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ABSTRACT: Seventy-four unrelated clinical isolates of Streptococcus pneumoniae harboring the tet(M) gene were studied. Seven strains with low tetracycline (Tc) MICs (0.25 to 0.5 μg/ml) were found to harbor truncated tet(M) alleles that were inactivated by different frameshift mutations. In contrast, five strains bore deletions in the tet(M) promoter region, among which four displayed increased Tc MICs (16 to 64 μg/ml). The same promoter mutations were detected in Tc-resistant mutants selected in vitro from various susceptible strains. Sequence analysis revealed that these deletions might impede the formation of the transcriptional attenuator located immediately upstream of tet(M). Expression in Enterococcus faecalis of a tet(M) reporter gene transcribed from these promoter mutants conferred a level of Tc resistance similar to that observed in the parental S. pneumoniae strains. These results show that different levels of Tc susceptibility found in clinical isolates of S. pneumoniae can be explained by frameshift mutations within tet(M) and by alterations of the upstream transcriptional attenuator.
Antimicrobial Agents and Chemotherapy 07/2012; 56(10):5040-5. · 4.84 Impact Factor
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ABSTRACT: The Sirscan2000automatic MIC determination (SIR-MD) system is a new system for MIC determination based on the automatic detection of growth of bacteria spotted onto agar medium using a camera scan. To evaluate its accuracy, 3608 Streptococcus pneumoniae clinical isolates yielding 18,165 MICs were tested in parallel with the SIR-MD and a standard interpretive antibiogram procedure. The overall percent agreement between the 2 methods within 1 log(2) dilution was 86.9%. After exclusion of the 11.8% noninterpretable results, errors in the deduction of susceptibilities were very major in 0.03%, major in 0.2%, and minor in 1.3%.
Diagnostic microbiology and infectious disease 07/2011; 70(3):399-403. · 2.45 Impact Factor
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ABSTRACT: With respect to pneumococci, there is a need to detect first-step mutants with reduced fluoroquinolone (FQ) susceptibility from which second-step, resistant mutants are likely to be selected in the presence of antipneumococcal FQs. Here, we describe an interpretative disk diffusion test, of which three options are presented, that allows the distinction between first- and second-step mutants. Using five FQ disks (pefloxacin, norfloxacin, levofloxacin, ciprofloxacin, and sparfloxacin, option 1), all known mechanisms of altered FQ susceptibility found in first-step mutants (ParC, ParE, GyrA, or efflux) and in second-step mutants (ParC and GyrA or ParE and GyrA) can be accurately detected, making this option a useful epidemiological tool. Using three FQ disks (pefloxacin, norfloxacin, and levofloxacin, option 2), the most prevalent FQ-resistant mutants, but not the first-step GyrA mutants, can be detected. With only two FQ disks (norfloxacin and levofloxacin) in the third and simplest option, first-step mutants can be distinguished from second-step mutants, however, without differentiation of ParC, ParE, or efflux alterations.
Antimicrobial Agents and Chemotherapy 03/2006; 50(2):572-9. · 4.84 Impact Factor
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Thierry Garnier,
Karin Eiglmeier,
Jean-Christophe Camus,
Nadine Medina,
Huma Mansoor,
Melinda Pryor,
Stephanie Duthoy, Sophie Grondin,
Celine Lacroix,
Christel Monsempe, [......],
Rebecca Atkin,
Jon Doggett,
Rebecca Mayes,
Lisa Keating,
Paul R Wheeler,
Julian Parkhill,
Bart G Barrell,
Stewart T Cole,
Stephen V Gordon,
R Glyn Hewinson
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ABSTRACT: Mycobacterium bovis is the causative agent of tuberculosis in a range of animal species and man, with worldwide annual losses to agriculture of $3 billion. The human burden of tuberculosis caused by the bovine tubercle bacillus is still largely unknown. M. bovis was also the progenitor for the M. bovis bacillus Calmette-Guérin vaccine strain, the most widely used human vaccine. Here we describe the 4,345,492-bp genome sequence of M. bovis AF2122/97 and its comparison with the genomes of Mycobacterium tuberculosis and Mycobacterium leprae. Strikingly, the genome sequence of M. bovis is >99.95% identical to that of M. tuberculosis, but deletion of genetic information has led to a reduced genome size. Comparison with M. leprae reveals a number of common gene losses, suggesting the removal of functional redundancy. Cell wall components and secreted proteins show the greatest variation, indicating their potential role in host-bacillus interactions or immune evasion. Furthermore, there are no genes unique to M. bovis, implying that differential gene expression may be the key to the host tropisms of human and bovine bacilli. The genome sequence therefore offers major insight on the evolution, host preference, and pathobiology of M. bovis.
Proceedings of the National Academy of Sciences 06/2003; 100(13):7877-82. · 9.68 Impact Factor
