The Infectious Diseases Society of America (IDSA) Foundation recently hosted a webinar on the continuous challenges of non-COVID respiratory tract infections as part of their Dr. John G. Bartlett Memorial Education Series. The World Health Organization (WHO) reports respiratory tract infections as the leading cause of disease burden and lower respiratory tract infection (LRTI) as the third leading cause of death worldwide .
The webinar, available on-demand here, focuses on lower respiratory tract infections and is divided into three presentations. In the first talk of the webinar, Dr. Donna Wolk discusses screening and diagnosis of lower respiratory tract infections and surveillance options. In the second presentation Dr. Leila Hojat discusses the pathogenesis, etiology and clinical manifestation of pneumonia. The third topic covers antibiotic decision-making and the importance of vaccines, presented by Dr. Maryrose Laguio-Vila.
This blog summarizes the highlights from the first talk. The second and third talk of the webinar is covered covered here and here.
In the first presentation of the webinar Dr. Wolk discusses screening and diagnosis of lower respiratory tract infections and surveillance options. Sputum specimens are among the most common sample types that clinical laboratories receive from patients with suspected lower respiratory tract infections. However, compared to other better quality sample types such as those obtained from endotracheal aspirate and bronchoalveolar lavage, only 20-60% of sputum samples are adequate for diagnosis. Dr. Wolk explains that microscopic examination of a Gram-stained smear of the specimen for LRTI features such as polymorphonuclear leukocytes (PMNs), alveolar macrophages, and minimal squamous epithelial cells frequently reveals whether the specimen is acceptable for diagnosis. For example, the presence of PMNs usually indicate infection or inflammation in an immunocompetent patient and the observation of squamous epithelial cells signals oral contamination in the sample, which may contain opportunistic pathogens that could misdirect proper treatment. In general, as Dr. Wolk mentions, specimen quality is important for acceptability and extent of culture work-up. The two most widely used Gram stain scoring systems, the Quality (Q) score system and the Q234 system, help improve culture prediction of infection.
While culture is commonly used to support diagnosis, determine causative pathogens, and check antibiotic sensitivity, limitations exist. For example, normal (pharyngeal) flora can overgrow in cultures, antibiotic usage before culture may derail culture results, some pathogens are difficult to detect through standard culture methods or do not grow in the presence of other pathogens.
The emergence of molecular diagnostic panels has the advantage of allowing for fast identification of common pathogens and may allow for quicker and better target therapy, says Dr. Wolk. Studies have reported variable accuracy as compared to cultures. However, the lack of standardization for culture and molecular diagnostics methods complicates direct performance comparison. Additionally, more evidence-based studies depicting actionable results from molecular diagnostic panels are needed to further bolster and assure reimbursement.
In the last section of her talk, Dr. Wolk focuses on surveillance. In general, surveillance can be active or passive, utilizing culture or molecular diagnostics. Special media can be formulated to detect only pathogens under surveillance, such as Pseudomonas spp. or Acinetobacter baumannii. Chromogenic media can be utilized for methicillin-resistant Staphylococcus aureus (MRSA) or gram negative multidrug resistant organism (MDRO) surveillance. Besides culture, molecular surveillance is a powerful alternative that can be designed to detect the genetic material of any pathogen of interest.
A blog summarizing the highlights of the second and the third talks is available here and here.
The webinar is available on-demand here to learn more about screening, diagnosis, and surveillance of respiratory tract infections as well as etiology, clinical manifestation, and antibiotic stewardship.
About the Speaker
Dr. Wolk is the Division Chief, Molecular and Microbial Diagnostics and Development, at Geisinger Medical Laboratories. She is the founder and principal investigator for Geisinger’s Microbial Diagnostics and Innovation Center. She is a diplomate of the American Board of Medical Microbiology, a board-certified medical laboratory scientist, and a professor at the Geisinger Commonwealth School of Medicine.
 Avendaño Carvajal L, Perret Pérez C. Epidemiology of Respiratory Infections. Pediatric Respiratory Diseases. 2020 Feb 1:263–72. doi: 10.1007/978-3-030-26961-6_28. PMCID: PMC7120591.