2 Periodontal pathogens and their relationship to Respiratory infections Periodontal pathogens cause infection in the mouth. It can cause periodontitis or gum diseases. Periodontal diseases can cause bacterial pneumonia and worsen respiratory diseases like Chronic obstructive pulmonary disease. Periodontal diseases start with mild bacterial infection, and it gradually gets exacerbated. Unhealthy oral conditions help bacteria reside in plaque and multiply it, causing gums inflammation and ultimately damaging the gum, bone, and teeth. When the disease progresses, the gum recedes, and the teeth look longer than expected. Lack of appropriate treatment can cause loose teeth and even complete loss of teeth. The transmission mode is via Bacteria from the periodontal disease travels down to the lungs via droplets, then multiplies in the lungs causes infectious bacterial pneumonia and worsening COPD (Linden et al., 2016). It usually occurs in people with low immunity, elderly patients who canno