Laboratory diagnosis of Mycoplasma pneumoniae infection. 2. Comparison of methods for the direct detection of specific antigen or nucleic acid sequences in respiratory exudates

The first assessment to detect Mycoplasma hyopneumoniae by sampling laryngeal swabs to investigate sow stability in South Korea

Background

Mycoplasma hyopneumoniae (M. hyopneumoniae), a representative pathogen causing swine enzootic pneumonia, generally infects piglets vertically. However, it is difficult to ascertain the M. hyopneumoniae infection state of sows due to limited detection methods. This report investigated sow herd stability by applying nested PCR to laryngeal swabs of suckling pigs, which is reportedly the most sensitive method.

Results

M. hyopneumoniae was detected in 14 farms (63.6%) and 127 piglets (6.5%). The prevalence of sows likely to transmit M. hyopneumoniae in herds (11.1%) was calculated. In addition, there was a significant difference in detection rates among farms depending on herd size, gilt replacement rate, acclimation method, and antibiotic usage, suggesting various parameters that influence sow stability.

Conclusions

The results demonstrated that laryngeal swabs from suckling pigs have provided useful information regarding vertical transmission from sows in South Korean farm conditions. This result demonstrated that farms with larger herd sizes, higher gilt replacement rates, and a practice of naturally exposing gilts for acclimation had higher detection rates in weaning piglets, indicating an unstable sow infection state.

A sensible technique to detect mollicutes impurities in human cells cultured in GMP condition

In therapeutic trials the use of manipulated cell cultures for clinical applications is often required. Mollicutes microorganism contamination of tissue cultures is a major problem because it can determine various and severe alterations in cellular function. Thus methods able to detect and trace cell cultures with Mollicutes contamination are needed in the monitoring of cells grown under good manufacturing practice conditions, and cell lines in continuous culture must be tested at regular intervals. We here describe a multiplex quantitative polymerase chain reaction assay able to detect contaminant Mollicutes species in a single-tube reaction through analysis of 16S-23S rRNA intergenic spacer regions and Tuf and P1 cytoadhesin genes. The method shows a sensitivity, specificity, and robustness comparable with the culture and the indicator cell culture as required by the European Pharmacopoeia guidelines and was validated following International Conference on Harmonization guidelines and Food and Drug Administration requirements.

Development and validation of a multiplex quantitative polymerase chain reaction assay for the detection of Mollicutes impurities in human cells, cultured under good manufacturing practice conditions, and following European Pharmacopoeia requirements and the International Conference on Harmonization guidelines

BACKGROUND AIMS

The clinical applications of in vitro manipulated cultured cells and their precursors are often made use of in therapeutic trials. However, tissue cultures can be easily contaminated by the ubiquitous Mollicutes micro-organisms, which can cause various and severe alterations in cellular function. Thus methods able to detect and trace Mollicutes impurities contaminating cell cultures are required before starting any attempt to grow cells under good manufacturing practice (GMP) conditions.

METHODS

We developed a multiplex quantitative polymerase chain reaction (qPCR) assay specific for the 16S-23S rRNA intergenic spacer regions, for the Tuf and P1 cytoadhesin genes, able to detect contaminant Mollicutes species in a single tube reaction. The system was validated by analyzing different cell lines and the positive samples were confirmed by 16S and P1 cytoadhesin gene dideoxy sequencing.

RESULTS

Our multiplex qPCR detection system was able to reach a sensitivity, specificity and robustness comparable with the culture and the indicator cell culture method, as required by the European Pharmacopoeia guidelines.

CONCLUSIONS

We have developed a multiplex qPCR method, validated following International Conference on Harmonization (ICH) guidelines, as a qualitative limit test for impurities, assessing the validation characteristics of limit of detection and specificity. It also follows the European Pharmacopoeia guidelines and Food and Drug Administration (FDA) requirements.

Development and evaluation of a loop-mediated isothermal amplification assay for rapid detection of Mycoplasma pneumoniae

A loop-mediated isothermal amplification (LAMP) assay for the rapid detection ofMycoplasma pneumoniaewas developed and evaluated. The assay specifically amplified onlyM. pneumoniaesequences, and no cross-reactivity was observed for otherMycoplasmaspecies or respiratory bacterial species. The detection limit for this assay was found to be 2 × 102copies, corresponding to 2–20 colour changing units ofM. pneumoniaein 1 h, as observed in a real-time turbidimeter and electrophoretic analysis. The accuracy of the LAMP reaction was confirmed by restriction endonuclease analysis as well as direct sequencing of the amplified product. The assay was applied to 95 nasopharyngeal swab samples collected from patients or from healthy individuals, and compared to a real-time PCR assay in-house. A concordance of 100 % was observed between the two assays. The LAMP assay is easy to perform, shows a rapid reaction and is inexpensive. It may therefore be applied in the routine diagnosis ofM. pneumoniaeinfection in the clinical laboratory.

Mycoplasma pneumoniae and central nervous system complications: a review

Mycoplasma pneumoniae is a common cause of community-acquired pneumonia. Little is known about the extrapulmonary manifestations of this organism. Numerous central nervous system (CNS) manifestations have been described with M. pneumoniae. CNS involvement is probably the most common site of involvement in addition to the respiratory system. Up to 7% of patients hospitalized with M. pneumoniae may have CNS symptoms. Common CNS presentations include encephalitis, aseptic meningitis, polyradiculitis, cerebellar ataxia, and myelitis. The mechanism behind these CNS manifestations remains unclear. Direct invasion, neurotoxin production, or an immune-mediated mechanism has been proposed. Newer diagnostic techniques for the direct detection of the antigen and the microorganism are proving useful for the detection of extrapulmonary disease. This review comprehensively reviews the CNS complications that have been reported with M. pneumoniae.

Expression and immunological characterization of the carboxy-terminal region of the P1 adhesin protein of Mycoplasma pneumoniae

Mycoplasma pneumoniae is the causative agent of primary atypical pneumonia in humans. Adherence of M. pneumoniae to host cells requires several adhesin proteins, such as P1, P30, and P116. A major limitation in developing a specific diagnostic test for M. pneumoniae is the inability to express adhesin proteins in heterologous expression systems due to unusual usage of the UGA stop codon, leading to premature termination of these proteins in Escherichia coli. In the present study, we successfully expressed the C-terminal (P1-C1) and N-terminal (P1-N1) regions of the P1 protein in E. coli. On screening these recombinant proteins with sera from M. pneumoniae-infected patients, only the P1-C1 protein was found to be immunogenic. This protein can be used as an antigen for immunodiagnosis of M. pneumoniae infection, as well as in adherence inhibition studies to understand the pathophysiology of the disease.

Immune response to Mycoplasma pneumoniae P1 and P116 in patients with atypical pneumonia analyzed by ELISA

Background

Serology is often used for the diagnosis of Mycoplasma pneumoniae. It is important to identify specific antigens that can distinguish between the presence or absence of antibodies against M. pneumoniae. The two proteins, P116 and P1, are found to be immunogenic. By using these in ELISA it is possible to identify an immune response against M. pneumoniae in serum samples.

Results

A recombinant protein derived from the P116 protein and one from the P1 protein were used in two ELISA tests, rP116-ELISA and rP1-ELISA. Human serum samples from patients with atypical pneumonia were tested and compared to the results of the complement fixation test. There was a good agreement between the two tests but the rP1-ELISA showed the best discrimination between positive and negative samples.

Conclusion

Two ELISA tests based on recombinant proteins have been analysed and compared to the complement fixation test results. The two ELISA tests were found suitable for use in serodiagnostics of M. pneumoniae infections. The use of specific antigens eliminates the risk of cross reaction to an immune response against other bacteria.

Detection of Mycoplasma pneumoniae by real-time nucleic acid sequence-based amplification

Real-time isothermal nucleic acid sequence-based amplification (RT-NASBA) was applied to the detection of Mycoplasma pneumoniae. In vitro-generated M. pneumoniae RNA was used to assess the sensitivity of the assay. The 95% hit rate was 148 molecules of M. pneumoniae RNA in the amplification and 10(4) molecules of in vitro-generated RNA after nucleic acid extraction. The sensitivity of the RT-NASBA and the conventional NASBA assays corresponded to 5 color-changing units (CCU) of M. pneumoniae. In spiked throat swabs, nasopharyngeal aspirates, bronchoalveolar lavages, and sputum, the sensitivity of both NASBA assays corresponded to 5 to 50 CCU of M. pneumoniae. A total of 17 clinical specimens positive for M. pneumoniae by PCR were also positive by conventional NASBA, but one specimen was negative by RT-NASBA. These results indicate that the sensitivity of detection of M. pneumoniae by RT-NASBA in respiratory samples might be slightly reduced compared to that by conventional NASBA. However, the real-time assay is superior in speed and ease of handling.

Laboratory diagnosis of Mycoplasma pneumoniae infection

Diagnosis of Mycoplasma pneumoniae infection is challenging due to the fastidious nature of the pathogen, the considerable seroprevalence, and the possibility of transient asymptomatic carriage. During recent years, various new techniques have been adapted for the diagnosis of M. pneumoniae infection, notably in the field of molecular biology. Standard polymerase chain reaction (PCR) is currently the method of choice for direct pathogen detection, but several PCR-related methods provide enhanced sensitivity or more convenient handling procedures, and have been successfully applied for research purposes. Among these techniques are real-time PCR, nested PCR, reverse transcriptase PCR (RT-PCR) and multiplex PCR. Generally, amplification-based methods have replaced hybridization assays and direct antigen detection. Serology, which is the basic strategy for mycoplasma diagnosis in routine clinical practice, has been improved by the widespread availability of sensitive assays for separate detection of different antibody classes. For the diagnosis of mycoplasma pneumonia, serology and direct pathogen detection should be combined. Extrapulmonary diseases may be diagnosed by direct pathogen detection alone, but the value of this diagnostic approach is limited by the probably immunologically mediated pathogenesis of some manifestations. This review summarizes the current state of Mycoplasma pneumoniae diagnosis, with special reference to molecular techniques. The value of different methods for routine diagnosis and research purposes is discussed.

Detection of Mycoplasma pneumoniae in spiked clinical samples by nucleic acid sequence-based amplification

Isothermal nucleic acid sequence-based amplification (NASBA) was applied to the detection of Mycoplasma pneumoniae. M. pneumoniae RNA prepared from a plasmid construct was used to assess the sensitivity of the assay, and an internal control for the detection of inhibitors was constructed. The sensitivity of the NASBA assay was 10 molecules of wild-type M. pneumoniae RNA generated in vitro and 5 color-changing units (CCU) of M. pneumoniae. An appropriate specimen preparation procedure was developed: after protease treatment of the respiratory specimens, guanidine thiocyanate lysis solution (4.7 M guanidine thiocyanate [Sigma-Aldrich NV], 46 mM Tris-HCl [Merck, Darmstadt, Germany], 20 mM EDTA [Sigma-Aldrich NV], 1.2% [wt/vol] Triton X-100 [Sigma-Aldrich NV], pH 6.2.) was added. With spiked throats, nasopharyngeal aspirates, bronchoalveolar lavage specimens, and sputum specimens, the sensitivity of the NASBA assay in the presence of the internal control was 2 x 10(4) molecules of in vitro-generated RNA or 5 CCU of M. pneumoniae. The sensitivity of the NASBA assay was comparable to that of a PCR targeted to the P1 adhesin gene. Fifteen clinical specimens positive for M. pneumoniae by PCR were also positive by NASBA. These results indicate that the sensitivity of detection of M. pneumoniae in spiked respiratory samples by NASBA is high. Together with the use of the internal control, the assay merits evaluation as a diagnostic tool.

Pneumonia due to unusual organisms in children

Generally antimicrobials for treatment of pneumonia are chosen to target the usual bacterial etiological agents. Such regimens are unable to cure patients of pneumonia caused by 'unusual organisms' mycoplasma, chlamydia, Pneumocystis carinii and Legionella pneumophilus). Thus, there is a need to anticipate their presence in appropriate cases and to plan the initial antimicrobial therapy accordingly. Studies in Europe as well as India have shown that such infections form a fairly substantial percentage of community acquired pneumonia in children. Mycoplasma pneumoniae and Chlamydia pneumoniae are common in school age children while Chlamydia trachomatis occurs in early infancy. Pneumocystis carinii is an important pathogen in immunocompromised children. Routine laboratory tests and radiological features are not specific enough to give accurate diagnosis of these infections for which one has to depend on sophisticated culture techniques, immunological tests for the antigens or antibodies and polymerase chain reaction. Mycoplasma, chlamydia and legionella infections respond to macrolide antibiotics and for pneumocystis infections, trimethoprim-sulfamethaxozole or pentamidine is the drug of choice. Overall prognosis with appropriate treatment is good except for P. carinii infection in immunocompromised host which carries a high mortality and recurrence rate.

Molecular approaches to diagnosis of pulmonary diseases due to Mycoplasma pneumoniae

In this prospective study, the use of a culture-enhanced PCR assay for the detection of Mycoplasma pneumoniae, followed by hybridization with a specific probe (MP-HPCR) or without hybridization (MP-PCR), and the use of a nested PCR (MP-NPCR) were evaluated. Clinical samples (190 specimens) from 190 patients with respiratory complaints were incubated in culture broth overnight and then subjected to PCR. The results of the PCR were compared to those obtained by culture, the direct antigen test, and serologic testing by microparticle agglutination and by immunoblotting in unclear cases. The sensitivities were 19 CFU for MP-PCR, 1.9 CFU for MP-HPCR, and 0.019 CFU for MP-NPCR. PCR amplification of the beta-globin gene was possible in 98% of cases: after dilution of the beta-globin-negative samples, all samples were reactive. Correlation between negative MP-NPCR results and negative serology results was found in 89% of cases; a positive correlation was found with 10% of the patients. Samples from three immunocompromised patients were MP-NPCR positive but serologically negative. High respiratory colonization by M. pneumoniae (>10(5) CFU/ml) in patients with acute respiratory disease could be detected by culture, MP-PCR, and MP-NPCR. These results indicate that MP-PCR and MP-NPCR are reliable methods for the detection of M. pneumoniae in respiratory tract samples of patients with respiratory complaints.

Rapid detection of Mycoplasma pneumoniae by an assay based on PCR and probe hybridization in a nonradioactive microwell plate format

A new molecular assay, based on a rapid DNA extraction protocol, PCR, and hybridization to a specific probe in a nonradioactive microwell plate format was used to detect Mycoplasma pneumoniae in bronchoalveolar fluid specimens. The sensitivity of the assay was determined to be 10 to 100 organisms with M. pneumoniae reference strains. Specificity testing with different bacteria capable of producing pneumonia showed no cross-reactivity. In a prospective study, bronchoalveolar lavage fluids obtained from patients with pneumonia were investigated with the PCR assay and compared to culture. Twelve positive samples were detected with the PCR assay. Seven of them were subsequently confirmed by culture. All patients with positive PCR results seroconverted. Application of the PCR assay described may lead to safe and early diagnosis of M. pneumoniae in patients with pneumonia.

Detection of Mycoplasma pneumoniae by polymerase chain reaction in lung aspirates from patients with community-acquired pneumonia

STUDY OBJECTIVE

This study was designed to evaluate the usefulness of polymerase chain reaction (PCR) to detect Mycoplasma pneumoniae DNA in samples obtained by transthoracic needle aspiration (TNA).

DESIGN

Prospective study of cases.

SETTING

A university hospital in Lleida, Spain.

PATIENTS

A total of 101 unselected patients, admitted between January 1993 and March 1994 in the emergency department, with a clinical and radiologic picture of community-acquired pneumonia, and without contraindications for TNA application.

INTERVENTIONS

Patients were studied with conventional diagnostic techniques for community-acquired pneumonia. In addition, a sample obtained by TNA was processed by the following methods: culture in standard media, culture in selective media for Legionella, detection of capsular antigens for Streptococcus pneumoniae and Haemophilus influenzae, and detection of M pneumoniae specific genome by PCR.

RESULTS

Serologic data were not available in eight patients and were excluded from this analysis. M pneumoniae PCR amplification was possible in eight cases, well correlated with serologic responses indicating current infection. Samples from ten additional patients, negative by PCR, were found to be demonstrative of recent M pneumoniae infection by serologic study. Finally, in all the remaining 75 cases, including the 59 patients for whom a different microbial diagnosis was established, M pneumoniae PCR test gave negative results.

CONCLUSION

This study indicates that PCR, applied to samples obtained by TNA, appears to be a moderately sensitive and highly specific method for rapid detection of M pneumoniae lung infection.

Phylogeny based on elongation factor Tu reflects the phenotypic features of mycoplasmas better than that based on 16S rRNA

A universal phylogenetic tree of organisms from all kingdoms was constructed by the use of elongation factor Tu (EF-Tu) as the marker molecule. As in the 16S ribosomal RNA (16S rRNA)-based phylogeny, the EF-Tu tree divides eukaryotes, archaebacteria, and prokaryotes into three main branches. Furthermore, the EF-Tu-based tree shows, in contrast to the 16S rRNA tree, some interesting evolutionary relationships between mycoplasmas, better reflecting phenotypic features of these organisms.

Performance of Meridian ImmunoCard Mycoplasma test in a multicenter clinical trial

Serology is the principal laboratory method used to diagnose Mycoplasma pneumoniae infection. Meridian Diagnostics has developed the ImmunoCard Mycoplasma kit, a 10-min card-based enzyme-linked immunosorbent assay (ELISA) designed to detect immunoglobulin M (IgM) antibodies to M. pneumoniae. We compared the ImmunoCard with two M. pneumoniae IgM-specific assays (immunofluorescence assay [IFA] and ELISA) and a standard complement fixation (CF) procedure using 896 specimens submitted to clinical laboratories for M. pneumoniae serology. Equivocal results obtained by CF, IFA, or ELISA were resolved by testing with an additional method or by reviewing patient chart information. The ImmunoCard had sensitivities ranging from 74% compared with the ELISA to 96% compared with CF results with IFA. ImmunoCard specificities ranged from 85% compared with the IgM-specific ELISA to 98% compared with IgM-specific IFA results resolved with clinical chart review. We also compared the ImmunoCard results with consensus results of 694 specimens tested on at least two non-ImmunoCard methods because of the lack of a "gold standard" for M. pneumoniae serology. Overall, the ImmunoCard Mycoplasma IgM assay had 90% sensitivity, 93% specificity, and 92% agreement with the consensus results. The ImmunoCard is technically less complex and requires less equipment that the three other assays. Our results indicate that the ImmunoCard Mycoplasma IgM assay is a valid and simple procedure which can reduce technologist time (and, thus, labor cost) and turnaround time for laboratories analyzing small numbers of specimens (< 10 per batch) submitted for IgM anti-M. pneumoniae testing.

Diagnosis of Mycoplasma pneumoniae pneumonia in pediatric patients by polymerase chain reaction (PCR)

Polymerase chain reaction (PCR) testing was performed on respiratory tract specimens obtained by throat swab in 21 children admitted to the hospital with suspected Mycoplasma pneumoniae pneumonia. Of 13 patients with a clinical condition compatible with mycoplasma infection and an immunological response to M. pneumoniae, 11 were positive by PCR. Eight patients were negative by serology and/or had a clinical condition not compatible with mycoplasma infection, and all were negative by PCR. The antibody response to M. pneumoniae was delayed for a week or more in 3 (23%) of the 13 patients with documented mycoplasma infection. These results suggest that PCR performed on a respiratory tract specimen obtained by a throat swab may be useful in the initial evaluation of children with suspected M. pneumoniae pneumonia, especially in patients in whom the serological response is delayed.

Routine diagnosis of seven respiratory viruses and Mycoplasma pneumoniae by enzyme immunoassay

A composite EIA, using 8-well microstrips, was used for the rapid detection of seven respiratory viruses and M. pneumoniae. The viruses included influenza A and B, parainfluenza 1, 2 and 3, adenovirus and respiratory syncytial virus. During the 61 month period--June 1988 to June 1993--17326 respiratory specimens, submitted from three states, were tested by this EIA. The specimens were mainly from a paediatric population (hospitals and private physicians). RSV was the predominant virus detected, followed by adenovirus, parainfluenza 3, M. pneumoniae, influenza A, parainfluenza 2, influenza B and parainfluenza 1. The use of blocking antibodies confirmed the identification of the agents, in particular with samples showing absorbance values greater than the cutoff with more than one infectious agent. Different methods for processing specimens in order to obtain a uniform suspension, and interpretation of non-specific reactions, are discussed. The assays showed an average sensitivity of 85% and specificity of 99%, compared to virus culture. This EIA system provided an efficient method for the rapid diagnosis of viral and mycoplasmal infections in a busy diagnostic laboratory.

Direct PCR enables detection of Mycoplasma pneumoniae in patients with respiratory tract infections

The sensitivities of three methods of detection of Mycoplasma pneumoniae by a 16S rDNA PCR were compared by using a serial dilution of M. pneumoniae. These methods consisted of a PCR performed directly on cells after a proteinase K pretreatment (direct PCR), a PCR after purification of nucleic acids (DNA-PCR), and a PCR with rRNA sequences as the target after reverse transcription. The direct PCR and the reverse transcription PCR had a sensitivity of 1.5 CFU (approximately 250 genomes). By purification, a 10-fold loss of target DNA occurred, as shown by a 10-fold decrease in sensitivity (15 CFU) of the DNA-PCR. The presence of an excess of human background DNA did not influence the sensitivity of either PCR. The direct PCR was evaluated on samples from patients with respiratory complaints. Direct PCR amplification was possible in 94.9% of the samples, which were tested by amplification of a 326-bp fragment of the beta-globin gene, which was performed to test for the suitability of amplification. Nucleic acid purification was performed on the beta-globin-negative samples, after which only 2% remained negative. A positive correlation between the direct M. pneumoniae PCR and serology, as tested by the microparticle agglutination assay (MAG assay), was found in 88.1% of the cases. A positive MAG assay result was found for samples from 10 (17%) of the patients; samples from 6 (10.2%) of these patients were also positive by PCR. Samples from three patients were found to be positive by the M. pneumoniae PCR and negative by the MAG assay. Persistence of M. pneumoniae, as detected by PCR was observed in three patients. These results indicate that the direct PCR with 16S rDNA could prove to be useful in the detection of M. pneumoniae in respiratory tract samples, although more studies are needed to evaluate the correlation between clinical symptoms and positive test results.

Evaluation of an antigen-capture enzyme immunoassay for rapid diagnosis of Mycoplasma pneumoniae infection

A new enzyme immunoassay (EIA; Enzygost) for rapid detection of Mycoplasma pneumoniae antigen was evaluated in 51 young adults with acute respiratory infection. The EIA results using sputa and nasopharyngeal aspirates were compared with those of serological antibody tests, culture and a DNA probe. In sputum the sensitivity of the EIA ranged from 40% to 81% and the specificity from 64% to 100%, depending on the reference method. In nasopharyngeal aspirates the sensitivity was well below 20%, but the test was nearly 100% specific.

Laboratory diagnosis of Mycoplasma pneumoniae infection. 4. Antigen capture and PCR-gene amplification for detection of the Mycoplasma: problems of clinical correlation

Direct detection assays for Mycoplasma pneumoniae were established by PCR amplification of short sequences within the foot protein/adhesin (P1) gene and the 16S ribosomal RNA gene. Specificity and sensitivity was excellent, no hybridization was observed with M. genitalium and other human Mycoplasma species. In nose and throat washings from subjects with respiratory infection a pattern of high counts (c.f.u./ml) of M. pneumoniae (deduced from the amount of amplified PCR product), and a positive antigen capture assay, was found in 83% of subjects with serological evidence of current infection with M. pneumoniae. A small proportion of subjects with serological patterns suggesting infection in the more distant past had positive PCR assays. This was considered to represent either persistence of the organism from a previous infection or perhaps transient carriage during a reinfection, without substantial change in antibody response. PCR-based assay of M. pneumoniae offers a powerful, rapid, and sensitive substitute for culture of the mycoplasma. Antigen capture, while less sensitive than PCR, offers the advantage that it is more often positive with samples from current infection and requires less stringent laboratory organization to contain false positive results. We conclude however that the laboratory diagnosis of a chosen clinical episode should not rest on the PCR or Ag-EIA assays alone, but must also include antibody assays to confirm whether infection is current or represents persistence from past exposure.

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.

Outbreak of Mycoplasma pneumoniae infection among hospital personnel studied by a nucleic acid hybridization test

An outbreak of Mycoplasma pneumoniae (MP) infection occurred during the period March-May 1989 among the personnel of the Accident and Emergency Department of the Kuopio University Hospital, Kuopio, Finland. The index patient was a young male orderly, who fell ill with severe pneumonia. His tracheal mucus sample proved to be strongly positive for MP when tested by a commercial DNA-RNA hybridization test (Gen-Probe). After the index patient two additional staff members (an orderly and a nurse) fell ill with pneumonia and 66 others showed symptoms of upper respiratory infection or fever. The most frequent symptoms were a sore throat, a cough, rhinitis and headaches. All 97 employees of the department were tested for the presence of MP in April-May 1989 using throat swabs as test material. Forty-three (44%) were found to be positive for MP by the 'Gen-Probe' test. Eight (19%) of the MP positive staff were completely asymptomatic. The MP positive staff were retested about 3 weeks later, whereupon 40 (93%) had become negative. Most of the persons involved in this outbreak suffered only from mild respiratory symptoms, suggesting that MP outbreaks like the present one may easily pass unnoticed.

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.

Post-infectious encephalomyelitis associated with Mycoplasma pneumoniae and Legionella pneumophila infection

A case of severe acute encephalomyelitis associated with a serological diagnosis of both Mycoplasma pneumoniae and Legionella pneumophila infection is reported. Serological co-positivity between these two pathogens has been reported previously, and has, in general, been attributed to cross-reactivity. This is the first documented case of co-infection using more sensitive and specific serological techniques. The potential significance of these findings is discussed in the context of the considerable problems in the interpretation of serological data.

A latex agglutination test for the detection of Mycoplasma pneumoniae in respiratory exudates: a comparative study with a commercially available DNA-probe test

We prepared polyclonal antibody specific to Mycoplasma pneumoniae. Using this antibody, we developed a latex agglutination test (LAT) for detecting the organism in respiratory exudates as rapid diagnosis of M. pneumoniae infection. Further, LAT was compared with DNA-probe test (DP) which was the only commercially available test for the rapid detection of the organism. In LAT, both M. pneumoniae and M. genitalium give positive agglutination, but the titer of M. genitalium was significantly lower than that of M. pneumoniae. The detection limit of LAT was 2 x 10(5) CFU/ml and that of DP was 5 x 10(4) CFU/ml in vitro. It was considered that target molecules in LAT were accumulated in the pharyngeal portion of the patients, because of their long half-life at 37 C. However, ribosomal RNA which was target molecule in DP was destroyed at 37 C much sooner, and the accumulation could not be expected. Actually, positive rate in LAT was higher than that in DP among clinical specimens in which M. pneumoniae was detected by culture method. The procedure of LAT is much easier and more rapid than that of DP in which radioactive isotope is required. LAT could be the choice of test for rapid diagnosis of M. pneumoniae infection.

Application of an indirect immunofluorescence test for detection of Mycoplasma pneumoniae in respiratory exudates

We prepared polyclonal antibody specific to Mycoplasma pneumoniae and examined the conditions influencing the ability of an indirect immunofluorescence test to detect the specific antigen in respiratory exudates. The antibody did not cross-react with normal human serum or with respiratory exudates from 10 healthy persons. Cross-reactivity of the antibody with species of mycoplasmas other than M. genitalium was fully diminished when absorbed with horse serum and yeast extract, components of the culture medium. Though the absorbed antibody cross-reacted with M. genitalium, the titer was significantly lower than when tested against M. pneumoniae. Two types of antigen-specific fluorescence were observed in clinical specimens: one is large or small fluorescent granular aggregates found in mucus, and the other is fine fluorescent particles diffused on the entire surface of small epithelial cells. Throat smears from 49 patients with serologically confirmed M. pneumoniae infections were examined by our indirect immunofluorescence method. Positive results were obtained in 42 cases, many of which were positive before a rise in serum antibody titer could be demonstrated, indicating that the method is useful for a preliminary diagnosis at an early stage of the infection.

Diagnosis of Mycoplasma pneumoniae pneumonia: sensitivities and specificities of serology with lipid antigen and isolation of the organism on soy peptone medium for identification of infections

The sensitivities and specificities of isolation and serology for detection of Mycoplasma pneumoniae infections were determined for 3,546 pneumonia patients for whom both isolation and serological data were available. Soy peptone, fresh yeast extract, horse serum-supplemented agar, and diphasic medium were employed for isolation, and the lipid antigen of M. pneumoniae was used for serodiagnosis by complement fixation. The number of M. pneumoniae colonies most frequently detected was 200 to 600 per throat swab, with a range of less than or equal to 60 to greater than or equal to 2,000. The use of diphasic medium increased the number of isolates by 26% compared with direct isolation on agar plates. The organism was isolated from 360 of 525 patients who showed fourfold or greater antibody increases in their paired sera, resulting in a sensitivity of culture of 68%. When persons with titers of greater than or equal to 32 but no fourfold increase were used as the reference, the sensitivity of culture was 58%. The combined sensitivity of the culture method for persons with serological evidence of infection (fourfold increase and titer of greater than or equal to 32) was 64%. The specificity of the culture method was 97% for the 2,527 serologically negative persons. Fourfold antibody increases were found in 360 of 674 persons with isolates of the organism, resulting in a sensitivity of 53%. An additional 247 persons showed titers of greater than or equal to 32 (without a fourfold increase), resulting in a combined sensitivity of 90% for serology with the lipid antigen for the detection of antibodies in culture-positive persons. Fourfold antibody increases were found in 6% of culture-negative persons, resulting in a specificity of 94%. The quantitative culture results provide important base-line data for the development of rapid diagnostic tests for M. pneumoniae infection.

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.

Epidemic pneumonia in university students

Longitudinal surveillance of pneumonia in a university student health service was conducted from 1965-1971 and 1984-1987. Of 104 pneumonia cases documented by chest x-ray, only six were presumed to have bacterial etiology; the remaining 98 were characteristic of atypical pneumonia syndrome. Mycoplasma pneumoniae was the etiology in 51% of the pneumonias in the 1960s and 13% in 1984-1987. Pneumonia incidence was highest in the fall semester in seven of 11 years studied. Annual incidence followed a three- to four-year periodicity. Both of these observations mirror the epidemiology of M. pneumoniae in the world population. Symptoms of cough, headache, malaise, and absence of the physical finding of wheezing were seen more consistently in M. pneumoniae pneumonia than in other atypical pneumonias; other clinical features varied among epidemics. Rapid cold agglutinin tests were positive in 27% of our clinically diagnosed pneumonias and in 36% of those with documented mycoplasmal infections. This study appears to provide a basis for predicting future epidemics of atypical pneumonia in student populations.

Laboratory diagnosis of Mycoplasma pneumoniae infection. 1. Direct detection of antigen in respiratory exudates by enzyme immunoassay

Direct and indirect antigen capture enzyme immunoassays (Ag-EIA) have been developed for the detection of Mycoplasma pneumoniae in nasopharyngeal aspirates or sputum from respiratory infection. The sensitivity of the two Ag-EIA were similar, but the indirect method using polyclonal rabbit and guinea-pig antisera was more convenient. The Ag-EIA had a detection limit of 10(4-4.5) colony-forming units/ml of sample. It was specific for M. pneumoniae and gave a low level response with M. genitalium. There were no cross-reactions with 10 other species of mycoplasmas. Tests with a wide range of bacteria and chlamydia group antigen, representing agents sometimes found in the respiratory tract, were also negative. At the current level of development, the Ag-EIA detected about 90% of specimens that were also positive for culture; 43% of specimens from culture-negative--seropositive patients gave a positive result. The overall pattern of results indicated that while antigen detection is a quick and effective substitute for the slow culture method, serological examination for specific IgM antibody is also necessary to give a complete diagnostic coverage.