Rapid increase in macrolide resistance among penicillin non-susceptible pneumococci in Finland, 1996-2000.
The aims of this study were to evaluate the resistance patterns and serotypes/groups of penicillin non-susceptible pneumococci (PNSP) in Finland, and to determine phenotypes and resistance mechanisms of the erythromycin-resistant isolates. A total of 1190 PNSP were collected during 1996-2000 in Finland. The MICs of 18 antimicrobials were determined by the agar plate dilution method, and PCR was used to study the resistance mechanisms of the macrolide-resistant isolates. For serotyping, counterimmunoelectrophoresis and latex agglutination were used. Erythromycin resistance increased from 32% in 1996 to 62% in 2000 among PNSP in Finland. Multiresistance (co-resistance to erythromycin, tetracycline and co-trimoxazole) was present in 22% of the isolates in 1996 and in 40% in 2000. The most common macrolide resistance phenotype was the MLS(B) phenotype (72%), 25% had the M phenotype and 3% the MS phenotype. The MLS(B) and M phenotypes increased in the same proportion during the study period. All the MLS(B) isolates had the erm(B) gene, the M isolates the mef(A) gene, and in 11 MS isolates, ribosomal mutations were the cause of resistance. The most common serotypes/groups were 14, 19 and 6. We found a significant increase in multiresistance among PNSP within a short period of time in Finland. Although pneumococcal resistance to erythromycin was 11% in 2000, the same figure was 50% among the PNSP. The rise in erythromycin resistance is worrying, as macrolides are commonly used as first- and second-line drugs in pneumococcal infections.
Pihlajamäki
Marja
M
Antimicrobial Research Laboratory, National Public Health Institute, Kiinamyllynkatu 13, 20520 Turku, Finland. mapihla@utu.fi
Kaijalainen
Tarja
T
Huovinen
Pentti
P
Jalava
Jari
J
D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D004351:Drug Resistance; D018432:Drug Resistance, Multiple; D004363:Drug Utilization; D005387:Finland / Q000453:epidemiology; D006801:Humans; D018942:Macrolides; D008826:Microbial Sensitivity Tests; D010406:Penicillins / Q000494:pharmacology*; D010641:Phenotype; D011008:Pneumococcal Infections / Q000453:epidemiology / Q000382:microbiology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012703:Serotyping; D013296:Streptococcus pneumoniae / Q000187:drug effects* / Q000235:genetics
D000900:Anti-Bacterial Agents; D018942:Macrolides; D010406:Penicillins