The Journal of the American Medical Association recently published a paper about the association of invasive Haemophilus influenzae infections in pregnant women and fetal outcomes. The researchers studied British women who had an invasive H. influenzae infection (defined as recovery of said organism from a normally sterile site). The researchers concluded that pregnant women had a greater risk of invasive infection than non-pregnant women, and these infections resulted in poor pregnancy outcomes.
H. influenzae is a fastidious organism that grows on chocolate agar. Normally associated with respiratory infections, if the organism is an encapsulated strain, it can spread to other parts of the body and cause meningitis, septicemia, pericarditis, and even urinary tract infections.
In terms of identification, H. influenzae are small, gram-negative coccobacilli on microscopic examination. The opaque colonies appear grayish on chocolate agar. Because it requires X and V factors to grow, the organism will appear on blood agar only in the presence of an organism that hemolyzes the blood (like Staphylococcus aureus). In addition to the X and V requirements, H. influenzae ferments glucose and is catalase positive.
Want to learn more? The CDC has great information on this organism.
–Kelly Swails, MT(ASCP), is a laboratory professional, recovering microbiologist, and web editor for Lab Medicine.