Use of the enzyme-linked immunosorbent assay for the early diagnosis of Mycoplasma pneumoniae infection

Tuberculous pleurisy mimicking Mycoplasma pneumoniae infection in a previously healthy young adult: A case report

RATONALE

Sometimes, pleural effusion accompanying an acute Mycoplasma pneumoniae infection or tuberculous pleurisy has similar analysis results. We report a case of tuberculous pleurisy which was initially diagnosed as acute M pneumoniae infection, which is of special interest because anti-Mycoplasma antibody results were positive, which served as a red herring.

PATIENT CONCERNS

A 20-year-old woman visited the outpatient emergency romm of our hospital for chief complaints of high fever, dry cough, and pleuralgia persiting for 2 days. Since anti-mycoplasma antibody test results were positive, we treated acute M pneumoniae infection and drained her pleural effusion. The condition tended to improve, but on day 16 postadmission, the acid-fast bacterial culture of the pleural effusion was positive for Mycobacterium tuberculosis.

DIAGNOSES

Tuberculous pleurisy.

INTERVENTIONS

After the diagnosis, the patient received antituberculous drugs.

OUTCOMES

She completed treatment with no noticeable adverse events, and the right pleural effusion disappered and diffuse right pleural thickening improved.

LESSONS

Exudative pleural effusion with lymphocyte dominance and a high adenosine deaminase level in M pneumoniae infection have been reported. Even though the condition suggests acute M pneumoniae infection, clinicians should be aware that tuberculous pleurisy and M pneumoniae infection can share similar clinical features, and should understand the usefulness and limitations of the anit-Mycoplasma antibody test.

[Evaluation of four commercial immunoglobulin G (IgG)- and IgM- specific enzyme immunoassays for diagnosis of Mycoplasma pneumoniae infections]

The four following commercially available enzyme immunoassays (EIAs) were assessed and compared for their performance in detecting Mycoplasma pneumoniae specific IgG and IgM antibodies: EIA-Platelia, EIA-Bmd, EIA-Sorin and EIA-Biotest. Three groups of patients were investigated: 39 patients (27 children and 12 adults) with respiratory infections and a M. pneumoniae PCR-positive in respiratory specimens (group I; 52 sera), 61 healthy children and adults (group II; 61 sera) and 20 patients with rheumatoid factor, antinuclear antibodies or positive antiviral IgM (group III; 20 sera). In group III, the IgM specificity for the EIA-Platelia, EIA-Bmd, EIA-Biotest and EIA-Sorin was 100%, 90%, 65% and 25%, respectively. In the children from group I, the four EIAs had similar IgM sensitivity (89 to 92%) but a striking difference in IgM sensitivity was observed in adult patients: 16% EIA-Platelia and EIA-Bmd, 50% EIA-Biotest, 58% EIA-Sorin. The sensitivity for IgG was greater with EIA-Bmd and EIA-Biotest, especially in detection of IgG in acute-phase serum : 61% EIA-Bmd and EIA-Biotest, 15% EIA-Platelia and 31% EIA-Sorin. Discrepant and unexpected results were observed in IgM detection from control healthy patients using EIA-Sorin and EIA-Biotest, confirming the lack of specificity of these two EIA-tests and making them inaccurate for routine diagnosis. A high IgG seroprevalence were found in healthy adults by the four EIAs (43-70%). In healthy children, EIA-Bmd and EIA-Biotest gave a higher IgG seroprevalence than EIA-Sorin and EIA-Platelia (45% each for the former as compared to 17% and 20%, respectively, for the latter).These results confirm that the IgM EIA serology test is a valuable tool for the early diagnosis of M. pneumoniae infections in children, as long as the EIA test used is specific. In adults, the difficult interpretation of EIA tests suggests that paired sera, combined with PCR detection on respiratory tract specimens collected on admission of patient, should be required for accurate diagnosis.

Evaluation of four commercial immunoglobulin G (IgG)- and IgM-specific enzyme immunoassays for diagnosis of Mycoplasma pneumoniae infections

The four following commercially available enzyme immunoassays (EIAs) were assessed and compared for their performance in detecting Mycoplasma pneumoniae immunoglobulin G (IgG)- and IgM-specific antibodies Platelia EIA, ImmunoWELL M. pneumoniae ELISA IgG and IgM, ETI-MP-IgG and IgM EIAs and Biotest anti-M. pneumoniae IgG and IgM ELISA (referred to herein as EIA-Platelia, EIA-BMD, EIA-Sorin, and EIA-Biotest). Three groups of patients were investigated: 39 patients (27 children and 12 adults) with respiratory infections who tested positive by PCR for M. pneumoniae in respiratory specimens (group I; 52 serum samples), 61 healthy children and adults (group II; 61 serum samples), and 20 patients with rheumatoid factor or antinuclear antibodies, or who tested positive for antiviral IgM (group III; 20 serum samples). In group III, the IgM specificity for EIA-Platelia, EIA-BMD, EIA-Biotest, and EIA-Sorin was 100, 90, 65, and 25%, respectively. In the children from group I, the four EIAs had similar IgM sensitivities (89 to 92%); the sensitivity for IgG was greater with EIA-BMD and EIA-Biotest than with EIA-Platelia and EIA-Sorin (66 and 78% versus 55 and 52%, respectively). In adult patients from group I, 9 to 10 serum samples were positive for IgG with a concordant sensitivity of 75 to 83% between the four EIAs but a striking difference in IgM sensitivity: 16% by EIA-Platelia and EIA-BMD, 50% by EIA-Biotest, and 58% by EIA-Sorin. Discrepant and unexpected results were observed in IgM detection from control healthy patients using EIA-Sorin and EIA-Biotest, confirming the lack of specificity of these two EIAs and making them inaccurate for routine diagnosis. A good concordance of IgG seroprevalence in healthy adults was found between the four EIAs (66 to 70%), though this concordance was lower with EIA-Platelia (43%). In healthy children, EIA-BMD and EIA-Biotest gave a higher IgG seroprevalence than EIA-Sorin and EIA-Platelia (45% each for the former compared to 17 and 20%, respectively, for the latter). These results confirm that the IgM EIA serology test is a valuable tool for the early diagnosis of M. pneumoniae infections in children, as long as the EIA used is specific. In adults, the difficult interpretation of EIAs suggests that paired sera, combined with PCR detection on respiratory tract specimens collected on admission of patient, should be required for accurate diagnosis.

16S rRNA based polymerase chain reaction compared with culture and serological methods for diagnosis of Mycoplasma pneumoniae infection

The use of a 16S rRNA based polymerase chain reaction (PCR) for the detection of Mycoplasma pneumoniae infection was investigated. Sputum samples from 34 patients with respiratory illness and evidence of pneumonia as judged by chest X-ray were analyzed by PCR and microbiological culture. Throat swabs from 14 healthy individuals were used as controls. For serology, an enzyme immunoassay for the detection of immunoglobulin M antibodies and a complement fixation assay were performed. Evidence of Mycoplasma pneumoniae infection was obtained in ten patients (29%), eight of whom were found positive by both PCR and serology. Two of the sputum samples from these eight patients were negative by culture. Of the remaining two patients positive for Mycoplasma pneumoniae, one was positive by PCR and culture but negative by serology, and one was found positive by serology but negative by PCR and culture. Thirteen of the 14 controls were negative by both PCR and serology. One control, however, was negative by serology but positive by PCR, which was probably due to asymptomatic carriage of Mycoplasma pneumoniae. The results of this study indicate the suitability of the PCR for the detection of Mycoplasma pneumoniae in clinical samples as well as its potential value as an additional tool for the diagnosis of infection.

Rapid, sensitive detection of Mycoplasma pneumoniae in simulated clinical specimens by DNA amplification

The polymerase chain reaction (PCR) was investigated as a means of diagnosing Mycoplasma pneumoniae infections. The target DNA sequence was a 375-bp segment of the P1 virulence protein. This DNA segment was amplified in pure cultures of five different strains of M. pneumoniae but not in other species of Mycoplasma, Acholeplasma, or Ureaplasma that were tested. Simulated clinical specimens were used to compare PCR, culture, and the gene probe. The sensitivity of PCR was between 1 and 10 organisms. The sensitivity of culture was approximately 10(3) organisms, and the gene probe detected between 10(4) and 10(5) organisms. These results indicate that PCR has significant potential as a rapid, sensitive method for detecting M. pneumoniae in clinical specimens.

Enzyme immunoassay for detection of immunoglobulin M (IgM) and IgG antibodies to Mycoplasma pneumoniae

An enzyme immunoassay (EIA) for detection of immunoglobulin M (IgM) and IgG antibodies to Mycoplasma pneumoniae was developed. The EIA was evaluated on the basis of results in the M. pneumoniae complement fixation (MPCF) test and the cold agglutinin test. Serum samples from 430 patients with respiratory infections of known or unknown etiology, from 91 healthy children and adults and from 20 patients with rheumatoid factor, were investigated. By the criteria chosen for positive diagnostic EIA values, we found that the combined measurement of specific IgM and IgG gave a specificity of 99.7% and a sensitivity of 97.8%. If only IgM antibodies were measured, the specificity was 100% and the sensitivity was 88%. For IgG alone the specificity was 99.7%, but the sensitivity was only 46% because of the high EIA cutoff value chosen for IgG. We found no false positives among serum samples from patients with non-M. pneumoniae respiratory infection of known etiology, and there were no false IgM positives due to rheumatoid factor. In some cases the IgM EIA results became positive earlier in the course of illness than the MPCF titer. While children and teenagers responded predominantly with IgM antibodies, patients older than 40 years often had an IgG response only (56% of cases), probably because of reinfection. We conclude that this EIA is a good alternative to the combined MPCF and cold agglutinin tests in the diagnosis of M. pneumoniae infection.

Evaluation of a commercial enzyme immunoassay for detection of Mycoplasma pneumoniae specific immunoglobulin G antibodies

A commercial enzyme immunoassay (Platelia Mycoplasma, Diagnostics Pasteur) for the diagnosis of Mycoplasma pneumoniae [corrected] infections was evaluated and found not to be suitable for the purpose. More than 80% of healthy persons and patients with non-Mycoplasma pneumoniae respiratory infection, all with a negative Mycoplasma pneumoniae complement fixation test, had a positive EIA. Paired sera did not show the positive correlation between a rise in complement fixation titre and the EIA ratio reported by the manufacturer.

Rapid immunoblot method for diagnosis of acute Mycoplasma pneumoniae infection

A rapid immunoblotting technique based on the IgM response to a major immunogenic protein is described for the diagnosis of Mycoplasma pneumoniae infection. Using results of the complement fixation test as the criterion for diagnosis, the rapid immunoblot method was positive in 95.7% of patients. The sensitivity was reduced to 81.9% if the test was performed on either single sera or acute sera only from serum pairs. Although the few sera that failed to demonstrate a positive IgM response were more likely to be from older patients, there was a consistent IgM response recorded for both younger (less than 20 years) and older (greater than or equal to 20 years) patients.

Development of urease conjugated enzyme-linked immunosorbent assays (ELISA) for the detection of IgM and IgG antibodies against Mycoplasma pneumoniae in human sera

Urease conjugated enzyme linked immunosorbent assays (ELISA) were developed for the detection of human IgM and IgG antibodies against Mycoplasma pneumoniae. Results obtained by ELISA were compared with complement fixation test (CFT); which showed that of the 214 serum specimens tested, 80 were found to have antibody against M. pneumoniae. ELISA revealed that 70 of these specimens were IgG antibody, and 27 of them also contain IgM antibody. CFT failed to detect the presence of antibody against M. pneumoniae in five serum specimens tested. However, by using ELISA, three of them were found to have IgG and IgM antibodies. and the other two sera have IgG antibody only. Four out of the five specimens tested were the first serum specimens collected from patients with clinical and serological evidence of M. pneumoniae infection. In addition, 28 serum specimens, including 10 sera containing IgM rheumatoid factors and sera known to contain IgM antibody to other infectious organisms, were also tested for IgM antibody against M. pneumoniae by ELISA. None of these specimens showed a nonspecific reaction. ELISA had a sensitivity of 87.5% and a specificity of 96.3% when compared with CFT. Thus, ELISA developed in our laboratory is a specific test, and the results indicated that IgM ELISA might be used as a rapid diagnosis for M. pneumoniae infection.

Enzyme-linked immunosorbent assay for detection of Mycoplasma pneumoniae specific immunoglobulin M

An ELISA was developed for the detection of IgM antibodies to Mycoplasma pneumoniae in human sera, using microtiter plates coated with rabbit antiserum to human IgM selecting for IgM antibodies in the first reaction step. The specific antibodies were detected using enzyme-labelled, detergent-solubilized antigen. The complement fixation test was used as reference method. In a prospective study of 59 patients with community-acquired pneumonia, 13 of whom had evidence of mycoplasmal etiology, the ELISA was shown to have high specificity (97%). In samples taken seven days after onset of the disease all complement-fixation positive samples (n = 20) but one were positive, demonstrating the diagnostic value of a positive test in samples taken after that period.

Red-cell IgM-antibody capture assay for the detection of Mycoplasma pneumoniae-specific IgM

A red-cell IgM-antibody capture assay has been developed for detecting Mycoplasma pneumoniae-specific IgM, which is based on the adsorption or 'capture' of IgM from patients' sera onto so-called 'inagglutinable' bovine red cells, chemically linked with anti-human mu. When M. pneumoniae antigen is added to the system, the red cells agglutinate in the presence of M. pneumoniae-specific IgM. The test was compared with the mu-capture ELISA described by Wreghitt & Sillis (1985), and was found to give comparable results. The two tests had similar sensitivity and specificity and could detect M. pneumoniae-specific IgM for a similar time (up to 6 months) after proven M. pneumoniae infection. However, the red-cell antibody capture assay is a much more simple and rapid test, taking only 1 h to perform (compared to 24 h for mu-capture ELISA). The red-cell IgM-antibody capture assay is therefore amenable to rapid diagnosis of M. pneumoniae infection and the institution of early appropriate antibiotic therapy.

Detection of specific IgM antibodies for the diagnosis of Mycoplasma pneumoniae infections: a clinical evaluation

The diagnostic value of detection of specific IgM antibodies was analysed in Mycoplasma pneumoniae infections. In a retrospective clinical and serological study, M. pneumoniae IgM antibodies were determined by a mu-capture ELISA using enzyme-labelled antigen. The study group consisted of 91 patients with significantly raised titers in paired sera or a single high titer of complement fixation antibodies. About 40% of the patients had been treated with antibiotics ineffective against M. pneumoniae infections prior to admission to hospital. Treatment with erythromycin or tetracycline was shown to give a shorter period of fever compared to if no or ineffective therapy was given. Specific IgM antibodies were detected in about 80% of sera sampled 9 days or more after onset of symptoms. In sera sampled at 7-8 days after onset IgM antibodies were found in about 40% of the sera but only occasionally in sera sampled earlier. In the age group 0-20 years 88% of the patients developed an IgM response. In the higher ages (greater than 60 years) a significantly lower rate of IgM responders was observed.

Demonstration of cross-reactive antibodies to mycoplasmas in human sera by ELISA and immunoblotting

Varying levels of cross-reactivity to some mycoplasma species were observed in the sera of patients infected with Mycoplasma pneumoniae and even in normal human sera by enzyme-linked immunosorbent assay (ELISA). The absorption of the patients' sera with M. pneumoniae lysate showed the decrease in ELISA titers not only to M. pneumoniae, but also to other mycoplasma species. These results suggested the existence of cross-reactive antibodies to mycoplasmas in human sera. Cross-reactive antibodies to M. pneumoniae and other mycoplasmas in the patients' sera were also demonstrated by Western blotting technique.

Specific immunoglobulin M enzyme-linked immunosorbent assay for confirming the diagnosis of measles

An enzyme-linked immunosorbent assay (ELISA) was evaluated for the detection of measles virus-specific immunoglobulin M (IgM) (MIgM). The ELISA was standardized by deriving a seronegative range of values from sera which should not contain MIgM (24 cord sera, 59 sera from immune health care workers, and 47 sera from infants before the administration of measles vaccine). These values were separable from those obtained from individuals convalescing from measles. Twenty sera containing rheumatoid factor were MIgM seronegative. Of 30 acute-phase sera from suspected measles cases, 26 contained MIgM; those that were seronegative were obtained on day 0, 0, 2, or 9. All 25 convalescent-phase samples contained MIgM. Of the 25 paired samples, 22 were IgG positive at the first sampling; 3 of the 22 did not show a rise in IgG titer. The MIgM ELISA can be used for confirming suspected measles cases, often requiring only a single serum specimen.

A 168-kilodalton protein of Mycoplasma pneumoniae used as antigen in a dot enzyme-linked immunosorbent assay

The attachment protein of Mycoplasma pneumoniae (molecular weight 168 kd) was used as antigen in a special enzyme-linked immunosorbent assay (dot ELISA) and compared with a sonicate of the whole organism. In control sera the intensity of the 168-kd band on immunoblots correlated well with the ELISA IgG values derived from isolated protein. The diagnostic significance of the 168-kd antigen was tested on paired sera from 33 patients with Mycoplasma pneumoniae infection (24 children, 9 adults). The ELISA values with the isolated protein were slightly lower than with cell antigen, but the protein also showed a lower basic activity in controls. In first sera of specimens of children collected within the first week of infection the 168-kd IgM response was more distinct than that to the whole cell antigen. Similarly the IgG response to the purified protein antigen differed significantly from the controls already in the first serum. In sera of adult patients the increased levels of IgG antibody were more evident with the 168-kd protein antigen. Use of the protein 168 kd as antigen increased the sensitivity of the ELISA for detecting early stages of disease, especially in children.

Reaction pattern of human anti-Mycoplasma pneumoniae antibodies in enzyme-linked immunosorbent assays and immunoblotting

In serological diagnosis of Mycoplasma pneumoniae disease the frequently used complement fixation test is based on a cross-reacting glycolipid. Recently enzyme-linked immunoassays have been developed to overcome this lack of specificity. To study the involvement of the various proteins and the influence of age on the level of antiprotein antibodies present, we investigated by enzyme-linked immunoassays (immunoglobulin M [IgM] and IgG) and immunoblotting the sera of healthy persons of different age groups as well as sera of patients (including paired sera) with M. pneumoniae infection. In sera of children with nonrespiratory diseases and in healthy blood donors the IgM antibodies rose during the first 2 years of life to a relatively constant background level (optical density at 405 nm of 0.15 to 0.21). In contrast IgG remained low up to the seventh year and then increased to moderate levels (optical density of 0.15). The blotting patterns showed few IgM bands in the age group of 20 to 30 years. IgG blots revealed, up to 7 years, only very few reactions with a 168-kilodalton protein, but in higher age groups a considerable number of reactions with proteins of 193, 168, 84, 69, and 56 kilodaltons were detected. In the sera of patients, positive IgM blots were most numerous in the third week, whereas the number of IgG blots increased up to the fourth and the fifth week. At this time all sera contained antibodies against the 168-kilodalton protein, which is identical with the adhesin of M. pneumoniae. In a patient with acute infection, who had a high preinfection IgG level, no IgM response developed. The data indicate a relatively high background of antibodies against M. pneumoniae proteins in older age groups, suggesting a requirement for paired sera. Furthermore, reinfections of adults may occur without a concomitant IgM response.

The serological diagnosis of Mycoplasma pneumoniae infection: a comparison of complement fixation, haemagglutination and immunofluorescence

A total of 193 sera were examined for antibody to Mycoplasma pneumoniae by three techniques - complement fixation (CF), haemagglutination (HA) and immunofluorescence (IF), the last method being used to assess IgM, IgG and IgA antibodies. The most reliable single test for diagnosis was HA, and the most useful combination of tests was HA with IF (IgM and IgG). The IgA IF was not found to be diagnostically helpful.

A micro-capture ELISA for detecting Mycoplasma pneumoniae IgM: comparison with indirect immunofluorescence and indirect ELISA

A mu-capture ELISA was developed for detecting Mycoplasma pneumoniae-specific IgM, and compared with an indirect immunofluorescent antibody (IFA) technique and an indirect ELISA. mu-capture ELISA and IFA compared well and were found to be the most sensitive assays. The IFA test can be completed in 2 h whilst the results of the mu-capture ELISA can be available in 24 h. Both tests are amenable to routine diagnostic use and have similar sensitivity. Indirect ELISA was found to be less sensitive and less specific, giving high assay values with several sera having undetectable M. pneumoniae CF antibody or CF antibody in low titre. Serum samples obtained from 11 patients at various times after M. pneumoniae infection showed maximum antibody levels within the first month by all assays, with a gradual fall in amount of IgM with time when assayed by mu-capture ELISA, a more gradual decline by IFA and hardly any decline with indirect ELISA. It was concluded that the indirect ELISA is unsuitable for the investigation of possible M. pneumoniae infection because the sustained high assay values with serum samples taken many months after infection, make interpretation of the test results very difficult.

Adherence inhibition assay: a specific serological test for detection of antibodies to Mycoplasma pneumoniae

Antibodies directed against the adherence-mediating protein of Mycoplasma pneumoniae were measured by an adherence inhibition assay. Pretreatment with antibody-containing sera reduced the attachment of sheep erythrocytes to Mycoplasma pneumoniae layers grown in flat-bottom microtiter plates. The degree of attachment of erythrocytes was estimated by lysis with distilled water and measurement of absorbance in a microtiter reader. Sera tested included 126 sera from patients with suspected Mycoplasma pneumoniae respiratory infection and 60 sera from patients with serologically confirmed respiratory infection of other origin. Examination of human sera by both complement fixation using glycolipid as antigen, and the adherence inhibition assay indicated a high degree of specificity of the latter. Furthermore, titer increases parallel to complement fixation titers were found in six paired sera, and testing of separated IgM showed high reactivity in this immunoglobulin fraction. The adherence inhibition assay is a reproducible method which is relatively easy to perform. It may be of importance especially when a non-specific complement fixation reaction due to cross-reaction is suspected.