Nonfermenting bacteria are ubiquitous environmental opportunists that cause infections in humans, especially compromised patients. Due to their limited biochemical reactivity and different morphotypes, misidentification by classical phenotypic means occurs frequently. Therefore, we evaluated the use of matrix-assisted laser desorption ionization-time-of-flight mass spectrometry (MALDI-TOF MS) for species identification. By using 248 nonfermenting culture collection strains composed of 37 genera most relevant to human infections, a reference database was established for MALDI-TOF MS-based species identification according to the manufacturer's recommendations for microflex measurement and MALDI BioTyper software (Bruker Daltonik GmbH, Leipzig, Germany), i.e., by using a mass range of 2,000 to 20,000 Da and a new pattern-matching algorithm. To evaluate the database, 80 blind-coded clinical nonfermenting bacterial strains were analyzed. As a reference method for species designation, partial 16S rRNA gene sequencing was applied. By 16S rRNA gene sequencing, 57 of the 80 isolates produced a unique species identification (>99% sequence similarity); 11 further isolates gave ambiguous results at this threshold and were rated as identified to the genus level only. Ten isolates were identified to the genus level (>97% similarity); and two isolates had similarity values below this threshold, were counted as not identified, and were excluded from further analysis. MALDI-TOF MS identified 67 of the 78 isolates (85.9%) included, in agreement with the results of the reference method; 9 were misidentified and 2 were unidentified. The identities of 10 randomly selected strains were 100% correct when three different mass spectrometers and four different cultivation media were used. Thus, MALDI-TOF MS-based species identification of nonfermenting bacteria provided accurate and reproducible results within 10 min without any substantial costs for consumables.

The higher plant Arabidopsis thaliana (Arabidopsis) is an important model for identifying plant genes and determining their function. To assist biological investigations and to define chromosome structure, a coordinated effort to sequence the Arabidopsis genome was initiated in late 1996. Here we report one of the first milestones of this project, the sequence of chromosome 4. Analysis of 17.38 megabases of unique sequence, representing about 17% of the genome, reveals 3,744 protein coding genes, 81 transfer RNAs and numerous repeat elements. Heterochromatic regions surrounding the putative centromere, which has not yet been completely sequenced, are characterized by an increased frequency of a variety of repeats, new repeats, reduced recombination, lowered gene density and lowered gene expression. Roughly 60% of the predicted protein-coding genes have been functionally characterized on the basis of their homology to known genes. Many genes encode predicted proteins that are homologous to human and Caenorhabditis elegans proteins.

Current methods for identification of Mycobacterium spp. rely upon time-consuming phenotypic tests, mycolic acid analysis, and narrow-spectrum nucleic acid probes. Newer approaches include PCR and sequencing technologies. We evaluated the MicroSeq 500 16S ribosomal DNA (rDNA) bacterial sequencing kit (Applied Biosystems, Foster City, Calif.) for its ability to identify Mycobacterium isolates. The kit is based on PCR and sequencing of the first 500 bp of the bacterial rRNA gene. One hundred nineteen mycobacterial isolates (94 clinical isolates and 25 reference strains) were identified using traditional phenotypic methods and the MicroSeq system in conjunction with separate databases. The sequencing system gave 87% (104 of 119) concordant results when compared with traditional phenotypic methods. An independent laboratory using a separate database analyzed the sequences of the 15 discordant samples and confirmed the results. The use of 16S rDNA sequencing technology for identification of Mycobacterium spp. provides more rapid and more accurate characterization than do phenotypic methods. The MicroSeq 500 system simplifies the sequencing process but, in its present form, requires use of additional databases such as the Ribosomal Differentiation of Medical Microorganisms (RIDOM) to precisely identify subtypes of type strains and species not currently in the MicroSeq library.

Six methods of extracting Mycobacterium tuberculosis DNA from sputum for testing by quantitative PCR were compared: Tris-EDTA (TE) buffer, PrepMan Ultra, 2% sodium dodecyl sulfate (SDS)-10% Triton X with and without sonication, Infectio Diagnostics, Inc. (IDI) lysing tubes, and QIAGEN QIAamp DNA mini kit; all included a 15-min boiling step. Pooled digested and decontaminated sputum was spiked with M. tuberculosis ATCC 27294. Each extraction method was repeated eight times. Quantitative PCR was performed on the Smart Cycler and Rotor-Gene 3000 using primers targeting an 83-bp fragment of IS6110. An minor grove binding Eclipse probe with a fluorescent label was used for detection. An internal control was included to detect amplification inhibition. The limit of detection of M. tuberculosis DNA was 0.5 fg with both instruments. Calculated DNA concentrations (picograms) extracted using IDI, PrepMan, QIAGEN, and TE were 42.8, 30.4, 28.2, and 7.4, respectively, when run on the Smart Cycler, and 51.7, 20.1, 14.9, and 8.6, respectively, when run on Rotor-Gene. All extractions using SDS/Triton X with or without sonication were inhibited. Of the extraction methods evaluated, IDI lysis tubes provided the greatest yield of mycobacterial DNA, and the procedure can be completed in less than 1 h versus 2.5؊3 h for the QIAGEN extraction.Tuberculosis is a public health problem worldwide, and for optimal control, early diagnosis is necessary (4, 6, 7). Several researchers have developed real-time PCR assays that provide rapid detection of various target sequences of Mycobacterium tuberculosis complex (MTBC) and drug resistance genes in patient specimens (1,3,5,(16)(17)(18)(19). The ability of these assays to detect MTBC in clinical samples is dependent on both the target sequence selected and the efficiency of the DNA extraction procedure. Several methods of mycobacterial cell wall lysis and DNA extraction have been evaluated, including detergents, proteolytic enzymes, mechanical disruption, and temperature changes alone and in various combinations (1, 2, 5, 8-15, 17, 20). The objective of this study was to compare six methods of extracting M. tuberculosis DNA from respiratory specimens: Tris-EDTA (TE) boil extraction (10), PrepMan ultra extraction (Applied Biosystems, Inc., Foster City, CA), Infectio Diagnostics, Inc. (IDI) lysis extraction (Infectio Diagnostics, Inc. Quebec, Canada), QIAGEN QIAmp DNA mini kit (QIAGEN, Inc., Valencia, CA), sodium dodecyl sulfate (SDS)-Triton X extraction (9), and SDS-Triton X plus sonication. The effectiveness of each extraction method was assessed using two quantitative real-time PCR assays.Sample preparation. Digested and decontaminated (Nacetyl-cysteine-2% NaOH) sputum specimens that were culture negative for mycobacteria were pooled for use as the standard respiratory specimen. A suspension of M. tuberculosis ATCC 27294 was prepared in sterile saline and adjusted to the density of a 1.0 McFarland standard. The suspension was diluted 1:10 in saline and used to spike the pooled respiratory sp...

Identification of clinically significant nocardiae to the species level is important in patient diagnosis and treatment. A study was performed to evaluate Nocardia species identification obtained by partial 16S ribosomal DNA (rDNA) sequencing by the MicroSeq 500 system with an expanded database. The expanded portion of the database was developed from partial 5 16S rDNA sequences derived from 28 reference strains (from the American Type Culture Collection and the Japanese Collection of Microorganisms). The expanded MicroSeq 500 system was compared to (i) conventional identification obtained from a combination of growth characteristics with biochemical and drug susceptibility tests; (ii) molecular techniques involving restriction enzyme analysis (REA) of portions of the 16S rRNA and 65-kDa heat shock protein genes; and (iii) when necessary, sequencing of a 999-bp fragment of the 16S rRNA gene. An unknown isolate was identified as a particular species if the sequence obtained by partial 16S rDNA sequencing by the expanded MicroSeq 500 system was 99.0% similar to that of the reference strain. Ninety-four nocardiae representing 10 separate species were isolated from patient specimens and examined by using the three different methods. Sequencing of partial 16S rDNA by the expanded MicroSeq 500 system resulted in only 72% agreement with conventional methods for species identification and 90% agreement with the alternative molecular methods. Molecular methods for identification of Nocardia species provide more accurate and rapid results than the conventional methods using biochemical and susceptibility testing. With an expanded database, the MicroSeq 500 system for partial 16S rDNA was able to correctly identify the human pathogens N. brasiliensis, N. cyriacigeorgica, N. farcinica, N. nova, N. otitidiscaviarum, and N. veterana.

Several Mycobacterium-like organisms related to the Mycobacterium terrae complex have been isolated from clinical samples. In the clinical microbiology laboratory, partial 16S rRNA gene sequencing (approximately the first 500 bp) rather than full 16S rRNA gene sequencing is often used to identify Mycobacterium species. Partial 16S rRNA gene sequence analysis revealed 100 % similarity between 65 clinical isolates and Mycobacterium sp. MCRO 6 (GenBank accession no. X93032). Even after sequencing the nearly full-length 16S rRNA gene, closest similarity was only 99?6 % to Mycobacterium nonchromogenicum ATCC 19530 T . Sequencing of the nearly full-length 16S rRNA gene, the 16S-23S internal transcribed spacer region and the hsp65 gene did not reveal genotypic identity with the type strains of M. nonchromogenicum, M. terrae or Mycobacterium triviale. Although sequence analysis suggested that these clinical isolates represented a novel species, mycolic acid analysis by HPLC failed to distinguish them from M. nonchromogenicum. Therefore, phenotypic analysis including growth characterization, antibiotic susceptibility testing and biochemical testing was performed. These strains from clinical samples should be recognized as representing a novel species of the genus Mycobacterium, for which the name Mycobacterium arupense sp. nov. is proposed. The type strain is AR30097 T (=ATCC BAA-1242 T =DSM 44942 T ).At the time of writing, the genus Mycobacterium comprises 119 species with validly published names, at least 30 of which have been described within the last 5 years (http:// www.bacterio.cict.fr/m/mycobacterium.html). Despite this rapid increase in the number of newly recognized Mycobacterium species, many additional Mycobacterium species remain to be formally described (Pauls et al., 2003;Tortoli, 2003;Turenne et al., 2004). Many of these unnamed species have been isolated from clinical specimens and need to be correctly characterized for appropriate patient management.In the clinical microbiology laboratory, phenotypic and biochemical testing may not identify Mycobacterium species accurately, as the results of these tests may be identical between different species or may vary depending on the growth conditions employed. Sequencing the 16S rRNA gene of Mycobacterium species has improved the speed and accuracy of identification (Cloud et al., 2002;Turenne et al., 2001;Patel et al., 2000). Sequencing additional targets such as the hsp65 gene and the 16S-23S internal transcribed spacer region 1 (ITS1) has increased our ability to describe novel Mycobacterium species (Turenne et al., 2004;Tortoli, 2003;Ringuet et al., 1999; Mohamed et al., 2005).The purpose of this study was to describe a Mycobacteriumlike organism that appears to be a genotypic match to Abbreviations: FL-HPLC, fluorescence detection HPLC; ITS1, internal transcribed spacer region 1; NTM, non-tuberculous mycobacteria.

Meningitis remains a worldwide problem, and rapid diagnosis is essential to optimize survival. We evaluated the utility of a multiplex PCR test in differentiating possible etiologies of meningitis. Cerebrospinal fluid (CSF) from 69 HIV-infected Ugandan adults with meningitis was collected at diagnosis (n=51) and among persons with cryptococcal meningitis during therapeutic lumbar punctures (n=68). Cryopreserved CSF specimens were analyzed with BioFire FilmArray® Meningitis/Encephalitis panel, which targets 17 pathogens. The panel detected Cryptococcus in the CSF of patients diagnosed with a first-episode of cryptococcal meningitis by fungal culture with 100% sensitivity and specificity, and differentiated between fungal relapse and paradoxical immune reconstitution inflammatory syndrome in recurrent episodes. A negative FilmArray result was predictive of CSF sterility on follow-up lumbar punctures for cryptococcal meningitis. EBV was frequently detected in this immunosuppressed population (n=45). Other pathogens detected included: CMV (n=2), VZV (n=2), HHV-6 (n=1), and Streptococcus pneumoniae (n=1). The FilmArray Meningitis/Encephalitis panel offers a promising platform for rapid meningitis diagnosis.

Legionella spp. are a common cause of community-acquired respiratory tract infections and an occasional cause of nosocomial pneumonia. A PCR method for the detection of legionellae in respiratory samples was evaluated and was compared to culture. The procedure can be performed in 6 to 8 h with a commercially available DNA extraction kit (Qiagen, Valencia, Calif.) and by PCR with gel detection. PCR is performed with primers previously determined to amplify a 386-bp product within the 16S rRNA gene of Legionella pneumophila. We can specifically detect the clinically significant Legionella species including L. pneumophila, L. micdadei, L. longbeachae, L. bozemanii, L. feeleii, and L. dumoffii. The assay detects 10 fg (approximately two organisms) of legionella DNA in each PCR. Of 212 clinical specimens examined by culture, 100% of the culture-positive samples (31 of 31) were positive by this assay. By gel detection of amplification products, 12 of 181 culture-negative samples were positive forLegionella species by PCR, resulting in 93% specificity. Four of the 12 samples with discrepant results (culture negative, PCR positive) were confirmed to be positive for Legionellaspecies by sequencing of the amplicons. The legionella-specific PCR assay that is described demonstrates high sensitivity and high specificity for routine detection of legionellae in respiratory samples.