The differentiation of Chlamydia species by antigen detection in sputum specimens from patients with community-acquired acute respiratory infections

Comparison of Cell Culture with Three Conventional Polymerase Chain Reactions for Detecting Chlamydophila pneumoniae in Adult's Pharyngotonsillitis

Chlamydophila pneumoniae is an intracellular pathogen responsible for respiratory tract infections. The isolation of the microorganism from clinical specimens is essential for a diagnosis. However, the identification of C. pneumoniae by cell cultures is very difficult besides strongly depending on the sample conditions. The study aimed to investigate, in adult patients with pharyngotonsillitis, the frequency of Chlamydophila pneumoniae detection by cell cultures and three conventional PCRs (a conventional PCR targeting the 16S rRNA gene and two nested PCRs, targeting the 16S rRNA gene and the ompA gene, respectively). The presence of chlamydial inclusion in cell cultures was observed in 11/94 samples (11.70%) by IFA. C. pneumoniae DNA was detected in 12/94 (12.76%) specimens by the 16S rRNA gene nested PCR, 4/94 (4.26%) by ompA gene nested PCR, and in 2/94 (2.13%) by 16S rRNA single-step PCR. Our data show poor agreement between the three applied DNA-amplification methods; in fact, only 16S rRNA gene nested PCR showed a statistically significant difference. Moreover, this result allowed us to achieve a definitive confirmation of the previous finding and to avoid the risk of an overestimation of the C. pneumoniae as a pathogen in pharyngotonsillitis.

Chlamydia psittaci (psittacosis) as a cause of community-acquired pneumonia: a systematic review and meta-analysis

Psittacosis is a zoonotic infectious disease caused by the transmission of the bacterium Chlamydia psittaci from birds to humans. Infections in humans mainly present as community-acquired pneumonia (CAP). However, most cases of CAP are treated without diagnostic testing, and the importance of C. psittaci infection as a cause of CAP is therefore unclear. In this meta-analysis of published CAP-aetiological studies, we estimate the proportion of CAP caused by C. psittaci infection. The databases MEDLINE and Embase were systematically searched for relevant studies published from 1986 onwards. Only studies that consisted of 100 patients or more were included. In total, 57 studies were selected for the meta-analysis. C. psittaci was the causative pathogen in 1·03% (95% CI 0·79-1·30) of all CAP cases from the included studies combined, with a range between studies from 0 to 6·7%. For burden of disease estimates, it is a reasonable assumption that 1% of incident cases of CAP are caused by psittacosis.

Laboratory diagnosis of Chlamydia pneumoniae infections

Chlamydia pneumoniae is an important cause of respiratory illness. There is a need for accurate and rapid laboratory diagnostic methods that will lead to improved patient care, appropriate use of antimicrobial therapy and a better understanding of the epidemiology of this emerging pathogen. Culture is highly specific but is technically demanding, expensive, has a long turnaround time and its sensitivity is highly dependent on transport conditions. Antigen detection tests such as enzyme immunoassay and direct fluorescent antibody assay, and molecular detection methods such as the polymerase chain reaction assay, may provide a rapid diagnosis without the requirement for stringent transport conditions. The results of these tests should be interpreted with caution until more thorough evaluation is available. Serology remains the method of choice. The limitations of different serological methods for the laboratory diagnosis of C pneumoniae are discussed.

Diagnosis of community-acquired pneumonia in adults

Community-acquired pneumonia (CAP) is a common presentation to both primary and secondary care, representing approximately 5% of the acute medical intake in the UK. Treatment is often based on an empirical approach, using broad-spectrum antibiotic regimens, with which the majority of patients will achieve clinical cure. However, in cases of severe CAP, initial treatment failure or severe comorbidity, a more rigorous diagnostic approach is required. This review assesses the evidence base behind the common diagnostic methods for CAP, and presents the case for a rapid and accurate microbiological and radiological diagnosis in improving management and outcomes of this common condition.

Microbiological profile of community-acquired pneumonia in adults over the last 20 years

OBJECTIVES

To assess any change in the microbiological profile of community-acquired pneumonia (CAP) in our region over the last 20 years.

METHODS

We compared hospital admissions aged between 15 and 74 (n = 61) in Norfolk (UK) for CAP over a 19-month period in 1982-3 (ST1) with all admissions aged over 16 (n = 99) over a 14-month period in 1999-2000 (ST2). Data were collected for ST1 as part of a prospective multicentred research study, in a period of high Mycoplasma pneumoniae activity. ST2 was a prospective study of clinical practice. Chlamydophila species were differentiated in ST2 using whole-cell immunofluorescence.

RESULTS

A microbiological diagnosis was made in 38 (62%) in ST1 compared with 48 (48%) in ST2. Streptococcus pneumoniae remained the most common pathogen (26% in ST1, 25% in ST2). The incidence of M. pneumoniae was 18% in ST1 and 4% in ST2. The proportion of viral pathogens identified was similar: nine (15%) in ST1 and 14 (14%) in ST2. No cases of Chlamydophila pneumoniae were diagnosed in ST2.

CONCLUSIONS

The microbiological profile of CAP in Norfolk (UK) has not changed over the last 20 years and C. pneumoniae is not a frequent pathogen.

Touchdown enzyme time release-PCR for detection and identification of Chlamydia trachomatis, C. pneumoniae, and C. psittaci using the 16S and 16S-23S spacer rRNA genes

Three touchdown enzyme time release (TETR)-PCR assays were used to amplify different DNA sequences in the variable regions of the 16S and 16S-23S spacer rRNA genes specific for Chlamydia trachomatis, Chlamydia pneumoniae, and Chlamydia psittaci as improved tests for sensitive diagnosis and rapid species differentiation. The TETR-PCR protocol used 60 cycles of amplification, which provided improved analytical sensitivity (0.004 to 0.063 inclusion-forming unit of Chlamydia species per PCR). The sensitivity of TETR-PCR with primer set CTR 70-CTR 71 was 96.7%, and the specificity was 99.6%, compared to those of the AMPLICOR PCR for the detection of C. trachomatis in vaginal swab samples. TETR-PCR for C. pneumoniae with primer set CPN 90-CPN 91 was 90% sensitive and 93.3% specific compared with a nested PCR with primer set CP1/2-CPC/D for clinical respiratory samples. TETR-PCR for C. psittaci with primer set CPS 100-CPS 101 showed substantial agreement with cell culturing (kappa, 0.78) for animal tissue samples. Primer sets were then combined into a single multiplex TETR-PCR test. The respective 315-, 195-, and 111-bp DNA target products were precisely amplified when DNA from each of the respective Chlamydia species or combinations of them was used. Multiplex chlamydia TETR-PCR correctly identified one strain of each of the 15 serovars of C. trachomatis, 22 isolates of C. pneumoniae, and 20 isolates of C. psittaci. The primer sets were specific for each species. No target products were amplified when DNA from C. pecorum or a variety of other microorganisms was tested for specificity. TETR-PCR with primers selected for specific sequences in the 16S and 16S-23S spacer rRNA genes is a valuable test that could be used either with individual primers or in a multiplex assay for the identification and differentiation of Chlamydia species from culture isolates or for the detection of chlamydiae in clinical samples.

Comparison of throat swabs with sputum specimens for the detection of Chlamydia pneumoniae antigen by direct immunofluorescence

AIM

To compare throat swabs with sputum specimens for Chlamydia pneumoniae antigen detection.

METHODS

During a one year period, sputum and throat swabs from 50 patients over 15 years of age with acute or persisting lower respiratory tract infection were examined for C pneumoniae antigen by direct immunofluorescence.

RESULTS

C pneumoniae antigen was detected in 18/50 patients (36.0%) from sputum, throat swab, or both. Paired sputum and throat swabs were received from 35/50 patients (70.0%). C pneumoniae antigen was detected in either or both specimens from 14/35 patients (40.0%). Of the 14 positive patients, both specimens were positive in nine (64.3%), throat swab only in four (28.6%), and sputum only in one (7.1%). Of the remaining 15 patients from whom only a single specimen was sent, a further three of eight throat swabs and one of seven sputum specimens were positive. There was no statistically significant difference between the results obtained from the two types of specimen.

CONCLUSIONS

Throat swabs may be as good as sputum for the detection of C pneumoniae antigen.

Chlamydia pneumoniae respiratory infections among patients infected with the human immunodeficiency virus

Thirteen cases of Chlamydia pneumoniae infection in patients seropositive for the human immunodeficiency virus (HIV) are described. The occurrence, the clinical spectrum, and the significance of the infection during HIV disease are compared with data reported in the literature. Chlamydia pneumoniae infection was established by a serologic micro-immunofluorescence test using standard diagnostic criteria. In four cases the results of serological tests were confirmed by direct immunofluorescence on respiratory specimens. Five patients developed focal pneumonia but recovered completely after specific antibiotic treatment. Three patients developed severe and diffuse interstitial pulmonary involvement, two of whom died of acute respiratory failure. Five patients developed upper respiratory tract infection. Using 39 pair-matched HIV-seropositive subjects as controls, the cases of infection were found to be significantly associated with a previously diagnosed pulmonary disease. Upon retrospective analysis of 319 consecutive cases of pneumonia among HIV-infected patients, Chlamydia pneumoniae was the sole agent detected in eight (2.5%) cases, and Chlamydia pneumoniae together with other infectious agents was detected in seven (2.2%) cases. Chlamydia pneumoniae is a possible cause of severe respiratory infection in Italian HIV-infected immunocompromised patients, and its presence must be suspected when patients do not respond to therapy with beta-lactam agents or to anti-Pneumocystis carinii treatment.

Prevalence of respiratory viruses and Mycoplasma pneumoniae in sputum samples from unselected adult patients

Sputum samples from adult patients are routinely used for bacteriological tests, but not for the diagnosis of viral/mycoplasmal infections. We examined 511 sputum samples submitted for bacterial tests from patients at the Royal Adelaide Hospital. Each specimen was tested directly (and after six days of cell culture amplification) for antigens to influenza A and B, parainfluenza 1, 2 and 3, adenovirus, respiratory syncytial virus (RSV) and Mycoplasma pneumoniae. Respiratory viruses or M. pneumoniae were found in 11% of all specimens but were most common (14%) in sputa reported as containing only "oral flora". Respiratory virus or M. pneumoniae infection was significantly more common in medical patients (12%) than in surgical patients (5%), and was most common in oncology (hematology/radiotherapy) patients (25%). Influenza A and RSV were equally common in medical patients, while RSV was the most frequent isolate in oncology patients. Respiratory viral infection is an underdiagnosed condition in adults, particularly the immunocompromised, which can be successfully diagnosed by virological examination of sputum.

Rapid diagnosis of chlamydial respiratory infection in children

A study was undertaken to determine the incidence of chlamydial respiratory infection in paediatric patients during a 12-month period by antigen detection. Nasopharyngeal aspirates (NPA) from 514 patients were screened for genus-specific chlamydia antigen using the Pharmacia Chlamydia enzyme immunoassay (EIA) and Kallestad immunofluorescence (IF) assays. EIA screen-positive samples were confirmed by specific blocking antibody. Specimens which were EIA positive or IF positive were cultured for chlamydia. The NPAs from 7 patients were positive in the EIA and IF assays. Four of these patients were culture positive for chlamydia. Our results showed that the incidence of chlamydia respiratory infection by antigen detection was 1.4% or 0.8% if confirmed by culture.

Evaluation of serological methods in the diagnosis of Chlamydia pneumoniae pneumonia during an epidemic in Finland

A complement fixation (CF) test, a micro-immunofluorescence (micro-IF) test and an enzyme immunoassay (EIA) using Re-lipopolysaccharide as antigen were compared in the diagnosis of chlamydial infection in 136 mainly elderly patients hospitalized with community-acquired pneumonia during a Chlamydia pneumoniae epidemic in Finland in 1986-1987. Chlamydial pneumonia was diagnosed in 58 (42.6%) of the 136 pneumonia patients; 44 (75.9%) of them could be shown by micro-IF to be caused by Chlamydia pneumoniae, three by Chlamydia psittaci and four by Chlamydia spp. Only 5 (11.4%) of 44 patients with Chlamydia pneumoniae pneumonia were IgM-positive, indicating that the majority of cases were reinfections. In this population of mainly elderly patients the CF test was insensitive, being positive in only 6 (10.3%) of 58 cases of chlamydial pneumonia. The EIA detected 72.4% of cases and micro-IF 87.9% of cases (including infections with Chlamydia pneumoniae, Chlamydia psittaci and Chlamydia spp.). In the EIA 77% of positive cases were positive in serum samples taken a week apart, whereas the corresponding figure for micro-IF was 50%. In micro-IF the measurement of IgA antibody levels is recommended and IgM-positive sera should be retested after removal of IgG antibody to avoid false-positive findings due to presence of rheumatoid factor. The collection of a third serum sample, for instance one month after onset, is also recommended, since half of the patients showed a diagnostic response in the micro-IF only in the sera taken one month apart.

Detection of Chlamydia pneumoniae and Chlamydia psittaci in sputum samples by PCR

AIMS

To use the polymerase chain reaction (PCR) to detect Chlamydia pneumoniae and Chlamydia psittaci in sputum samples.

METHODS

A nested PCR was developed, the first stage of which amplified DNA from both C pneumoniae and C psittaci while the second stage targeted specifically at C pneumoniae, allowing the two species to be differentiated. The primers were designed not to amplify sequences from C trachomatis. A panel of 26 sputum samples from patients with community acquired pneumonia evaluated previously by enzyme linked immunosorbent assay (ELISA), direct immunofluorescence (DIF), and culture was tested blind by PCR. Most of these specimens also had accompanying serial serum samples which were tested for species specific antibodies using microimmunofluorescence (micro-IF).

RESULTS

PCR detected C pneumoniae DNA in 10 of the 26 samples and C psittaci DNA in four. There was good concordance between ELISA, DIF, micro-IF and PCR in the C pneumoniae group. Two of the C psittaci identified by PCR were labelled C pneumoniae by DIF but the PCR results were supported by serology or a history of bird contact. Of the PCR negative group: six were true negative results; two contained C trachomatis. There were four discrepant results.

CONCLUSIONS

The data suggest that PCR is effective in the detection of C pneumoniae. The sensitivity for C psittaci is inevitably lower due to the strategy taken but specificity seemed to be good.

Prospective study of aetiology and outcome of adult lower-respiratory-tract infections in the community

Community-acquired adult lower-respiratory-tract infections (LRTI) are generally thought to be caused by atypical and viral infections. We have studied 480 adults presenting to a single general practice with community-acquired LRTI between November, 1990, and December, 1991. The overall incidence was 44 cases per 1000 population per year; the incidence was 2-4 times higher in people aged 60 and over than in those aged less than 50. 206 patients were studied in detail; among this group 91 (44%) had 113 pathogens identified. There were 92 bacteria (Streptococcus pneumoniae in 62 and Haemophilus influenzae in 16), 19 viruses (influenza virus in 12), and only 2 atypical pathogens (Mycoplasma pneumoniae and Coxiella burnetii). Pneumococcal infection was common in people who were 60 or older, those who had underlying chronic disease, or people with both features. There was moderate morbidity in terms of time in bed, time to return to normal activities, and days off work. 25% of patients returned for a second consultation with the general practitioner, in most because of unsatisfactory clinical progress. Community-acquired LRTI are very common, and the range of causative pathogens is similar to that for community-acquired pneumonia. Existing management strategies seem inadequate.