Molecular confirmation of
Brucella
spp. in traditional cheeses: A cross‐sectional study
Narges Abasi, Ali Mehrabi, Masoud Kazeminia, Shaghayegh Mousavi, Hajar Khedmati Morasa, Peyman Ghajarbeygi, Seyed Sajjad Babaeimarzangou, Razzagh Mahmoudi Abstract
Background and Objective
Brucella spp. are major zoonotic foodborne pathogens frequently associated with the consumption of unpasteurized dairy products, particularly traditional cheeses. Although previous studies, including molecular investigations, have examined Brucella contamination in Iranian dairy products, molecularly confirmed and methodologically comparative data from central Iran remain limited, particularly with respect to diagnostic specificity. This cross‐sectional study aimed to (i) estimate the proportion of cheese samples yielding culture‐positive isolates that were PCR‐positive using an omp2a ‐based assay in major types of traditional cheeses marketed in Qazvin province, Iran, using combined culture and molecular confirmation, (ii) evaluate the agreement and limitations of conventional culture relative to PCR‐based confirmation, and (iii) explore whether contamination patterns vary descriptively by season and cheese type.
Methods
A total of 112 traditional cheese samples were systematically collected from retail outlets in Qazvin, Iran, using a geographically stratified sampling framework. Samples were initially screened using standard culture techniques. Culture‐positive isolates were subsequently subjected to PCR confirmation targeting the omp2a gene. Associations between contamination status, season, and cheese type were assessed descriptively using the Fisher–Freeman–Halton exact test, as the limited number of PCR‐positive samples precluded reliable logistic regression modeling.
Results
Fourteen samples (12.5%) were culture‐positive, whereas only seven samples (6.25%) were confirmed as Brucella spp. by PCR, indicating possible limited sensitivity of culture‐based screening. White cheese accounted for the highest proportion of PCR‐confirmed samples. Although higher contamination frequencies were observed during autumn and winter, no statistically robust associations with season or cheese type were identified. A statistically significant association was observed between sampling location and PCR‐confirmed positivity ( p = 0.038); however, this finding should be interpreted with caution given the small number of confirmed positives ( n = 7) and unequal sample sizes across sites (Site A: 1/44, Site B: 2/28, Site C: 4/36, Site D: 0/4), and does not establish a causal relationship.
Conclusion
These findings support the cautious integration of molecular tools as confirmatory components of food safety surveillance, alongside strengthened hygiene and pasteurization practices in traditional cheese production.