DIAGNOSTIC VALUE OF MICROBIOLOGICAL TEST DETERMINING THE RESPIRATORY AGENTS

Abstract

Lower respiratory tract infections (LRTI), including acute and chronic bronchitis, community-acquired pneumonia, hospital-acquired pneumonia, and pneumonia inimmunocompromised hosts or pneumonia in patientswith other heath problems, are the most common respiratory infectious illnesses. According to Centers for Disease Control and Prevention, lower respiratory tract infections are resposible for 5–10% all-cause mortality. Changes in the characteristics of the population, such as the number of individuals over age 65, the number of individuals in nursing homes, and the number of patients with immunocompromising conditions, have increased the number of individuals at risk, the number of infections that occur and the variety of pathogens known to cause infection. The role of the microbiology laboratory in the diagnosis of milder cases of acute bronchitis and community-acquired pneumonia has been challenged. Even for seriously ill patients controversy exists over the diagnostic value ofmany specimens obtained routinely, as well as those that are obtained viamore invasive procedures such as bronchoscopy. The clinical laboratory plays a vital role in the diagnosis of these infections but faces numerous challenges due to the complexity of LRTIs, including specimen quality and diversity; contamination of specimens with oropharyngeal flora; a diverse pathogen population that includes bacteria, viruses, and fungi; and the complex pathophysiology of respiratory tract infections, especially in special populations. Five current questions in the clinical microbiology of LRTI were discussed: 1. What is the real value of the Gram stain of expectorated sputum? 2. What is the value of quantitative culture techniques on bronchoalveolar lavage (BAL) andmini-BAL specimens, endotracheal (ET) aspirates,
and transbronchial biopsy specimens? 3. What is the role of the clinical microbiology lab in the diagnosis of acute exacerbations of chronic bronchitis (AECB)? 4. How do we optimize the microbiological evaluation of cystic fibrosis (CF) patientswith exacerbations?