Helicobacter macacae

• Helicobacter macacae is a Gram-negative, microaerophilic, spiral-shaped bacterium within the Helicobacter genus. 
• It was first isolated from the colonic tissue of rhesus monkeys (Macaca mulatta), both with and without chronic idiopathic colitis. This discovery has expanded the understanding of Helicobacter species diversity and their association with non-human primates, particularly in research settings. 
• H. macacae has been studied for its potential role in gastrointestinal diseases and its relevance to primate health.

Morphology and Characteristics 

• H. macacae exhibits several defining features typical of the Helicobacter genus. 
• The bacterium is spiral-shaped, which facilitates its movement through mucus layers in the gastrointestinal tract. 
• It is Gram-negative, characterized by a thin peptidoglycan layer and an outer membrane. 
• As a microaerophilic organism, H. macacae thrives in environments with reduced oxygen levels, such as the colonic mucosa. 
• Its motility is supported by flagella, which aid in colonization and persistence within the host.

Isolation and Host Association 

• The initial isolation of H. macacae occurred during studies of rhesus monkeys in colonies with and without endemic diarrhea. 
• It was recovered from the colonic tissue of monkeys with chronic idiopathic colitis, a condition characterized by severe inflammation, crypt abscesses, and mucosal erosion. The bacterium was also detected in monkeys without clinical symptoms, suggesting its presence as part of the gut microbiota in some individuals. 
• Its association with rhesus monkeys highlights its potential role in gastrointestinal health and disease in non-human primates.

Taxonomy and Nomenclature 

• The species name “macacae” reflects its origin from rhesus monkeys, as “Macaca” is the taxonomic genus name of its host. 
• Genetic and phenotypic analyses confirmed its classification as a distinct species within the Helicobacter genus. 
• The type strain of H. macacae is designated as CCUG 55313 (LMG 26486; MIT 99-5501), providing a reference for future studies. 
• Its identification contributes to the expanding taxonomy of Helicobacter species and emphasizes the genus’s adaptability to diverse hosts.

Pathogenic Potential and Clinical Relevance 

• H. macacae has been associated with chronic idiopathic colitis in rhesus monkeys, a condition characterized by progressive weight loss, dehydration, and chronic diarrhea. 
• Histopathological studies have revealed severe inflammation, crypt epithelial hyperplasia, goblet cell depletion, and mucosal ulceration in affected animals. 
• While its exact pathogenic mechanisms remain unclear, H. macacae is thought to play a role in the development of these conditions. 
• Its identification in research primates highlights its relevance in studies of gastrointestinal diseases and host-microbe interactions.

Public Health and Research Implications 

• The discovery of H. macacae underscores the importance of studying Helicobacter species in non-human primates. 
• While there is no evidence to suggest zoonotic transmission or human health implications, monitoring Helicobacter species in research animals is essential for understanding their ecological roles and potential risks. 
• Research into H. macacae may provide insights into the broader Helicobacter genus and its role in gastrointestinal health and disease.