Aerobic and anaerobic growth modes and expression of type 1 fimbriae in Salmonella

Food-Associated Stress Primes Foodborne Pathogens for the Gastrointestinal Phase of Infection

The incidence of foodborne outbreaks and product recalls is on the rise. The ability of the pathogen to adapt and survive under stressful environments of food processing and the host gastrointestinal tract may contribute to increasing foodborne illnesses. In the host, multiple factors such as bacteriolytic enzymes, acidic pH, bile, resident microflora, antimicrobial peptides, and innate and adaptive immune responses are essential in eliminating pathogens. Likewise, food processing and preservation techniques are employed to eliminate or reduce human pathogens load in food. However, sub-lethal processing or preservation treatments may evoke bacterial coping mechanisms that alter gene expression, specifically and broadly, resulting in resistance to the bactericidal insults. Furthermore, environmentally cued changes in gene expression can lead to changes in bacterial adhesion, colonization, invasion, and toxin production that contribute to pathogen virulence. The shared microenvironment between the food preservation techniques and the host gastrointestinal tract drives microbes to adapt to the stressful environment, resulting in enhanced virulence and infectivity during a foodborne illness episode.

Development of microbiological field methodology for water and food-chain hygiene analysis of Campylobacter spp. and Yersinia spp. in Burkina Faso, West Africa

Field-adaptable research methods for identifying Campylobacter sp., Yersinia sp. and other pathogenic and indicator bacteria were designed in Finland and tested in Burkina Faso. Several bacterial groups were also validated from artificially contaminated samples. Campylobacter strains were cultivated using an innovative gas generation system: The 'Portable Microbe Enrichment Unit' (PMEU) which provides microaerobic gas flow into the enrichment broth. This enhanced cultivation system produced rapid growth of several isolates of campylobacteria from water and chicken samples. The latter were obtained from local marketplace samples. No yersinias were found in the field studies, whereas they were readily recovered from the spiked samples, as well as Salmonella sp. and Escherichia coli strains. The PMEU method turned out to be reliable for monitoring of water and food hygiene in remote locations.

Composition and antimicrobial activity of the skin peptidome of Russian brown frog Rana temporaria

A nano-HPLC-ESI-OrbiTrap study involving HCD and ETD spectra has been carried out to clarify the composition of the skin peptidome of brown Russian frogs Rana temporaria. This approach allowed determinantion of 76 individual peptides, increasing 3-fold the identified portion of the peptidome in comparison to that obtained earlier with FTICR MS. A search for the new bradykinin related peptides (BRPs) was carried out by reconstructing mass chromatograms based on the ion current of characteristic b- and y-ions. Several peptides were reported in the secretion of R. temporaria for the first time. The overall antibacterial activity of the skin secretion in general and of one individual peptide (Brevinin 1Tb) was determined using PMEU Spectrion (Portable Microbe Enrichment Unit) technology. The inhibitory effects of these peptides on Staphylococcus aureus and Salmonella enterica Serovar typhimutium were equal in scale to that reported for some antibiotics.

Gaseous CO2 signal initiates growth of butyric-acid-producing Clostridium butyricum in both pure culture and mixed cultures with Lactobacillus brevis

Microbial strains produce numerous volatile substances in the anaerobic conditions of the human intestines. The availability of CO(2) is known to be a prerequisite for bacterial growth in general. In experiments with anaerobic Lactobacillus brevis and Clostridium butyricum bacteria in the Portable Microbial Enrichment Unit (PMEU) it was shown that these strains interact; this interaction being mediated by CO(2) emission. CO(2) promoted clostridial growth in pure cultures and mixed cultures with lactobacilli. The growth of C. butyricum in pure cultures was much delayed or did not start at all without CO(2) from outside. Conversely, the onset of growth was provoked by a short (15 min) CO(2) burst. In mixed cultures the presence of lactobacilli in equal numbers speeded up the onset of clostridial growth by 10 h. If C. butyricum cultures designated as PMEU 1, 2, and 3 in cultivation syringes were chained by connecting the gas flow thereby allowing the volatiles of the preceding syringe culture to bubble to the next one, the growth started in 20, 10, or 6 h, respectively. This effect of gaseous emissions from other cultures speeding up the bacterial growth initiation was abolished if the gas was passed through sodium hydroxide to remove the CO(2). The positive contribution of lactobacilli to the growth of butyric-acid-producing clostridia documented in this simulation experiment with PMEU has in vivo implications and indicates molecular communication between the species. CO(2) is a necessary signal for the growth of clostridia, and lactobacilli can promote clostridial growth in mixed cultures where both bacteria grow well with mutual benefit.

Lactic Acid bacteria enriched from human gastric biopsies

The purpose of this paper was to check if viable bacteria, in particular lactic acid bacteria (LAB), could be enriched from biopsies obtained from healthy gastroscopy patients. Gastric biopsies were obtained from 13 gastroscopy patients and subjected to an anaerobic or microaerophilic enrichment procedure utilizing the Portable Microbe Enrichment Unit (PMEU). Profuse microbial growth was observed in most cases. Samples plated on MRS showed high numbers of LAB. The most common species characterized were Lactobacillus reuteri, Lact. salivarius, and Streptococcus salivarius. The results demonstrate a continuous presence of viable LAB in healthy stomach. The species are similar to those traditionally used in food applications. The gastric LAB strains could have a potential in developing probiotic foods aimed specially on the upper part of the gastrointestinal tract.

Enterobacterial microflora in infancy - a case study with enhanced enrichment

OBJECTIVE

To validate PMEU (Portable Microbe Enrichment Unit) method for monitoring the composition and development of infantile intestinal enterobacterial microflora.

METHODS

A case study of a boy with neonatal sepsis is presented. During the first 32 months, he was given 19 systemic antibiotic treatments representing seven different antibiotic classes. Seven fecal samples collected at ages from 3.4 to 31.6 months were studied for enterobacterial strains by a combination of enhanced enrichment culture in the PMEU and plate culture. The identification and phenotypic characterization of the isolates was performed by biochemical tests.

RESULTS

37/51 (73%) of the enterobacterial isolates were detected only after the PMEU enrichment. In most samples Escherichia coli strains were predominating, but also several Enterobacter, Klebsiella, Pantoea and Proteus strains could be isolated. It seemed that the antibiotic medications remarkably delayed the development of the intestinal microflora, because first enterobacterial strains were detected only after 6 months of age.

CONCLUSIONS

The enrichment step turned out to essentially improve the characterization and monitoring of the intestinal enterobacterial microbiota of infants. Compared to plate culture the amount of isolates was 2.6-fold by the PMEU enrichment. This study gives an idea on the development and succession of microbial communities in the gastrointestinal tract and on the variation of the strains due to the intestinal environmental factors.

Enhanced enrichment and detection of thermotolerant Campylobacter species from water using the Portable Microbe Enrichment Unit and real-time PCR

An enhanced enrichment using the Portable Microbe Enrichment Unit (PMEU) with the microaerobic bubbling of broths was applied for the detection of thermotolerant Campylobacter species from water. This PMEU enrichment was compared with the conventional static enrichment of the international standard ISO 17995:2005. In addition, Campylobacter detection after enrichment using a real-time PCR detection was compared with colony counts. The tests with stressed Campylobacter jejuni cells in drinking water indicated that the PMEU enrichment yielded a significantly higher number of Campylobacter cells in the Bolton broth compared with the conventional static incubation. Application of the real-time PCR technique shortened the Campylobacter detection time. This combination of method modifications can be used for Campylobacter detection from water and adds methodological repertoire for the rapid survey and management of waterborne outbreaks.

Growth and gaseous emissions of pure and mixed small intestinal bacterial cultures: Effects of bile and vancomycin

Simultaneous cultivations in anaerobiosis, aerobiosis and with microaerobic gas mixture were used to clarify the bile (oxgall) effects on the pure and mixed cultures of enterobacterial strains in simulations in Portable Microbe Enrichment Unit (PMEU) linked with ChemPro100i((R)) gas detector. The effects of vancomycin were evaluated in aerobic cultures. Growth and metabolic activity of cultures were also followed by measuring sugar consumption, pH alterations, and colony counts on BD CHROMagar Orientation plates. Results showed that the two fermentatively different strains of facultative anaerobes, Escherichia coli E 17 and Klebsiella mobilis ATCC 13048 grew in balance regardless of oxygen level, bile acid concentration or other components of the mixed cultures, Bacillus cereus or Staphylococcus aureus. When the evaporations of the mixed cultures of E. coli, K. mobilis and S. aureus were compared with the emissions of the corresponding pure cultures by ChemPro100i((R)) gas sensing detector, the pure cultures of bile resistant E. coli and K. mobilis produced more gaseous components than the mixed culture indicating that these organisms cooperate and use the substrate more effectively together than separately. A survey of the aseptic bacterial isolations from the bile tract in a big University Hospital, (Salzburg, Austria) during 3 years, showed that these bacterial groups dominated. Only 13.24% of the 287 patient samples were sterile, and around 180 strains of both E. coli and Klebsiella/Enterobacter groups were found amongst 973 isolates from 249 patients (together 35.57%). Enterococcus sp. accounted for 246 isolates being the largest group of strains (24.25% of all the isolates). In anaerobiosis it was shown that Klebsiella neutralized the acids produced in the mixed acid fermentation of the E. coli. The ethanol produced from both groups evaporated in the gas stream of the PMEU culturing step and its formation also removes excess acidity from the cultures. The synergistic behaviour and symbiotic function between E. coli and Klebsiella/Enterobacter strains is suggested.

Transcriptional and translational analysis of biofilm determinants of Aggregatibacter actinomycetemcomitans in response to environmental perturbation

Fimbriae, lipopolysaccharide (LPS), and extracellular polymeric substance (EPS) all contribute to biofilm formation by the periodontopathogen Aggregatibacter actinomycetemcomitans. To understand how individual biofilm determinants respond to changing environmental conditions, the transcription of genes responsible for fimbria, LPS, and EPS production, as well as the translation of these components, was determined in rough (Rv) and isogenic smooth (Sv) variants of A. actinomycetemcomitans cultured in half-strength and full-strength culture medium under anaerobic or aerobic conditions, and in iron-supplemented and iron-chelated medium. The transcription of tadV (fimbrial assembly), pgaC (extracellular polysaccharide synthesis), and orf8 or rmlB (lipopolysaccharide synthesis) was measured by real-time PCR. The amounts of fimbriae, LPS, and EPS were also estimated from stained sodium dodecyl sulfate-polyacrylamide gels and verified by Western blotting and enzyme-linked immunoadsorbent assay using specific antibodies. Each gene was significantly upregulated in the Rv compared to in the Sv. The transcription of fimbrial, LPS, and EPS genes in the Rv was increased approximately twofold in cells cultured in full-strength medium under anaerobic conditions compared to that in cells cultured under aerobic conditions. Under anaerobic conditions, the transcription of fimbrial and EPS enzymes was elevated in both Rv and Sv cells cultured in half-strength medium, compared to that in full-strength medium. Iron chelation also increased the transcription and translation of all biofilm determinants compared to their expression with iron supplementation, yet the quantity of biofilm was not significantly changed by any environmental perturbation except iron limitation. Thus, anaerobic conditions, nutrient stress, and iron limitation each upregulate known biofilm determinants of A. actinomycetemcomitans to contribute to biofilm formation.