Correlation of antistaphylococcal antibody titers with severity of staphylococcal disease

Respective roles of serological status and blood specific antihuman herpesvirus 8 antibody levels in human herpesvirus 8 intrafamilial transmission in a highly endemic area

Transmission of human herpesvirus 8 (HHV-8), the etiological agent of Kaposi's sarcoma, occurs mainly during childhood in endemic countries and, to a large extent, through intrafamilial contacts. To additionally investigate this familial transmission, and especially the role of plasma anti-HHV-8 antibody titers, we conducted a large survey in a village from Cameroon, Central Africa, including 92 families (608 individuals). Plasma samples were tested for specific IgG directed against HHV-8 lytic antigens by immunofluorescence assay, and titers were determined by 2-fold dilutions. Global HHV-8 seroprevalence was 60%, raising from 32% under 9 years up to a plateau of around 62% between 15 and 40 years. The familial correlation patterns in HHV-8 seropositive/seronegative status showed strong dependence from mother to child and between siblings. In contrast, no familial correlation in anti-HHV-8 antibody levels was observed among infected subjects. In particular, no relationship was observed between the anti-HHV-8 antibody titer of HHV-8 seropositive mothers and the proportion of their HHV-8 seropositive children. Furthermore, a random permutation study of the anti-HHV-8 antibody titers among HHV-8 infected subjects showed that the main risk factor for infection was the HHV-8 serologic status and not the antibody level. In addition, no correlation was found between anti-HHV-8 antibody levels and buffy coat HHV-8 viral loads in a subsample of 95 infected subjects. Overall, these results strongly suggest that, in this highly endemic population from Central Africa, HHV-8 transmission mainly occurs from mother to child and between siblings, and it is independent of plasma antibody levels of HHV-8 infected relatives.

Rapid serodiagnosis of gram-positive bacterial endocarditis

OBJECTIVES

To characterize a serological test for diagnosing endocarditis caused by Gram-positive cocci.

METHODS

We have developed an indirect enzyme-linked immunosorbent assay (ELISA) for the serological detection of Gram-positive infections. The test measures serum IgG directed towards lipid S, a recently identified exocellular glycolipid antigen which is related to lipoteichoic acid. We have previously shown the test to be of value in serodiagnosis of central venous catheter-associated sepsis and infection of orthopaedic prostheses caused by coagulase-negative staphylococci. We now describe the application of this test in endocarditis.

RESULTS

Serum IgG levels to lipid S were significantly elevated in 34 patients with Gram-positive bacterial endocarditis confirmed as 'definite' by the Duke criteria as compared to 50 control patients. The test had a sensitivity of 88% and a specificity of 88%.

CONCLUSIONS

The assay is independent of culture results or endocardial imaging, making it complementary to currently used investigations. It may therefore be possible to refine the current Duke criteria for diagnosing endocarditis. We describe an algorithm which incorporates lipid S serology into a positive diagnostic strategy.

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.

Antibody response to whole cells and teichoic acid of Staphylococcus aureus strain E 1369 in human sera

A whole cell Staphylococcus aureus enzyme-linked immunosorbent assay (ELISA) using the protein A-deficient strain E 1369 as antigen was compared to an ELISA with cell-wall teichoic acid, extracted from the same strain, as antigen for the detection of IgG antibodies against S. aureus in human sera. A total of 178 serum samples from 119 patients with S. aureus endocarditis, complicated and uncomplicated septicaemia, non-S. aureus endocarditis and septicaemia were investigated together with sera from 155 healthy controls. The sensitivity in diagnosing S. aureus endocarditis was better for the whole cell-ELISA (83%) as compared to the teichoic acid-ELISA (61%), and the same was true for complicated septicaemia (41% vs 29%). The whole cell ELISA was also more specific for S. aureus infections with only 3.6% false positive test values compared to 7.1% for the teichoic acid-ELISA. The differences were however, not statistically significant. None of the assays were able to distinguish between complicated and uncomplicated S. aureus septicaemia.

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.

Experimental mandibular Staphylococcus aureus osteomyelitis; antibody response and treatment with dicloxacillin

Staphylococcus aureus mandibular osteomyelitis was produced in 20 rabbits by injection of a sclerosing agent and 1 X 10(9) colony-forming units of Staphylococcus aureus V8 into the medullary cavity of the mandible. After 2 weeks all rabbits developed infections. 10 of the rabbits were then treated with dicloxacillin (22.5 mg/kg body weight) every 12 h for 7 days and 10 were left untreated. The animals were sacrificed after 8 weeks and histopathological examination was performed. An enzyme-linked immunosorbent assay (ELISA) was used to measure IgG response against staphylococcal teichoic acid and alpha-toxin during the observation period. In the treated group, there was a decrease in clinical symptoms after the treatment period, while in the untreated group, progression of the infection was a common finding. At the end of the treatment period, Staphylococcus aureus V8 could not be recovered from aspirates obtained from animals in the treatment group, while in the non-treatment group, Staphylococcus aureus V8 could be recovered from abscesses in 6 rabbits. Both in the treated group and in the untreated group, the rabbits showed increasing IgG titers against teichoic acid and alpha-toxin during the first 2-3 weeks. No significant differences in antibody response patterns were noted between the treated and untreated groups and no clear correlation between the immunological response and the severity of the disease was observed.

Antibody determinations by counterimmunoelectrophoresis in the diagnosis and management of Pseudomonas aeruginosa bone and joint infections

Antibody titers were measured by counterimmunoelectrophoresis in eight patients with Pseudomonas aeruginosa and in eight patients with Staphylococcus aureus bone and joint infections. Titers were obtained at the beginning of therapy in all patients with pseudomonas infections and at various intervals during and after completion of therapy in seven patients. These patients were followed clinically, with 99mTc-MDP bone and 67Ga scans, and with serial erythrocyte sedimentation rates. Six of eight of these patients had detectable pseudomonas antibodies. A fall in antibody titer occurred in all six successfully treated antibody-positive patients. By contrast, none of the control patients with staphylococcal infections had antibodies to pseudomonas heptavalent antigen. The predictive value of a positive test was 100% and of a negative test, 80%. Counterimmunoelectrophoresis is a helpful adjunctive test in supporting the diagnosis and documenting a successful treatment of chronic pseudomonas bone or joint infections.

Antibodies to staphylococcal teichoic acid and alpha toxin in patients with cystic fibrosis

Enzyme-linked immunosorbent assay (ELISA) was used for IgG antibody determination to teichoic acid and alpha-toxin from Staphylococcus aureus in 65 patients with cystic fibrosis (CF). In patients chronically colonized with S. aureus, elevated titres to teichoic acid were found in 13/35 (37%) patients, to alpha-toxin in 12/35 (34%) and to either antigen in 18/35 (51%). Patients with elevated titres to teichoic acid had a significantly lower X-ray score than patients with normal titres. The highest titres against both teichoic acid and alpha-toxin were seen in patients not receiving optimal treatment. These findings suggest that staphylococci contribute to the tissue damage in CF and that the determination of antibodies especially to staphylococcal teichoic acid might be of value in the diagnosis and management of staphylococcal infections in patients with CF.

Enzyme-linked immunosorbent assay for detection of antibodies to Staphylococcus aureus cell walls in experimental osteomyelitis

An enzyme-linked immunosorbent assay was used to evaluate and compare the immunoglobulin G antibody response to Staphylococcus aureus cell walls of rabbits with either chronic staphylococcal osteomyelitis or subcutaneous abscesses. Osteomyelitis of the femur was produced by the intramedullary application of a sclerosing agent (3% sodium tetradecyl sulfate) and S. aureus. Radiographic evidence of osteomyelitis was observed in 10 of the 13 animals that survived the 10-week experimental period, and the diagnosis was confirmed by histopathology in 8 of the 10 instances. Abscess formation was initiated in a separate group of rabbits by the subcutaneous injection of S. aureus cells. All 10 of these rabbits subsequently developed abscesses, which usually resolved spontaneously within 3 to 5 weeks. Elevated levels of immunoglobulin G antibodies to the cell wall antigen were detected in 7 of 10 rabbits with osteomyelitis at 21 days postinfection, and these animals continued to display high antibody levels even at 59 days postinfection. In contrast, elevated levels of anti-cell-wall antibodies were only detected in 1 of 10 rabbits with subcutaneous abscesses. The enzyme-linked immunosorbent assay was found to be a rapid and sensitive serological technique for the detection of cell wall antibodies in this experimental osteomyelitis model and may be useful for the diagnosis of staphylococcal bone infections in humans.

Antibody response against whole Staphylococcus aureus in patients with staphylococcal septicaemia and endocarditis investigated by ELISA

A whole cell Staphylococcus aureus enzyme-linked immunosorbent assay (ELISA) for the detection of IgG antibodies against S. aureus has been developed. To avoid non-specific binding of IgG to protein A, the protein A-poor strains of S. aureus, E 1369 and Wood 46, were used as antigens. One-hundred and eighty serum samples from 120 patients with S. aureus endocarditis, non S. aureus endocarditis, S. aureus septicaemia and non S. aureus septicaemia were tested together with sera from 155 healthy controls. The sensitivity was similar for the E 1369 ELISA and the Wood 46 ELISA and positive test values were detected in 84.2% of patients with S. aureus endocarditis and 41.2% of patients with complicated S. aureus septicaemia. No distinction could be found between complicated and uncomplicated S. aureus septicaemia. The E 1369 ELISA was more specific showing cross reactions with sera from patients infected with other bacteria than S. aureus in 3.6%. Furthermore, the reproducibility was better for the E 1369 ELISA with a coefficient of variation at 0.054. The absence of need for purified antigens makes the whole S. aureus ELISA easy, rapid and cheap. Therefore, we suggest the whole S. aureus ELISA as a good alternative to previously reported assays using purified cell wall antigens.

Detection of antibody to staphylococcal lipoteichoic acid with a microenzyme-linked immunosorbent assay

Sera from individuals with Staphylococcus aureus endocarditis and osteomyelitis and from some individuals with other forms of gram-positive endocarditis yielded higher readings in a microenzyme-linked immunosorbent assay against lipoteichoic acid from S. aureus than did sera from individuals with other types of serious staphylococcal infection or non-staphylococcal osteomyelitis, or from unselected inpatients.

Enzyme-linked immunosorbent assay for antibodies against teichoic acid in patients with staphylococcal infections

A highly purified teichoic acid preparation was used in an enzyme-linked immunosorbent assay to measure the specific immunoglobulin G (IgG) and IgM response in staphylococcal disease. Antibody determination in a normal population, showing a difference of up to 20-fold in the mean IgG titers between the youngest children and adults, was used to establish age-correlated upper normal values. IgM antibodies were found to be of little diagnostic value since their response was often low or absent. Increased IgG titers were found in 24 of 27 (89%) patients with endocarditis, in 11 of 14 (79%) with complicated septicemia, and in 10 of 20 (50%) with uncomplicated septicemia with serum samples drawn between days 7 and 30 of disease. With paired samples, the numbers of patients with increased IgG titers were 17 of 17, 3 of 4, and 6 of 7, respectively, in the same patient groups. Increased IgG titers were less often demonstrated in patients with chronic osteomyelitis (7 of 22). The enzyme-linked immunosorbent assay for teichoic acid antibodies was found to be a sensitive and specific method for diagnosing staphylococcal endocarditis and septicemia. For optimal results, both the substantial age-correlated variation in normal titers and the importance of adequately spaced samples should be considered.

Serum antibody to staphylococcal teichoic acid and alpha-haemolysin in dermatological patients

Teichoic acid antibody (TAA) titres and antibody to alpha-haemolysin of Staphylococcus aureus (ASta) were measured in 274 dermatological patients and 200 normal controls. Positive ASta values (greater than or equal to 2.0 iu/ml) were common in patients with chronic pruritic dermatoses such as atopic dermatitis (44% ASta positive) and infective eczema (28% ASta positive), but patients with primary pyoderma were all ASTa negative. Positive TAA titres (greater than or equal to 1:4) were seen less frequently than positive ASta values, but still significantly more often in atopic dermatitis patients than in controls. Routine skin swabs were taken from all patients, but positive TAA or ASta tests correlated neither with growth of Staphylococcus aureus from skin lesions nor with signs of clinical infection. This study shows that the TAA test cannot be used as an indicator of septic staphylococcal infection in patients with atopic dermatitis.

Assay of teichoic acid antibodies and antistaphylolysin in the diagnosis of Staphylococcal osteomyelitis

Teichoic acid antibodies (TAA), measured by gel diffusion, and antistaphylolysin (ASa) values were determined in 46 osteomyelitis patients and 200 healthy controls. A positive TAA titer (greater than or equal to 4) was seen in 4/16 patients with acute hematogenous osteomyelitis caused by Staphylococcus aureus and in 7/22 patients with chronic staphylococcal osteomyelitis, while ASta was positive (greater than or equal to 2.0 IU/ml) in 9 patients in both groups all except 2 exceeding 4.0 IU/ml. No positive TAA titres or ASta values were seen in 8 patients with chronic nonstaphylococcal osteomyelitis. The rate of positive test results in 200 controls was 7% for TAA and 4% for ASta. Basing diagnosis on a positive value in either of the tests gave 21 positive results in 38 patients with staphylococcal osteomyelitis; 18 by ASta alone and 11 by TAA alone. Both tests were positive at the same time in 3 patients with acute and in 5 patients with chronic staphylococcal osteomyelitis but never in controls.

Detection of Staphylococcus aureus antibodies in patients with S. aureus infections and in normal persons, using solid phase radioimmunoassay

One hundred and thirteen patients with S. aureus infections, eight patients with non-S. aureus septicemia and 167 normal controls were investigated by solid-phase radioimmunoassay for staphylococcal antibodies. All serum samples tested had measurable antibodies, including the normal controls. The test could differentiate the patients group with S. aureus endocarditis from patients with other S. aureus septicemia, as well as from normal controls, as the endocarditis group had significantly higher antibody levels. Patients with non-bacteremic S. aureus infections, such as osteomyelitis and recurrent furunculosis, showed a wide range of antibody levels, 1/3 and 1/4 of the patients, respectively, showing high levels comparable to the endocarditis patients. Among normal controls, high antibody levels were found in 13 per cent.

Precipitating antibodies against Staphylococcus aureus in serum from patients with staphylococcal osteomyelitis, investigated by means of quantitative immunoelectrophoretic methods

By means of crossed immunoelectrophoresis, precipitating antibodies against 55 Staphylococcus aureus antigens were investigated in serum from 11 patients with acute osteomyelitis and 47 patients with chronic osteomyelitis. Patients with acute osteomyelitis had an increase antibody response, expressed as a precipitin score, compared to normal persons, while patients with chronic osteomyelitis had an almost normal response. The precipitin score in patients with acute osteomyelitis was significantly higher than in patients with chronic osteomyelitis (p less than 0.01). However, patients with chronic osteomyelitis increased their precipitin score during an active phase of the infection.

Teichoic acid antibody and circulating immune complexes in the management of Staphylococcus aureus bacteremia

Optimal antibiotic therapy for patients with Staphylococcus aureus bacteremia remains controversial. The results of two serologic tests, teichoic acid antibody and circulating immune complexes, have shown promise in detecting patients who have serious bacteremia (sustained bacteremia with endocarditis or metastatic abscess) and require longer, more intensive treatment. These tests were performed on serial samples from 38 patients with staphylococcal bacteremia prospectively categorized by severity of infection and by risk factors associated with serious disease (sustained bacteremia, valvular heart disease, absence of focus of infection, metastatic abscess). A surprisingly large group of these patients (20, or 53 percent) could not be prospectively defined as having "serious" or "benign" bacteremia. Neither test differentiated patients with serious bacteremia from those with benign bacteremia. Although it is possible that additional significant associations with risk factors might have been obtained with the teichoic acid antibody test had more patients been included, positive tests were found more frequently only in patients in whom metastatic abscesses developed. The teichoic acid antibody test was found to be a sensitive, but not specific, indicator of serious staphylococcal disease and was of value in excluding serious infection only when a negative results was supported by clinical evidence for benign disease. Other than this use, neither assay was helpful in determining optimal therapy of staphylococcal bacteremia.