Prevalence and Molecular Genetics of Macrolide Resistance among Streptococcus pneumoniae Isolates Collected in Finland in 2002

Abstract

The prevalence and mechanisms of macrolide resistance among 1,007 clinical pneumococcal isolates collected in Finland were investigated. Of these, 217 (21.5%) were resistant to erythromycin and 11% to clindamycin. Among the erythromycin-resistant isolates, mef(E) was present in 95 isolates (44%), mef(A) was present in 12 isolates (6%), and erm(B) was present in 90 isolates (41%). A double mechanism, mef(E) and erm(B), was detected in five isolates (2%). Ribosomal mutation was detected in 14 (6%) macrolide-resistant isolates in which no other determinant was found. Based on the telithromycin MICs, two groups of isolates were formed: 83.3% of the isolates belonged to a major group for which the telithromycin MIC range was <0.008 to 0.063 g/ml, and 16.7% belonged to a minor group for which the telithromycin MIC range was 0.125 to 8 g/ml. All except three isolates in the minor population carried a macrolide resistance gene.

Temporal Trends of Antimicrobial Resistance and Clonality of Invasive Streptococcus pneumoniae Isolates in Finland, 2002 to 2006

“…A multiplex PCR method (24) was used to detect the macrolide resistance determinants [mef, erm(B), and erm(A)] of 223 randomly selected ERY-nonsusceptible isolates (MIC Ն 0.5 mg/liter). For the multiplex PCR, primers from the following sources were used: mef (24,48), erm(B) (57), and erm(A) [erm(TR) subclass] (44). Separate PCRs were performed to differentiate efflux gene subclasses mef(A) and mef(E) in the 60 randomly selected mef-positive isolates described previously (48) by using published primers (10,14).…”

“…In the years 1999 to 2000, 7% of the invasive pneumococci isolated in Finland were resistant to macrolides and 4% were nonsusceptible to PEN, but multiresistance and resistance to fluoroquinolones or extended-spectrum cephalosporins were even rarer (43). Nevertheless, the 2002 study indicated that antimicrobial resistance among pneumococci in Finland was emerging (48).…”

Streptococcus pneumoniae Isolates Resistant to Telithromycin

“…However, due to the lack of breakpoints for the agar dilution method used in the study, the proportion of telithromycin nonsusceptibility could not be determined (20). The objectives of this study were to investigate the TEL susceptibility of isolates with a known macrolide resistance determinant using an approved CLSI disk diffusion method (4) and to compare these results with those obtained by the agar dilution (5) and CLSI broth microdilution (4) methods.…”

“…Bacterial isolates and susceptibility testing. Two hundred ten erythromycin-resistant (MIC Ն 0.5 g/ml) pneumococci with a known macrolide resistance determinant and 47 randomly selected erythromycin-susceptible pneumococci were investigated from among 1,007 Streptococcus pneumoniae isolates that were collected in 2002 in Finland for macrolide resistance surveillance purposes (20).…”

“…Pyrosequencing was used to detect mutations at the macrolide and ketolide binding sites (12,22). Primers for detecting mutations in positions 2058 to 2059 and 2611 of domain V have previously been published (12,20). Primers for amplifying loop 35 of domain II were 5Ј-GCGCCTTAGTATCATGACGTAGA-3Ј (biotinylated), 5Ј-AATGTCGACGCTAGCCCTAAAG-3Ј, and, for pyrosequencing, 5Ј-CGCTACCCACAAGTCA-3Ј.…”