History of Infectious Disease Testing
Up until the early 1900s, there was little physicians could do to treat people with infectious diseases. The advent of culture testing changed that by enabling doctors to identify pathogens within the body that cause infection.
Traditional Blood Culture Testing [1900s]
The techniques for testing and identifying microbes responsible for infectious diseases in the body were major breakthroughs for modern science and healthcare. This method of identifying the source of infection from a culture involves observing the microbe, its physical characteristics, and reactions in biochemical tests.
While technology and science have advanced, the method of testing for infectious diseases has largely remained the same. Today’s clinical microbiology laboratories conduct traditional culture tests to select, isolate, and then identify pathogenic organisms.
The Limitations of Cultures:
Time-consuming trial-and-error process to rule out a number of species until only one remains
Accuracy, because some microbes cannot be cultured at all
Contaminated blood cultures are common
Costly, require expensive lab time and labor to conduct testing
Polymerase Chain Reaction (PCR) 
In some infection samples, bacteria may exist only in small concentrations making them very hard to isolate and identify. Polymerase chain reaction is a process used to "amplify" the DNA, enabling the identification and measurement of specific genes or organisms.
The PCR technique, developed in 1984 by Kary Mullis, has revolutionized life sciences, becoming an essential technique in conducting clinical diagnostics, forensics, and genetic engineering.
Real-Time PCR [1990s]
Using the same process of amplification, Real-time PCR monitors and measures reactions in “real time” rather than at the end.
The advent of new sequencing technologies, with techniques such as PCR and microarrays, has reduced analytical processing time to a matter of hours. The newly developed technologies have arrived at a time when antibiotic resistance has become a serious problem for today’s clinicians.