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Brucella melitensis is a Gram-negative coccobacillus bacterium from the Brucellaceae family. The bacterium causes ovine brucellosis, along with Brucella ovis. It can infect sheep, cattle, and sometimes humans, and it can be transmitted by the stable fly.[citation needed] It is zoonotic, unlike B. ovis, causing Malta fever or localized brucellosis in humans.

Brucella melitensis
Brucella melitensis.jpg
A photomicrograph of the bacterium Brucella melitensis
Scientific classification
B. melitensis
Binomial name
Brucella melitensis

Brucella neotomae

Brucella melitensis colonies growing on agar

Pathogenesis and diseaseEdit

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.[1] In goats and sheep, B. melitensis can cause abortion, stillbirth, and weak offspring for the first gestation after the animal is infected. Mastitis can happen, but is uncommon.[2] 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.[3] 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.[2]


In animalsEdit

B. melitensis is transmitted by the stable fly.[citation needed] It can also infect other animals through contact with the placenta, fetus, fetal fluids, and vaginal discharge of infected animals.[2]

In humansEdit

B. melitensis can be transmitted to humans through ingestion of contaminated dairy products. A handful of human-to-human infections have been reported,[where?] including one in 1991, when a man was infected after ingesting unpasteurized goat cheese, and later passed the infection to his wife.[4]


In 1887, Micrococcus melitensis was isolated in Malta by David Bruce from the spleen of a soldier who had died from acute brucellosis.[5]

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.[6] The genus of Micrococcus was later renamed Brucella, in honor of David Bruce.[7]

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.[8]


  1. ^ "Reportable and Foreign Animal Diseases" (PDF). USDA. Retrieved 2017-02-04.
  2. ^ a b c "Ovine and Caprine Brucellosis: Brucella melitensis" (PDF). Center for Food Security and Public Health. September 2009. Retrieved 22 March 2018.
  3. ^ "brucellosis (Brucella melitensis)". Retrieved 22 March 2018.
  4. ^ Vigeant, P; Mendelson, J; Miller, MA (May 1995). "Human to human transmission of Brucella melitensis". The Canadian Journal of Infectious Diseases. 6 (3): 153–5. doi:10.1155/1995/909404. PMID 22514390.
  5. ^ Galińska, EM; Zagórski, J (2013). "Brucellosis in humans — etiology, diagnostics, clinical forms". Annals of Agricultural and Environmental Medicine. 20 (2): 233–8. PMID 23772567.
  6. ^ Wyatt, H.V. (2005). "How Themistocles Zammit found Malta Fever (brucellosis) to be transmitted by the milk of goats". Journal of the Royal Society of Medicine. 98 (10): 451–454. doi:10.1258/jrsm.98.10.451. PMC 1240100. PMID 16199812.
  7. ^ Moreno, E.; Moriyon, I. (8 January 2002). "Brucella melitensis: A nasty bug with hidden credentials for virulence". Proceedings of the National Academy of Sciences. 99 (1): 1–3. doi:10.1073/pnas.022622699. hdl:10171/29623. PMC 117501. PMID 11782541.
  8. ^ Wu, Katherine J. "Oldest Cheese Ever Found in Egyptian Tomb". Smithsonian. Retrieved 2018-08-17.

External linksEdit