Culture & Sensitivity, Aerobic bacteria Throat Swab For C.Diptheriae (Manual method)

Bacterial/ Viral

Report in 72Hrs

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No Fasting Required

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Identifies bacteria & antibiotic susceptibility.

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Culture & Sensitivity Aerobic bacteria Throat Swab For C.Diptheriae (Manual method)

Why is it done?
- Detection and identification of Corynebacterium diphtheriae, the causative agent of diphtheria, a serious bacterial infection affecting the respiratory system and potentially other organs
- Evaluation of acute pharyngitis, sore throat, or upper respiratory tract infections with suspected diphtheria
- Confirmation of diphtheria in patients presenting with characteristic pseudomembrane formation in the pharynx or nasopharynx
- Contact tracing and surveillance of individuals exposed to suspected or confirmed diphtheria cases
- Determination of antibiotic susceptibility patterns to guide targeted therapeutic intervention
- Differential diagnosis in patients with throat symptoms unresponsive to standard treatment
- Screening of healthcare workers or food handlers following potential exposure to diphtheria
Normal Range
- Negative Result: No growth of Corynebacterium diphtheriae detected on culture media. Normal throat flora may include Streptococcus viridans, Staphylococcus epidermidis, Neisseria species, and other commensal organisms
- Units of Measurement: Qualitative (Positive/Negative); Quantitative culture expressed as Colony Forming Units per milliliter (CFU/mL) or semi-quantitative as sparse (1+), moderate (2+), or heavy growth (3-4+)
- Interpretation of Normal: Absence of C. diphtheriae indicates patient is either not infected, successfully treated, or not a carrier of diphtheria. Normal commensal throat bacteria may be reported
- Sensitivity Pattern (Normal/Expected): If C. diphtheriae is isolated, susceptibility to penicillin, erythromycin, or cephalosporins is typically expected; resistance patterns are uncommon but possible with resistant or non-toxigenic strains
Interpretation
- Positive Culture - C. diphtheriae Isolated: Confirms active diphtheria infection or carrier state; organism identification includes morphological characteristics (gram-positive bacilli), colonial morphology (tellurite reduction producing dark colonies), and biochemical tests (fermentation patterns)
- Toxigenicity Status: Toxigenic strains produce diphtheria toxin causing severe systemic manifestations; non-toxigenic strains may cause localized infection; toxin production assessed via Elek test or molecular methods (PCR for toxin gene)
- Biotype Classification: Gravis (larger colonies, strong toxin production), Mitis (small translucent colonies), or Intermedius (intermediate characteristics) affecting clinical severity and treatment approach
- Sensitivity Results: Reported as Susceptible (S), Intermediate (I), or Resistant (R) to specific antibiotics; penicillin and erythromycin are first-line agents; aminoglycosides, fluoroquinolones, and rifampin may be effective alternatives
- Negative Culture: Suggests absence of C. diphtheriae; may indicate alternative diagnosis (viral pharyngitis, Group A Streptococcus), prior antibiotic treatment, or inadequate specimen collection; consider repeat sampling if clinical suspicion remains high
- Factors Affecting Results: Timing of specimen collection (early in illness optimal), prior antibiotic therapy (may inhibit growth), proper swab technique and specimen transport, culture media quality, and duration of incubation (48-72 hours required for optimal recovery)
- Clinical Significance: Positive toxigenic C. diphtheriae indicates immediate need for antitoxin administration and supportive care; guides infection control measures; positive non-toxigenic strains require clinical correlation; culture confirmation essential before treatment initiation due to serious complications
Associated Organs
- Primary Organ Systems: Respiratory tract (pharynx, larynx, trachea); respiratory epithelium where pseudomembrane forms; nasopharynx and oropharynx primarily affected
- Secondary Organ Involvement (Toxin-mediated): Heart (myocarditis, arrhythmias, cardiogenic shock); nervous system (cranial nerve palsies, ascending paralysis, respiratory failure); kidneys (acute kidney injury); adrenal glands (acute necrosis)
- Associated Diseases: Acute diphtheria with pseudomembrane formation; cutaneous diphtheria; wound diphtheria; respiratory diphtheria with airway obstruction; chronic carrier state; invasive diphtheria infections in immunocompromised patients
- Potential Complications: Airway obstruction requiring intubation or tracheostomy; myocarditis causing shock and fatal arrhythmias; polyneuropathy with respiratory paralysis; secondary bacterial infections; aspiration pneumonia; septic emboli; death if untreated
- Diagnostic Significance: Culture confirmation essential for distinguishing diphtheria from viral pharyngitis, acute streptococcal pharyngitis, or other bacterial causes; positive result indicates need for immediate treatment initiation
- Public Health Implications: Reportable disease; positive cases require notification to public health authorities; contact tracing mandatory; carriers require identification and prophylaxis; outbreak investigation and epidemiological surveillance necessary
Follow-up Tests
- Toxin Production Assessment: Elek test (immunodiffusion) for toxin detection; PCR testing for toxin gene (tox+) to confirm toxigenic strain; necessary to guide treatment intensity and prognosis
- Repeat Culture if Initially Negative: Repeat throat and nasopharyngeal swabs 48-72 hours after initial sampling if high clinical suspicion persists; useful in suspected carriers or recent treatment initiation
- Post-Treatment Follow-up Cultures: Throat culture at completion of antimicrobial therapy (2-4 weeks post-treatment) to confirm eradication; second culture 2 weeks later if initial post-treatment culture remains positive
- Cardiac Evaluation: Electrocardiogram (ECG) to detect arrhythmias or conduction abnormalities; cardiac biomarkers (troponin, BNP); echocardiography if myocarditis suspected; serial ECGs to monitor for cardiotoxicity
- Neurological Assessment: Cranial nerve function testing; electromyography (EMG) if polyneuropathy suspected; lumbar puncture to rule out CNS involvement if atypical presentation
- Contact Screening Cultures: Throat and nasopharyngeal cultures of close contacts; specimens obtained at initial contact and 2 weeks later if first sample negative; identifies asymptomatic carriers for prophylaxis
- Serological Testing: Diphtheria antitoxin antibody levels to assess immunity; Schick test (historical but still used in some settings) to determine toxin susceptibility; useful for screening vaccination status
- Molecular Testing (PCR): Real-time PCR for C. diphtheriae detection and toxin gene amplification; faster than culture; useful for rapid diagnosis and epidemiological tracking
- Monitoring Frequency: Initial culture results within 48-72 hours; post-treatment cultures at weeks 2-4 and week 6; close contact cultures within 24 hours of exposure and again at 2 weeks; ongoing surveillance during outbreak investigations
Fasting Required?
- Fasting: NO Fasting is not required for this throat swab culture test
- Patient Preparation: No special dietary restrictions; patient can eat and drink normally before test; avoid eating or drinking for 5-10 minutes immediately before specimen collection to minimize contamination with oral flora and food debris
- Pre-collection Instructions: Do not rinse mouth or gargle with antiseptic solutions prior to collection; avoid mouthwash or throat lozenges for at least 30 minutes before swabbing; do not use antibiotic throat sprays or gargles before collection
- Medications: Do not apply local anesthetics to throat prior to swabbing; if already on antimicrobial therapy, document this on specimen requisition as it may inhibit bacterial growth and affect culture positivity; optimal timing for culture is before antibiotic initiation
- Specimen Collection Requirements: Sterile cotton or calcium alginate swab used to obtain specimen from posterior pharynx and tonsillar area; nasopharyngeal swab may also be obtained; swabs placed in appropriate transport media (Amies or Stuart's medium) immediately after collection; specimens kept at room temperature and transported to laboratory within 2 hours
- Timing of Collection: Optimal collection within first 3-5 days of symptom onset for highest recovery rates; later collection may still yield positive results in pseudomembranous diphtheria; collection can be performed at any time of day
- Additional Precautions: Use appropriate personal protective equipment (mask, gloves, eye protection) during specimen collection; consider airborne precautions if active diphtheria suspected; proper biohazard labeling and handling; inform patient to close mouth during transport container sealing

How our test process works!