Blood Culture And Sensitivity (Anerobic)(Vitek 2 Compact)

Bacterial/ Viral

Report in 120Hrs

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No Fasting Required

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Culture for anaerobic organisms in blood.

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Blood Culture And Sensitivity (Anaerobic)(Vitek 2 Compact) - Comprehensive Guide

Why is it done?
- Purpose: Detects and identifies anaerobic bacteria (organisms that grow without oxygen) in blood samples using the VITEK 2 Compact automated microbial identification system, and determines antibiotic susceptibility patterns
- Primary Indications: Diagnosis of bloodstream infections suspected to be caused by anaerobic bacteria; suspected septicemia or sepsis; fever of unknown origin; endocarditis; intra-abdominal infections; aspiration pneumonia; postoperative infections; immunocompromised patients with systemic infections
- Typical Timing: Performed when patient presents with clinical signs of systemic infection; during active fever episodes; before antimicrobial therapy initiation when possible; results typically available within 24-72 hours after positive culture detection
- Clinical Significance: Critical for selecting targeted antimicrobial therapy; anaerobic infections often polymicrobial and serious; includes organisms such as Bacteroides, Clostridium, Peptococcus, and Prevotella species
Normal Range
- Normal Result: NEGATIVE - No growth of anaerobic bacteria detected after 5-7 days of incubation; indicates blood is sterile and free from anaerobic pathogens
- Abnormal Result: POSITIVE - Growth detected; includes organism identification and susceptibility patterns; graded as 1+ to 4+ based on colony count
- Units of Measurement: Colony Forming Units (CFU/mL); qualitative growth description (1+ to 4+); Minimum Inhibitory Concentration (MIC) in micrograms/milliliter for antibiotic sensitivity
- Result Interpretation: Negative indicates no bacteremia; Positive indicates presence of anaerobic bacteremia requiring antimicrobial therapy; Growth quantity and timing help differentiate true infection from contamination (single positive bottle vs multiple bottles)
- Susceptibility Categories: Susceptible (S) - organism inhibited by standard antibiotic doses; Intermediate (I) - organism may respond to higher doses; Resistant (R) - organism not inhibited by achievable drug concentrations
Interpretation
- Negative Result: No anaerobic bacteremia present; rules out anaerobic septicemia; patient may have aerobic infections or non-infectious fever; contamination ruled out when collected properly
- Positive Result: Confirms anaerobic bacteremia; identifies specific organism(s) cultured; indicates serious infection requiring immediate targeted antimicrobial therapy; organism susceptibility pattern guides antibiotic selection
- Contamination Indicators: Growth in only one of two bottles suggests contamination; common skin commensals like Propionibacterium, coagulase-negative Staphylococcus may indicate contamination; clinical correlation with patient symptoms essential
- Time to Positivity: Early positivity (24-48 hours) suggests higher bacterial load; delayed positivity may indicate lower level bacteremia or fastidious organisms; helps assess severity and source of infection
- Susceptibility Pattern Significance: Susceptible pattern allows narrowest-spectrum antibiotic use; intermediate results may require monitoring or dose adjustment; resistant patterns necessitate alternative agent selection; multi-drug resistance impacts prognosis
- Factors Affecting Results: Prior antibiotic therapy may reduce culture yield; timing of blood draw relative to fever spikes; collection technique and bottle fill volume; sample transport time and temperature; immunosuppression status; presence of polymicrobial infections
- Common Anaerobic Organisms: Bacteroides fragilis group; Prevotella species; Clostridium difficile, perfringens, botulinum; Peptococcus and Peptostreptococcus species; Fusobacterium nucleatum; anaerobic cocci; Eubacterium species
Associated Organs
- Primary Systems Involved: Circulatory/Cardiovascular system (bloodstream); Gastrointestinal tract (source of many anaerobes); Oral cavity (periodontal infections); Female reproductive tract; Biliary system; Respiratory tract (aspiration)
- Associated Conditions: Septicemia/sepsis; bacterial endocarditis; intra-abdominal infections (appendicitis, diverticulitis, peritonitis); aspiration pneumonia; lung abscess; necrotizing soft tissue infections; diabetic foot ulcers; bite wound infections; pelvic inflammatory disease; postoperative infections
- Diseases Commonly Diagnosed: Bacteremia caused by anaerobic organisms; polymicrobial infections; Clostridioides difficile bacteremia; gas gangrene; tetanus (Clostridium tetani); botulism; Lemierre's syndrome; acute necrotizing infections
- Potential Complications: Septic shock; multiple organ failure; treatment failure if incorrect antibiotics selected; disseminated infection; abscess formation; thromboembolism; myocardial infarction; acute kidney injury; disseminated intravascular coagulation
- Risk Factors for Anaerobic Infections: Immunosuppression; malignancy; diabetes; trauma; surgery; aspiration risk; poor dentition; recent antibiotic use; indwelling catheters; elderly patients; abdominal pathology
Follow-up Tests
- Repeat Blood Cultures: Recommended 24-48 hours after antibiotic initiation to confirm organism clearance; assess therapy effectiveness; persistent positivity indicates inadequate treatment or complications
- Aerobic Blood Culture: Run simultaneously with anaerobic cultures; many infections are polymicrobial; identifies co-pathogens; impacts broad-spectrum therapy decisions
- Imaging Studies: CT scan; ultrasound; MRI to identify infection source and localized abscess; assess organ involvement; guide intervention planning (drainage procedures)
- Complete Blood Count (CBC): Monitor white blood cell count and differential; assess response to infection; evaluate thrombocytopenia; track recovery
- Comprehensive Metabolic Panel (CMP): Assess organ function; evaluate electrolyte abnormalities; monitor kidney and liver function during therapy; detect complications
- Prothrombin Time (PT/INR), Partial Thromboplastin Time (PTT): Screen for disseminated intravascular coagulation (DIC); assess coagulation status in septic patients; monitor for bleeding complications
- Echocardiography: When endocarditis suspected; identifies vegetations; assesses valve function; detects complications (perivalvular abscess, aortic root disease)
- Source Cultures: Identify primary infection source; wound cultures; urine cultures; CSF cultures; bile cultures; samples from surgical drainage or abscess aspiration
- Procalcitonin: Marker of bacterial infection severity; helps differentiate bacterial from viral infections; monitor therapy response; elevated levels indicate severe infection
- Lactate Level: Assesses tissue perfusion; identifies septic shock; prognostic indicator; elevated levels suggest severe infection and poor outcome risk
- Monitoring Frequency: Daily monitoring during acute phase; repeat labs every 24-48 hours initially; less frequent monitoring as patient improves; continue until clinical resolution and negative repeat cultures
Fasting Required?
- Fasting Requirement: NO - Fasting is NOT required for blood culture collection
- Patient Preparation: May eat and drink normally; no special diet restrictions; hydration is recommended; patient should be seated or reclined comfortably for blood draw
- Skin Preparation: Venipuncture site must be cleaned with antiseptic solution (typically povidone-iodine or chlorhexidine); alcohol prep alone is insufficient; allow skin to dry before collection to prevent contamination
- Medications to Avoid: Do NOT start antibiotics before blood collection if possible; if patient already receiving antibiotics, continue on schedule (test still meaningful); no other specific medications need to be held
- Collection Timing: Collect during fever spike if possible; avoid collection immediately after antibiotic dose (collect just before next dose); daytime collection preferred for optimal processing; STAT collection for suspected sepsis
- Collection Volume: Typically 8-10 mL per bottle (minimum 5 mL); use proper ratio of blood to media (usually 1:10); fill aerobic bottle first, then anaerobic bottle; avoid underfilling which reduces culture sensitivity
- Special Instructions: Collect from two different sites (arms) to differentiate contamination from true bacteremia; do NOT use indwelling catheters unless specifically requested; handle tubes gently to avoid hemolysis; transport to laboratory within 30 minutes; maintain anaerobic conditions (never refrigerate); note antimicrobial therapy on requisition
- After Collection: Normal activities may resume immediately; minimal bruising to bleeding risk; can perform all normal functions; maintain current medications and diet; contact healthcare provider with results or if symptoms worsen

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