Blood Culture and Swabs Test PDF

Pathological analyses Lec.7 By:Dr: Baydaa Hussein Blood culture and Swabs test What Is a Blood Culture Test A blood culture is a test that checks samples of blood for the presence of disease-causing germs like ba...

Pathological analyses Lec.7 By:Dr: Baydaa Hussein Blood culture and Swabs test What Is a Blood Culture Test A blood culture is a test that checks samples of blood for the presence of disease-causing germs like bacteria and fungi. Some bacteria prefer oxygen (aerobes), while others thrive in a reduced oxygen environment (anaerobes). Blood cultures are usually drawn into two types of media to detect both types of bacteria. If your blood culture is positive, the specific bacteria causing the infection will be identified and antibiotic susceptibility testing will be done to tell your doctor which antibiotics will be effective for treatment. If yeasts are causing the infection, treatment will be given that is appropriate for fungal infections. Infections of the bloodstream are caused most commonly by bacteria (bacteraemia), but can also be caused by a fungus (fungaemia) or a virus (viraemia). If your immune defences and white blood cells cannot contain an infection at its source, for example, in the bladder for a urinary tract infection, the infection may spread to your bloodstream and be carried throughout your body. Endocarditis, an inflammation and infection of the lining of the heart and/or of the heart valves, can result from a bloodstream infection. Purpose of a blood culture Blood cultures are ordered when your doctor suspects you may have a blood infection. It’s important to test for blood infections because they can lead to serious complications. One such complication of a blood infection is sepsis. In sepsis, the pathogens that are causing the infection in your bloodstream interfere with your body’s normal defenses and prevent your immune system from working properly. The pathogens also produce toxins that can damage your organs. The results of the test can help your doctor determine which specific organism or bacteria is causing the blood infection and how best to combat it. Symptoms of blood infection and sepsis You should call 911 or visit a doctor immediately if you’re experiencing any symptoms of a blood infection. These include:  shaking chills  moderate or high fever  rapid breathing  increased heart rate or palpitations 1  Pathological analyses Lec.7  excessive fatigue  muscle aches and headache Without treatment, a blood infection can progress to its most severe stage, sepsis. The symptoms of sepsis include those listed above, as well as signs of damaged organs. The following are additional symptoms of sepsis:  confusion  decreased urine  dizziness  nausea  mottled skin As the infection progresses, more serious complications of sepsis may develop. These can include:  inflammation throughout your body  formation of many tiny blood clots in your smallest blood vessels  a dangerous drop in blood pressure  failure of one of more organs Blood cultures are also drawn more frequently in newborns and children with fever who may have an infection but don’t have the typical signs and symptoms of sepsis. Older adults are also at higher risk for blood infections. Blood culture for other conditions A blood culture can also be used to detect conditions such as endocarditis. Endocarditis is a condition that occurs when bacteria in your bloodstream sticks to your heart valves. It can belife-threatening. How is the sample collected for testing? Usually, two blood samples are collected from different veins to increase the likelihood of detecting bacteria or fungi if they are present in the blood. Multiple blood samples help to differentiate true pathogens, which will be present in more than one blood culture, from skin bacteria that may contaminate one of several blood cultures during the collection process. Skin Preparation 1. Wash your hands with soap and water and then dry. 2. Clean any visibly soiled skin on the patient with soap and water and then dry. 3. Apply a tourniquet and palpate to identify vein. 4. Clean the skin with an alcohol wipe and allow to dry. If a culture is being collected from a central venous catheter, disinfect the access port with alcohol swab and allow to dry. 2  Pathological analyses Lec.7 Blood Collectioin Needle and syringe method 1. Wash and dry your hands again or use alcohol hand rub and apply clean examination gloves (sterile gloves not necessary) 2. Insert needle – do not palpate again after cleaning. 3. Collect the sample and release the tourniquet. 4. Cover the puncture site with an appropriate dressing. 5. If blood is being collected for other tests always inoculate the blood culture bottles first. 6. Inoculate the blood into the culture bottles. Do not change the needle between sample collection and inoculation. Inoculate the orange blood culture first and then the green one. Ensure that as least 5-10ml is inoculated into each bottle. 7. Discard the needle and syringe in a sharps container at the point of use. 8. Remove gloves and wash hands with soap and water. 9. Record the procedure in the patients medical notes including indication, date, time, site of venepuncture and any complications. 3  Pathological analyses Lec.7 Container  Label the bottle with the patient information.  Do not remove the barcode sticker from the bottle – this is essential for laboratory processing.  Do not cover the bottle barcode with the patient information sticker – please use the blank space provided. Specimen requirements Adult  1 x aerobic bottle (green top)  1x anaerobic bottle (orange top) Paediatric  1 x paediatric bottle (yellow top) Minimum volume Adult  Aerobic (green top): 8-10ml  Anaerobic (orange top): 8-10ml Paediatric  Paediatric (yellow top): 5ml Number and timing of samples: For most patients two blood culture sets are recommended. A second or third set taken from a different site not only increases yield but also allows recognition of contamination. Volume of blood Blood culture volume is the most significant factor affecting the detection of organisms in bloodstream infection. There is a direct relationship between blood volume and yield, with approximately a 3% increase in yield per mL of blood cultured. False negatives may occur if inadequate blood culture volumes are submitted. 4  Pathological analyses Lec.7 Turnaround time Final reports issued  Negative: 5-10 days  Positive within 48 hours: 4 days (organism dependent) Interim reports issued  Adult: Negative at 48 hours  Paediatric: Negative at 36 hours Positive: all positive bottles are phoned to the requesting source at the time of positivity and an interim microscopy report issued. What are medical swabs for? The swab is a medical device used for the collection of biological samples from the human body and allows for the transport and preservation of the sample. Some of the most common applications of swabs are:  For the isolation of microorganisms in culture media.  For inoculation of plates by seeding on the surface of the medium, as in the case of antibiograms.  For the preparation of smears, after taking the samples to be observed under a microscope.  For sampling of pre-operative cleaning All pathological specimens must be treated as potentially infectious and local written laboratory protocols should be followed for the safe handling and transportation of specimens. Specimen should be collected in sterile containers with close fitting lids to avoid contamination and spillage. All specimen containers must be transported in a double sided, self-sealing polythene bag with one compartment containing the laboratory request form and the other the specimen. Transport medium may be used to preserve microorganisms during transportation: Charcoal medium improves the isolation of bacteria by neutralising toxic substances such as naturally occurring fatty acids found on the skin. Swab head and shaft The swab head can be made of natural fibres (such as cotton) or inorganic and inert fibres such as viscose, polyester, and flocked fibres. Each material offers different characteristics to be assessed by the healthcare professional depending on the intended use. the swab shaft can also be made of various materials: wood, polystyrene, or aluminium, and is chosen according to the sampling point. In the case of flocked swabs, the shaft is made of polystyrene and there are different shafts and head shapes depending on their use: 5  Pathological analyses Lec.7 nasopharyngeal, urethral, paediatric. Principle : Swab test is the counting of total number of aerobic bacterial, yeasts and molds onany surface. Procedure : 1. A cotton Swab with normal saline( 0.9 % NaCl) and placed in a suitable test tube or screw cap test tube. The mouth of the test tube is closed with cotton plug and rapped with aluminum foil. 2. The test tube containing the swab is then sterilized by autoclaving at 121 OC , 15 psi, pressure for 15 min. 3. Alternativily pre sterilised cotton swab of HI- media make can also be used.In this case,moisten the swab with sterile normal saline before using the swab. 4.Wear handgloves and take out the swab carefully from the test tube and swab the surface to be checked. 5.The area of the swab should be approximately 10 Sq. cm. 6.Replace the swab immediately in the test tube and close. Types of Swabs: −Throat Culture  Used to diagnose or rule out strep throat  Test procedure:  Your health care provider will insert a special swab into your mouth to take a sample from the back of the throat and tonsils. −Urine Culture  Used to diagnose a urinary tract infection and identify the bacteria causing the infection  Test procedure:  You will provide a sterile sample of urine in a cup, as instructed by your health care provider  −Sputum Culture 6 Pathological analyses Lec.7 Sputum is a thick mucus that is coughed up from the lungs. It is different from spit or saliva.  Used to help diagnose bacterial infections in the respiratory tract. These include bacterial pneumonia and bronchitis.  Test procedure:  You may be asked to cough up sputum into a special cup as instructed by your provider; or a special swab may be used to take a sample from your nose. −Stool Culture Another name for stool is feces.  Used to detect infections caused by bacteria or parasites in the digestive system. These include food poisoning and other digestive illnesses.  Test procedure:  You will provide a sample of your feces in a clean container as instructed by your  healthcare provider. −Wound Culture  Used to detect infections on open wounds or on burn injuries  Test procedure:  Your health care provider will use a special swab to collect a sample from the site of your wound. Culture of swabs and the Sensitivity test Culture- a grown bacteria and sensitivity is an anaerobic test to do the Sensitivity analysis, also called susceptibility testing, to determine the “sensitivity” of the bacteria to an antibiotic. It helps the doctor in finding the most effective antibiotic to kill an infecting microorganism. The test is performed on a sample of pus swab to scale the level of Culture of the pathogenic organism in the pus swab. It also determines the ability of the drug to kill the bacteria. Procedure for culture and Sensitivity Sensitivity analysis steps involve: A bacterial sample is collected by swabbing the infected area. Samples can be taken from: blood, urine, sputum (spit), inside the cervix, a pus- containing wound. 1. The culture will be spread on a special growing surface and allowed to grow and multiplyresulting in the formation of a large group of bacteria known as colonies. 2. The colonies will be subjected to different antibiotics for further testing. 3.These colonies respond differently with respect to the antibiotics to which they are exposed: ► Susceptible, state that they can’t grow if the drug is present. This means the antibiotic is effective against the bacteria. ►Resistant state that the bacteria can grow even if the drug is present. This is a sign of an ineffective antibiotic. ►Intermediate state that a higher dose of the antibiotic is needed to prevent growth. 7 Pathological analyses Lec.7 Protozoan organisms Cryptosporidium ► sppngestion of oocyst (sporulated), some species are zoonotic (e.g. bovine fecal contamination Entamoeba histolytica ► fecal-oral transmission of cyst, not amoeba Giardia lamblia ►ingestion of water containing deer or beaver feces Toxoplasa gondii ►ingestion of uncooked/undercooked pork/lamb/goat with Toxoplasmabradyzoites, ingestion of raw milk with Toxoplasma tachyzoites, ingestion of contaminated water food or soil with oocysts in cat feces that is more than one day old. Trichomonas vaginalis ►sexually transmitted infection – only trophozoite form (no cysts) 3-Sputum culture Mucus: production in the respiratory tract is a normal process. It is secreted from goblet cells found in the surface epithelium lining the airways of the respiratory tract and from seromucous glands in the connective tissue layer beneath the mucosal epithelium. 8  Pathological analyses Lec.7 The primary functions of mucus are to: Humidify air passing through the respiratory tract;  Trap dust particles, bacteria and other inhaled debris;  Destroy bacteria. Sputum expectoration is abnormal and there is always an underlying pathological cause. Such causes include:  Effects of smoking on the airway;  Infection (viral, bacteria or fungal);  Chronic lung disease, such as chronic obstructive pulmonary disease and asthma;  Cystic fibrosis. Secretions in the lower airways create an ideal environment for the growth of bacteria and the presence of infection can increase and change the nature of mucus leading to the need to expectorate and cough. Principles of sputum specimen collection The aim of sputum collection is to identify the bacterial, viral or fungal cause of a suspectedinfection and its sensitivities to antibiotics. A specimen is indicated if patient has:  Clinical signs of infection including a productive cough and purulent sputum;  Signs of systemic infection;  Pyrexia of unknown origin It is difficult to accurately assess the amount of sputum produced but it may be described by its colour and consistency. It is important to consider the characteristics of sputum as part of an overall patient assessment. Sputum may be described using the following terms ,which can aid diagnosis of the cause:  Mucoid – containing or resembling mucous;  Purulent – containing pus;  Mucopurulent – containing pus and mucous;  Frothy – visible froth;  Viscous – thick and sticky;  Blood-stained – visible blood present. 9 Pathological analyses Lec.7 Yellow, orange or green sputum is commonly associated with bacterial or viral infection. Red sputum indicates the presence of blood and may suggest tuberculosis or cancer, or infection, particularly in bronchiectasis and fungal growths such as aspergilloma in immunocompromised patients. Expectorating large amounts of white frothy sputum may be a sign of pulmonary oedema. Sputum samples: Sputum samples can be obtained using a non-invasive or invasive method andideally should be collected before antibiotics are started. Invasive methods include oropharyngeal or endotracheal suctioning; these are used with patients who are intubated. A sputum trap is connected to the suction catheter to collect the sputum. It is important to check that the sample contains sputum, as samples contaminated with oropharyngeal secretions and saliva are difficult to interpret and can be misleading. Contamination of the sample can result in inappropriate or delayed treatment. 10 Pathological analyses Lec.7 11