Search for agents causing atypical pneumonia in HIV-positive patients by inhibitor-controlled PCR assays

Acute respiratory distress syndrome caused by Mycoplasma pneumoniae in a child: the role of methylprednisolone and clarythromycin

Mycoplasma pneumoniae is recognized as an important agent of pneumonia in pediatric population. In rare situations, severe pulmonary injury can develop. The use of corticoids in these cases remains controversial. A case of a girl with acute respiratory distress syndrome and bilateral pleural effusion secondary to pneumonia due to Mycoplasma pneumoniae is described, with good recovery after appropriate use of methylprednisolone and clarythromicyn.

Lung function and bronchial responsiveness after Mycoplasma pneumoniae infection in early childhood

Mycoplasma (M.) pneumoniae has been associated with exacerbation of symptoms in asthmatic school children and adults; and an etiological role in asthma has been suggested. The purpose of this study was to investigate whether infection with M. pneumoniae in early childhood has a long-term influence on lung function and bronchial responsiveness. In a retrospective, clinical cohort-study children younger than 5 years-of-age when PCR-tested for M. pneumoniae were enrolled. Sixty-five children with clinical symptoms suggesting infection with M. pneumoniae during an epidemic season completed a clinical follow-up examination including lung function testing (28 PCR-positive and 37 PCR-negative). In addition to the PCR-test for M. pneumoniae all respiratory tract specimens were additionally tested for other atypical bacteria and for viruses by PCR. Lung function was measured as specific airway resistance by whole-body plethysmography and bronchial hyperresponsiveness was assessed by cold, dry air hyperventilation. Neither baseline lung function nor bronchial response to cold dry air hyperventilation differed between M. pneumoniae-positive and -negative children: mean baseline lung function were 1.17 versus 1.21 (kPa sec), P = 0.45; and mean change in specific resistance was 13% versus 9%, P = 0.42. In conclusion, M. pneumoniae infection in early childhood was not associated with long-term effects on lung function and bronchial hyperresponsiveness 2 years after infection.

Evaluation of NucliSens easyMAG for automated nucleic acid extraction from various clinical specimens

The objectives of this study were to evaluate the performance of the NucliSens easyMAG platform for nucleic acid extraction from different clinical specimens compared to NucliSens miniMAG platform and manual QIAGEN extraction. The NucliSens easyMAG and the NucliSens miniMAG showed equal performance on 215 throat swabs since real-time nucleic acid sequence-based amplification scored the same samples positive for Mycoplasma pneumoniae (n=9) and Chlamydia pneumoniae (n=5) RNAs, although internal control RNA was slightly better detected with the NucliSens easyMAG (99.3% versus 96.8%). NucliSens easyMAG extracted nucleic acids more efficiently (higher recovery and/or fewer inhibitors) compared to QIAGEN extraction by showing, on average, lower Ct values in real-time LightCycler PCR, although 4 individual specimen out of 45 were found positive only with QIAGEN. For nine M. pneumoniae-positive throat swabs, the mean difference in Ct values between NucliSens easyMAG extraction and QIAGEN extraction was -2.26 (range, -5.77 to +0.60); for the detection of five C. pneumoniae-positive throat swabs, the average difference in Ct values between the two methods was -3.38 (range, -6.62 to -2.02); and for the detection of cytomegalovirus in 24 blood samples, the mean difference in Ct values between the two methods was -0.95 (range, -5.51 to +1.68). The NucliSens easyMAG is considerably easier to perform, efficiently extracts nucleic acids from throat swabs and whole blood, is automated, and has high throughput.

Detection of pulmonary Mycoplasma pneumoniae infections in HIV-infected subjects using culture and serology

OBJECTIVE

The true prevalence of Mycoplasma pneumoniae infections involving the respiratory tracts of HIV-infected individuals is still unclear. This study examined the prevalence of M. pneumoniae in 100 HIV-infected individuals at an AIDS care center in Chennai, India, using conventional laboratory techniques and interpretation criteria.

METHODS

Diagnosis was based on culture, cold agglutination test, and commercial enzyme-linked immunosorbent assay (ELISA) for the qualitative determination of IgM antibodies against M. pneumoniae. The efficacies of the different diagnostic procedures used in the study were analyzed.

RESULTS

The prevalence of M. pneumoniae was 31% by culture and 21% by IgM ELISA. Cough (p=0.03, OR 3.8, 95% CI 1-17.8), myalgia (p=0.04, OR 2.5, 95% CI 1-6.6), rales (p=0.04, OR 2.4, 95% CI 1-6.6), and cervical adenopathy (p=0.03, OR 2.7, 95% CI 1-7.1) were the symptoms that significantly corroborated culture positivity. Patients positive for M. pneumoniae by culture or IgM antibody had significantly greater CD4+ T-cell depletion and anemia than those without any evidence of infection.

CONCLUSIONS

This study provides the means to diagnose M. pneumoniae infection and information on the prevalence of the pathogen in HIV-infected individuals in resource constrained settings. Although modern molecular techniques may provide more insight into the prevalence of M. pneumoniae in HIV-infected individuals, conventional methods can still be used in diagnosis.

Species-specific identification by inhibitor-controlled PCR of ruminant components contaminating industrial crude porcine heparin

With the emergence of bovine spongiform encephalopathy, the source of pharmaceutical heparin is currently restricted to porcine intestinal mucosa. To control the species origin of industrial crude heparin, molecular biology methods relying on species-specific protein or DNA analysis should be developed to identify the ruminant components that might be contaminants in industrial crude porcine heparin (ICPH). Because heparin contained in ICPH is a strong PCR inhibitory substance, it is necessary to explore DNA extraction methods specific for ICPH and develop analysis methods that could monitor the presence of PCR inhibitory substances. In the present studies, DNA was extracted from ICPH by seven methods, and their abilities to remove the PCR inhibitory substances were compared using inhibitory-controlled PCR (IC-PCR). The results showed that, based on the optimization of the final concentration of the internal processing control (IPC), IC-PCR was a rapid, sensitive and efficient way to monitor the presence of PCR inhibitory substances contained in DNA extracted from ICPH, and only the agarose gel purification method could be used to completely eliminate the PCR inhibitory substances contained in ICPH.

Role of prednisolone treatment in severe Mycoplasma pneumoniae pneumonia in children

Mycoplasma pneumoniae pneumonia (MP) is responsible for 10-40% of cases of pediatric community-acquired pneumonia. Occasionally, progression to severe pneumonia occurs despite appropriate antibiotic therapy. We retrospectively evaluated the effect of prednisolone in 15 children with MP whose clinical and radiographic course worsened despite broad-spectrum antibiotics, including appropriate macrolides. The mean ( +/- SD) age was 6.1 +/- 1.9 years, and 10 were boys. All children had received macrolides at presentation, but they had persistent fever and progressively worsening radiographic findings. In addition to broad-spectrum antimicrobial therapy, we added prednisolone (1 mg/kg for 3-7 days, then tapered over 7 days) on day 6 (+/-1.5 days) of admission. Fourteen children became afebrile within 24 hr, and their clinical status and radiographic findings improved over several days. The white blood cell count at presentation was 7,500 +/- 2,000/mm3, with a proportion demonstrating lymphopenia (lymphocyte differential, 19.7 +/- 5.7%). In conclusion, corticosteroid treatment appeared to be temporally associated with clinical and radiographic improvement, and may be helpful for reducing morbidity in children with macrolide-nonresponsive severe MP. Further studies may be warranted.

Laboratory diagnosis of Mycoplasma pneumoniae infection

Diagnosis of Mycoplasma pneumoniae infection is challenging due to the fastidious nature of the pathogen, the considerable seroprevalence, and the possibility of transient asymptomatic carriage. During recent years, various new techniques have been adapted for the diagnosis of M. pneumoniae infection, notably in the field of molecular biology. Standard polymerase chain reaction (PCR) is currently the method of choice for direct pathogen detection, but several PCR-related methods provide enhanced sensitivity or more convenient handling procedures, and have been successfully applied for research purposes. Among these techniques are real-time PCR, nested PCR, reverse transcriptase PCR (RT-PCR) and multiplex PCR. Generally, amplification-based methods have replaced hybridization assays and direct antigen detection. Serology, which is the basic strategy for mycoplasma diagnosis in routine clinical practice, has been improved by the widespread availability of sensitive assays for separate detection of different antibody classes. For the diagnosis of mycoplasma pneumonia, serology and direct pathogen detection should be combined. Extrapulmonary diseases may be diagnosed by direct pathogen detection alone, but the value of this diagnostic approach is limited by the probably immunologically mediated pathogenesis of some manifestations. This review summarizes the current state of Mycoplasma pneumoniae diagnosis, with special reference to molecular techniques. The value of different methods for routine diagnosis and research purposes is discussed.

Determination of PCR efficiency in chelex-100 purified clinical samples and comparison of real-time quantitative PCR and conventional PCR for detection of Chlamydia pneumoniae

BACKGROUND

Chlamydia pneumoniae infection has been detected by serological methods, but PCR is gaining more interest. A number of different PCR assays have been developed and some are used in combination with serology for diagnosis. Real-time PCR could be an attractive new PCR method; therefore it must be evaluated and compared to conventional PCR methods.

RESULTS

We compared the performance of a newly developed real-time PCR with a conventional PCR method for detection of C. pneumoniae. The PCR methods were tested on reference samples containing C. pneumoniae DNA and on 136 nasopharyngeal samples from patients with chronic cough. We found the same detection limit for the two methods and clinical performance was equal for the real-time PCR and for the conventional PCR method, although only three samples tested positive. To investigate whether the low prevalence of C. pneumoniae among patients with chronic cough was caused by suboptimal PCR efficiency in the samples, PCR efficiency was determined based on the real-time PCR. Seventeen of twenty randomly selected clinical samples had similar PCR efficiency to samples containing pure genomic C. pneumoniae DNA.

CONCLUSION

These results indicate that the performance of real-time PCR is comparable to that of conventional PCR, but this needs to be confirmed further. Real-time PCR can be used to investigate the PCR efficiency which gives a rough estimate of how well the real-time PCR assay work in a specific sample type. Suboptimal PCR efficiency of PCR is not a likely explanation for the low positivity rate of C. pneumoniae in patients with chronic cough.

Intensified microbiological investigations in adult patients admitted to hospital with lower respiratory tract infections

The objective of this study was to investigate the diagnostic yield of a programme with intensified microbiological investigations in immunocompetent adult patients with lower respiratory tract infections (LRTI). Patients in the study group were included prospectively and consecutively from September 1st 1997 to May 31st 1998 and were compared with a control group from the preceding year. A total of 67 adult patients were included in the study group and they were compared with 122 adult patients in the control group. The study group underwent fibre-optic bronchoscopy (FOB) with bronchoalveolar lavage (BAL). Only 7% in the historic control group were discharged with an aetiological diagnosis of their infections; while the diagnostic yield in the study group increased to 51% of patients. In the study group the presence of new infiltrates on chest X-ray increased the detection of a microbiological aetiology from 37% with no infiltrates to 62% with infiltrates and recent antibiotic therapy reduced the detection of a microbiological cause of infection from 61% in 36 patients who had not received antibiotic therapy to 39% in 31 patients who had received recent antibiotic therapy prior to microbiological sampling. Patients in the study group with known aetiology had higher values of inflammatory markers than patients with unknown aetiology. For Streptococcus pneumoniae infection culture and urine antigen detection were complimentary depending on recent antibiotic therapy since seven of eight culture-positive patients had not received antibiotic therapy within 72 h prior to investigation, while all four patients positive for urine antigens from S. pneumoniae had received antibiotic therapy within 72 h of urine sampling. In conclusion intensified microbiologic investigations increase the diagnostic yield from 7% to 51% of patients in the study group with an aetiologic diagnosis. Routine FOB with BAL had no apparent effect on clinical outcome and seems only justified in selected patients with severe LRTI with infiltrates on chest X-ray and signs of severe inflammation where a high diagnostic yield is achieved.

Chlamydia trachomatis and Mycobacterium tuberculosis lung infection in an HIV-positive homosexual man

A 31-year-old homosexual man, who was human immunodeficiency virus (HIV)-positive was admitted for fever and cough. Chest computed tomography (CT) revealed the presence of diffuse interstitial reticular nodulation, and brain nuclear magnetic resonance imaging showed the presence of nodular frontal lesions. Microscopic examination of sputum and other body fluids showed the presence of acid-fast bacilli and culture-only growth Mycobacterium tuberculosis. Serology for respiratory tract pathogens was negative except for Chlamydia. An antibody titer in the immunoglobulin G (IgG) class of 1:64 for Chlamydia pneumoniae and, unexpectedly, an antibody titer of 1:1024 for C. trachomatis were found. The patient was successfully treated with antituberculosis agents, and clarithromycin, for presumptive chlamydial infection.

Herpesvirus type 1-8 in BAL fluid from HIV-1-infected patients with suspected pneumonia and from healthy individuals

Pneumonia is still a major problem in human immunodeficiency virus (HIV)-infected patients, and despite extensive investigation the aetiology remains unknown in many cases. The prevalence of the eight human herpesviruses was determined by polymerase chain reaction in 91 samples of bronchoalveolar lavage (BAL) fluid from 72 HIV-infected patients with 91 episodes of suspected pneumonia. The presence of herpesviruses was related to clinical and immunological findings and the prevalence of herpesviruses in HIV-infected patients was compared with the prevalence in BAL fluid from 50 healthy, immunocompetent individuals. Epstein-Barr virus, cytomegalovirus and human herpesvirus-8 (HHV8) were found in 5.5%, 36% and 5.5% of BAL fluid samples from HIV-infected patients. No herpesviruses were detectable in BAL fluid from healthy, immunocompetent individuals. The herpesviruses occurred mainly in patients with CD4+ counts <200 x 10(6) L(-1). All patients with herpesviruses recovered without specific antiviral treatment. Two patients with HHV8 had the diagnosis of Kaposi's sarcoma. It is concluded that cytomegalovirus, Epstein-Barr virus, and human herpesvirus-8 are frequently present in bronchoalveolar lavage fluid from severely immunocompromised human immunodeficiency virus-infected patients with pulmonary symptoms. In bronchoalveolar lavage fluid from healthy, immunocompetent individuals, herpesviruses are absent. Apart from human herpesvirus-8, the present results indicate that the herpesviruses do not play a serious pathogenic role in the development of pulmonary symptoms in human immunodeficiency virus-infected patients.

Chlamydia pneumoniae respiratory infections

Chlamydia pneumoniae is a significant cause of both upper and lower respiratory tract infections. The spectrum of diseases ranges from asymptomatic infection to serious disease, including severe pneumonia and exacerbations of chronic bronchitis requiring mechanical ventilation. There is increasing evidence of involvement of C. pneumoniae infection in bronchial asthma, and the role of this agent in immunocompromised patients has also begun to be appreciated.