Epidemiological aspects of healthcare-associated infections and microbial genomics.

Hospital-acquired infections (HAIs) are a cause of continuously increasing morbidity and mortality. Most of these infections are caused by a limited set of bacterial species, which share the capability to efficiently spread from patient to patient and to easily acquire antibiotic resistance determinants. This renders correct and rapid species identification and antibiotic susceptibility testing (AST) important and underscores the relevance of bacterial epidemiological typing. The latter is needed for the sensitive detection and exact tracing of nosocomial spread of these potentially multidrug-resistant microorganisms (MDRO). Many microbial typing technologies have been developed and put to some level of executive practice, but it seems that the continued evolution in methodology has currently reached an apex: there is likely to be scientific and practical consensus on the ultimate typing potential of bacterial whole-genome sequencing (WGS). The possibility to perform pan-genomic nucleotide-to-nucleotide comparisons between strains belonging to a single species and to detect even minute changes in nucleotide order will identify closely related organisms, while upon accumulation of such mutations, independent descend can be assumed. Calibration of difference levels [i.e. number of single nucleotide polymorphisms (SNPs)] into categories of inter-strain relatedness needs to be performed in order to generate robust, portable typing schemes. Here, we will briefly discuss the state of affairs regarding bacterial epidemiology based upon WGS, its relatedness with the nomenclature of former typing approaches and the continuing need for a global typing language.

Identification of bacterial species by untargeted NMR spectroscopy of the exo-metabolome.

Identification of bacterial species is a crucial bottleneck for clinical diagnosis of infectious diseases. Quick and reliable identification is a key factor to provide suitable antibiotherapies and avoid the development of multiple-drug resistance. We propose a novel nuclear magnetic resonance (NMR)-based metabolomics strategy for rapid discrimination and identification of several bacterial species that relies on untargeted metabolic profiling of supernatants from bacterial culture media. We show that six bacterial species (Gram negative: Escherichia coli, Pseudomonas aeruginosa, Proteus mirabilis; Gram positive: Enterococcus faecalis, Staphylococcus aureus, and Staphylococcus saprophyticus) can be well discriminated from multivariate statistical analysis, opening new prospects for NMR applications to microbial clinical diagnosis.

A Novel Solid Medium for Culturing Mycobacterium tuberculosis Isolates from Clinical Specimens.

The laboratory diagnosis of tuberculosis usually relies on culture-based isolation of the causative Mycobacterium tuberculosis bacteria. We developed and evaluated the performance of MOD9, a new blood-free derivative of the MOD4 solid medium on which we previously reported for the isolation and culture of mycobacteria. First, inoculation of Lowenstein-Jensen medium with 21 M. tuberculosis isolates at 10(5), 10(3), and 10 CFU yielded colonies in 5.7 ± 1.5 days, 7.6 ± 0.8 days, and 10.8 ± 1.7 days versus 1.5 ± 0.4 days, 3.5 ± 0.6 days, and 4.9 ± 1 days in MOD9 (P < 0.05, Student's t test). Further, the time to detectable growth of M. tuberculosis was measured on MOD9 and Lowenstein-Jensen media after duplicate inoculation of 250 clinical specimens decontaminated with 0.7% chlorhexidine. The contamination rate was 1.6% (4/250) on MOD9 versus 4.4% (11/250) on Lowenstein-Jensen medium (P = 0.11, Fisher's exact test). Chlorhexidine-MOD9 yielded 38/250 (15.2%) isolates versus 32/250 (12.8%) isolates for the chlorhexidine-LJ (P = 0.5195, Fisher's exact test). All together, eight M. tuberculosis isolates were cultured solely from chlorhexidine-MOD9, and two M. tuberculosis isolates were cultured solely from chlorhexidine-LJ. The time to detection was 9.8 ± 3.9 (range, 5 to 18) days for chlorhexidine-MOD9 versus 17.4 ± 5.9 (range, 10 to 35) days for chlorhexidine-LJ (P < 0.05, Student's t test). These data indicate the superiority of the MOD9 medium over the standard LJ medium following chlorhexidine decontamination for the recovery of M. tuberculosis.

Rapid detection of carbapenemase activity: benefits and weaknesses of MALDI-TOF MS.

Matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry (MS) has been introduced as an identification procedure for bacteria and fungi. The MALDI-TOF MS-based analysis of resistance to ß-lactam antibiotics has been applied to detect hydrolysis of carbapenems by different bacterial strains. However, the detection of enzymatic carbapenem degradation by MALDI-TOF MS lacks well-standardized protocols and several methods and models of interpretation using different calculations of ratio-of-peak intensities have been described in the literature. Here, we used faropenem and ertapenem hydrolysis as model compounds. In an attempt to propose a universal protocol, the hydrolysis was regularly monitored during 24 h using well-characterized bacterial strains producing different types of carbapenemases (KPC, IMP, NDM, VIM, and OXA-48). Variable responses and different timing for detectable hydrolysis, depending on the enzyme produced, were observed. KPC degrades its template antibiotics very quickly (15 min for some KPC producers) compared to other types of enzymes (more than 90 min for other enzymes). Prior bacterial lysis was shown to be of no interest in the modulation or optimization of the hydrolytic kinetics. The adequate detection of carbapenem hydrolysis would, therefore, require several MALDI-TOF MS readouts for the timely detection of rapid hydrolysis without missing slow hydrolysis. This enzymatic constraint limits the implementation of a standard protocol in routine microbiology laboratories.

A metagenomics method for the quantitative detection of bacterial pathogens causing hospital-associated and ventilator-associated pneumonia.

IMPORTANCE: The management of ventilator-associated pneumonia and hospital-acquired pneumonia requires rapid and accurate quantitative detection of the infecting pathogen. To this end, we propose a metagenomic sequencing assay that includes the use of an internal sample processing control for the quantitative detection of 20 relevant bacterial species from bronchoalveolar lavage samples.

Dietary fibre degradation and fermentation by two xylanolytic bacteria Bacteroides xylanisolvens XB1A and Roseburia intestinalis XB6B4 from the human intestine.

AIMS: To characterize fibre degradation, colonization and fermentation, and xylanase activity of two xylanolytic bacteria Bacteroides xylanisolvens XB1A(T) and Roseburia intestinalis XB6B4 from the human colon. METHODS AND RESULTS: The bacteria grew well on all the substrates chosen to represent dietary fibres: wheat and corn bran, pea, cabbage and leek fibres, and also on purified xylans. Roseburia intestinalis colonized the substrates more efficiently than Bact. xylanisolvens. For the two bacteria, 80-99% of the total xylanase activity was associated with the cells whatever the substrate and time of growth. Optimal specific activities of cells were obtained on oat spelt xylan; they were higher than those previously measured for xylanolytic bacteria from the human gut. Roseburia intestinalis produced high molecular mass xylanases (100-70 kDa), while Bact. xylanisolvens produced lower molecular mass enzymes, including a cell-associated xylanase of 37 kDa. CONCLUSIONS: The two bacteria display very high xylanolytic activity on the different substrates. Differences were observed on substrate attachment and enzyme systems, suggesting that the two species occupy different niches within the gut microbiota. SIGNIFICANCE AND IMPACT OF THE STUDY: This study characterizes xylan degradation by two major species of the human intestine.

Vitamin E in cranes: reference ranges and nutrient interactions.

Fat soluble vitamins E and A (quantified as alpha-tocopherol and all-trans retinol, respectively) were measured in plasma samples from 274 captive cranes from four institutions and five free-ranging birds. Ages ranged from 4 mo to 80 yr, and all 15 crane species were represented. Captive cranes had a mean +/- standard error (SE) of 6.57 +/- 0.82 micrograms/ml alpha-tocopherol; migrating greater sandhill cranes (Grus canadenis tabida) had a plasma concentration of 3.71 +/- 0.22 micrograms/ml. Sex and age differences were not significant, but crane species that evolved in temperate habitats had higher circulating levels of alpha-tocopherol than tropical or subtropical species. Mean +/- SE retinol values were 0.69 +/- 0.05 micrograms/ml in captive cranes, and 0.66 +/- 0.08 micrograms/ml in free-ranging cranes; values did not differ significantly by sex, age, or species. Dietary vitamin E concentrations were significantly correlated with plasma alpha-tocopherol levels in a logarithmic relationship. Dietary selenium at 0.5 mg/kg was associated with decreased circulating alpha-tocopherol concentrations.

Micropollutants in urban stormwater: occurrence, concentrations, and atmospheric contributions for a wide range of contaminants in three French catchments.

This study aimed at: (a) providing information on the occurrence and concentration ranges in urban stormwater for a wide array of pollutants (n = 77); (b) assessing whether despite the differences between various catchments (land use, climatic conditions, etc.), the trends in terms of contamination level are similar; and (c) analyzing the contribution of total atmospheric fallout (TAF) with respect to sources endogenous to this contamination. The studied contaminants include conventional stormwater contaminants (polycyclic aromatic hydrocarbons (PAHs), Zn, Cu, Pb, etc.), in addition to poorly or undocumented pollutants such as nonylphenol and octylphenol ethoxylates (NPnEO and OPnEO), bisphenol A (BPA), polybrominated diphenyl ethers (PBDEs), a wide variety of pesticides, and various metals of relevance (As, Ti, Sr, V). Sampling and analysis were performed using homogeneous methods on three urban catchments with different land use patterns located in three distinct French towns. For many of these pollutants, the results do not allow highlighting a significant difference in stormwater quality at the scale of the three urban catchments considered. Significant differences were, however, observed for several metals (As, Cr, Cu, Ni, Sr and Zn), PAHs, and PBDEs, though this assessment would need to be confirmed by further experiments. The pollutant distributions between dissolved and particulate phases were found to be similar across the three experimental sites, thus suggesting no site dependence. Lastly, the contributions of TAF to stormwater contamination for micropollutants were quite low. This finding held true not only for PAHs, as previously demonstrated in the literature, but also for a broader range of molecules such as BPA, NPnEO, OPnEO, and PBDEs, whose high local production is correlated with the leaching of urban surfaces, buildings, and vehicles.