Blood Culture and Sensitivity Test

Blood Culture

Definition: A blood culture is a medical laboratory test used to detect bacteria and fungus in personal blood. Under typical circumstances, the blood does not harbor microorganisms. Their presence can signify a bloodstream infection like bacteremia or fungemia, which in severe instances may lead to sepsis.

Introduction to Blood Culture Sensitivity Test: A blood culture test is a crucial diagnostic procedure used in the field of medicine to identify and diagnose infections caused by bacteria or fungi present in a patient's bloodstream. This test plays a vital role in helping healthcare professionals determine the specific microorganism responsible for the infection, allowing for targeted treatment and improved patient outcomes.

The procedure involves the collection and incubation of a small sample of the patient's blood in a specialized culture medium. This medium provides an optimal environment for the growth of microorganisms if they are present in the bloodstream. Over a period of several days, the sample is closely monitored for the development of bacterial or fungal colonies. Once growth is observed, the microorganisms are identified through various laboratory techniques, such as staining and microscopy, and sometimes genetic testing.

Blood culture tests are typically ordered when a patient exhibits symptoms of a systemic infection, such as high fever, chills, rapid heartbeat, and low blood pressure. These symptoms may suggest the presence of bacteria or fungi circulating in the bloodstream, potentially originating from an infected organ, tissue, or medical device.

Blood Culture

Indication of Blood Culture:

· Enteric fever
· Septicemia
· Bacteramia
· Meningitis
· Pyrexia of unknown origin
· Bacteria infective endocarditic
· Osteomyelitis
· Brucellosis
· Pneumonia
· Endocarditis

Media used in blood culture: Solid agar media-

· Blood Agar media
· Macconkey agar media
· Chocolate Agar media
· Mollar-Hinton agar media

Liquid if media:

· Bile broth
· Glucose broth
· Tryptic-soya broth
· Thioglycate broth
· Brain heart infusion broth.

Composition of Blood Agar Media:

Preparation of blood if media:

Organism of blood if media:

· Staphylococci species
· Streptococci species
· Pseudomonas
· Salmonella species
· Escherichia coli
· Anaerobic organisms

The procedure of blood culture:

Blood culture can be done in three processes:

1. Traditional Method- Using liquid media on biphasic media.

2. Lytic Method - After processing in lytic solution in solid media.

3. Automated -Very rapid (within 6 hours)

Traditional Method-Procedure:

Blood Sample: The test involves drawing a sample of the patient's blood. This blood sample is collected under sterile conditions to minimize the risk of contamination.

5 ml of blood is collected aseptically and is inoculated directly into the liquid medium. medium is 1:10 the inoculated media is then incubated at 37 ° c for 3-7 days. The growth of bacteria in the broth is determined by the turbidity of the broth. When the medium becomes turbid, a few drops of broth are then inoculated aseptically in solid media like blood agar media, McConkey agar media, and chocolate agar media. bacteria in agar media are then identified by observing the colony morphology and biochemical characteristics.

Blood culture

Lab diagnosis:

1. Specimen collection: blood 15-20 cc in an aseptic way (skin wash is done with 2% iodine)

2. Culture:

Solid if media-

· Blood Agar media
· Macconkey agar media
· Chocolate Agar media
· Mollar-Hinton agar media

Liquid if media:

· Bile broth
· Glucose broth
· Tryptic-soya broth
· Thioglycate broth
· Brain heart infusion broth.

Sub-Culture:

· Subculture should be done at blood agar, McConkey agar, and chocolate agar media at 37 ° c temperature for 48 hours.

· E.Coli-Pin color colony
· Streptococcus Pneumonia
· Salmonella color colony.

Antibiotic sensitivity test: Method-Diffusion disc method

3. Bio-chemical Test (microbiology)

· Catalase test
· Coagulase test
· Sugar fermentation test
· Oxidase Test (Positive eudomonase)

Staining should be done after centrifuging the blood with an anticoagulant EDTA sample taken from a buff coat for gram staining and acid-fast staining.

Report: Once the culture and sensitivity testing is complete, the laboratory generates a report detailing the type of microorganism found in the blood and a list of antibiotics or antifungal medications that are effective against it. The report also indicates which drugs are ineffective, helping Medical technologists avoid prescribing antibiotics that won't work.

Treatment Adjustment: Armed with the information from sensitivity testing, Medical technologists can adjust the patient's treatment plan to use the most effective antimicrobial agents. This is crucial for managing serious bloodstream infections and preventing the development of antibiotic resistance.

Monitoring: Patients with bloodstream infections often require close monitoring and may need further blood cultures to ensure that the treatment is effective in clearing the infection.

Blood culture and sensitivity tests are essential diagnostic tools in the management of severe infections. They enable Medical technologists to tailor treatment plans to the specific microorganism causing the infection, improving the chances of a successful outcome and reducing the risk of antibiotic resistance.

Conclusion: Blood culture" is a medical test that helps determine the presence of any bacteria or pathogens in the blood by taking a blood sample and examining it. It provides initial information about the presence of infection in the blood and its relation to normal blood. The results of blood culture are the first step in understanding the presence of bacteria or pathogens. If any microorganisms are found, their nature and any susceptibility to common treatments are determined using this information.

Detailed information about the discovered pathogen is provided, including its nature and the type of microorganism. Blood culture results also provide important clues for the doctor's necessary treatment decisions. Your doctor will review and interpret your blood culture test results and recommend any necessary treatment. This test helps determine the appropriate treatment for your condition and allows for oral discussion about the nature of your medical condition.

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