Misaki T, Naka S, Wato K, Hatakeyama R, Nagasawa Y, Ito S, Inaba H, Nomura R, Matsumoto-Nakano M, Nakano K: Campylobacter Rectus in the Oral Cavity Correlates with Proteinuria in Immunoglobulin A Nephropathy Patiens. Nephron 2018;139:143–149
It is generally accepted that systemic inflammatory processes can enhance or induce proteinuria, especially in subjects with pre-existing glomerular disorders. However, much less is known about the impact of localized inflammatory disorders, especially those of a bacterial nature, on the permselectivity properties in glomerular diseases.
Misaki and colleagues sought to help fill this knowledge gap by studying the bacterial flora of the mouth (using salivary fluid samples and polymerase chain reaction (PCR) techniques) in 117 patients with IgA nephropathy (lgAN) and 56 healthy controls. Campylobacter rectus and treponema denticola were considered representative of bacteria associated with periodontitis, and streptococcus mutans as bacteria associated with dental caries. Campylobacter rectus, especially when combined with streptococcus mutans, was positively associated with an increased risk of having proteinuria > 0.5gms/d in the patients with IgAN (see table 1). About 44 % of IgAN patients and 27 % of healthy controls had demonstrable campylobacter rectus in saliva. Streptococcus mutans demonstration alone did not show any effect on urinary protein excretion levels. There were no correlations between campylobacter rectus demonstration and renal pathology.
This study is primarily hypothesis generating as correlation is not equivalent to causation. It is unfortunate that no measures of systemic inflammation, such as serum Interleukin 6 or C-reactive protein levels, were included in the study. As the authors note, it is possible that reverse causality is operative (e.g. IgAN predisposes to gingivitis and/or caries). Also, the disease specificity of the observations were not examined. The study needs confirmation and extension into a broader array of proteinuric renal diseases. Nevertheless, it raises the interesting possibility that aggressive treatment of the oral and dental lesion induced by these bacteria might lower the prevalence of proteinuria and thus have salutary effects on the long-term progression of disease.
Table 1: Association between urinary protein levels >0.5 g/gCr and C. rectus and cnm-positive S. mutans (From Nephron 2018;139:143–149)