Journal of Rapid Methods and Automation in Microbiology最新文献

Abstract Petrifilm™ Kit-HEC (3M Company, St. Paul, MN) was used to monitor the growth of Escherichia coli O157:H7 in ground beef co-inoculated with microorganisms of the background flora, including nonpathogenic E.coli, Pseudomonas putida or Leuconostoc sp. The growth was monitored in beef samples stored at room temperature and under refrigeration. A cultural procedure using sorbitol MacConkey agar was used for comparison. The correlation between counts of E.coli O157:H7 using these procedures was high: 99.1% for samples kept at room temperature and 94.9% for those kept under refrigeration.

Abstract Nine cultures were examined for growth at 37C in media with different levels of PCB and selected one culture to treat an industrial liquid waste containing high levels of PCB 1248. All the nine cultures grew well in the presence of 100 to 500 μg PCB 1254 mL⁻¹ glucose basal salt broth (GBSB) as well as in tryptic soy broth (TSP) with no significant changes in generation time. The cultures grew well in basal salt agar containing PCB as sole source of carbon. Pseudomonas aeruginosa and Serratia liquefaciens strains survived for 75 to 120 min in the presence of 300 to 2000 μg PCB 1254 mL⁻¹ sodium-phosphate buffer (SPB) pH 7.0. The P. aeruginosa cells removed both PCB 1254 and ¹⁴C-PCB from SPB and GBSB within 48 h and the percent uptakes were 26 and 39.7%, respectively. The results of the fate and distribution of PCB 1254, including ¹⁴C-PCB, in cells of P. aeruginosa, S. liquefaciens, and two Bacillus strains grown in PCB-media showed that more than 50% of the ¹⁴C-PCB were in the alcohol and in alcohol-ether soluble fractions (mostly lipids). This was also confirmed after rupturing the P. aeruginosa cells using French pressure and/or lysozyme and fractionation. Both the intrinsic flora and P. aeruginosa strain were used in a bioreactor system for the treatments of 27 and 33 gallons industrial liquid waste containing 150 and/or 800 mg PCB 12481 1⁻¹, respectively, and complete oxidation was achieved, within approximately 150 days and the biological half-life of the PCB was 30 and 15 days, respectively.

Abstract Human foods and animal feeds vary in their amino acid availability based upon the nature of the protein source and subsequent processing treatments to which the source may have been subjected during manufacture. In this study, growth and recovery of an Escherichia coli lysine auxotroph assay organism was tested in the presence of an antibiotic and antifungal supplemented medium previously developed. Overall growth rate comparisons in amended liquid minimal media showed that addition of antistatic agents did not alter the growth rate of the indicator strain and that it is independent of lysine concentration. Six different animal feeds were studied to determine the potential background contribution of indigenous feed Escherichia coli and whether the selective medium would suppress these organisms. Recovery of the indicator strain used for the rapid bacterial lysine assay was above 94% in all feed suspensions. In addition to this, indigenous microflora of the animal feeds was unable to grow in the presence of the antistatic agents selected. Microbial growth measured as agar plate colonies from short (1 week) and long term storage (6 months) feeds were completely suppressed on the antibiotic supplemented plates after 24 h of incubation. This result confirms that the amendments will suppress the growth of indigenous feed E. coli populations during the time frame typically used to conduct the rapid bacterial lysine assay with the E. coli lysine auxotroph without altering the growth rate response of the auxotroph.

Abstract The rapid identification and quantification of pathogenic foodborne bacteria is a national research priority. Data collected with a new spectrochemical method suggests that resonance Raman spectroscopy can rapidly and selectively identify and quantify bacteria in foods and other complex biomatrices. This method utilizes hydrogen-deuterium exchange (HDE) to resolve the spectral fingerprints of individual components in the overlapped regions of the ultraviolet resonance Raman spectra of heterogeneous samples. We illustrate this concept with HDE-induced changes in the spectra of bacteria and beef carcass wash samples. The data presented here suggest that the combination of ultraviolet resonance Raman spectroscopy and HDE can potentially establish the identities and quantities of bacteria in heterogeneous samples within seconds to minutes.

Abstract Bacterial reduction of trimethylamine N-oxide (TMAO) cannot be reliably determined try qualitative methods, which are unusable because of problems relating to incubation time, the indicator and the equilibrium of the redox potential. This makes it difficult to reproduce results. These problems have been observed with various semi-agar media used in the evaluation of TMAO reduction. We propose a new and rapid method of quantitative evaluation by means of assay of trimethylamine (TMA) in a new TMA-free culture medium. This methodology has been used to evaluate the TMAO-reducing capacity of different endogenous and exogenous bacterial strains found in fish flesh (Aeromonas hydrophila, Alteromonas communis, Escherichia coli, Flavobacterium branchiophilum, Micrococcus sedentarius, Proteus mirabilis, Pseudomonas fluorescens, Pseudomonas nautica, Serratia marcescens, Shewanella putrefaciens, Vibrio parahaemolyticus). Unlike the qualitative methods, our method showed that all tested strains were able to reduce TMAO. Fish spoilage bacteria can form TMA under anaerobic conditions, as shown by tests using bacterial suspensions from fish (Helicolenus dactylopterus, Merlangus merlangus, Clupea harengus). Such tests can be used to assess fish spoilage.

Abstract A rapid screening method was developed to presumptively identify S. typhimurium DT 104 in naturally contaminated poultry barn environmental samples. This technique involves a semiselective preenrichment (chloramphenicol in buffered peptone water) procedure followed by screening with a Salmonella-specific chemiluminescence-based detection system (IsoSCREEN™, Stratecon Diagnostics International, USA), then plating on Modified Semi-solid Rappaport-Vassilliadis (MSRV) agar plates incorporating antibiotic disks (ampicillin, chloramphenicol and tetracycline). Environmental samples (183 total) from a poultry barn were analyzed for the suspected presence of Salmonella typhimurium DT 104. Of these, 141 samples were identified as containing Salmonella species, 9 of which were identified as Salmonella typhimurium DT 104 by both the standard culture methods and the combined IsoSCREEN™-MSRV antibiotic susceptibility test (IsoSCREEN™-MAST). In comparison with the standard culture and antibiotic susceptibility testing techniques, which require 7–9 days to complete, the IsoSCREEN™-MAST required only 3–5 days to presumptively identify Salmonella typhimurium DT 104 in the samples.