Diagnostic Laboratory Tests Specimens: Diarrheal/ stools Smears: Gram-stained smears of stool may show the typical"gull-shaped?" rods e Culture: (have been described above)Diagnostic Laboratory Tests Specimens: Diarrheal stools Smears: Gram-stained smears of stool may show the typical “gull-shaped” rods. Culture: (have been described above)