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Clinical relevance of penicillin-resistant Streptococcus pneumoniae
1Infectious Disease Division, Winthrop-University Hospital, Mineola; and the State University of New York School of Medicine, Stony Brook, NY 11501, USA.
Abstract:
Streptococcus pneumoniae is the most important respiratory tract pathogen in otitis, sinusitis, bronchitis, and community-acquired pneumonia. Over the past decades, there has been an increase in minimum inhibitory concentrations (MICs) to penicillin. Decreased susceptibility to penicillin is not the same as penicillin resistance. Decreased susceptibility to penicillin has occurred worldwide from dissemination of several resistant pneumococcal clones, and, to a lesser extent, from excessive use of ciprofloxacin, macrolides, and trimethoprim-sulfamethoxazole (TMP-SMX). Currently, penicillin resistance is defined by using a breakpoint of 2 microg/mL or more. Intermediately resistant strains (MIC 1-2 microg/mL) are also relatively sensitive depending on antibiotic concentration. Intermediate antibiotic susceptibility is concentration dependent. Antibiotic concentration at various body sites is determined by pharmacokinetic considerations. Except for very highly resistant strains, the treatment of penicillin-resistant S. pneumoniae causing bacteremia, sinusitis, otitis, bronchitis, or community-acquired pneumonia remains penicillin or any beta-lactam. Only in pneumococcal meningitis caused by penicillin-resistant pneumococci does the clinician have to use care in selecting an antipneumococcal antibiotic with adequate cerebrospinal fluid penetration and favorable kill ratios. Clinicians should be selective in antibiotic selection to minimize further decreases in penicillin susceptibility to S. pneumoniae. This is best achieved by using low-resistance potential antibiotics oral/intravenous mono-therapy at the full recommended dose. Therapeutic failure may occur in using lower doses at certain body sites. Macro-lides as monotherapy or as part of combination therapy should be minimized. Optimal therapy for non-central nervous system pneumococcal infection is with a respiratory quinolone (eg, levofloxacin, gatifloxacin, moxifloxacin), clindamycin, doxycycline, third-generation cephalosporins. For highly resistant pneumococci, levofloxacin, gatifloxacin, moxifloxacin, cefepime, meropenem, vancomycin, or linezolid may be used.
Insights
Penicillin resistance in Streptococcus pneumoniae is increasing globally. Careful antibiotic selection, prioritizing respiratory quinolones and avoiding macrolides, is crucial for effective treatment and minimizing further resistance.
Area of Science:
- Medical Microbiology
- Infectious Diseases
- Pharmacology
Background:
- Streptococcus pneumoniae is a major cause of respiratory infections like pneumonia and otitis.
- Increasing minimum inhibitory concentrations (MICs) to penicillin have been observed globally.
- Decreased penicillin susceptibility is driven by resistant pneumococcal clones and overuse of other antibiotics.
Purpose of the Study:
- To review the current status of penicillin resistance in Streptococcus pneumoniae.
- To provide guidance on appropriate antibiotic selection for S. pneumoniae infections.
- To emphasize strategies for minimizing the development of further antibiotic resistance.
Main Methods:
- Literature review of studies on Streptococcus pneumoniae resistance patterns.
- Analysis of antibiotic susceptibility data and clinical treatment outcomes.
- Pharmacokinetic considerations for antibiotic efficacy at various body sites.
Main Results:
- Penicillin resistance is defined by MICs ≥ 2 microg/mL; intermediate resistance (MIC 1-2 microg/mL) is concentration-dependent.
- For most S. pneumoniae infections, penicillin or other beta-lactams remain effective, except in cases of meningitis.
- Respiratory quinolones, clindamycin, doxycycline, and third-generation cephalosporins are optimal for non-CNS infections.
Conclusions:
- Judicious antibiotic selection is essential to combat rising penicillin resistance in S. pneumoniae.
- Minimizing macrolide monotherapy and using full-dose, low-resistance potential antibiotics is recommended.
- For highly resistant strains, alternative agents like fluoroquinolones, cefepime, meropenem, vancomycin, or linezolid are necessary.