Transport of Multidrug Resistance Substrates by theStreptococcus agalactiaeHemolysin Transporter

Abstract

Streptococcus agalactiae (group B streptococcus [GBS]) causes neonatal sepsis, pneumonia, and meningitis, as well as infections of the bovine udder. The S. agalactiae hemolysin is regarded as an important virulence factor, and hemolysin expression is dependent on the cyl gene cluster. cylA and cylB encode the ATP binding and transmembrane domains of a typical ATP binding cassette (ABC) transporter. The deduced proteins contain the signature sequence of a multidrug resistance (MDR) transporter, and mutation of the genes results in a nonhemolytic and nonpigmented phenotype. To further elucidate the function of the putative transporter, nonpolar deletion mutants of cylA were constructed. These mutants are nonhemolytic and can be complemented by the transporter genes. Wild-type strain and nonhemolytic cylA and cylK deletion mutants were exposed to known substrates of MDR transporters. Mutation of cylA significantly impaired growth in the presence of daunorubicin, doxorubicin, and rhodamine 6G and resulted in a decreased export of doxorubicin from the cells. The mutation of cylK, a gene of unknown function located downstream from cylA, caused a loss of hemolysis but had no effect on the transport of MDR substrates. Furthermore, the hemolytic activity of the wild-type strain was inhibited by reserpine in a dose-dependent manner. We conclude that CylAB closely resembles an ABC-type MDR transporter and propose that the GBS hemolysin molecule represents a natural substrate of the transporter.

Heterogeneity of Hemolysin Expression during Neonatal Streptococcus agalactiae Sepsis

“…CylA represents the ATP binding component of the S. agalactiae hemolysin transporter. Targeted mutagenesis of the transporter results in the loss of the hemolytic phenotype (6), and it has previously been noted that some naturally occurring nonhemolytic S. agalactiae mutants harbor an additional copy of IS1381 inserted at this location in cylA (12). The presence of an additional IS1381 element in the nonhemolytic strain could also be demonstrated by Southern blot hybridization.…”

Characterization of <i>Streptococcus criceti</i> insertion sequence IS<i>Scr1</i>

“…IS982 was first identified in lactococci (Yu et al, 1995) and IS982 family elements are distributed in Gram-positive bacteria (Mahillon and Chandler, 1998). To our knowledge, besides ISScr1 of S. criceti, IS982 members identified from streptococci are ISSa4 of S. agalactiae (Spellerberg et al, 2000), which is a causative organism of invasive neonatal human diseases (Gottschalk et al, 2006) and ISSmu5 of S. mutans (GenBank accession no. AF104381).…”

Characterization of Multidrug-Resistant Group B Streptococci with Reduced Penicillin Susceptibility Forming Small Non-Beta-Hemolytic Colonies on Sheep Blood Agar Plates

“…The results showed that they harbored a deletion in the deduced amino acid of CylK through positions 127 to 191. A previous study showed that the ⌬cylK mutant of GBS showed less beta-hemolytic activity than the wild type (14,15). Although CylK is a GBS-specific protein with unknown functions, it is thought to be essential for the full expression of beta-hemolytic activity of GBS isolates (14).…”