Bacteremia and Blood Culture Part 2

The presence an infection in the blood is detected through the use of blood cultures.  For this procedure, blood is collected into sterile bottles containing a media which when metabolized by any present organism will result in the release of carbon dioxide.  This alters the pH of the substrate on the bottom of the container, causing a change in color which is generally measured by a sensor in an automated incubator, usually monitored up to a five day span.  Once this color change is detected, the medical technologist will receive an alarm indicating which bottle has tested positive for an increase of carbon dioxide so that further culture and identification of the pathogen can occur.

In order to achieve this, blood from the culture bottle is inoculated onto media for isolation/identification of the organism as well as Gram stained so that a preliminary identification can occur and general treatment can begin.  After 24 hours the resulting growth on the media can be observed and processed using rapid testing such as oxidase or catalase to obtain a final identification.  If a final identification cannot be determined at this step, identification systems can be utilized to identify the pathogen.  Upon final identification, antibiotic susceptibility testing can be initiated in order to provide a more precise antibiotic treatment that can be used to rid the patient of the infection.

This is a brief description of the lecture information and laboratory exercise we performed during the first week of our course.  I processed a blood culture bottle by using this method of isolation culture, rapid testing, and identification systems, and was able to determine that the patient in question had bacteremia resulting from Escherichia coli.  I found this exercise to be quite informative, and hopefully my description can aid in the understanding of how this process works in a medical laboratory setting.