BRUCELLOSIS
Hussien Mohammed Jumaah CABM Lecturer in internal medicine Mosul College of Medicine Thursday, 24 march, 2016Brucellosis: Microbiology and epidemiology Is an enzootic infection (i.e. endemic in animals). Although six species of Brucella are known, only four are important to humans: B. melitensis (goats, sheep and camels). B. abortus (Cows, camels, cattle, buffalo). B. suis (pigs). B. canis (dogs). Brucellae are, gram-negative, non-motile, strict anaerobes, nonsporulating coccobacilli. Sensitive to sunlight, ionizing radiation. Killed by boiling and pasteurization. Resistant to freezing and drying, facilitating airborne transmission. Survive up to 2 months in soft cheese.
Sir David Bruce (1855-1931) British Army physician and microbiologist who discovered Micrococcus melitensis 1887, the organism isolated from the spleens of 5 patients with fatal cases in Malta. The disease gets its names from both its course (undulant) and location (Malta fever, Crimean fever).
Brucellosis : Portals of entry Brucellosis may be acquired by ingesting contaminated uncooked meat, milk, cheese, yoghurt and butter. Animal urine, manure particles may act as sources of infection through abraded skin and aerosols to the respiratory tract and conjunctiva. Inhaling as few as 10 to100 organisms can cause disease. B. melitensis and B. suis have been developed as biological weapon (bioterrorism) . Person-to-person transmission is extremely rare, as is transfer of infection by blood or tissue donation. In a few cases, women have passed the disease to their infants during birth or through their breast milk. May also spread through sexual activity . Brucellae, along with leptspira, have the unique property of being able to penetrate through intact skin
Brucellosis Portals of entry 1. Oral entry - most common route a. Ingestion of contaminated animal products b. contact with contaminated fingers 2. Aerosols a. Inhalation of bacteria b. Contamination of the conjunctivae 3. Percutaneous infection through skin abrasions or by accidental inoculation
Brucellosis: Pathophysiology Brucellae are intracellular organisms that can survive for long periods within the reticulo-endothelial system invading both phagocytic and nonphagocytic cells avoiding the immune system. This explains the chronicity and the tendency to relapse even after adequate antimicrobial therapy and why brucellosis is a systemic disease and can involve almost every organ system. Lipopolysaccharide, a major component of the cell membrane, likely play a substantial role in intracellular survival.
Brucellosis: Clinical features The disease may be Asymptomatic. Acute (< 2 months) Subacute (2-12 months) Chronic (> 1 year) incapacitating disease with severe complications. B. melitensis is associated with acute infection and causes the most severe disease, whereas the infections with other species are usually subacute and prolonged.
Brucellosis: Clinical features (continued) The incubation period ,1 week to several months. Acute illness is characterised by a high swinging temperature, chills , rigors , sweating, lethargy, headache, and joint and muscle pains. Occasionally delirium, abdominal pain and constipation. Some authors consider malodorous perspiration pathognomonic. Fewer than 1% of patients die usually a consequence of cardiac involvement; rarely from severe neurologic disease. Localised infection which occurs in about 30% of patients, more likely if diagnosis and treatment are delayed.
Brucellosis: Clinical features (continued) Physical signs A palpable spleen, may lead to hypersplenism and thrombocytopenia. Enlarged lymph nodes.
Localised infection
Brucellosis: DiagnosisDefinitive diagnosis depends on the isolation of the organism. Blood cultures are positive in 75–80% of infections caused by B. melitensis and 50% of those caused by B. abortus.Bone marrow culture should not be used routinely but may increase the diagnostic yield, particularly if antibiotics have been given before specimens are taken. CSF culture in neurobrucellosis is positive in about 30% of cases. The laboratory should be alerted to a suspected diagnosis of brucellosis, as the organism has a propensity for infecting laboratory workers and must be cultured at an enhanced containment level.Brucellosis: Diagnosis (continued) Serology may also aid diagnosis. In endemic areas, a single high antibody titre of more than 1/320 or a fourfold rise in titre is needed to support a diagnosis of acute infection. The test usually takes several weeks to become positive but should eventually detect 95% of acute infections.
Treatment of brucellosis Aminoglycosides show synergistic activity with tetracycline against brucellae. Treatment regimens for different forms of brucellosis are outlined in the box