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

Ascending Reproductive Tract Infection in Pig-Tailed Macaques Inoculated with Mycoplasma genitalium

Mycoplasma genitalium is a sexually transmitted bacterial pathogen that causes urogenital disease in men and women. M. genitalium infections can persist for months to years and can ascend to the upper reproductive tract in women where it is associated with serious sequelae including pelvic inflammatory disease, tubal factor infertility, and preterm birth. An animal model is needed to understand immune evasion strategies that allow persistence, mechanisms of ascending infection, and factors associated with clearance. In earlier studies, we determined that pig-tailed macaques are susceptible to cervical infection; however, not all primates were successfully infected, persistence varied between animals, and ascension to the upper reproductive tract was not observed after 4 or 8 weeks of follow-up. Building on our previous findings, we refined our inoculation methods to increase infection rates, extended observation to 18 weeks, and comprehensively sampled the upper reproductive tract to detect ascending infection. With these improvements, we established infection in all (3/3) primates inoculated with M. genitalium and demonstrated lower tract persistence for 16 to 18 weeks. Ascension to the upper reproductive tract at endpoint was observed in two out of three primates. All three primates developed serum and local antibodies reacting primarily to the MgpB and MgpC adherence proteins. Elevated genital polymorphonuclear leukocytes (PMNs) and inflammatory cytokines and chemokines, erythema of the ectocervix in one primate, and histologic evidence of vaginitis and endocervicitis in two primates suggest a mild to moderate inflammatory response to infection. This model will be valuable to understand the natural history of M. genitalium infection including mechanisms of persistence, immune evasion, and ascension to the upper reproductive tract.

Etiology and the challenge of diagnostic testing of community-acquired pneumonia in children and adolescents

Background

Pneumonia is the leading cause of mortality in pediatric population. The etiology of pneumonia in this population is variable and changes according to age and disease severity and where the study is conducted. Our aim was to determine the etiology of community-acquired pneumonia (CAP) in children aged 1 month to 17 years admitted to 13 Colombian hospitals.

Methods

Prospective cohort study. Hospitalized children with radiologically confirmed CAP and ≤ 15 days of symptoms were included and followed together with a control group. Induced sputum (IS) was submitted for stains and cultures for pyogenic bacteria and Mycobacterium tuberculosis, and multiplex PCR (mPCR) for bacteria and viruses; urinary antigens for pneumococcus and Legionella pneumophila; nasopharyngeal swabs for viruses, and paired serology for atypical bacteria and viruses. Additional cultures were taken at the discretion of primary care pediatricians.

Results

Among 525 children with CAP, 71.6% had non-severe pneumonia; 24.8% severe and 3.6% very severe pneumonia, and no fatal cases. At least one microorganism was identified in 84% of children and 61% were of mixed etiology; 72% had at least one respiratory virus, 28% pyogenic bacteria and 21% atypical bacteria. Respiratory syncytial virus, Parainfluenza, Rhinovirus, Influenza, Mycoplasma pneumoniae, Adenovirus and Streptococcus pneumoniae were the most common etiologies of CAP. Respiratory syncytial virus was more frequent in children under 2 years and in severe pneumonia. Tuberculosis was diagnosed in 2.3% of children. IS was the most useful specimen to identify the etiology (33.6%), and blood cultures were positive in 3.6%. The concordance between all available diagnostic tests was low. A high percentage of healthy children were colonized by S. pneumoniae and Haemophilus influenzae, or were infected by Parainfluenza, Rhinovirus, Influenza and Adenovirus.

Conclusions

Respiratory viruses are the most frequent etiology of CAP in children and adolescents, in particular in those under 5 years. This study shows the challenges in making an etiologic diagnosis of CAP in pediatric population because of the poor concordance between tests and the high percentage of multiple microorganisms in healthy children. IS is useful for CAP diagnosis in pediatric population.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12887-022-03235-z.

Azithromycin and Doxycycline Resistance Profiles of U.S. Mycoplasma genitalium Strains and Their Association with Treatment Outcomes

Mycoplasma genitalium is a sexually transmitted bacterium associated with nongonococcal urethritis (NGU) in men and cervicitis, endometritis, and pelvic inflammatory disease in women. Effective treatment is challenging due to the inherent, and increasingly acquired, antibiotic resistance in this pathogen. In our treatment trial conducted from 2007 to 2011 in Seattle, WA, we demonstrated poor efficacy of azithromycin (AZM) and doxycycline (DOX) against M. genitalium among men with NGU. In the present study, we cultured M. genitalium from 74 of 80 (92.5%) PCR-positive men at enrollment (V-1) and defined the MICs of AZM (N = 56 isolates) of DOX (N = 62 isolates). Susceptibility to AZM was bimodal; MICs were >8 μg/ml (44.6%) and <0.004 μg/ml (55.4%) for these isolates. The association of MIC with treatment efficacy was determined for men initially treated with either AZM (N = 30) or DOX (N = 24). Men treated with AZM were more likely to experience microbiologic treatment failure (P < 0.001) if infected with isolates that had AZM MICs of >8 μg/ml (18/18 men) than those with isolates that had AZM MICs of <0.004 μg/ml (1/12 men). Clinical treatment failure also was more likely to occur (P = 0.002) with AZM MICs of >8 μg/ml (12/18 men) than with AZM MICs of <0.004 μg/ml (1/12 men). In contrast, DOX MICs ranged from <0.125 to 2 μg/ml and were not correlated with microbiologic (P = 0.71) or clinical treatment (P = 0.41) failure, demonstrating no relationship between DOX MICs and treatment efficacy. Given the rapid spread of AZM resistance and the emergence of quinolone resistance, the current second-line therapy, monitoring MICs and evaluating other potential treatments for M. genitalium will be critical.

Model-driven design allows growth of Mycoplasma pneumoniae on serum-free media

Mycoplasma pneumoniae is a slow-growing, human pathogen that causes atypical pneumonia. Because it lacks a cell wall, many antibiotics are ineffective. Due to its reduced genome and dearth of many biosynthetic pathways, this fastidious bacterium depends on rich, undefined medium for growth, which makes large-scale cultivation challenging and expensive. To understand factors limiting growth, we developed a genome-scale, constraint-based model of M. pneumoniae called iEG158_mpn to describe the metabolic potential of this bacterium. We have put special emphasis on cell membrane formation to identify key lipid components to maximize bacterial growth. We have used this knowledge to predict essential components validated with in vitro serum-free media able to sustain growth. Our findings also show that glycolysis and lipid metabolism are much less efficient under hypoxia; these findings suggest that factors other than metabolism and membrane formation alone affect the growth of M. pneumoniae. Altogether, our modelling approach allowed us to optimize medium composition, enabled growth in defined media and streamlined operational requirements, thereby providing the basis for stable, reproducible and less expensive production.

Comparison of serological methods with PCR-based methods for the diagnosis of community-acquired pneumonia caused by atypical bacteria

Background

The diagnosis of community-acquired pneumonia (CAP) caused by Legionella pneumophila, Mycoplasma pneumoniae, and Chlamydophila pneumoniae is traditionally based on cultures and serology, which have special requirements, are time-consuming, and offer delayed results that limit their clinical usefulness of these techniques. We sought to develop a multiplex PCR (mPCR) method to diagnosis these bacterial infections in CAP patients and to compare the diagnostic yields obtained from mPCR of nasopharyngeal aspirates (NPAs), nasopharyngeal swabs (NPSs), and induced sputum (IS) with those obtained with specifc PCR commercial kits, paired serology, and urinary antigen.

Results

A total of 225 persons were included. Of these, 10 patients showed serological evidence of L. pneumophila infection, 30 of M. pneumoniae, and 18 of C. pneumoniae; 20 individuals showed no CAP. The sensitivities were mPCR-NPS = 23.1 %, mPCR-IS = 57.1 %, Seeplex®-IS = 52.4 %, and Speed-oligo®-NPA/NPS = 11.1 %, and the specificities were mPCR-NPS = 97.1 %, mPCR-IS = 77.8 %, Seeplex®-IS = 92.6 %, and Speed-oligo®-NPA/NPS = 96.1 %. The concordance between tests was poor (kappa <0.4), except for the concordance between mPCR and the commercial kit in IS (0.67). In individuals with no evidence of CAP, positive reactions were observed in paired serology and in all PCRs.

Conclusions

All PCRs had good specificity but low sensitivity in nasopharyngeal samples. The sensitivity of mPCR and Seeplex® in IS was approximately 60 %; thus, better diagnostic techniques for these three bacteria are required.

Electronic supplementary material

The online version of this article (doi:10.1186/s12952-016-0047-y) contains supplementary material, which is available to authorized users.

Comparison of sputum and nasopharyngeal swab specimens for molecular diagnosis of Mycoplasma pneumoniae, Chlamydophila pneumoniae, and Legionella pneumophila

Background

Differentiation of atypical pathogens is important for community-acquired pneumonia (CAP). In this study, we compared sputum and nasopharyngeal swabs (NPS) for use in detection of Mycoplasma pneumoniae (MP), Chlamydophila pneumoniae (CP), and Legionella pneumophila (LP), using Seeplex PneumoBacter ACE Detection Assay (PneumoBacter; Seegene).

Methods

Sputum and NPS specimens were collected from patients in 15 hospitals. DNA was extracted from sputum using QIAamp DNA Stool Mini Kit (Qiagen) and from NPS using easyMAG (bioMérieux). Both types of specimens were evaluated by multiplex PCR using PneumoBacter. To determine the diagnostic performance of this assay, sputum samples were also tested using BD ProbeTec ET Atypical Pneumonia Assay (APA; Becton Dickinson).

Results

Among 217 sputum and NPS, 20 (9.2%), 2 (0.9%), and 0 sputum were positive for MP, LP, and CP, respectively, whereas 8 (3.7%) NPS were positive for MP. The sputum APA test yielded 186, 206, and 204 interpretable results for MP, LP, and CP, respectively. Of these, 21 (11.3%) were positive for MP, 2 (1.0%) were positive for LP, and 0 samples were positive for CP. Compared to APA, the sensitivity and specificity of the sputum assay for MP were 95.2% and 100.0%, respectively, whereas for the NPS assay, these were 38.1% and 93.9%. Sputum testing was more sensitive than NPS testing (P=0.002). For LP and CP diagnosis, PneumoBacter and APA tests agreed 100%.

Conclusions

Specimen type is crucial and sputum is preferred over NPS for simultaneous detection of MP, LP, and CP using multiplex PCR in CAP.

Mycoplasma pneumoniae: Innocent Bystander or a True Cause of Central Nervous System Disease?

The consistency with which Mycoplasma pneumoniae has been implicated as a cause of encephalitis, and the increased incidence of central nervous system (CNS) disease observed during M. pneumoniae respiratory outbreaks, support the role of M. pneumoniae as a CNS pathogen. Three pathophysiologic mechanisms have been proposed: direct infection, autoimmunity, and vascular occlusion. Recent evidence demonstrating the organism's ability to survive intracellularly, presence of its DNA in the serum of individuals with acute encephalitis, case reports in which the organism is detected in brain parenchyma or cerebrospinal fluid (CSF), and animal data demonstrating CNS invasion by several Mycoplasma species support the contention that M. pneumoniae is capable of direct infection of the CNS. Because of limitations of current serologic assays and difficulty in interpreting the significance of positive polymerase chain reaction results in regard to acuity of infection and viability of the organism, the diagnosis of M. pneumoniae-associated CNS disease should be based on a combination of positive tests and exclusion of alternative diagnoses.

Microfluidic platform versus conventional real-time polymerase chain reaction for the detection of Mycoplasma pneumoniae in respiratory specimens

Rapid, accurate diagnosis of community-acquired pneumonia (CAP) due to Mycoplasma pneumoniae is compromised by low sensitivity of culture and serology. Polymerase chain reaction (PCR) has emerged as a sensitive method to detect M. pneumoniae DNA in clinical specimens. However, conventional real-time PCR is not cost-effective for routine or outpatient implementation. Here, we evaluate a novel microfluidic real-time PCR platform (Advanced Liquid Logic, Research Triangle Park, NC) that is rapid, portable, and fully automated. We enrolled patients with CAP and extracted DNA from nasopharyngeal wash (NPW) specimens using a biotinylated capture probe and streptavidin-coupled magnetic beads. Each extract was tested for M. pneumoniae-specific DNA by real-time PCR on both conventional and microfluidic platforms using Taqman probe and primers. Three of 59 (5.0%) NPWs were positive, and agreement between the methods was 98%. The microfluidic platform was equally sensitive but 3 times faster and offers an inexpensive and convenient diagnostic test for microbial DNA.

[Contribution of microbiological investigations to the diagnosis of lower respiratory tract infections]

The diagnosis of community-acquired pneumonia is usually based on clinical and radiological criteria. The identification of a causative organism is not required for the diagnosis. Although numerous microbiological techniques are available, their sensitivity and specificity are not high enough to guide first-line antimicrobial therapy. Consequently, this treatment remains most often empiric. If the causative organism is identified, the antimicrobial treatment is adapted. Sputum analysis may be proposed as a diagnostic tool for patients with an acute exacerbation of chronic obstructive pulmonary disease, in specific cases (prior antibiotherapy, hospitalization, failure of the empiric antimicrobial treatment).

Erythema multiforme due to Mycoplasma pneumoniae infection in two children

Mycoplasma pneumoniae is an important and highly relevant cause of bullous erythema multiforme, isolated mucositis, and Stevens-Johnson syndrome in children. In this article, we present two children with respiratory Mycoplasma pneumoniae infection and associated cutaneous findings within the spectrum of erythema multiforme. We review the literature associating these three entities with Mycoplasma pneumoniae infection and discuss controversies regarding the classification of erythema multiforme, as well as update reported infectious causes of the bullous form. Many understand the erythema multiforme spectrum to include bullous erythema multiforme, mucositis, and Stevens-Johnson syndrome in the order of increasing severity. We feel that this relationship should be reconsidered to help better understand the prognosis and outcomes. It is our opinion that bullous erythema multiforme is a separate, yet related condition that can occur in the context of Mycoplasma pneumoniae infection. With many similarities to mucositis and Stevens-Johnson syndrome, bullous erythema multiforme can be considered part of a spectrum of disease that includes Stevens-Johnson syndrome. Unlike mucositis and Stevens-Johnson syndrome, bullous erythema multiforme caused by Mycoplasma pneumoniae infection has low morbidity for the child. Mycoplasma pneumoniae-associated mucositis and Stevens-Johnson syndrome seem to occur along a spectrum with separate prognosis and potential pathogenesis compared with bullous erythema multiforme. Making the distinction between these conditions is valuable for predicting the child's prognosis. Patients who develop symptoms consistent with these conditions should be appropriately evaluated for Mycoplasma pneumoniae infection and closely monitored.

Detection of pulmonary Mycoplasma pneumoniae infections in HIV-infected subjects using culture and serology

OBJECTIVE

The true prevalence of Mycoplasma pneumoniae infections involving the respiratory tracts of HIV-infected individuals is still unclear. This study examined the prevalence of M. pneumoniae in 100 HIV-infected individuals at an AIDS care center in Chennai, India, using conventional laboratory techniques and interpretation criteria.

METHODS

Diagnosis was based on culture, cold agglutination test, and commercial enzyme-linked immunosorbent assay (ELISA) for the qualitative determination of IgM antibodies against M. pneumoniae. The efficacies of the different diagnostic procedures used in the study were analyzed.

RESULTS

The prevalence of M. pneumoniae was 31% by culture and 21% by IgM ELISA. Cough (p=0.03, OR 3.8, 95% CI 1-17.8), myalgia (p=0.04, OR 2.5, 95% CI 1-6.6), rales (p=0.04, OR 2.4, 95% CI 1-6.6), and cervical adenopathy (p=0.03, OR 2.7, 95% CI 1-7.1) were the symptoms that significantly corroborated culture positivity. Patients positive for M. pneumoniae by culture or IgM antibody had significantly greater CD4+ T-cell depletion and anemia than those without any evidence of infection.

CONCLUSIONS

This study provides the means to diagnose M. pneumoniae infection and information on the prevalence of the pathogen in HIV-infected individuals in resource constrained settings. Although modern molecular techniques may provide more insight into the prevalence of M. pneumoniae in HIV-infected individuals, conventional methods can still be used in diagnosis.

Seroprevalence of Mycoplasma pneumoniae in HIV-infected patients using a microparticle agglutination test

Mycoplasma pneumoniae is increasingly recognized as a common and important pathogen in community settings, and is responsible for various pulmonary and extrapulmonary conditions in the normal population. However, the seroepidemiology of acute M. pneumoniae infection in HIV-infected individuals is still unclear worldwide. This study examined the seroprevalence of antibodies to M. pneumoniae in HIV-infected patients admitted with respiratory complaints at a tertiary AIDS care centre in Chennai, India. A commercial gelatin microparticle agglutination test (Serodia-Myco II, Fujirebio) was used for the determination of antibodies against M. pneumoniae in acute serum specimens. Of the 200 HIV-infected patients with underlying pulmonary conditions tested, 34 (17 % positivity; 95 % CI 12-23 %) had antibodies specific to M. pneumoniae, while among the 40 patients with no underlying pulmonary symptoms, five (12.5 % positivity; 95 % CI 4-27 %) had evidence of anti-M. pneumoniae antibody. This shows that the incidence of M. pneumoniae seropositivity is greater in patients with underlying pulmonary complaints. Most positive titres were found in the age group 28-37 years in the symptomatic and symptom-free groups (64.7 and 60 %, respectively). The positive titres ranged from 40 to >20 480. High titres (> or =320) were found in 10 out of the 39 patients (25.6 %). This seroprevalence study reports a 16.2 % prevalence of M. pneumoniae infections in HIV-infected patients by a particle agglutination test.

Mycoplasma pneumoniae-associated myelitis: a comprehensive review

Myelitis is one of the most severe central nervous system complications seen in association with Mycoplasma pneumoniae infections and both acute transverse myelitis (ATM) as well as acute disseminated encephalomyelitis (ADEM) have been observed. We reviewed all available literature on cases of Mycoplasma spp. associated ATM as well as ADEM with dominant spinal cord pathology and classified those cases according to the strength of evidence implicating M. pneumoniae as the cause. A wide range of data on diagnosis, epidemiology, immunopathogenesis, clinical picture, laboratory diagnosis, neuroimaging and treatment for this rare entity is presented. The use of highly sensitive and specific molecular diagnostic techniques may assist in clearly elucidating the role of M. pneumoniae in ATM/ADEM syndromes in the near future. Immunomodulating therapies may have a role in treating such cases.

Serosurveillance of acute Mycoplasma pneumoniae infection among HIV infected patients with pulmonary complaints in Chennai, Southern India

BACKGROUND

The true seroepidemiology of acute Mycoplasma pneumoniae infection in HIV infected individuals is ambiguous.

METHODS

This study examined the serosurveillance of IgM antibodies to M. pneumoniae in HIV infected patients presenting with pulmonary symptoms at a tertiary AIDS care center in Chennai, Southern India, using cold-haemagglutination test and commercial enzyme linked immunosorbent assay in acute serum specimens.

RESULTS

One hundred HIV infected patients had enrolled in the study; 21 (21%) were positive for M. pneumoniae IgM antibodies by ELISA and 34 (34%) showed evidence of cold hemagglutinins.

CONCLUSION

This serosurveillance study reports a 21% prevalence of M. pneumoniae IgM antibody among HIV infected patients with pulmonary symptoms by ELISA and non-specific diagnosis was confirmed in 34% of the cases screened. Determination of cold agglutination titer could be used as a substitute to other expensive procedures in limited resource settings and third-world nations to diagnose M. pneumoniae infections for prompt initiation of therapy, as CAT has been found to be 100% sensitive and 84% specific in the diagnosis of M. pneumoniae infection.

Swedish guidelines for the management of community-acquired pneumonia in immunocompetent adults

This document presents the evidence-based guidelines of the Swedish Society of Infectious Diseases for the management of adult immunocompetent patients with community-acquired pneumonia (CAP), who are assessed at hospital. The prognostic score 'CURB-65' is recommended for all CAP patients in the emergency room. The score provides an assessment tool for the decision regarding outpatient treatment or level of hospital supervision, the choice of microbiological investigations, and empirical antibiotic treatment. In patients with non-severe CAP (CURB-65 score 0-2) we recommend initial narrow-spectrum antibiotic treatment, orally or intravenously, primarily directed at Streptococcus pneumoniae. In those with CURB-65 score 3, penicillin G or a cephalosporin intravenously is recommended. For CURB-65 score 0-3 atypical pathogens should be covered only when they are suspected on clinical or epidemiological grounds. In patients with CURB-65 score 4-5 intravenous combination therapy with either cephalosporin/macrolide or penicillin G/fluoroquinolone is recommended. Efforts should be made to identify the CAP aetiology in order to support the ongoing antibiotic treatment or to suggest treatment alterations. Recommended measures for prevention of CAP include influenza -- and pneumococcal -- vaccination to risk groups and efforts for smoking cessation.

Sample type is crucial to the diagnosis of Mycoplasma pneumoniae pneumonia by PCR

Sensitive and specific methods for rapid laboratory diagnosis of Mycoplasma pneumoniae were not available until nucleic acid amplification methods were developed. The choice of sample type and method of sampling are crucial to optimal diagnostic efficacy. Three types of respiratory samples from 32 young military conscripts with pneumonia were collected during an outbreak of M. pneumoniae infection. Sputum, nasopharyngeal aspirate and throat swab specimens were tested by 16S rRNA gene-based PCR with liquid-phase probe hybridization, and the results were compared with serology. The PCR result was positive for 22 (69 %) of the sputa, 16 (50 %) of the aspirates and 12 (37.5 %) of the swabs. Serology with increasing or high titres supported the positive findings in all instances. Sputum, when available, is clearly the best sample type for young adults with pneumonia.

Mycoplasma pneumoniae and its role as a human pathogen

Mycoplasma pneumoniae is a unique bacterium that does not always receive the attention it merits considering the number of illnesses it causes and the degree of morbidity associated with it in both children and adults. Serious infections requiring hospitalization, while rare, occur in both adults and children and may involve multiple organ systems. The severity of disease appears to be related to the degree to which the host immune response reacts to the infection. Extrapulmonary complications involving all of the major organ systems can occur in association with M. pneumoniae infection as a result of direct invasion and/or autoimmune response. The extrapulmonary manifestations are sometimes of greater severity and clinical importance than the primary respiratory infection. Evidence for this organism's contributory role in chronic lung conditions such as asthma is accumulating. Effective management of M. pneumoniae infections can usually be achieved with macrolides, tetracyclines, or fluoroquinolones. As more is learned about the pathogenesis and immune response elicited by M. pneumoniae, improvement in methods for diagnosis and prevention of disease due to this organism may occur.

Detection of Mycoplasma pneumoniae in respiratory samples by real-time PCR using an inhibition control

Polymerase chain reaction (PCR) with real-time detection using two adjacent fluorescent probes in a Lightcycler instrument was applied for detection of the Mycoplasma pneumoniae P1 protein gene. To monitor inhibition in each sample an internal control was constructed that can be amplified by the same primers but detected by different probes and dual color detection. The real-time PCR was applied on 115 respiratory samples from 82 patients and compared to a conventional PCR. There was 100% agreement between the assays, but the real-time PCR proved to be highly superior in speed with a much lower risk of false positives by laboratory contamination.

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.

Mycoplasma pneumoniae ecephalitis

Mycoplasma pneumoniae causes between 5 and 10 percent of acute childhood encephalitis in Europe and North America. Encephalitis due to this organism may be caused by direct infection of the brain, immune-mediated brain injury or thromboembolic phenomenon. The prognosis is guarded with 20 to 60 percent suffering neurologic sequelae. The diagnosis of M. pneumoniae encephalitis should be based on strong evidence of M. pneumoniae infection that includes detection of the organism in culture or using molecular detection techniques in addition to serology and exclusion of other potential etiologies. Antibiotic therapy should be considered for all children with suspected M. pneumoniae encephalitis; antibiotics with good central nervous system (CNS) penetration such as ciprofloxacin, doxycycline, chloramphenicol or azithromycin are appropriate under most circumstances. Immune modulating therapies, such as corticosteroids, intravenous immune globulin or plasmapharesis, should be considered in those with immune-mediated syndromes such as acute disseminated encephalomyelitis.

Polymerase chain reaction as a sensitive and rapid method for specific detection of Mycoplasma pneumoniae in clinical samples

The fast diagnosis of Mycoplasma primary atypical pneumonia is impaired by the lack of routinely available culture methods for isolation of Mycoplasma pneumoniae from clinical specimens. Likewise, serological methods commonly used for diagnosis are insensitive and non-specific. In this study, we have established and applied the polymerase chain reaction (PCR) technique to detect M. pneumoniae DNA in clinical samples originating from the respiratory tract. The PCR results were compared with those from culture and serology tests. To standardize the detection of M. pneumoniae by PCR, we first used DNA from culture grown organisms and clinical samples seeded with M. pneumoniae. PCR amplification was performed with M. pneumoniae-specific primers to amplify 144, 153 and 631 bp DNA fragments by using primer pairs MP5-1/MP5-2, P1-178/P1-331 and P1-178/P1-809, respectively. The amplification of the 631 bp DNA fragment was found to be most sensitive for the detection of M. pneumoniae. Using the most sensitive PCR, a total of 47 respiratory specimens from patients suspected of community acquired pneumonia were tested. While none of the specimens were positive for M. pneumoniae in culture, 6 specimens gave positive results by PCR. In 4 out of the 5 PCR positive samples tested serologically, the results were supported by elevated levels of anti-mycoplasma IgG/IgM/IgA. Thus, these results suggest that PCR is the most sensitive method to detect M. pneumoniae in clinical specimens.

Evaluation of Chlamydia pneumoniae and Mycoplasma pneumoniae as etiologic agents of persistent cough in adolescents and adults

Chlamydia pneumoniae and Mycoplasma pneumoniae were evaluated as agents of persistent cough in adolescents and adults (n = 491). Tests of 473 respiratory specimens by culture or PCR or both identified four episodes (0.8%) of M. pneumoniae-associated illness and no episodes of C. pneumoniae illness, suggesting that these bacteria do not frequently cause persistent cough.

Infectious etiologies in acute exacerbation of COPD

Acute exacerbation (AE) is a frequent episode during the prolonged chronic course of chronic obstructive pulmonary disease (COPD), which entails significant morbidity and mortality. The purpose of this study was to determine the frequency distribution of infectious etiologies in these episodes. Two hundred forty hospitalizations for AECOPD were included in a prospective, purely serologically based study. Paired sera were obtained for each of the hospitalizations and were tested using immunofluorescence or EIA methods to identify 13 different pathogens. Only significant changes in antibody titers were considered diagnostic. The mean age ( +/- SD) of the patients was 66.8 +/- 9.0 years and 179 (84%) were males. In 175 (72.9%) hospitalizations at least one infectious etiology was identified. In 117 (48.8%) hospitalizations at least one of 7 viral etiologies was identified. In 72 (30.0%) hospitalizations at least one of the following atypical bacteria was identified: Legionella spp. in 40 (16.7%), Mycoplasma pneumoniae in 34 (14.2%), and Coxiella burnetii in a single hospitalization. In 58 (24.2%) hospitalizations at least one classic bacterial etiology was found: Streptococcus pneumoniae in 48 (20.0%), Hemophilus influenzae in 10 (4.2%) and Moraxella catarrhalis in 9 (3.8%). More than one etiology was found in 72 (30.0%) hospitalizations. There were no significant differences in the etiologic distribution when the patients were classified by severity of airway obstruction or the clinical type of the exacerbation. We conclude that in most cases of hospitalization due to AECOPD the infectious etiology is viral or atypical bacteria and is classic bacteria in only a minority of cases. More than one etiologic cause can be identified in a third of the cases. The frequency distribution of the etiologies is not associated with the severity of airway obstruction or the clinical type of the exacerbation. The results of our study suggest that atypical bacteria should be covered in antibiotic regimens recommended for AECOPD. This issue should be addressed in future studies.

Acute Childhood Encephalitis andMycoplasma pneumoniae

In a prospective 5-year study of children with acute encephalitis, evidence of Mycoplasma pneumoniae infection was demonstrated in 50 (31%) of 159 children. In 11 (6.9%) of these patients, M. pneumoniae was determined to be the probable cause of encephalitis on the basis of its detection in cerebrospinal fluid (CSF) by polymerase chain reaction (PCR) or by positive results of serologic tests for M. pneumoniae and detection of the organism in the throat by PCR. CSF PCR positivity correlated with a shorter prodromal illness (P=.015) and lack of respiratory symptoms (P=.06). Long-term neurologic sequelae occurred in 64% of probable cases. Thirty children (18.9%) who were seropositive for M. pneumoniae but did not have the organism detected by culture or PCR had convincing evidence implicating other organisms as the cause of encephalitis, suggesting that current serologic assays for M. pneumoniae are not sufficiently specific to establish a diagnosis of M. pneumoniae encephalitis.

Effect of a Mycoplasma hominis-like Mycoplasma on the infection of HEp-2 cells by the TW-183 strain of Chlamydia pneumoniae

We isolated a Mycoplasma hominis-like mycoplasma from a stock culture of Chlamydia pneumoniae TW-183 obtained from the American Type Culture Collection and eradicated the contaminant by treating the stock suspension with a nonionic detergent, Igepal CA-630. The M. hominis-like mycoplasma neither inhibits nor enhances the infectivity of C. pneumoniae for HEp-2 cells.

Rhabdomyolysis associated with infection by Mycoplasma pneumoniae: a case report

BACKGROUND

Mycoplasma pneumoniae is responsible for approximately 20% of the cases of community-acquired pneumonia. The onset of respiratory symptoms is gradual and systemic complaints such as headache, malaise, arthalgias, and low-grade fever are frequently prominent. Extrapulmonary manifestations of M pneumoniae are common and hematologic (thrombocytopenia, splenomegaly, disseminated intravascular coagulation, hemolytic anemia), dermatologic (Stevens-Johnson syndrome), gastrointestinal (vomiting, diarrhea, pancreatitis), renal (interstitial nephritis, glomerulonephritis), cardiac (pericarditis, myocarditis, pericardial effusion) and central nervous system (meningitis, transverse myelitis, polyradiculopathy, cerebellar ataxia, sensorineural hearing loss) complications can occur.

OBSERVATION

We describe the case of an adolescent girl with massive rhabdomyolysis associated with an infection caused by M pneumoniae. We briefly review the differential diagnosis of a patient presenting with acute rhabdomyolysis and discuss the use of a new polymerase chain reaction-based assay for direct detection of M pneumoniae in throat swab specimens.

CONCLUSION

Clinicians should be aware of a possible association between rhabdomyolysis and infection with M pneumoniae and should consider testing for M pneumoniae when they are presented with a patient with idiopathic rhabdomyolysis. The new polymerase chain reaction-based assay for detection of M pneumoniae is a more accurate and more efficient method than traditional culture.

Atypical pathogens in community-acquired pneumonia

The atypical pathogens are an important and significant cause of CAP. The clinical and radiologic manifestations of CAP caused by these pathogens are modulated by the immunologic and physiologic status of the host, and therefore are not pathogen-specific. The range of frequencies found in various studies for the atypical pathogens among the causes of CAP is broad. These frequencies are affected by very important factors that should be recognized. In a significant percentage of patients, an atypical pathogen can be identified together with an additional cause. The significance of multiple causes has not been clarified sufficiently. The principal diagnostic techniques in use today for the causative diagnosis of CAP are serologic tests. Different serologic methods have been used in various studies and diagnostic criteria are not standardized. In the future it is likely that diagnostic testing will be based on the PCR technique on serum samples. The effectiveness and importance of antimicrobial therapy in some patients with atypical pathogen CAP are unclear. The accepted therapy today for atypical pathogen CAP, which is based on erythromycin, will probably be changed in the near future in favor of the new generations of fluoroquinolone or the new macrolide preparations.

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.

Anti-smooth muscle antibody in clinical human and experimental animal Mycoplasma pneumoniae infection

Autoantibody formation is possibly integral to the development of non-respiratory manifestations of acute Mycoplasma pneumoniae infection. We sought to confirm the occurrence of smooth muscle antibodies (SMA) in humans with acute Myc. pneumoniae respiratory infection and furthermore to assess whether similar autoantibodies would develop in a hamster model of respiratory infection. Paired sera from 21 patients with acute infection were assayed for SMA by immunofluorescence on mouse kidney/stomach substrates. The frequency of SMA was then determined for 52 paediatric patients with acute Myc. pneumoniae infection and 16 controls, and for sera from a hamster model of infection. Five of 21 paired sera had an increment in SMA between acute and convalescent specimens. At a screening dilution of 1:40, 18/52 infected and 0/16 controls had positive sera (P = 0.003); positive specimens demonstrated IgG rather than IgM SMA. In the hamster model of Myc. pneumoniae respiratory infection, significant IgG SMA increases occurred in 7/19 infections but not in 11 controls (P = 0.02). Immunoblotting did not identify actin as the substrate for SMA. Smooth muscle antibody increases are found in a significant minority of Myc. pneumoniae-infected humans and hamsters. A role for SMA in the pathogenesis of Myc. pneumoniae infection remains to be defined.

Isotype-specific antibody responses to acute Mycoplasma pneumoniae infection

BACKGROUND

Mycoplasma pneumoniae-induced respiratory infections affect millions of patients and have been implicated in exacerbation of bronchial asthma. IgE may be involved in such exacerbations. While specific IgG and IgM responses to Mycoplasma pneumoniae are well described, the response of other isotypes is less known.

PURPOSE

To determine whether specific IgE and what subclasses of IgG are formed in response to Mycoplasma pneumoniae infection.

METHODS

We studied 20 patients with acute Mycoplasma pneumoniae infection, in whom the diagnosis was confirmed by a 16-fold increase in complement fixation titer between acute and convalescent serum samples. We developed an enzyme-linked immunosorbent assay (ELISA) for the determination of IgG, IgA, and IgM antibodies specific for Mycoplasma pneumoniae protein antigens. We used Western blotting to confirm the results of the ELISA and to detect Mycoplasma-specific IgG subclasses and IgE.

RESULTS

Changes in Mycoplasma pneumoniae-specific IgG, IgA, and IgM were significant. Western blots of Mycoplasma pneumoniae antigens in 13 convalescent sera showed specific IgG in all, IgM in 11, IgA in 6, and IgE in 10. The IgG response consisted mainly of IgG1 and IgG3, and to a lesser degree of IgG2 and IgG4.

CONCLUSIONS

We conclude that Mycoplasma pneumoniae infection is associated with a significant specific IgA and IgE response, in addition to the well-known responses of IgG and IgM. As IgE is involved in allergic reactions, the production of Mycoplasma pneumoniae-specific IgE may have a role in exacerbation of bronchial asthma.

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.

Isolation of Mycoplasma genitalium strains from the male urethra

Mycoplasma genitalium is a human mycoplasma species which, on the basis of detection by PCR, has been incriminated as a cause of nongonococcal urethritis. Previously, only two strains from the urogenital tract and five strains from extragenital sites have been isolated. We have developed a method for the isolation of this fastidious microbe. M. genitalium from PCR-positive urethral specimens was initially propagated in Vero cell cultures grown in serum-free medium supplemented with Ultroser HY serum substitute. Growth was monitored by PCR. The M. genitalium strains grown in cell cultures could subsequently be subcultured in modified Friis's FF broth medium. Several passages in broth medium were required before growth on agar medium was attained. A total of 11 urethral specimens positive for M. genitalium by PCR from male patients with urethritis were investigated. Six strains were adapted to growth in broth medium, and four of these strains were cloned. Three specimens were overgrown by other mycoplasmas during propagation in the cell cultures. In only two PCR-positive specimens was propagation of M. genitalium unsuccessful. The use of cell culture combined with PCR monitoring of mycoplasmal growth may prove to be more widely applicable for the isolation of other fastidious mollicutes.

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.

Comparison of two rapid commercial tests with complement fixation for serologic diagnosis of Mycoplasma pneumoniae infections

The complement fixation (CF) test is the current reference serologic test for the diagnosis of Mycoplasma pneumoniae infection. However, it is reported to be insensitive and nonspecific, and it is labor intensive. To determine if a faster and more sensitive diagnosis of M. pneumoniae could be obtained, we examined 50 paired serum samples from patients with suspected M. pneumoniae infection by the CF test and two commercial rapid antibody detection kits, the Remel M. pneumoniae immunoglobulin G (IgG)-IgM antibody test system (Remel, Lenexa, Kans.) and the Seradyn Color Vue M. pneumoniae IgG-IgM kit (Seradyn, Indianapolis, Ind.). The Remel test, a 5-min qualitative immunobinding assay, detected antibodies in three patient serum samples with CF titers of 32 and in all but one sample with titers of > or = 64. The Seradyn test, a 40-min qualitative agglutination test, was less sensitive than CF or Remel. The Seradyn test was positive in 68% of cases, compared with 94 and 96% of cases tested by CF or Remel, respectively. Both commercial tests are faster and less technically demanding to perform than is the CF test.

Clinical utility of the polymerase chain reaction to diagnose Mycoplasma pneumoniae infection

The diagnosis of Mycoplasma pneumoniae infection currently relies on serological methods which may be slow to produce diagnostic results and may be inconvenient for both the clinician and the patient. This study was designed to assess whether or not the polymerase chain reaction (PCR) is a useful additional diagnostic method. Comparison was therefore made with serology as it is routinely practiced. PCR was used to examine for the presence of M. pneumoniae DNA in throat swab specimens obtained from 99 hospitalized patients investigated for a range of respiratory pathogens including M. pneumoniae. PCR detected M. pneumoniae DNA in 24 adults and 25 children, which is significantly more than the 32 patients found to be antibody positive by the particle agglutination test (p = 0.001). M. pneumoniae DNA was not detected in any of the throat swabs from 32 apparently healthy volunteers. PCR inhibitors were not detected in any of the samples tested. Significantly more children (88%) than adults (38%) were found to be anti-mycoplasma antibody-positive (p < 0.0001). Routine clinical practice was reflected in the fact that 56 patients (57%) had indeterminate serological results because only single sera were obtained. The sensitivity and specificity of PCR were assessed to be 92% and 98% respectively, using a combination of serological and clinical data as the benchmark. PCR appears to have advantages over serological testing, both with respect to accuracy and convenience of single specimen testing. The poor performance of serological tests in adults makes PCR especially useful in this age group.

Bronchoscopic diagnosis of pneumonia

Lower respiratory tract infections are characterized by significant morbidity and mortality but also by a relative inability to establish a specific etiologic agent on clinical grounds alone. With the recognized shortcomings of expectorated or aspirated secretions toward establishing an etiologic diagnosis, clinicians have increasingly used bronchoscopy to obtain diagnostic samples. A variety of specimen types may be obtained, including bronchial washes or brushes, protected specimen brushings, bronchoalveolar lavage, and transbronchial biopsies. Bronchoscopy has been applied in three primary clinical settings, including the immunocompromised host, especially human immunodeficiency virus-infected and organ transplant patients; ventilator-associated pneumonia; and severe, nonresolving community- or hospital-acquired pneumonia in nonventilated patients. In each clinical setting, and for each specimen type, specific laboratory protocols are required to provide maximal information. These protocols should provide for the use of a variety of rapid microscopic and quantitative culture techniques and the use of a variety of specific stains and selective culture to detect unusual organism groups.

Comparison of three serological methods for diagnosing Mycoplasma pneumoniae infection

AIMS

To compare the novel Serofast latex agglutination test (International Mycoplasma, Toulon-Cedex, France) with the complement fixation test and enzyme immunoassay (EIA) for diagnosing acute Mycoplasma pneumoniae infection.

METHODS

Paired sera from 60 patients with respiratory infection who had tested positive for M pneumoniae by complement fixation test were analysed with Serofast and indirect EIA for specific IgG and IgM antibodies.

RESULTS

Serofast was less sensitive than the two other tests. Only 30 (50%) out of 60 paired sera which showed a diagnostic seroconversion or had high positive, unchanged antibody titres by complement fixation test or EIA, or both, tested positive with Serofast. Positive test results with Serofast were associated with the presence of a complement fixation test titre of > or = 512 and high positive IgM antibody titres measurable by EIA; virtually all patients with a complement fixation test titre of < 256 or those responding primarily in the IgG class tested negative with Serofast. Based on analysis of sera taken at the acute phase of infection, 10 (17%) of the 60 patients tested positive by complement fixation test, 10 (17%) by EIA, and only four (7%) by Serofast.

CONCLUSIONS

Serofast was less sensitive than complement fixation test and EIA and it cannot be recommended as a replacement for either test in routine diagnostic use. It might prove useful in laboratories where non-specific tests, such as the determination of cold agglutinins, are still used for the diagnosis of M pneumoniae infection. Testing paired sera is, however, a prerequisite for obtaining acceptable sensitivity by Serofast as well as other serological methods currently available.

Detection of Mycoplasma pneumoniae by polymerase chain reaction and nonradioactive hybridization in microtiter plates

In order to improve the diagnosis of a Mycoplasma pneumoniae infection, we developed a polymerase chain reaction (PCR)-based assay. The gene encoding elongation factor Tu (tuf) was selected as the target sequence. Oligonucleotides derived from variable stretches of the tuf gene were able to prime the amplification of a 950-bp fragment exclusively when M. pneumoniae DNA was used as the template. The sensitivity of the assay was increased 10-fold when the amplification products were hybridized with an internal M. pneumoniae-specific oligonucleotide. The use of three to four genome copies for PCR was sufficient for obtaining a hybridization signal. In addition, we substituted radioactive filter hybridization with a microtiter plate assay. Via a biotin moiety of one PCR primer, the amplification products were immobilized on streptavidin-coated microtiter plates. Subsequent hybridization with a digoxigenin-labeled oligonucleotide resulted in the same sensitivity and specificity as those obtained by filter hybridization. Clinical application of the assay was performed on 102 throat swab specimens from patients with respiratory tract infections. Of 21 culture-positive samples, 19 were confirmed to be positive in the PCR-based assay (sensitivity, 90%). Furthermore, 14 of 19 seropositive but culture-negative samples gave a positive hybridization signal. Of 62 culture-negative and seronegative specimens, 60 gave a negative result in our assay (specificity, 97%). Of the 33 samples that were positive in our PCR-based assay, 5 samples initially gave false-negative results because of the presence of inhibitory substances in those specimens. Inhibition of Taq polymerase in these five cases was prevented by an additional step of phenol extraction and subsequent ethanol precipitation.

Comparison of the Seradyn Color Vue passive agglutination test and complement fixation for detection of Mycoplasma pneumoniae antibodies

We compared traditional complement fixation (CF) with a new passive agglutination method, the Seradyn Color Vue (SCV) test (Seradyn, Indianapolis, Ind.), for detection of Mycoplasma pneumoniae antibodies in 170 stored serum samples. The SCV test was 90% sensitive in identifying as positive 27 of 30 CF high-titer (> or = 1:64) serum samples and 100% specific in identifying as negative 134 of 134 CF low-titer (< or = 1:32) or negative (< 1:8) serum samples. The SCV test was technically undemanding, and it required no expensive equipment.

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.