Degradative strains of fast-growing Mycobacterium spp. are commonly isolated from polycyclic aromatic hydrocarbon (PAH)-contaminated soils. Little is known, however, about the ecology and diversity of indigenous populations of these fast-growing mycobacteria in contaminated environments. In the present study 16S rRNA genes were PCR amplified using Mycobacterium-specific primers and separated by temperature gradient gel electrophoresis (TGGE), and prominent bands were sequenced to compare the indigenous Mycobacterium community structures in four pairs of soil samples taken from heavily contaminated and less contaminated areas at four different sites. Overall, TGGE profiles obtained from heavily contaminated soils were less diverse than those from less contaminated soils. This decrease in diversity may be due to toxicity, since significantly fewer Mycobacterium phylotypes were detected in soils determined to be toxic by the Microtox assay than in nontoxic soils. Sequencing and phylogenetic analysis of prominent TGGE bands indicated that novel strains dominated the soil Mycobacterium community. Mineralization studies using [ 14 C]pyrene added to four petroleum-contaminated soils, with and without the addition of the known pyrene degrader Mycobacterium sp. strain RJGII-135, indicated that inoculation increased the level of degradation in three of the four soils. Mineralization results obtained from a sterilized soil inoculated with strain RJGII-135 suggested that competition with indigenous microorganisms may be a significant factor affecting biodegradation of PAHs. Pyrene-amended soils, with and without inoculation with strain RJGII-135, experienced both increases and decreases in the population sizes of the inoculated strain and indigenous Mycobacterium populations during incubation.Polycyclic aromatic hydrocarbons (PAHs) consist of a class of chemicals with two or more fused benzene rings in linear, angular, or cluster arrangements. PAHs are ubiquitous: they are produced during fossil fuel combustion, waste incineration, or as by-products of industrial processes, such as coal gasification and petroleum refining, and are often released in large quantities into the environment (28, 29). High-molecularweight PAHs are important constituents of petroleum as they are recalcitrant pollutants and because several of them are known mutagens or carcinogens. For example, the four-ring pyrene is mutagenic, whereas the five-ring benzo[a]pyrene is both mutagenic and carcinogenic (7).There has been growing interest in mycobacteria due to their potential for PAH degradation. Recently described mycobacteria, such as Mycobacterium sp. strains RJGII-135 (hereafter called strain 135) and PYR-1, were isolated from petroleumcontaminated soils and shown to be degraders of high-molecular weight-PAHs such as pyrene and benzo[a]pyrene (15,20,45). Most of the described PAH-degrading mycobacteria are fast-growing species within the genus (4,11,16,17,18,21,22,23,27,30,31,34), a clade distinct from the slow-growing group, which contains most o...

Aims:  To compare the BAX system, the Tecra UniqueTM Salmonella test, and a conventional culture method for the detection of Salmonella in various foods. Methods and Results:  Ready‐to‐eat and raw foods were inoculated with Salmonella serotype Typhimurium, Salmonella serotype Enteritidis, Salmonella serotype Typhi, or Salmonella serotype Derby. Incubated pre‐enrichment cultures were examined using the BAX system, the Tecra UniqueTM Salmonella test, and a conventional culture method. Salmonella could be detected in all ready‐to‐eat food samples inoculated with S. Typhimurium, S. Enteritidis, or S. Derby, with any of the three test methods. However, false negatives were obtained with the Tecra test and the culture method when samples with higher background flora were inoculated with S. Typhi. Sensitivity test results suggested the two rapid tests performed as well as the culture method in the detection of 101 CFU of S. Typhimurium in 25‐g cooked or raw food. Conclusions:  The BAX system and the Tecra UniqueTM Salmonella test demonstrated results comparable with those of the culture method in the detection of Salmonella serotypes used except S. Typhi. Significance and Impact of the Study:  This is the first evaluation of the BAX system, the Tecra UniqueTM Salmonella test, and a culture method in the detection of Salmonella in a variety of western and oriental foods.

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Aims: To evaluate the LightCycler Salmonella Detection Kit and the TaqMan Ò Salmonella Gold Detection and Quantitation Kit for the real-time PCR detection of Salmonella in various food samples. Methods and Results: Ready-to-eat foods and raw food samples were artificially contaminated with Salmonella serotypes. In the specificity test, bacterial DNA extracted from sample pre-enrichment culture was analysed with the detection kits performed respectively on the LightCycler Instrument or the ABI Prism 7000 Sequence Detection System. No false-positive or false-negative results were obtained, although the LightCycler system generated invalid PCR results on two occasions. In the sensitivity test using the LightCycler system, Salmonella could be detected in pre-enrichment cultures of 25-g samples inoculated with as low as 1AE5 · 10 3 CFU (depending on food type), and false-negative results were obtained for samples with low inoculum levels. Conclusions: Two commercial kits for real-time PCR detection of Salmonella were evaluated. Significance and Impact of the Study: Evaluation using more food types and matrices, and foods that contain low number of Salmonella or high number of other competing bacteria, is needed before adopting the real-time PCR technique for routine food tests.