Ultrasound-enhanced latex agglutination for the detection of bacterial antigens in urine

An ultrasound-enhanced latex agglutination technique has been applied to the detection of bacteria in urine. The approach combines the use of ultrasound, the dilution of latex to allow agglutination with low levels of antigen, and microscopy. Using commercially available latex coated with antibody to Esch. coli O157 or K1, ultrasound enhanced the detection of Esch. coli strains carrying these antigens by x512 and x2048 respectively, compared with the standard test card procedure. The latex particles in the commercial kits were 0.4-1.0 micron in diameter. As larger particles are more effectively manipulated in a sound field, particles of 2.8 microns diameter were coated with antiserum against a urinary tract isolate of Esch. coli (SP3112). The application of ultrasound with these particles facilitated the detection of 6 x 10(3) cells/mL of Esch. coli SP3112 within 2 min, a > 10,000-fold increase in sensitivity compared with the normal agglutination procedure. The possible exploitation of this technique in the clinical laboratory for the rapid, sensitive detection of bacterial antigens in urine is discussed.