Evaluation of a commercial counterimmunoelectrophoresis kit for detection of Staphylococcus aureus teichoic acid antibodies

Detection of teichoic acid antibodies in Staphylococcus aureus infections

A commercially available agar gel diffusion (AGD) assay was used to investigate the teichoic acid antibody (TAA) response in 183 patients with proven Staphylococcus aureus (SA) infections. Two control groups were also investigated. One consisted of 100 hospitalized patients with a variety of medical and surgical conditions other than SA infection and the other consisted of 116 healthy hospital staff members. The sensitivity of the AGD assay varied markedly depending on the site of infection in the patients with proven SA infections. All patients with SA endocarditis developed positive TAA titres (greater than or equal to 1:4), although more than one third of these were initially negative. In patients with chronic osteomyelitis or septic arthritis, 41% had positive TAA titres, whereas no positive titres were detected in patients with acute osteomyelitis or septic arthritis. Lower rates of positive TAA titres were found in patients with deep abscesses (27%), pneumonia (14%) and post-operative infections (9%), but no positive titres occurred in patients with acute uncomplicated bacteremia, cellulitis or meningitis. In 100 hospitalized control patients, no positive titres were detected, and only 1 of 116 (0.9%) healthy hospital staff controls was positive. Suggested guidelines for the use of the AGD assay are discussed.

Preparation of a latex reagent for the detection of anti-Staphylococcus aureus ribitol teichoic acid antibodies

Purified S. aureus ribitol teichoic acid was covalently bound to carboxylated latex particles. The immunological properties of the polysaccharide antigen were preserved. The reagent obtained was used for the quantification of anti-ribitol teichoic acid antibodies by means of a direct and rapid agglutination test carried out on a slide. There was good correlation between the preliminary results of this test and those obtained with counter-immunoelectrophoresis (CIE). The method is faster and more sensitive than CIE.

Rapid screening for Staphylococcus aureus infection by measuring enterotoxin B

We developed a simple, sensitive laser nephelometric assay (LNA) to detect circulating staphylococcal enterotoxin B (SEB). This assay yields the result within 2 h and needs no special treatment. Influence of protein A, a product generated by Staphylococcus aureus, was negligible in this assay. The levels of SEB in plasma were measured in 28 patients with and without S. aureus infection with the LNA. The levels of SEB in plasma increased significantly in patients with S. aureus infection. We also demonstrated that the levels of SEB in plasma were higher in patients with methicillin-resistant S. aureus infection than in patients with nonresistant staphylococcal infection. Our data indicate that LNA is a useful assay in the early diagnosis of methicillin-resistant S. aureus infection.

Staphylococcus aureus antigens reactive with milk immunoglobulin G of naturally infected dairy cows

A 14- to 26-kilodalton fraction of Staphylococcus aureus exoproteins isolated by molecular sieve chromatography and electroelution from polyacrylamide gels was shown to specifically react with antibodies in milk of naturally infected dairy cows. Silver staining of the antigen preparation electrophoresed in polyacrylamide gels showed the strongest reactivity in the 24- to 26-kilodalton region with lesser staining at lower apparent molecular sizes. An enzyme-linked immunosorbent assay was developed to differentiate infected from uninfected cows for diagnostic purposes. Samples from S. aureus-infected cows reacted in the assay, and samples from uninfected cows did not. There was no correlation between numbers of somatic cells in the samples and reactivity to the antigens. Samples from cows infected with coagulase-negative staphylococci did not react with the antigens. It was found, however, that some samples from uninfected cows that were recently postpartum or producing low amounts of milk contained antibodies which bound the antigens. This was believed to be due to transport from blood to the mammary gland of antibodies which were generated by previous intramammary infections or infections at other sites.

Antibody response to teichoic acid and peptidoglycan in Staphylococcus aureus osteomyelitis

An enzyme-linked immunosorbent assay was used to evaluate the immunoglobulin G (IgG) response to Staphylococcus aureus crude teichoic acid (TA) and peptidoglycan (PG) in both rabbits and patients with osteomyelitis. In rabbits with experimental S. aureus osteomyelitis, elevated levels of IgG to TA were present in 13/18 (72%) of the serum samples obtained at 4 and 10 weeks postinfection. In contrast, only 5/18 (28%) of these sera were found to be positive for antibodies to PG. Of a total of 39 patients with confirmed S. aureus osteomyelitis (11 acute, 28 chronic), IgG to TA was elevated in 17 (44%), whereas antibodies to PG were found to be increased in only 1 (3%). Cross-reacting antibodies to S. aureus TA were detected in only 1/18 (6%) of the patients with osteomyelitis caused by organisms other than S. aureus. These studies indicate that IgG to TA is more prevalent than IgG to PG in patients with staphylococcal osteomyelitis. Although these results are encouraging, a larger number of patients is required for an adequate evaluation of the TA enzyme-linked immunosorbent assay for the diagnosis and management of suspected S. aureus osteomyelitis.