Brazilian purpuric fever caused by Haemophilus influenzae biogroup aegyptius strains lacking the 3031 plasmid.

Brazilian purpuric fever (BPF) is a life-threatening pediatric infection caused by Haemophilus influenzae biogroup aegyptius (Hae), an organism formerly associated with only self-limited purulent conjunctivitis. Strains of Hae causing BPF have a 24-MDa plasmid with a specific AccI restriction pattern designated 3031. This plasmid was thought to code for a virulence factor because it had been detected only among Hae strains isolated from BPF cases or their contacts. From 3 typical BPF cases recently identified in São Paulo State, sterile-site Hae isolates were obtained; these isolates were similar to earlier BPF-associated Hae except they did not possess a 3031 plasmid. HindIII restricted chromosomal DNA from these strains was probed with purified 3031 plasmid DNA under high-stringency conditions. There was no evidence that 3031 plasmid DNA had become chromosomally integrated. It appears that the 3031 plasmid does not code for BPF-specific virulence factors.