肺炎衣原体的套式（Nested）PCR检测及其临床意义

肺炎衣原体（C_(pn)）可致上、下呼吸道的炎症，并且是非典型性肺炎综合征（APS）的主要病原体之一。C_(pn)已占肺炎病原体的第三或第四位。近年的深入研究表明，C_(pn)还能引起呼吸道之外的脏器炎症。由于C_(pn)为专性细胞内寄生菌，因此培养困难。目前国内尚缺乏C_(pn)感染诊断方法。本文介绍一种灵敏、特异、简便的C_(pn)套式PCR检测方法。应用本法检测55例呼吸道感染者之咽拭子，共检出9例阳性（阳性率16．2％）。表明C_(pn)的呼吸道感染在我国并不少见。C_(pn)套式PCR方法的建立，对于我国的C_(pn)人群感染率和C_(pn)感染的分子流行学研究有着极其重要的意义。     

Isolation of Chlamydia pneumoniae from the lungs of patients infected with the human immunodeficiency virus.

Chlamydia pneumoniae is being recognized as a common cause of respiratory tract infections. Bronchoalveolar lavage specimens from human immunodeficiency virus-infected patients were examined by culture for this pathogen. Of 50 specimens examined, 5 (10%) were positive for C. pneumoniae. Four of these (80%) were also positive for other pathogens frequently implicated as causes of respiratory disease in this patient population. C. pneumoniae may frequently inhabit the respiratory tracts of human immunodeficiency virus-infected individuals.     

Chlamydial infections of the heart

Chlamydiae are common human pathogens, causing a broad spectrum of infectious diseases. Chlamydial infections involving the heart have been described in numerous previous reports. These organisms are documented to cause endocarditis, myocarditis and pericarditis. Furthermore,Chlamydia pneumoniae, the recently discovered respiratory pathogen, has also been implicated in coronary artery disease. For the first time the literature on involvement of the heart in chlamydial infections is reviewed. Information on the discovery ofChlamydia species is also included and the problem of the species determination ofChlamydia in interpretation of the older literature is mentioned.     

Microbiological profile of telithromycin, the first ketolide antimicrobial

Telithromycin, the first of the ketolide antimicrobials, has been specifically designed to provide potent activity against common and atypical/intracellular or cell-associated respiratory pathogens, including those that are resistant to β-lactams and/or macrolide–lincosamide–streptogramin_B (MLS_B) antimicrobials. Against Gram-positive cocci, telithromycin possesses more potent activity in vitro and in vivo than the macrolides clarithromycin and azithromycin. It retains its activity against erm -(MLS_B) or mef -mediated macrolide-resistant Streptococcus pneumoniae and Streptococcus pyogenes and against Staphylococcus aureus resistant to macrolides through inducible MLS_B mechanisms. Telithromycin also possesses high activity against the Gram-negative pathogens Haemophilus influenzae and Moraxella catarrhalis , regardless of β-lactamase production. In vitro , it shows similar activity to azithromycin against H. influenzae , while in vivo its activity against H. influenzae is higher than that of azithromycin. Telithromycin's spectrum of activity also extends to the atypical, intracellular and cell-associated pathogens Legionella pneumophila , Mycoplasma pneumoniae and Chlamydia pneumoniae . In vitro , telithromycin does not induce MLS_B resistance and it shows low potential to select for resistance or cross-resistance to other antimicrobials. These characteristics indicate that telithromycin will have an important clinical role in the empirical treatment of community-acquired respiratory tract infections.     

Is There a Role for Antibiotics in the Treatment of Asthma?

Emerging evidence suggests an association between some asthma and pulmonary infection by the atypical organisms Chlamydia pneumoniae and Mycoplasma pneumoniae, but a causal role for infection remains unproven and controversial. Most acute exacerbations of asthma are triggered by acute infections that are due to viral respiratory pathogens, not to bacteria or atypical organisms. Administration of antibiotics for acute exacerbations of asthma has been shown to be ineffective. Most evidence linking atypical infections to asthma is consistent with a promoting role for chronic infection in producing persistent asthma symptoms. Preliminary studies suggest that prolonged (>/=6 weeks) administration of doxycycline or macrolides may eradicate C. pneumoniae from respiratory secretions and improve long term, not acute, asthma symptoms. Randomised, controlled trials are currently under way to investigate the effectiveness of these prolonged courses of macrolides and azalides (roxithromycin, clarithromycin and azithromycin) in adults with stable persistent asthma. Traditional courses (7 to 10 days) of any antibiotic are incapable of eradicating chronic C. pneumoniae or M. pneumoniae infection; furthermore, beta-lactam and sulphonamide-based antibiotics that are commonly prescribed in acute respiratory syndromes are ineffective against these atypical organisms. Unless the goal is to treat documented sinusitis associated with asthma, it is inappropriate to prescribe traditional courses of any antibiotic for acute asthma exacerbations; whether longer courses of antibiotics should be prescribed to eradicate chronic atypical infections and decrease persistent asthma severity remains to be established.     

Diagnosis of acute respiratory tract infections: serology and new method

No test is available that can identify all potential pathogens in acute respiratory tract infections. Each diagnostic test is associated with limitations with respect to sensitivity and/or specificity and/or speed, and thus a combination of tests has to be used. Even so, no etiologic agent is found in 30-60% of cases. The following methods are recommended for use in the routine laboratory for the diagnosis of infections: (1) Legionella — direct immunofluorescence test, culture, serology and antigen detection (available only in specialized laboratories); (2) Chlamydia pneumoniae — microimmunofluorescence test, complement fixation, but not direct antigen detection by immunofluorescence; (3) Mycoplasma pneumoniae — complement fixation and/or particle agglutination or other evaluated methods; (4) Coxiella burnetti — immunofluorescence test (IgG and IgM) and complement fixation; (5) viruses — complement fixation or other similar test (ELISAs often lack adequate evaluation). Culture for Chlamydia, Mycoplasma pneumoniae, Coxiella burnetti and viruses should only be performed by very experienced laboratories. Most procedures deliver results only retrospectively or too late. The most promising diagnostic tools for the future are nucleic acid amplification techniques (NAT) or PCR, which could solve many of the problems connected with conventional techniques, but there are enormous contamination problems. Further research and worldwide aid in the development of standardized NAT, especially by industrial companies, is urgently encouraged to improve the laboratory diagnosis of these pneumonias.     

Asymptomatic respiratory tract infection with Chlamydia pneumoniae TWAR.

Chlamydia pneumoniae is a newly recognized organism associated with respiratory tract infections. Asymptomatic infection with C. pneumoniae, although it has been suggested to occur, has not been previously documented. We describe two asymptomatic individuals infected with this organism; these infections demonstrate that C. pneumoniae is able to establish a subclinical infection.     

Introduction: Evolving needs in respiratory tract infections

Two issues that have become clinically relevant to the treatment of pneumonia over the past few years are the development of antibiotic resistance among respiratory pathogens and the increasing importance of the atypical respiratory pathogens— Mycoplasma pneumoniae, Chlamydia pneumoniae and Legionella spp.
Resistance has become an important issue in Streptococcus pneumoniae , methicillin-resistant Staphylococcus aureus and Gram-negative rods. The ways by which bacteria become resistant to antibiotics include production of antibiotic-modifying enzymes, reduced access to target sites, efflux of antibiotic, change in the bacterial target site and the bypassing of inhibited pathways. In Streptococcus pneumoniae that are penicillin resistant, the mechanism is through alteration of the target site for penicillins (penicillin-binding proteins) and this may also confer resistance to some cephalosporins. Multidrug resistance has also been reported in some strains of pneumococci. Of particular concern is resistance to macrolides mediated by the ermAM gene, which also confers resistance to lincosamides and streptogramin-B drugs. In Staphylococcus aureus , resistance to virtually all β-lactam drugs is mediated by acquisition of the mecA gene, which codes for the drug-resistant β-lactam target PBP2a.
Antimicrobials are now needed that have enhanced activity against aerobic Gram-negative rods, atypical respiratory pathogens and Gram-positive cocci.     

Outbreak and persistence of Chlamydia pneumoniae infection in an Italian family

We describe an outbreak of familial infection of Chlamydia pneumoniae, an etiological agent for respiratory tract infections. In a family member detection of C. pneumoniae on a pharyngeal swab by polymerase chain reaction was positive until four months after the onset of symptoms, despite a course of antibiotics known to be effective against Chlamydia species     

Chlamydia pneumoniae arthritis in a patient with common variable immunodeficiency.

BACKGROUND: Arthritis is an important and sometimes life-threatening complication in patients with common variable immunodeficiency (CVID). OBJECTIVE: To describe a patient with CVID and arthritis due to Chlamydia pneumoniae, which is usually regarded as a respiratory tract pathogen and has not previously been detected in the synovial fluid by cell culture technique. METHODS: Routine bacteriologic, virologic, mycologic, and tuberculosis cultures were performed. The patient's synovial fluid was examined for fastidious organisms that might be causative pathogens of arthritis, such as chlamydiae, and special cell culture methods were used. Serologic tests were performed to determine viral and bacteriologic etiology. RESULTS: The patient had a history of recurrent respiratory tract infections, and the latest exacerbation was followed by arthritis. Cytologic examination of the fluid yielded abundant lymphocytes. Chlamydia pneumoniae was detected in synovial fluid specimens by cell culture technique. Her nasopharyngeal swab and sputum culture specimens were also positive for this pathogen. She was diagnosed as having arthritis caused by C pneumoniae and was given antibiotherapy. CONCLUSION: Chlamydia pneumoniae should be kept in mind as a causative pathogen in patients with CVID and arthritis, especially when effusion fluid is full of lymphocytes rather than polymorphonuclear cells and no organism is grown on routine cultures.     

Bacteriological activity of trovafloxacin, a new quinolone, against respiratory tract pathogens

The use of established fluoroquinolones, such as ciprofloxacin and ofloxacin, as empirical therapy for the treatment of moderate-to-severe respiratory tract infections is limited by their poor activity against gram-positive and atypical pathogens. Data from in vitro susceptibility studies and in vivo animal protection models suggest that the new fluoroquinolone, trovafloxacin, compared with ciprofloxacin and ofloxacin offers equivalent activity against gram-negative pathogens and improved activity against gram-positive pathogens. In particular, susceptibility data indicate that trovafloxacin is at least 16-fold more potent than either ciprofloxacin or ofloxacin against penicillin-susceptible and penicillin-resistant strains ofStreptococcus pneumoniae. Other susceptible pathogens includeStreptococcus pyogenes, vancomycin-susceptibleEnterococcus faecalis and the atypical respiratory pathogensLegionella pneumophila, Mycoplasma pneumoniae andChlamydia pneumoniae. In vivo studies involving models of protection against acute systemic infection and pneumococcal pneumonia in mice, and Legionnaires' disease in guinea pigs, indicate that the antibacterial spectrum observed for trovafloxacin in vitro extends to the in vivo setting. Together, these findings suggest that trovafloxacin may offer clinical efficacy against respiratory pathogens superior to that of ciprofloxacin and of ofloxacin, and may find a useful role as empiric therapy in both the community and hospital setting.     

Clinical features of Chlamydia pneumoniae acute respiratory infection

Chlamydia pneumoniae is a worldwide respiratory pathogen involved in 6–20% of community-acquired pneumonias and in about 5% of acute exacerbations of chronic bronchitis. Preliminary data also indicate a possible association between Chlamydia pneumoniae infection and asthma. Further studies are needed to elucidate whether Chlamydia pneumoniae is merely a precipitant of asthma symptoms or is actually one of the causes of asthma.     

Detection of respiratory bacterial pathogens causing atypical pneumonia by multiplex Lightmix® RT-PCR

Pneumonia is a severe infectious disease. In addition to common viruses and bacterial pathogens (e.g. Streptococcus pneumoniae), fastidious respiratory pathogens like Chlamydia pneumoniae, Mycoplasma pneumoniae and Legionella spp. can cause severe atypical pneumonia. They do not respond to penicillin derivatives, which may cause failure of antibiotic empirical therapy. The same applies for infections with B. pertussis and B. parapertussis, the cause of pertussis disease, that may present atypically and need to be treated with macrolides. Moreover, these fastidious bacteria are difficult to identify by culture or serology, and therefore often remain undetected. Thus, rapid and accurate identification of bacterial pathogens causing atypical pneumonia is crucial. We performed a retrospective method evaluation study to evaluate the diagnostic performance of the new, commercially available Lightmix^® multiplex RT-PCR assay that detects these fastidious bacterial pathogens causing atypical pneumonia. In this retrospective study, 368 clinical respiratory specimens, obtained from patients suffering from atypical pneumonia that have been tested negative for the presence of common agents of pneumonia by culture and viral PCR, were investigated. These clinical specimens have been previously characterized by singleplex RT-PCR assays in our diagnostic laboratory and were used to evaluate the diagnostic performance of the respiratory multiplex Lightmix^® RT-PCR. The multiplex RT-PCR displayed a limit of detection between 5 and 10 DNA copies for different in-panel organisms and showed identical performance characteristics with respect to specificity and sensitivity as in-house singleplex RT-PCRs for pathogen detection. The Lightmix^® multiplex RT-PCR assay represents a low-cost, time-saving and accurate diagnostic tool with high throughput potential. The time-to-result using an automated DNA extraction device for respiratory specimens followed by multiplex RT-PCR detection was below 4 h, which is expected to significantly improve diagnostics for atypical pneumonia-associated bacterial pathogens.     

Molecular genetic methods in the diagnosis of lower respiratory tract infections

Molecular diagnostic techniques, such as PCR, have become useful tools for the rapid etiological diagnosis of lower respiratory tract infections. Nucleic acid amplification tests (NAATs) have been evaluated for detecting most respiratory pathogens, and commercial assays are available for some pathogens. However, standardized protocols are needed before these assays are introduced into routine diagnostic use. For pneumonia, NAATs offer advantages over conventional tests for the detection of Mycoplasma pneumoniae, Legionella spp. and Chlamydia pneumoniae. For pneumococcal pneumonia in adults, PCR adds little to existing diagnostic tests, and is unable to distinguish pneumococcal colonization from infection when testing respiratory samples. Although less sensitive than culture-based methods, several commercial molecular diagnostic assays have been developed for tuberculosis and are useful rapid tests for selected patients. PCR can now be considered the rapid diagnostic test of choice for pertussis and some respiratory virus infections. Further work is required to better characterize the role of molecular diagnostic tests for diagnosing lower respiratory tract infections, and to develop standard assays that can be readily adopted by routine diagnostic laboratories.     

Choice of antimicrobial drug for infections caused by Chlamydia trachomatis and Chlamydophila pneumoniae

Chlamydia (C.) trachomatis is the most common bacterial cause of sexually transmitted disease in the world. A well documented feature of chlamydial infection is its high rate of recurrence among sexually active populations. However, it is difficult to distinguish whether the high rate of recurrent disease is due to reinfection or to persistent infection with the same organism. Of particular concern in this era of increasing antibiotic resistance is whether persistent infection is the consequence of increasing resistance to standard antimicrobial therapy. Azithromycin and doxycycline are considered by the Centers for Disease Control and Prevention (CDC) as first line drugs for the treatment of chlamydial infections; erythromycin, ofloxacin and levofloxacin are recommended as alternative-regimen. Although C. trachomatis has been historically sensitive to these antibiotics, in vitro resistance is being increasingly reported. However, although in vitro antimicrobial resistance has been described, the clinical significance of these findings is unknown. C. pneumoniae is associated with community-acquired pneumonias, acute exacerbations of chronic bronchitis, otitis media, sinusitis and reactive airway disease. Persistent nasopharyngeal infection with C. pneumoniae has been documented in adults following acute respiratory infection. Chronic infection with C. pneumoniae has also been implicated in the pathogenesis of atherosclerosis, although this is still very controversial. Azithromycin, clarithromycin and quinolones are frequently used for the treatment of C. pneumoniae respiratory infections. Microbiologic failure has been described in C. pneumoniae infections, even after prolonged courses of azithromycin, erythromycin and doxycycline.     

Atypical pathogens as etiologic agents in hospitalized patients with community-acquired pneumonia in Korea: a prospective multi-center study

Local epidemiologic data on the etiologies of patients hospitalized with community-acquired pneumonia (CAP) is needed to develop guidelines for clinical practice. This study was conducted prospectively to determine the proportion of atypical bacterial pathogens in adults patients hospitalized with CAP in Korea between October 2001 and December 2002. Microbiological diagnosis was determined by serology for antibodies to Mycoplasma pneumoniae, Chlamydia pneumoniae, and Legionella pneumophila. Nucleic acid of M. pneumoniae and C. pneumoniae in respiratory samples and Legionella antigen in urine samples were detected. The study population consisted of 126 patients (71 males, 55 females), averaging 54.6 yr (SD+/-17.8), whose paired sera were available. An etiologic diagnosis for atypical pathogens was made in 18 patients (14.3%): C. pneumoniae 9 (7.1%), M. pneumoniae 8 (6.3%), and L. pneumophila 3 patients (2.4%). Streptococcus preumoniae and other typical pathogens were isolated from 36 patients (28.6%). Of 126 patients, 16 (12.7%) were admitted to intensive care unit and atypical pathogens were identified in 5 patients (31.3%). Initial clinical features of patients with pneumonia due to atypical, typical or undetermined pathogens were indistinguishable. We conclude that atypical pathogens should be seriously considered in hospitalized patients with CAP, when initiating empiric treatment in Korea.