Infectious Disease: Microbiology

Yi-Wei Tang, MD, PhD, F(AAM), FIDSA
Chief and Member, Clinical Microbiology Service
Member, Infectious Diseases Service

The Microbiology Service in the Department of Clinical Laboratories is staffed by a Chief, Director of Molecular Microbiology, Manager, Supervisors, Technologists, Technicians and Clerical Personnel; and is open at all hours, including weekends. The Microbiology Service, with its laboratories of bacteriology, mycobacteriology, mycology, parasitology, virology, serology, molecular biology, and molecular epidemiology is located one floor below the Infectious Disease Service, and continuous interaction between the two Services occurs.

The primary goal of the clinical microbiology laboratory is to determine the presence and nature of microorganisms in material from patients. This information, when correlated with clinical impressions and other laboratory test results, helps in diagnosing infection and frequently guides specific therapy. Patients whose immune mechanisms have been suppressed by drug therapy or by underlying disease often present with problems in the diagnosis and management of infections that differ from those encountered in patients with intact immune systems. In the immunosuppressed patient the usual hallmarks of infection such as leukocytosis and antibody response may be absent; thus the microbiology laboratory plays a fundamental role in the diagnosis of infection. Also, because infections in the immunosuppressed patient may be caused by unusual organisms whose identification requires special techniques, close communication between the physician and the laboratory is important.

Classic methods used to demonstrate microorganisms in a specimen submitted to the laboratory have included visualization techniques with stains and wet preparations, culture, and non-cultural methods involving immunologic and immunochemical techniques. The potential value of the clinical microbiology laboratory has been enhanced during the past few years, owing to the introduction of molecular diagnostic techniques, computers and automated equipment. Occurring at the same time, the emergence of new infections and the re-emergence of older ones, together with generalized trends toward increased resistance of bacteria to antibiotics, have led to circumstances in which the use of classic microbiologic techniques may not be adequate for the proper diagnosis of infecting microorganisms. At Memorial Sloan Kettering, the Microbiology Laboratory now includes a molecular epidemiology section that types organisms of nosocomial interest, a virology laboratory that employs both direct fluorescent microscopy and shell-vial assays for rapid virus detection, and a molecular microbiology laboratory that uses various amplification technologies for rapid organism detection. All of these services work best, once again, when laboratory personnel have close working relationships within the hospital with clinicians, epidemiologists, and other medical staff, and outside the hospital with centralized health agencies, reference laboratories, and research organizations.