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Background: Mycoplasma pneumoniae ( M. pneumoniae ) is implicated in several immune-mediated extrapulmonary manifestations, including reactive arthritis. Recently, increased total serum IgE were reported in children developing M. pneumoniae -related extrapulmonary diseases (MpEPDs). Here, we aimed at analyzing these aspects in children affected with rheumatic disorders and, in detail, Juvenile Idiopathic Arthritis (JIA)., Methods: M. pneumoniae serology (IgG and IgM) and total serum IgE were concomitantly analyzed in 139 pediatric patients diagnosed with: JIA (Group 1, n = 85), or any rheumatic disease other than JIA (Group 2, n = 27), or non-inflammatory endocrinological disorders (Group 3, n = 27)., Results: Overall, 19.4% M. pneumoniae seroprevalence was observed in this hospitalized pediatric population, without signicant differences among the three groups. No significant differences in total serum IgE levels were noted among these groups; however, a second analysis excluding children with very high (and clearly abnormal) IgE levels suggested that JIA patients and, in detail, those with oligopolyarticular forms may have higher serum IgE concentrations. This relative difference among groups in serum IgE level seems to be more pronounced in M. pneumoniae seropositive children., Conclusions: M. pneumoniae infection should be actively sought in children developing immune-mediated diseases, including patients affected with JIA and, especially, in oligopolyarticular forms. There is some evidence that total serum IgE levels may tend to be increased in patients with oligopolyarticular JIA subtype and especially in those resulting as M. pneumoniae seropositive. However, further and focused research is needed to confirm these preliminary results and to clarify the relation between M. pneumoniae infection, atopic status, and immune-mediated arthritis., Competing Interests: The authors have no conflict of interest to declare., (Copyright © 2021 Dimitri Poddighe et al.)

Objective: Mycoplasma pneumoniae ( M. pneumoniae ), an extracellular pathogen lacking a cell wall, causes respiratory infection in adults and children and has been implicated in asthma exacerbation; immunoglobulin (Ig) E may be involved in these exacerbations. Specific IgM and IgG immune response to M. pneumoniae has been reported, but less is known about IgE M. pneumoniae antibody (Ab) responses in asthma. Previous studies in our laboratory demonstrated that asthmatic children have increased IgM M. pneumoniae levels, but not IgE. Thus, we sought to investigate whether past M. pneumoniae infection triggers production of M. pneumoniae -specific IgE Abs in adult subjects with/without asthma., Methods: M. pneumoniae - IgE and -IgM Ab responses were studied in adult asthmatic (N=22) and non-asthmatic (N=22) subjects (ELISA). Data are reported as antibody index. Threshold detection levels: IgE, IgM: 0.2, 0.9, respectively., Results: M. pneumoniae -IgE Ab levels were low and below the threshold of detection in both asthmatic and non-asthmatics (0.002 ± 0.008 vs. 0.02 ± 0.03; P =0.021). However, specific-IgM levels were slightly higher in non-asthmatics compared with asthmatics (0.96 ± 0.37 vs. 0.79 ± 0.31; P =0.054). M. pneumoniae -IgM Ab positivity was similar in both groups ( P =1.0)., Conclusion: IgM M. pneumoniae Abs may play an important role in non-asthma and persist for months after acute infection. IgE M. pneumoniae Abs may play a less important role in both groups., (© 2021 by the Association of Clinical Scientists, Inc.)

Introduction: Mycoplasma pneumoniae (Mypn) infection could be occurring at an earlier age due to social pheno mena such as attending daycare centers more frequently and earlier than decades ago., Objective: to estimate the prevalence of anti-Mypn antibodies in children aged 0-12 years, and to explore whether age, attendance to daycare center/school, overcrowding or the presence of children aged below 12 years in the households increase the risk of seropositivity., Patients and Method: Cross-sectional stu dy including healthy children aged 0-12 years which required blood draws for routine laboratory tests. In all cases, the aforementioned variables were recorded and anti-Mypn IgG was determined by enzyme immunoassay. The association between predictors and seropositivity was assessed in a logistic regression model., Results: We included 232 patients (average age 56.4 ± 40.0 months). 56.9% attended a daycare center/school, 63.8% co-habited with children under 12 years old, and 15.9% lived in overcrowded households. The prevalence of anti-Mypn antibodies was 14.6%. There were no significant differences between seropositive and seronegative children regarding age (63.1 ± 40.7 vs. 55.4 ± 41.3 months), school/day-care attendance (64.7% vs. 55.5%), overcrowding (14.7% vs. 14.9%), or co-habiting with children (64.7% vs. 63.6%). Age was not an independent predictor of seropositivity in the multivariate model., Conclusion: The prevalence of anti-Mypn antibodies in children was 14.6% and age was not a predictor of seropositivity.

Background: Extensive studies have focused on the diagnosis and treatment of Mycoplasma pneumoniae infection; however, rare studies investigated the posttreatment conditions. We analyzed the carrying status of M. pneumoniae in the respiratory tract of children before and after treatment., Methods: Ninety-two children with M. pneumoniae pneumonia were included in this study. Clinical data were obtained from each patient, and pharyngeal swab sampling was performed at preliminary diagnosis and discharge. Real-time PCR and dilution quantitative culture were utilized to determine the DNA quantification and number of viable M. pneumoniae from samples collected upon preliminary diagnosis and discharge., Results: All the 92 cases showed DNA positivity upon preliminary diagnosis, serum IgM antibody was detected in 80 patients, and positivity of M. pneumoniae culture was observed in 82 cases. Upon discharge, the M. pneumoniae nucleotide and culture positivity were detected in 87 and 49 cases, respectively. The content of viable M. pneumoniae was 10-10 4  CCU/mL and 10-10 2  CCU/mL in the preliminary diagnosis samples and discharge samples, respectively., Conclusions: Real-time PCR was rapid and effective for the qualitative diagnosis of M. pneumoniae at the early stage, but it cannot be used to evaluate the prognosis of patients with M. pneumoniae infection. Quantitative analysis for M. pneumoniae DNA could not directly reflex the viable strain content., Competing Interests: The authors declare that there are no conflicts of interest regarding the publication of this paper., (Copyright © 2020 Fei Zhao et al.)

Objective: We aimed to assess the prevalence of Chlamydophila pneumoniae and Mycoplasma pneumoniae acute infections, using serological testing, in patients admitted to the emergency department for acute exacerbations of chronic obstructive pulmonary disease (COPD)., Methods: We performed a prospective observational study of 100 consecutive patients. Serum specimens were collected at day 0 and day 15. C. pneumoniae and M. pneumoniae antibodies (IgM and IgG) were tested by commercial ELISA and immunofluorescence assay, respectively., Results: We did not observe any acute M. pneumoniae infection; however, 11 patients (11%) showed a profile compatible with a recent C. pneumoniae infection (nine patients with specific IgM and two with an IgG antibody rise). Demographic and clinical parameters did not differ between patients with and without biological profile of recent C. pneumoniae infection., Conclusion: C. pneumoniae is a pathogen that requires specific antimicrobial treatment. Its detection must always be performed considering its prevalence in patients presenting with acute COPD exacerbations., (Copyright © 2016 Elsevier Masson SAS. All rights reserved.)

There have been some limitations on early diagnosis of Mycoplasma pneumoniae (MP) infection because of no immunoglobulin M (IgM) responses and variable detection rates of polymerase chain reaction in the early stage of the disease. We wanted to discuss regarding early diagnostic method using short-term paired titration of MP-specific IgM and cold agglutinins (CAs) in the early stage of MP pneumonia.The participants of this study were 418 children with MP pneumonia during 2 recent epidemics (2006-2007 and 2011), and they were diagnosed by an anti-MP IgM antibody test (Serodia Myco II) examined twice during hospitalization at presentation and around discharge (mean of 3.4 ± 1.3 days apart). CA titers were simultaneously examined twice during study period. Anti-MP IgM antibody titer ≥1:40 and CA titer ≥1:4 were considered positive, respectively. The relationships between 2 IgM antibodies in the early stage were evaluated.Regarding MP-specific antibody titers, 148 patients showed a seroconversion, 245 patients exhibited increased titers, and 25 patients had unchanged higher titers (≥1:640) during hospitalization. The median MP-specific antibody titers at each examination time were 1:80 and 1:640, respectively; those of CAs were 1:8 and 1:32, respectively. Illness duration prior to admission showed a trend of association with both titers, and patients with shorter illness duration had a higher rate of negative titers or lower titers at each examination time. CAs and MP-specific antibody titers were correlated in the total patients at presentation and at 2nd examination (P < 0.001, respectively), and the diagnostic corresponding rates of CAs to IgM antibody test were 81% to 96% in patient subgroups.Short-term paired MP specific-IgM determinations in the acute stage may be used as a definitive diagnostic method for MP pneumonia. Paired CA titers showed a correlation with MP-specific antibody titers, suggesting they can be used as an adjuvant diagnostic method.

Early diagnosis of Mycoplasma pneumoniae (MP) infection is crucial for prompt treatment and good patient outcome. However, serological tests to detect MP rapidly and conveniently are still lacking. This study aimed to use the fluorescent dye Alexa Fluor® 647 as the detection marker to develop a lateral flow immunochromatographic assay (LFIA) for detection of MP-specific IgM in serum specimen. Monoclonal mouse antibody against human IgM (μ-chain specific) and goat anti-rabbit IgG were labeled with Alexa Fluor® 647 (anti-IgM-AF647 and anti-IgG-AF647). A mixture of natural MP antigen and recombinant P1 antigen was coated as the test line (T line) and rabbit IgG was coated as the control line (C line) on a nitrocellulose (NC) membrane. The MP antigens captured IgM-anti-IgM-AF647 complex on the T line. Rabbit IgG captured anti-IgG-AF647 on the C line. The fluorescence intensity on the T line and C line was measured. Sartorius CN140 NC membrane showed higher sensitivity than CN95. The optimal reaction time for the LFIA was 10min. The area under the receiver operating characteristic curve based on 34 MP positive and 166 MP negative serum samples was 0.986 (p<0.001). The cutoff value of T/C area ratio was 0.3830. The LFIA strips did not react with serum from patients infected with non-MP pathogens including influenza viruses and bacteria causing respiratory tract infection. The intra-assay and inter-assay coefficients of variation were between 3.28% and 10.14%. The shelf life was calculated to be 2years at room temperature. The LFIA strips and the commercial EUROIMMUN kit showed consistent results on 372 serum specimens. The overall consistency rate was 96.37% with a Kappa value of 0.842 (p<0.001). The LFIA in the current study may be a sensitive and specific approach to detect early MP infection rapidly and conveniently., (Copyright © 2016 Elsevier B.V. All rights reserved.)

Objective: To measure Mycoplasma pneumoniae pneumonia (MPP)-associated myocardial damage in different age groups of children with pneumonia., Methods: Children aged 0-14 years with pneumonia and myocardial damage (serum creatine kinase isoenzyme-MB [CK-MB] concentration >25 U/l) were enrolled in the study. The children were classified as Mycoplasma pneumoniae immunoglobulin M positive (M. pneumoniae IgM+) or negative (M. pneumoniae IgM-) based on a serological test. Children were stratified into four age groups in order to analyse age-specific MPP-associated myocardial damage., Results: The incidence of fever was significantly higher in children who were M. pneumoniae IgM+ compared with M. pneumoniae IgM- children. The median serum CK-MB concentration was significantly higher in children who were M. pneumoniae IgM+ compared with those who were M. pneumoniae IgM-. Children who were M. pneumoniae IgM+ in the 13-36 months and 72 months-14 years age groups had significantly higher median serum CK-MB concentrations than those who were M. pneumoniae IgM- in the same age group., Conclusions: M. pneumoniae infection was associated with greater myocardial damage in children aged 13-36 months and 72 months-14 years. This suggests age-specific immune responses to M. pneumoniae.

In this study, the performance of 10 serological assays for the diagnosis of Mycoplasma pneumoniae infection was evaluated. A total of 145 sera from 120 patients were tested. They were obtained from patients who were serologically positive for M. pneumoniae infection as well as from patients who were infected with micro-organisms that may cause interstitial pneumonia. The following assays were utilized: SeroMP IgM and IgG, SeroMP recombinant IgM, IgA and IgG, Liaison M. pneumoniae IgM and IgG and M. pneumoniae IgM, IgA and IgG ELISA Medac. The SeroMP Recombinant and Liaison assays both showed low IgM specificity, and crossreactivity was mainly observed in groups of patients with acute cytomegalovirus and Epstein-Barr virus infections. For IgA, the Medac assay was less specific than the SeroMP Recombinant assay. Discrepancies between the four tests were observed in IgG analyses, and due to the lack of a gold standard, 22 results were removed prior to determining the sensitivity and specificity. Therefore, the overall performance of IgG assays may be overstated; nevertheless, the SeroMP assay demonstrated a lack of sensitivity. The seroprevalence of IgG appears to be very low, raising concerns regarding whether the serological techniques can detect IgG levels over time. Serology remains a biological tool of choice for diagnosing M. pneumoniae infection, but improvement and standardization of the assays are needed, particularly for the determination of IgG., (Copyright © 2013 Elsevier Inc. All rights reserved.)

Background: Diagnosis of community-acquired pneumonia (CAP) caused by Mycoplasma pneumoniae in adults and adolescents is hampered by a lack of rapid and standardized tests for detection., Methods: CAP patients from 12 teaching hospitals were prospectively and consecutively recruited. Basic and clinical information, throat swabs and paired sera were collected. Mycoplasma pneumoniae was detected by IgG and IgM antibody tests, fluorescence quantitative polymerase chain reaction (FQ-PCR) and culture. A comparative study of the diagnostic values of three methods, including sensitivity, specificity, positive and negative predictive values and positive likelihood ratio (PLR) was conducted. A fourfold or greater increase of IgG antibody titers of paired sera was set as the diagnostic "gold standard"., Results: One hundred and twenty-five CAP patients (52.8% males, median age 47 years, range 14-85) were enrolled. Twenty-seven (21.6%) patients were diagnosed with acute Mycoplasma pneumoniae infections by the "gold standard". Specificity values of all three methods were around 90%. An increasing trend of sensitivity, positive predictive value and PLR was found, with the lowest in IgM testing (7.4%, 28.6% and 1.45), intermediate in FQ-PCR (40.7%, 50% and 3.63), and highest in culture (55.6%, 75% and 10.9)., Conclusions: In the defined group of patients, there was a good agreement between positive rate of MP cultivation of throat swabs and acute M. pneumoniae infection (PLR of 10.9). Since the sensitivity is low in all of the evaluated methods, the logical approach would be to incorporate PCR, culture and serological tests for optimum diagnosis of acute Mycoplasma pneumoniae infections in adults and adolescents.

Sheep flocks from Hokkaido, Iwate and Aomori, three northern prefectures of Japan, were screened for antibodies to Mycoplasma ovipneumoniae and Mycoplasma agalactiae by ELISA. Sixty four animals out of 246 (26%) were seropositive to M. ovipneumoniae, with positive results obtained from all three prefectures. None of the sera tested were serologically positive to M. agalactiae.

Background: Mycoplasma pneumoniae (M. pneumoniae) is a major cause of respiratory tract infection. There is no specific and simple diagnosis test for the clinic treatment. In this study, we evaluated the effectiveness of a recently developed commercial rapid M. pneumoniae medium testing method., Methods: There were 132 patients with acute respiratory tract infection enrolled in this study. All of the patients' throat swabs were taken in the morning after admission and determined using the rapid identification culture test for M. pneumoniae. In addition the M. pneumoniae polymerase chain reaction (PCR) test and routine bacterial and fungal microorganism culture test were used to identify the organisms following culture. In addition, serum from each patient was tested for M. pneumoniae using the passive particle agglutination test., Results: The rapid identification culture procedure indicated that 41 patients were M. pneumoniae positive, only 6 patients were M. pneumoniae positive based on PCR, and all of the positive cultures had fungus contamination. There were only 26 of the 41 patients whose serum M. pneumoniae tested positive. Passive particle agglutination test shows 38.6% of the patients were M. pneumoniae positive (51 out of 132). Compared with the passive particle agglutination test, the specificity, sensitivity of rapid M. pneumoniae identification culture method are 81.48% and 50.98%., Conclusions: The rapid identification of M. pneumoniae culture test is easy to perform and provides results fast, but has poor concordance with the M. pneumoniae PCR and serum M. pneumoniae antibody test due to the high fungus contamination. This commercial rapid M. pneumoniae medium method needs improvement for clinical use.

The simplified ImmunoCard Mycoplasma test for rapidly detecting Mycoplasma pneumoniae-specific IgM antibodies has been widely used. We examined the usefulness of this test for outpatient practices as well as for the association with bronchial asthma. Among 196 patients whose ImmunoCard showed positive, we targeted 57 cases in which we were able to perform this test multiple times. We evaluated the degree of inflammatory response in the laboratory findings at the time of the test, the period until negative seroconversion for antibodies, and the course of their pulmonary function findings. The number of days from the onset of pyrexia until the test was a median of 10 (range 2-70) days, wherein the inflammatory response did not have a significant effect on that number of days. In 35 cases in which we observed the seroconversion to negative for antibodies, the period of the positive phase was 180 (21-421) days, wherein it was significantly longer for smokers. We observed exacerbation in the majority of the asthma patients, and some of the non-asthmatic patients showed either asthma or asthma-like clinical conditions. For ImmunoCard-positive individuals, it is desirable to ascertain the history of respiratory infection retrospectively to about half a year, although this test is known to suffer from lack of both of sensitivity and specificity. Additionally, it is necessary for ImmunoCard-positive patients to pay attention to the exacerbation of asthma and the development of asthma thereafter.

Introduction: Although Mycoplasma pneumoniae is usually assumed as an infection mainly prevalent in school aged children and adolescents, there is evidence supporting that it may occur at younger ages. This could be related to social conditions, like crowding and day care center/school attendance more frequently and at younger ages than two decades ago. We estimated the prevalence of antibodies anti- Mycoplasma pneumoniae in children aged under 12 years. We also evaluated its association with age, day care center/school attendance, crowding or other children in the household., Population and Methods: This cross-sectional study included children aged under 12 years that required blood sampling for surgery. Those with acute infections, chronic diseases or known immunological disorders were excluded. In all cases predictors were recorded, and IgG anti-Mycoplasma pneumoniae determined by enzimoimmunoassay. Association between predictors and seropositivity was evaluated by logistic regression., Results: We included 355 children, aged 4.8 +/- 3.1 years. 57.6% attended to day care center/school, crowding was present in 27.3% and 70.1% had other children in the household. IgG antibodies anti-Mycoplasma pneumoniae were present in 12.4%. Seropositives were older than seronegatives (7.1 +/- 3.15 years vs. 4.4 +/- 3.06 years, p < 0.0001). After controlling by confounders, age remains as an independent predictor of seropositivity (OR: 1.19, CI 95%: 1.043-1.362)., Conclusions: Seroprevalence of Mycoplasma pneumoniae IgG antibodies in children aged under 12 years was 12.4%. Age is an independent predictor of seropositivity.

Background: The purpose of the present paper was to evaluate the clinical and chest radiographic features of pediatric patients with serologically proven Mycoplasma pneumoniae pneumonia (mycoplasma pneumonia)., Methods: The clinical records and chest radiographs of 39 consecutive patients (19 male, 20 female; age 3-13 years) with serologically positive IgG and IgM mycoplasma pneumonia were reviewed., Results: More than 90% of patients presented with fever and cough and 48% of patients had leukocyte count >10,000/mm(3). A C-reactive protein (CRP) level >0.375 mg/dL was noted in 28 patients (72%). Chest radiographs displayed four different patterns: (i) peribronchial and perivascular interstitial infiltrates (n= 19, 49%); (ii) airspace consolidations (n= 15, 38%); (iii) reticulonodular opacification (n= 3, 8%); and (iv) nodular or mass-like opacification (n= 2, 5%). Bilateral peribronchial perivascular interstitial infiltrations in central and middle lung zones were frequently seen (n= 19, 49%). Other radiological features were bilateral lesions in 51% of patients, pleural effusion in 23%, and hilar lymphadenopathy in 13%. Means of duration for treatment response and hospitalization were 2.5 and 5 days, respectively., Conclusion: There are various radiological features of mycoplasma pneumonia in children. Bilateral peribronchial and perivascular interstitial infiltrates were most frequently seen in the present patients.

With a rise in the incidence of allergic diseases and in the number of studies into the mechanisms of their occurrence, M. pneumoniae undoubtedly attracts a particular attention as a microorganism whose infection is able to simultaneously cause Th1 and Th2 types of immunological reactions. A serological survey of the patients of an allergology center could detect immunoglobulins M and G to M. pneumonia antigens.

The aim of study was to describe Mycoplasma pneumoniae epidemics in a hospital-based population. Special attention was paid to the relationship between antibody titer to M. pneumoniae and sex, age, and atopy. During the eight 6-month periods between January 2000 and December 2003, serum samples were obtained from 1,319 Korean children who presented with respiratory symptoms, and were examined for antibodies to M. pneumoniae using the indirect particle agglutination test. Geometric mean antibody titers peaked in the second half of 2000 and then decreased gradually, a second peak occurred in the second half of 2003. Likewise, the frequency of high antibody titers (> or =1:640) also peaked during these two periods. Antibody titers in children aged 0-3 yr were lower than in older children during both peak periods and for 2 yr after the first peak. Sex and atopy had no effect on antibody titers. During the years 2000-2003, geometric mean antibody titers and the frequencies of high antibody titers varied with time. These changes suggest a cyclic pattern of M. pneumoniae infection, with two epidemic peaks separated by 3 yr.

The Meridian ImmunoCard (IC), GenBio ImmunoWELL-IgM, and Remel EIA commercial antibody tests are qualitative enzyme immunoassays that detect antibodies to Mycoplasma pneumoniae in serum. These tests were compared to an M. pneumoniae complement fixation (CF) assay, which uses a commercially available antigen component. The Meridian IC and the ImmunoWELL-IgM detect immunoglobulin M (IgM) only; the Remel EIA and the CF test detect both IgM and IgG antibodies. Detection of specific IgM antibody, which appears early in infection, can be, but is not always, indicative of a recent or current infection. Paired serum samples from 64 adult patients with probable M. pneumoniae infection were examined with each of the four tests. Thirty (47%) of the 64 acute-phase sera were IgM positive by Meridian IC, 26 (41%) were positive by Remel EIA, 24 (38%) were positive by CF, and 15 (23%) were positive by ImmunoWELL-IgM. When both the acute- and convalescent-phase serum samples from each patient were examined, 61 (95%) of the 64 patients were positive by CF, 60 patients (94%) were positive by Remel EIA, 52 patients (81%) were IgM positive by the Meridian IC, and 29 patients (45%) were IgM positive by the ImmunoWELL-IgM assay. The Meridian IC was more sensitive than the other tests for early detection of IgM antibodies. However, after examining paired serum samples, we concluded that the detection of IgM alone may not be useful for all cases of mycoplasma infection, especially in an adult population.

Chlamydia pneumoniae and Mycoplasma pneumoniae immunoglobulin G (IgG) and IgA antibody seroprevalence rates and antibody levels related to age and gender were studied. The samples (n = 742) were collected during a nonepidemic period and analyzed by quantitative enzyme immunoassays (EIAs). Seroprevalence to C. pneumoniae was found to increase sharply in young children, and in the 15- to 19-year-old group it reached levels as high as 70 and 60% for IgG and IgA, respectively. After adolescence, seroprevalence showed a transient decrease and then continued to increase, although less dramatically than in early childhood. In the elderly the seroprevalence of IgG antibodies reached 75 and 100% in women and men, respectively. The corresponding rates of IgA antibodies were 73 and 100%. When a randomly selected subgroup of samples (n = 66) was analyzed in parallel by a microimmunofluorescence test and an EIA for C. pneumoniae IgA antibodies, similar seroprevalence rates were obtained (36 versus 35%). Seroprevalence to M. pneumoniae was already found to increase very sharply in 2- to 4-year-old children, reaching 16% for IgG and 8% for IgA. Seroprevalence to M. pneumoniae also continued to increase in adolescence, but in contrast to that to C. pneumoniae, the increase leveled off at about 40 to 50% in adulthood. In subjects aged over 65 years, prevalence did not exceed 60% for IgG or 35% for IgA. The seroprevalence patterns as well as the medians and variations of levels of C. pneumoniae and M. pneumoniae IgG antibodies were similar to those of corresponding IgA antibodies. Compared to IgG antibodies, IgA antibodies do not seem to be of additional value in the diagnosis of infections caused by these pathogens when single serum specimens are studied.

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.

Paired serum specimens from 17 patients with Mycoplasma pneumoniae infection, as demonstrated by a rise in complement fixation (CF) antibody titer and 14 single sera, negative in the CF test, were tested for the presence of Ig A, Ig G, and Ig M antibodies to a polypeptide with a molecular weight of 170 KDa (P1) in an immunoblot assay. In acute phase sera, collected in the 1st week of the disease, frequency of occurrence of the antibodies against P1 protein did not exceed 18%. Two to three weeks later, Ig A antibodies were detectable in 82.4%, Ig M in 76.5%, and Ig G antibodies in all convalescent phase sera. No sera negative in the CF test (titer < 4) had antibodies against M. pneumoniae adhesin P1.

The prevalence of antibodies to Mycoplasma pneumoniae was determined in normal Thai children by means of complement fixation. There were 445 children (243 boys and 202 girls) of different ages, ranging from newborn to 15 years. The lowest frequency of complement-fixing antibody was found in children age 1-3 months, and highest in children age 6-10 years which corresponds to the age distribution of symptomatic M. pneumoniae infection. The lowest and highest titers measured were less than 1:8 and 1:512 respectively. The prevalence of complement fixing antibody of titers more than or equal to 1:8, 1:32, 1:64 and 1:128 were 61.3, 31.7, 25.4 and 10.3 per cent of total children, respectively. Among children less than one month old, the frequency of complement fixing antibody of titers greater than or equal to 1:32 was 12.2 per cent and decreased to 1.3 per cent among children from the age 1-3 months. This decrease probably represented the disappearance of maternal antibody over this period. An increase in both the frequency and the geometric mean titer was seen thereafter. The peak frequency of high titers (greater than or equal to 1:32), 81.1 per cent, occurred in children 6-10 year of age. Paired sera were obtained from 72 children with high titers of greater than or equal to 1:64, 9.7 per cent had four fold changes of titer which indicated recent infection.(ABSTRACT TRUNCATED AT 250 WORDS)