Mycoplasma pneumoniae: acute illness, antibiotics, and subsequent pulmonary function

Bacteria in Asthma Pathogenesis

The airways are under continuous assault from aerosolized bacteria and oral flora. The bacteria present in the airways and gastrointestinal tract of neonates promote immune maturation and protect against asthma pathogenesis. Later bacterial infections and perturbations to the microbiome can contribute to asthma pathogenesis, persistence, and severity.

Microbiome in Mechanisms of Asthma

The lung and gut microbiome are factors in asthma risk or protection. Relevant elements of the microbiome within both niches include the importance of the early life window for microbiome establishment, the diversity of bacteria, richness of bacteria, and effect of those bacteria on the local epithelium and immune system. Mechanisms of protection include direct anti-inflammatory action or induction of non-type 2 inflammation by certain bacterial colonies. The gut microbiome further impacts asthma risk through the contribution of metabolic products. This article reviews the mechanisms that connect the lung and gut microbiota to asthma development and severity.

Mycoplasma pneumoniae induces allergy by producing P1-specific immunoglobulin E

BACKGROUND

Our previous study found that most Mycoplasma pneumoniae (MP) pneumonia (MPP)patients had elevated serum total immunoglobulin E (IgE) levels.

OBJECTIVE

To determine components of MP that can cause an IgE increase in children, and to clarify its specific mechanism.

METHODS

The components of MP cells were isolated by serum IgE from patients with MP pneumonia. These components obtained through the prokaryotic expression were used as allergens to detect the proportion of allergen-specific IgE produced in MPP patients, and the clinical characteristics and related immune parameters of these patients who produced this allergen-specific IgE were also analyzed. In addition, a cell experiment was used to verify the biological effect of these components in vitro.

RESULTS

P1-specific IgE was detected in serum of MPP children. An approximately 24-kDa polypeptide of P1 protein was obtained through prokaryotic expression purified by nickel agarose affinity chromatography. Approximately 9.2% of MPP patients produced IgE against this polypeptide of P1 protein, which was more likely to be produced in MPP patients with no history of allergies or family history of allergy-related diseases. P1-specific IgE-positive MPP patients had more severe clinical symptoms, with excessive secretion of interleukin (IL)-4 and IL-5 and overdifferentiation of Th0 cells into Th2 cells. Tests also demonstrated that the P1 protein stimulated excessive secretion of IL-4 and IL-5 in peripheral blood mononuclear cells from the peripheral blood of healthy donors.

CONCLUSION

Mycoplasma pneumoniae is not only an infectious agent but also an allergen for certain individuals. The P1 protein of MP can induce the production of P1-specific IgE.

Chronic Infection and Severe Asthma

Chronic bacterial infection is implicated in both the development and severity of asthma. The atypical bacteria Mycoplasma pneumoniae and Chlamydophila pneumoniae have been identified in the airways of asthmatics and correlated with clinical features such as adult onset, exacerbation risks, steroid sensitivity, and symptom control. Asthmatic patients with evidence of bacterial infection may benefit from antibiotic treatment directed towards these atypical organisms. Examination of the airway microbiome may identify microbial communities that confer risk for or protection from severe asthma.

Long-term effects of pneumonia in young children

Each year an estimated 120 million episodes of pneumonia occur in children younger than 5 years of age, resulting in one million deaths globally. Within this age group the lungs are still developing by increasing alveoli numbers and airway dimensions. Pneumonia during this critical developmental period may therefore adversely affect the lung's structure and function, with increased risk of subsequent chronic lung disease. However, there are few longitudinal studies of pneumonia in otherwise healthy children that extend into adulthood to help address this important question. Birth cohort, longitudinal, case-control and retrospective studies have reported restrictive and obstructive lung function deficits, asthma, bronchiectasis, and chronic obstructive pulmonary disease. In particular, severe hospitalised pneumonia had the greatest risk for long-term sequelae. Most studies, however, were limited by incomplete follow-up, some reliance upon parental recall, risk of diagnostic misclassification, and potential confounders such as nutrition, social deprivation, and pre-existing small airways or lungs. More long-term studies measuring lung function shortly after birth are needed to help disentangle the complex relationships between pneumonia and later chronic lung disease, while also addressing host responses, types of infection, and potential confounding variables. Meanwhile, parents of young children with pneumonia need to be advised about the importance of symptom resolution, post-pneumonia. In addition, paying attention to factors associated with optimising lung growth such as good nutrition, minimising exposure to air pollution, avoiding cigarette smoke, and decreasing the risk of preventable infections through good hygiene and having their children fully vaccinated should be emphasised. Finally, in the developing world and for disadvantaged communities in developed countries, public health policies leading to good quality housing and heating, hygiene, education, and improving socio-economic status are also essential.

Incident asthma and Mycoplasma pneumoniae: A nationwide cohort study

BACKGROUND

Previous studies investigating the relationship between Mycoplasma pneumoniae and incident asthma in the general population have been inconclusive.

OBJECTIVE

We conducted a nationwide cohort study to clarify this relationship.

METHODS

Using the National Health Insurance Research Database of Taiwan, we identified 1591 patients with M pneumoniae infection (International Classification of Diseases, Ninth Revision, Clinical Modification code 4830) given diagnoses between 2000 and 2008. We then frequency matched 6364 patients without M pneumoniae infection from the general population according to age, sex, and index year. Cox proportional hazards regression analysis was performed to determine the adjusted hazard ratio (aHR) of the occurrence of asthma in the M pneumoniae cohort compared with that in the non-M pneumoniae cohort.

RESULTS

Regardless of comorbidities and the use of antibiotic or steroid therapies, patients with M pneumonia infection had a higher risk of incident asthma than those without it. The aHR of asthma was 3.35 (95% CI, 2.71-4.15) for the M pneumoniae cohort, with a significantly higher risk when patients were stratified by age, sex, follow-up time, and comorbidities, including allergic rhinitis, atopic dermatitis, or allergic conjunctivitis. Patients with M pneumoniae infection had a higher risk of having early-onset (age, <12 years; aHR, 2.87) and late-onset (age, ≥12 years; aHR, 3.95) asthma. The aHR was also higher within the less than 2-year follow-up in the M pneumoniae cohort (aHR, 4.41; 95% CI, 3.40-5.74) than in the cohort without the infection.

CONCLUSION

This study found that incident cases of early-onset and late-onset asthma are closely related to M pneumoniae infection, even in nonatopic patients.

Macrolide antibiotics for treatment of asthma in adults: a meta-analysis of 18 randomized controlled clinical studies

Mounting studies have been showed that long-term macrolides used in patients with asthma could improve the lung function and symptoms. However, a large number of studies have reported inconclusive results. The aim of this meta-analysis was to investigate the effect of macrolide antibiotics in patients with asthma. We have performed a search in PubMed, Embase, China National Knowledge Internet (CNKI), and Wanfang databases. The weighed mean difference (WMD) or standardized mean difference (SMD) was used to evaluate the pooled effect. Statistical analysis was performed by STATA 11.0 software. Totally 1306 patients were included in the meta-analysis. The overall results indicated that statistically significance of long-term macrolides therapy in patients with asthma on forced expiratory volume in 1 s (FEV1) (WMD: 0.11, P < 0.01), peak expiratory flow (PEF) (SMD: 0.25, P = 0.001), airway hyper-responsiveness (AHR) (SMD: 0.90, P = 0.04), forced vital capacity (FVC) (WMD: 0.18, P = 0.05) and FEV1/FVC (WMD: 1.93, P < 0.001), but no statistically significance on FEV1/predict, FVC/predict, symptom scores, quality of life scores (QOL), reliever inhaler puffs per 24 h, and cell counts in sputum and blood. The subgroup analysis indicated macrolides could increase FEV1 and PEF in Caucasian and Asian, decrease AHR in Caucasian, while cells counts of sputum improvement among Asian. Therefore, the study suggested that long-term marolides therapy in asthma may improved the FEV1, PEF, AHR, FVC, FEV1/FVC and cells counts in sputum, but it can't improve other lung function (FEV1/predict and FVC/predict) and clinical outcomes (such as symptom, quality of life etc.).

Is asthma an infectious disease? New evidence

The pathogenetic mechanisms leading to asthma are likely to be diverse, influenced by multiple genetic polymorphisms as well as elements of the environment. Recent data on the microbiome of the airway have revealed intriguing differences between the number and diversity of microbial populations in healthy persons and asthmatics. There is convincing evidence that early viral infections, particularly with human rhinovirus and respiratory syncytial virus, are often associated with the development of chronic asthma and with exacerbations. Recent studies suggest that two unrelated types of atypical bacteria, Mycoplasma pneumoniae (Mpn) and Chlamydia pneumoniae, are present in the airways of a substantial proportion of the population, bringing up the possibility that the persistent presence of the organism may contribute to the asthmatic phenotype in a subset of patients. This review will examine the current data regarding a possible role for infection in chronic asthma with a particular focus on atypical bacterial infections.

Mycoplasma pneumoniae in children with acute and refractory asthma

BACKGROUND

The presence of Mycoplasma pneumoniae has been associated with worsening asthma in children. Sensitive assays have been developed to detect M pneumoniae-derived community-acquired respiratory distress syndrome (CARDS) toxin.

OBJECTIVES

To identify the frequency and persistence of M pneumoniae detection in respiratory secretions of children with and without asthma and to evaluate antibody responses to M pneumoniae and the impact of M pneumoniae on biological markers, asthma control, and quality of life.

METHODS

We enrolled 143 pediatric patients (53 patients with acute asthma, 26 patients with refractory asthma, and 64 healthy controls; age range, 5-17 years) during a 20-month period with 2 to 5 follow-up visits. We detected M pneumoniae using CARDS toxin antigen capture and polymerase chain reaction and P1 adhesin polymerase chain reaction. Immune responses to M pneumoniae were determined by IgG and IgM levels directed against CARDS toxin and P1 adhesin. pH was measured in exhaled breath condensates, and asthma control and quality of life were assessed using the Asthma Control Test and Pediatric Asthma Quality of Life Questionnaire.

RESULTS

M pneumoniae was detected in 64% of patients with acute asthma, 65% with refractory asthma, and 56% of healthy controls. Children with asthma had lower antibody levels to M pneumoniae compared with healthy controls. Exhaled breath condensate pHs and asthma control and quality of life scores were lower in M pneumoniae-positive patients with asthma.

CONCLUSION

The results suggest that M pneumoniae detection is common in children, M pneumoniae detection is associated with worsening asthma, and children with asthma may have poor humoral immune responses to M pneumoniae.

Long term sequelae from childhood pneumonia; systematic review and meta-analysis

Background

The risks of long term sequelae from childhood pneumonia have not been systematically assessed. The aims of this study were to: (i) estimate the risks of respiratory sequelae after pneumonia in children under five years; (ii) estimate the distribution of the different types of respiratory sequelae; and (iii) compare sequelae risk by hospitalisation status and pathogen.

Methods

We systematically reviewed published papers from 1970 to 2011. Standard global burden of disease categories (restrictive lung disease, obstructive lung disease, bronchiectasis) were labelled as major sequelae. ‘Minor’ sequelae (chronic bronchitis, asthma, other abnormal pulmonary function, other respiratory disease), and multiple impairments were also included. Thirteen papers were selected for inclusion. Synthesis was by random effects meta-analysis and meta-regression.

Results

Risk of at least one major sequelae was 5.5% (95% confidence interval [95% CI] 2.8–8.3%) in non hospitalised children and 13.6% [6.2–21.1%]) in hospitalised children. Adenovirus pneumonia was associated with the highest sequelae risk (54.8% [39.2–70.5%]) but children hospitalised with no pathogen isolated also had high risk (17.6% [10.9–24.3%]). The most common type of major sequela was restrictive lung disease (5.4% [2.5–10.2%]) . Potential confounders such as loss to follow up and median age at infection were not associated with sequelae risk in the final models.

Conclusions

All children with pneumonia diagnosed by a health professional should be considered at risk of long term sequelae. Evaluation of childhood pneumonia interventions should include potential impact on long term respiratory sequelae.

Infection, eosinophilia and childhood asthma

There is a growing list of viruses and bacteria associated with wheezing illness and asthma. It is well known that a few of these pathogens are strongly associated with wheezing illness and asthma exacerbations. What is not known is if early childhood infections with these pathogens cause asthma, and, if so, exactly what are the pathophysiologic mechanisms behind its development. The current consensus is respiratory infection works together with allergy to produce the immune and physiologic conditions necessary for asthma diasthesis. One link between respiratory infection and asthma may be the eosinophil, a cell that plays prominently in asthma and allergy, but can also be found in the body in response to infection. In turn, the eosinophil and its associated products may be novel therapeutic targets, or at the very least used to elucidate the complex pathophysiologic pathways of asthma and other respiratory illnesses. Together or separately, they can also be used for diagnosis, treatment and monitoring. The optimal care of a patient must take into consideration not only symptoms, but also the underlying disease mechanisms.

Stevens-Johnson syndrome in a boy with macrolide-resistant Mycoplasma pneumoniae pneumonia

Mycoplasma pneumoniae is a highly specialized parasitic bacterium that is a significant cause of community-acquired pneumonia in children. Although most such respiratory infections are mild, a minor percentage of patients require hospitalization and, occasionally, intensive treatment for respiratory failure. A variety of extrapulmonary sequelae of M pneumoniae infections have been described, including Stevens-Johnson syndrome. Macrolide resistance in M pneumoniae has developed rapidly in Asia, particularly in China, over the past decade and is now appearing in the United States. Emerging resistance to macrolides creates a therapeutic conundrum, particularly for pediatricians caring for young children in whom absolute or relative contraindications exist for the use of tetracyclines or fluoroquinolones, the 2 other main classes of drugs shown to be efficacious for M pneumoniae. We describe here the case of a child with a prolonged febrile illness associated with Stevens-Johnson-like mucocutaneous involvement who was found to have a respiratory infection with macrolide-resistant M pneumoniae.

Lower respiratory tract infections in cats: reaching beyond empirical therapy

PRACTICAL RELEVANCE

Lower respiratory tract infections (LRTIs) in cats can be due to bacteria, parasites, fungi and viruses. This review details the practical investigation of these infections and highlights specific therapy where possible. The aim is to avoid the all-too-frequent temptation in practice to treat cats with lower respiratory tract signs empirically for feline bronchial disease (FBD)/asthma. This is potentially hazardous as immunosuppressive therapy for FBD/asthma could exacerbate disease due to a LRTI. Empirical treatment of suspected LRTI is also difficult to recommend given the wide range of potential pathogens.

CLINICAL CHALLENGES

Making a clinical ante-mortem diagnosis of LRTI in a cat can be challenging. Consistent historical, clinical, haematological and radiographic abnormalities are often lacking and findings may be non-specific. Astute clinical acumen, thorough investigation and high quality laboratory analysis are usually required for a diagnosis. Bronchoalveolar lavage, if feasible, and tests for lungworm should be routine in cats with lower respiratory tract signs. Lung fine needle aspiration may be useful in cases of diffuse or nodular pulmonary disease. Histopathology is rarely employed in ante-mortem investigations.

EVIDENCE BASE

The authors have reviewed a substantial body of literature to provide information on many of the reported bacterial, parasitic, fungal and viral pathogens, including some that occur in Asia. Attention has been given to specific therapy for each pathogen, with evidence-based comments when there is a deviation from routine recommendations.

[Asthma and Mycoplasma pneumoniae]

INTRODUCTION

A growing body of basic and clinical science implicates Mycoplasma pneumonia in asthma, but its exact contribution to asthma development, exacerbation and persistence is as yet unclear.

STATE OF THE ART

M. pneumoniae infection, with the induction of bronchial hyperresponsiveness, seems to be a precipitating factor for asthma development in predisposed subjects. M. pneumoniae has been seen both in acute exacerbation (18-20%) and in chronically infected adults with stable asthma, where it may be enhancing chronic airway inflammation.

PERSPECTIVES

If M. pneumoniae plays a role in the development or progression of asthma, its eradication might influence the clinical course of the disease and improve symptoms. Macrolide treatment, with antimicrobial and anti-inflammatory properties, could have a place in the management of asthma, especially steroid-dependent asthma.

CONCLUSIONS

M. pneumoniae infection seems to be important in asthma pathogenesis and the clinical course of the disease. Difficulty in detecting the pathogen complicates investigations. Ongoing research will further determine the place of macrolide antibiotics in asthma management.

Potential contribution of fungal infection and colonization to the development of allergy

Fungi have long been recognized as an important source of allergens in patients with atopic disease. In this review, we explore the hypothesis that fungal exposures resulting in colonization or infection directly influence the tendency of an individual to develop allergic disease. According to this hypothesis, fungal exposures especially those early in life may influence the manner in which the immune response handles subsequent responses to antigen exposures. Studies detailing this potential connection between fungi have already provided important insights into the immunology of fungal-human interactions and offer the potential to provide new approaches and targets for the therapy of allergic disease. The first half of this review summarizes the data concerning fungal infections and asthma, including possible connections between fungal infections and urban asthma. The second half explores the potential role of the fungal gastrointestinal microbiota in promoting allergic inflammation.

Analysis of pulmonary inflammation and function in the mouse and baboon after exposure to Mycoplasma pneumoniae CARDS toxin

Mycoplasma pneumoniae produces an ADP-ribosylating and vacuolating toxin known as the CARDS (Community Acquired Respiratory Distress Syndrome) toxin that has been shown to be cytotoxic to mammalian cells in tissue and organ culture. In this study we tested the ability of recombinant CARDS (rCARDS) toxin to elicit changes within the pulmonary compartment in both mice and baboons. Animals responded to a respiratory exposure to rCARDS toxin in a dose and activity-dependent manner by increasing the expression of the pro-inflammatory cytokines IL-1α, 1β, 6, 12, 17, TNF-α and IFN-γ. There was also a dose-dependent increase in several growth factors and chemokines following toxin exposure including KC, IL-8, RANTES, and G-CSF. Increased expression of IFN-γ was observed only in the baboon; otherwise, mice and baboons responded to CARDS toxin in a very similar manner. Introduction of rCARDS toxin to the airways of mice or baboons resulted in a cellular inflammatory response characterized by a dose-dependent early vacuolization and cytotoxicity of the bronchiolar epithelium followed by a robust peribronchial and perivascular lymphocytic infiltration. In mice, rCARDS toxin caused airway hyper-reactivity two days after toxin exposure as well as prolonged airway obstruction. The changes in airway function, cytokine expression, and cellular inflammation correlate temporally and are consistent with what has been reported for M. pneumoniae infection. Altogether, these data suggest that the CARDS toxin interacts extensively with the pulmonary compartment and that the CARDS toxin is sufficient to cause prolonged inflammatory responses and airway dysfunction.

Increased serum interleukin-5 and vascular endothelial growth factor in children with acute mycoplasma pneumonia and wheeze

Acute mycoplasma pneumonia may be accompanied by wheeze in some children considered not to have asthma. The aim of the present study was to evaluate cytokine secretion in children with acute mycoplasma pneumonia and wheeze. We studied 58 patients with mycoplasma pneumonia (12 with wheeze, Group 1; 46 without wheeze, Group 2) and 36 patients of non-mycoplasma pneumonia (Group 3). Serum levels of interleukin (IL)-4, IL-5, interferon (IFN)-gamma, and vascular endothelial growth factor (VEGF) were measured using an enzyme-linked immunosorbent assay kits. The mean +/- SD IL-5 level of Group 1 was 97.1 +/- 73.0 pg/ml, which was significantly higher than that of Group 2 (28.2 +/- 32.2 pg/ml) and that of Group 3 (35.7 +/- 42.0 pg/ml). The mean +/- SD VEGF level of Group 1 was 687.5 +/- 385.8 pg/ml, which was significantly higher than that of Group 2 (310.0 +/- 251.9 pg/ml) and that of Group 3 (402.3 +/- 279.5 pg/ml). No significant differences in serum levels of IL-4, IFN-gamma, and IgE were observed between the groups. Our results show that children with mycoplasma pneumonia and wheeze have significantly higher serum levels of IL-5 and VEGF. These increased immune responses may be associated with the pathophysiological mechanisms by which the Mycoplasma pneumoniae contribute to the development of wheeze during acute mycoplasma pneumonia.

Asthma and atypical bacterial infection

A growing body of basic and clinical science implicates the atypical bacterial pathogens Mycoplasma pneumoniae and Chlamydophila (formerly Chlamydia) pneumoniae as potentially important factors in asthma, although their exact contribution to asthma development and/or persistence remains to be determined. Evidence from human studies links both M pneumoniae and C pneumoniae to new-onset wheezing, exacerbations of prevalent asthma, and long-term decrements in lung function, suggesting that these organisms can play an important role in the natural history of asthma. Furthermore, animal models of acute and chronic infection with these organisms indicate that they have the ability to modulate allergic sensitization and pulmonary physiologic and immune response to allergen challenge. These findings raise the possibility that, in at least some individuals with asthma, antibiotic therapy might have a role in long-term treatment. While antibiotics do not currently have a defined role in the treatment of stable patients with chronic asthma, there is emerging evidence that asthma symptoms and biomarkers of airway inflammation can improve when patients who have atypical bacterial infection as a cofactor in their asthma are treated with macrolide antibiotics. Ongoing research into the importance of atypical pathogens in asthma will further elucidate whether these infections are important in disease development or whether their prevalence is increased in asthmatic subjects due to chronic airway inflammation or other, yet unidentified, predisposing factors. Current studies will further define the role of macrolide antibiotics in the treatment of stable patients with asthma, ultimately determining whether these therapeutic agents have a place in asthma management.

Repeated respiratory Mycoplasma pneumoniae infections in mice: effect of host genetic background

Respiratory Mycoplasma pneumoniae (Mp) infection is involved in several acute and chronic lung diseases including community-acquired pneumonia, asthma and chronic obstructive pulmonary disease. In the chronic disease process, recurrent respiratory bacterial infections could occur, which may result in varying degrees of symptoms and lung inflammation among patients. However, the lung immunologic differences of host responses to repeated bacterial (i.e., Mp) infections remain to be determined. In the present study, we examined cellular and humoral responses to multiple (up to 3) Mp infections in two genetically different strains of mice (BALB/c and C57BL/6). Mice were intranasally inoculated with one Mp infection, two or three Mp infections (4 weeks apart), and sacrificed on days 3, 7 and 14 after the last Mp infection. Overall, compared to C57BL/6 mice, BALB/c mice demonstrated a significantly higher degree of lung tissue inflammatory cell infiltrate, BAL cellularity, and release of pro-inflammatory cytokines (TNF-alpha, keratinocyte-derived chemokine (KC, a mouse homolog of human chemokine Gro-alpha [CXCL1], and IFN-gamma). In addition, BALB/c mice presented higher levels of serum Mp-specific IgG and IgM, but not IgA. Consistently with lung and serum data, Mp load in BAL and lung specimens was significantly higher in BALB/c mice than C57BL/6 mice. Moreover, repeated Mp infections in BALB/c, but not C57BL/6 mice, produced a greater inflammatory response than did a single Mp infection. Our results suggest that hosts with different genetic background may have different susceptibility to repeated respiratory Mp infections along with inflammatory responses.

Evaluation of LBM415 (NVP PDF-713), a novel peptide deformylase inhibitor, for treatment of experimental Mycoplasma pneumoniae pneumonia

Mycoplasma pneumoniae is a major cause of community-acquired pneumonia. We evaluated the efficacy of LBM415, a novel peptide deformylase inhibitor antimicrobial agent, for the treatment of M. pneumoniae pneumonia in a mouse model. Eight-week-old BALB/c mice were intranasally inoculated once with 10(7) CFU of M. pneumoniae. Groups of mice were treated with LBM415 (50 mg/kg of body weight) or placebo subcutaneously daily for 13 days, starting 24 h after inoculation. Groups of mice were evaluated at the baseline; at days of treatment 1, 3, 6, and 13; and at 7 days after treatment. The MIC of LBM415 against M. pneumoniae was <0.005 microg/ml. LBM415-treated mice had significantly lower bronchoalveolar lavage fluid M. pneumoniae concentrations than placebo-treated mice on days 6 and 13 of treatment. Compared with placebo treatment, therapy with LBM415 significantly decreased lung histopathology scores at days 3, 6, and 13 of treatment and at 7 days after treatment. Airway obstruction was significantly lower in LBM415-treated mice than in placebo-treated mice on days 1, 3, and 6 of treatment and after 7 days of therapy, while airway hyperresponsiveness was significantly lower only on day 3 of therapy. The bronchoalveolar lavage fluid concentrations of tumor necrosis factor alpha, gamma interferon (IFN-gamma), interleukin-6 (IL-6), IL-12, KC (functional IL-8), monocyte chemotactic protein 1, macrophage inflammatory protein 1alpha, monokine induced by IFN-gamma, and IFN-inducible protein 10 were significantly reduced in LBM415-treated mice compared with the levels in placebo-treated mice. There were no differences in the bronchoalveolar lavage fluid concentrations of granulocyte-macrophage colony-stimulating factor, IL-1beta, IL-2, IL-4, IL-5, and IL-10 between the two groups of mice. LBM415 therapy had beneficial microbiologic, histologic, respiratory, and immunologic effects on acute murine M. pneumoniae pneumonia.

A role for the Mycoplasma pneumoniae adhesin P1 in interleukin (IL)-4 synthesis and release from rodent mast cells

Mycoplasma pneumoniae is a respiratory tract pathogen associated with exacerbations in patients with chronic asthma, yet relatively little is known about the potential role of this organism in asthma pathogenesis. Our previous studies demonstrated that RBL-2H3 mast cells co-cultured with M. pneumoniae released preformed inflammatory mediators, synthesized multiple cytokine mRNA species, and released IL-4 protein. In this study, we sought to determine the mechanism by which M. pneumoniae activates mast cell cytokine production. Cytokine mRNA upregulation and IL-4 protein production in RBL cells were induced almost exclusively by plastic-adherent M. pneumoniae cultures (MpA). Organisms grown under non-adherent conditions (MpN) were unable to induce cytokine responses efficiently. Western blots demonstrated that MpA was enriched for P1, the major M. pneumoniae adhesin, compared to MpN. M. pneumoniae-induced IL-4 release from RBL cells was inhibited >85% by anti-P1 monoclonal antibodies. Additionally, a P1-deficient strain of the bacteria was unable to efficiently induce IL-4 release. Desialation of RBL cell surface glycoproteins by neuraminidase treatment eliminated IL-4 release. We conclude that P1 plays an important role in M. pneumoniae-induced cytokine responses in RBL mast cells and that direct contact between the organism and sialated residues on the RBL surface mediates this activation.

Infectious triggers of asthma

There is abundant evidence that asthma is frequently exacerbated by infectious agents. Several viruses have been implicated in the inception and exacerbation of asthma. Recent attention has been directed at the role of infections with the atypical bacteria Mycoplasma pneumoniae and Chlamydia pneumoniae as agents capable of triggering asthma exacerbations and potentially as inciting agents for asthma. This article examines the evidence for interaction between specific infectious agents and exacerbations of asthma, including the immunopathology of infection-triggered asthma, and the current therapeutic options for management.

Atypical bacterial pneumonia and asthma risk

The role of respiratory infections in asthma is poorly understood. Atypical bacteria Mycoplasma pneumoniae and Chlamydia pneumoniae are present in the lower airways of approximately 50% of asthmatics. This study tested the hypothesis that early life community-acquired pneumonia caused by Mycoplasma pneumoniae or Chlamydia pneumoniae is associated with increased asthma prevalence. Thirty-five subjects with a history of community-acquired pneumonia (22 due to atypical bacteria, 13 due to nonatypical pathogens) were evaluated by questionnaire 7-9 years after the episode of pneumonia. Subjects with a history of either typical or atypical pneumonia demonstrated increased asthma prevalence. Current or past asthma prevalence was 55% in subjects with atypical bacterial pneumonia and 61.5% in subjects with nonatypical bacterial pneumonia. Significant between-group differences were not demonstrated with regard to asthma prevalence (risk ratio=0.89; 95% confidence interval=0.49-1.61), current bronchodilator use [1.18 (0.44-3.17)], and family history of atopy [1.18 (0.73-1.91)], or asthma [1.63 (0.68-3.88)]. These data suggest that atypical bacterial pneumonia confers a risk of asthma similar to that seen with nonatypical bacterial pneumonia. Prospective studies are warranted to more fully evaluate the importance of atypical bacterial pneumonia as an asthma risk factor.

Mycoplasma pneumoniae induces host-dependent pulmonary inflammation and airway obstruction in mice

Respiratory tract infections result in wheezing in a subset of patients. Mycoplasma pneumoniae is a common etiologic agent of acute respiratory infection in children and adults that has been associated with wheezing in 20-40% of individuals. The current study was undertaken to elucidate the host-dependent pulmonary and immunologic response to M. pneumoniae respiratory infection by studying mice with different immunogenetic backgrounds (BALB/c mice versus C57BL/6 mice). After M. pneumoniae infection, only BALB/c mice developed significant airway obstruction (AO) compared with controls. M. pneumoniae-infected BALB/c mice manifested significantly elevated airway hyperresponsiveness (AHR) compared with C57BL/6 mice 4 and 7 d after inoculation as well as BALB/c control mice. Compared with C57BL/6 mice, BALB/c mice developed worse pulmonary inflammation, including greater peribronchial infiltrates. Infected BALB/c mice had significantly higher concentrations of tumor necrosis factor-alpha, interferon-gamma, interleukin (IL)-1beta, IL-6, IL-12, KC (functional IL-8), and macrophage inflammatory protein 1alpha in the bronchoalveolar lavage fluid compared with infected C57BL/6 mice. No differences in IL-2, IL-4, IL-5, IL-10, and granulocyte/macrophage colony-stimulating factor concentrations were found. The mice in this study exhibited host-dependent infection-related AO and AHR associated with chemokine and T-helper type (Th)1 pulmonary host response and not Th2 response after M. pneumoniae infection.

Radiological and pulmonary function outcomes of children with SARS

We examined the radiological and pulmonary function outcomes of children affected with severe acute respiratory syndrome (SARS) at 6 months from diagnosis. Twenty-one female and 26 male Chinese patients (median age, 13.6 years; interquartile range, 9.9-16.0) were studied. In each subject, high-resolution computed tomography (HRCT) of the thorax and pulmonary function were assessed. All children were asymptomatic and had a normal clinical examination. Mild pulmonary abnormalities were detected on HRCT in 16 (34.0%) subjects, including residual ground-glass opacification (n = 5), air trapping (n = 8), and a combination of ground-glass changes and air trapping (n = 3). The need for oxygen supplementation (P = 0.02) and lymphopenia during the course of illness (P = 0.012) were significant risk factors in predicting abnormal HRCT. There were no significant lung function differences between those with and without HRCT abnormalities. Despite complete clinical resolution, a considerable proportion of children affected with SARS had abnormal HRCT findings at 6 months. These abnormalities were more prevalent in those with severe disease. It is important that careful follow-up be carried out to assess the clinical significance and persistence of such abnormalities.

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.

Impact of cethromycin (ABT-773) therapy on microbiological, histologic, immunologic, and respiratory indices in a murine model of Mycoplasma pneumoniae lower respiratory infection

Mycoplasma pneumoniae is a major etiologic agent of acute lower respiratory infections. We evaluated the antimicrobial and immunologic effects of cethromycin (ABT-773), a ketolide antibiotic, for the treatment of M. pneumoniae pneumonia in a mouse model. Eight-week-old BALB/c mice were inoculated intranasally once with 10(6) CFU of M. pneumoniae on day 0. Treatment was started 24 h after inoculation. Groups of mice were treated subcutaneously with cethromycin at 25 mg/kg of body weight or with placebo daily until sacrifice. Five to ten mice per group were evaluated at days 1, 4, 7, and 10 after inoculation. Outcome variables included bronchoalveolar lavage (BAL) for M. pneumoniae quantitative culture and cytokine and chemokine concentration determinations by enzyme-linked immunosorbent assay (tumor necrosis factor alpha [TNF-alpha], gamma interferon [IFN-gamma], interleukin-1beta [IL-1beta], IL-2, IL-4, IL-12, granulocyte-macrophage colony-stimulating factor, IL-8, monocyte chemoattractant protein 1 [MCP-1], and macrophage inflammatory protein 1alpha [MIP-1alpha]), histopathologic score of the lungs (HPS), and pulmonary function tests (PFT) using whole-body, unrestrained plethysmography at the baseline and post-methacholine exposure as indicators of airway obstruction (AO) and airway hyperresponsiveness (AHR), respectively. The cethromycin-treated mice had a greater reduction in M. pneumoniae culture titers than placebo-treated mice, reaching statistical significance on days 7 and 10 (P < 0.05). HPS was significantly reduced in cethromycin-treated mice compared with placebo-treated mice on days 4, 7, and 10 (P < 0.05). Cytokine concentrations in BAL samples were reduced in mice that received cethromycin, and the differences were statistically significant for 7 of the 10 cytokines measured (TNF-alpha, IFN-gamma, IL-1beta, IL-8, IL-12, MCP-1, and MIP-1alpha) on day 4 (P < 0.05). PFT values were improved in the cethromycin-treated mice, with AO and AHR significantly reduced on day 4 (P < 0.05). In this mouse model, treatment with cethromycin significantly reduced M. pneumoniae culture titers in BAL samples, cytokine and chemokine concentrations in BAL samples, histologic inflammation in the lungs, and disease severity as defined by AO and AHR.

Role of atypical bacterial infection of the lung in predisposition/protection of asthma

Asthma is a common inflammatory disease of the airways that results in airway narrowing and wheezing. Allergic asthma is characterised by a T-helper cell-type (Th) 2 response, immunoglobulin (Ig) E production, and eosinophilic influx into the airways. Recently, many clinical studies have implicated Mycoplasma pneumoniae and Chlamydia pneumoniae in the development and exacerbation of both chronic and acute asthma. It is widely accepted that M. pneumoniae and C. pneumoniae infections require Th1 immunity for clearance; therefore, according to the hygiene hypothesis, these infections should be protective against asthma. Here, we review the clinical evidence for the association and mechanisms of predisposition to and protection against asthma by these infections. We will examine the following question: Is it the absence of infection or the age of the individual on infection that confers susceptibility or resistance to asthma and does this vary between normal and predisposed individuals? We put forward a hypothesis of the effects of these infections on the development and prevention of asthma and how novel preventative and treatment strategies involving these microbes may be targeted against asthma.

Lower respiratory tract infections in cats: 21 cases (1995-2000)

Twenty-one lower respiratory tract infections diagnosed in cats at University of Sydney Veterinary Centre between 1995 and 2000 were identified retrospectively. Patient records were analysed to determine historical, clinical, clinicopathologic and radiographic features of lower respiratory tract infections. Response to therapy was also assessed. Infectious agents identified were Mycoplasma spp., Pasteurella spp., Bordetella bronchiseptica, Salmonella typhimurium, Pseudomonas sp., Mycobacterium thermoresistible, Cryptococcus neoformans, Toxoplasma gondii, Aelurostrongylus abstrusus and Eucoleus aerophilus. The study provides a detailed retrospective analysis of infectious lower respiratory tract disease in this population of cats.

A retrospective analysis of feline bronchoalveolar lavage cytology and microbiology (1995-2000)

A retrospective study of 88 bronchoalveolar lavage specimens from 80 cats presenting to the University of Sydney Veterinary Centre between 1995 and 2000 was performed. Bronchoalveolar lavage cytology and microbiology in conjunction with other diagnostic aids and patient records were used to classify cases as lower respiratory tract infections (LTRIs), LRTI revisits, feline bronchial disease, cardiac disease, neoplastic disease and multisystemic disease. Cases for which a definitive diagnosis could not be made were classified as inconclusive. Infectious agents identified were Mycoplasma spp., Pasteurella spp., Bordetella bronchiseptica, Salmonella typhimurium, Pseudomonas sp., Cryptococcus neoformans, Aelurostrongylus abstrusus and Eucoleus aerophilus. The study highlights the importance of bronchoalveolar lavage cytology and microbiology in the evaluation of feline lower respiratory tract disease.

Pharmacology of airway inflammation in asthma and COPD

The current asthma therapies are not cures and symptoms return soon after treatment is stopped even after long term treatment. Although inhaled glucocorticoids are highly effective in controlling airway inflammation in asthma, they are ineffective in the small group of patients with glucocorticoid-dependent and -resistant asthma. With very few exceptions, COPD is caused by tobacco smoking, and smoking cessation is the only truly effective treatment of COPD available. Current pharmacological treatment of COPD is unsatisfactory, as it does not significantly influence the severity of the disease or its natural course. Glucocorticoids are scarcely effective in COPD patients without concomitant asthma. Bronchodilators improves symptoms and quality of life, in COPD patients, but, with the exception of tiotropium, they do not significantly influence the natural course of the disease. Theophylline is the only drug which has been demonstrated to have a significant effect on airway inflammation in patients with COPD. Here we review the pharmacology of currently used antiinflammatory therapies for asthma and COPD and their proposed mechanisms of action. Recent understanding of disease mechanisms in severe steroid-dependent and -resistant asthma and in COPD, has lead to the development of novel compounds, which are in various stages of clinical development. We review the current status of some of these new potential drugs.

Mycoplasma disease and acute chest syndrome in sickle cell disease

BACKGROUND

Acute chest syndrome (ACS) is the leading cause of hospitalization, morbidity, and mortality in patients with sickle cell disease. Radiographic and clinical findings in ACS resemble pneumonia; however, etiologies other than infectious pathogens have been implicated, including pulmonary fat embolism (PFE) and infarction of segments of the pulmonary vasculature. The National Acute Chest Syndrome Study Group was designed to identify the etiologic agents and clinical outcomes associated with this syndrome.

METHODS

Data were analyzed from the prospective study of 671 episodes of ACS in 538 patients with sickle cell anemia. ACS was defined as a new pulmonary infiltrate involving at least 1 complete segment of the lung, excluding atelectasis. In addition, the patients had to have chest pain, fever >38.5C, tachypnea, wheezing, or cough. Samples of blood and deep sputum were analyzed for evidence of bacteria, viruses, and PFE. Mycoplasma pneumoniae infection was determined by analysis of paired serologies. Detailed information on patient characteristics, presenting signs and symptoms, treatment, and clinical outcome were collected.

RESULTS

Fifty-one (9%) of 598 episodes of ACS had serologic evidence of M pneumoniae infection. Twelve percent of the 112 episodes of ACS occurring in patients younger than 5 years were associated with M pneumoniae infection. At the time of diagnosis, 98% of all patients with M pneumoniae infection had fever, 78% had a cough, and 51% were tachypneic. More than 50% developed multilobar infiltrates and effusions, 82% were transfused, and 6% required assisted ventilation. The average hospital stay was 10 days. Evidence of PFE with M pneumoniae infection was seen in 5 (20%) of 25 patients with adequate deep respiratory samples for the PFE assay. M pneumoniae and Chlamydia pneumoniae was found in 16% of patients with diagnostic studies for C pneumoniae. Mycoplasma hominis was cultured in 10 (2%) of 555 episodes of ACS and occurred more frequently in older patients, but the presenting symptoms and clinical course was similar to those with M pneumoniae.

CONCLUSIONS

M pneumoniae is commonly associated with the ACS in patients with sickle cell anemia and occurs in very young children. M hominis should be considered in the differential diagnosis of ACS. Aggressive treatment with broad-spectrum antibiotics, including 1 from the macrolide class, is recommended for all patients as well as bronchodilator therapy, early transfusion, and respiratory support when clinically indicated.

Cytokine secretion in children with acute Mycoplasma pneumoniae infection and wheeze

The aim of this study was to evaluate cytokine secretion in children with acute Mycoplasma pneumoniae infection and wheeze. We studied 25 patients aged 2-14 years with an acute episode of wheezing (15 with acute M. pneumoniae infection) and 16 healthy controls of similar gender and age (8 with laboratory evidence of asymptomatic acute M. pneumoniae infection). Serum interleukin (IL)-2, interferon (IFN)-gamma, IL-4, and IL-5 concentrations were measured in samples obtained at enrollment, using enzyme-linked immunosorbent assay kits. In the presence of wheezing, IL-5 concentrations were significantly higher in subjects with acute M. pneumoniae infection (33.415 +/- 22.138 pg/mL) than in those without such infection (2.320 +/- 1.846 pg/mL, P < 0.0001). The children with acute M. pneumoniae infection and wheeze had higher IL-5 concentrations (33.415+/-22.138 pg/mL) than those with asymptomatic acute infection and without wheeze (1.740 +/- 2.299 pg/mL, P < 0.0001). No significant between-group differences were observed in terms of IL-2, IFN-gamma, or IL-4 levels, or the prevalence of atopy. Our results show that children with wheezing and acute M. pneumoniae infection have a specific cytokine profile characterized by a significant increase in serum levels of IL-5. This immune response may be important for understanding the pathophysiological mechanisms by which this pathogen contributes to the development of wheeze-related symptoms, and for identifying new treatment strategies.

Mycoplasma pneumoniae and Chlamydia pneumoniae in asthma: effect of clarithromycin

STUDY OBJECTIVES

To determine the effect of clarithromycin therapy in patients with asthma.

DESIGN

Randomized, double blind, placebo-controlled trial.

SETTING

A tertiary referral center.

PATIENTS OR PARTICIPANTS

Fifty-five subjects with chronic, stable asthma recruited from the general Denver, CO, community.

INTERVENTIONS

Patients underwent airway evaluation for Mycoplasma pneumoniae and Chlamydia pneumoniae by polymerase chain reaction (PCR) and culture, followed by treatment with clarithromycin, 500 bid, or placebo for 6 weeks.

MEASUREMENTS AND RESULTS

Outcome variables were lung function, sinusitis as measured by CT, and the inflammatory mediators tumor necrosis factor (TNF)-alpha, interleukin (IL)-2, IL-4, IL-5, and IL-12 messenger RNA (mRNA) measured via in situ hybridization, in airway biopsies, and BAL. Mycoplasma or chlamydia were detected by PCR in 31 of 55 asthmatics. Treatment resulted in a significant improvement in the FEV(1), but only in the PCR-positive subjects (2.50 +/- 0.16 to 2.69 +/- 0.19 L, mean +/- SEM; p = 0.05). This was not appreciated in the PCR-negative subjects (2.59 +/- 0.24 to 2.54 +/- 0.18 L, p = 0.85) or the PCR-positive or PCR-negative subjects who received placebo. Sinus CTs revealed no change in sinusitis with clarithromycin treatment. In situ hybridization revealed no significant difference in baseline airway tissue or BAL-mediator expression between the PCR-positive and PCR-negative subjects. However, the PCR-positive subjects who received clarithromycin demonstrated a reduction in TNF-alpha (p = 0.006), IL-5 (p = 0.007), and IL-12 (p = 0.004) mRNA in BAL and TNF-alpha mRNA in airway tissue (p = 0.0009). The PCR-negative subjects who received clarithromycin only demonstrated a reduction in TNF-alpha (p = 0.01) and IL-12 (p = 0.002) mRNA in BAL and TNF-alpha mRNA in airway tissue (p = 0.004). There were no significant differences in cytokine expression in those subjects who received placebo.

CONCLUSIONS

These observations support the hypothesis that clarithromycin therapy improves lung function, but only in those subjects with positive PCR findings for M pneumoniae or C pneumoniae.

Mycoplasma pneumoniae-induced activation and cytokine production in rodent mast cells

BACKGROUND

Mycoplasma pneumoniae is a respiratory tract pathogen that has been associated with severe exacerbations in patients with chronic asthma. Murine models of infection have recently been established, with disease manifestations similar to those observed in human subjects. Previous studies have suggested that this organism is capable of producing activation of a wide range of immunologic cell types.

OBJECTIVE

We sought to determine whether M pneumoniae can induce mast cell activation in the rodent mast cell line RBL-2H3.

RESULTS

After 4 hours of coculture, morphologic changes indicative of activation were observed by means of electron microscopy, and M pneumoniae was identified, by means of immunoelectron microscopy, adhering to mast cell membranes. Coculture of rat basophilic leukemia cells with viable M pneumoniae for 4 hours resulted in net release of beta-hexosaminidase and serotonin into the supernatant. Live, but not heat-killed, organisms induced the release of IL-4 protein into the culture supernatant, with a peak at 4 hours. During coculture with M pneumoniae, production of mRNA for IL-4, IL-6, and TNF-alpha was upregulated after 2 hours and had returned to near baseline by 24 hours after infection.

CONCLUSIONS

We conclude that viable M pneumoniae induces activation of mast cells with release of granule contents, as well as cytokine production.

Emerging role of Mycoplasma pneumoniae and Chlamydia pneumoniae in paediatric respiratory-tract infections

Increased use of specialised diagnostic techniques over the past 10 years has allowed considerable new information to be obtained concerning Mycoplasma pneumoniae and Chlamydia pneumoniae infections. In children, these pathogens seem to have a more important role in causing respiratory-tract infections than previously thought; they have been associated with wheezing, and they are also frequent in children aged under 5 years. Contrary to original belief, no clinical, laboratory, or radiological findings seem to be unique to M. pneumoniae or C. pneumoniae; furthermore, there is no rapid and cost-effective diagnostic test capable of identifying these pathogens. Appropriate antimicrobial treatment of the infections they cause is needed to reduce the recurrent episodes of wheezing and other respiratory symptoms, to decrease morbidity, and to avoid the spread of the pathogens. However, a number of therapeutic issues remain unsolved.

Asthma in children: are chlamydia or mycoplasma involved?

Asthma aetiology is complex, involving interactions between genetic susceptibility, allergen exposure and external aggravating factors such as air pollution, smoking and respiratory tract infections. Available evidence supports a role for acute Chlaymdia pneumoniae or Mycoplasma pneumoniae respiratory tract infection as a trigger for 5 to 30% of wheezing episodes and asthma exacerbations. It also appears that acute infections with C. pneumoniae and M. pneumoniae can initiate asthma in some previously asymptomatic patients; however, the quantitative role for these atypical bacteria as asthma initiators is unknown at the present time. Whether chronic infections with these agents play an important role in persistent asthma symptoms and/or to asthma severity is unclear and additional information should be acquired before definite conclusions can be reached. Improvement in asthma symptoms after antimicrobial therapy active against C. pneumoniae and M. pneumoniae has been observed. In some studies C. pneumoniae seems to be more important for asthma pathogenesis and exacerbations than M. pneumoniae; in other reports the role of M. pneumoniae appears to be more significant. However, a number of questions remain unanswered. Carefully controlled randomised trials are clearly warranted to determine whether infection with atypical bacteria is really associated with asthma and to define the appropriate role of antimicrobial treatment.

Elevated cytokine and chemokine levels and prolonged pulmonary airflow resistance in a murine Mycoplasma pneumoniae pneumonia model: a microbiologic, histologic, immunologic, and respiratory plethysmographic profile

Because Mycoplasma pneumoniae is hypothesized to play an important role in reactive airway disease/asthma, a comprehensive murine model of M. pneumoniae lower respiratory infection was established. BALB/c mice were intranasally inoculated once with M. pneumoniae and sacrificed at 0 to 42 days postinoculation. All mice became infected and developed histologic evidence of acute pulmonary inflammation, which cleared by 28 days postinoculation. By contrast, M. pneumoniae persisted in the respiratory tract for the entire 42 days studied. Tumor necrosis factor alpha, gamma interferon, interleukin-6 (IL-6), KC (functional IL-8), MIP-1alpha, and MCP-1/JE concentrations were significantly elevated in bronchoalveolar lavage samples, whereas IL-4 and IL-10 concentrations were not significantly elevated. Pulmonary airflow resistance, as measured by plethysmography, was detected 1 day postinoculation and persisted even after pulmonary inflammation had resolved at day 28. Serum anti-M. pneumoniae immunoglobulin G titers were positive in all mice by 35 days. This mouse model provides a means to investigate the immunopathogenesis of M. pneumoniae infection and its possible role in reactive airway disease/asthma.

Respiratory infections and asthma

Clinical and experimental evidence suggests an important role for respiratory infections in the development of asthma attacks. Viral upper respiratory infections have been associated with 80% of asthma exacerbations in children and 50% of all asthma episodes in adults. Human rhinovirus has been implicated as the principal virus associated with asthma episodes. Separate studies indicate that atypical bacteria such as Chlamydia pneumoniae and Mycoplasma pneumoniae may precipitate asthma symptoms. Although not completely clarified, the intricate pathogenetic mechanisms by which viral infections promote asthma attacks have been extensively investigated in recent years. By contrast, it has not yet been established whether atypical bacterial infections are an epiphenomenon or a pathogenic event in asthma.

Reduced lung diffusion capacity after Mycoplasma pneumoniae pneumonia

BACKGROUND

Mycoplasma pneumoniae is a frequent but underdiagnosed cause of community-acquired pneumonia (CAP) in children, and appropriate macrolide treatment is often given late. The aim of this work was to estimate the frequency of pulmonary involvement in children 6 months after a clinical episode of Mycoplasma CAP.

METHODS

We measured carbon monoxide diffusion capacity (TLCO) and conducted spirometric tests in 35 children without asthma or chronic lung disease (ages 4.5 to 15 years), 6 months and 1 year after acute CAP caused by M. pneumoniae (23 children), pneumococci (5 children) or viruses (7 children). Only 11 of 23 patients with M. pneumoniae CAP required hospitalization, whereas all the patients with pneumococcal or viral pneumonia were admitted to hospital.

RESULTS

Lung volumes and spirometric tests were normal for all children. TLCO was normal 6 months after pneumococcal or viral pneumonia (87 to 112% of expected values for height and sex). After acute M. pneumoniae CAP, 11 of 23 patients (48%) had TLCO values <80% of the expected value. The extent of change in lung diffusion capacity was correlated with the delay to diagnosis and treatment: TLCO was low in 8 of 11 patients given macrolide treatment 10 days or more after the onset of acute symptoms vs. only 3 of 10 patients given appropriate treatment in the first 10 days. TLCO was low in 7 of 7 who received macrolide therapy for <2 weeks. TLCO had increased slightly after 1 year in the 5 patients retested after a new course of macrolide treatment. TLCO reached the lower normal range in 2 patients controlled after 3 years.

CONCLUSIONS

The abnormal TLCO values suggest that some children with Mycoplasma pneumonia have reduced pulmonary gas diffusion after recovery from the illness. The reduction is related to delay and short macrolide therapy.

The role of bacterial infections in asthma

In summary, bacterial organisms are clinically relevant contributors to asthma exacerbations, and have received much less attention than viruses in this process. Streptococcus pneumoniae, Hemophilus influenzae, and Moraxella catarrhalis have been linked to asthma exacerbations, particularly when sinusitis is present. Treatment therefore should be directed toward these organisms if a bacterial cause is suspected. The atypical bacteria--specifically, C. pneumoniae and M. pneumoniae--deserve special attention. Data suggest a link between these organisms and the exacerbation of asthma, as well as suggest that these organisms may be causative in asthma development. The existing data are not conclusive, but are suggestive enough to drive studies evaluating them as a possible mechanism in asthma pathogenesis. An animal model evaluating M. pneumoniae and C. pneumoniae would be ideal, but at present no model exists in which chronic infection with these organisms results in bronchial hyperresponsiveness. There is active work in this area, however. Alternative investigations include continued evaluation of these organisms by several modalities, including culture, serology, and PCR, along with evaluation of the host response. Many questions remain, but the ground is fertile for continued investigation.

Late abnormal findings on high-resolution computed tomography after Mycoplasma pneumonia

BACKGROUND

The clinical course of Mycoplasma pneumonia is typically mild and self-limited. There are, however, several case reports of severe complication following this illness with considerable morbidity and mortality.

OBJECTIVES

This study was conducted to investigate, using high-resolution computed tomography (HRCT), the long-term pulmonary structural abnormalities after Mycoplasma pneumonia and to identify risk factors (chest radiograph findings, antibody titers, and host factors) that might increase the likelihood of developing the sequelae.

METHODS

Thirty-eight children requiring hospitalization attributable to Mycoplasma pneumonia were recruited by the retrospective examination of hospital records. They underwent HRCT after an interval of 1.0 to 2. 2 years. A control group of 17 children with the history of Mycoplasma upper respiratory infection was also studied after a similar interval.

RESULTS

Abnormal HRCT findings were present in 37% (14/38) of the pneumonia group, compared with 12% (2/17) of the control group. The abnormalities in the pneumonia group, which appeared alone or in combination, included mosaic perfusion (n = 12), bronchiectasis (n = 8), bronchial wall thickening (n = 4), decreased vascularity (n = 1), and air trapping on expiratory scan (9 of 29 tested). The area affected by these abnormalities, usually involving 2 or more lobes, corresponded in all cases to the location of the infiltrate on chest radiograph at the time of pneumonia. Between subjects with abnormal HRCT (n = 14) and normal HRCT (n = 24) in the pneumonia group, significant differences were observed in age at the time of pneumonia (mean +/- standard deviation: 5.3 +/- 2. 0 years vs 7.7 +/- 3.4 years) and peak antimycoplasma antibody titer (geometric mean [range of 1 standard deviation]; 1:7943 [3126-19 953] vs 1:3093 [832-11 482]).

CONCLUSIONS

We conclude that a considerable proportion of children with history of Mycoplasma pneumonia have abnormal findings on HRCT, suggestive of small airway obstruction and that younger age and higher antibody titer at the time of pneumonia may be risk factors for these sequelae.

Detection of Mycoplasma pneumoniae in the airways of adults with chronic asthma

Infection with Mycoplasma pneumoniae has been shown to exacerbate asthma in humans. However, the role of M. pneumoniae in the pathogenesis of chronic asthma has not been defined. Eighteen asthmatics with chronic, stable asthma and 11 nonasthmatic control subjects underwent evaluation of the upper and lower airways and serologic analysis to determine the presence of M. pneumoniae, Chlamydia pneumoniae, and seven respiratory viruses through culture, enzyme-linked immunoassay (EIA) and polymerase chain reaction (PCR). M. pneumoniae was detected by PCR in 10 of 18 asthmatics and one of 11 control subjects (p = 0.02). In nine of the 10 patients, the organism was detected in bronchoalveolar lavage or bronchial biopsies. Seven of 18 asthmatics and one of 11 control subjects were also positive for M. fermentans and M. genitalium by PCR. All patients' cultures, EIAs, and serology were negative for M. pneumoniae. All PCR and cultures were negative for C. pneumoniae, and all EIAs for respiratory viruses were negative in all subjects. Nine asthmatics and one control subject exhibited positive serology for C. pneumoniae (p = 0.05). M. pneumoniae was present in the lower airways of chronic, stable asthmatics with greater frequency than control subjects, and may play a role in the pathogenesis of chronic asthma.

Infectious causes of chronic inflammatory diseases and cancer

Powerful diagnostic technology, plus the realization that organisms of otherwise unimpressive virulence can produce slowly progressive chronic disease with a wide spectrum of clinical manifestations and disease outcomes, has resulted in the discovery of new infectious agents and new concepts of infectious diseases. The demonstration that final outcome of infection is as much determined by the genetic background of the patient as by the genetic makeup of the infecting agent is indicating that a number of chronic diseases of unknown etiology are caused by one or more infectious agents. One well-known example is the discovery that stomach ulcers are due to Helicobacter pylori. Mycoplasmas may cause chronic lung disease in newborns and chronic asthma in adults, and Chlamydia pneumoniae, a recently identified common cause of acute respiratory infection, has been associated with atherosclerosis. A number of infectious agents that cause or contribute to neoplastic diseases in humans have been documented in the past 6 years. The association and causal role of infectious agents in chronic inflammatory diseases and cancer have major implications for public health, treatment, and prevention.