Escherichia coli K1 aslA contributes to invasion of brain microvascular endothelial cells in vitro and in vivo

Neonatal Escherichia coli meningitis remains a devastating disease, with un acceptably high morbidity and mortality despite advances in supportive care measures and bactericidal antibiotics. To further our ability to improve t he outcome of affected neonates, a better understanding of the pathogenesis of the disease is necessary. To identify potential bacterial genes which c ontribute to E. coli invasion of the blood-brain barrier, a cerebrospinal f luid isolate of E. coli K1 was mutagenized with TnphoA. TnphoA mutant 27A-6 was found to have a significantly decreased ability to invade brain microv ascular endothelial cells compared to the wild type. In vivo, 32% of the an imals infected with mutant 27A-6 developed meningitis, compared to 82% of t hose infected with the parent strain, despite similar levels of bacteremia. The DNA flanking the TnphoA insertion in 27A-6 was cloned and sequenced an d determined to be homologous to E. coli K-12 aslA (arylsulfatase-like gene ). The deduced amino acid sequence of the E. coli K1 aslA gene product show s homology to a well-characterized arylsulfatase family of enzymes found in eukaryotes, as well as prokaryotes. Two additional aslA mutants were const ructed by targeted gene disruption and internal gene deletion. Both of thes e mutants demonstrated decreased invasion phenotypes, similar to that of Tn phoA mutant 27A-6. Complementation of the decreased-invasion phenotypes of these mutants was achieved when aslA was supplied in trans. This is the fir st demonstration that this locus contributes to invasion of the blood-brain barrier by E. coli K1.