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Journal of Clinical Microbiology, August 2007, p. 2754-2755, Vol. 45, No. 8
0095-1137/07/$08.00+0     doi:10.1128/JCM.00579-07
Copyright © 2007, American Society for Microbiology. All Rights Reserved.

LETTER TO THE EDITOR

Three New Macrolide Efflux (mef) Gene Variants in Streptococcus agalactiae{triangledown}


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LETTER
 
Streptococcus agalactiae (group B streptococcus [GBS]) is the most common cause of neonatal sepsis (9). Penicillin is used for intrapartum prophylaxis, but erythromycin or clindamycin is recommended for patients allergic to penicillin (3). There are two major mechanisms of erythromycin resistance in S. agalactiae, (i) erythromycin ribosomal methylase, mediated by ermB, ermA, ermTR, or ermC, which confers cross-resistance to macrolides, lincosamides, and streptogramin B (MLSB phenotype), and (ii) a less common macrolide efflux pump, mediated by mef (7), which confers resistance to 14- and 15-membered macrolides only (M phenotype). The major mef variants, mefE and mefA, were originally identified in S. pneumoniae and S. pyogenes, respectively (5, 11); both are found in S. agalactiae (2), although mefE is much more common (4, 12).

Recently, we tested 512 GBS isolates from Australia, Hong Kong, and South Korea by using a multiplex PCR-based reverse line blot (mPCR/RLB) assay to identify nine resistance markers and identified mef in 22 (12). However, we did not distinguish mef variants. Subsequently, we tested a total of 1,629 GBS clinical isolates (including the original 512) from nine countries by using the same mPCR/RLB, except that two new probe pairs, specific for mefA and mefE, were added (Table 1). Isolates were typed by using a three-set genotyping system which identifies the molecular serotype (MS), surface protein genes, and mobile genetic elements, as described previously (8). Antibiotic susceptibilities to erythromycin, clindamycin, and tetracycline were measured by E-test (AB Biodisk; Australia Laboratory Services Pty. Ltd.) and interpreted as recommended by the Clinical and Laboratory Standards Institute (12).


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  		TABLE 1. Oligonucleotide primers and probes used in this study

Forty five (2.7%) of 1,629 isolates were positive for mef, and of these, 35 contained mefE, 7 contained mefA, and 3 gave weak or variable signals with mefE- and mefA-specific probes. These three isolates were among 16 mef-positive isolates from Hong Kong. Their genotypes and phenotypic susceptibilities to erythromycin, clindamycin, and tetracycline are shown in Table 2. All three had the M phenotype and MS Ia but atypical genotypes. MS Ia usually has the surface protein gene alp1 and insertion sequence IS1381 (8, 10). Two of these isolates had alp1 but, instead of IS1381, carried the type II intron GBSi1, usually found in MS III but rarely in other serotypes (10). The other isolate had neither the surface protein gene nor the insertion sequence.


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  		TABLE 2. Characteristics and comprehensive genotyping results of three mef variants

From each of these three isolates, mef was amplified and sequenced with the primers shown in Table 1. The full sequences indicated that all were novel mef variants not previously described in a GBS. They were deposited in GenBank with accession numbers DQ445269 to DQ445271. DQ445271 and DQ445270 were 99% similar to each other but only 88% and 89% homologous with mefE (GenBank accession no. AF227521) and mefA (GenBank accession no. AY064721), respectively. They shared 99 to 100% homology with a mef variant recently identified in Streptococcus dysgalactiae (a group G streptococcus) (GenBank accession no. AM168138 and AY355405) (1). DQ445269 has not been described before; it had 89% homology with mefA (GenBank accession no. AY064721) and the novel group G streptococcus mef gene (GenBank accession no. AY355405), 91% homology with mefE (GenBank accession no. AY227521), and 92% homology with another mef variant, mefI, described in Streptococcus pneumoniae (GenBank accession no. AJ971089) (6). The inconsistent mPCR/RLB results for these isolates can be explained by mutations in the mefAESb and mefAEAb regions. New primers and probes will be required to detect them reliably by mPCR/RLB. For these novel mef variants, we propose the names mefG (for DQ445270 and DQ445271) and mefB (for DQ445269) to reflect the beta-hemolytic streptococcus groups in which they were first identified.

These findings and the atypical genotype patterns suggest that these strains have arisen by recombination. Further investigation will be required to determine their clinical significance.


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ACKNOWLEDGMENTS
 
We sincerely thank Margaret Ip, Department of Microbiology, The Chinese University of Hong Kong, and the Prince of Wales Hospital, Hong Kong, for allowing us to study their isolates.

This work was partially supported by National Health and Medical Research Council grant 358351 to G.L.G. and F.K.


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FOOTNOTES
 
{triangledown} Published ahead of print on 27 June 2007. Back


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REFERENCES
 
    1
  1. Amezaga, M. R., and H. McKenzie. 2006. Molecular epidemiology of macrolide resistance in beta-haemolytic streptococci of Lancefield groups A, B, C and G and evidence for a new mef element in group G streptococci that carries allelic variants of mef and msr(D). J. Antimicrob. Chemother. 57:443-449.[Abstract/Free Full Text]
    2. 2
  2. Arpin, C., H. Daube, F. Tessier, and C. Quentin. 1999. Presence of mefA and mefE genes in Streptococcus agalactiae. Antimicrob. Agents Chemother. 43:944-946.[Abstract/Free Full Text]
    3. 3
  3. Baker, C. J., N. A. Halsey, and A. Schuchat. 1999. 1997 AAP guidelines for prevention of early-onset group B streptococcal disease. Pediatrics 103:701.[Free Full Text]
    4. 4
  4. Clancy, J., F. Dib-Hajj, J. W. Petitpas, and W. Yuan. 1997. Cloning and characterization of a novel macrolide efflux gene, mreA, from Streptococcus agalactiae. Antimicrob. Agents Chemother. 41:2719-2723.[Abstract]
    5. 5
  5. Clancy, J., J. Petitpas, F. Dib-Hajj, W. Yuan, M. Cronan, A. V. Kamath, J. Bergeron, and J. A. Retsema. 1996. Molecular cloning and functional analysis of a novel macrolide-resistance determinant, mefA, from Streptococcus pyogenes. Mol. Microbiol. 22:867-879.[CrossRef][Medline]
    6. 6
  6. Cochetti, I., M. Vecchi, M. Mingoia, E. Tili, M. R. Catania, A. Manzin, P. E. Varaldo, and M. P. Montanari. 2005. Molecular characterization of pneumococci with efflux-mediated erythromycin resistance and identification of a novel mef gene subclass, mef(I). Antimicrob. Agents Chemother. 49:4999-5006.[Abstract/Free Full Text]
    7. 7
  7. Klaassen, C. H. W., and J. W. Mouton. 2005. Molecular detection of the macrolide efflux gene: to discriminate or not to discriminate between mef(A) and mef(E). Antimicrob. Agents Chemother. 49:1271-1278.[Free Full Text]
    8. 8
  8. Kong, F., D. Martin, G. James, and G. L. Gilbert. 2003. Towards a genotyping system for Streptococcus agalactiae (group B streptococcus): use of mobile genetic elements in invasive Australasian isolates. J. Med. Microbiol. 52:1-8.[Free Full Text]
    9. 9
  9. Schuchat, A. 1998. Epidemiology of group B streptococcal disease in the United States: shifting paradigms. Clin. Microbiol. Rev. 11:497-513.[Abstract/Free Full Text]
    10. 10
  10. Sun, Y., F. Kong, Z. Zhao, and G. L. Gilbert. 2005. Comparison of a three-set genotyping system with multilocus sequence typing for Streptococcus agalactiae (group B streptococcus). J. Clin. Microbiol. 43:4704-4707.[Abstract/Free Full Text]
    11. 11
  11. Tait-Kamradt, A., J. Clancy, M. Cronan, F. Dib-Hajj, L. Wondrack, W. Yuan, and J. Sutcliffe. 1997. mefE is necessary for the erythromycin-resistant M phenotype in Streptococcus pneumoniae. Antimicrob. Agents Chemother. 41:2251-2255.[Abstract]
    12. 12
  12. Zeng, X., F. Kong, H. Wang, A. Darbar, and G. L. Gilbert. 2006. Simultaneous detection of nine antibiotic resistance-related genes in Streptococcus agalactiae using multiplex PCR and reverse line blot hybridization assay. Antimicrob. Agents Chemother. 50:204-209.[Abstract/Free Full Text]
Yongwei Cai
Department of Dermatology
Hangzhou Third People's Hospital
Hangzhou, Zhejiang Province, Peoples Republic of China

Fanrong Kong
Gwendolyn L. Gilbert*
Centre for Infectious Diseases and Microbiology (CIDM)
Institute of Clinical Pathology and Medical Research (ICPMR)
Westmead, New South Wales, Australia

* Phone: (612) 9845 6255, Fax: (612) 9893 8659, E-mail: lyng{at}icpmr.wsahs.nsw.gov.au

Journal of Clinical Microbiology, August 2007, p. 2754-2755, Vol. 45, No. 8
0095-1137/07/$08.00+0     doi:10.1128/JCM.00579-07
Copyright © 2007, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Varaldo, P. E., Montanari, M. P., Giovanetti, E. (2009). Genetic Elements Responsible for Erythromycin Resistance in Streptococci. Antimicrob. Agents Chemother. 53: 343-353 [Full Text]  

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