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Clinical Application and Interpretation of Antimicrobial Susceptibility Testing
Vanderbilt University Medical Center, Nashville, Tennessee, USA
Charles W. Stratton
Charles W. Stratton教授
Introduction
As the 19th century drew to a close, the work of Joseph Lister ushered in the dawn of the antimicrobial era. Lister was among the first scientists to understand that microorganisms might be involved in human disease. Lister studied the inhibitory effect of various chemicals on the growth and viability of bacteria and directly applied this knowledge to medicine by using phenol to sterilize surgical instruments. Following this early example of infection control, the next step was to use such chemicals to attack microbes causing infection. As the use of antimicrobial agents over the 20th century progressed, their clinical successes were truly amazing and resulted in these agents being hailed as miracle drugs. During the second half of the 20th century, medicine enjoyed almost complete control over bacterial infection.
Although it seems paradoxical that these miracle drugs have the potential to destroy the miracle, this is what is happening due to the emergence of resistance. In the last decade, antimicrobial resistance rapidly has become a major threat to the efficacy of these agents, strongly suggesting that the remarkable success of antimicrobial agents is not going to continue indefinitely. Therefore, as the 20th century now represents the antimicrobial era, the 21st century may ultimately represent the post-antimicrobial era.
Role of the Susceptibility Testing
The increasing problem with the failure of antimicrobial therapy due to resistant microorganisms brought many long-standing problems with susceptibility testing into focus. Susceptibility testing has long been used to identify resistant microorganisms. Indeed, a British microbiologist, Sir Alexander Fleming, was among the first to perform an in vitro susceptibility test. The introduction of sulfonamides in 1935 and penicillin in 1942 initiated the antimicrobial era. Within a decade of antimicrobial therapy, the correlation of clinical results with laboratory susceptibility tests was first questioned. Others have continued to ask this question. Another British microbiologist, David Greenwood, perhaps framed this important question the best when he asked, “In vitro veritas?” in regards to antimicrobial susceptibility tests and their clinical relevance. The clinical application and interpretation of antimicrobial susceptibility testing has become an important issue and must be appreciated by clinicians and laboratory personnel alike.
New Resistance Challenges
There are a number of examples of new resistance challenges that clinicians and clinical microbiology laboratories have addressed in the past several decades. These include community-acquired methicillin-resistance Staphylococcus aureus, decreased vancomycin susceptibility of S. aureus, extended-spectrum beta-lactamase in enteric Gram-negative bacilli, Klebsiella pneumoniae carbapenases,and beta-lactam resistance in Streptococcus pneumoniae. Each of these examples as created problems for the clinician in terms of treating patients and for the clinical microbiology laboratory in terms of identifying these resistant pathogens.
