Staphylococcus aureus latex agglutination (Lat-SA) test for the diagnosis of S. aureus infection

Animal models were established for Staphylococcus aureus generalized infection (septicemia), and for localized S. aureus infection (osteomyelitis and empyema) to evaluate the possible use of a S. aureus latex agglutination (Lat-SA) test as an indicator of S. aureus infection. Plasma, obtained from animals before and after S. aureus challenge, was used for the test. In the models of generalized infection, all nine rabbits and 13 of 20 (65%) rats had a positive Lat-SA test together with a positive blood culture. Only 3 of the 14 (21%) rats with negative blood cultures after S. aureus challenge had a positive test (P less than 0.05). In the models of localized infection, plasma samples were positive in all animals at some time after bacterial challenge, even if the animal was not bacteremic. Aspirates from bone marrow (2/2) for the osteomyelitis model and pleural exudate (2/2) for the empyema model were Lat-SA test positive and yielded S. aureus on culture. Plasma obtained from these animals before injection with bacteria were all negative by the Lat-SA test, as were plasma samples obtained from two rabbits after injection with S. epidermidis. Since these models mimic human disease, the Lat-SA test may be useful as a diagnostic aid for S. aureus infection in man. Further studies will be necessary to evaluate this.