A 40-year-old woman presents with fever and cough for several days. She complains of green coloured sputum and was treated with inhaled bronchodilators for what was believed to be asthma. The patient had a long history of productive cough with documented bronchiectasis. The patient's temperature was 103degF. She was ale and in no distress. Examination of the chest revealed diffuse coarse wheezes. There was mild clubbing of the fingers and toes. Gram stain of expectorated sputum was done The possible genera into which the organism fits include?

The chest film shows right lower lobe pneumonia. Gram stain of expectorated sputum reveals many filamentous, branched gram-positive rods. B (Nocardia) is correct answer, as it is a gram-positive filamentous rod with prominent branching. Their fine, threadlike (filamentous) diameter distinguishes them immediately from the much larger fungal genera such as A (Candida). Multiple overlapping pseudohyphae of Candida species may appear to be branches, but their much larger size makes their identity as fungi, and not bacteria. C (Clostridium) is, indeed, a gram-positive rod, but it is not branched, and its width is much greater than that of Nocardia or Actinomyces. D (Pseudomonas) cannot be correct for many reasons, the most impoant of which is that it is a gram-negative rod.