What is the Penicillin (PCN) resistance rate in southeast Missouri?

Penicillin Resistance Rates in Southeast Missouri

Based on the available evidence, there is no specific data on penicillin resistance rates in southeast Missouri, but national data indicates that approximately 25-50% of Streptococcus pneumoniae strains in the United States show relative or high resistance to penicillin. 1

General Penicillin Resistance Patterns in the United States

Streptococcus pneumoniae

• 25-50% of S. pneumoniae strains in the US demonstrate relative or high resistance to penicillin 1
• Resistance levels are defined by the National Committee for Clinical Laboratory Standards:
  • Susceptible: MIC ≤0.06 mg/mL
  • Intermediate resistance: MIC 0.1-1.0 mg/mL
  • Resistant: MIC ≥2.0 mg/mL 1

Other Common Pathogens

• Approximately 50% of Haemophilus influenzae strains are β-lactamase producing 1
• 90-100% of Moraxella catarrhalis strains are β-lactamase producing 1
• 100% of Streptococcus pyogenes remain susceptible to penicillin despite increasing macrolide resistance (8-9% in 1999-2001) 1

Clinical Implications of Resistance

Pneumococcal Infections

• For pneumonia, intermediate resistance to penicillin is not clinically important, but high-grade resistance (MIC >4 mg/mL) may be significant 1
• High-dose amoxicillin (90 mg/kg/day in 2 divided doses) can overcome resistance in most cases 1
• For severe infections with suspected drug-resistant S. pneumoniae, alternative agents such as respiratory fluoroquinolones may be needed 2

Skin and Soft Tissue Infections

• For community-acquired skin infections, empiric therapy should account for potential MRSA, which has high prevalence in many communities 1
• For serious infections, assume resistance and use agents effective against MRSA (vancomycin, linezolid, or daptomycin) 1

Risk Factors for Resistant Infections

• Age ≥65 years (OR 3.8)
• Alcoholism (OR 5.2)
• β-lactam therapy within previous 3 months (OR 2.8)
• Multiple medical comorbidities
• Exposure to children in daycare centers
• Immunosuppressive illness 1

Recommendations for Clinical Practice

When treating infections in southeast Missouri without specific local resistance data:

1. For empiric therapy of respiratory infections:

   • Consider high-dose amoxicillin or amoxicillin-clavulanate for mild-moderate infections
   • For severe infections or high-risk patients, use broader coverage (respiratory fluoroquinolones or combination therapy)

2. For skin and soft tissue infections:

   • Assume potential MRSA and treat accordingly, especially for severe infections
   • Reevaluate patients in 24-48 hours if using empiric therapy to verify clinical response 1

3. For urinary tract infections:

   • Consider local resistance patterns; when resistance rates exceed 20%, culture-guided therapy is recommended 1, 3

Importance of Surveillance and Antibiotic Stewardship

• Regional resistance patterns vary significantly across the United States 1
• Unnecessary broad-spectrum antibiotic use contributes to increasing resistance 4
• When possible, obtain appropriate cultures before initiating antibiotics and de-escalate therapy based on susceptibility results 1

Without specific data for southeast Missouri, clinicians should consider consulting with local infectious disease specialists or hospital antibiograms for the most accurate regional resistance patterns.