What do S (Sensitive) and SYN-S (Synergistic Sensitive) indicate in wound culture reports?

Understanding S and SYN-S in Wound Culture Reports

In wound culture reports, "S" stands for "Sensitive," indicating that the isolated bacteria are susceptible to a particular antibiotic, while "SYN-S" stands for "Synergistic Sensitive," meaning the bacteria are sensitive to a combination of antibiotics that work synergistically together.

Antimicrobial Susceptibility Testing Terminology

"S" (Sensitive)

• Indicates that the isolated pathogen is inhibited by the standard dosage of an antibiotic
• When "S" appears next to an antibiotic name, it means the antibiotic is likely to be effective against the identified organism
• Guides clinicians in selecting appropriate antibiotics for treating the infection
• Based on standardized laboratory testing methods that determine minimum inhibitory concentrations (MICs)

"SYN-S" (Synergistic Sensitive)

• Indicates that two antibiotics work together more effectively than either one alone
• Commonly seen with combinations such as:
  • Beta-lactam antibiotics with aminoglycosides
  • Trimethoprim with sulfamethoxazole
  • Piperacillin with tazobactam
• The synergistic effect may allow for:
  • Lower doses of individual antibiotics
  • Enhanced bacterial killing
  • Broader spectrum of coverage
  • Potential reduction in development of resistance

Clinical Significance

The interpretation of these sensitivity patterns is crucial for effective treatment of wound infections:

• Sensitivity results guide appropriate antibiotic selection, which directly impacts:

  • Morbidity and mortality outcomes 1
  • Healing time of infected wounds
  • Prevention of antimicrobial resistance

• For polymicrobial infections (common in chronic wounds), understanding both individual and synergistic sensitivities is particularly important 1

• When treating diabetic foot infections or surgical site infections, targeted therapy based on culture and sensitivity results improves outcomes compared to empiric therapy 1

Practical Application

When reviewing wound culture reports:

1. First identify the isolated organism(s)
2. Check which antibiotics are marked as "S" (sensitive)
3. Look for any "SYN-S" designations that indicate beneficial antibiotic combinations
4. Select the most appropriate antibiotic therapy based on:
   • Sensitivity results
   • Site of infection
   • Patient factors (allergies, renal function)
   • Local resistance patterns

Common Pitfalls to Avoid

• Don't ignore polymicrobial results: Multiple organisms are common in chronic wounds, and all significant pathogens should be addressed 1

• Don't assume all "S" antibiotics are equally effective: Consider tissue penetration, side effects, and spectrum of activity

• Don't overlook synergistic combinations: When "SYN-S" is indicated, the combination may be more effective than monotherapy, particularly for difficult-to-treat infections

• Don't continue broad-spectrum antibiotics unnecessarily: Once sensitivity results are available, therapy should be narrowed to the most appropriate agent(s) 1

• Don't rely solely on superficial wound cultures: Deep tissue specimens are more reliable than superficial swabs for identifying true pathogens 1

By understanding these designations in wound culture reports, clinicians can select the most effective antimicrobial therapy, improving patient outcomes while minimizing the risk of developing antimicrobial resistance.