Escherichia coli K1 aslA Contributes to Invasion of Brain Microvascular Endothelial Cells In Vitro and In Vivo

NeonatalEscherichia coli meningitis remains a devastating disease, with unacceptably high morbidity and mortality despite advances in supportive care measures and bactericidal antibiotics. To further our ability to improve the outcome of affected neonates, a better understanding of the pathogenesis of the disease is necessary. To identify potential bacterial genes which contribute toE. coli invasion of the blood-brain barrier, a cerebrospinal fluid isolate ofE. coli K1 was mutagenized with TnphoA . TnphoA mutant 27A-6 was found to have a significantly decreased ability to invade brain microvascular endothelial cells compared to the wild type. In vivo, 32% of the animals infected with mutant 27A-6 developed meningitis, compared to 82% of those infected with the parent strain, despite similar levels of bacteremia. The DNA flanking the TnphoA insertion in 27A-6 was cloned and sequenced and determined to be homologous toE. coli K-12aslA (arylsulfatase-like gene). The deduced amino acid sequence of theE. coli K1aslA gene product shows homology to a well-characterized arylsulfatase family of enzymes found in eukaryotes, as well as prokaryotes. Two additionalaslA mutants were constructed by targeted gene disruption and internal gene deletion. Both of these mutants demonstrated decreased invasion phenotypes, similar to that of TnphoA mutant 27A-6. Complementation of the decreased-invasion phenotypes of these mutants was achieved whenaslA was supplied intrans . This is the first demonstration that this locus contributes to invasion of the blood-brain barrier byE. coli K1.