Staphylococcus aureus binding to human nasal mucin

Abstract

Colonization of human nasal mucosa with Staphylococcus aureus sets the stage for subsequent systemic infection. This study characterizes S. aureus adhesion to nasal mucosa in vitro and investigates the interaction of S. aureus with human nasal mucin. S. aureus binding to cell-associated and cell-free mucus was greater than to nonmucin-coated epithelial cells. Scanning electron microscopy of S. aureus incubated with human nasal mucosal tissue showed minimal binding to ciliated respiratory epithelium. In a solid-phase assay, S. aureus bound to purified human nasal mucin-coated wells significantly more than to bovine serum albumin-coated microtiter wells. Binding to mucin was saturable in a dose-and time-dependent fashion. Staphylococcal adherence to human nasal mucin was inhibited by bovine submaxillary mucin but not by fibrinogen. Pretreatment of mucin with periodate but not with pronase reduced adherence. Trypsin treatment of the bacteria significantly reduced adherence to mucin. 125 I-labelled nasal mucin bound to two surface proteins (138 and 127 kDa) of lysostaphin-solubilized S. aureus. Binding to human nasal mucin occurs in part via specific adhesinreceptor interactions involving bacterial proteins and the carbohydrate moiety in mucin. These experiments suggest that S. aureus binding to mucin may be critical for colonization of the nasopharyngeal mucosa.Staphylococcus aureus remains one of the most frequently occurring community-as well as hospital-acquired pathogens (42,44). The consequences of these infections, especially when bacteremic, are often devastating (26,44). Nasal colonization with S. aureus is common, occurs in 15 to 44% of the general population, and is usually without ill effects (29, 57). Certain groups, however, have higher rates of carriage, including dialysis patients (21, 58), diabetics (51), parenteral drug users (52), and AIDS patients (55). In these high-risk groups, there are strong epidemiologic data linking nasal carriage with an increased risk of subsequent infection. Phage typing and antibiotic susceptibility profiles suggest that the colonizing and invading strains are identical (21,53,58). Colonized individuals at risk of subsequent infection are often treated with topical antimicrobial agents in an attempt to eliminate carriage. This approach has had only limited success (56). The recent emergence of multiply antibiotic-resistant staphylococci has raised concern that effective antimicrobial regimens may not be available in the near future (25,28,47). As a result, new approaches to both the therapy and prevention of these infections must be developed.In contrast to the substantial body of epidemiologic information that exists regarding the risks of S. aureus carriage, relatively little is known of the basic host surface components or mechanisms that mediate attachment of staphylococci to the nasal mucosa. Investigators have demonstrated binding to desquamated nasal epithelial cells (3, 6), to ferret airway mucus (41), bovine submaxillary mucin (41, 46), as well as immunoglobuli...

Co-colonization byStreptococcus pneumoniaeandStaphylococcus aureusin the throat during acute respiratory illnesses

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