Specimen Collection for Microbiology Studies PDF

Specimen Collection for Microbiological Studies Dr. Basma Samir (MD) Blood COLLECTING BLOOD FOR CULTURING POINT CARE PROTOCOL Critical Considerations Physicians order blood for culturing when the patient’s condition needs evaluate whether there is bacteremia and septicemia. If the spe...

Specimen Collection for Microbiological Studies Dr. Basma Samir (MD) Blood COLLECTING BLOOD FOR CULTURING POINT CARE PROTOCOL Critical Considerations Physicians order blood for culturing when the patient’s condition needs evaluate whether there is bacteremia and septicemia. If the specimens are collected without any of point care and aseptic precautions, blood cultures turn out to be either Sterile when inappropriate specimen is inoculated or Contaminated when careless in collection persists Circumstances in which blood cultures are especially ordered: known or suspected sepsis, meningitis, osteomyelitis, arthritis, endocarditis, peritonitis, pneumonia, and fever of unknown origin. Important Considerations Blood is one of the most important specimens received by the microbiology laboratory for culture. Culture of blood is the most sensitive method for detection of bacteremia or fungemia. Quality of the specimens submitted to the microbiology laboratory is critical for optimal specimen evaluation. Bacteraemia in adults is generally intermittent. Important Considerations The first step in appropriate collection remains with optimal collection and ideal antiseptic precautions using the standard decontamination protocols. Decontaminate skin surface. Use 70-95% alcohol and 2% chlorhexidine or 1-2% tincture of iodine (TIO) in the modern concept use Betadine to prepare the site. Allow a contact time of two minutes to maximize the antiseptic effect. Important Considerations Multiple blood cultures, each containing large volumes of blood, are required to detect bacteraemia. Prior to initiation of antimicrobial therapy, at least two sets of blood cultures taken from separate venipuncture sites should be obtained. The technique, number of cultures, and volume of blood are more important factors for detection of bacteraemia than timing of culture collection; these are discussed further in the following sections. Technique Careful technique is critical to avoid contamination of blood culture media by normal skin flora during the process of collection. This is important because normal bacterial skin flora can also cause systemic disease, and in some circumstances blood culture contamination can make it difficult to distinguish between false-positive results and true infection. Measures to reduce contamination include effective disinfection of the venipuncture site and avoiding blood culture collection through existing intravenous line, which certainly interferes with the decision whether it is a contaminant or true pathogen.  Apply tourniquet to the extremity and identify phlebotomy site. Preferred: Use locally available chlorhexidine solution. Cleanse and scrub the site with 2-3 alcohol swabs. Allow to dry for at least 30 seconds. Wear sterile gloves. Use a firm scrubbing motion for 30 seconds to disinfect the site. A 10 cm area of skin should be disinfected. Allow the site to dry at least 30 seconds before venipuncture.  Povidone-iodine swabs permit more decontamination than chlorhexidine alone. Allow to dry for a at least 30 seconds to allow antiseptic effect If using iodine product, clean patient's skin with alcohol to remove excess iodine (to prevent iodine burns). Use alcohol pad to cleanse patient's skin, using a circular motion starting at the site and moving outward. Repeat twice. Allow to dry at least 30 seconds.  Do not touch the venipuncture site after skin preparation. If palpation is absolutely necessary, sterile gloves must be applied immediately prior to palpation. Insert needle into vein and withdraw appropriate amount of blood. Draw blood cultures prior to drawing other blood samples. Try to keep the dominant hand sterile. Remove the alcohol pad from the top of the culture bottles.  Inoculate each culture bottle with exactly 8-10 ml of blood, using previously marked indicator line. Blood specimens from infants and younger children are less than adult blood specimens. Remove the tourniquet and butterfly needle from the site and cover with gauze dressing. Apply pressure to site as needed.  If absolutely necessary to draw from a central catheter site, utilize the site that has been most recently inserted (ruling out catheter sepsis). Label the culture bottles in the presence of the patient. Do not place label over bar-coded area of the bottle. Fill out Microbiology-routine lab slip. Indicate suspected diagnosis. Include date and time of collection. Document that cultures were obtained on appropriate nursing form.  Send specimens to the laboratory as soon as possible. Never refrigerate blood culture specimens. Send second set of blood cultures using the same procedure as above. If a different peripheral site is possible, the second set may be drawn immediately. If using the same site, wait at least 10 minutes for the second set, and if possible (i.e. not waiting to give antibiotics) draw a third set 1-3 hours later. In order to rule out specific diagnoses, more specific blood culture procedures may be necessary. Suspected catheter sepsis Draw two blood culture sets. One set is obtained from the suspected catheter. At the same time, a second set must be from a separate peripheral site. Time of collection should be indicated for both specimens. If the catheter is removed, a section of about 1 inch in length from an intradermal portion is to be cut aseptically and sent to Microbiology Lab in a dry sterile container. Do not send catheter tip without sending concomitant blood cultures. Acute endocarditis Draw 2-3 culture sets from separate sites within 30 minutes of each other and before beginning antimicrobial therapy. Begin therapy after cultures are obtained. Subacute endocarditis Draw 2-3 blood culture sets on day 1, spaced 30-60 minutes apart. This may help to document a continuous bacteremia. If all are negative additional sets can be drawn on days 2 and 3 (no more than 4 sets in a 24 hour period). Immediate antibiotics are less important than establishing a specific microbial diagnosis. Fungal Cultures Candida spp. - If a physician orders fungal cultures, follow routine procedure for bacterial cultures as described above. Bone Marrow Physicians should wear gowns, masks, and gloves during specimen collection. Prepare skin as for blood cultures. Drape the surrounding skin with sterile linen. Aspirate the marrow percutaneously using a sterile needle and syringe. Transfer 3-5 ml for each: Bacterial test into a blood culture bottle - do not send in a Heparin tube. AFB culture and fungal culture into a mycobacteria/fungal blood culture bottle. Transport specimens immediately at ambient temperature.