r te et sl 5 ew 00 l N 2 na ry tio ua na br ter Fe In 5 • n° State-of-the-Art The bioMérieux Did you know? Practical advice Streptococcus pneumoniae solution has always been an important pathogen ■ ■ ■ ■ for man and a big therapeutic success Antibiotic and Evaluation of Web sites why test S.pneumoniae the New VITEK® 2 ■ S.pneumoniae? in the early years of antibiotherapy Identifying System Resistance ■ what are the key with penicillin. News issues with S.pneumoniae For many years ■ NCCLS infections? this species was perfectly susceptible recommendations ■ What is the and antibiotic susceptibility testing ■ Antibiotics reference method for testing ■ ® was not necessary. VITEK 2 S.pneumoniae? phenotypes Then things changed dramatically about ■ The epidemiology of 25 years ago and resistance emerged S.pneumoniae in the South Hemisphere, spread to the world and now amounts State-of-the-Art to 50% of strains for penicillin as well as for other antibiotic families. This is a perfect example of emergence Antibiotic and of new resistance. Antibiotic testing of this species S.pneumoniae is now highly important and bioMérieux has developed a special VITEK2 card Keith Klugman MB BCh, PhD, is Professor of International Health at the Rollins School of Public Health at Emory University, in Atlanta, GA, USA. He is also Professor of Medicine in for this purpose with an appropriate the Division of Infectious Diseases of the School of Medicine at that University and a selection of antibiotics. Visiting Researcher in the Respiratory Diseases Branch of the Centers for Disease Control and Prevention (CDC). Knowledge about the resistance He is the Director of the Respiratory and Meningeal Pathogens Research Unit of the of this species is important University of the Witwatersrand, the Medical Research Council and the National Institute for and we are pleased to offer you Communicable Diseases in Johannesburg, South Africa. this new issue of our Professor Klugman is a Member of the US National Committee of the Identifying Resistance Newsletter International Union of Microbiological Societies. He has served on expert committees of the World Health Organization in Geneva, the Wellcome to share this information. Trust in London and the Institute of Medicine in Washington, DC. He serves as a member of the editorial board of 8 international journals on infectious disease and antimicrobial research. Professor Klugman's research interests are in antibiotics, antimicrobial resistance and vaccines for bacterial Dr. Mark Mackowiak pathogens particularly the pneumococcus. He has published more than 250 papers to date. VP for Research & Development, bioMérieux sa Keith Klugman Beta-lactams pneumococci are usually lower than those Although penicillin resistance was first of penicillin, these strains are more resistant described in the pneumococcus in 1967 to amoxicillin than to penicillin. The strains (15) the emergence of unusual strains were first isolated in France but have more of pneumococci with very high level recently also been found in the United resistance to amoxicillin has recently been States. Of recent concern also is the documented (7). These strains are unusual emergence of pneumococci with penicillin in that while the amoxicillin MIC’s of MIC’s ≥ 8 µg/ml. These strains remain rare, from diagnosis, Identifying Resistance International Newsletter • February 2005 Identifying Resistance International Newsletter • February the seeds of better health State-of-the-Art Antibiotic and S.pneumoniae Several antibiotics can inhibit S.pneumoniae. And resistance exist for most of them. fig. 1 BLA b-lactams, VAN vancomycin, ERY erythromycin, TET tetracyclin, CMP chloramphenicol, RIF rifampin, SXT trimethoprime+sulfamethoxazole, QUN quinolones The three resistance mechanisms are: target alteration, efflux and antibiotic inactivation. but there is evidence that they may be to create mosaic genes (8), the discovery common in certain geographic areas of the of the critical role played by murM in United States and they have strong clonal the biosynthesis of the branched chain origins. While changes in penicillin-binding precursors required to cross-link the cell proteins (PBP’s) remain the basis of beta- wall of resistant pneumococci is providing lactam resistance in the pneumococcus by new insight into non-PBP mechanisms that the transformation of pneumococcal pbp may be important in the development of genes with DNA from viridans streptococci beta-lactam resistance in this pathogen (13). Within the setting of the specific PBP shown that mutations in the L4 and L22 the enzyme substrates of the drugs (1, 18). changes found in a highly penicillin-resistant proteins can confer clinically relevant Hungarian strain with an MIC of 16 µg/ml, macrolide resistance in the pneumococcus Chloramphenicol it was found that murM played a critical (23, 31) and combinations of mutation in Resistance to chloramphenicol in the role in the expression of that very high these genes and rRNA can confer pneumococcus is mediated by the level of resistance (28). The role of murM resistance to the streptogramins as well as acquisition of a gene encoding is however complex, and an altered murM to the ketolides (26). chloramphenicol acetyl transferase. An does not seem to play an essential role in interesting aspect of this mechanism is that the manifestation of all high-level penicillin Oxazolidinones the gene is located on a plasmid, probably resistant pneumococci (9). The first reports of linezolid - resistant derived from the staphylococcus, which has pneumococci have been made (12) and entered the pneumococcus by linearization Macrolides the molecular basis of the resistance is and inclusion on a transposable element The dominant mechanisms of macrolide being sought. (33). resistance in the pneumococcus are the efflux mechanism (predominantly mefA) Tetracycline Vancomycin and the presence of the rRNA methylation Most tetracycline resistance in the Although no vancomycin-resistant gene, ermB which additionally confers pneumococcus is conferred by the pneumococcus has been described, there resistance to lincosamides such as presence of the tetM gene and although are reports of a tolerance phenotype, the clindamycin and to streptograminB. Usually the tetO gene has been described in clinical role of which remains to be fully pneumococci have only one of these two discrete geographic locations (South established (22, 24). resistance genes but the concurrence of the Africa and USA), these strains remain rare genes was described in South Africa, in a (19, 34). Fluoroquinolones global pneumococcal clone called the The emerging resistance to Taiwan19F – 14 clone (21). This clone now Rifampin fluoroquinolones is mediated mostly by comprises a significant percentage of The molecular basis of resistance to the changes in the QRDR of the topoisomerase macrolide - resistant pneumococci in many rifamycins is mutation in the beta subunit of enzymes. There is also efflux mediated other countries. Closely related versions of RNA polymerase rpoB. A number of resistance that is thought only to be the mef and erm genes exist primarily in mutations in the gene associated with clinically relevant mostly at low levels of Streptococcus pyogenes. The ermA gene resistance have been described (10, 25). resistance. Although there is evidence for from Streptococcus pyogenes has been clonal spread of fluoroquinolone resistance found in a pneumococcal strain from Trimethoprim-Sulfamethoxazole in Hong Kong (16), most of the emerging Greece (29) and together with the ermB The molecular basis of resistance to these resistance in North America has been gene in a pneumococcus from Spain (3). agents are base mutations, insertions sporadic mutation in strains isolated The mefA gene from the pneumococcus, and deletions in the genes encoding from patients with a previous history formerly called mefE, is located in a transposable element called MEGA (macrolides efflux genetic assembly) MOSAIC GENES (14), which lacks the genes for transposition in transposon1207.1 around PBP 1A 1B 2X 2A 2B 3 the mefA gene from Streptococcus pyogenes, which has also been wild documented in S. pneumoniae (27). Of particular interest is the recent emergence of mutation based resistance to macrolides Tolerant in the pneumococcus. The pneumococcus has four rRNA genes and there is a dose- response to increasing levels of resistance Low level R. as mutations occur in the macrolide - binding areas of the RNA (30). Resistance High level R. to macrolides in pneumococci bearing these mutations have been found rarely, but are widely distributed, having been High level R. found in Europe, North America, South East Asia and Australia (11). It has also been High level R. References 1. Adrian, P. V., and K. P. Klugman. 1997. Mutations in the 20. McGee, L., C. E. Goldsmith, and K. P. Klugman. 2002. dihydrofolate reductase gene of trimethoprim-resistant isolates of Fluoroquinolone resistance among clinical isolates of Streptococcus pneumoniae. Streptococcus pneumoniae belonging to international Antimicrobial Agents & Chemotherapy 41:2406-13. multiresistant clones. Journal of Antimicrobial Chemotherapy 49:173-176. 2. Balsalobre, L., M. J. Ferrandiz, J. Linares, F. Tubau, and A. G. de la Campa. 2003. Viridans group streptococci are donors in horizontal 21. McGee, L., K. P. Klugman, A. Wasas, T. Capper, and A. Brink. 2001. transfer of topoisomerase IV genes to Streptococcus pneumoniae. Serotype 19f multiresistant pneumococcal clone harboring two of fluoroquinolone