Evaluation of Vircell enzyme-linked immunosorbent assay and indirect immunofluorescence assay for detection of antibodies against Legionella pneumophila

Diagnostic Value of IgA Antibody Measurement in Tick-Borne Spotted Fever (Astrakhan Rickettsial Fever)

Tick-borne spotted fevers caused by Rickettsia occur worldwide. The symptoms of this bacterial infection are similar to those of viral infection, and thus, diagnostic accuracy has special clinical importance. One of the commonly used methods for the diagnosis of tick-borne spotted fever is enzyme-linked immunosorbent assay (ELISA), which is based on estimation of the presence of specific IgM antibodies in blood. However, IgA analysis has not been used for the diagnosis of rickettsial diseases thus far. We investigated the diagnostic value of IgA antibody determination using patient sera collected in the Astrakhan region of Russia, where an isolated site of Astrakhan rickettsial fever (ARF) caused by Rickettsia conorii subsp. caspia is located. Our investigation was performed on serum samples collected from 185 patients diagnosed with Astrakhan rickettsial fever from May to October 2019. Western blot analysis revealed that specific IgA antibodies, as well as IgM antibodies, from patient sera bind to high-molecular-weight pathogen proteins with similar masses. The obtained data show that the determination of IgM alone allows for serological confirmation of diagnosis in only 46.5% of cases but that the determination of both IgM and IgA increases this rate to 66.5%. Taken together, the findings show an important diagnostic value of IgA evaluation for tick-borne spotted fever rickettsiosis. IMPORTANCE Tick-borne spotted fevers caused by Rickettsia occur worldwide. The symptoms of this bacterial infection are similar to the symptoms of viral infection, and thus, diagnostic accuracy has special clinical importance. The most serious spotted fever group rickettsiosis is Rocky Mountain fever in the United States, which is caused by Rickettsia rickettsii, and disease complications can lead to hemiparesis, blindness, or amputation. Rickettsia conorii subsp. caspia causes a rickettsial spotted fever named Astrakhan rickettsial fever (ARF). One of the commonly used methods for the diagnosis of tick-borne spotted fevers is ELISA, which is based on estimation of the presence of specific IgM antibodies in blood, though IgA has not been used for the diagnosis of rickettsial diseases thus far. In this study, we showed that both IgA and IgM should be analyzed in the blood serum samples of patients to significantly enhance the accuracy of diagnostics of tick-borne spotted fever rickettsiosis.

Atypical Pathogen Distribution in Chinese Hospitalized AECOPD Patients: A Multicenter Cross-Sectional Study

Purpose

The proportion of atypical pathogens in patient with AECOPD within mainland China is unknown. The objectives of this study were to determine the distribution of atypical pathogens among Chinese patients with AECOPD, to evaluate the clinical characteristics of different atypical pathogen infections, and to compare different detection methods for atypical pathogens.

Patients and Methods

Specimens were collected from patients with AECOPD from March 2016 to November 2018 at eleven medical institutions in eight cities in China. Double serum, sputum, and urine samples were obtained from 145 patients. Serological and nucleic acid tests were used to assess for Mycoplasma pneumonia and Chlamydia pneumoniae; serological, urinary antigen, and nucleic acid tests were applied to detect Legionella pneumophila. The clinical characteristics of atypical pathogen-positive and -negative groups were also compared.

Results

The overall positivity rate for Mycoplasma pneumoniae was 20.69% (30/145), with the highest rate being 20.00% (29/145) when determined by passive agglutination.The overall positive rates for Chlamydia pneumoniae and Legionella pneumophila were 29.66% (43/145) and 10.34% (15/145), respectively. The most common serotype of Legionella pneumophila was type 6. The maximum hospitalized body temperature, ratio of eosinophils, C-reactive protein (CRP) level, and procalcitonin (PCT) level of the Mycoplasma pneumoniae-positive group were significantly higher than those of the Mycoplasma pneumoniae-negative group. Patients in the Chlamydia pneumoniae-positive group smoked more, had higher proportions of comorbidities and frequent aggravations in the previous two years than those in the Chlamydia pneumoniae-negative group. Furthermore, the forced expiratory volume in one second to forced vital capacity (FEV₁/FVC) ratio assessment of lung function was higher, and the concentration of arterial blood bicarbonate (HCO₃ ^-) was lower in the Legionella pneumophila-positive group than in the Legionella pneumophila-negative group.

Conclusion

Overall, atypical pathogens play an important role in AECOPD. Regarding the testing method, serological testing is a superior method to nucleic acid testing.

Comparison of a novel chemiluminescence immunoassay with the passive agglutination method for the diagnosis of Mycoplasma pneumoniae infection in children

OBJECTIVE

The purpose of this study was to evaluate a newly developed chemiluminescence immunoassay (CLIA) and compare it to passive agglutination (PA) for the diagnosis of pneumonia caused by Mycoplasma pneumoniae in children.

METHOD

A total of 291 children suspected of M. pneumoniae infections were enrolled. Serum samples were obtained from routine diagnostic requests, and specific antibodies were simultaneously detected by PA and CLIA. Cohen's kappa was used to assess the agreement between the PA and CLIA assays, multivariate logistic regression analysis was used to evaluate risk factors for the discordance between the PA and CLIA assays.

RESULTS

The positive rate was 62.2% (181/291) for PA and 61.2% (178/291) for CLIA (P = 0.08). The specificity, sensitivity, negative, and positive predictive values of CLIA for M. pneumoniae infection were 80.09%, 86.7%, 78.8%, and 88.2%, respectively, with the PA test considered as the diagnostic standard. The correlation of the CLIA and PA assays was 76.8%, and the Kappa coefficient was 0.80. Significant correlations were found between the PA titers and the results of MP-IgM (R = 0.88, P < .05) and MP-IgG (R = 0.84, P < .05) detected by CLIA.

CONCLUSIONS

A high degree of consistency was found between the PA and CLIA methods in detecting M. pneumoniae infections. CLIA is a reliable and rapid method and might be a promising alternative assay to PA for the diagnosis of M. pneumoniae infections.

Comparison of enzyme-linked immunosorbent assay with indirect immunofluorescence assay for the diagnosis of Mycoplasma pneumoniae infection

BACKGROUND

The study aimed to compare enzyme-linked immunosorbent assay (ELISA) with indirect immunofluorescence assay (IFA) in the diagnosis of Mycoplasma pneumoniae infection.

METHODS

From March 2016 to May 2017, 180 patients suspected with M. pneumoniae infection were enrolled. The SeroMP kit using ELISA and PNEUMOSLIDE kit using IFA were performed in parallel to detect the IgM antibodies against M. pneumoniae. Cohen's kappa statistics were used to assess the agreement between the ELISA and IFA assays, multivariate logistic regression analysis was used to evaluate risk factors for the discordance between the ELISA and IFA assays.

RESULTS

The mean age of the enrolled subjects was 46.6 ± 21.1 years. For detection of M. pneumoniae infection, the positivities of the ELISA and IFA assays were 15.6% (95% CI: 11.0%, 21.6%) and 10.0% (95% CI: 6.4%, 15.3%), respectively. The total positivity was 19.4% (95% CI: 14.3%, 25.8%). The agreement between the ELISA and IFA assays was low (κ = 0.117, P < 0.001). Variables associated with discordant results between ELISA and IFA assays in multivariate analysis were as follows: male (OR: 0.366; 95% CI: 0.149, 0.899; P < 0.05), age (>33 years old; OR: 0.313; 95% CI: 0.129, 0.758; P < 0.05).

CONCLUSION

In detection of M. pneumoniae infection, low agreement was found in IgM assays between the ELISA and IFA methods, female and younger age were significant risk factors for the discordance. A combination of ELISA and IFA tests would be recommended, in order to detect more patients suspected of M. pneumoniae infection in clinical practice.

Is driving a car a risk for Legionnaires' disease?

Legionnaires' disease (LD) is a major cause of severe community-acquired pneumonia but the source and mode of transmission are not always apparent, especially in sporadic cases. We hypothesized that LD can be acquired from the air-conditioning systems of motor cars. Swabs were taken from the evaporator compartments of the air-conditioning system of scrapped cars. Healthy subjects who were mainly employees of regional transportation companies were tested for antibody to Legionella pneumophila serogroups 1-6; they also completed a questionnaire. Legionella species were detected in 11/22 scrapped cars by the loop-mediated isothermal amplification method. The prevalence of microplate agglutination titres > or =1:32 was significantly higher in subjects who sometimes used car air-conditioning systems. Although we did not prove a direct link between Legionella spp. in the car evaporator and LD, our findings point to a potential risk of car air-conditioning systems in LD, which needs further investigation.

Comparison of the new InoDiag automated fluorescence multiplexed antigen microarray to the reference technique in the serodiagnosis of atypical bacterial pneumonia

The aetiological diagnosis of pneumonia depends largely on culture-, antigen- or PCR-based tests. Atypical agents of pneumonia include Coxiella burnetii, Chlamydophila pneumoniae, Chlamydia psittaci, Legionella pneumophila, Francisella tularensis and Mycoplasma pneumoniae. In these cases, serological tests are commonly used for diagnosis. All of the above species were comparatively screened for by using the InoDiag multiplexed automatic immunofluorescence assay and established reference techniques. The InoDiag assay required 5 microL of serum, took 76 min per serum sample, and required an incubator, a fluorescence reader and interpretation software. In total, 248 single sera from patients were tested, for the diagnosis of pneumonia, and the results obtained with selected serum samples were compared with results obtained with the reference method. It was shown that, for the detection of Coxiella burnetii IgM, the automated assay had a sensitivity and specificity of 100%. For the detection of M. pneumoniae IgM, sensitivity was 100% and specificity was 98%. For the detection of Chlamydophila pneumoniae and Chlamydia psittaci IgG, sensitivity was 81% and specificity was 94%. For the detection of L. pneumoniae IgG, sensitivity was 63% and specificity was 98%. For the detection of F. tularensis IgG and IgM, sensitivity was 100% for both, and specificity was 95% and 100%, respectively. The performance of this serological assay was comparable to that of other assays reported in the literature. This preliminary study shows that the automatic InoDiag assay opens the way to immunofluorescence assay standardization.