Objective: To document laboratory transmission of brucellosis and identify the likely mechanism of transmission of brucellosis
at Her Royal Highness (HRH) Princess Sirindhorn Medical Center, Thailand.
Material and Method: Using small subunit ribosomal RNA (rRNA) sequencing technique to analyze Brucella melitensis
cultured from the first 2 patients of the hospital and an infected laboratory technician, and using brucellosis serologic test to rule out infections in all other involved technicians.
Results: We had encountered the first 2 cases of brucellosis. Both had infected from community exposure with goat. The first
case had pancreatic abscess and spinal bone involvement with a positive blood culture. The second case presented with fever of unknown origin and had a positive blood culture. A few weeks later, 1 of our laboratory technicians presented with fever, myalgia and fatigue. Blood culture grew B. melitensis. He never had any associated community-acquired risk factors for brucellosis. The presumed mechanism of transmission was an inhalation while taking photographs of the bacterial plate of the first patient. B. melitensis identified from our laboratory technician and both patients were analyzed based on 16S-23S
rRNA intergenic transcribed spacer (ITS) region. Results of 16S-23S rRNA ITS sequence testing confirmed a match from all patients and laboratory technician’s isolate. All other 10 potentially exposed laboratory technicians were asymptomatic. A brucellosis serologic test was negative in all non-infected technicians but was only positive in the 1 infected technician.
Conclusion: This is the first report in Thailand of occupational brucellosis transmitted in microbiologic laboratory. The most
likely mechanism is air-borne inhalation of bacterial organisms on culture media in the absence of adequate precautions.
Laboratory technicians should handle Brucella cultivation with caution utilizing appropriate measures to prevent inhalation.

Keyword: Outbreak, Brucella melitensis, Epidemic investigation, Laboratory transmission