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Updated: Jan 16, 2026
Identification of Rare Bacterial Pathogens by 16S rRNA Gene Sequencing and MALDI-TOF MS
Published on: July 11, 2016
Bacteriological and molecular characterization of B. melitensis isolated from aborted sheep and Malta fever patients
Saba Falah Klaif1, Luma Al-Bayati2,3, Hassan Al-Karagoly4,5
1Unite of Zoonotic Disease, College of Veterinary Medicine, University of Al-Qadisiyah, Al-Qadisiyah, Iraq.
Background:
Zoonotic diseases are a major global health concern, particularly those with high prevalence or widespread impact. Brucella melitensis, the causative agent of human brucellosis or undulant fever, is a highly virulent pathogen that is transmitted mainly through contact with infected animals or consumption of unpasteurized dairy products. The significance lies in its public health impact and economic burden in endemic regions.
Aim:
This study aimed to isolate and identify B. melitensis from human patients and sheep using conventional and molecular techniques, with the goal of tracking its presence and genetic variations across both hosts.
Methods:
A total of 50 samples were collected from Al-Qadisiyah Province, Iraq, including 25 blood samples obtained via venipuncture from sheep owners clinically suspected of having Malta fever and 25 placenta samples aseptically collected from recently aborted ewes during field visits to local farms. We cultivated the collected samples on blood agar media and performed biochemical analysis using VITEK® 2 Compact 15 (V2C15). We also examined the samples using PCR and partial sequencing (PS) techniques, which used the 16S rRNA gene as the bacterial DNA target.
Results:
Classical bacteriological methods identified B. melitensis in 15 out of 25 (60%) human blood samples and 13 (52%) sheep placental samples. In V2C15, 13 (86.66%) and 11 (84%) human and sheep placental samples were positive for B. melitensis. PCR identified B. melitensis in 10 (76.9%) and 10 (90%) human and ewe placental samples, respectively. The partial gene sequencing (PGS) of two samples from humans and two samples from ewe placentas demonstrated isolates closely aligned with global isolates from China and India, respectively.
Conclusion:
The present study revealed continuous circulation of B. melitensis infection from sheep to humans in Al-Diwaniyah City, Iraq, and that the sequenced bacteria might have faced genetic evolution after they were descended from China or India isolates.
Insights
Brucella melitensis circulates from sheep to humans in Iraq, with genetic links to global isolates. This zoonotic disease poses a significant public health risk, necessitating ongoing surveillance and control efforts.
Area of Science:
- Microbiology
- Zoonotic Diseases
- Public Health
Background:
- Zoonotic diseases, like brucellosis caused by Brucella melitensis, present significant global health and economic challenges.
- Brucella melitensis is a virulent pathogen transmitted through animal contact or unpasteurized dairy products, impacting public health in endemic areas.
Purpose of the Study:
- To isolate and identify Brucella melitensis in human patients and sheep in Al-Qadisiyah Province, Iraq.
- To track the presence and genetic variations of Brucella melitensis across human and ovine hosts.
Main Methods:
- Collected 50 samples (25 human blood, 25 sheep placenta) from Al-Qadisiyah Province, Iraq.
- Utilized conventional bacteriology, VITEK® 2 Compact 15 (V2C15) for biochemical analysis, and PCR with 16S rRNA gene sequencing.
- Performed partial gene sequencing (PGS) on identified isolates.
Main Results:
- Brucella melitensis was identified in 60% of human blood samples and 52% of sheep placental samples using classical methods.
- Biochemical analysis (V2C15) showed higher positivity rates: 86.66% for human and 84% for sheep samples.
- PCR confirmed Brucella melitensis in 76.9% of human and 90% of sheep samples; partial gene sequencing revealed genetic similarities to isolates from China and India.
Conclusions:
- Demonstrated continuous circulation of Brucella melitensis from sheep to humans in Al-Diwaniyah City, Iraq.
- Suggests potential genetic evolution of local Brucella melitensis strains descended from international isolates (China, India).
- Highlights the importance of integrated diagnostic approaches for accurate zoonotic disease surveillance.
