Isolation and characterisation of intestinal spirochaetes

Area of Science:

• Microbiology
• Gastroenterology
• Epidemiology

Background:

• Intestinal spirochaetes are anaerobic bacteria that colonize the large intestine.
• Their prevalence and clinical significance in humans are not fully understood.
• Previous studies have identified specific species like Brachyspira aalborgi.

Purpose of the Study:

• To investigate the prevalence of intestinal spirochaetes in a general population.
• To characterize the phenotypic properties of human intestinal spirochaete isolates.
• To compare human isolates with known spirochaete species.

Main Methods:

• Faecal or rectal swab samples from 1527 subjects were cultured anaerobically on blood agar with spectinomycin.
• Positive cultures were identified and characterized phenotypically.
• Comparative analysis was performed with porcine intestinal spirochaetes and Brachyspira aalborgi.

Main Results:

• Twenty-three specimens (1.5%) yielded positive results for intestinal spirochaetes.
• Only one positive case was associated with diarrhoea.
• All positive isolates originated from Asian individuals or known homosexuals.
• Human isolates exhibited close phenotypic similarity to non-pathogenic porcine intestinal spirochaetes.
• These isolates were phenotypically distinct from Brachyspira aalborgi.

Conclusions:

• Intestinal spirochaetes are present in a small percentage of the studied population.
• The prevalence appears higher in specific demographic groups (Asians, homosexuals) and is generally not associated with diarrhoea.
• Human isolates represent a distinct group, possibly related to porcine spirochaetes, and differ from Brachyspira aalborgi.