BACKGROUND: Streptococcus pneumoniae is the most common etiologic agent of community-acquired respiratory infections. In recent years, S. pneumoniae resistance to antimicrobial agents has increased. Minimum inhibitory concentration (MIC) is routinely used to determine resistance. Polymerase chain reaction (PCR) detects the genes responsible for Streptococcus pneumoniae resistance to penicillin within approximately 8 hours. OBJECTIVE: To compare the PCR and MIC methods in determining Streptococcus pneumoniae resistance to penicillin. METHOD: A total of 153 Streptococcus pneumoniae samples, isolated from various anatomical sites, were evaluated in order to detect mutations in the genes encoding pbp1a, pbp2a and pbp2x, which are responsible for Streptococcus pneumoniae penicillin resistance. A correlation was found between mutations and penicillin MIP, as determined by the agar diffusion method. RESULTS: Overal Streptococcus pneumoniae resistance to penicillin was 22.8% (16.3% intermediate resistance and 6.5% high resistance). In a statistically significant finding, we observed no mutations in the penicillin-sensitive samples and only one mutation, typically in the gene encoding pbp2x, among the samples with intermediate resistance, whereas mutations in all three genes studied were observed in the high-resistance samples. CONCLUSION: For determining Streptococcus pneumoniae resistance to penicillin, PCR is a rapid method of detection that could well be used in clinical practice.
Streptococcus pneumoniae; Penicillin resistance; Polymerase chain reaction
