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Penicillin-resistant Streptococcus pneumoniae in Lebanon: the first nationwide study
Marwan Uwaydah1, Jacques E Mokhbat, Dolla Karam-Sarkis
1American University of Beirut Medical Center, P.O. Box 11 - 0236, Riad El Solh 110 72020, Beirut, Lebanon. mardah@cyberia.net.lb
Abstract:
A total of 123 clinical isolates of Streptococcus pneumoniae were collected from all over Lebanon and tested for their susceptibility to penicillin: 30.1% were susceptible (minimum inhibitory concentration (MIC) < or = 0.06 microg/mL), 56.1% were intermediately susceptible (MIC 0.09-1.0 microg/mL) and 13.8% were resistant (MIC > 1.0 microg/mL). The oxacillin disk screening test detected all penicillin-resistant isolates, but erroneously designated two penicillin-intermediate isolates as penicillin susceptible. All isolates were consistently susceptible to levofloxacin, but cross-resistance between penicillin and the three tested cephalosporins was frequently noted. The in vitro activity of amoxicillin/clavulanic acid paralleled that of penicillin; however, 92.7% of the isolates were designated as susceptible based on the recommended interpretive cut-off point (MIC < or = 2/1 microg/mL). This discrepancy represents a paradox that deserves serious consideration.
Insights
Penicillin resistance in Streptococcus pneumoniae is significant in Lebanon, with over 13% resistant. While levofloxacin showed consistent susceptibility, amoxicillin/clavulanic acid results present a concerning discrepancy.
Area of Science:
- Microbiology
- Infectious Diseases
- Antimicrobial Resistance
Background:
- Streptococcus pneumoniae is a major cause of bacterial infections worldwide.
- Antimicrobial resistance in S. pneumoniae poses a significant public health threat.
- Understanding local resistance patterns is crucial for effective treatment strategies.
Purpose of the Study:
- To determine the antimicrobial susceptibility patterns of clinical isolates of Streptococcus pneumoniae in Lebanon.
- To evaluate the effectiveness of commonly used antibiotics against S. pneumoniae.
- To investigate potential cross-resistance between different antibiotic classes.
Main Methods:
- Collection of 123 clinical isolates of Streptococcus pneumoniae from Lebanon.
- Testing susceptibility to penicillin using minimum inhibitory concentration (MIC) breakpoints.
- Utilizing the oxacillin disk screening test for penicillin resistance detection.
- Assessing susceptibility to levofloxacin, cephalosporins, and amoxicillin/clavulanic acid.
Main Results:
- 30.1% of isolates were susceptible to penicillin, 56.1% intermediate, and 13.8% resistant (MIC > 1.0 microg/mL).
- Oxacillin disk screening correctly identified all resistant isolates but misclassified two intermediate isolates.
- All isolates remained susceptible to levofloxacin.
- Frequent cross-resistance was observed between penicillin and tested cephalosporins.
- Amoxicillin/clavulanic acid showed high susceptibility rates (92.7%) despite in vitro activity mirroring penicillin.
Conclusions:
- A substantial proportion of Streptococcus pneumoniae isolates in Lebanon exhibit penicillin resistance or intermediate resistance.
- Levofloxacin remains a highly effective agent against these isolates.
- The discrepancy in amoxicillin/clavulanic acid susceptibility based on interpretive cut-off points warrants further investigation.
- Local surveillance of antimicrobial resistance is essential for guiding clinical practice.
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