Clinical Microbiology: Past, Present, and Future

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Abstract
During the last two decades of the 19th century, a plethora of bacteria were isolated and designated etiological agents of human infectious diseases. As with many instances at the in- terface between cause and effective therapy, the further char- acterization of these alleged pathogens remained in the hands of a few devoted investigators until drugs with therapeutic potential became available. This vague period before the ad- vent of proper cures for infections explains the shadowy origin of clinical or diagnostic microbiology. But, as R. Porter has stated, "history should be rooted in detail and as messy as life itself" (8); this is an undeniable description of the history of clinical microbiology, long the stepchild, frequently denied le- gitimacy, among the many siblings that constitute the science of microbiology. Yet the practice of clinical microbiology is the application of knowledge gained to the betterment of the hu- man condition, the goal of clinical microbiologists. To appre- ciate the history of clinical microbiology, it must be said— without malice or rancor—that this practical side has earned us the disdain of those who emphasize theory exclusively. Our working behind the scenes is misinterpreted by colleagues in related fields whose egos require constant applause. Our role is belittled, but the wondrous ingenuity of our test objects un- derlines our contributions to health, disease diagnoses, and therapy. The evolution of clinical microbiology is a response to clin- ical needs. This can take the form of a technical innovation garnered from the armamentarium of science in general or a reflection of advances in anti-infective therapy demanding rec- ognition of microbial etiologies that now respond to therapeu- tic intervention. But this history is also a reflection of the political climate, of the perceived threats posed by an emerging field to more established organizational and professional enti- ties. While this struggle greatly influenced the development of clinical microbiology as a distinct specialty, it is sufficiently controversial to be omitted from this essay. One could propose that clinical microbiology got its start when various stains became available to indicate the presence of different organisms. The Gram stain helped divide the vast array of bacteria in various specimens into categories based, in addition to the staining reaction, on the anatomy of the organ- ism and its source. The acid-fast stain aided in the recognition of mycobacteria, while the Albert stain suggested the presence of Corynebacterium diphtheriae, leading to the administration of a specific antiserum, an emerging therapy at the start of the 20th century that was usually used on the basis of clinical presentation. A variety of selective, supplemented, and en- riched culture media became available for isolation, permitting more rapid recognition of the presumptive presence of a sig- nificant organism. Antisera were put to use as therapies and to identify isolates. The Quellung reaction became a standard task of interns and resident house officers, performed to iden- tify the type of pneumococcus present and guide specific serum therapy, in addition to avoiding serum sickness by obtaining careful histories of previous treatment with equine antibodies against other etiologic agents. The advances in the grouping and typing of streptococci, salmonellae, and shigellae, the sep- aration of Staphylococcus aureus on the basis of the coagulase reaction, and the growing awareness of the need for safe water and uncontaminated food items established the need for lab- oratories to assume these responsibilities. It was only logical that microbiology should join endeavors such as chemistry, hematology, and serology under the rubric of clinical pathol- ogy. Differential media especially designed to sequester species increased dramatically during Word War II; military hospitals developed clinical microbiology sections devoted not only to recognizing agents endangering the health of troops in camps, in battle, and in foreign environments but also to assessing the responses of certain of the microorganisms isolated to several sulfonamides and that hitherto unknown agent, penicillin. The subsequent explosion of antimicrobial agents—streptomycin,