Microbiological Diagnosis of Respiratory Illness

Comparing sputum, nasopharyngeal swabs, and combined samples for respiratory bacterial detection using multiplex PCR

Respiratory tract infections are major global health issues that require rapid and accurate diagnostic methods. Multiplex quantitative PCR (qPCR) is commonly used for pathogen detection in respiratory samples. However, the optimal specimen selection for detecting bacterial pathogens is not well-explored. We evaluated the detection rates of respiratory bacteria from nasopharyngeal swabs (NPS), sputum, and combined NPS and sputum samples using multiplex qPCR (Allplex PneumoBacter Assay, Seegene). Paired NPS and sputum samples from 219 patients with acute respiratory symptoms admitted to Korea University Anam Hospital were analyzed. qPCR was performed to detect seven respiratory bacteria: Bordetella parapertussis, Bordetella pertussis, Chlamydophila pneumoniae, Haemophilus influenzae, Legionella pneumophila, Mycoplasma pneumoniae, and Streptococcus pneumoniae. Combined NPS and sputum samples (n = 92) were created from 46 pairs of positive and 46 pairs of negative signals for NPS-alone and sputum-alone samples. Sputum samples (44.3%; 97/219) had a significantly higher positivity rate compared to NPS samples (21.0%; 46/219) (P < 0.001). The 92 combined samples identified a total of 65 bacterial nucleic acids. The detection rate for the combined samples was 86.2% (56/65), which was comparable to that of sputum alone (89.2%; 58/65) and higher than that of NPS samples (50.8%; 33/65). Combining NPS and sputum samples for PCR testing may offer an alternative for bacterial pathogen detection, providing rates comparable to those of sputum alone and greater sensitivity than that of NPS alone. This combined approach could be a cost-effective method to maximize diagnostic yield, reduce the need for multiple tests, and improve the management of respiratory infections.

IMPORTANCE

This study offers important insights into refining diagnostic strategies for respiratory bacterial infections using multiplex PCR. This study finds that combining sputum and nasopharyngeal swabs into a single tube could serve as an effective alternative for detecting respiratory bacteria in adults with acute respiratory illness.

Rapid Molecular Diagnostics of Pneumonia Caused by Gram-Negative Bacteria: A Clinician's Review

With approximately half a billion events per year, lower respiratory tract infections (LRTIs) represent a major challenge for the global public health. Among LRTI cases, those caused by Gram-negative bacteria (GNB) are associated with a poorer prognostic. Standard-of-care etiologic diagnostics is lengthy and difficult to establish, with more than half of cases remaining microbiologically undocumented. Recently, syndromic molecular diagnostic panels became available, enabling simultaneous detection of tens of pathogen-related and antimicrobial-resistance genetic markers within a few hours. In this narrative review, we summarize the available data on the performance of molecular diagnostics in GNB pneumonia, highlighting the main strengths and limitations of these assays, as well as the main factors influencing their clinical utility. We searched MEDLINE and Web of Science databases for relevant English-language articles. Molecular assays have higher analytical sensitivity than cultural methods, and show good agreement with standard-of-care diagnostics regarding detection of respiratory pathogens, including GNB, and identification of frequent patterns of resistance to antibiotics. Clinical trials reported encouraging results on the usefulness of molecular assays in antibiotic stewardship. By providing early information on the presence of pathogens and their probable resistance phenotypes, these assays assist in the choice of targeted therapy, in shortening the time from sample collection to appropriate antimicrobial treatment, and in reducing unnecessary antibiotic use.

Guidelines for Antibiotics Prescription in Critically Ill Patients

How to cite this article: Khilnani GC, Tiwari P, Mittal S, Kulkarni AP, Chaudhry D, Zirpe KG, et al. Guidelines for Antibiotics Prescription in Critically Ill Patients. Indian J Crit Care Med 2024;28(S2):S104-S216.

Bacterial pathogens from lower respiratory tract infections: A study from Western Rajasthan

Respiratory tract infections are the most common diseases that are associated with social burden for the patient. Western Rajasthan has cases of Cystic fibrosis due to migrant population. The dry and dusty environment has led to prevalence of silicosis and COPD. As per IDSA (2018) guidelines, patients attending Out-Patient Department do not need microbiological investigations for lower respiratory tract infections (LRTI) except for influenza and tuberculosis.