Molecular Characterization of Penicillin-ResistantStreptococcus pneumoniaeIsolates Causing Respiratory Disease in the United States

Abstract

Three hundred twenty-eight (328) penicillin-resistant Streptococcus pneumoniae isolates collected in 39 states of the United States between October, 1996, and March, 1997, from (mostly adult) patients with respiratory disease were characterized by microbiological, serological, and molecular fingerprinting techniques, including determination of chromosomal macrorestriction pattern with pulsed-field gel electrophoresis (PFGE) and hybridization with DNA probes specific for various antibiotic resistance genes. The overwhelming majority of the isolates were in five serogroups (23, 6, 19, 9, 14). All isolates had penicillin MIC values of at least 2 microg/ml, but the collection also included isolates with MIC values as high as 16 microg/ml. Virtually all isolates (96.6%) were resistant to trimethoprim/sulfamethoxazole (SXT) and many isolates were also resistant to chloramphenicol (43%), tetracycline (55%), and erythromycin (65%). Resistance to levofloxacin was extremely rare. The molecular fingerprinting methods showed that a surprisingly large proportion (167 out of 328, or 50.9%) of the isolates belonged to two international epidemic clones of S. pneumoniae: clone A (127, or 38.7%) with properties indistinguishable from that of the 23F multiresistant "Spanish/USA" clone widely spread in Europe, Asia, Latin America, and South Africa, and clone B (40, or 12.2%) belonging to the "French" serogroup 9/14 clone widely spread in Europe and South America. Virtually all members of clone A were also resistant to chloramphenicol (cat+), tetracycline (tetM+), and SXT, and about 75% were also resistant to erythromycin (mefE+ or ermB+). Close to 30% (39 out of 127) of the clone A isolates expressed anomalous serotypes (primarily serotypes 19 and 14, and nontypable) and most likely represented spontaneous capsular transformants. Most of the 40 isolates (35/40) belonging to clone B expressed serotype 9, with five of the isolates expressing serotypes 14 or 19, or were nontypable. All members of this clone were resistant to penicillin and SXT with only occasional isolates showing resistance to macrolides, tetracycline, and chloramphenicol. The combination of microbiological tests and DNA hybridizations also allowed the identification of unusual strains, for instance, isolates that reacted with the tetM or mefE DNA probes without showing phenotypic antibiotic resistance, an isolate showing phenotypic macrolide resistance without hybridizing with either the ermB or mefE DNA probes, or isolates that hybridized with both of these DNA probes. In addition to clones A and B, another large portion of the S. pneumoniae isolates (112 of 328, or 34.1%) was represented by eight clusters, each with a unique PFGE type. These clusters, together with the clone A and clone B isolates, made up 85% of all the penicillin-resistant isolates identified in this survey in the United States. Both international clones and the unique clusters showed wide geographic dispersal: Clone A was present in 30 of the 39 states and clone B in 18. The data suggest that th...

A new serotype 14 variant of the pneumococcal Spain9V-3 international clone detected in the central region of Argentina

“…One of the best-characterized clones is Spain 9V -3, which appears to have emerged in Spain during the 1980s (Fenoll et al, 1991). This clone has been prevalent in France for the last 15 years and has been found in many other countries including Germany, the Netherlands, Poland, Denmark, Uruguay, Argentina, Brazil, Taiwan and South Africa (Castanheira et al, 2004;Coffey et al, 1999;Corso et al, 1998;Hermans et al, 1997a, b;Shi et al, 1998).…”

Genetic Relatedness of Levofloxacin-Nonsusceptible Streptococcus pneumoniae Isolates from North America

“…However, rapidly emerging resistance in the well-characterized Spain 23F -1 clone was apparently responsible for a fluoroquinolone resistance rate of 13.3% reported in Hong Kong during 2000 (20). This Spain 23F -1 clone is already responsible for an estimated 38.7% of penicillin-resistant S. pneumoniae respiratory tract isolates in the United States (6). While there have been many studies that address the epidemiology of S. pneumoniae with reduced susceptibility to macrolides and ␤-lactams (2,6,8,12,15,25,28,31), much remains unknown about the epidemiology of fluoroquinolone resistance in S. pneumoniae, since it has been documented only within the past few years and relatively small numbers of clinical isolates are available for study.…”

“…This Spain 23F -1 clone is already responsible for an estimated 38.7% of penicillin-resistant S. pneumoniae respiratory tract isolates in the United States (6). While there have been many studies that address the epidemiology of S. pneumoniae with reduced susceptibility to macrolides and ␤-lactams (2,6,8,12,15,25,28,31), much remains unknown about the epidemiology of fluoroquinolone resistance in S. pneumoniae, since it has been documented only within the past few years and relatively small numbers of clinical isolates are available for study. It is important to assess the characteristics of these organisms to gain a better understanding of their clonal relationships and their potential for clonal dissemination and to aid in the selection of appropriate antimicrobials for empirical therapy.…”

Molecular Epidemiology of Pneumococcal Carriage among Children with Upper Respiratory Tract Infections in Hanoi, Vietnam

“…In some countries and populations, up to 60% of the pneumococcal isolates are resistant to one or more antibiotics (1,12,22). A significant proportion of pneumococcal resistance is the result of the worldwide spread of a limited number of multidrug-resistant clones (6,15,35,39).…”