Culture & Sensitivity, Aerobic bacteria Blood 1 Aerobic, 1-Anerobic(Vitek 2 Compact)

Bacterial/ Viral

Report in 120Hrs

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No Fasting Required

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Identifies bacteria & antibiotic susceptibility.

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Culture & Sensitivity Aerobic Bacteria Blood - Comprehensive Medical Test Guide

Why is it done?
- Detection and identification of aerobic and anaerobic bacteria in bloodstream infections (bacteremia and sepsis)
- Diagnosis of systemic infections including endocarditis, osteomyelitis, and other serious infections
- Determination of antimicrobial susceptibility patterns to guide targeted antibiotic therapy
- Evaluation of patients with fever of unknown origin and clinical signs of sepsis
- Monitoring response to antimicrobial therapy in hospitalized patients
- Performed when patients present with symptoms such as fever, chills, hypotension, tachycardia, and altered mental status
- Essential in immunocompromised patients, post-surgical patients, and those with indwelling medical devices
Normal Range
- Normal Result: No growth or No organisms isolated after 5-7 days of incubation
- Interpretation: Normal findings indicate no bacteremia present; absence of blood-borne bacterial infection
- Positive Result: Growth of bacteria detected, with organism identification and colony count reported
- Contamination/Mixed Flora: Growth of skin commensals (Coagulase-negative Staphylococci, Corynebacterium, Bacillus); may indicate contamination but requires clinical correlation
- Units: Colony Forming Units per milliliter (CFU/mL) or qualitative growth assessment (rare, infrequent, occasional, frequent)
- Reference Values: Typically ≤ 15 CFU/mL considered negative; > 100 CFU/mL from single blood culture considered significant; multiple positive cultures with same organism strongly suggests true infection
Interpretation
- Organism Identification (via Vitek 2 Compact): Automated identification of bacterial species within 4-18 hours using biochemical testing and pattern recognition
- Antimicrobial Susceptibility Results: Reported as Susceptible (S), Intermediate (I), or Resistant (R) to tested antibiotics; guides appropriate antibiotic selection and dosing
- Clinical Significance of Common Pathogens: Staphylococcus aureus - serious pathogen associated with acute sepsis; consider endocarditis Staphylococcus epidermidis - evaluate as pathogen vs. contaminant based on clinical presentation Streptococcus pneumoniae - suggests pneumonia with bacteremia; meningitis risk E. coli & Enterobacteriaceae - often from urinary or GI sources; assess for sepsis severity Pseudomonas aeruginosa - nosocomial infection; higher mortality; critically ill patients Anaerobes (Bacteroides, Clostridium) - indicates intra-abdominal or polymicrobial infection
- Factors Affecting Results: Prior antibiotic therapy may reduce culture sensitivity Contamination during collection affects accuracy; proper skin antisepsis critical Volume of blood collected influences detection; minimum 10 mL recommended Time to processing affects viability; cultures should be incubated promptly Patient immune status affects bacterial load and detection probability Intermittent bacteremia may be missed if sampling occurs during non-bacteremic period
- Minimum Inhibitory Concentration (MIC) Values: Quantitative antibiotic resistance measurement; helps determine optimal antibiotic dosing, especially important for serious infections requiring high-dose therapy
- Multi-drug Resistant (MDR) Organisms: MRSA (Methicillin-resistant S. aureus), VRE (Vancomycin-resistant Enterococci), or ESBL-producing organisms reported separately; affects treatment and infection control measures
Associated Organs
- Primary Systems Affected: Circulatory/Cardiovascular system (bloodstream) Immune system (systemic inflammatory response) Multiple organ systems (in disseminated infection)
- Common Associated Conditions: Sepsis and septic shock Infective endocarditis (heart valve infection) Osteomyelitis (bone infections) Meningitis (CNS infection) Pneumonia with bacteremia Urinary tract infections with sepsis Intra-abdominal infections Device-related infections (prosthetic joints, catheters, pacemakers)
- Diseases This Test Helps Diagnose: Acute bacterial infections requiring urgent antimicrobial therapy Nosocomial (hospital-acquired) infections Healthcare-associated bloodstream infections Community-acquired infections with systemic manifestations Opportunistic infections in immunocompromised hosts
- Potential Complications of Positive Results: Septic shock with multi-organ failure Disseminated intravascular coagulation (DIC) Acute respiratory distress syndrome (ARDS) Renal failure Myocardial dysfunction Endotoxin/cytokine-mediated tissue damage Mortality rates 20-40% depending on organism and timeliness of treatment
- Organ-Specific Seeding Risks: Cardiac valves (endocarditis risk with streptococci and staphylococci) Central nervous system (meningitis, particularly with S. pneumoniae, N. meningitidis) Bones and joints (osteomyelitis, septic arthritis) Lungs (septic emboli, secondary pneumonia) Liver and spleen (splenic infarcts, abscess formation)
Follow-up Tests
- Repeat Blood Cultures: Obtained 24-48 hours after initial positive culture to assess response to therapy; persistence indicates inadequate treatment or source control
- Source-Specific Cultures: Urine culture (if UTI suspected as source) Cerebrospinal fluid culture (if meningitis possible) Sputum/bronchoalveolar lavage (if pulmonary source) Wound/abscess cultures Prosthetic joint aspirate cultures
- Imaging Studies: Echocardiography (TEE/TTE for endocarditis evaluation) CT scan (abdomen/chest for source identification and complications) MRI (osteomyelitis, spinal infections) Nuclear medicine imaging (FDG-PET for infection localization)
- Laboratory Monitoring Tests: Complete Blood Count with differential (WBC trends) Comprehensive Metabolic Panel (renal function, liver function, electrolytes) Lactate levels (tissue perfusion marker) Procalcitonin (bacterial infection marker, prognostic indicator) C-reactive protein (CRP) and ESR (inflammation markers) Coagulation studies (PT/INR, aPTT, fibrinogen - monitor for DIC) Blood glucose monitoring
- Antimicrobial Stewardship Follow-up: De-escalation to targeted antibiotics based on susceptibility results (typically within 48-72 hours) Antibiotic levels/therapeutic drug monitoring if applicable (vancomycin, aminoglycosides) Repeat susceptibility testing if clinical failure occurs
- Monitoring Frequency: Initial: Repeat blood cultures at 24-48 hours post-initial draw Ongoing: Daily clinical assessment until hemodynamically stable Long-term: Follow-up cultures as indicated for specific infections (e.g., endocarditis surveillance cultures) Typically continue antibiotic therapy for 7-28 days depending on organism and infection type
Fasting Required?
- Fasting Required: No - fasting is not required for blood culture collection
- Patient Preparation Requirements: No special fasting or dietary restrictions necessary Patient may eat and drink normally before collection No fluid restrictions required
- Critical Preparation - Skin Antisepsis: Proper skin cleansing is paramount to reduce contamination: Use chlorhexidine gluconate 0.5% with alcohol, povidone-iodine, or 70% isopropyl alcohol Cleanse venipuncture site for minimum 30 seconds in circular motion from center outward Allow to air dry completely (do not fan or blow dry) - critical for antiseptic effectiveness Do not touch site after antiseptic application Do not repalpate vein after skin cleansing Phlebotomist should wear clean gloves
- Collection Technique Requirements: Collect 10-30 mL of blood per culture bottle (typically 10 mL into aerobic and 10 mL into anaerobic bottles) Peripheral venipuncture preferred over line draws to reduce contamination Multiple sets from different sites recommended (increases sensitivity for true bacteremia) Immediate transport to laboratory at room temperature Do not refrigerate blood culture bottles
- Medications and Timing: Collect blood cultures BEFORE starting antibiotic therapy when possible (cultures drawn after antibiotics begun have reduced sensitivity) If patient already on antibiotics, document on requisition Do not discontinue or delay essential antibiotics pending culture results Peak bacteremia often coincides with fever spikes; collect during or just before temperature elevation if possible
- Special Populations: Neonates/infants: Consider transient bacteremia from maternal antibodies; follow institution-specific protocols Central line patients: Can collect from line but note site (risk vs. benefit assessment) Post-operative patients: Collect within 6 hours of fever onset for optimal yield

How our test process works!