Radiographic appearance of Chlamydia pneumoniae (TWAR strain) respiratory infections. CBPIS Study Group. Community-based Pneumonia Incidence Study

Atypical Pneumonia: Definition, Causes, and Imaging Features

Pneumonia is among the most common causes of death worldwide. The epidemiologic and clinical heterogeneity of pneumonia results in challenges in diagnosis and treatment. There is inconsistency in the definition of the group of microorganisms that cause "atypical pneumonia." Nevertheless, the use of this term in the medical and radiologic literature is common. Among the causes of community-acquired pneumonia, atypical bacteria are responsible for approximately 15% of cases. Zoonotic and nonzoonotic bacteria, as well as viruses, have been considered among the causes of atypical pneumonia in a patient who is immunocompetent and have been associated with major community outbreaks of respiratory infection, with relevant implications in public health policies. Considering the difficulty of isolating atypical microorganisms and the significant overlap in clinical manifestations, a targeted empirical therapy is not possible. Imaging plays an important role in the diagnosis and management of atypical pneumonia, as in many cases its findings may first suggest the possibility of an atypical infection. Clarifying and unifying the definition of atypical pneumonia among the medical community, including radiologists, are of extreme importance. The prompt diagnosis and prevention of community spread of some atypical microorganisms can have a relevant impact on local, regional, and global health policies. ^©RSNA, 2021.

Atypical Pneumonia: Updates on Legionella, Chlamydophila, and Mycoplasma Pneumonia

Community-acquired pneumonia (CAP) has multiple causes and is associated with illness that requires admission to the hospital and mortality. The causes of atypical CAP include Legionella species, Chlamydophila, and Mycoplasma. Atypical CAP remains a diagnostic challenge and, therefore, likely is undertreated. This article reviews the advancements in the evaluation and treatment of patients and discusses current conflicts and controversies of atypical CAP.

Two cases of acute respiratory distress syndrome with high values of Chlamydophila pneumoniae-specific antibodies

We herein report two cases of acute respiratory distress syndrome (ARDS) with high values of Chlamydophila pneumoniae-specific antibodies. In the first case (a 65-year-old man), high levels of anti-C. pneumoniae antibodies (IgG and IgA) were detected on admission, and the anti-C. pneumoniae IgA level rose by Day 30. The patient was successfully treated with quinolone and steroids. In the second case (an 85-year-old man), abnormally high levels of anti-C. pneumoniae IgM were detected on admission. The patient did not recover, despite receiving treatment with several antibiotics and anti-inflammatory agents. Neither of the patients displayed other pathogen-specific antigens or antibodies. Chlamydophila pneumonia is usually mild, although it can cause severe interstitial pneumonia and ARDS in reinfected patients and the elderly.

Bilateral hilar lymphadenopathy due to Chlamydia pneumoniae infection

We here report a 5-year-old boy who presented with cough and bilateral hilar lymphadenopathy with a family history of sarcoidosis. The laboratory investigations did not confirm this diagnosis. The child was serologically proven to have Chlamydia pneumoniae infection. He responded well to a course of erythromycin resulting in complete resolution of his symptoms and the presenting radiographic findings on his initial chest X-ray. Pediatr. Pulmonol. 2011; 46:1038-1040. © 2011 Wiley-Liss, Inc.

Chlamydophila pneumoniae

Chlamydophila pneumoniae is estimated to cause about 10% of community-acquired pneumonia (CAP) cases and 5% of bronchitis cases, although most patients with C pneumoniae infection are asymptomatic, and the course of respiratory illness is relatively mild. The incubation period of C pneumoniae infection is around 21 days, and such symptoms as cough and malaise show a gradual onset, yet may persist for several weeks or months despite appropriate antibiotic therapy. Diagnosis by nasopharyngeal specimen culture, serum antibody titers, or molecular techniques is usually delayed with respect to the onset of symptoms, antibiotic treatment, or disease resolution and there is no accurate, standardized, commercial US Food and Drug Administration-cleared diagnostic method available. Erythromycin, tetracycline, and doxycycline are used as first-line therapy, although some investigators report no clinical or survival benefits from treating CAP caused by atypical pathogens. Meanwhile, adequate prospective studies have met with ethical and logistic barriers. Despite these limitations, North American guidelines recommend the antimicrobial treatment of patients with acute C pneumoniae respiratory infection.

HIV-related pneumococcal lung disease: does highly active antiretroviral therapy or bacteremia modify radiologic appearance?

We reviewed chest radiographs of 57 HIV-infected patients with pulmonary diseases in whom Streptococcus pneumoniae was the sole respiratory pathogen isolated to evaluate whether highly active antiretroviral therapy (HAART) or bacteremia modify radiographic appearance. Pneumococcal lung disease presented as lobar pneumonia in 40% of the cases, 54% of whom were on HAART; as bronchopneumonia in 42%, 58% on HAART; as interstitial infiltrates in 17%, 60% on HAART. Bacteremia was observed 38 times in 23 patients with CD4 less than 200/mm(3), and in 15 with CD4 greater than 200/mm(3) (p > 0.05). HAART does not significantly influences radiographic appearances of lung disease caused by Streptococcus pneumoniae (p > 0.05). Immunosuppression induced by HIV infection was a major risk factor for development of pneumococcal lung disease (p = 0.04) and influences radiographic appearance; bronchopneumonia (p = 0.006), in particular multifocal (p = 0.008), which was more frequent in subjects with CD4 less than 200/mm(3). Bacteremia influences radiographic appearance of pneumococcal lung disease; lobar pneumonia was more frequent (p = 0.003), and considering CD4 cell count, was more frequent if CD4 cell count was above 200/mm(3). An original finding of this study was the frequency of interstitial changes. This pattern of pneumonia, found in 17% of our patients, could represent a difference between HIV-seropositive and -seronegative subject in displaying pneumococcal lung disease.

Acute exacerbation of idiopathic pulmonary fibrosis: role of Chlamydophila pneumoniae infection

BACKGROUND AND OBJECTIVES

Patients with idiopathic pulmonary fibrosis (IPF) may experience acute exacerbations of their illness. The actual trigger(s) of such exacerbations is unknown. Chlamydophila pneumoniae infection can cause exacerbation of asthma and COPD. A prospective study was conducted to investigate the possible role of C. pneumoniae infection in triggering acute exacerbations of IPF.

METHODS

A prospective observational study over 5 years of consecutive IPF patients who fulfilled the criteria for acute exacerbation. Sputum, blood cultures and acute and convalescent serology for C. pneumoniae IgG and IgA (ELISA) were performed.

RESULTS

Previous infection with C. pneumoniae is common. Of the 27 study patients, 15 had a C. pneumoniae IgG index of 1.10-2.99 (positive) and 3 had a C. pneumoniae IgG index of >2.99 (strongly positive) at the time of presentation with an acute exacerbation. In addition, 15 subjects had a C. pneumoniae IgA index of 1.10-2.99 (positive) and 6 subjects had a C. pneumoniae IgA index of >2.99 (strongly positive). However, only two of the 15 subjects (13%) for whom paired sera were tested exhibited a significant rise in antibody response (change in index of 1.90 for C. pneumoniae IgG and 1.54 for IgA, respectively) indicating either acute or reactivated infection with C. pneumoniae. There were 15 deaths (56%) despite supportive care that included high-dose corticosteroid therapy and oxygen supplementation.

CONCLUSIONS

Mortality is high with acute exacerbation of IPF. Acute infection with C. pneumoniae is uncommon at the time of presentation with acute exacerbation of IPF.

Chlamydial infection showing migratory pulmonary infiltrates

A 70-year old man was admitted to our hospital because of nonproductive cough, fever and increasing dyspnea associated with alveolar opacities on chest roentgenogram, which later migrated to previously unaffected areas. The diagnosis of Chlamydial pneumonitis was made on serological grounds. Organizing pneumonia was documented by transbronchial lung biopsies and the subsequent course was satisfactory under minocycline therapy. Chlamydial infection should be considered in the differential diagnosis of migratory pulmonary infiltrates.

Community epidemiology of Chlamydia and Mycoplasma pneumoniae in LRTI in France over 29 months

BACKGROUND

The role of Chlamydia pneumoniae (CP) and Mycoplasma pneumoniae (MP) in lower respiratory tract infections (LRTI) is still little known in community settings.

METHODS

In all, 3207 adult cases of LRTI (871 with pneumonia, and 2336 with acute bronchitis) were prospectively included in the ETIIC1 ETIIC : ETude de l'Incidence des Infections respiratoires basses d'origine Communautaire dues A Chlamydia pneumoniae et Mycoplasma pneumoniae (Incidence of CP and MP in LRTI in community settings) program by 303 general practitioners and 24 hospital physicians in France between September 1997 and February 2000. The polymerase chain reaction and immunoassays were used to detect CP or MP in 3198 pharyngeal specimens obtained by gargling.

RESULTS

Of these 3198 patients, 232 (7.3%), were PCR-positive for CP and/or MP. Immunoassays were far less sensitive than PCRs (Se = 2 and 13% for MP and CP). Among the 2336 patients with acute bronchitis, PCR was positive for CP in 95 (4.1%), and for MP, in 54 (2.3%). Among the 671 patients with radiologically confirmed pneumonia, PCR was positive for CP in 23 (3.4%), and for MP in 49 (7.3%). CP and MP displayed significant geographic heterogeneity. Independent clinical determinants of positive PCR for CP and/or MP were age below 45 years, previous antimicrobial therapy (especially betalactams). Clinical signs were not of practical use in distinguishing accurately between etiologic diagnoses.

CONCLUSIONS

CP or MP diagnosed by PCR were found in more than 7% of patients with LRTI in community settings with a significant geographical heterogeneity and significant temporal trends in the incidence.

Reliability of radiographic findings and the relation to etiologic agents in community-acquired pneumonia

In a clinical setting the chest radiograph is the reference standard in establishing the diagnosis of community-acquired pneumonia (CAP). This study aimed to assess interobserver reliability (IR) of radiographic findings and the relationship to different causative pathogens in CAP. Chest radiographs of 192 patients with pneumonia, obtained from a database, were reviewed by 2 radiologists and 1 respiratory physician without specific clinical information. Main pattern of infiltrate, extent of pneumonia, presence of pleural fluid, thickened bronchial walls, lymphadenopathy and air bronchogram were scored. Also, the involved lobes were identified. Sputum cultures, blood cultures and serological tests were performed to identify the causative pathogen. IR was poor (kappa <0.4) for determining the main pattern of infiltrate and presence of air bronchogram, lymphadenopathy and thickening of bronchial walls. IR was fair to good (kappa 0.4-0.7) or even excellent (kappa>0.7) for determining the presence of pleural effusion, the extent of pneumonia and for identifying the lobes involved. Mycoplasma pneumoniae was associated more often with patchy alveolar opacities than Streptococcus pneumoniae (P=0.05). Chlamydia spp. were associated with unilobar involvement (86%), especially when compared to M. Pneumoniae (P=0.03) and S. pneumoniae (P=0.004). In conclusion, simple features such as presence of pleural fluid, the extent of pneumonia and identifying the involved lobes show fair to excellent IR. Other features such as main pattern of infiltrate are difficult to assess and show poor IR. Hardly any relation between different pathogens and radiological features was found. Therefore, chest radiographs are of limited value in predicting the causative pathogen, but are of good use to determine the extent of pneumonia and to detect complications such as parapneumonic effusion.

Chlamydia pneumoniae: comparison with findings of Mycoplasma pneumoniae and Streptococcus pneumoniae at thin-section CT

PURPOSE

To retrospectively compare thin-section computed tomographic (CT) findings of Chlamydia pneumoniae pneumonia with those of Streptococcus pneumoniae pneumonia and Mycoplasma pneumoniae pneumonia.

MATERIALS AND METHODS

Institutional review board and patient informed consent were not required. Twenty-four patients with C pneumoniae pneumonia (17 men, seven women; age range, 19-89 years) underwent thin-section CT; 41 patients with S pneumoniae pneumonia (28 men, 13 women; age range, 19-91 years) and 30 patients with M pneumoniae pneumonia (20 men, 10 women; age range, 16-67 years) were also enrolled. Thin-section CT scans of each patient were retrospectively and independently assessed by two chest radiologists for consolidation, ground-glass opacity (GGO), bronchovascular bundle thickening, nodules, pleural effusion, lymphadenopathy, reticular or linear opacity, airway dilatation, pulmonary emphysema, and bilateral lung involvement. Consensus was reached for disagreements. The frequency of each finding was compared among the three types of pneumonia by using the chi2 test.

RESULTS

For C pneumoniae pneumonia, CT demonstrated consolidation in 20 patients, GGO in 13, bronchovascular bundle thickening in 17, nodules in 18, pleural effusion in six, lymphadenopathy in eight, reticular or linear opacity in 15, airway dilatation in nine, pulmonary emphysema in 11, and bilateral lung involvement in 12. Bronchovascular bundle thickening (P = .022) and airway dilatation (P = .034) were significantly more frequent in patients with C pneumoniae pneumonia than in those with S pneumoniae pneumonia. Reticular or linear opacity (P = .017), airway dilatation (P = .016), and associated pulmonary emphysema (P = .003) were significantly more frequent in patients with C pneumoniae pneumonia than in those with M pneumoniae pneumonia.

CONCLUSION

C pneumoniae pneumonia demonstrates a wide spectrum of thin-section CT findings that are similar to those of S pneumoniae pneumonia and M pneumoniae pneumonia; airway dilatation and bronchovascular thickening were significantly more frequent in patients with C pneumoniae pneumonia.

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.

Community-acquired pneumonia of mixed etiology: prevalence, clinical characteristics, and outcome

Community-acquired pneumonia (CAP) of mixed etiology has increasingly been appreciated in the literature, but its clinical significance remains unknown. The aim of this analysis was to describe the prevalence, clinical characteristics, and outcome of CAP of mixed etiology. Data were obtained from a 2-year prospective study of consecutive patients with CAP in whom an extensive microbiological workup was performed. Predefined strict criteria were used to establish the etiology. A total of 493 patients were included. A single pathogen was detected in 222 (45%) cases and two or more pathogens in 28 (5.7%) cases. Mixed infections were seen across all age groups and in patients treated both in hospital and as outpatients. The most frequent combinations of pathogens were those of a bacterium plus an "atypical" organism (28.6%) and of two bacterial organisms (28.6%). Compared with patients with monomicrobial pneumonia, patients with mixed pneumonia were more likely to have underlying conditions (64% vs. 45%, p=0.04) and dementia (25% vs. 10%, p=0.02). The incidence of a defined series of complications was higher in patients with mixed pneumonia (39.3% vs. 18.6%; OR=2.84; p=0.02). Community-acquired pneumonia of mixed etiology is uncommon. Patients with mixed pneumonia are more likely to have underlying medical conditions, and they may have a more severe course of disease.

Imagerie moderne des pneumonies infectieuses aiguës

Les pneumonies infectieuses aiguës constituent un problème de santé publique important, car elles sont une cause majeure de morbidité et de mortalité chez l’adulte. Si les données cliniques et radiographiques permettent le plus souvent de faire le diagnostic de pneumonie infectieuse, le diagnostic étiologique est plus difficile. En effet, de nombreux agents pathogènes peuvent être responsables de pneumonie et la réaction du parenchyme pulmonaire est peu variée, d’où la faible spécificité des lésions radiologiques observées en dehors de quelques cas particuliers. C’est pourquoi la compréhension des mécanismes physiopathologiques permet d’expliquer certains aspects radiologiques. De même, la connaissance des bases anatomocliniques et radiologiques autorise la reconnaissance de trois aspects radiographiques principaux. Quant à l’appréciation des contextes épidémiologique et immunitaire, ils peuvent permettre également d’approcher le germe en cause.

Chlamydia pneumoniae respiratory infection after allogeneic stem cell transplantation

Chlamydia pneumoniae is a common cause of upper and lower respiratory tract infections in immunocompetent patients; however, its role as a respiratory pathogen in immunocompromised hosts has been infrequently recognized. We describe C. pneumoniae lower respiratory tract infection in a 19-year-old male after allogeneic stem cell transplantation. The patient developed fever on day +14, and a subsequent computed tomography scan of the chest revealed a right lateral pleural-based opacity, which was then resected during thoracoscopy. Diagnosis was made by culture and staining of the resected tissue with C. pneumoniae-specific monoclonal antibodies, and azithromycin was administered. To the best of our knowledge, this is the first report of C. pneumoniae respiratory infection after stem cell or marrow transplantation. C. pneumoniae often coexists with other etiologic agents of pneumonia in immunocompromised patients. Considering the infrequency of infections from this organism in this clinical setting, one must still rule out other more likely respiratory pathogens.

Nonresolving or slowly resolving pneumonia

Given the variability in rate of radiographic resolution, it remains controversial to decide when to initiate an invasive diagnostic work-up for nonresolving or slowly resolving pulmonary infiltrates. In immunocompetent patients who present with classical features of CAP (i.e., fever, chills, productive cough, new pulmonary infiltrate), clinical response to therapy is the most important determinant for further diagnostic studies. Within the first few days, persistence or even progression of infiltrates on chest radiographs is not unusual. Defervescence, diminished symptoms, and resolution of leukocytosis strongly support a response to antibiotic therapy, even when chest radiographic abnormalities persist. In this context, observation alone is reasonable, and invasive procedures can be deferred. Serial radiographs and clinical examinations dictate subsequent evaluation. In contrast, when clinical improvement has not occurred and chest radiographs are unchanged or worse, a more aggressive approach is warranted. In this setting, we advise fiberoptic bronchoscopy with BAL and appropriate cultures for bacteria, legionella, fungi, and mycobacteria. When endobronchial anatomy is normal and there is no purulence to suggest infection, TBBs should be done to exclude noninfectious causes (discussed earlier) or infections attributable to mycobacteria or fungi. An aggressive approach is also warranted in patients who are clinically stable or improving when the rate of radiographic resolution is delayed. As discussed earlier, what constitutes excessive delay is controversial, and depends upon the acuity of illness, specific pathogen, extent of involvement (i.e., lobar versus multilobar), comorbidities, and diverse host factors. Stable infiltrates even 2 to 4 weeks after institution of antibiotic therapy does not mandate intervention provided patients are improving clinically. Invasive techniques can also be deferred when unequivocal, albeit incomplete, radiographic resolution can be demonstrated. Lack of at least partial radiographic resolution by 6 weeks, even in asymptomatic patients, however, deserves consideration of alternative causes (e.g., endobronchial obstructing lesions, or noninfectious causes). Fiberoptic bronchoscopy with BAL and TBBs has minimal morbidity and is the preferred initial invasive procedure for detecting endobronchial lesions or substantiating noninfectious causes. The yield of bronchoscopy depends on demographics, radiographic features, and pre-test likelihood. In the absence of specific risk factors, the incidence of obstructing lesions (e.g., bronchogenic carcinomas, bronchial adenomas, obstructive foreign body) is low. Bronchogenic carcinoma is rare in nonsmoking, young (< 50 years) patients but is a legitimate consideration in older patients with a history of tobacco abuse. Non-neoplastic causes (e.g., pulmonary vasculitis, hypersensitivity pneumonia, etc.) should be considered when specific features are present (e.g., hematuria, appropriate epidemiologic exposures). Ancillary serologic tests or biopsies of extrapulmonary sites are invaluable in some cases. In rare instances, surgical (open or VATS) biopsy is necessary to diagnose refractory or non-resolving "pneumonias."

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

Infections caused by M. pneumoniae, C. pneumoniae, and Legionella spp. are important causes of community-acquired pneumonia (CAP). In the past decade, considerable new information has come to light concerning these organisms. Despite this, debate continues concerning the syndromic approach to CAP and the scientific merit of lumping these pathogens together. Because the etiologic diagnosis of these pathogens is established only in a minority of cases, the true prevalence tends to be underestimated. In clinical practice, these pathogens are often empirically treated. More rapid and cost-effective diagnostic techniques are needed so that the clinical course of patients with these infections can be better characterized.

Mediastinal lymphadenitis associated with Chlamydia pneumoniae infection

A young woman presented with mediastinal lymphadenitis and measles-like eruption. All clinical manifestations promptly responded to macrolide therapy. Serologically, current infection of Chlamydia pneumoniae was highly suspected. Evaluation of Chlamydia pneumoniae infection should be included in the diagnostic approach to mediastinal lymphadenitis.

[Clinical manifestations of Chlamydia pneumoniae infections]

Chlamydia pneumoniae is a newly described and ubiquitous bacterium. Most infections are asymptomatic as shown by a high worldwide seroprevalence (> 50% of cases). It is a common cause of acute respiratory infections, mainly pneumonia (> 50% of cases) and other acute respiratory tract infections (25% of acute bronchitis, < 5% of sinusitis, otitis and pharyngitis). About 10% of the community acquired pneumonia cases have been associated with Chlamydia pneumoniae infection. This incidence depends on a cyclic epidemiology with a high incidence for 2 to 3 years followed by a low prevalence for 3 to 4 years. Most chlamydial infections are mild but occasionally severe with death especially in old people. Mostly acute infections are recurrent infections. The seroprevalence is higher in asthmatic patients, its role in acute exacerbation of chronic bronchitis is not definitely established. Extra-respiratory acute infections are less frequent, either fever alone, or cardiovascular diseases (acute myocarditis, pericarditis and endocarditis) or neurological (encephalitis, meningitis or Guillain-Barré syndrome). In addition, seroepidemiology studies have shown an association with coronary artery disease, Chlamydia pneumoniae was detected in coronary atheroma by immunochemistry, polymerase chain reaction and by electron microscopy. Chlamydia pneumoniae may be involved in the atherosclerotic process. To define the clinical spectrum of infection requires precise laboratory diagnosis, the most efficient tests (PCR, direct immunofluorescence and culture) are done in specialized laboratories, serological tests are less reliable. Macrolides, cyclines and fluoroquinolones are the most potent antibiotics but with differences in vitro within and between these families of antibiotics. Bacteriological failures are described despite the in vitro activity. A lot of questions on clinical aspects, epidemiology and treatment are unanswered, we need more studies.

Ambulatory patients with community-acquired pneumonia: the frequency of atypical agents and clinical course

OBJECTIVES

To determine the etiology of community-acquired pneumonia in patients treated in an ambulatory setting, using serological methods, and to compare presenting symptoms, radiographic manifestations, and clinical outcomes of patients with pneumonia of "atypical" and undetermined etiology.

PATIENTS AND METHODS

This prospective cohort study was conducted in emergency room and outpatient facilities of Victoria General Hospital, Halifax, Nova Scotia, and in offices of participating family doctors based in Halifax. One hundred forty-nine adults with acute onset of one or more symptoms or signs suggestive of pneumonia and radiographic evidence of pneumonia who provided informed consent were enrolled. Patients known to be HIV positive or who had been discharged from a hospital within the previous 10 days were ineligible for enrollment. Demographic features and clinical data were collected by direct patient interview and chart review by trained research nurses. Outcome measures included quantitative evaluation of pneumonia-specific symptoms, and responses to the Short Form 36 Health Survey at presentation and at 30 days after presentation. Information was also collected on each patient's health prior to pneumonia, as well as the time until each patient's self-reported return to work and to usual activities. The etiology of pneumonia was determined by testing acute and convalescent serum samples for antibodies to Legionella pneumophila serogroup 1, Mycoplasma pneumoniae, Chlamydia pneumoniae, Chlamydia psittaci, Coxiella burnetii, adenovirus, respiratory syncytia virus, influenza viruses A and B, and parainfluenza viruses 1, 2, 3.

RESULTS

The study population consisted of 149 patients, 54 (36%) of whom were men, with a mean age (+/- SD) of 41 +/- 15 years. An etiological diagnosis was made in 74 (49.7%) patients using serological methods. Etiological agents included M pneumoniae 34 (22.8%); C pneumoniae 16 (10.7%); M pneumoniae and C pneumoniae 5 (3.4%); C burnetii 4 (2.7%); influenza A virus 4 (2.7%); and other agents 6% (7.4%). Three patients (2%) had a conventional bacterial etiology, and 72 patients (48.3%) had pneumonia of undetermined etiology. Patients with pneumonia of known (atypical) and undetermined etiology were similar in terms of age, gender, race, education, employment, and comorbidity. Despite a higher proportion of patients with pneumonia of known etiology reporting sweats, chills, and headache at presentation, the two groups were similar for symptom severity and bother. The patients with pneumonia of undetermined etiology were more likely to have multilobar pneumonia (P < 0.02). Both patients with atypical pneumonia and those with pneumonia of undetermined etiology suffered severe deterioration of physical functioning with a marked but incomplete recovery at 30 days. Those with atypical pneumonia had higher physical functioning and general mental health scores at 30 days.

CONCLUSIONS

Nearly half the cases of ambulatory community-acquired pneumonia are due to "atypical" agents. It is not possible to reliably distinguish patients with atypical pneumonia from those with pneumonia of undetermined etiology by clinical features at baseline. The outcomes in terms of resolution of symptoms, functional status, return to work, and return to usual activities are essentially similar in the two groups.

Chlamydia pneumoniae pneumonia in hospitalized patients. Clinical characteristics and diagnostic value of polymerase chain reaction detection in BAL

STUDY OBJECTIVE

To evaluate the incidence and clinical characteristics of Chlamydia pneumoniae infection as detected by polymerase chain reaction (PCR) and culture of BAL in hospitalized patients with pneumonia, HIV-infected persons, and control subjects.

DESIGN

Prospective, comparative clinical study.

SETTING

University hospital medical center.

PATIENTS

Fifty-seven hospitalized patients with acute lower respiratory tract infection (group 1); 47 HIV-positive patients (group 2); 100 patients with noninfectious bronchopulmonary disorders (group 3).

INTERVENTIONS

BAL was performed in all patients at hospital admission for diagnostic purposes. In addition to semiquantitative bacterial and fungal culture, isolation and detection of C pneumoniae were performed by cell culture and PCR of the lavage fluid.

MEASUREMENTS AND RESULTS

C pneumoniae was detected in 16% of group 1, 13% of HIV-positive persons, and 0% of control subjects. The sensitivity of chlamydial culture was much lower as compared with PCR (4 vs 15 cases). In contrast to group 1, in the HIV-positive patients, acute respiratory symptoms were not always present, and in 3 of 6 cases, copathogens were found in the BAL. BAL differential cell counts disclosed a significant lymphocyte elevation mostly due to the CD8 subset (group 1: 15% vs 5%; group II: 18.5% vs 4%; C pneumoniae positive vs negative cases, respectively).

CONCLUSIONS

C pneumoniae is frequently detected in the BAL of hospitalized patients with pneumonia as sole pathogen. PCR detection is highly specific and far more sensitive than cell culture. Asymptomatic carriage seems to be uncommon in immunocompetent patients, but does occur in HIV-positive patients. A lymphocytic alveolitis is frequently found by BAL cytologic study and may represent a T-cell response to chlamydial infection in the lower respiratory tract.

Chlamydia pneumoniae community-acquired pneumonia: a review of 62 hospitalized adult patients

In a prospective study, Chlamydia pneumoniae was identified as the etiological agent in 62 (17.9%) of 346 adult patients hospitalized over the course of one year for community-acquired pneumonia at the Soroka Medical Center in Beer-Sheva, Israel. The diagnosis of C. pneumoniae infection was based on serological testing of antibodies by the MIF technique. In 43 of these patients (69.4%), at least one other etiological agent, in addition to C. pneumoniae for community-acquired pneumonia was identified. Streptococcus pneumoniae was identified in 34 patients with C. pneumoniae (54.8%), as an additional causative factor in infection. Community-acquired pneumonia patients with C. pneumoniae were significantly older than non-C. pneumoniae patients (p = 0.03), had a higher APACHE II score on admission (p < 0.05), a higher rate of positive blood cultures (p = 0.02), and longer periods of hospitalization (p = 0.022). Seven patients with pure C. pneumoniae infection recovered, despite treatment which is not considered to be specific for C. pneumoniae. It was concluded that C. pneumoniae is a common etiological agent for community-acquired pneumonia in our region, particularly in the elderly, and is characterized by a high rate of concomitant infections with other pulmonary pathogens. No specific clinical or radiological pattern was discerned that could distinguish between C. pneumoniae community-acquired pneumonia and non-C. pneumoniae community-acquired pneumonia.