ABSTRACT
CLINICAL SPECIMENS IN THE MICROBIOLOGY LABORATORY Specimen Types Invasive procedures such as tissue biopsies, bronchoscopically obtained biopsies, bronchoalveolar lavages (BAL), and bronchial washing and brushing, and fluids obtained by thoracentesis and paracentesis, offer the best chance of the recovery of a pathogen. Moreover, specimens obtained from sterile body sites are most useful in identifying the causative organisms and less likely to be contaminants. In debilitated cancer patients an ideal diagnostic sample for isolation of the pathogen may be difficult to obtain. Even the most commonly submitted sterile body site specimen, peripheral blood, may be hard to obtain from immunocompromised patients. For some individuals, sputum cultures for respiratory infection workups, and blood obtained from central lines for blood cultures, may be the only specimens available. In disseminated infections, especially by fungal agents, the recovery of a pathogen from skin or mucous membranes is helpful in making a diagnosis. However, it is very important to adhere to strict criteria to exclude the contaminating normal flora from being considered as the actual pathogen(s).
Blood Cultures Cancer patients, especially patients with hematological malignancies, have altered microbial flora, owing to damage to anatomic barriers and to granulocytopenia and subsequent microbial invasion following intensive myelosuppressive therapy. All these factors increase the incidence of bacteremia and show a more morbid outcome in cancer patients. In view of the seriousness of bacteremic episodes, it is important to use the most efficient blood culture techniques, which offer a speedy and accurate isolation of the pathogens. The original traditional blood culture method, which used bottles containing enriched nutrient broth, and which entailed daily visual evaluation by the technologist, is labor-intensive and time-consuming.
