Conventional Culture Based Methods in Microbiological Diagnostics

The traditional microbiological diagnostic assays include microscopy and micro-bial culture techniques as well as the detection of antigens or toxins. The culture-based procedures are complemented by serological methods using immunoassays for the detection of pathogen-specific antibodies in blood or cerebrospinal fluid. All these methods can be limited by poor sensitivity, nongrowing or slow-growing or poorly viable organisms, narrow detection windows, complex interpretation, immunosuppression of the patient, antimicrobial therapy, high levels of backgrounds, and nonspecific cross-reactivity. Nonetheless, microbial cultures produce valuable epidemiological data, revealing new, uncharacterized, or atypical microbes and yielding intact or infectious organisms for further study. For this reason, the role of traditional assays continues to be an important one [16, 17]. This is particularly true of antimicrobial susceptibility testing of bacterial patho gens, which is one of the primary functions of a diagnostic microbiology laboratory. Individual results have important therapeutic implications for the patient. The detection of resistant bacteria further provides a fundamental basis for infection control measures and antimicrobial surveillance systems. Antibiotic resistance is routinely determined in diagnostic laboratories using culture-based methods, e.g., disc diffusion assay or broth dilution. These traditional methods, however, are largely confined to rapidly growing bacteria and depend on the expression of antibiotic resistance genes under laboratory culture conditions.

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