1 / 35

Bacteremia

Bacteremia. MLAB 2434 –Microbiology Keri Brophy-Martinez. Definitions. Pseudobacteremia False bacteremia Contamination of a blood culture during or after collection. Definitions. Bacteremia – presence of bacteria in blood stream

tybalt
Download Presentation

Bacteremia

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Bacteremia MLAB 2434 –Microbiology Keri Brophy-Martinez

  2. Definitions • Pseudobacteremia • False bacteremia • Contamination of a blood culture during or after collection

  3. Definitions • Bacteremia – presence of bacteria in blood stream • Some conditions have a period of bacteremia as part of the disease process (ex. Meningitis, endocarditis) • Usually occurs due to a disruption of skin or mucosal barriers to bacterial invasion

  4. Classifications of Bacteremia • Classified by Site of Origin • Classified by Causative Agent • Classified by Place of Acquisition • Classified by Duration

  5. Classification by Site of Origin • Primary Bacteremia • Blood stream or endovascular bacterial invasion with no preceding or simultaneous site of infection with the same microorganism • Secondary Bacteremia • Isolation of a microorganism from blood as well as other site(s) • Fever of Unknown Origin (FUO) • Source unknown

  6. Classification by Causative Agent • Gram positive bacteremia • Gram negative bacteremia • Anaerobic bacteremia • Polymicrobial bacteremia

  7. Classification by Place of Acquisition • Community-acquired • Health-care acquired/Nosocomial • Defined as occurring 72 hours post admission

  8. Classification by Duration • Transient • Comes and goes • Usually occurs after a procedural manipulation (ex. Dental procedures) • Intermittent • Can occur from abscesses at some body site that is “seeding” the blood • Continuous Bacteremia • Organisms from an intravascular source that are consistently present in bloodstream

  9. Sepsis & Septicemia • Presence of active bacteria • Results from continuous bacteremia • Clinical signs and symptoms of bacterial invasion and toxin production • Apply the SIRS criteria • Systemic response to bacterial infection

  10. Bacteremia Complications • Septic shock • Results from body’s reactions to bacterial bi-products • Endotoxins: lipopolysaccharide • Exotoxins • Disrupts many body functions • Hemodynamic changes, decreased tissue perfusion and compromised organ & tissue function • Mortality 40% to 50%

  11. Bacteremia/Septicemia Risk Factors • Immunocompromised patients • Due to decrease in circulating neutrophils • Increased use of invasive procedures & indwelling devices • Disrupts normal flora • Age of patient • Young: defect in humoral immunity • Old: Decreased immune competency • Administration of drug therapy • Broad spectrum antibiotics decrease normal flora • Increase in antimicrobial resistance

  12. Sources of Bacteremia • Pericarditis and Peritonitis • Pneumonias • Pressure sores • Prosthetic medical devices • Total hip replacement • Skeletal system • Skin and soft tissue • Urinary Tract Infections

  13. Clinical Signs and Symptoms • Abrupt onset of chills, fever, or hypothermia and hypotension • Prostration (exhaustion/weakness) and diaphoresis (perspiration) • Tachypnea (rapid breathing) is an early sign of bacteremia • Delirium, stupor, agitation • Nausea, vomiting

  14. Clinical Signs and Symptoms (cont’d) • Laboratory Values in Bacteremia • Thrombocytopenia • Leukocytosis or leukopenia • Acidosis • Abnormal liver functions • Coagulopathy • DIC • Elevations in CRP, haptoglobin, fibrinogen, ESR, procalcitonin

  15. Specimen Collection • Positive blood cultures • Critical value • Physician correlates finding to clinical picture to verify septicemia • Best Practice • Collect specimen immediately PRIOR to rise in temperature • Collect PRIOR to antibiotic therapy

  16. Specimen Collection • Aseptic collection procedure is critical • Cleansing agents • Tincture of iodine (1-2%) • Leave on skin for 30 seconds • Povidine-iodine (10%) • Leave on skin 1.5 to 2 minutes • Chlorhexidine/ChloraPrep • Leave on skin for 30 seconds • 2% chlorhexidine gluconate + 70% isopropyl alcohol • Cleansing Technique • In concentric fashion, from inside to out • After cleaning, wait 1.5-2 minutes • Acceptable Contamination Rate • 1-3%

  17. Collection sites • Preferred • Peripheral venous • Arterial sites • Less common • Central venous catheters • Arterial lines

  18. Blood Collection Devices • Traditional set • Aerobic bottle • Selects for aerobic & facultative anaerobes • Anaerobic bottle • Selects for obligate anaerobes • ARD bottle (Antibiotic Removal Device) • Used when patient is on antibiotics prior to blood collection • SPS= Sodium polyanetholsulfonate

  19. Blood Collection Devices • Anticoagulants • SPS= Sodium polyanetholsulfonate • Function/Purpose • Anticoagulant • Neutralizes human serum • Prevents phagocytosis • Inactivates certain antimicrobial agents • SAS(sodium amylosulfate) • Similar to SPS, but less effective in neutralizing serum

  20. Specimen Collection:Blood Volume • Ideal ratio of blood: broth • 1:5 to 1:10 • Dilution aids in preventing the bactericidal effect of WBCs & complement • Volume Recommendations by Age • Younger than 10 years- 1 mL of blood for every year of life • Over 10 years- 20 mL • Short draw? • Inoculate anaerobic bottle first

  21. Specimen Collection:Frequency of Collection • Depends if bacteremia is transient, intermediate or continuous • General guidelines • Usually x2 from different body sites, when patient is spiking a fever • Endocarditis • 3 sets from 3 different sites within 1-2 hours of clinical presentation • Fever of Unknown Origin (FUO) • Initially 2 sets; 24-36 hours later, obtain 2 more

  22. Specimen Collection:Frequency of Collection • If a catheter-related bloodstream infection is suspected: • One set drawn peripherally • One set drawn via catheter

  23. Blood Culture Methods • Conventional Broth Systems • Aerobic broth contains soybean casein digest broth, tryptic or trypticase soy broth, Brucella agar or Columbia broth base • Anaerobic broth is usually the same as aerobic with addition of 0.5% cysteine in an aerobic environment • Must be subcultured and gram stained manually, at 12, 24 and 48 hours • Method not recommended due to risk of needlestick and contamination; not cost effective

  24. Blood Culture Methods (cont’d) • Biphasic Broth-Slide System • Agar “paddles” attached to top of bottle; includes CA, MAC, malt extract agars • Incubate at 35 OC for 7 days • Allows for blind subcultures • Closed system

  25. Blood Culture Methods (cont’d) • Lysis-Centrifugation Blood Culture Systems (Isolator) • Used in the recovery of Fungus and AFB • The Isolator is a special tube that contains saponin, a chemical that lyses cells and other anticoagulants • Approximately 7.5-10 ml of blood is placed in the tube, then centrifuged to concentrate microorganisms; sediment is subcultured to fungal and/or mycobacterial media

  26. Blood Culture Methods (cont’d) • Automatic Blood Culture Systems • BacTec 9000 Series • Fluorescent light is used to detect changes in CO2 levels

  27. Bactec 9000 Series

  28. Automatic Blood Culture Systems (con’t) • ESP( Extra Sensing Power) • Now VersaTREK • Measures consumption/production of gases; such as CO2 H2, N2 and O2 in the headspace of each bottle • Detects a change in pressure

  29. Automatic Blood Culture Systems (con’t) • BacT-Alert • Carbon dioxide production results in a pH change • pH change results in color change detected by system as “positive”

  30. Blood Culture Workup • Incubation times • Routine aerobic/anaerobic • 5-7 days • Endocarditis • 2 weeks • Brucellosis/Fungemia/HACEK • 21-28 days • Reporting results • Initial report is sent out at 24 hours • Final report is sent out at 5-7 days for all no growth specimens

  31. Blood Culture Workup • Positive Cultures • Gram stain the bottle to determine the morphology of the organism present • Call the results of the gram stain to the physician or nurse, including how many sets etc., so that antibiotic therapy can be initiated • Subculture to appropriate media • Identify organism and perform sensitivity testing

  32. Blood Cultures: Pathogens • Staphylococcus aureus • Streptococcus pneumoniae • Haemophilus influenza • Pseudomonas species • Neisseria species • Coagulase negative Staphylococcus species (immunocompromised) • Group B Streptococcus (infants) • Alpha hemolytic Streptococcus viridans group • Gram negative rods • Yeasts and molds • Anaerobes

  33. Blood Cultures: Contaminants • Coagulase negative Staphylococcus • Propionibacterium acnes • Alpha hemolytic Streptococcus viridans group • Bacillus species • Diphtheroids • Growth of multiple organism

  34. Treatment & Prevention • Treatment • Empirical treatment, initially, with broad spectrum antibiotic • Antisepsis therapy; physiological support, anticoagulation agents, glucocorticoids • Adjunctive measures; draining fluids, removing catheters • Prevention • Vaccines; S. pneumo, influenza, varicella

  35. References • Broyles, M. (2013, June). A Closer Look at Sepsis. ADVANCE for Medical Laboratory Professionals, 25(5), 12-13. • http://www.achats-publics.fr/Fournisseurs/BIOMERIEUX.htm http://www.bd.com/ds/productCenter/212536.asp • http://www.bd.com/ds/productCenter/445718.asp • http://www.temple.edu/medicine/microbiology_lab.htm • Kiser, K. M., Payne, W. C., & Taff, T. A. (2011). Clinical Laboratory Microbiology: A Practical Approach . Upper Saddle River, NJ: Pearson Education. • Mahon, C. R., Lehman, D. C., & Manuselis, G. (2011). Textbook of Diagnostic Microbiology (4th ed.). Maryland Heights, MO: Saunders.

More Related