Haemophilus Q. Why do I sometimes get slight growth in the X quadrant of the Haemophilus ID Quad plate?
A. This “carry over” effect is often seen when testing H. influenzae on the Haemophilus Quad plate. Nutrients from the Chocolate Agar plate can be accidentally carried over with the inoculum to the Quad plate, resulting in slight growth in the X and V quadrants. Always compare the amount of growth in the X and V quadrants to the growth in the Chocolate (fourth) quadrant. Slight growth on the X or V quadrant compared to luxuriant growth on the Chocolate quadrant is interpreted as a negative. As a precaution against the “carry over” effect, always prepare a dilution of your inoculum and flame your loop between the streaking of each quadrant.
