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- Taha, Muhamed-Kheir, et al.
(författare)
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Defining the breakpoint for resistance to rifampicin in Neisseria meningitidis by rpoB sequencing
- 2009
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Clinical isolates of Neisseria meningitidis resistant to rifampicin are important to identify asthey lead to failure of chemoprophylaxis of meningococcal disease. However, theidentification of these isolates is hindered by the absence of a harmonized breakpoint despiteefforts of standardization. In the present study, a large number (n=352) of clinical N.meningitidis isolates from 12 mainly European countries and spanning over 25 years (1984 to2009) were examined. The collection comprised all clinical isolates with MIC 0.25 mg/lreceived by the national reference laboratories for meningococci in the participating countries(n=161). In addition, representative isolates displaying MIC of rifampicin <0.25 mg/l wereexamined (n=191). Phenotyping and genotyping of isolates were performed and a 660 bpDNA fragment of the rpoB gene was sequenced in all the included isolates. Sequencesdiffering by at least one nucleotide were defined as a unique rpoB allele (n=55). Geometricmeans of MIC were calculated for isolates displaying the same allele. All the clinical isolatesdisplaying MIC >1 mg/l of rifampicin possessed rpoB alleles with critical mutations (in total21 alleles), resulting in substitutions at the codon H552 and less frequently at nearby codons(S548 and S557). These alterations were absent in the alleles (n=34) found in all isolates withMIC 1 mg/l. Based on these findings, rifampicin susceptible isolates could be defined asthose with MIC 1 mg/l. A new web site was created based on the data from this work (http://neisseria.org/nm/typing/rpoB). The rifampicin resistant isolates belonged to diversegenetic lineages and provoked lower bacteremia levels in mice. This biological cost mayexplain the non-expansion of the rifampicin resistant isolates.
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- Vaneechoutte, Mario, et al.
(författare)
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Description of Acinetobacter venetianus ex Di Cello et al. 1997 sp nov.
- 2009
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Ingår i: International Journal of Systematic and Evolutionary Microbiology. - : Microbiology Society. - 1466-5026 .- 1466-5034. ; 59, s. 1376-1381
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Tidskriftsartikel (refereegranskat)abstract
- The name 'Acinetobacter venetianus' has been used previously to designate three marine hydrocarbon-degrading Acinetobacter strains, of which strain RAG-1 (=ATCC 31012) has industrial applications for the production of the bioemulsifier emulsan. However, to date, the name of this taxon has not been validly published. In this study, five strains were examined to corroborate the delineation of this taxon by means of phenotypic characterization, DNA-DNA hybridization, selective restriction fragment amplification (AFLP), amplified rDNA restriction analysis (ARDRA), rpoB gene sequence analysis and tRNA intergenic spacer length polymorphism analysis (tDNA-PCR) and to emend the description of 'Acinetobacter venetianus' (ex Di Cello et al. 1997). AFLP analysis showed that the five strains formed a tight cluster at 56.8 +/- 5.0% genomic relatedness that was separated from strains of other haemolytic species of the genus Acinetobacter and from the type and reference strains of other Acinetobacter species at <= 27% relatedness, indicating the distinctiveness of the novel strains. The strains were haemolytic and able to grow on citrate (Simmons), L-histidine and malonate. The strains did not oxidize D-glucose or utilize DL-lactate or L-aspartate. The G + C contents of strains RAG-1 and of VE-C3 were 43.9% and 43.6 mol%, respectively. The novel strains could be recognized by a characteristic ARDRA pattern (Cfol 1, Alul 3, Mbol 2, Rsal 2, Mspl 3). The consensus tDNA-PCR pattern for the five strains consisted of amplified fragments of 87.9, 100.2, 134.6 and 248.5 bp and was indistinguishable from that of strains of Acinetobacter genomic species 14BJ. The five strains represent a novel species for which the name Acinetobacter venetianus sp. nov. is proposed. The type strain is RAG-1(T) (=ATCC 31012(T)=CCUG 45561(T)=LMG 19082(T)=LUH 3904(T)=NIPH 1925(T)).
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