Chapter 2 : Conventional Blood Culture Methods

Abstract:

Chapter 1 took us on a time-travel journey spanning the evolution of blood cultures. All the experimentation and discovery since the 17th century have led to a common understanding of which microorganisms cause bloodstream infections and what essential nutrition is required to grow and recover them from blood. Even today, blood culture remains the best option to determine microbial causes of sepsis. Detection of microbial nucleic acids in blood by PCR or sequencing may not represent the presence of viable organisms (see chapter 13 on the blood microbiome). Often, manual culture methods are used as a reference standard for newer iterative protocols like current-generation automated blood culture systems ( 1 ). While the routine use of manual blood culture methods in modern diagnostic microbiology laboratories in 2017 is no longer commonplace, the practice remains quite prevalent in the developing world where purchase and maintenance of automated blood culture instruments are both unaffordable and impractical. But in the developed world, manual blood culture protocols often serve as a backup plan if automated systems experience problems. The comedian Mitch Hedberg once said, “An escalator can never break: it can only become stairs.” The same holds true for automated blood culture systems. Regardless of how blood cultures are performed, however, the same set of parameters must be attained to ensure optimal microbial recovery. The list of best practice benchmarks includes the following and can also be found in chapter 10: