Group B streptococcal polysaccharide detection in the urine of neonates by staphylococcal co-agglutination.

Staphylococcal co-agglutination reagents were prepared by the sensitization of commercially available staphylococci with commercially available grouping serum. The reagents were able to detect from 31 ng/ml to 62.5 ng/ml of purified group B polysaccharide lacking type specificity, when 20 microliters of polysaccharide solution was used. The reagents were able to identify group B streptococcal polysaccharide in the concentrated urine of all six patients with positive group B streptococcal blood cultures (sensitivity = 100%). Two of 72 patients with negative blood cultures had positive tests when concentrated urine was tested (specificity = 97%). Prepared reagents had a sensitivity and specificity similar to that reported by others for commercially available reagents for the detection of group B polysaccharide at five to ten percent of the total cost.