Clonal distribution of penicillin-resistant Streptococcus pneumoniae 23F in France

Abstract

We studied the clonality of clinical isolates of Streptococcus pneumoniae 23F, the serotype most often associated with penicillin resistance in France. Clinical isolates obtained between November 1992 and April 1993 from nasopharyngeal samples from children with acute otitis media from different regions of the country were analyzed. The genetic polymorphism of penicillin-susceptible and -resistant 23F isolates (MIC, 2 mg/liter) was studied by pulsed-field gel electrophoresis. The resistant isolates were closely related, whereas the susceptible isolates were genetically heterogeneous. PCR amplification and restriction of the genes encoding penicillin-binding proteins (PBPs) 1A, 2B, and 2X also showed that the 24 resistant isolates had similar patterns which were very different from those of the susceptible isolates. All resistant isolates gave the same PBP pattern, with low affinities of PBPs for penicillin. Our results indicate that, in contrast to penicillinsusceptible 23F isolates, the penicillin-resistant 23F isolates have a single clonal origin, suggesting the rapid clonal spread of a resistant epidemic strain throughout the country.

Molecular Analysis by Pulsed-Field Gel Electrophoresis and Antibiogram of Streptococcus pneumoniae Serotype 6B Isolates from Selected Areas within the United States

“…The PFGE patterns of the remaining isolates were heterogeneous, with no more than five isolates having the same ApaI or SmaI pattern (CS ϭ 95%) and no more than four isolates having the same combined ApaI and SmaI PFGE patterns (CS ϭ 93%) ( Table 2). This is comparable with other studies that have shown that isolates of the same serotype are not necessarily more closely related to each other than isolates of different serotypes (5,8,11,16,26,27).…”

“…While serotyping and antibiotic susceptibility testing have been the most common epidemiologic tools for typing pneumococci, they have relatively limited discriminatory power (2). In contrast, genotyping methods such as multilocus enzyme electrophoresis (MLEE) (8,15,22,27,32), ribotyping (19,29), and PFGE (5,12,18) have shown greater discriminatory power for isolates within a single serogroup and have provided evidence for clonality and intercontinental spread of particular drugresistant pneumococci (8,11,19,21,25,26). In this study, we utilized PFGE following ApaI and SmaI restriction digestion of chromosomal DNA to determine genetic relatedness between pneumococcal serotype 6B isolates from different geographic locations in the United States.…”

“…Two enzymes with rare recognition sites were used: ApaI (Promega, Madison, Wis.) recognizes 5Ј-GGGCCC-3Ј; SmaI (Promega) recognizes 5Ј-CCCGGG-3Ј. Both of these enzymes have previously been used for PFGE analysis of S. pneumoniae chromosomal DNA (5,11,12,13,16,20,27).…”

“…Coefficients of similarity (CS ϭ number of shared bands ϫ 2 ϫ 100/total number of bands in the two samples) were determined for some isolates as a means of quantitating the relatedness or lack thereof among these isolates (11,12,18,20). When PFGE patterns between isolates following digestion with one restriction enzyme were compared, the CS value was given as a single percentage, whereas a range of CS values was given when isolates were analyzed after digestion with two restriction enzymes.…”

“…Over the past decade in the United States, there has been an increase in the number of reports of pneumococcal isolates that are either moderately or completely resistant to penicillin, erythromycin, and trimethoprim-sulfamethoxazole (TMP-SMZ) (28). Isolates resistant to these antibiotics appear to belong to a few selected serogroups and/or serotypes (6B, 14, 19F, 23F, 9V) (1,11,14). These serotypes are commonly associated with invasive disease and are most frequently isolated from children with serious infections (4).…”