Abstract
Purpose:
To investigate the association between specific oral bacteria and primary open angle glaucoma (POAG) in an exploratory case-control study.
Methods:
Mouthwash specimens were collected from African American POAG patients (n=27) and controls (n=20). Inclusion criteria for the POAG group were open angles, characteristic visual field (VF) defects and typical optic nerve head (ONH) appearance (cup-to-disc ratio (CDR) >0.8) in at least one eye as determined by a glaucoma specialist. Controls had no current or past IOP elevation, no significant ONH asymmetry, and CDR<0.5 in both eyes. Specimens were analyzed using 16S RNA pyrosequencing after amplification of both the V1-2 and V4 hypervariable regions. Sequences of the amplicons obtained were used to estimate the % contribution of each bacterial species in the oral microbiome. Total amounts of bacterial DNA (bacterial load) were determined using RT-PCR. POAG severity of each case was assessed by the VF mean deviation of the worst eye.
Results:
The total amount of oral bacterial load was not correlated with glaucoma severity (p>0.05).<br /> The frequencies of all 86 detected bacterial genera was similar among POAG cases and controls (p>0.05, Chi-square).<br /> Among 8 genera that contributed at least 3% to the total oral bacterial load in both cases and controls, the normalized amounts of Streptococci was significantly higher in cases vs controls (p<0.01, t-test).<br /> Streptococcus mitis group species were present in 100% of cases and controls and accounted for ~26% of bacterial species in cases and ~17.6% in controls. The amounts of Streptococcus mitis group were higher in cases compared to controls (p<0.02, t-test)<br /> Neisseria species were present in 80% of both cases and controls. However, the amounts (p<0.01, t-test) as well as the frequency (p<0.01, Fisher's exact test) of Neisseria meningitidids polysaccharea were higher among cases compared to controls.
Conclusions:
Alterations in the amounts of individual oral bacterial species may be associated with glaucoma pathology. This may occur because such alterations can lead to the establishment of chronic proinflammatory environment in the oral cavity which in turn may influence glaucoma pathology as previously described (Astafurov 2014). However, given the study limitations caused by evaluation of many genera/species, results should be considered preliminary. Additional studies are needed to confirm the association between oral bacteriome dysregulation and glaucoma.