Journal of Antimicrobial Chemotherapy (1999) 44, 19-25
© 1999 The British Society for Antimicrobial Chemotherapy
A variety of Gram-positive bacteria carry mobile mef genes
a Department of Pathobiology, Box 357238, School of Public Health and Community Medicine, University of Washington, Seattle, WA 98195-7238, USA b Department of Microbiology, University of Leeds, Leeds LS2 9JT, UK
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Abstract |
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The mefE gene codes for a membrane bound efflux protein, which confers resistance to macrolides, and has been identified in Streptococcus pneumoniae. A variety of Gram-positive organisms were examined. Twenty-six isolates of S. pneumoniae carried mefE and were resistant to erythromycin (MIC of 2-16 mg/L). Two additional isolates of Em r S. pneumoniae carried both ermB and mefE (MIC of 16-128 mg/L). One Micrococcus luteus, one Corynebacterium jeikeium, three Corynebacterium spp., two viridans streptococci and seven Enterocccus spp. also carried mefgenes. It was possible to move the mef gene from all 11 S. pneumoniae tested to susceptible S. pneumoniae and/or Enterococcus faecalis recipients. The addition of DNase (1 g/L) did not affect the gene transfer. It was also possible to move the mef gene from donor Enterococcus spp., viridans streptococci, M. luteus, C. jeikeium and Corynebacterium spp. to E. faecalis recipients. Transconjugant isolates were resistant to erythromycin (MIC
16
mg/L). Hybridization with a labelled mef oligonucleotide probe against Southern blots
and
bacterial dot blots confirmed the presence of the mef genes. This is the first time that a
mobile mef gene has been identified in four different genera, from three distinct
geographical locations. |
Introduction |
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TopAbstractIntroductionMaterials and methodsResultsDiscussionReferences |
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World-wide, the prevalence of antibiotic resistant Streptococcus pneumoniaehas increased, 1,2,3,4 with five serogroups (6, 9, 14, 19 and 23) having developed resistance to two or more classes of antibiotic. 5 Most resistance (with the exception of that to ß-lactams), has been obtained through the acquisition of new genes, usually associated with conjugative transposons. 6,7 Resistance to erythromycin in the first resistant S. pneumoniae isolates described was found to be due to the presence of an rRNA methylase gene, ermB, which conferred resistance to the macrolides, lincosamides and streptogramin B antibiotics. This gene is still commonly found in many streptococcal species. 8,9,10,11
More recently, resistance to macrolides in the absence of resistance to lincosamides or streptogramin B has been described in S. pneumoniae and ß-hemolytic (Lancefield Group A) streptococci. This is determined by the presence of a membrane bound efflux protein, encoded by the mef genes, mefA or mefE. 12,13,14,15,16 mefA has been cloned from Streptococcus pyogenes and has been identified in Lancefield Group C and G streptococci originating from Finland. 14,16 The mefEgene has been identified and cloned from S. pneumoniae in the USA. 13,15,17 The two genes have 90% nucleotide sequence identity, and using DNA probes for conserved regions, both mefA and mefE will be detected. In this study, probes to the conserved regions of the genes were used. The mef gene will be referred to as mefE for S. pneumoniae and the mef gene for other species.
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Materials and methods |
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TopAbstractIntroductionMaterials and methodsResultsDiscussionReferences |
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Thirty-four isolates of S. pneumoniae, which were erythromycin resistant (Em r) (MIC
2 mg/L), were included in the study. Twenty-four
isolates from cases of invasive disease were collected between 1995 and 1996, during a
Washington
State Surveillance Study; four Em
r S. pneumoniae resulted from a Paediatric
Nasopharyngeal Carriage Study, conducted in 1996, in Seattle; and a further six Em
r invasive isolates of S. pneumoniae were obtained in
1997 from the Washington State Health Department. Serotypes of the S. pneumoniae isolates were initially determined by the Quellung reaction
18 in this laboratory and subsequently confirmed by the
University of Washington Medical Center, Seattle, and/or the Centers for Disease Control and
Prevention (CDC) in Anchorage, Alaska. In addition, ten Em
r Micrococcus luteus isolates and 20 Em
r Corynebacteriumspp. isolates (one Corynebacterium jeikeium,
one Corynebacterium Group G2, ten Corynebacterium Group ANF, three Corynebacterium Group A, three Corynebacterium aquaticum and two Corynebacterium spp.) collected in the UK during 1997 from skin cultures of
patients attending an acne clinic at the University of Leeds were examined. Thirty-two Em
r Enterococcus spp. obtained from normally
sterile sites, from patients at the University of Washington Medical Center Clinical Microbiology
Laboratory, Seattle, were examined. Unfortunately, no patient information was available on these
isolates. Twenty-nine viridans streptococcal isolates, which grew on erythromycin supplemented
media
(10 mg/L), collected from oral cultures of children participating in a dental study in Lisbon,
Portugal,
were also screened. Resistance to erythromycin was confirmed for mef positive isolates
by
micro-broth dilution or agar dilution as described in NCCLS guidelines.
19,20 Streptococcus spp. were grown on Brucella blood agar (BA) (Difco, Detroit, MI, USA) supplemented with 5% sheep red blood cells and incubated with 5% CO 2 at 36.5°C. M. luteus and Corynebacterium spp. were grown on Brain Heart Infusion Agar (BHIA) (Difco) supplemented with 5% NAD and 5% Vitamin K- haemin. Enterococcus faecalis JH2-2 was grown on BHIA without supplements. Bacteria for DNA dot blots and DNA extractions were grown overnight at 36.5°C in BHI broth (Difco) supplemented with 0.03 M D-glucose and 0.04% DL-threonine. 21,22
Mating experiments
Ten Em r S. pneumoniae from Seattle and S. pneumoniae 02J1048, known to contain the mefE gene, from Pfizer, Inc. (Groton, CT, USA), 15 Em r M. luteus 64, four Em r Corynebacterium spp. (214, 260, 274 and 388), three Em r Enterococcus spp. (102, 106 and 138) and two Em r viridans streptococci (7405B2-47 and 7405B2-48) were used as donors. The donor organisms were susceptible to fusidic acid, rifampicin and streptomycin. E. faecalis JH2-2 was used as a recipient (erythromycin susceptible), and had been previously selected for chromosomal resistance to rifampicin (25 mg/L) and fusidic acid (25 mg/L) (Em s Rif r Fus r). 21,23 The other recipient was a clinical isolate, S. pneumoniae 915, a 6B serotype from Alaska, which was susceptible to erythromycin and, by stepwise selection, made chromosomally resistant to streptomycin (1 g/L), fusidic acid (25 mg/L) and rifampicin (25 mg/L) (Em s Rif r Fus r Str r). 21 Donor and recipient bacteria were grown separately at 36.5°C overnight on BA or BHIA plates. Each isolate was suspended in 0.5-1.0 mL of BHI broth (Difco) to a density of approximately 10 9 cells/mL (3 McFarland). Donor and recipient at a 1:1 (donor to recipient) ratio for S. pneumoniae to S. pneumoniaematings,or a 5:1 (donor to recipient) ratio for all other matings, were mixed, plated directly on to BA plates, and incubated in CO 2 at 36.5°C for 48 h. 21 After incubation, the mating mixture was serially diluted on to antibiotic supplemented plates as previously described. 21,22,23 Transconjugants from the S. pneumoniae-S. pneumoniae and S. pneumoniae-viridans streptococcus matings were selected on BA plates supplemented with 2 mg/L of erythromycin and 25 mg/L of rifampicin. S. pneumoniae transconjugants grew on BA plates supplemented with either erythromycin (2 mg/L), rifampicin (25 mg/L), fusidic acid (25 mg/L) or streptomycin (1 g/L). These isolates were identified biochemically as S. pneumoniae. 18 The E. faecalis tranconjugants were selected on BHIA supplemented with erythromycin 10 mg/L and either rifampicin 25 mg/L. E. faecalis tranconjugants grew in the presence of rifampicin (25 mg/L), erythromycin (10 mg/L) or fusidic acid (25 mg/L), as previously described, 23 and were identified biochemically as E. faecalis. 24 Plates with no growth were held for 7 days. All matings were done in duplicate. Some matings were done in the presence of DNase (1 g/L) (Sigma Chemical Co., St Louis, MO, USA) as previously described, to rule out transformation. 25 Duplicate matings were performed without DNase, and the frequencies were compared with the frequencies of the matings with DNase, and were shown to be the same. mef was detected using labelled mef oligonucleotide probe hybridization of bacterial dot blots and/or Southern blots.
Labelled probes
The oligonucleotide probes used were MF4 (sequence: 5'-ACC GAT TCT ATC AGC AAA-3'), MF5 (sequence: 5'-GGT GCT GTG ATT GCA TCT ATT AC-3'), and ErmB F (sequence: 5'-GAA AAG GTA CTC AAC CAA ATA-3'). 26 The probes were labelled using the Genius Oligonucleotide Labeling Kit (Boehringer Mannheim, Indianapolis, IN, USA), following the manufacturer's procedures for purified Southern blots and whole cell DNA dot blots only. 32P-labelled probes were used for whole bacterial cell dots using T4 polynucleotide kinase (10 U) (Promega, Madison, WI, USA) as previously described. 22
Whole cell DNA extraction
Whole cell DNA was prepared from isolates and transconjugants, using cells grown overnight, in 100 mL of supplemented BHI broth, as previously described. 27 After extractions with Tris-saturated phenol, pH 8.0, and chloroform, the DNA was precipitated with ethanol, resuspended in nanopure sterile water and stored at -20°C until needed. The whole cell DNA was run on a 0.7% agarose gel and Southern blots were prepared. 28
Dot blots
Overnight bacterial growth (1 mL) in supplemented BHI broth was placed into 1.5 mL sterile
Eppendorf tubes, centrifuged at 10,000 rpm for 2 min, and the supernatant decanted. The
bacterial
pellet was resuspended with 1 mL BHI broth to create a turbid suspension (corresponding to 3
McFarland; 10
9 bacteria/mL). Suspension (200 µL) was spotted onto GeneScreenPlus
membrane (NEN Research, Boston, MA, USA), dried, treated with 0.5 M NaOH for 10 min, 1
M
Tris- HCl for 3 min and 1 M Tris- HCl with 1.5% NaCl, pH 7.5, for 10 min. The membrane was
dried, washed twice in chloroform- isoamylalcohol (24:1), rinsed in water twice, then washed in
1 M
Tris- HCl, and 1 M Tris- HCl with 1.5% NaCl, and baked at 80°C for 1 h. The filters were
stored at room temperature until labelled.
28
Polymerase chain reaction (PCR)
A PCR assay was used as a second method for detection of the mefgenes in donors and transconjugants. The PCR assay used 40 ng of genomic DNA from S. pneumoniae 02J1048 as a positive control, and 40 ng genomic DNA as a template from S. pneumoniae, Micrococcus, Corynebacterium spp., viridans streptococci and Enterococcus spp. The primers used were: MF4a (5'-ACC GAT TCT ATC AGC AAA G-3') and MF6 (5'-GGA CCT GCC ATT GGT GTG-3'). 17 Both are in the conserved regions of mefA and mefE genes. Each reaction contained 2 units of Taq polymerase (Perkin Elmer- Cetus, Norwalk, CT, USA), 200 µM deoxynucleoside triphosphates, 1x PCR buffer (1.5 mM MgCl 2) and 100 ng of each primer. Using a Perkin Elmer- Cetus thermal cycler, the reactions were carried out by denaturing at 94°C for 1 min, annealing at 37°C for 1 min and elongation at 72°C for 2 min for 35 cycles. The PCR products were lyophilized, resuspended in 1/10 volume sterile water, and run on a 1.5% agarose gel with 0.5x TBE running buffer. Ethidium bromide staining allowing visualization of PCR bands and Southern blots were prepared. The 940 bp PCR product was confirmed by hybridization with a labelled internal mef probe, MF5 (5'-GGT GCT GTG ATT GCA TCT ATT AC-3'). Negative and positive controls were included in each run.
DNA- DNA hybridization
Southern blots of the uncut whole cell DNA were prepared on Magnagraph nylon (Micron Separation Inc., Westboro, MA, USA) and hybridized with nonradiolabelled oligonucleotide probe MF4 or ermB F following the manufacturer's directions (Boehringer). Southern blots of the PCR assay were prepared using the Magnagraph nylon membrane (Micron Separation, Inc.) and hybridized with labelled MF5. Detection of the probe was performed using the CDP-Star reagent at a 1:1000 dilution, following the manufacturer's instructions (Boehringer Mannheim Biochemica). DNA dot blots containing 30-300 µg of purified whole cell DNA were placed on GeneScreenPlus membrane (NEN Research Products) and hybridized with the nonradiolabelled probe. The whole bacterial cell dot blots were placed on GeneScreenPlus membrane and hybridized with a 32P-labelled oligonucleotide probe. 22
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Results |
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TopAbstractIntroductionMaterials and methodsResultsDiscussionReferences |
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Detection of the mef and ermB genes in four genera of bacteria
Sixty-three (50%) of the total 125 bacterial isolates tested hybridized with the mef
and/or ermB probes (Table I). Twenty-six (76%) of the 34 S. pneumoniae isolates tested hybridized with the mef probe only, two isolates
hybridized with mef and ermB probes, and four isolates hybridized with the ermB probe only (Table I). One of the M. luteus, four Corynebacterium spp.
(one C. jeikeium, one Corynebacterium Group A, and two Corynebacterium spp.), seven of the Enterococcus spp. and two viridans
streptococci hybridized with the mef probe. Six Enterococcus spp., one M.
luteus, one Corynebacterium(Group A) and nine viridans streptococci hybridized
with the ermB probe (Table I). The PCR assay with
hybridization of the internal MF5 probe confirmed the
presence of the mef gene in the isolates. Correlations were found between low-level
erythromycin resistance (MIC of 2- 4 mg/L) and the presence of the mefE gene in S.
pneumoniae, or high-level erythromycin resistance (MIC of 16 to >128 mg/L) with ermB, or mefE and ermB in S. pneumoniae (Table II). In Enterococcus spp. there were similar correlations between low-level
erythromycin resistance (MIC of 2-16 mg/L) and the presence of the mef gene and
high-level
resistance (MIC 32 mg/L) and the presence of ermB. In viridans streptococci,
low-level
erythromycin resistance (MIC of 2-4 mg/L) was associated with the mef gene, but both
low-
and high-level resistance was seen in the isolates with the ermB gene (Table
II). MIC in M. luteus and Corynebacterium spp. did not correlate
with the
presence of the mef gene, but the numbers tested were small (Table II). Other ermgenes (ermA, ermC, etc.) were not examined.
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Conjugal transfer of the mef gene
Erythromycin resistance erm genes are often associated with mobile elements.
Therefore, it
was of interest to see whether the mef gene was associated with mobile elements in
these
isolates. It was possible to move the mefgene from three of four S. pneumoniae donors to the S. pneumoniae recipient, at frequencies ranging from 10
-6 to 10
-7 per recipient (Table III). To selected matings,
DNase (1
g/L) was added to the mating mixtures and the frequencies were compared with matings without
DNase. The frequencies of transfer were within 0.5 log
10 with DNase, compared with the same matings without DNase, suggesting that
conjugation rather than transformation was taking place in S. pneumoniae-S.
pneumoniae matings. Two mating pairs are shown inTable III. In
these three S.
pneumoniae donors and eight other (total 11) S. pneumoniae donors, transfer of the
mefE gene to the E. faecalis recipient could be demonstrated, at frequencies
ranging from
10
-6 to 10
-8 per recipient (Table III).
The mef gene could also be moved from M. luteus 64, C. jeikeium388
and Corynebacteriumspp. (214, 274) to E. faecalis JH2-2, at frequencies of
10
-6 to 10
-8 per recipient (Table III).
The same transfer of mefgenes was effected from Enterococcusspp. (102, 106,
138)
and viridans streptococci donors (7405B2-47, 7405B2-48) to E. faecalis JH2-2, at
frequencies of 10
-8 and 10
-6 per recipient, respectively (Table III). The MIC of
erythromycin in the transconjugants from each mating with the various donors was five-fold
higher than
the MIC of the parental recipient (0.5 mg/L vs 16 mg/L). Whole cell DNA from donors,
recipients
and transconjugants were run on 0.7% agarose gel and Southern blots were prepared.
Transconjugants
hybridized with the labelled mef probe, whereas the susceptible recipients did not. The
probe
hybridized with the chromosomal fraction, suggesting a chromosomal location (data not shown).
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Discussion |
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TopAbstractIntroductionMaterials and methodsResultsDiscussionReferences |
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The most important finding of this study was that the mef genes examined were associated with DNase resistant mobility, suggesting a conjugative element in four Gram-positive genera, from three distinct geographical locations (USA, UK and Portugal) (Table III). Transfer occurred between S. pneumoniae-S. pneumoniae, as well as between unrelated genera. Plasmids were not detected in the donors or transconjugants tested. The mef probe hybridized with the chromosomal fraction in Southern blots of uncut DNA, suggesting a chromosomal location. Although the mef genes were transferred (Table III), the nature of the putative conjugative elements is unknown, but could be related to previously described conjugative elements found in streptococci. 7 As this paper was being reviewed, a paper was published which demonstrated the plasmid-free conjugal transfer of the mefgene from S. pyogenesto JH2-2 E. faecalisrecipient. 29
In earlier studies, the mef genes have been found in a limited number of hosts (S. pneumoniae, S. pyogenes and Lancefield Groups C and G streptococci). 14,15,16,29 This study has demonstrated that the mef genes are present in three new Em r Gram-positive genera (Corynebacterium, Enterococcus and Micrococcus) (Table I) as well as in Em r viridans streptococci. Recently sequencing of the PCR fragments from M. luteus and Corynebacterium spp. 388 and 214 showed 93%, 93% and 95% DNA homology with the mefE GeneBank sequence, respectively. Twenty-six S. pneumoniae carried the mefE gene, and two additional isolates carried both the mefE and ermB genes.
A correlation was found between lower erythromycin MIC (2-4 mg/L) for isolates carrying the mefE gene in S. pneumoniae and for enterococci (2-16 mg/L) carrying the mef
gene. In contrast, isolates with higher MICs (16 mg/L) carried the ermB gene,
either
alone or in addition to the mef gene (Table II). More examples
from
different locations will need to be studied to determine whether the presence of these genes
would
predict the therapeutic usefulness of clindamycin. What impact, if any, the differences seen
between
carriage of mef versus ermgenes will have on treatment of S. pneumoniae or
other Gram-positive disease has not yet been examined. It is clear from this study that the host
range of
the mef genes in Gram-positive bacteria needs to be more fully examined.
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Acknowledgments |
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This work was presented in part at the 38th Interscience Conference on Antimicrobial Agents and Chemotherapy, September 1998. This study was supported in part by the NIH National Institute of Dental Health (Grant U01-DE-11894 and Contract N01-DE-72623). We wish to thank Dr T. Fritsche and Ms S. Swanzy from the Department of Laboratory Medicine, University of Washington Medical Center, Seattle, for the Enterococcus spp., and Mr S. Deliganis from Northwest Pharmaceutical Research Network for S. pneumoniae isolates. We also wish to thank Dr A. Parkinson at the Arctic Investigations Program of the Centers for Disease Control and Prevention, Anchorage, Alaska, for confirmation of S. pneumoniae serotypes.
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Notes |
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* Corresponding author. E-mail: marilynr{at}u.washington.edu
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References |
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Received 21 October 1998; returned 5 February 1999; revised 17 February 1999; accepted 12 April 1999
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A. A. Watters, R. N. Jones, J. A. Leeds, G. Denys, H. S. Sader, and T. R. Fritsche Antimicrobial activity of a novel peptide deformylase inhibitor, LBM415, tested against respiratory tract and cutaneous infection pathogens: a global surveillance report (2003-2004) J. Antimicrob. Chemother., May 1, 2006; 57(5): 914 - 923. [Abstract] [Full Text] [PDF]
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K. K. Ojo, M. J. Striplin, C. C. Ulep, N. S. Close, J. Zittle, H. Luis, M. Bernardo, J. Leitao, and M. C. Roberts Staphylococcus Efflux msr(A) Gene Characterized in Streptococcus, Enterococcus, Corynebacterium, and Pseudomonas Isolates Antimicrob. Agents Chemother., March 1, 2006; 50(3): 1089 - 1091. [Abstract] [Full Text] [PDF]
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I. Cochetti, M. Vecchi, M. Mingoia, E. Tili, M. R. Catania, A. Manzin, P. E. Varaldo, and M. P. Montanari Molecular Characterization of Pneumococci with Efflux-Mediated Erythromycin Resistance and Identification of a Novel mef Gene Subclass, mef(I) Antimicrob. Agents Chemother., December 1, 2005; 49(12): 4999 - 5006. [Abstract] [Full Text] [PDF]
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J. M. Marimon, A. Valiente, M. Ercibengoa, J. M. Garcia-Arenzana, and E. Perez-Trallero Erythromycin Resistance and Genetic Elements Carrying Macrolide Efflux Genes in Streptococcus agalactiae Antimicrob. Agents Chemother., December 1, 2005; 49(12): 5069 - 5074. [Abstract] [Full Text] [PDF]
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T. Bogdanovich, D. Esel, L. M. Kelly, B. Bozdogan, K. Credito, G. Lin, K. Smith, L. M. Ednie, D. B. Hoellman, and P. C. Appelbaum Antistaphylococcal Activity of DX-619, a New Des-F(6)-Quinolone, Compared to Those of Other Agents Antimicrob. Agents Chemother., August 1, 2005; 49(8): 3325 - 3333. [Abstract] [Full Text] [PDF]
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J. Weigelt, K. Itani, D. Stevens, W. Lau, M. Dryden, C. Knirsch, and the Linezolid CSSTI Study Group Linezolid versus Vancomycin in Treatment of Complicated Skin and Soft Tissue Infections Antimicrob. Agents Chemother., June 1, 2005; 49(6): 2260 - 2266. [Abstract] [Full Text] [PDF]
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B. Godin, E. Touitou, E. Rubinstein, A. Athamna, and M. Athamna A new approach for treatment of deep skin infections by an ethosomal antibiotic preparation: an in vivo study J. Antimicrob. Chemother., June 1, 2005; 55(6): 989 - 994. [Abstract] [Full Text] [PDF]
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 O. Petsaris, F. Miszczak, M. Gicquel-Bruneau, A. Perrin-Guyomard, F. Humbert, P. Sanders, and R. Leclercq Combined Antimicrobial Resistance in Enterococcus faecium Isolated from Chickens Appl. Envir. Microbiol., May 1, 2005; 71(5): 2796 - 2799. [Abstract] [Full Text] [PDF]
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C. H. W. Klaassen and J. W. Mouton Molecular Detection of the Macrolide Efflux Gene: To Discriminate or Not To Discriminate between mef(A) and mef(E) Antimicrob. Agents Chemother., April 1, 2005; 49(4): 1271 - 1278. [Full Text] [PDF]
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T. Maisch, C. Bosl, R.-M. Szeimies, N. Lehn, and C. Abels Photodynamic Effects of Novel XF Porphyrin Derivatives on Prokaryotic and Eukaryotic Cells Antimicrob. Agents Chemother., April 1, 2005; 49(4): 1542 - 1552. [Abstract] [Full Text] [PDF]
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G. Lin, K. Credito, L. M. Ednie, and P. C. Appelbaum Antistaphylococcal Activity of Dalbavancin, an Experimental Glycopeptide Antimicrob. Agents Chemother., February 1, 2005; 49(2): 770 - 772. [Abstract] [Full Text] [PDF]
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R. S. Duarte, B. C. Bellei, O. P. Miranda, M. A. V. P. Brito, and L. M. Teixeira Distribution of Antimicrobial Resistance and Virulence-Related Genes among Brazilian Group B Streptococci Recovered from Bovine and Human Sources Antimicrob. Agents Chemother., January 1, 2005; 49(1): 97 - 103. [Abstract] [Full Text] [PDF]
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A. Brenciani, K. K. Ojo, A. Monachetti, S. Menzo, M. C. Roberts, P. E. Varaldo, and E. Giovanetti Distribution and molecular analysis of mef(A)-containing elements in tetracycline-susceptible and -resistant Streptococcus pyogenes clinical isolates with efflux-mediated erythromycin resistance J. Antimicrob. Chemother., December 1, 2004; 54(6): 991 - 998. [Abstract] [Full Text] [PDF]
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K. Credito, G. Lin, L. M. Ednie, and P. C. Appelbaum Antistaphylococcal Activity of LBM415, a New Peptide Deformylase Inhibitor, Compared with Those of Other Agents Antimicrob. Agents Chemother., October 1, 2004; 48(10): 4033 - 4036. [Abstract] [Full Text] [PDF]
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D. B. Hoellman, G. A. Pankuch, and P. C. Appelbaum Antistaphylococcal Activity of CB-181963 (CAB-175), an Experimental Parenteral Cephalosporin Antimicrob. Agents Chemother., October 1, 2004; 48(10): 4037 - 4039. [Abstract] [Full Text] [PDF]
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K. K. Ojo, C. Ulep, N. Van Kirk, H. Luis, M. Bernardo, J. Leitao, and M. C. Roberts The mef(A) Gene Predominates among Seven Macrolide Resistance Genes Identified in Gram-Negative Strains Representing 13 Genera, Isolated from Healthy Portuguese Children Antimicrob. Agents Chemother., September 1, 2004; 48(9): 3451 - 3456. [Abstract] [Full Text] [PDF]
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P. Cerda Zolezzi, L. M. Laplana, C. R. Calvo, P. G. Cepero, M. C. Erazo, and R. Gomez-Lus Molecular Basis of Resistance to Macrolides and Other Antibiotics in Commensal Viridans Group Streptococci and Gemella spp. and Transfer of Resistance Genes to Streptococcus pneumoniae Antimicrob. Agents Chemother., September 1, 2004; 48(9): 3462 - 3467. [Abstract] [Full Text] [PDF]
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A. Villedieu, M. L. Diaz-Torres, A. P. Roberts, N. Hunt, R. McNab, D. A. Spratt, M. Wilson, and P. Mullany Genetic Basis of Erythromycin Resistance in Oral Bacteria Antimicrob. Agents Chemother., June 1, 2004; 48(6): 2298 - 2301. [Abstract] [Full Text] [PDF]
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 P. Tang, P. Ng, M. Lum, M. Skulnick, G. W. Small, D. E. Low, A. Sarabia, T. Mazzulli, K. Wong, A. E. Simor, et al. Use of the Vitek-1 and Vitek-2 Systems for Detection of Constitutive and Inducible Macrolide Resistance in Group B Streptococci J. Clin. Microbiol., May 1, 2004; 42(5): 2282 - 2284. [Abstract] [Full Text] [PDF]
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B. H. Jost, H. T. Trinh, J. G. Songer, and S. J. Billington A Second Tylosin Resistance Determinant, Erm B, in Arcanobacterium pyogenes Antimicrob. Agents Chemother., March 1, 2004; 48(3): 721 - 727. [Abstract] [Full Text] [PDF]
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S. Cousin Jr., W. L. H. Whittington, and M. C. Roberts Acquired Macrolide Resistance Genes in Pathogenic Neisseria spp. Isolated between 1940 and 1987 Antimicrob. Agents Chemother., December 1, 2003; 47(12): 3877 - 3880. [Abstract] [Full Text] [PDF]
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P. C. Y. Woo, A. P. C. To, H. Tse, S. K. P. Lau, and K.-y. Yuen Clinical and Molecular Epidemiology of Erythromycin-Resistant Beta-Hemolytic Lancefield Group G Streptococci Causing Bacteremia J. Clin. Microbiol., November 1, 2003; 41(11): 5188 - 5191. [Abstract] [Full Text] [PDF]
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E. Giovanetti, A. Brenciani, R. Lupidi, M. C. Roberts, and P. E. Varaldo Presence of the tet(O) Gene in Erythromycin- and Tetracycline-Resistant Strains of Streptococcus pyogenes and Linkage with either the mef(A) or the erm(A) Gene Antimicrob. Agents Chemother., September 1, 2003; 47(9): 2844 - 2849. [Abstract] [Full Text] [PDF]
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D. B. Hoellman, G. Lin, L. M. Ednie, A. Rattan, M. R. Jacobs, and P. C. Appelbaum Antipneumococcal and Antistaphylococcal Activities of Ranbezolid (RBX 7644), a New Oxazolidinone, Compared to Those of Other Agents Antimicrob. Agents Chemother., March 1, 2003; 47(3): 1148 - 1150. [Abstract] [Full Text] [PDF]
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P. C. Braga and D. Ricci Differences in the susceptibility of Streptococcus pyogenes to rokitamycin and erythromycin A revealed by morphostructural atomic force microscopy J. Antimicrob. Chemother., October 1, 2002; 50(4): 457 - 460. [Abstract] [Full Text] [PDF]
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V. A. Luna, M. Heiken, K. Judge, C. Ulep, N. Van Kirk, H. Luis, M. Bernardo, J. Leitao, and M. C. Roberts Distribution of mef(A) in Gram-Positive Bacteria from Healthy Portuguese Children Antimicrob. Agents Chemother., August 1, 2002; 46(8): 2513 - 2517. [Abstract] [Full Text] [PDF]
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 W. Liebl, W. E. Kloos, and W. Ludwig Plasmid-borne macrolide resistance in Micrococcus luteus Microbiology, August 1, 2002; 148(8): 2479 - 2487. [Abstract] [Full Text] [PDF]
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J.-A. Lim, A.-R. Kwon, S.-K. Kim, Y. Chong, K. Lee, and E.-C. Choi Prevalence of resistance to macrolide, lincosamide and streptogramin antibiotics in Gram-positive cocci isolated in a Korean hospital J. Antimicrob. Chemother., March 1, 2002; 49(3): 489 - 495. [Abstract] [Full Text] [PDF]
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M. Del Grosso, F. Iannelli, C. Messina, M. Santagati, N. Petrosillo, S. Stefani, G. Pozzi, and A. Pantosti Macrolide Efflux Genes mef(A) and mef(E) Are Carried by Different Genetic Elements in Streptococcus pneumoniae J. Clin. Microbiol., March 1, 2002; 40(3): 774 - 778. [Abstract] [Full Text] [PDF]
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J. C. S. de Azavedo, M. McGavin, C. Duncan, D. E. Low, and A. McGeer Prevalence and Mechanisms of Macrolide Resistance in Invasive and Noninvasive Group B Streptococcus Isolates from Ontario, Canada Antimicrob. Agents Chemother., December 1, 2001; 45(12): 3504 - 3508. [Abstract] [Full Text] [PDF]
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 A. C. Fluit, M. R. Visser, and F.-J. Schmitz Molecular Detection of Antimicrobial Resistance Clin. Microbiol. Rev., October 1, 2001; 14(4): 836 - 871. [Abstract] [Full Text] [PDF]
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B. Aracil, M. Minambres, J. Oteo, C. Torres, J. L. Gomez-Garces, and J. I. Alos High prevalence of erythromycin-resistant and clindamycin-susceptible (M phenotype) viridans group streptococci from pharyngeal samples: a reservoir of mef genes in commensal bacteria J. Antimicrob. Chemother., October 1, 2001; 48(4): 592 - 594. [Full Text] [PDF]
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E. Perez-Trallero, D. Vicente, M. Montes, J. M. Marimon, and L. Pineiro High proportion of pharyngeal carriers of commensal streptococci resistant to erythromycin in Spanish adults J. Antimicrob. Chemother., August 1, 2001; 48(2): 225 - 229. [Abstract] [Full Text] [PDF]
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S. J. Rehm, D. R. Graham, L. Srinath, P. Prokocimer, M.-P. Richard, and G. H. Talbot Successful administration of quinupristin/dalfopristin in the outpatient setting J. Antimicrob. Chemother., May 1, 2001; 47(5): 639 - 645. [Abstract] [Full Text] [PDF]
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I. Rodriguez-Avial, C. Rodriguez-Avial, E. Culebras, A. Benitez, and J. J. Picazo Distribution of mef(A) and erm(B) genes in macrolide-resistant blood isolates of viridans group streptococci J. Antimicrob. Chemother., May 1, 2001; 47(5): 727 - 728. [Full Text] [PDF]
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L. McGee, K. P. Klugman, A. Wasas, T. Capper, A. Brink, and The Antibiotics Surveillance Forum Of South Africa Serotype 19F Multiresistant Pneumococcal Clone Harboring Two Erythromycin Resistance Determinants [erm(B) and mef(A)] in South Africa Antimicrob. Agents Chemother., May 1, 2001; 45(5): 1595 - 1598. [Abstract] [Full Text]
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C. J. Henwood, D. M. Livermore, A. P. Johnson, D. James, M. Warner, A. Gardiner, and The Linezolid Study Group Susceptibility of Gram-positive cocci from 25 UK hospitals to antimicrobial agents including linezolid J. Antimicrob. Chemother., December 1, 2000; 46(6): 931 - 940. [Abstract] [Full Text] [PDF]
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A. Tait-Kamradt, T. Davies, P. C. Appelbaum, F. Depardieu, P. Courvalin, J. Petitpas, L. Wondrack, A. Walker, M. R. Jacobs, and J. Sutcliffe Two New Mechanisms of Macrolide Resistance in Clinical Strains of Streptococcus pneumoniae from Eastern Europe and North America Antimicrob. Agents Chemother., December 1, 2000; 44(12): 3395 - 3401. [Abstract] [Full Text]
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D. L. Stevens, L. G. Smith, J. B. Bruss, M. A. McConnell-Martin, S. E. Duvall, W. M. Todd, and B. Hafkin Randomized Comparison of Linezolid (PNU-100766) versus Oxacillin-Dicloxacillin for Treatment of Complicated Skin and Soft Tissue Infections Antimicrob. Agents Chemother., December 1, 2000; 44(12): 3408 - 3413. [Abstract] [Full Text]
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V. A. Luna, S. Cousin Jr., W. L. H. Whittington, and M. C. Roberts Identification of the Conjugative mef Gene in Clinical Acinetobacter junii and Neisseria gonorrhoeae Isolates Antimicrob. Agents Chemother., September 1, 2000; 44(9): 2503 - 2506. [Abstract] [Full Text]
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M. Santagati, F. Iannelli, M. R. Oggioni, S. Stefani, and G. Pozzi Characterization of a Genetic Element Carrying the Macrolide Efflux Gene mef(A) in Streptococcus pneumoniae Antimicrob. Agents Chemother., September 1, 2000; 44(9): 2585 - 2587. [Abstract] [Full Text]
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A. Portillo, F. Ruiz-Larrea, M. Zarazaga, A. Alonso, J. L. Martinez, and C. Torres Macrolide Resistance Genes in Enterococcus spp. Antimicrob. Agents Chemother., April 1, 2000; 44(4): 967 - 971. [Abstract] [Full Text]
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V. A. Luna, D. B. Jernigan, A. Tice, J. D. Kellner, and M. C. Roberts A Novel Multiresistant Streptococcus pneumoniae Serogroup 19 Clone from Washington State Identified by Pulsed-Field Gel Electrophoresis and Restriction Fragment Length Patterns J. Clin. Microbiol., April 1, 2000; 38(4): 1575 - 1580. [Abstract] [Full Text]
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M. C. Roberts, J. Sutcliffe, P. Courvalin, L. B. Jensen, J. Rood, and H. Seppala Nomenclature for Macrolide and Macrolide-Lincosamide-Streptogramin B Resistance Determinants Antimicrob. Agents Chemother., December 1, 1999; 43(12): 2823 - 2830. [Full Text]
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