Meeting Abstract
Within the medical literature, there is a growing awareness of the complex interactions – even among commensal species – that may cause polymicrobial diseases and increase virulence of opportunistic pathogens. Despite evidence that Mycoplasma agassizii causes a respiratory disease in tortoises, other, unknown factors influence the severity and recrudescence of disease. We used a quantitative PCR to compare loads of a commensal, common microbe (Pasteurella testudinis) and the opportunistic pathogen (M. agassizii) in nasal lavage samples obtained from 389 Mojave desert tortoises (Gopherus agassizii). We show that animals with P. testudinis have higher loads of M. agassizii, which is associated with a higher risk of disease. However, the prevalences of the microbes were not associated with each other, and the presence of both microbes did not predict a higher probability of disease. We used a captive, M. agassizii-naïve colony of healthy tortoises to verify that P. testudinis alone does not cause disease and is a prevalent member of both the nasal and cloacal microbiomes. We are exploring techniques to understand this possible indirect, facultative interaction between the two microbes, including the possibility of cross-feeding. Cross-feeding occurs when one microbe makes nutrients available to another species of microbe, influencing its persistence or growth rates inside the host. Such mechanisms can include enzymes such as sialidase, which can cleave glycoprotein components of the mucous and provide additional nutrients for microbial growth.
