|CASE REPORT: BACTERIOLOGY
|Year : 2013 | Volume
| Issue : 2 | Page : 66-68
Acute brucellosis caused by Brucella melitensis: A case report
Shailaja T Sukumaran, Sushitha S Thayyil, Sathiavathy K Ambramoli
Department of Microbiology, Jubilee Mission Medical College and Research Institute, Thrissur, Kerala, India
|Date of Web Publication||7-Jan-2014|
Shailaja T Sukumaran
Department of Microbiology, Jubilee Mission Medical College and Research Institute, Thrissur, Kerala
Source of Support: None, Conflict of Interest: None
Members of the genus Brucella are aerobic, small, Gram-negative coccobacilli, which include seven species, of which four are human pathogens, namely Brucella melitensis, Br. abortus, Br. suis and Br. canis. Brucellosis, a zoonosis continues to be a major public health problem worldwide. We report a case of acute brucellosis caused by Br. melitensis in a 25-year-old male working in Middle-East, who presented with fever of 3 weeks duration. He was empirically treated as a case of enteric fever. Br. melitensis was isolated from his blood culture using automated blood culture system and the serology was positive for Brucella IgM antibody. The patient responded well to injection streptomycin 0.75gm IM and doxycycline 200mg daily for a period of three weeks.
Keywords: Acute brucellosis, automated blood culture, Br. melitensis
|How to cite this article:|
Sukumaran ST, Thayyil SS, Ambramoli SK. Acute brucellosis caused by Brucella melitensis: A case report. J Acad Clin Microbiol 2013;15:66-8
| Introduction|| |
Brucellosis More Details, a zoonosis is found throughout the eastern and western hemispheres. Indigenous human and animal infections occur in the Mediterranean region, the Arabian Gulf, the Indian sub continent and parts of America and Africa.  Human infections can occur following 1) contact with infected animals and their products of conception, 2) by consumption of contaminated meat or dairy products and 3) by inhalation of aerosolised organism as in laboratory workers. Human to human transmission is rare.
The genus Brucella More Details is divided into seven species.  Br. melitensis, which is by far the most important cause of human brucellosis, is the causative agent of Mediterranean or Malta fever More Details and is frequently present in unpasteurised milk or cheese products from goats and sheep in the Mediterranean and Middle-East countries.  In countries where Br. abortus has been eradicated from cattle with effective vaccines, Br. melitensis has replaced the former. 
Chances of chronicity and relapses are common in brucellosis due to its intra-cellular location, which makes the bacterium inaccessible to host defence mechanisms and antibiotics. As the treatment requires prolonged use of specific antibiotics, a proper and prompt diagnosis is essential. Strong clinical suspicion and interaction between clinician and microbiologist is crucial for the correct diagnosis of brucellosis.
| Case Report|| |
A 25-year-old male presented with high grade intermittent fever of 3 weeks duration. There was associated chills and rigor and the fever was mostly nocturnal. Abdominal pain, vomiting and loose stools were also present, which led to a significant weight loss of approximately 10 kg. Other symptoms like skin rashes, arthralgia or myalgia were not present. The patient has been working as an air conditioner mechanic in Dubai for the past 6 months. He got admitted in a hospital in Dubai and was treated as a case of typhoid fever. Since the doctor suggested treatment for a few more weeks, he returned to Kerala and got admitted in our hospital. There was no history of any relevant illnesses in the past.
On examination, patient was emaciated and his body temperature was 101°F. Conjunctival congestion and non-tender hepatosplenomegaly of 3 cm each were present. He was taken as a case of pyrexia of unknown origin (PUO) and following investigations were done: Haemogram revealed haemoglobin of 11.6 g%, total white blood cells (WBCs) count of 5800 cells/mm 3 with polymorphs 49%, lymphocytes 42%, monocytes 8% and ESR 25 mm/first hour. Peripheral smear showed microcytic, hypochromic anaemia with a few reactive lymphocytes. Blood urea, serum creatinine, thyroid function test and blood sugar were within normal limits. Total bilirubin was 0.9 mg%, direct bilirubin was 0.24 mg% (normal: 0.0-0.2), SGOT-196 IU and SGPT was 168 IU.
Echocardiogram was within normal limits. Ultrasonography (USG) abdomen revealed hepatosplenomegaly with hypoechoic liver parenchyma. Increased bronchovascular markings were seen in the chest X-ray.
Widal test was non-reactive, malarial parasite QBC and Mantoux tests were negative. Urine culture showed no bacteriuria. ELISA for HBsAg and hepatitis A done from Dubai was non-reactive. Blood culture was done using BacT ALERT 3D automated blood culture system (bio Merieux, Germany).
On admission, patient was empirically treated for enteric fever with injection Ceftriaxone 1 g IV twice daily. Since all the investigations were inconclusive, ELISA for Brucella antibody (IgM) was also done, which was found to be positive. No clinical response was seen even after adding Gentamicin along with Ceftriaxone. Thereafter he was put on Doxycycline 100 mg twice daily and injection Streptomycin 0.75 g once daily. After 2 days of therapy, temperature started coming down.
Blood culture became positive on the fourth day and Gram smear from the broth showed tiny Gram-negative cocci in short chains and clusters. Sub-culture was performed on blood agar (BA) and Mac Conkey agar (MA) and direct sensitivity was done on BA. After 48 hours, small, grey, translucent and glistening, non-haemolytic colonies appeared on BA [Figure 1] and small glistening pale colonies on MA. The Gram smear of the colonies showed small Gram-negative coccobacilli in clusters [Figure 2]. The isolate was catalase and oxidase positive, acid fast by modified (cold) acid fast method, non-motile, not an H 2 S producer and a non-fermenter of sugars. Urease was positive within 4 hours, nitrate was reduced to nitrite, citrate utilisation and indole tests were negative. The isolate was identified as Br. melitensis by Vitek 2 automated bacterial identification system (bio Merieux, Germany) with 98% probability which correlated well with the conventional methods. With Kirby- Bauer disc diffusion method, the isolate was found to be sensitive to Ampicillin, Co-trimoxazole, Tetracycline, Gentamicin, Piperacillin-Tazobactam and Meropenem.
|Figure 2: Gram stained colony smear from BA showing Gram-negative coccobacilli|
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On review after a period of three weeks' therapy with doxycycline and streptomycin, he was totally symptom free and had a weight gain of four kg.
| Discussion|| |
Brucellae enter through abraded skin, conjunctiva and mucosa of gastrointestinal and respiratory tract. Factors that determine the prevalence of brucellosis in endemic countries are the methods of food preparation, efficiency of heat treatment of dairy products and direct contact with animals. 
In the present case, the patient does not have any direct contact with animals and the source of infection can be attributed to the packed milk from an endemic country, which he used to have without boiling. According to him, the milk was pasteurised (which was supposed to be free from Brucellae) and he was not sure of the source of milk, whether ovine or bovine origin. Currently Br. melitensis is the principal cause of human brucellosis worldwide including India.
The diagnosis of human brucellosis is challenging, because of the non-specific clinical presentation. Gastrointestinal symptoms like abdominal pain, nausea, vomiting and diarrhoea may occur as a part of acute systemic infections in more than 70% of patients,  as in the present case. History of travel to endemic areas is an important clue to the diagnosis. Only fewer than 10% of human brucellosis may be clinically diagnosed  and even in endemic areas there is under reporting of cases due to lack of specific diagnostic tools. Though blood culture is the most specific laboratory method, the rate of isolation is only 70% since bacteraemia is as unpredictable as clinical manifestations ],[ which necessitates repeated sampling. Unlike the conventional blood culture methods, which require 6-8 weeks incubation, newer automated methods yield growth within 4-5 days as in this case. Other methods for diagnosis are bone marrow culture (92%), Brucella-specific antigen detection, antibody detection and molecular methods. Standard agglutination test for Brucella antibodies, which was widely used in olden days, is not that helpful since it has many limitations. ELlSA for antigen and antibody detection are available and antigen ELISA is as good as blood culture  but there is a paucity of published data in this regard.  Serology along with a positive blood culture is of significance.
Conventionally, the speciation of the genus Brucella is done by sensitivity to dyes, production of H 2 S, requirement of CO 2 and agglutination by sera monospecific for A and M epitopes. Br. melitensis does not produce H 2 S and does not require CO 2 . Automated bacterial identification methods can identify Brucellae to species level but should be interpreted with caution, as not all contain the appropriate profiles. 
A triple drug regimen of Doxycycline, Aminoglycosides and Rifampicin is the best treatment option for brucellosis. In the case of a two drug regime, a combination of Doxycycline (6 weeks) and Gentamicin/Streptomycin (3 weeks) is preferred over Doxycycline and Rifampicin.  Although a therapy of 6 weeks is associated with less chances of relapse, in our case physicians opted for a 3-week regime since it was an uncomplicated one.
Brucellae are highly infectious organisms requiring class III level of containment and pose an occupational threat to laboratory workers. There are several cases of laboratory-acquired brucellosis, even in centres using class II biosafety cabinets. 
Prevention of human brucellosis is mainly dependent on control of infection in domestic animals by vaccination. A safe and effective vaccine for human use is yet to be manufactured.
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