Helicobacter equorum sp. nov., a urease-negative Helicobacter species isolated from horse faeces.

The researchers have discovered a new species of bacteria that they have named Helicobacter equorum. This bacteria was isolated from healthy horse faecal matter and differs significantly from other bacteria in the Helicobacter genus.

Experiment and Isolation

• During their research, the team isolated two strains of bacteria from the faeces of two different, clinically healthy horses. These were called strains EqF1T and EqF2.
• The bacteria were gram-negative, curved and motile. The identifying feature was a single, monopolar, sheathed flagellum. Unlike many other species in the Helicobacter genus, the new strain was found to be urease-negative.
• Conditions for optimal growth of these bacteria were found to be microaerobic conditions at a temperature of 37 degrees Celsius. They could not survive at 42 degrees Celsius or in media containing 1% glycine.

Further Analysis

• The bacterial strains exhibited positive reactions for oxidase, catalase, and alkaline phosphatase. They could also reduce nitrate to nitrite. However, the strains lacked gamma-glutamyl transpeptidase activity.
• Testing these strains for their antibiotic resistance revealed they were resistant to cephalotin and nalidixic acid but susceptible to metronidazole.

Classification and Naming

• The DNA of these isolates was sequenced, and the 16S and 23S rRNA gene sequences were analysed to confirm that they represented a single new species within the Helicobacter genus.
• When compared to established Helicobacter species, specifically H. pullorum and H. canadensis, the novel strains’ 16S rRNA gene sequence similarity was scored at 98%. The 23S rRNA gene sequence showed a lower similarity of 94%.
• Further genetic, biochemical, and protein data helped in firmly establishing these strains as a new species. The research team decided to name them Helicobacter equorum due to their origin from horse faeces. The type strain was recorded as EqF1T.

Unique Differentiation

• Numerical analysis of whole-cell protein extracts by using Sodium Dodecyl Sulfate Polyacrylamide Gel Electrophoresis (SDS-PAGE) was conducted to compare the novel species with other Helicobacter species.
• This process determined that the new isolates were clearly different from H. pullorum, H. canadensis, H. canis and other species of the genus Helicobacter.
• This finding of the novel species was also independently verified by the sequence analysis of their hsp60 gene.