Purpose of review: In many cases, the specific pathogen responsible for a respiratory infection is not identified and can lead to improper medical treatment, increased duration of illness, and possibly contributes to the development of antibiotic resistance. Molecular-based diagnostic methodologies have significantly improved our ability to identify common respiratory pathogens; these techniques are not useful, however, when a novel pathogen is responsible for the infection and clinicians must rely on differential diagnosis for the treatment of patients.
Recent findings: New pathogens previously not associated with human infections have been identified in the past few years. In addition, new strains of bacteria and viruses have emerged as the causative agents of pneumonia and acute respiratory distress. Protozoans and saprophytic fungi, which are not normally associated with respiratory infection, have also emerged as respiratory pathogens particularly in individuals with AIDS or in those who are otherwise immunocompromised.
Summary: This review discusses the recent literature on newly described respiratory pathogens as well as opportunistic pathogens that can infect the respiratory system of immunocompromised individuals. The studies referenced here reveal the need for expanded laboratory tests and highly trained microbiologists in clinical laboratories worldwide.