Diversity of Campylobacter species in a rhesus macaque breeding colony

Abstract

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LETTER

The recent article by Bacon and colleagues (1) focused on the prevalence of Campylobacter jejuni and Campylobacter coli colonization in a population of rhesus macaques. It is useful to point out that other Campylobacter species as well as related spiral bacterial species such as Helicobacter spp. and Arcobacter spp. may also affect rhesus macaque health. A few studies have reported other Campylobacter species in this population including Campylobacter fetus subsp. venerealis (2) and Campylobacter hyointestinalis (3). Helicobacter pylori is well known to be associated with gastritis in these animals (4). Helicobacter suis was reported in a colony of Macaca mulatta without clear clinical significance (4). Arcobacter spp. have been rarely described in these nonhuman primates. A. butzleri, a known human pathogen, was described as a cause of diarrheal illness in rhesus macaques (5, 6).

Additional approaches to understand the prevalence of these spiral bacteria would be useful for population studies. The authors used a selective culture media, Campy Blood Agar (Blaser formulation) with antibiotics (cephalosporins) incubated in microaerobic conditions at 41℃–43°C which preferentially selects for thermophilic species, Campylobacter jejuni and Campylobacter coli. Different media formulations are better suited for isolating other Campylobacter species, such as a charcoal-based medium and other formulations with better performance characteristics, incubated at 37°C along with a microaerobic environment with increased H_2_ concentration (7). It should be noted that commercial gas packs used to generate microaerobic conditions generally have little to no hydrogen produced (7) so other sources to increase H_2_ would be required. Additionally, some Campylobacter species are susceptible to antibiotics in certain media formulations. Another method, such as a filtration method, may be better suited for isolating antibiotic-susceptible Campylobacter species (7). Arcobacter species are aerotolerant and may be recovered on some Campylobacter selective media and media designed for isolating Arcobacter species (7). Helicobacter pylori and other Helicobacter species are quite fastidious, require increased H_2_, and prolonged incubation for successful isolation on culture media (8).

In addition to culture-based methods, molecular approaches to survey nonhuman primate populations would be revealing of the spectrum of species commonly colonizing these non-human primates. Rhoades et al. (3) used metagenomic analysis to study the microbiomes of infant macaques and detected a number of unculturable bacterial species as well as Campylobacter hyointestinalis, a species that requires increased hydrogen for isolation in culture. Using broad-range 16S rDNA PCR methods on fecal material may reveal common or uncommon Campylobacter species (9) and Helicobacter species (10).

Additional comprehensive surveys using alternative culture methods and molecular approaches would add to our knowledge about the importance of other Campylobacter species and other spiral bacteria in health and disease of these nonhuman primates.