Lung fungal infection. Light micrograph (LM) of a section of lung from a patient with pulmonary candidiasis. Pulmonary candidiasis is a form of pulmonary fungal infection and refers to an opportunistic infection of the lung with the fungus Candida albicans (black). This organism is part of the normal human microbial flora of the oral cavity. Most patients with pulmonary candidiasis tend to have widespread systemic involvement. People with a weakened immune system from other illnesses like HIV, tuberculosis, or cystic fibrosis are those who are most affected by fungal lung infections. Magnification: x150 when printed at 10 centimetres wide