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Re: Human brucellosis - where, when, what and how?

Dear Editor

I fully endorse the recommendations of Reddy and co-workers concerning management of potential Brucella isolates and those staff potentially exposed 1. The authors highlight that clinical information may not always suggest potential brucellosis, especially if time has elapsed since exposure, thus suspicion may not be raised. The authors then proceed to describe four blood culture isolates obtained from patients with travel histories to endemic regions. Although recovery of Brucella from blood cultures taken from patients with undulant fever is the typical text book scenario, readers should be aware that brucellae may result in focal lesions affecting nearly every organ 2. Unusual sources for isolation of brucellae are typified by the recent recovery of a Brucella-like organism from a breast implant 3.

The importance of non-blood samples for diagnosis of brucellosis must also be stressed. Where there is a suitable degree of clinical suspicion, bone marrow is the sample of choice for isolation. This is further substantiated by the recent findings of Mantur and co-workers who undertook a comparative study of Brucella recovery from various specimens. During these investigations, recovery was only achieved from 45.6% of blood cultures whereas 82.5% of bone marrow biopsies yielded growth 4.

Although the United Kingdom is officially Brucella-free, I would like to draw the attention of medical colleagues to recent human infections with marine mammal-associated brucellae. A paper by Sohn et al described two patients with neurological disease attributed to infection with strains of Brucella derived from marine mammals 5. Brucella was isolated following surgical intervention although only one patient was positive serologically. A further infection initially mistaken as B. suis, was reported from New Zealand 6. Previously, laboratory-acquired infection with a similar strain had been described 7. Serological and cultural evidence suggests that brucellosis is very widespread in a range of cetaceans, pinipeds around the coasts of the British Isles and elsewhere, and there is similar evidence that otters located inland are also infected 8.

Finally, regarding the application of PCR to identify Brucella in clinical material as used in case 4, this provides a useful diagnostic tool, negating the need to handle large quantities of this highly infectious microbe. Indeed, this has proven particularly valuable to confirm infection in patients, and household contacts with potential shared exposures 9. Molecular diagnostics have now evolved to offer equivalent discriminatory power to more traditional identification methods, however, cultivation and classical microbiological biotyping remain the gold standard, underscoring the need for precise recommendations for reduction of laboratory exposure, or appropriate management of exposed individuals, as outlined in the afore mentioned article.

Sally J Cutler

References:

1.Reddy S, Manuel R, Sheridan E, et al., Brucellosis in United Kingdom - a risk to laboratory workers? Recommendations for prevention and management of laboratory exposure. Journal of Clinical Pathology, 2008:jcp.2007.053108.

2.Al Dahouk S, Nockler K, Hensel A, et al., Human brucellosis in a nonendemic country: a report from Germany, 2002 and 2003. Eur J Clin Microbiol Infect Dis, 2005;24:450-6.

3.De BK, Stauffer L, Koylass MS, et al., Novel Brucella Strain (BO1) Associated with a Prosthetic Breast Implant Infection. Journal of Clinical Microbiolology 2008;46:43-49.

4.Mantur BG, Mulimani MS, Bidari LH, et al., Bacteremia is as unpredictable as clinical manifestations in human brucellosis. Int J Infect Dis, 2008;12:303-7.

5.Sohn AH, Probert WS, Glaser CA, et al., Human neurobrucellosis with intracerebral granuloma caused by a marine mammal Brucella spp. Emerging Infectious Diseases, 2003;9:485-488.

6.McDonald WL, Jamaludin R, Mackereth G, et al., Characterization of a Brucella sp. Strain as a Marine-Mammal Type despite Isolation from a Patient with Spinal Osteomyelitis in New Zealand. Journal of Clinical Microbiolology, 2006;44:4363-4370.

7.Brew SD, Perrett LL, Stack JA, et al., Human exposure to Brucella recovered from a sea mammal. Veterinary Record, 1999;144:483.

8.Foster G, MacMillan AP, Godfroid J, et al., A review of Brucella sp. infection of sea mammals with particular emphasis on isolates from Scotland. Vet Microbiol, 2002;90:563-80.

9.Mendoza-Nunez M, Mulder M, Franco MP, et al., Brucellosis in Household Members of Brucella Patients Residing in a Large Urban Setting in Peru. Am J Trop Med Hyg, 2008;78:595-598.