A Laboratory Method for Determining Bacterially Formed Odorants and Reducing Odor in Absorbent Incontinence Products.

PURPOSE: The purpose of this study was to design a laboratory test method to mimic the formation of bacterially formed odorants during the use of absorbent urinary incontinence products. Three odor inhibitors with different modes of action were tested and evaluated. METHODS: Bacterially formed odorants in incontinence products were evaluated by adding a synthetic urine inoculated with a mixture of 4 bacterial strains to product samples cut from the incontinence products. The product samples were incubated in sealed flasks. The odorants that formed in the head space were sampled onto adsorbent tubes and analyzed by gas chromatography. The inhibitory effects of low pH, ethylenediaminetetraacetic acid (EDTA), and activated carbon were then measured. RESULTS: This technique enabled production of known odorants 3-methylbutanal, guaiacol, diacetyl, and dimethyl disulfide (DMDS) in concentrations of 50 to 600 ng/L in incontinence products. The method was further evaluated by testing 3 types of odor inhibitors; EDTA significantly reduced formation of all 4 odorants (P < .001). Lowering the pH from 6.0 to 4.9 decreased levels of 3-methylbutanal, DMDS, and guaiacol (P < .001); however, diacetyl levels increased (P < .001). Activated carbon significantly reduced the formation of diacetyl, DMDS, guaiacol, and 3-methylbutanal (P < .001). CONCLUSIONS: The technique we developed can be used to evaluate inhibitors with different modes of action to determine odor control in incontinence products. The odorants formed are produced by bacteria and have been identified as key contributors to the odor of used incontinence products. This work can be a step toward establishing a standard in the field of incontinence and odor control; creation of a standard will help the health care sector compare products to be purchased and benefit patients through the development of better products.

The early response to acid shock in Lactobacillus reuteri involves the ClpL chaperone and a putative cell wall-altering esterase.

To be able to function as a probiotic, bacteria have to survive the passage through the gastrointestinal tract. We have examined survival and gene expression of Lactobacillus reuteri ATCC 55730 after a sudden shift in environmental acidity to a pH close to the conditions in the human stomach. More than 80% of the L. reuteri cells survived at pH 2.7 for 1 h. A genomewide expression analysis experiment using microarrays displayed 72 differentially expressed genes at this pH. The early response to severe acid shock in L. reuteri differed from long-term acid adaptation to milder acid stress studied in other lactic acid bacteria. The genes induced included the following: clpL, genes putatively involved in alterations of the cell membrane and the cell wall; genes encoding transcriptional regulators; phage genes; and genes of unknown function. Two genes, clpL, encoding an ATPase with chaperone activity, and lr1516, encoding a putative esterase, were selected for mutation analyses. The mutants were significantly more sensitive to acid than the wild type was. Thus, these genes could contribute to the survival of L. reuteri in the gastrointestinal tract.

The cell surface of Lactobacillus reuteri ATCC 55730 highlighted by identification of 126 extracellular proteins from the genome sequence.

Bioinformatical analyses of a draft genome sequence of the commensal bacterium Lactobacillus reuteri ATCC 55730 revealed 126 genes encoding putative extracellular proteins. The function, localization and distribution in bacterial species were predicted. Interestingly, few proteins possessed LPXTG motifs or C-terminal transmembrane anchors. Instead eight proteins were putatively anchored by GW repeats and several secreted proteins were likely to be re-associated to the surface. The majority of the extracellular proteins were widely distributed, i.e., found universally or in gram-positive bacteria, but 24 were only detected in L. reuteri. Further, the number of transporters was lower, while the number of enzyme was higher than in related species.

Phage display reveals 52 novel extracellular and transmembrane proteins from Lactobacillus reuteri DSM 20016(T).

Extracellular and transmembrane proteins are important for the binding of bacteria to intestinal surfaces and for their interaction with the host. The aim of this study was to identify genes encoding extracellular and transmembrane proteins from the probiotic bacterium Lactobacillus reuteri by construction and screening of a phage display library. This library was constructed by insertion of randomly fragmented DNA from L. reuteri into the phagemid vector pG3DSS, which was previously developed for screening for extracellular proteins. After affinity selection of the library, the L. reuteri inserts were sequenced and analysed with bioinformatic tools. The screening resulted in the identification of 52 novel genes encoding extracellular and transmembrane proteins. These proteins were classified as: transport proteins; enzymes; sensor-regulator proteins; proteins involved in host/microbial interactions; conserved hypothetical proteins; and unconserved hypothetical proteins. Further characterization of the extracellular and transmembrane proteins identified should contribute to the understanding of the probiotic properties of L. reuteri.

Escherichia coli lacking the AcrAB multidrug efflux pump also lacks nonproteinaceous, PHB-polyphosphate Ca2+ channels in the membrane.

PHB(polyP) complexes bind calcium and form calcium channels in the cytoplasmic membrane in Escherichia coli and are likely to be important in Ca(2+) homeostasis in this organism. E. coli N43, which lacks the AcrA component of a major multidrug resistance pump, was shown to be defective in calcium handling, with an inability to maintain submicromolar levels of free Ca(2+) in the cytoplasm. Therefore, using an N-phenyl-1-napthylamine (NPN)-dependent fluorescence assay, we measured temperature-dependent phase transitions in the membranes of intact cells. These transitions specifically depend on the presence of PHB(Ca(2+)polyP) complexes. PHB(Ca(2+)polyP) channel complexes, particularly in stationary phase cultures, were detected in wild-type strains; however, in contrast, isogenic acrA(-) strains had greatly reduced amounts of the complexes. This indicates that the AcrAB transporter may have a novel, hitherto undetected physiological role, either directly in the membrane assembly of the PHB complexes or the transport of a component of the membrane, which is essential for assembly of the complexes into the membrane. In other experiments, we showed that the particular defective calcium handling detected in N43 was not due to the absence of AcrA but to other unknown factors in this strain.