Bactericidal activity of rat lung lavage fluid against Bordetella pertussis

Cell-free lung lavage fluid (LLF) from healthy normal rats killed phase I ( wild-type, virulent) Bordetella pertussis at 37 degrees C in vitro. B. para pertussis was also killed by the LLF, but phase IV (avirulent mutant) B. pe rtussis and some other common bacterial species, including B. bronchiseptic a, were not. Transmission electron microscopy of thin sections of the phase I B. pertussis showed extensive structural damage and cell lysis. None of the other mammalian species tested had LLF with bactericidal activity again st B. pertussis as high as that of the rat. Rats killed with halothane yiel ded LLF with higher bactericidal activity than when CO2 was used. Ultracent rifugation of LLF at 55 000 g gave a surfactant (pellet) fraction that had c. 95% of the bactericidal activity and which was biochemically distinct fr om the 5% of activity in the supernate fraction. Phospholipids and fatty ac ids appeared to be involved in LLE bactericidal activity, but not complemen t or lysozyme. Arachidonic acid was the most active of the fatty acids test ed. Artificial surfactant, as used in premature infants, had no bactericida l effect on B. pertussis.