Pathogenic microbial detection and control in laboratory animal facilities is essential to guarantee animal welfare, data validity and reproducibility. Helicobacter spp. are known to affect mice health, what may interfere with experimental outcomes. This study aimed to screen for Helicobacter spp. in mice from animal facilities in Rio de Janeiro, Brazil using a PCR-based method. Primers designed to specifi cally identify Helicobacter spp. were used to amplify feces or intestine DNA extracted of mice from four different animal facilities. The expected 375 base pairs (bp) amplicon was purifi ed, sequenced and a similarity of 95% was observed when compared to deposited sequences of H. hepaticus and H. bilis. In our screening, Helicobacter spp. was detected in ~59% of fecal and ~70% of intestine samples. Our study is the fi rst to screen for Helicobacter spp. in mouse facilities of a Rio de Janeiro University using a low cost, rapid molecular diagnostic test. Although Helicobacter spp. screening is not mandatory according to Brazilian animal welfare regulation it is recommended by institutional animal health monitoring programs guidelines worldwide, including ARRIVE, AAALAC and FELASA.

1Pathogenic microbial detection and control in breeding and experimental 2 laboratory animal facilities is essential to guarantee animal welfare, data validity and 3 reproducibility. Helicobacter spp. is known to severely affect mice health, mainly in 4 immunocompromised strains, what may affect experimental outcomes. This study 5 aimed to screen for Helicobacter spp. in mice from four different animal houses in Rio 6 de Janeiro, Brazil using a PCR for 16S ribosomal RNA. A pair of primers was designed 7 to specifically identify Helicobacter species that commonly infect laboratory mice. 8 Following PCR reaction, the expected 375 base pairs (bp) amplification product was 9 purified, sequenced and showed a 95% similarity when compared to deposited 10 sequences of Helicobacter hepaticus and Helicobacter bilis. Then, the presence of 11 Helicobacter spp. in both feces and intestines samples was analyzed. Helicobacter spp 12 DNA was detected in 59.6% of the fecal and 70.17% of the intestine samples. Although 13 Helicobacter spp screening is recommended by institutional animal health monitoring 14 programs worldwide it is still not mandatory by Brazilian animal welfare regulation. 15 Our study, the first to monitor Helicobacter species in laboratory mice in Brazil, 16 demonstrates the possibility of using a low cost, rapid molecular diagnostic test to 17 screen Helicobacter and highlights the importance of regular microbiological 18 verification of mice used for research in Brazilian animal houses.19 20