Onset is typically fairly rapid and usually occurs ...

can happen, but is uncommon. The infection can also reduce milk yield by at least 10%. The placenta might also be retained, and the animal can suffer from purulent vaginal discharge. In males, the infection can cause acute orchitis and epididymitis, and in turn infertility. Arthritis can also occur. Brucellosis can be confirmed with the help of ''post mortem'' lesions in the reproductive tract, udders, and supramammary lymph nodes. While these are not pathognomonic for brucellosis, they can help farmers determine if their herds are infected.

Transmission

In animals

''B. melitensis'' is transmitted to animals through contact with the placenta, fetus, fetal fluids, and vaginal discharge of infected animals.

In humans

''B. melitensis'' can be transmitted to humans through ingestion of contaminated dairy products. It can also be transmitted to humans via inhalation of the organism or by direct contact with infected animal secretions. Human to human transmission is exceptionally rare, occurring via blood transfusion, organ and tissue transplantation, sexual contact, and breastfeeding.

History

In 1887, ''Micrococcus melitensis'' was isolated in Malta by David Bruce from the spleen of a soldier who had died from acute brucellosis. The mechanism of transmission was not determined until 1905, when Temi Żammit found that apparently healthy goats could infect humans with ''M. melitensis'' via their milk. The genus of ''Micrococcus'' was later renamed ''Brucella'', in honor of David Bruce. The bacterium was detected in a 3200-year-old cheese which was found in the Tomb of Ptahmose (vizier) in 2010, by researchers at the

University of Catania The University of Catania ( it, Università degli Studi di Catania) is a university located in Catania, Sicily. Founded in 1434, it is the oldest university in Sicily, the 13th oldest in Italy, and the 29th oldest university in the world. With a ...

References

External links

Brucella melitensis
genomes and related information a
PATRIC
a Bioinformatics Resource Center funded b
NIAIDBrucella melitensis 16M genome informationType strain of ''Brucella melitensis'' at Bac''Dive'' - the Bacterial Diversity Metadatabase
{{DEFAULTSORT:Brucella Melitensis Hyphomicrobiales