Diagnostic, therapeutic and economic consequences of a positive urinary antigen test forLegionellaspp. in patients admitted with community-acquired pneumonia: a 7-year retrospective evaluation

Clinical Characteristics and Microorganisms Isolated in Community-Acquired Pneumonia in the COVID-19 Period

Introduction

Community-acquired pneumonia is a leading cause of mortality and hospital admissions. The aetiology remains unknown in 30-65% of the cases. Molecular tests are available for multiple pathogen detection and are under research to improve the causal diagnosis.

Methods

We carried out a prospective study to describe the clinical characteristics and aetiology of community-acquired pneumonia during the COVID-19 pandemic and to assess the diagnostic effectivity of the microbiological tests, including a molecular test of respiratory pathogens (FilmArray™ bioMérieux).

Results

From the 1st of February 2021 until the 31st of March 2022, 225 patients were included. Failure in microorganism identification occurred in approximately 70% of patients. Streptococcus pneumoniae was the most common isolate. There were 5 cases of viral pneumonia. The tested FilmArray exhibited a low positivity rate of 7% and mainly aided in the diagnosis of viral coinfections.

Conclusions

Despite our extensive diagnostic protocol, there is still a low rate of microorganism identification. We have observed a reduction in influenza and other viral pneumoniae during the COVID-19 pandemic. Having a high NEWS2 score on arrival at the emergency department, an active oncohematological disease or chronic neurological conditions and a positive microbiological test result were related to worse outcomes. Further research is needed to determine the role of molecular tests in the microbiological diagnosis of pneumonia.

Association between the Timing of Urinary Antigen Testing and Outcomes in Legionella Pneumonia Patients: A Nationwide Database Study

Objective Recommendations on the timing of Legionella urinary antigen tests for community-acquired pneumonia patients differ among guidelines in Japan, the United States, and European nations. We therefore evaluated the association between the timing of urinary antigen tests and in-hospital mortality in patients with Legionella pneumonia. Methods We conducted a retrospective cohort study using the Diagnosis Procedure Combination database, a nationwide database of acute care inpatients in Japan. Patients who underwent Legionella urinary antigen tests on the day of admission formed the tested group. Patients who were tested on day 2 of admission or later or were unexamined formed the control group. We performed a propensity score matching analysis to compare in-hospital mortality, length of hospital stay and duration of antibiotics use between the two groups. Results Of the 9,254 eligible patients, 6,933 were included in the tested group. One-to-one propensity score matching generated 1,945 pairs. The tested group had a significantly lower 30-day in-hospital mortality than the control group (5.7 vs. 7.7%; odds ratio, 0.72; 95% confidence intervals, 0.55-0.95; p=0.020). The tested group also showed a significantly shorter length of stay and duration of antibiotics use than the control group. Conclusion Urine antigen testing upon admission was associated with better outcomes in patients with Legionella pneumonia. Urine antigen tests upon admission may be recommended for all patients with severe community-acquired pneumonia.

Urinary Antigen Testing for Respiratory Infections: Current Perspectives on Utility and Limitations

Pneumonia is a leading cause of hospitalization and death due to infection worldwide. Streptococcus pneumoniae and Legionella pneumophila remain among the most commonly identified bacterial pathogens. Unfortunately, more than half of all pneumonia cases today lack an etiologic diagnosis due to limitations in traditional microbiological methods like blood and sputum cultures, which are affected by poor sample collection, prior antibiotic administration, and delayed processing. Urinary antigen tests (UATs) for S. pneumoniae and L. pneumophila have emerged as powerful tools for improving the diagnosis of bacterial respiratory infections, enabling physicians to administer early directed therapy and improve antimicrobial stewardship. UATs are simple, rapid, and non-invasive diagnostic tests with high specificity (>90%) and moderate sensitivity (<80%). The potential impact of urinary antigen testing is especially significant for respiratory infections caused by Legionella. While all recommended community-acquired pneumonia (CAP) therapies are adequate for treating pneumococcal pneumonia, only certain antibiotics are effective against Legionella. Delayed therapy for Legionella is associated with worse clinical outcomes, which underscores the importance of rapid diagnostic methods like UATs. Despite their potential impact, current American Thoracic Society and Infectious Diseases Society of America (ATS/IDSA) guidelines argue against the routine use of urinary antigen testing for S. pneumoniae and L. pneumophila, except in patients with severe CAP and those with epidemiological risk factors for Legionella. Further research is necessary to evaluate the impact of early targeted treatment due to positive UAT results, as well as optimal strategies for UAT utilization. The purpose of this review is to summarize the UATs available for bacterial respiratory infections, describe current guidelines on their usage, and assess their impact on clinical outcomes and targeted therapy.

Sequence-based typing of clinical and environmental Legionella pneumophila isolates in Shenyang, China

INTRODUCTION

We performed SBT (sequence-based typing) on clinical and environmental Legionellapneumophila isolates in Shenyang (China). We analyzed and compared the results with those obtained by PFGE (pulsed field gel electrophoresis).

METHODS

Twenty-two L. pneumophila isolates were collected from two patients with L. pneumophila infection, two hospitals, and 13 office buildings. There were two clinical isolates, one strain isolated from domestic tap water, another from shower water and 18 strains from cooling tower water. All these isolates were analyzed by SBT and PFGE methods.

RESULTS

The 22 isolates were divided into 7 types by SBT. Five isolates belonged to novel sequence types (ST2345, ST2344, ST2406, ST2407, and ST2408) and one isolate belonged to ST328. The STs were not obtained for two of the isolates. The remaining 14 isolates belonged to ST1. PFGE typing divided the 22 isolates into 14 pulsotypes. The main pulsotype was SYC, which included seven isolates.

CONCLUSION

Both typing methods showed that predominant clonal lines exist in the Shenyang region, with high levels of genetic polymorphisms. Five novel STs were identified, indicating a unique genetic composition of L. pneumophila strains in this region, which are significantly different from those found in other environmental water systems in the world.

Case report: fatal pneumonia caused by new sequence type Legionella pneumophilia serogroup 1

INTRODUCTION

Legionnaires' disease is caused by Legionella bacteria, and commonly manifests as pneumonia and has a high fatality rate.

PATIENT CONCERNS

This case study reports on the fatal incident of a patient, initially diagnosed with pneumonia, and subsequently diagnosed with Legionnaires' disease caused by a new sequence type (ST) of Legionella.

DIAGNOSIS

It is speculated that the patient acquired Legionnaires' disease from a contaminated water source. Legionnaires' disease was diagnosed using the Legionella urinary antigen assay and bacterial cultures of respiratory secretions; Legionella pneumophilia Type 1 was also identified through serological testing. Sequence-based typing of the cultured bacterium revealed it to be a previously unidentified species, and it was named ST2345 new-type.

INTERVENTIONS

In addition to the treatment of Legionnaires' disease, blood samples taken on the second day of admission showed a co-infection of Candida tropicalis, which was treated with anti-fungal treatment. The patient improved after a week, however, on the seventh day of administration lower respiratory secretions showed the growth of Klebsiella pneumonia, indicative of ventilator-associated pneumonia.

OUTCOMES

Despite active treatment, the patient passed away due to multiple organ failure. As this was a fatal case, further research is needed to determine whether the critical condition of this case was related to the virulence of the novel Legionella strain.

CONCLUSION

A key finding of this study is that treatment for suspected Legionnaires' disease must be administered rapidly, as infection with Legionella may give rise to secondary pathogenic infections.

Sequence-based typing of clinical and environmental Legionella pneumophila isolates in Shenyang, China

INTRODUCTION

We performed SBT (sequence-based typing) on clinical and environmental Legionellapneumophila isolates in Shenyang (China). We analyzed and compared the results with those obtained by PFGE (pulsed field gel electrophoresis).

METHODS

Twenty-two L. pneumophila isolates were collected from two patients with L. pneumophila infection, two hospitals, and 13 office buildings. There were two clinical isolates, one strain isolated from domestic tap water, another from shower water and 18 strains from cooling tower water. All these isolates were analyzed by SBT and PFGE methods.

RESULTS

The 22 isolates were divided into 7 types by SBT. Five isolates belonged to novel sequence types (ST2345, ST2344, ST2406, ST2407, and ST2408) and one isolate belonged to ST328. The STs were not obtained for two of the isolates. The remaining 14 isolates belonged to ST1. PFGE typing divided the 22 isolates into 14 pulsotypes. The main pulsotype was SYC, which included seven isolates.

CONCLUSION

Both typing methods showed that predominant clonal lines exist in the Shenyang region, with high levels of genetic polymorphisms. Five novel STs were identified, indicating a unique genetic composition of L. pneumophila strains in this region, which are significantly different from those found in other environmental water systems in the world.

Pneumococcal and Legionella Urinary Antigen Tests in Community-acquired Pneumonia: Prospective Evaluation of Indications for Testing

BACKGROUND

Adult, community-acquired pneumonia (CAP) guidelines from the Infectious Diseases Society of America (IDSA) and American Thoracic Society (ATS) include indications for urinary antigen tests (UATs) for Streptococcus pneumoniae (SP) and Legionella pneumophila (LP). These recommendations were based on expert opinions and have not been rigorously evaluated.

METHODS

We used data from a multicenter, prospective, surveillance study of adults hospitalized with CAP to evaluate the sensitivity and specificity of the IDSA/ATS UAT indications for identifying patients who test positive. SP and LP UATs were completed on all included patients. Separate analyses were completed for SP and LP, using 2-by-2 contingency tables, comparing the IDSA/ATS indications (UAT recommended vs not recommended) and UAT results (positive vs negative). Additionally, logistic regression was used to evaluate the association of each individual criterion in the IDSA/ATS indications with positive UAT results.

RESULTS

Among 1941 patients, UATs were positive for SP in 81 (4.2%) and for LP in 32 (1.6%). IDSA/ATS indications had 61% sensitivity (95% confidence interval [CI] 49-71%) and 39% specificity (95% CI 37-41%) for SP, and 63% sensitivity (95% CI 44-79%) and 35% specificity (95% CI 33-37%) for LP. No clinical characteristics were strongly associated with positive SP UATs, while features associated with positive LP UATs were hyponatremia, fever, diarrhea, and recent travel.

CONCLUSIONS

Recommended indications for SP and LP urinary antigen testing in the IDSA/ATS CAP guidelines have poor sensitivity and specificity for identifying patients with positive tests; future CAP guidelines should consider other strategies for determining which patients should undergo urinary antigen testing.

Urinary antigen testing in community-acquired pneumonia in adults: an update

INTRODUCTION

Community-acquired pneumonia (CAP) continues to be a leading cause of hospitalization and mortality worldwide. Streptococcus pneumoniae and Legionella pneumophila remain the major etiological agents and are responsible for a significant proportion of CAP mortality. Among diagnostic tests for CAP, urine antigen detection of S. pneumoniae and L. pneumophila is widely accepted due to the simplicity of collection and the rapidity of the test results. Areas covered: This comprehensive review outlines the urinary antigen tests available, discusses their sensitivity and specificity, and assesses the usefulness of their results as the basis for targeted therapy. Expert commentary: There have been advances in urine antigen detection tests for patients with CAP. New methodologies show greater sensitivity, detect S. pneumoniae and L. pneumophila in a single test, and also detect pneumococcal serotypes. In addition, urine antigen detection tests have shown a high specificity, which means that a positive result practically indicates the causative pathogen of CAP. Therefore, a positive result can lead to a targeted therapy that is likely to improve patient outcomes and reduce the risk of resistance and adverse events. However, well-designed studies are needed to evaluate the usefulness of urine antigen detection tests with regard to clinical outcomes.

Diagnosis and treatment of community-acquired pneumonia in adults: 2016 clinical practice guidelines by the Chinese Thoracic Society, Chinese Medical Association

Community‐acquired pneumonia (CAP) in adults is an infectious disease with high morbidity in China and the rest of the world. With the changing pattern in the etiological profile of CAP and advances in medical techniques in diagnosis and treatment over time, Chinese Thoracic Society of Chinese Medical Association updated its CAP guideline in 2016 to address the standard management of CAP in Chinese adults. Extensive and comprehensive literature search was made to collect the data and evidence for experts to review and evaluate the level of evidence. Corresponding recommendations are provided appropriately based on the level of evidence. This updated guideline covers comprehensive topics on CAP, including aetiology, antimicrobial resistance profile, diagnosis, empirical and targeted treatments, adjunctive and supportive therapies, as well as prophylaxis. The recommendations may help clinicians manage CAP patients more effectively and efficiently. CAP in pediatric patients and immunocompromised adults is beyond the scope of this guideline. This guideline is only applicable for the immunocompetent CAP patients aged 18 years and older. The recommendations on selection of antimicrobial agents and the dosing regimens are not mandatory. The clinicians are recommended to prescribe and adjust antimicrobial therapies primarily based on their local etiological profile and results of susceptibility testing, with reference to this guideline.

Multiplex real-time PCR assay for Legionella species

Legionella pneumophila serogroup 1 (sg1) accounts for the majority of infections in humans, but other Legionella species are also associated with human disease. In this study, a new SYBR Green I-based multiplex real-time PCR assay in a single reaction was developed to allow the rapid detection and differentiation of Legionella species by targeting specific gene sequences. Candidate target genes were selected, and primer sets were designed by referring to comparative genomic hybridization data of Legionella species. The Legionella species-specific groES primer set successfully detected all 30 Legionella strains tested. The xcpX and rfbA primers specifically detected L. pneumophila sg1-15 and L. pneumophila sg1, respectively. In addition, this assay was validated by testing clinical samples and isolates. In conclusion, this novel multiplex real-time PCR assay might be a useful diagnostic tool for the rapid detection and differentiation of Legionella species in both clinical and epidemiological studies.

Current and emerging Legionella diagnostics for laboratory and outbreak investigations

Legionnaires' disease (LD) is an often severe and potentially fatal form of bacterial pneumonia caused by an extensive list of Legionella species. These ubiquitous freshwater and soil inhabitants cause human respiratory disease when amplified in man-made water or cooling systems and their aerosols expose a susceptible population. Treatment of sporadic cases and rapid control of LD outbreaks benefit from swift diagnosis in concert with discriminatory bacterial typing for immediate epidemiological responses. Traditional culture and serology were instrumental in describing disease incidence early in its history; currently, diagnosis of LD relies almost solely on the urinary antigen test, which captures only the dominant species and serogroup, Legionella pneumophila serogroup 1 (Lp1). This has created a diagnostic "blind spot" for LD caused by non-Lp1 strains. This review focuses on historic, current, and emerging technologies that hold promise for increasing LD diagnostic efficiency and detection rates as part of a coherent testing regimen. The importance of cooperation between epidemiologists and laboratorians for a rapid outbreak response is also illustrated in field investigations conducted by the CDC with state and local authorities. Finally, challenges facing health care professionals, building managers, and the public health community in combating LD are highlighted, and potential solutions are discussed.