Nasopharyngeal Cultures in Pertussis.

Abstract

The generally accepted method for the bacteriological diagnosis of pertussis is the cough-plate culture, originally described by Chievitz and Meyer, or some modification of their procedure. The percentage of positive cultures obtained by this technic varies considerably in the hands of different workers and under various conditions. We have found the cough-plate method satisfactory for older children, but in infants we have obtained positive cultures in only about 25%, even when the cultures were made during the catarrhal period of the disease. This low incidence seems to be due to the fact that the young infant does not cough as vigorously as does the older child, thereby resulting in an inadequate inoculation of the medium. During the course of a comparative study of various technics for making cultures, we were impressed by the favorable results obtained from culturing the nasopharynx. Recent reports, have described the advantages of the nasopharyngeal culture in the bacteriological diagnosis of pneumonia. This present report describes the results obtained by making simultaneous nasopharyngeal, throat and cough-plate cultures in a series of 25 consecutive cases of pertussis observed in the pediatric clinic during the past 4 months. The procedure follows. The medium was prepared as previously described and poured into ordinary Petri dishes. Medium more than 3 days old was discarded. The cough-plate cultures were made by exposing the medium during a paroxysm at a point about 6 inches in front of the patient's mouth. The nasopharyngeal cultures were taken by passing a sterile swab, consisting of a small bit of cotton tightly wrapped about the end of a thin, flexible copper wire, through the nose until it touched the posterior wall of the pharynx.