Haemophilus Q. Why do I occasionally get slight growth in the X quadrant of the Haemophilus ID Quad plate?
A. This “carryover” 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 “carryover” effect, always prepare a dilution of your inoculum and flame your loop between streaking each quadrant.
