Postmortem bacteriology of the lung by printculture of frozen tissue. A technique for in situ culture of microorganisms in whole frozen organs.

Lung lobes obtained at necropsy from 100 patients were frozen at -70 degrees C and sectioned as a whole in a sledge microtome as used on complete frozen animals. Prints of freshly cut surfaces were cultured on different solid media in 14 cm Petri dishes. The printcultures showed three patterns of bacterial growth: dense growth in 24%, patchy growth in 43%, and no significant growth in 33%. Forty-two of the 67 positive printcultures showed to or more bacterial species. Besides bacteria known to be pathogens of the lung, streptococci of the viridans group, enterococci, and streptococci of group B were grown, sometimes in pure cultures. The patterns of the printcultures were reproducible in successive sections, and the quantity of the bacterial species could be assessed. Contaminating bacteria on the surface of the lung lobe could be recognised, as these produced colonies restricted to the edges of the print. Because there was no smearing of infecting and contaminating bacteria, printculture offers a method of reference.