Blood CultureGROUP MEMBERS:

Aimen NiazRafia Hafeez

Adeena ShafiqueZujaja tul MisbahSammia Rehman

Syeda Fatma H. BukhariPRESENTED BY:Adeena ShaiqueSammia Rehman

Syeda Fatma H. Bukhari

WHAT IS BLOOD CULTURE

A blood culture is the laboratory test in which blood is injected into bottles with media to determine the presence of microorganism invaded in blood of patient

PURPOSE OF BLOOD CULTURE

DIAGNOSIS PROGNOSIS THERAPY

BACTERAEMIA VS. SEPTICAEMIA

The presence of bacteria in the blood is called Bacteraemia Bacteraemia occurs in • Typhoid fever• Brucellosis• Leptospirosis• Endocarditis.

Severe and life-threatening form of bacteraemia is called SepticaemiaSeptic shock is due to Gram negative bacilli

PATHOGENS ISOLATED FROM BLOODCULTURES

BACTERIA• E. coli• S. epidermidis• Neisseria meningitidis• Salmonella Typhi• S. aureus

FUNGI• Candida albicans • yeasts• Histoplasma

capsulatum

NOTE:Blood does not have a normal microbial flora.

Day 1Collect blood and inoculate culture media

Collection of blood:• Blood should be collected before antimicrobial

treatment has started• Collect the blood as the temperature of patient

begins to rise• At least two specimens (collected at different times)

should be cultured.• About 20 ml of blood is taken from adults.• Blood from neonates should be collected from a peripheral vein not

from the umbilical vein. • 1–2 ml of blood is enough to detect the presence of bacteria in

children’s blood.

Choice of culture media

• Diphasic blood culture medium• Columbia agar and broth• Commercially produced culture media

NOTE: Choice of media depends on the bacterial disease that is suspected. Some bacteria grow well in a particular medium, others do not.

Aseptic blood collection and dispensingtechnique

• Wash hands.• Disinfect the venepuncture site with 70% ethanol and

2% tincture of iodine.• Decontaminate blood culture bottle tops.• Using a sterile syringe, withdraw 20ml blood.• Dispense 10 ml into the culture medium.• Incubate the inoculated media as soon as possible. Incubate upto 4 weeks when brucellosis is suspected Incubate upto 14 days for anaerobic infections

Aseptic Technique

Examining the blood culture:1- CENTRIFUGE: a sample of EDTA anticoagulated venous blood or heparinized capillary blood and make smears of the buffy coat layers.

2- STAIN:• _ Gram smear: for Gram positive and Gram negative bacteria detection• _ Ziehl-Neelsen smear: To detect AFB (acid fast bacteria)• _ Giemsa or rapid Field’s smear: To detect borreliae, or parasites such as

trypanosomes, malaria parasites, and microfilariae.

3- DRY the smears, fix with absolute methanol for 2 minutes and stain by the appropriate staining technique.

Day 2 and Onwards 3- REPORT• Diphasic culture (Columbia agar and broth) Check for microbial growth, indicated by colonies growing on the agar slope, usually beginning at the agar-broth interface. • Colonial appearances Colonies of staphylococci, S. Typhi, brucellae, and most coliforms can usually be seen easily, whereas colonies of S. pneumoniae, Neisseria species, S. pyogenes, and Y. pestis are less easily seen.• Pseudomonas and Proteus species produce a film of growth on the agar.• When growth is present:– Subculture on blood agar, chocolate agar, and MacConkey agar.– Incubate the blood agar and MacConkey agar plates aerobically and the chocolate agar plate in a carbon dioxide atmosphere (candle jar).– Examine a Gram stained smear of the colonies.• Depending on the bacteria seen, test the colonies further (e.g. for coagulase, catalase,

oxidase, urease, and motility).

• Subculture on lactose egg yolk milk agar and incubate anaerobically

Large Gram positiverods (C. perfringens)

• Subculture the colonies on Kligler iron agar

motile, urease and oxidase negative Gram negative rods are isolated

• Suspect Brucella species and send for identification.

• Mark it as ‘High Risk’.

catalase positive,Gram negative coccobacilli are isolated

NOTE: When there is no growth, wash slope of diphasic culture. Reincubate cultures and subculture.

• Examine toluidine blue smear (diphasic culture)

• Examine thioglycollate culture• Subculture and examine microscopically• Incubate subculture anaerobically

Contamination of Blood Culture

Collection of blood

During subculturing

Frequent contaminants include:•Commensal staphylococci, micrococci, and diphtheroids•Contaminants from the environmentsuch as species of Bacillus or Acinetobacter.

Other possibilities

• Occasionally in immunocompromised patients, organisms usually considered ‘contaminants’ may be pathogenic, especially fungi.

• Contamination is indicated when an organism is recovered from only one bottle when it should have grown in both thioglycollate broth and the diphasic culture medium or when a mixed microbial flora is isolated.

Another use…

• Severe and often fatal reactions can be caused by the transfusion of contaminated blood.

• The bacteriological investigation of a transfusion reaction is as follows:

• Appearing unusually dark in colour• Containing small clots• The plasma appearing red, or unusually turbid

(examine after centrifuging a sample of the blood).Visible signs

• At room temperature• At 4°C

Varied subculturing

• Motility Test• Gram stained smear of the plasmaTests