J. Peter Rissing

Binding of a Staphylococcus aureus bone pathogen to type I collagen

We contrasted the collagen-binding potential of the experimental osteomyelitis pathogen, Staphylococcus aureus strain SMH, to several other strains. These included Cowan 1 (binder), Wood 46 (non-binder) and six capsular variants. These measurements were made using an 125I-collagen binding assay. Formalin-killed S. aureus SMH strongly bound commercial type I iodinated collagen (dissociation constant, Kd = 2 x 10(-9) M). The extent of binding was similar to Cowan 1. Binding was saturable and not inhibited by 100 mM solutions of D-glucose, D-galactose, D-mannose, methyl-alpha-L-fucopyranoside, L-hydroxyproline or L-glycine. D-lactose gave moderate inhibition of binding to collagen, and L-fucose was strongly inhibitory. Trypsinized SMH did not bind collagen. None of four Ruthenium-red-staining staphylococci (encapsulated) avidly bound type I collagen. The encapsulated Smith strain, for example, did not bind to collagen but its capsule-negative variant, Smith compact, showed extensive binding. Three of five non-encapsulated S. aureus were strong collagen binders. These data suggest that the prototype bone pathogen binds to the major protein component of bones extracellular matrix. Collagen-binding is promoted by protein adhesin(s), not capsule. The latter, in fact, appeared to interfere with this interaction. Binding was inhibited by solutions containing the simple monosaccharide, L-fucose.

Multistrain Comparison of Three Antimicrobial Prophylaxis Regimens in Experimental Postoperative Pseudomonas Endophthalmitis

We compared subconjunctivally administered ceftazidime and BMY 28142, two third-generation cephalosporins, to a regimen of gentamicin and cefazolin for their ability to prevent experimental Pseudomonas postoperative endophthalmitis in rabbits. After extracapsular lens extraction, an inoculum of Pseudomonas was injected into the vitreous; one of the three antimicrobial regimens was then administered subconjunctivally. All 25 eyes treated with gentamicin and cefazolin become infected (P = 1). Two of 25 eyes treated with BMY 28142 became infected (P less than .001). None of the 25 eyes treated with ceftazidime became infected (P less than .001).

Quantitation of phospholipase A2 and phospholipase C activity using alkaline phosphatase impregnated liposomes

Abstract Phospholipase A2 and C activity was quantitated using liposomes impregnated with alkaline phosphatase. Release of alkaline phosphatase was dependent on phospholipase related hydrolysis of intact vesicles. Released alkaline phosphatase was quantitated after addition of its chromogenic substrate p-nitrophenyl phosphate. The lower limit of detectability for phospholipase A2 and C activity was 0.5 unit/ml. These limits were 10-fold lower than a titrimetric method. Liposome destruction as measured by alkaline phosphatase release was calcium dependent and inhibited by 1 mM EDTA and 1 mM ZnSO4. The assay was technically simple, generated same day results, and used automated enzyme-linked immunosorbent assay instrumentation.