Legionnaire’s Disease

As many of you may have heard, recently there have been several cases of Legionnaire’s Disease diagnosed at UAB Hospital in Downtown Birmingham, Alabama.  I thought that for this week’s topic, I would give some background information about this condition and the causative pathogen for this disease.

Legionnaire’s Disease is a type of pneumonia brought about by an infection of a bacterium from the Legionella genus.  These organisms can be found in virtually any source of water, and are likewise transferred through inhalation of water droplets that contain the pathogen, not person to person.  The disease has an incubation time of two to ten days and is characterized by symptoms that are similar to other types of bacterial pneumonia which may include fever, headache, and nonproductive cough.  The individuals at the highest risk of infection for this disease include the elderly, smokers, and those who are immunocompromised, while those with a healthy immune system either fight off the bacteria and never get Legionnaire’s Disease or only get a milder case.¹

When you combine the facts, it is clear how an outbreak can easily happen in a hospital environment.  Many of the individuals have a weakened immune system, and if exposed to the Legionella bacterium in the water supply, they can easily contract this disease. 

Diagnosis of this disease is accomplished through a variety of means such as special fluorescent stains, DNA detection, and even a urine antigen test.  Since this organism is difficult to grow and isolate on standard media, special media must be utilized that can aid in its culture.¹

Hopefully this information helped in the understanding of this disease.

References:

1.      Tillie, Patricia M (2014). Legionella. Bailey and Scott’s Diagnostic Microbiology 13^th Edition (pp. 424-430). St. Louis, Missouri: Elsevier Mosby.

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.

Bacteremia and Blood Culture Part 1

For my first official entries, I thought it would be good to review over some of the information and activities we have covered so far in the course during the first couple of weeks, particularly bacteremia and blood cultures.  This will be a two part post, with the second half being posted next week.

Under normal circumstances and in healthy individuals, the blood system within your body should not contain organisms of any kind, and is considered to be a sterile body fluid.  Inevitably, due to incidences such as cuts, IV catheters, and infections of other body sites, pathogens such as bacteria or viruses can gain access into the blood stream.  The immune system is able to normally rid itself of these invasions in most healthy adults.  Unfortunately for individuals with a weak or compromised immune system, this can lead to a more serious complication.  Since the blood system is basically a highway throughout the body, if undiagnosed or untreated this can lead to systemic infections that can affect various organs and may lead to death. 

The terminology used to describe these conditions is based on the responsible organism and the severity of the infection.  Some of these include bacteremia, viremia, and fungemia which indicate the presence of bacteria, viruses, and fungi in the blood, respectively.  Septicemia is another term that is used to indicate that pathogens are present and reproducing within the blood stream. 

Welcome

Welcome to Infection of Knowledge!  This blog was created for the purpose of giving an inside view to the world of the Microbiology/Infectious Disease scientific discipline from the perspective of a graduate student throughout the course of an entire semester.  The subject matter posted here will cover various issues ranging from current events related to the field to interesting topics or information discussed in some of the coursework and laboratory exercises that I am currently undertaking. Hopefully, this information can help others to better understand the biological medical laboratory, and shed light on some of the lesser known facts related to this area of expertise.