MicrobiologyInfectious Diseases

Culture and Sensitivity

Normal Range
No growth of pathogens
Sample Type
Varies (Blood, Urine, Sputum, etc.)
Fasting
No
Unit
Qualitative

Function

The Culture and Sensitivity (C&S) test is the gold standard in microbiology for diagnosing bacterial and fungal infections. The process involves two steps: first, the 'Culture,' where the specimen is placed in a growth medium to see if any organisms multiply; and second, the 'Sensitivity,' where the isolated organism is exposed to various antibiotics to see which ones effectively kill it.

Why it is Ordered

This test is ordered whenever an infection is suspected and the clinician needs to know exactly what is causing it and how to treat it. It is commonly used for Urinary Tract Infections (UTIs), respiratory infections, bloodstream infections (sepsis), and wound infections. It moves treatment from 'empiric' (best guess) to 'definitive' (targeted).

Associated Conditions

  • Bacteremia/Sepsis: Growth of bacteria in the blood.
  • Urinary Tract Infections (UTI): Growth of coliforms like E. coli in urine.
  • Pneumonia: Identification of S. pneumoniae or Klebsiella in sputum.
  • Skin/Soft Tissue Infections: Identification of Staph aureus or Streptococcus.

Clinical Importance

With the global rise of multi-drug resistant organisms (MDROs), the sensitivity profile is indispensable. It allows for 'Antibiotic Stewardship,' ensuring that broad-spectrum drugs are reserved for severe cases and that the patient receives the most narrow-spectrum, effective drug possible, reducing side effects and the risk of fostering further resistance.

Why Context Matters

Results can be confounded by improper sample collection (e.g., not collecting a 'mid-stream' urine sample), which introduces normal skin or environmental bacteria into the culture. Taking even a single dose of an antibiotic before the sample is collected can prevent the pathogen from growing in the lab, resulting in a false-negative 'No Growth' result despite the patient being ill.

Lab ranges are statistical averages, not biological laws. "Normal" for a 20-year-old male isn't normal for a 60-year-old female.

Clinical References

Source-of-truth databases and clinical guidelines for Culture and Sensitivity:

Research & Guidelines

Related Indicators

Albert's Stain

View Range

Spore Stain

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AFB Culture (Radiometric)

View Range
DR

Medically Reviewed by Dr. Binoy Babu, MBBS

Board Certified Doctor • 10+ Years Clinical Experience

Dr. Babu is a practicing physician dedicated to empowering patients with clear, actionable medical information. He founded 2opi to bridge the gap between complex lab reports and patient understanding, ensuring everyone has access to a reliable second opinion.

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