Penicillin-resistant Streptococcus pneumoniae in Lebanon: the first nationwide study

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) ≤ 0.06 μg/mL), 56.1% were intermediately susceptible (MIC 0.09–1.0 μg/mL) and 13.8% were resistant (MIC > 1.0 μg/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 ≤ 2/1 μg/mL). This discrepancy represents a paradox that deserves serious consideration.