The role of atypical pathogens: Mycoplasma pneumoniae, Chlamydia pneumoniae, and Legionella pneumophila in respiratory infection

Respiratory Tract Infections and Laboratory Diagnostic Methods: A Review with A Focus on Syndromic Panel-Based Assays

Respiratory tract infections (RTIs) are the focus of developments in public health, given their widespread distribution and the high morbidity and mortality rates reported worldwide. The clinical spectrum ranges from asymptomatic or mild infection to severe or fatal disease. Rapidity is required in diagnostics to provide adequate and prompt management of patients. The current algorithm for the laboratory diagnosis of RTIs relies on multiple approaches including gold-standard conventional methods, among which the traditional culture is the most used, and innovative ones such as molecular methods, mostly used to detect viruses and atypical bacteria. The implementation of molecular methods with syndromic panels has the potential to be a powerful decision-making tool for patient management despite requiring appropriate use of the test in different patient populations. Their use radically reduces time-to-results and increases the detection of clinically relevant pathogens compared to conventional methods. Moreover, if implemented wisely and interpreted cautiously, syndromic panels can improve antimicrobial use and patient outcomes, and optimize laboratory workflow. In this review, a narrative overview of the main etiological, clinical, and epidemiological features of RTI is reported, focusing on the laboratory diagnosis and the potentialities of syndromic panels.

Clinical Evaluation of a Novel Point-of-Care Assay To Detect Mycoplasma pneumoniae and Associated Macrolide-Resistant Mutations

The recent increase in macrolide-resistant Mycoplasma pneumoniae in Asia has become a continuing problem. A point-of-care testing method that can quickly detect M. pneumoniae and macrolide-resistant mutations (MR mutations) is critical for proper antimicrobial use. Smart Gene (Mizuho Medy Co., Ltd., Tosu City, Saga, Japan) is a compact and inexpensive fully automatic gene analyzer that combines amplification with PCR and the quenching probe method to specify the gene and MR mutations simultaneously. We performed a clinical evaluation of this device and its reagents on pediatric patients with suspected M. pneumoniae respiratory infections and evaluated the impact of the assay on antimicrobial selection. Using real-time PCR as a comparison control, the sensitivity of Smart Gene was 97.8% (44/45), its specificity was 93.3% (98/105), and its overall concordance rate was 94.7% (142/150). The overall concordance rate of Smart Gene diagnosis of MR mutations in comparison with sequence analysis was 100% (48/48). The ratio of MR mutations was significantly higher at high-level medical institutions than at a primary medical clinic (P = 0.023), and changes in antibiotic therapy to drugs other than macrolides were significantly more common in patients with MR mutations (P = 0.00024). Smart Gene demonstrated excellent utility in the diagnosis of M. pneumoniae and the selection of appropriate antimicrobials for MR mutations at primary medical institutions, which play a central role in community-acquired pneumonia care. The use of this device may reduce referrals to high-level medical institutions for respiratory infections, thereby reducing the medical and economic burdens on patients.

Epidemiology and Molecular Characteristics of Mycoplasma pneumoniae During an Outbreak of M. pneumoniae-associated Stevens-Johnson Syndrome

BACKGROUND

An increase in Mycoplasma pneumoniae-associated Stevens-Johnson syndrome (SJS) cases at a Colorado pediatric hospital led to an outbreak investigation. We describe the epidemiologic and molecular characteristics of M. pneumoniae among SJS case-patients and surrounding community members during the outbreak.

METHODS

M. pneumoniae polymerase chain reaction-positive respiratory specimens from 5 Colorado hospitals and 4 referral laboratories underwent confirmatory polymerase chain reaction testing; positive specimens then underwent multilocus variable-number tandem-repeat analysis (MLVA) and macrolide resistance testing. Three SJS-M. pneumoniae case-patient households were surveyed using a standardized questionnaire, and nasopharyngeal/oropharyngeal swabs were obtained from all consenting/assenting household contacts. International Classification of Diseases, 9th revision codes were used to identify pneumonia cases among Colorado patients 5-21 years of age from January 2009 to March 2014.

RESULTS

Three different M. pneumoniae MLVA types were identified among the 5 SJS case-patients with confirmed infection; MLVA type 3-X-6-2 was seen more commonly in SJS case-patients (60%) than in 69 non-SJS community specimens (29%). Macrolide resistance was identified in 7% of community specimens but not among SJS case-patients. Of 15 household contacts, 5 (33%) were M. pneumoniae positive; all MLVA types were identical to those of the corresponding SJS case-patient, although the specimen from 1 contact was macrolide resistant. Overall pneumonia cases as well as those caused by M. pneumoniae specifically peaked in October 2013, coinciding with the SJS outbreak.

CONCLUSIONS

The outbreak of M. pneumoniae-associated SJS may have been associated with a community outbreak of M. pneumoniae; clinicians should be aware of the M. pneumoniae-SJS relationship. Household transmission of M. pneumoniae was common within the households investigated.

Pathogenesis of Mycoplasma pneumoniae: An update

Genus Mycoplasma, belonging to the class Mollicutes, encompasses unique lifeforms comprising of a small genome of 8,00,000 base pairs and the inability to produce a cell wall under any circumstances. Mycoplasma pneumoniae is the most common pathogenic species infecting humans. It is an atypical respiratory bacteria causing community acquired pneumonia (CAP) in children and adults of all ages. Although atypical pneumonia caused by M. pneumoniae can be managed in outpatient settings, complications affecting multiple organ systems can lead to hospitalization in vulnerable population. M. pneumoniae infection has also been associated with chronic lung disease and bronchial asthma. With the advent of molecular methods of diagnosis and genetic, immunological and ultrastructural assays that study infectious disease pathogenesis at subcellular level, newer virulence factors of M. pneumoniae have been recognized by researchers. Structure of the attachment organelle of the organism, that mediates the crucial initial step of cytadherence to respiratory tract epithelium through complex interaction between different adhesins and accessory adhesion proteins, has been decoded. Several subsequent virulence mechanisms like intracellular localization, direct cytotoxicity and activation of the inflammatory cascade through toll-like receptors (TLRs) leading to inflammatory cytokine mediated tissue injury, have also been demonstrated to play an essential role in pathogenesis. The most significant update in the knowledge of pathogenesis has been the discovery of Community-Acquired Respiratory Distress Syndrome toxin (CARDS toxin) of M. pneumoniae and its ability of adenosine diphosphate (ADP) ribosylation and inflammosome activation, thus initiating airway inflammation. Advances have also been made in terms of the different pathways behind the genesis of extrapulmonary complications. This article aims to comprehensively review the recent advances in the knowledge of pathogenesis of this organism, that had remained elusive during the era of serological diagnosis. Elucidation of virulence mechanisms of M. pneumoniae will help researchers to design effective vaccine candidates and newer therapeutic targets against this agent.

Etiology, seasonality, and clinical characterization of viral respiratory infections among hospitalized children in Beirut, Lebanon

Acute respiratory tract viral infections occur worldwide and are one of the major global burdens of diseases in children. The aim of this study was to determine the viral etiology of respiratory infections in hospitalized children, to understand the viral seasonality in a major Lebanese hospital, and to correlate disease severity and the presence of virus. Over a 1‐year period, nasal and throat swabs were collected from 236 pediatric patients, aged 16‐year old or less and hospitalized for acute respiratory illness. Samples collected were tested for the presence of 17 respiratory viruses using multiplex real‐time RT‐PCR. Pathogens were identified in 165 children (70%) and were frequently observed during fall and winter seasons. Co‐infection was found in 37% of positive samples. The most frequently detected pathogens were human Rhinovirus (hRV, 23%), Respiratory Syncytial Virus (RSV, 19%), human Bocavirus (hBov, 15%), human Metapneumovirus (hMPV, 10%), and human Adenovirus (hAdV, 10%). A total of 48% of children were diagnosed with bronchiolitis and 25% with pneumonia. While bronchiolitis was often caused by RSV single virus infection and hAdV/hBoV coinfection, pneumonia was significantly associated with hBoV and HP1V1 infections. No significant correlation was observed between a single viral etiology infection and a specific clinical symptom. This study provides relevant facts on the circulatory pattern of respiratory viruses in Lebanon and the importance of using PCR as a useful tool for virus detection. Early diagnosis at the initial time of hospitalization may reduce the spread of the viruses in pediatric units. J. Med. Virol. 88:1874–1881, 2016. © 2016 Wiley Periodicals, Inc.

Simultaneous detection of Legionella species and L. anisa, L. bozemanii, L. longbeachae and L. micdadei using conserved primers and multiple probes in a multiplex real-time PCR assay

Legionnaires' disease is a severe respiratory disease that is estimated to cause between 8,000 and 18,000 hospitalizations each year, though the exact burden is unknown due to under-utilization of diagnostic testing. Although Legionella pneumophila is the most common species detected in clinical cases (80-90%), other species have also been reported to cause disease. However, little is known about Legionnaires' disease caused by these non-pneumophila species. We designed a multiplex real-time PCR assay for detection of all Legionella spp. and simultaneous specific identification of four clinically-relevant Legionella species, L. anisa, L. bozemanii, L. longbeachae, and L. micdadei, using 5'-hydrolysis probe real-time PCR. The analytical sensitivity for detection of nucleic acid from each target species was ≤50fg per reaction. We demonstrated the utility of this assay in spiked human sputum specimens. This assay could serve as a tool for understanding the scope and impact of non-pneumophila Legionella species in human disease.

The Evolution of Advanced Molecular Diagnostics for the Detection and Characterization of Mycoplasma pneumoniae

Over the past decade there have been significant advancements in the methods used for detecting and characterizing Mycoplasma pneumoniae, a common cause of respiratory illness and community-acquired pneumonia worldwide. The repertoire of available molecular diagnostics has greatly expanded from nucleic acid amplification techniques (NAATs) that encompass a variety of chemistries used for detection, to more sophisticated characterizing methods such as multi-locus variable-number tandem-repeat analysis (MLVA), Multi-locus sequence typing (MLST), matrix-assisted laser desorption ionization-time-of-flight mass spectrometry (MALDI-TOF MS), single nucleotide polymorphism typing, and numerous macrolide susceptibility profiling methods, among others. These many molecular-based approaches have been developed and employed to continually increase the level of discrimination and characterization in order to better understand the epidemiology and biology of M. pneumoniae. This review will summarize recent molecular techniques and procedures and lend perspective to how each has enhanced the current understanding of this organism and will emphasize how Next Generation Sequencing may serve as a resource for researchers to gain a more comprehensive understanding of the genomic complexities of this insidious pathogen.

Extended release amoxicillin/clavulanate: optimizing a product for respiratory infections based on pharmacodynamic principles

Acute bacterial respiratory tract infections cause a great deal of human morbidity and mortality. Treatment guidelines for these infections include macrolides, doxycycline, beta-lactams and beta-lactam/beta-lactamase inhibitor combinations such as amoxicillin/clavulanic acid to provide coverage for the common respiratory pathogens, including penicillin and macrolide nonsusceptible Streptococcus pneumoniae, as well as beta-lactamase-producing Haemophilus influenzae and Moraxella catarrhalis. In response to recent guidelines recommending higher dose amoxicillin to extend coverage to a higher percentage of S. pneumoniae, a new formulation of amoxicillin/clavulanic acid was developed. This formulation includes a higher amoxicillin dose, with part of the amoxicillin dose being in an extended release formulation, without increasing the clavulanate dose, for twice-daily oral treatment of these infections. Clinical studies of community-acquired pneumonia and acute rhinosinusitis have shown that the new formulation is well tolerated and highly efficacious, with clinical outcomes equivalent to comparators.

Does empiric therapy for atypical pathogens improve outcomes for patients with CAP?

The present controversy regarding the need to cover atypical pathogens in the empiric therapy of community-acquired pneumonia is related to several issues, including the relevance of terminology, imprecise diagnostic methods, and perceived contradictory results of published evidence. Studies evaluating the time to clinical recovery and the use of earlier endpoints for evaluation suggest that appropriate therapy provides a benefit if an atypical pathogen is a pathogen. Because recent surveillance studies suggest these pathogens are common and until there is the availability of accurate, cost-effective, and easily interpreted laboratory tests to provide the etiologic diagnosis at the time of point of care, empiric therapy of atypical pathogens is supported.

Mycoplasma pneumonia: Clinical features and management

Mycoplasma pneumonia is a common respiratory pathogen that produces diseases of varied severity ranging from mild upper respiratory tract infection to severe atypical pneumonia. Apart from respiratory tract infections, this organism is also responsible for producing a wide spectrum of non-pulmonary manifestations including neurological, hepatic, cardiac diseases, hemolytic anemia, polyarthritis and erythema multiforme. This review focuses on molecular taxonomy, biological characteristics, epidemiology, clinical presentation, radiology and various laboratory tools in diagnosis, differential diagnosis, treatment and prevention of mycoplasma pneumonia.

Multistep resistance development studies of ceftaroline in gram-positive and -negative bacteria

Ceftaroline, the active component of the prodrug ceftaroline fosamil, is a novel broad-spectrum cephalosporin with bactericidal activity against Gram-positive and -negative isolates. This study evaluated the potential for ceftaroline and comparator antibiotics to select for clones of Streptococcus pneumoniae, Streptococcus pyogenes, Haemophilus influenzae, Moraxella catarrhalis, Klebsiella pneumoniae, Staphylococcus aureus, and Enterococcus faecalis with elevated MICs. S. pneumoniae and S. pyogenes isolates in the present study were highly susceptible to ceftaroline (MIC range, 0.004 to 0.25 μg/ml). No streptococcal strains yielded ceftaroline clones with increased MICs (defined as an increase in MIC of >4-fold) after 50 daily passages. Ceftaroline MICs for H. influenzae and M. catarrhalis were 0.06 to 2 μg/ml for four strains and 8 μg/ml for a β-lactamase-positive, efflux-positive H. influenzae with a mutation in L22. One H. influenzae clone with an increased ceftaroline MIC (quinolone-resistant, β-lactamase-positive) was recovered after 20 days. The ceftaroline MIC for this isolate increased 16-fold, from 0.06 to 1 μg/ml. MICs for S. aureus ranged from 0.25 to 1 μg/ml. No S. aureus isolates tested with ceftaroline had clones with increased MIC (>4-fold) after 50 passages. Two E. faecalis isolates tested had ceftaroline MICs increased from 1 to 8 μg/ml after 38 days and from 4 to 32 μg/ml after 41 days, respectively. The parental ceftaroline MIC for the one K. pneumoniae extended-spectrum β-lactamase-negative isolate tested was 0.5 μg/ml and did not change after 50 daily passages.

Management of community-acquired pneumonia: a review and update

Community-acquired pneumonia (CAP) is a leading cause of morbidity and mortality worldwide, affecting approximately 5.6 million patients annually in the USA, where the annual cost exceeds US$12 billion. Optimal management should be based on knowledge of the most likely etiologic pathogens for each patient, based on an assessment of specific risk factors. It is also essential to assess severity of illness, to determine the appropriate site of care, and to order appropriate diagnostic testing. New developments in CAP management have focused on recognizing newly identified pathogens, such as methicillin-resistant Staphylococcus aureus and novel H1N1 influenza, understanding when to utilize new microbiological diagnostic techniques, and how to use biomarkers to direct the appropriate utilization of antibiotics and to define the duration of therapy. This paper reviews recent advances in our knowledge about the diagnosis and optimal management of CAP.

A community outbreak of Legionnaires’ disease from an industrial cooling tower: Assessment of clinical features and diagnostic procedures

An outbreak of Legionnaires' disease (LD) occurred in Lidköping, Sweden, in August 2004. A cooling tower was identified as the probable source of infection. During the outbreak period an unexpected 3-6-fold increase in pneumonia patients was noted at the local hospital. During 7 weeks LD was diagnosed in 15 patients by urinary antigen and/or sputum culture. Additionally, 15 LD patients were diagnosed later by serology. Patients with LD were generally younger, more healthy, and more often smokers compared to other pneumonia patients. On admittance they had more severe symptoms with high fever and raised CRP levels, and more often hyponatraemia, gastrointestinal and CNS symptoms. A causative agent besides Legionella was found in 2 patients only. A significant titre rise for Mycoplasma and/or Chlamydophila pneumoniae was found in 13 of 29 tested patients with confirmed LD. We conclude that the clinical diagnosis of LD is difficult and that available diagnostic methods detect only a minority of patients in the acute phase. Therefore in severe pneumonia, empirically targeted therapy should be instituted on clinical grounds irrespective of the results of diagnostic tests. The observation of increased antibody levels for M. and C. pneumoniae suggests an unspecific immune reaction and merits further study.

Culture versus polymerase chain reaction for the etiologic diagnosis of community-acquired pneumonia in antibiotic-pretreated pediatric patients

Tracheal aspirates were collected from 176 hospitalized antibiotic-pretreated children with community-acquired pneumonia. Haemophilus influenzae and Streptococcus pneumoniae were detected by both culture and target-enriched multiplex (TEM)-PCR whereas Mycoplasma pneumoniae and Chlamydia pneumoniae were detected by TEM-PCR only. TEM-PCR detected more S. pneumoniae (32 vs. 7) and H. influenzae (29 vs. 23) than did culture. TEM-PCR detected an additional 26 M. pneumoniae and 1 C. pneumoniae. TEM-PCR significantly enhances the pathogen-specific diagnosis of CAP in children.

Review: Novel targets in the management of pneumonia

Community-acquired pneumonia (CAP) is the leading cause of death from infectious diseases in the US. It accounts each year for 500,000 hospitalizations and 45,000 deaths and represents one of the most common causes of intensive care unit (ICU) admission. The mortality rate due to severe CAP has shown little improvement in the past three decades, remaining between 21% and 58% in patients admitted to the intensive care unit. Antimicrobial agents are the cornerstone of therapy against CAP, but there are some novel antibiotic and nonantibiotic therapies that have been recently tested that may potentially impact outcomes of patients with severe CAP. We will review the most recent data regarding novel therapies in patients with the highest risk of death such as those with severe CAP.

Pediatric respiratory infections by Mycoplasma pneumoniae

Mycoplasma pneumoniae is one of the most common agents of community-acquired pneumonia in children and young adults. Although M. pneumoniae is a small bacterium that can reproduce in an artificial culture medium and is known to be sensitive to certain antibiotics in vitro as well as in vivo, the immunopathogenesis of M. pneumoniae in the human host is not fully understood. The epidemiologic characteristics, including periodic epidemics, and some clinical characteristics of M. pneumoniae are similar to those observed in systemic viral infections. Many experimental and clinical studies have suggested that the pathogenesis of lung injuries in M. pneumoniae infection is associated with a cell-mediated immune reaction, including high responsiveness to corticosteroid therapy. This paper presents an overview of M. pneumoniae infections, with emphasis on epidemiology, pathogenesis and treatment.

Mycoplasma pneumoniae infection in a clinical setting

BACKGROUND

Mycoplasma pneumoniae infection predominantly affects the respiratory tract, although the other organs may also be involved. Previous studies compared the clinical features of patients with M. pneumonia pneumonia to other pathogens and these studies were predominantly adult case series rather than involving children. The objectives of the present study were to compare the clinical features, laboratory, and radiographic findings in children seropositive for M. pneumoniae infection with children tested for suspected M. pneumoniae infection who were seronegative.

METHODS

Using a retrospective review of children who had complement fixation test (CFT) performed for suspected M. pneumoniae infection, children were classified as seropositive if the acute phase serum titer was >or=64, or paired samples taken 2-4 weeks apart showed a fourfold or greater rise in serum titer. In contrast, a patient with an antibody titer <64 or with paired sera showing less than a fourfold rise in titer was considered seronegative.

RESULTS

One hundred and fifty-one children were included. Seventy-six children had serological evidence of M. pneumoniae infection and the remaining 75 were seronegative. Children with M. pneumoniae infection were more likely to have fever >6 days duration prior to admission, crackles on auscultation, radiographic consolidation and thrombocytosis at presentation. In addition, M. pneumoniae infection was associated with pneumonia whereas seronegative children were more likely to have upper respiratory tract infection or asthma.

CONCLUSIONS

Certain clinical parameters could assist in gauging the likelihood of M. pneumoniae infection in children, and thus direct whether antibiotic treatment is needed.

Atypical pneumonias: current clinical concepts focusing on Legionnaires' disease

PURPOSE OF REVIEW

This review provides clinicians with an overview of the clinical features of the atypical pneumonias. Atypical community-acquired pneumonia pathogens cause systemic infections with pneumonia. The key to the clinical diagnosis of atypical pneumonias depends on recognizing the characteristic pattern of extrapulmonary organ involvement different for each pathogen. As Legionella is likely to present as severe pneumonia and does not respond to beta-lactams, it is important to presumptively diagnose Legionnaires' disease clinically so that Legionella coverage is included in empiric therapy. This study reviews the clinical features and nonspecific laboratory markers of atypical pathogens, focusing on Legionnaires' disease.

RECENT FINDINGS

Case reports/outbreaks increase our understanding of Legionnaires' disease transmission. Both Mycoplasma pneumoniae and Chlamydophilia pneumoniae may cause asthma. Antimicrobial therapy of Chlamydophilia pneumoniae/Mycoplasma pneumoniae is important to decrease person-to-person spread and to decrease potential long-term sequelae.

SUMMARY

Atypical pulmonary pathogens cause systemic infections accompanied by a variety of characteristic extrapulmonary features. Clinically, it is possible to differentiate Legionnaires' disease from the other typical/atypical pneumonias. Rapid clinical diagnosis of atypical pathogens, particularly Legionnaires' disease, is important in selecting effective empiric therapy and prompting definitive laboratory testing.

Acute Chlamydia pneumoniae infections in asthmatic and non-asthmatic military conscripts during a non-epidemic period

Chlamydia pneumoniae respiratory tract infections were studied in 512 male military conscripts (123 asthmatic and 389 non-asthmatic) taking part in 180-day service between July 2004 and July 2005 in Kajaani, Finland. Respiratory tract infections requiring a medical consultation were analysed prospectively. At baseline, at end of service, and during each episode of respiratory infection, blood samples were obtained for measurement of C. pneumoniae antibodies. Data concerning the clinical features of each infection episode were collected. Serological evidence of acute C. pneumoniae infection was found in 34 of the 512 conscripts with antibody data available, including 9.8% of the asthmatic subjects and 5.7% of the non-asthmatic subjects (p 0.111). A serological diagnosis could be made for 25 clinical episodes in 24 conscripts. The spectrum of respiratory tract infections included 13 episodes of mild upper respiratory tract infection and seven episodes of sinusitis, with five episodes involving asthma exacerbation. Two of three pneumonias were primary infections. Primary infections were diagnosed in five subjects, and re-infection/reactivation in 19 subjects, with the latter comprising 12 non-asthmatic subjects and seven asthmatic subjects (p 0.180). Prolonged infections were present in six asthmatic subjects and one non-asthmatic subject (p 0.001). A wide variety of respiratory tract infections, ranging from common cold to pneumonia, were associated with serologically confirmed C. pneumoniae infections. Infections were often mild, with common cold and sinusitis being the most common manifestations. Acute, rapidly resolved C. pneumoniae infections were equally common among asthmatic subjects and non-asthmatic subjects, whereas prolonged infections were more common among subjects with asthma.

Chlamydophila pneumoniae induces a sustained airway hyperresponsiveness and inflammation in mice

Background

It has been reported that Chlamydophila (C.) pneumoniae is involved in the initiation and promotion of asthma and chronic obstructive pulmonary diseases (COPD). Surprisingly, the effect of C. pneumoniae on airway function has never been investigated.

Methods

In this study, mice were inoculated intranasally with C. pneumoniae (strain AR39) on day 0 and experiments were performed on day 2, 7, 14 and 21.

Results

We found that from day 7, C. pneumoniae infection causes both a sustained airway hyperresponsiveness and an inflammation. Interferon-γ (IFN-γ) and macrophage inflammatory chemokine-2 (MIP-2) levels in bronchoalveolar lavage (BAL)-fluid were increased on all experimental days with exception of day 7 where MIP-2 concentrations dropped to control levels. In contrast, tumor necrosis factor-α (TNF-α) levels were only increased on day 7. From day 7 to 21 epithelial damage and secretory cell hypertrophy was observed. It is suggested that, the inflammatory cells/mediators, the epithelial damage and secretory cell hypertrophy contribute to initiation of airway hyperresponsiveness.

Conclusion

Our study demonstrates for the first time that C. pneumoniae infection can modify bronchial responsiveness. This has clinical implications, since additional changes in airway responsiveness and inflammation-status induced by this bacterium may worsen and/or provoke breathlessness in asthma and COPD.

The other causes of 'atypical' pneumonia

Mycoplasma, Chlamydia and Legionella are the usual organisms considered to be the etiologic agents of 'atypical' pneumonia. Other microorganisms such as bacteria, viruses, parasites, fungi and mycobacteria can also present with atypical pneumonia manifestations. Outbreaks and isolated cases of respiratory viruses with atypical pneumonia presentations have been reported among immunocompetent and immunosuppressed patients. Severe infections due to these respiratory viruses alone or as a concomitant bacterial or viral infection have been observed. Additionally, in endemic areas, certain zoonotic infections may present as atypical pneumonia.

Mycoplasma pneumoniae pneumonia: differential diagnosis by computerized tomography

OBJECTIVE AND BACKGROUND

This study was designed to clarify chest computerized tomography (CT) findings of Mycoplasma pneumoniae pneumonia facilitating differential diagnosis from CAP (community acquired pneumonia) caused by other organisms.

METHODS

We retrospectively reviewed the CT findings of 36 patients (median age 33 years, 15 males, 21 females) with serologically proven M. pneumoniae pneumonia and 52 patients (median age 61 years, 37 males, 15 females) suffering from CAP with no serological evidence of M. pneumoniae infection. The CT images were analyzed by experienced pulmonologists.

RESULTS

The most common finding in the M. pneumoniae pneumonia group was bronchial wall thickening, when we compared it with the CAP group (p<0.0001, Fisher's exact probability test). In the CAP group infected with other organisms, dense consolidations with air bronchograms were more frequent than any other findings (p=0.0279, chi-square test).

CONCLUSIONS

The diagnosis of M. pneumoniae pneumonia would appear to be reliable when we found bronchial wall thickening in the chest CT images.

Simultaneous detection of pathogens in clinical samples from patients with community-acquired pneumonia by real-time PCR with pathogen-specific molecular beacon probes

In this study, real-time PCR with pathogen-specific molecular beacons (MB) and primers was evaluated for prediction of community-acquired pneumonia (CAP) causative agents, detecting six main CAP agents, Streptococcus pneumoniae, Haemophilus influenzae, Mycoplasma pneumoniae, Chlamydophila pneumoniae, Legionella pneumophila, and Streptococcus pyogenes, simultaneously. The PCR assay was evaluated for fresh clinical specimens from infants and children (n = 389) and from adults (n = 40). The MB probes and primers are both pathogen specific, namely, the lytA gene for S. pneumoniae, the mip gene for L. pneumophila, and 16S rRNA genes for the remaining four organisms. DNA extraction of clinical specimens was performed with a commercially available EXTRAGEN II kit, and amplification was performed with Stratagene Mx3000P. The limit of detection for these pathogens ranged from 2 copies to 18 copies. The whole process from DNA extraction to the analysis was finished in less than 2 h. The obtained sensitivity and specificity of this real-time PCR study relative to those of conventional cultures were as follows: 96.2% and 93.2% for S. pneumoniae, 95.8% and 95.4% for H. influenzae, 100% and 100% for S. pyogenes, and 100% and 95.4% for M. pneumoniae, respectively. The sensitivity and specificity for M. pneumoniae relative to those of a serologic assay were 90.2% and 97.9%, respectively. In six clinical samples of C. pneumoniae, the real-time PCR gave positive predictable values, and in those cases, elevation of the titer value was also observed. In conclusion, we demonstrated that a real-time PCR assay with pathogen-specific MB is useful in identifying CAP causative agents rapidly and in examining the clinical course of empirical chemotherapy in a timely manner, supporting conventional culture methods.

[Antibiotherapy for acute CAP in adults]

Community acquired pneumonia is one of the most frequent infections. With time, bacterial epidemiology and bacterial resistance evolve and new antibiotics become available. So an up-date on adequate antibiotic use is necessary. We reviewed the epidemiology of pneumonia and the evolution of bacterial resistance. We also collected data on new antibiotics which can be used for this infection such as levofloxacin, moxifloxacin, telithromycin, and pristinamycin. All these drugs are effective on bacteria involved in pneumonia. At this time, only few Streptococcus pneumoniae strains have developed resistance to these drugs. However, resistance to fluoroquinolones is not easily detected with common laboratory techniques. There is no effectiveness difference between the 2 new fluoroquinolones (levofloxacin, moxifloxacin) in clinical studies. However, in bacteriological and pharmacological studies, moxifloxacin seems to be more effective than levofloxacin (500 mg/day). For the treatment of pneumonia due to Legionella pneumophila, fluoroquinolones are now widely recommended. For Streptococcus pneumonia, amoxicillin remain the drug of choice, even for bacteria with a decreased susceptibility to penicillin. The importance of treating atypical pathogens remains to be documented.

Chlamydia pneumoniae infection after lung transplantation

BACKGROUND

Chlamydia pneumoniae is established as a common agent of acute respiratory tract infection and has been implicated in the pathogenesis of asthma and chronic obstructive pulmonary disease. Airway disease is a prominent cause of morbidity and mortality after lung transplantation. We investigated the role of C pneumoniae as a pulmonary pathogen after lung transplantation.

METHODS

Eighty lung transplant recipients underwent 232 bronchoscopies with bronchoalveolar lavage with or without transbronchial lung biopsy during 1 year for surveillance of rejection and infection, or where clinically indicated.

RESULTS

C pneumoniae was detected using nested polymerase chain reaction in 9 of 36 (25%) recipients studied within 30 days of lung transplantation, 3 of whom remained positive on repeat lavage and died from airway disease in the first year post-operatively. By comparison, all 27 recipients with negative lavage survived >1 year. Lavage was positive for C pneumoniae in 18 of 71 (25%) recipients studied >30 days after lung transplantation, 5 of whom had pneumonia and 8 of whom had bronchiolitis obliterans syndrome. Eleven also had acute pulmonary allograft rejection.

CONCLUSIONS

Persistent infection with C pneumoniae (whether donor-derived, de novo or re-activated) appears deleterious to pulmonary allograft function and is associated with early mortality, rejection and bronchiolitis obliterans syndrome after lung transplantation. A trial of empiric antibiotic therapy for C pneumoniae may therefore be warranted in the attempt to prevent progressive inflammatory airway disease.

Role of Mycoplasma pneumoniae and Chlamydia pneumoniae in children with community-acquired pneumonia in Istanbul, Turkey

BACKGROUND

To investigate the role of Mycoplasma pneumoniae and Chlamydia pneumoniae infection in pediatric pneumonia, in Istanbul, Turkey, we conducted a prospective study covering all the children between 2 months and 15 years hospitalized for community-acquired pneumonia.

METHODS

A total of 140 children (85 males, median age 2.5 years) with community-acquired pneumonia were enrolled. Acute and convalescent sera were tested for IgM and IgG antibodies to M. pneumoniae (enzyme-linked immunosorbent assay, Serion ELISA classic) and for IgM and IgG antibodies to C. pneumoniae (microimmunofluorescence, Savyon, Israel).

RESULTS

Mycoplasma pneumoniae infection was diagnosed in 38 patients (27%) and C. pneumoniae infection in 7 (5%). In 2 children M. pneumoniae and C. pneumoniae co infection was observed. The average age of the M. pneumoniae cases was 5.3 years and that of the C. pneumoniae was 1.5 years. The average age of pneumonia cases caused by other pathogens was 3.4 years (p<0.05). No significant difference was observed in clinical onset, signs, symptoms and laboratory parameters in children with M. pneumoniae and C. pneumoniae infection and in those without M. pneumoniae and C. pneumoniae infection.

CONCLUSIONS

The results of this study suggest a remarkable role for M. pneumoniae and C. pneumoniae in childhood community-acquired pneumonia, and the knowledge of the true prevalence of these two types of infections discovered in the community might lead to modifications in the present empirical treatment of bacterial pneumonia.

The atypical pneumonias: clinical diagnosis and importance

The most common atypical pneumonias are caused by three zoonotic pathogens, Chlamydia psittaci (psittacosis), Francisella tularensis (tularemia), and Coxiella burnetii (Q fever), and three nonzoonotic pathogens, Chlamydia pneumoniae, Mycoplasma pneumoniae, and Legionella. These atypical agents, unlike the typical pathogens, often cause extrapulmonary manifestations. Atypical CAPs are systemic infectious diseases with a pulmonary component and may be differentiated clinically from typical CAPs by the pattern of extrapulmonary organ involvement which is characteristic for each atypical CAP. Zoonotic pneumonias may be eliminated from diagnostic consideration with a negative contact history. The commonest clinical problem is to differentiate legionnaire's disease from typical CAP as well as from C. pneumoniae or M. pneumonia infection. Legionella is the most important atypical pathogen in terms of severity. It may be clinically differentiated from typical CAP and other atypical pathogens by the use of a weighted point system of syndromic diagnosis based on the characteristic pattern of extrapulmonary features. Because legionnaire's disease often presents as severe CAP, a presumptive diagnosis of Legionella should prompt specific testing and empirical anti-Legionella therapy such as the Winthrop-University Hospital Infectious Disease Division's weighted point score system. Most atypical pathogens are difficult or dangerous to isolate and a definitive laboratory diagnosis is usually based on indirect, i.e., direct flourescent antibody (DFA), indirect flourescent antibody (IFA). Atypical CAP is virtually always monomicrobial; increased IFA IgG tests indicate past exposure and not concurrent infection. Anti-Legionella antibiotics include macrolides, doxycycline, rifampin, quinolones, and telithromycin. The drugs with the highest level of anti-Legionella activity are quinolones and telithromycin. Therapy is usually continued for 2 weeks if potent anti-Legionella drugs are used. In adults, M. pneumoniae and C. pneumoniae may exacerbate or cause asthma. The importance of the atypical pneumonias is not related to their frequency (approximately 15% of CAPs), but to difficulties in their diagnosis, and their nonresponsiveness to beta-lactam therapy. Because of the potential role of C. pneumoniae in coronary artery disease and multiple sclerosis (MS), and the role of M. pneumoniae and C. pneumoniae in causing or exacerbating asthma, atypical CAPs also have public health importance.

Clinical experience in the management of community-acquired pneumonia: lessons from the use of fluoroquinolones

Community-acquired pneumonia (CAP) remains a major cause of morbidity and mortality worldwide. The treatment of CAP has been complicated by several factors, including the expanding spectrum of causative organisms and the rising prevalence of antibiotic resistance among respiratory pathogens. Initial antimicrobial treatment for patients with CAP is usually selected empirically and should provide appropriate coverage against the most common causative organisms, including resistant strains. Respiratory fluoroquinolones, such as levofloxacin, are the only antimicrobials that are highly active against the pathogens most frequently implicated in CAP, including macrolide-resistant and penicillin-resistant pneumococci, Haemophilus influenzae, Legionella spp., and atypical agents. This paper reviews recent studies involving adult patients with CAP that suggest that levofloxacin, as compared with other conventional antibiotic treatments, may be associated with better clinical outcomes.

Chlamydia pneumoniae and Mycoplasma pneumoniae pneumonia: comparison of clinical, epidemiological characteristics and laboratory profiles

The purpose of our retrospective 3-year study was to analyse and compare clinical and epidemiological characteristics in hospitalized patients older than 6 years with community-acquired pneumonia (CAP) caused by Chlamydia pneumoniae (87 patients) and Mycoplasma pneumoniae (147 patients). C. pneumoniae and M. pneumoniae infection was confirmed by serology. C. pneumoniae patients were older (42.12 vs. 24.64 years), and were less likely to have a cough, rhinitis, and hoarseness (P<0.001). C. pneumoniae patients had higher levels of C-reactive protein (CRP), and aspartate aminotransferase (AST) than M. pneumoniae patients (P<0.001). Pleural effusion was recorded more frequently in patients with M. pneumoniae (8.84 vs. 3.37%). There were no characteristic epidemiological and clinical findings that would distinguish CAP caused by M. pneumoniae from C. pneumoniae. However, some factors are indicative for C. pneumoniae such as older age, lack of cough, rhinitis, hoarseness, and higher value of CRP, and AST.

Reactive species mediate inhibition of alveolar type II sodium transport during mycoplasma infection

RATIONALE

Mycoplasma pneumoniae is a significant cause of pneumonia in humans.

OBJECTIVES

To determine the impact of mycoplasma infection and the host inflammatory response on alveolar type II (ATII) cell ion transport in vivo and in vitro.

METHODS

Mice were infected with M. pulmonis for measurements of alveolar fluid clearance (AFC) in vivo and isolation of ATII cells. ATII cells were infected in vivo for determination of epithelial Na+ channel (ENaC) total and cell surface protein levels by biotinylation and Western blot and in vitro for whole cell patch clamp recording and measurement of nitric oxide (NO) production by chemiluminescence.

RESULTS

Mycoplasma infection significantly inhibited AFC at 24 h and total and amiloride-sensitive AFC by 48 h postinfection (pi). In contrast, infected myeloperoxidase-deficient mice had similar basal and amiloride-sensitive AFC values to uninfected control mice at 48 h pi. Addition of forskolin restored total and amiloride-sensitive AFC to control values at 48 h pi. ATII cells isolated from infected mice demonstrated normal alpha, beta, and gamma ENaC total protein levels; however, infected whole-lung cell-surface levels of gamma ENaC were significantly decreased. Patch-clamp recordings demonstrated a significant decrease in total and amiloride-sensitive Na+ currents at 24 h pi. ATII cells demonstrated a significant increase in the production of NO at 24 h pi and inhibition of NO by ATII cells before infection reversed the decrease in total Na+ currents.

CONCLUSIONS

These data indicate that mycoplasma infection results in decreased AFC and functional ENaC via the production of reactive oxygen nitrogen intermediates.

Chlamydia pneumoniae Pneumonia and Mycoplasma pneumoniae Pneumonia

The objective of this study was to identify the clinical and pulmonary CT findings associated with Chlamydia pneumoniae pneumonia and to compare them with those of Mycoplasma pneumoniae pneumonia. The clinical features and CT scans of 40 patients with C. pneumoniae pneumonia and 42 patients with M. pneumoniae pneumonia were retrospectively reviewed. There were no significant differences between the two etiologic agents with regard to clinical signs. Chest CT findings in patients with C. pneumoniae pneumonia consisted mainly of ground-glass attenuation (n = 38) and acinar patterns (n = 28). Acinar patterns and pleural effusions (n = 12) were observed significantly more frequently than in patients with M. pneumoniae pneumonia (P < 0.0001, P < 0.039, respectively). CT findings of centrilobular nodules and bronchial wall thickening were significantly less common than in the M. pneumoniae pneumonia patients (P < 0.0001, P < 0.0001, respectively). The CT finding of acinar patterns, although nonspecific, can be considered suggestive of C. pneumoniae pneumonia.

Self-limiting pneumonia due to Chlamydia pneumoniae

A case of self-limiting pneumonia due to Chlamydia pneumoniae is described. A 39-year-old male visited our hospital complaining of a persistent cough. No antibiotics were administered to this patient because of the absence of fever and a mild positive inflammatory response, but an infiltrate on a chest radiograph improved. Finally, a diagnosis of C. pneumoniae pneumonia was made by seroconversion of the C. pneumoniae-specific antibody and detection of the C. pneumoniae gene in bronchoalveolar lavage fluid. Self-limiting C. pneumoniae pneumonia is rarely encountered, although self-limiting upper respiratory tract infections due to C. pneumoniae are common. Thus, most self-limiting C. pneumoniae pneumonia may be missed when symptoms are minimal.

Single-run, parallel detection of DNA from three pneumonia-producing bacteria by real-time polymerase chain reaction

A molecular assay for parallel detection of three bacteria, Chlamydia (C.) pneumoniae, Legionella (L.) spp., and Mycoplasma (M.) pneumoniae, in clinical specimens by a set of real-time polymerase chain reactions (PCRs) in a single run was evaluated. Bacterial DNAs were extracted by an automated DNA extraction protocol on the MagNA Pure LC System. Amplification and detection were done by real-time PCR on the LightCycler (LC) instrument. For amplification, specific oligonucleotides derived from the 16s rRNA genes of C. pneumoniae, L. spp., and M. pneumoniae were used. The three assays were complemented with an internal control (IC), a specially designed DNA fragment which contains the specific primer binding sites for the three PCRs. The IC was added to the samples, co-extracted, and co-amplified. Primers and hybridization probes were designed to suit one LC PCR program. LC PCRs were established, detection limits were determined, and clinical samples were tested. The detection limits were found between 5.0 and 0.5 IFU/CFU per PCR reaction for each of the bacteria. A total number of 100 clinical specimens were tested for validation of the molecular assay. Tested samples included 63 bronchoalveolar lavages (BALs) and 37 induced sputa specimens. The internal control was detected in all negative and low-positive samples; no inhibition was found throughout the whole study. Additionally, samples underwent testing by culture for L. spp., and M. pneumoniae; for C. pneumoniae, the serological microimmunofluorescence (MIF) test was used. In conclusion, the developed set of LC PCR assays permits parallel detection of C. pneumoniae, L. spp., and M. pneumoniae in a single LC run. This molecular assay may lead to accurate and early diagnosis of pneumonia produced by these three types of bacteria. The assay proved to be suitable for the high-throughput routine diagnostic laboratory.

Etiology of community-acquired pneumonia

Community-acquired pneumonia (CAP) is a serious lower respiratory tract infection associated with significant morbidity and mortality that is characterized by disputes over diagnostic evaluations and therapeutic decisions. With the widespread use of broad-spectrum antimicrobial agents and the increasing number of immunocompromised hosts, the etiology and the drug resistance patterns of pathogens responsible for CAP have changed. Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis remain the leading causes of CAP in immunocompetent patients. Opportunistic infections with organisms such as Pneumocystis jiroveci and Mycobacterium tuberculosis and other opportunistic fungal pneumonias should also be considered in the differential diagnosis of CAP in immunocompromised patients. This article examines the current peer-reviewed literature on etiology, risk factors, and outcomes of patients with CAP.

An Asian study on the prevalence of atypical respiratory pathogens in community-acquired pneumonia

BACKGROUND

In many parts of Asia, the inaccessibility and high cost of diagnostic tests have hampered the study of community-acquired pneumonia (CAP) caused by atypical respiratory pathogens.

OBJECTIVE

This surveillance study examined the frequency of infection with Mycoplasma pneumoniae, Chlamydophila pneumoniae, and Legionella pneumophila in 1756 patients presenting with signs and symptoms of CAP at 12 medical centres in Asia, using standardised laboratory techniques and interpretation criteria in all participating centres.

METHODS

Diagnosis of current infection was based on significant changes in antibody titer or persisting high antibody titers, together with the presence of bacterial DNA in respiratory secretions, in the case of M. pneumoniae and C. pneumoniae infections, or bacterial antigen in urine, in the case of L. pneumophila serogroup 1 infection.

RESULTS

Using these criteria, results from 1374 patients with paired sera showed that, overall, 23.5% of CAP cases were associated with infection with atypical respiratory pathogens, with M. pneumoniae, C. pneumoniae, and L. pneumophila being found in 12.2%, 4.7%, and 6.6% of cases, respectively. Persisting high antibody titers indicative of past exposure to M. pneumoniae, C. pneumoniae, and L. pneumophila were seen in 10.2%, 4.8%, and 18.9% of patients, respectively.

CONCLUSION

These data reflect the overall high prevalence of these atypical pathogens among Asian patients with CAP.

Role of beta-lactam agents in the treatment of community-acquired pneumonia

Community-acquired pneumonia (CAP) is a common illness associated with high rates of morbidity and mortality worldwide. The beta-lactam antibacterial agents have been the mainstay of therapy for CAP for over four decades and remain as first-line therapy. However, the impact of the substantial prevalence of resistance seen among the common respiratory pathogens, particularly penicillin and macrolide resistance among Streptococcus pneumoniae, is now an area for concern. CAP treatment guidelines often recommend the use of a macrolide or fluoroquinolone in conjunction with, or as an alternative to, beta-lactam agents, but whether this is necessary is uncertain. This review outlines the historical use of beta-lactam antibacterial agents in the treatment of CAP along with their ongoing therapeutic utility.

Re-evaluation of the therapy of severe pneumonia caused by Streptococcus pneumoniae

Pneumonia caused by Streptococcus pneumoniae is the most deadly form of community-acquired pneumonia. The death rate of bacteremic pneumococcal pneumonia has remained constant over the past 50 years. Several retrospective reviews of bacteremic pneumococcal pneumonia suggest that dual therapy with a beta-lactam and a macrolide antimicrobial agent is associated with a lower case fatality rate than therapy with a beta-lactam alone. These studies are reviewed, potential mechanisms are suggested, and future studies are discussed.

Chlamydia pneumoniae, Mycoplasma pneumoniae, and Legionella pneumophila in elderly patients with stroke (C-PEPS, M-PEPS, L-PEPS): a case-control study on the infectious burden of atypical respiratory pathogens in elderly patients with acute cerebrovascular disease

BACKGROUND AND PURPOSE

Multiple studies have suggested an association between Chlamydia pneumoniae and Mycoplasma pneumoniae infection and cardiovascular disease. We investigated whether the risk of cerebrovascular disease is associated with Legionella pneumophila infection and the aggregate number/infectious burden of these atypical respiratory pathogens.

METHODS

One hundred patients aged >65 years admitted with acute stroke or transient ischemic attack (TIA) and 87 control patients admitted concurrently with acute noncardiopulmonary, noninfective conditions were recruited prospectively. Using enzyme-linked immunosorbent assay (ELISA) kits, we previously reported the seroprevalences of C pneumoniae and M pneumoniae in these patients. We have now determined the seroprevalences of L pneumophila IgG and IgM in this cohort of patients using ELISA.

RESULTS

The seroprevalences of L pneumophila IgG and IgM were 29% (n=91) and 12% (n=81) in the stroke/TIA group and 22% (n=86) and 10% (n=72) in the controls, respectively. Using logistic regression to adjust for age, sex, hypertension, smoking, diabetes, ischemic heart disease, and ischemic ECG, the odds ratios for stroke/TIA in relation to L pneumophila IgG and IgM were 1.52 (95% CI, 0.70 to 3.28; P=0.29) and 1.49 (95% CI, 0.45 to 4.90; P=0.51), respectively. The odds ratios in relation to IgG seropositivity for 1, 2, or 3 atypical respiratory pathogens after adjustment were 3.89 (95% CI, 1.13 to 13.33), 2.00 (95% CI, 0.64 to 6.21), and 6.67 (95% CI, 1.22 to 37.04), respectively (P=0.06).

CONCLUSIONS

L pneumophila seropositivity is not significantly associated with stroke/TIA. However, the risk of stroke/TIA appears to be associated with the aggregate number of chronic infectious burden of atypical respiratory pathogens such as C pneumoniae, M pneumoniae, and L pneumophila.

Diagnosis of infection in sepsis: An evidence-based review

OBJECTIVE

In 2003, critical care and infectious disease experts representing 11 international organizations developed management guidelines for the diagnosis of infection in sepsis that would be of practical use for the bedside clinician, under the auspices of the Surviving Sepsis Campaign, an international effort to increase awareness and improve outcome in severe sepsis.

DESIGN

The process included a modified Delphi method, a consensus conference, several subsequent smaller meetings of subgroups and key individuals, teleconferences, and electronic-based discussion among subgroups and among the entire committee.

METHODS

The modified Delphi methodology used for grading recommendations built on a 2001 publication sponsored by the International Sepsis Forum. We undertook a systematic review of the literature graded along five levels to create recommendation grades from A to E, with A being the highest grade. Pediatric considerations to contrast adult and pediatric management are in the article by Parker et al. on p. S591.

CONCLUSIONS

Obtaining a precise bacteriological diagnosis before starting antibiotic therapy is, when possible, of paramount importance for the success of therapeutic strategy during sepsis. Two to three blood cultures should be performed, preferably from a peripheral vein, without interval between samples to avoid delaying therapy. A quantitative approach is preferred in most cases when possible, in particular for catheter-related infections and ventilator-associated pneumonia. Diagnosing community-acquired pneumonia is complex, and a diagnostic algorithm is proposed. Appropriate samples are indicated during soft tissue and intraabdominal infections, but cultures obtained through the drains are discouraged.

Efficacy and safety of sequential moxifloxacin for treatment of community-acquired pneumonia associated with atypical pathogens

In two prospective, randomized studies intravenous (IV)/oral (PO) moxifloxacin (400 mg q.i.d.) was compared to IV/PO antimicrobial comparator agents for the treatment of hospitalized patients with community-acquired pneumonia. Reported here are the pooled data for the sub-population with atypical pathogens. Of 101 intent-to-treat patients with atypical pathogens, a total of 39 moxifloxacin-treated and 47 comparator-treated subjects were microbiologically valid and included in the analysis. Clinical and bacteriological success rates were 95% for the moxifloxacin-treated and 94% for the comparator-treated subjects at the test-of-cure visit. The results indicate IV/PO moxifloxacin (400 mg q.i.d.) is an effective monotherapy for patients with CAP due to atypical pathogens.

Aetiology of acute pharyngitis: the role of atypical bacteria

In order to establish the role of atypical bacteria and compare characteristics of different infectious agents in acute pharyngitis, 127 patients with acute pharyngitis (66 males; median age, 5.33 years; range, 6 months to 14 years) and 130 healthy subjects of similar sex and age were studied. Serology with paired samples and PCR on nasopharyngeal aspirates and throat cultures were used to identify bacteria and viruses. Viruses were identified in 43 patients (33.8%) and five controls (3.8%; P < 0.0001), potential bacterial pathogens in 34 patients (26.8%) and 26 controls (20%; P = 0.256) and mixed viral/bacterial pathogens in 26 patients (20.5%) and none of the controls (P < 0.0001). The main aetiological agents were adenovirus, respiratory syncytial virus (RSV), Mycoplasma pneumoniae, Streptococcus pyogenes and Chlamydia pneumoniae. M. pneumoniae was the agent found most frequently as a single pathogen. A history of recurrent pharyngitis, having older siblings and a negative outcome were significantly more common among patients with acute M. pneumoniae infection than among those with infections due to other pathogens or healthy controls. This study demonstrates that: (i) adenovirus and RSV have a prominent role in acute pharyngitis; (ii) S. pyogenes is found frequently, but it is not possible to distinguish simple carriers from patients with a true infection; (iii) M. pneumoniae appears to be able to cause acute pharyngitis per se; and (iv) C. pneumoniae seems to be mainly a co-pathogen. To avoid the risk of an incorrect therapeutic approach, simple laboratory investigations that allow rapid identification of M. pneumoniae infections are urgently needed.

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.