Aerobic C&S Vaginal Swab Culture and Susceptibility Testing - MIC
Also Known As
Test Parameters Included
- Aerobic Bacterial Pathogen Identification (semiquantitative growth)
- Minimum Inhibitory Concentration (MIC) values (μg/mL) for selected antibiotics
- Pathologist Microbiology Remark - correlated with clinical symptoms and resistance patterns
Department
Methodology
This test utilizes an Automated Culture and Susceptibility Testing system to identify aerobic bacterial pathogens in a vaginal swab sample and determine their susceptibility to antibiotics. The process involves:
* Automated Inoculation: The vaginal swab is used to inoculate various appropriate culture media (e.g., Blood Agar, Chocolate Agar, MacConkey Agar) designed to support the growth of a wide range of aerobic bacteria. Some labs may use specific media for common vaginal pathogens. * Automated Incubation: The inoculated plates are then automatically transferred to an incubator at a specific temperature (typically 35-37°C) for a defined period (usually 18-24 hours), potentially including specific atmospheric conditions (e.g., 5-10% CO2) if indicated for certain common vaginal flora or pathogens.
* Automated Growth Detection & Colony Selection: After incubation, automated systems (e.g., using imaging technology) detect and analyze bacterial growth. Laboratory technologists, often guided by the system, select colonies suspicious of significant pathogens. It's crucial here to differentiate between normal vaginal flora and potential pathogens.
* Automated Identification (ID): Pure colonies of suspected pathogens are isolated. Automated systems then perform rapid biochemical tests or mass spectrometry (e.g., MALDI-TOF) to accurately identify the specific bacterial species (e.g., Streptococcus agalactiae (Group B Strep), Staphylococcus aureus, Escherichia coli, etc.). Note: Interpretation must consider the extensive normal commensal flora of the vagina.
* Automated Susceptibility Testing (AST) - MIC: Once significant pathogenic bacteria are identified, the automated system prepares a standardized bacterial suspension and performs susceptibility testing. This involves exposing the bacteria to various concentrations of different antibiotics. The system then measures the Minimum Inhibitory Concentration (MIC) for each antibiotic. The MIC is the lowest concentration of an antibiotic that prevents visible growth of the bacterium.
* Automated Interpretation: The MIC values are then automatically interpreted by the system (based on established clinical breakpoints from organizations like CLSI - Clinical and Laboratory Standards Institute) to determine if the isolate is Susceptible (S), Intermediate (I), or Resistant (R) to each tested antibiotic.
This automated approach offers rapid, standardized, and highly accurate results for both bacterial identification and antibiotic susceptibility, crucial for guiding effective antibiotic therapy for vaginal infections.
Sample Required
* Collection Device: A sterile swab, preferably in a transport medium suitable for aerobic bacteria (e.g., Amies, Stuart, or ESwab). Calcium alginate swabs and cotton swabs with wooden shafts should be avoided as they may inhibit bacterial growth. * Collection Procedure: The swab should be collected by a healthcare professional (or sometimes by the patient with clear instructions) from the vaginal vault. * For diagnostic purposes (e.g., vaginitis, discharge), a swab of the discharge from the posterior fornix or vaginal walls is generally taken. * For Group B Strep screening in pregnancy, a rectovaginal swab is often preferred, including swabbing both the lower vaginal and perianal areas. * Timely Transport/Storage: The swab in transport medium should be transported to the laboratory as soon as possible (ideally within 24 hours). If immediate transport is not possible, it should be stored at room temperature or refrigerated according to the transport media manufacturer's instructions to maintain the viability of bacteria.
Preparation
* Avoid Vaginal Products: Advise the patient to avoid douching, using vaginal creams, jellies, or suppositories for at least 24-48 hours prior to sample collection, as these can interfere with results.
* Timing: Generally, it's best to avoid collection during menstruation if possible, as blood can obscure results and introduce contaminants.
* Specimen Collection: Usually performed by a healthcare professional. For GBS screening, specific rectovaginal collection techniques are used.
* Transport: Place the swab immediately into appropriate transport media (e.g., Amies, Stuart, or ESwab). Transport to the laboratory promptly. If immediate transport is not possible, store according to transport media instructions (typically room temperature or refrigeration for 24 hours).
Schedule Report
72 Hours
Emergency Report
Yes
Frequently Asked Questions
Is fasting required for this test?
No, fasting is not required. The test uses a vaginal swab sample, unaffected by food intake.
How is the sample collected?
A sterile swab is gently inserted into the vagina to collect secretions from the posterior fornix or affected area. Avoid douching or using vaginal medications 24 hours before collection.
What does this test detect?
It identifies aerobic bacteria causing vaginal infections (e.g., Group B Streptococcus, Staphylococcus aureus, E. coli, Gardnerella) and determines which antibiotics effectively inhibit their growth.
What is MIC testing?
Minimum Inhibitory Concentration measures the lowest antibiotic concentration that prevents visible bacterial growth. Lower MIC values indicate greater antibiotic susceptibility.
How long does it take to get results?
Preliminary reports are available in 24-48 hours. Final culture and susceptibility results typically take 48-72 hours depending on organism growth rate.
Can vaginal medications affect results?
Yes, recent use of antibiotics, antifungals, or antiseptic washes may suppress bacterial growth and cause false-negative results. Inform your doctor about recent treatments.
Test Description
Test Code
C75
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