Kingella kingae Expresses Type IV Pili That Mediate Adherence to Respiratory Epithelial and Synovial Cells

Abstract

Kingella kingae is a gram-negative bacterium that colonizes the respiratory tract and is a common cause of septic arthritis and osteomyelitis. Despite the increasing frequency of K. kingae disease, little is known about the mechanism by which this organism adheres to respiratory epithelium and seeds joints and bones. Previous work showed that K. kingae expresses long surface fibers that vary in surface density. In the current study, we found that these fibers are type IV pili and are necessary for efficient adherence to respiratory epithelial and synovial cells and that the number of pili expressed by the bacterium correlates with the level of adherence to synovial cells but not with the level of adherence to respiratory cells. In addition, we established that the major pilin subunit is encoded by a pilA homolog in a conserved region of the chromosome that also contains a second pilin gene and a type IV pilus accessory gene, both of which are dispensable for pilus assembly and pilusmediated adherence. Upon examination of the K. kingae genome, we identified two genes in physically separate locations on the chromosome that encode homologs of the Neisseria PilC proteins and that have only a low level homology to each other. Examination of mutant strains revealed that both of the K. kingae PilC homologs are essential for a wild-type level of adherence to both respiratory epithelial and synovial cells. Taken together, these results demonstrate that type IV pili and the two PilC homologs play important roles in mediating K. kingae adherence.

30 Years of Study of Kingella Kingae : Post Tenebras , Lux

“…An essential step in both colonization of the respiratory tract and seeding of distal sites is adherence to tissues, including the respiratory epithelium and the synovium [44,45]. K. kingae expresses type IV pili that are essential for mediating adherence to respiratory epithelial and synovial cells, presumably facilitating the colonization of the respiratory tract and the seeding of joints [44].…”

“…K. kingae expresses type IV pili that are essential for mediating adherence to respiratory epithelial and synovial cells, presumably facilitating the colonization of the respiratory tract and the seeding of joints [44]. Previous work described the presence of two K. kingae colony types called spreading/corroding and nonspreading/noncorroding, which correlate with high-and low-density piliation, respectively.…”

Respiratory Colonization by Kingella kingae, Person-to-Person Transmission, and Pathogenesis of Invasive Infection

“…In a series of elegant studies, St. Geme et al have shown that K. kingae expresses type IV pili and that these surfaced-exposed fibers are essential for the attachment of the organism to respiratory and synovial cells [16]. The investigators disclosed a chromosomal gene cluster homologous to that found in other gram-negative organisms consisting of a pilA1 gene that encodes the major pilin subunit, and pilA2 and fimB genes of unknown functions but that are dispensable for adherence and expression of pili [16].…”

“…In a series of elegant studies, St. Geme et al have shown that K. kingae expresses type IV pili and that these surfaced-exposed fibers are essential for the attachment of the organism to respiratory and synovial cells [16]. The investigators disclosed a chromosomal gene cluster homologous to that found in other gram-negative organisms consisting of a pilA1 gene that encodes the major pilin subunit, and pilA2 and fimB genes of unknown functions but that are dispensable for adherence and expression of pili [16]. As it is the case for other surfaceexposed virulence factors, the PilA subunit exhibits significant strain-to-strain variation in sequence and antibody reactivity indicating that this component is subjected to intensive selective pressure by the immune system [17].…”

“…This observation suggests that piliation offers a selective advantage in the colonization process and at the early stages of the infection, but is detrimental to the bacterium for the invasion of deep body tissues. Additional work by the same research group identified two other genes named pilC1 and pilC2 in physically separated chromosomal locations that encode homologs of the Neisseria PilC proteins that are essential for adherence and piliation [16,19]. Kingella kingae PilC1 and PilC2 proteins have a low level of homology to each other, contain calcium-binding sites and are dispensable for pilus asssembly [16,19].…”