Viable Pathogens Research Articles

A FRET-Based Fluorogenic Trehalose Dimycolate Analogue for Probing Mycomembrane-Remodeling Enzymes of Mycobacteria.

The mycobacterial outer membrane, or mycomembrane, is essential for the viability and virulence of Mycobacterium tuberculosis and related pathogens. The mycomembrane is a dynamic structure, whose chemical composition and biophysical properties can change during stress to give an advantage to the bacterium. However, the mechanisms that govern mycomembrane remodeling and their significance to mycobacterial pathogenesis are still not well characterized. Recent studies have shown that trehalose dimycolate (TDM), a major glycolipid of the mycomembrane, is broken down by the mycobacteria-specific enzyme TDM hydrolase (Tdmh) in response to nutrient deprivation, a process which appears to modulate the mycomembrane to increase nutrient acquisition, but at the expense of stress tolerance. Tdmh activity thus balances the growth of M. tuberculosis during infection in a manner that is contingent upon host immunity. Current methods to probe Tdmh activity are limited, impeding the development of inhibitors and the investigation of the role of Tdmh in bacterial growth and persistence. Here, we describe the synthesis and evaluation of FRET-TDM, which is a fluorescence-quenched analogue of TDM that is designed to fluoresce upon hydrolysis by Tdmh and potentially other trehalose ester-degrading hydrolases involved in mycomembrane remodeling. We found that FRET-TDM was efficiently activated in vitro by recombinant Tdmh, generating a 100-fold increase in fluorescence. FRET-TDM was also efficiently activated in the presence of whole cells of Mycobacterium smegmatis and M. tuberculosis, but the observed signal was predominantly Tdmh-independent, suggesting that physiological levels of Tdmh are low and that other mycobacterial enzymes also hydrolyze the probe. The latter notion was confirmed by employing a native protein gel-based fluorescence assay to profile FRET-TDM-activating enzymes from M. smegmatis lysates. On the other hand, FRET-TDM was capable of detecting the activity of Tdmh in cells when it was overexpressed. Together, our data demonstrate that FRET-TDM is a convenient and sensitive in vitro probe of Tdmh activity, which will be beneficial for Tdmh enzymatic characterization and inhibitor screening. In more complex samples, for example, live cells or cell lysates, FRET-TDM can serve as a tool to probe Tdmh activity at elevated enzyme levels, and it may facilitate the identification and characterization of related hydrolases that are involved in mycomembrane remodeling. Our study also provides insights as to how the structure of FRET-TDM or related fluorogenic probes can be optimized to achieve improved specificity and sensitivity for detecting mycobacteria.

The role of metal ions in the virulence and viability of bacterial pathogens

Metal ions fulfil a plethora of essential roles within bacterial pathogens. In addition to acting as necessary cofactors for cellular proteins, making them indispensable for both protein structure and function, they also fulfil roles in signalling and regulation of virulence. Consequently, the maintenance of cellular metal ion homeostasis is crucial for bacterial viability and pathogenicity. It is therefore unsurprising that components of the immune response target and exploit both the essentiality of metal ions and their potential toxicity toward invading bacteria. This review provides a brief overview of the transition metal ions iron, manganese, copper and zinc during infection. These essential metal ions are discussed in the context of host modulation of bioavailability, bacterial acquisition and efflux, metal-regulated virulence factor expression and the molecular mechanisms that contribute to loss of viability and/or virulence during host-imposed metal stress.

Survival of the Oak Wilt Fungus in Logs Fumigated with Sulfuryl Fluoride and Methyl Bromide

Abstract Methyl bromide (MB) fumigation of oak (Quercus sp.) logs destined for export is required to mitigate risks associated with movement of the oak wilt fungus, Bretziella fagacearum. Alternative fumigants with efficacy against B. fagacearum are needed because of MB's ozone-depleting properties. Fumigation with sulfuryl fluoride (SF) is considered a promising substitute. Logs (1.8 m long) were obtained from Quercus trees (18.3 to 29.2 cm diameter at breast height) that were naturally infested (NI) or artificially inoculated (AI) with B. fagacearum to compare pathogen colonization and survival following fumigation with SF and MB. The logs were fumigated with SF for 72 hours with 240, 280, and 320 g/m3 or 96 hours with 128 and 240 g/m3. MB fumigations were conducted using the current treatment schedule for oak logs destined for export (240 g/m3 for 72 h). Frequencies of successful pathogen isolation before treatment were higher for AI logs than for NI logs based on isolation rates from sapwood chips. Treatments greatly reduced frequencies of viable pathogen presence, but no treatment was successful in eradicating the pathogen. Experiments were conducted on blocks (10.2 by 10.2 by 11.4 cm3) obtained from Quercus trees to investigate simulated penetration and diffusion of SF and MB into oak logs. Slow, variable fumigant diffusion never reached concentration–time products lethal to B. fagacearum. Based on these results, reliance on SF alone as a quarantine measure may require higher concentration × time products to achieve quarantine level control of the oak wilt fungus in logs.

Vacuum Steam Treatment Eradicates Viable Bretziella fagacearum from Logs Cut from Wilted Quercus rubra.

Methyl bromide (MB) fumigation is required for U.S. Quercus log exports due to concern over unintentional spread of Bretziella fagacearum. MB alternatives are needed due to the chemical's ability to damage the earth's ozone layer. Vacuum steam (VS) is an environmentally friendly method that was evaluated for its ability to eradicate B. fagacearum in logs (24 to 61 cm diameter; 1.7 to 1.9 m long) obtained from Q. rubra that had wilted following natural infection (NI) or artificial inoculation (AI). Five replicate loads of two NI and one AI logs were VS-treated at 56°C for 30 min and 60°C for 60 min (at 5.0 cm sapwood depth). Mean frequencies of pretreatment fungus colonization ranged from 12.5 to 24.4% in NI and 29.4 to 45.6% in AI logs based on isolation from wood chips of inner and outer sapwood, respectively, of two disks per log. Frequencies of pathogen DNA detection were similar to those for isolation. No viable pathogen or its DNA were detected in posttreatment logs. Treatment times ranged from 5 to 9 h for the 56°C/30 min schedule and from 8 to 10 h for the 60°C/60 min schedule. Based on these results, VS is worthy of further development as a MB alternative.

Current Progress in the Structural and Biochemical Characterization of Proteins Involved in the Assembly of Lipopolysaccharide.

The lipid component of the outer leaflet of the outer membrane of Gram-negative bacteria is primarily composed of the glycolipid lipopolysaccharide (LPS), which serves to form a protective barrier against hydrophobic toxins and many antibiotics. LPS is comprised of three regions: the lipid A membrane anchor, the nonrepeating core oligosaccharide, and the repeating O-antigen polysaccharide. The lipid A portion is also referred to as endotoxin as its overstimulation of the toll-like receptor 4 during systemic infection precipitates potentially fatal septic shock. Because of the importance of LPS for the viability and virulence of human pathogens, understanding how LPS is synthesized and transported to the outer leaflet of the outer membrane is important for developing novel antibiotics to combat resistant Gram-negative strains. The following review describes the current state of our understanding of the proteins responsible for the synthesis and transport of LPS with an emphasis on the contribution of protein structures to our understanding of their functions. Because the lipid A portion of LPS is relatively well conserved, a detailed description of the biosynthetic enzymes in the Raetz pathway of lipid A synthesis is provided. Conversely, less well-conserved biosynthetic enzymes later in LPS synthesis are described primarily to demonstrate conserved principles of LPS synthesis. Finally, the conserved LPS transport systems are described in detail.

Effect of storage time and temperature on the viability of E. coli O157:H7, Salmonella spp., Listeria innocua, Staphylococcus aureus, and Clostridium sporogenes vegetative cells and spores in vacuum-packed canned pasteurized milk cheese

The effect of storage temperature and time on the viability of several foodborne bacterial pathogens inoculated into vacuum-packed canned pasteurized cow's milk cheese was investigated. Three popular cheese styles namely, a semi-soft white Monterey Jack style cheese, and two Cheddar cheeses vacuum packaged in mason jars were inoculated with a 3-strain cocktail of each of the following microbes at the mean concentrations listed: Escherichia coli O157:H7 (6.6 log CFU/g), Salmonella spp. (6.3 log CFU/g), Listeria innocua (6.4 log CFU/g), Staphylococcus aureus (3.6 log CFU/g), and Clostridium sporogenes vegetative cells (6.3 log CFU/g), and spores (6.0 log CFU/g). The effect of storage temperature (at 4.4, 10, and 21.1 °C) and the time (from 0 to 365 days) on the survival of the inoculated organisms was evaluated at different sampling times (0, 30, 60, 120,180, and 365 days). Both storage temperature and the time had a significant effect on the viability of the test organisms. Increasing the storage temperature from 4.4 to 21.1 °C and the storage time for up to 365 days increased pathogen reduction. The type of cheese also had a significant effect on the viability of the test organisms. At the same sampling times, the viability of E. coli O157:H7 and Salmonella spp., were highest in Monterey Jack-style cheese followed by the Cheddar cheeses one to which annatto had been added (Cheddar 1) and the second, a white Cheddar that has an added adjunct flavor culture (Cheddar 2). Similarly, the type of cheese and the time-temperature conditions to which the cheese was exposed had a significant effect on the viability of L. innocua. Among the tested organisms, S. aureus was most susceptible while C. sporogenes (both vegetative cells and spores) were most resistant. The findings of this challenge study indicate that vacuum packed canned cheese is not a favorable environment for the growth of bacterial pathogens. Depending upon the type of canned cheese, appropriate storage times and temperatures are critical to ensure microbiological safety.

Localized collection of airborne biological hazards for environmental monitoring

The need to detect and identify trace amounts of airborne biological hazards with ever increasing sensitivity and selectivity is the main driver in sensor research. However, the low concentration of airborne hazardous entities requires the concentration of the analyte at the biosensor of choice. Here, we present a robust implementation of an effective “Airborne Analyte Transporter”, which (i) permits time-course sampling of airborne particles, (ii) precise localization and concentration of airborne particles at a designated location of a given biosensor (iii) and allows the biological downstream analysis of viable pathogens. The Airborne Analyte Transporter implements a corona discharge based analyte charging method in combination with an electrodynamic funnel concentration concept. The Airborne Analyte Transporter achieves a 1000-fold increase in particle concentration compared to diffusion and settling based transport and allows the precise and local collection of viable pollen, yeasts, spores, bacteria and virus particles with an additional lateral concentration. Potential biological hazards with concentrations down to 20 ppm can still be analyzed using different microscopy techniques and bacterial cultures. The Airborne Analyte Transporter provides a localized collection of airborne particles on a biosensor of choice to be utilized in monitoring air in the health care sector or in hygiene-sensitive areas.

Seasonal and Regional Distributions, Degree-Day Models, and Phoresy Rates of the Major Sap Beetle (Coleoptera: Nitidulidae) Vectors of the Oak Wilt Fungus, Bretziella fagacearum, in Wisconsin

Oak wilt is a lethal disease caused by the invasive fungus Bretziella fagacearum, which is transmitted belowground via root grafts and aboveground by sap beetles (Nitidulidae). Attempts to limit spread and impact of B. fagacearum emphasize limiting harvesting and pruning to periods of vector inactivity. However, there is limited information on sap beetle activity periods, responses to temperature, and phoresy frequencies of fungi. We sampled two major vectors in Wisconsin, Colopterus truncatus and Carpophilus sayi, for 2 yr to quantify their seasonal and geographic abundances. Trapping was performed in 12 oak stands, and beetles were assayed for B. fagacearum. C. truncatus was captured from March until November, peaking during April and May. C. sayi was captured from April until November, peaking in May and July. Relative abundances (N = 15,980) were 59.3% C. truncatus and 40.7% C. sayi. C. sayi was more abundant in southern Wisconsin, whereas C. truncatus was more evenly distributed. Both species were present at asymptomatic sites. All sites with oak wilt centers yielded beetles with viable fungal propagules, with the frequency of association ranging from 1 to 50%. Sites asymptomatic for oak wilt contained both beetle species, but no vector-borne viable pathogen. Degree-day models were constructed to improve the generality of these results and estimate cumulative emergences across a latitudinal range over the previous 10-yr means and extremes. Because activity by C. truncatus and C. sayi spans the seasonal activities of oak wilt vectors, these results can help guide oak management practices.

A Nanowire-Based Flexible Antibacterial Surface Reduces the Viability of Drug-Resistant Nosocomial Pathogens

The global emergence of antimicrobial resistance poses a serious risk to patients by increasing the cost of healthcare with prolonged stay in hospitals, serious clinical complications, and even death. The ever-increasing challenges in discovering antibacterial agents with novel mechanisms of action necessitates the development of smart antibacterial surfaces that have the potential to minimize colonization of common hospital surfaces with bacterial pathogens. In this work, we report the antibacterial properties of flexible poly(dimethylsiloxane) (PDMS) polymer decorated with copper hydroxide nanowires (PDMS_Cu) against a panel of drug-resistant bacterial pathogens isolated from patients with bloodstream infection. The fabricated PDMS_Cu surface showed superior antimicrobial activity against both Gram negative (Escherichia coli and Klebsiella pneumoniae) and Gram positive (Staphylococcus aureus) bacterial strains as compared to flat PDMS and glass coverslip, which were used as controls. RAW macrophage and ...

Electrodeposition of a magnetic and redox-active chitosan film for capturing and sensing metabolic active bacteria

Rapid and portable detection of viable pathogen is highly desired to minimize the risk of foodborne pathogen outbreaks. Here we report a proof-of-concept fabrication methodology of a multifunctional film that allows established methods from bacterial recognition (antibodies) and nanotechnology (magnetic nanoparticles) to be coupled with electrochemical signal processing methods for detection of viable bacteria. Specifically, we enlist a sequence of externally applied electrical and magnetic signals to: i) guide the self-assembly of stimuli-responsive biopolymer; ii) incorporate magnetic nanoparticles to form a magnetic layer; iii) electro-synthesize a signal processing layer (redox-capacitor). The function of the magnetic layer is collecting and concentrating MMP-bacteria through magnetic attractions between MMP-bacteria and the magnetic layer. The function of the signal processing layer is amplifying electrochemical detection of the collected bacteria by engaging the redox-active mediators with the redox capacitor. Importantly, the fabrication demonstrated here is simple, controllable, and reagentless.

MP10-07 EVALUATION OF BACTERIAL BIOFILMS ON RENAL CALCULI

You have accessJournal of UrologyInfections/Inflammation/Cystic Disease of the Genitourinary Tract: Kidney & Bladder I1 Apr 2018MP10-07 EVALUATION OF BACTERIAL BIOFILMS ON RENAL CALCULI Negar Motayagheni, Sargurunathan Subashchandrabose, Jorge Gutierrez-Aceves, and Majid Mirzazadeh Negar MotayagheniNegar Motayagheni More articles by this author , Sargurunathan SubashchandraboseSargurunathan Subashchandrabose More articles by this author , Jorge Gutierrez-AcevesJorge Gutierrez-Aceves More articles by this author , and Majid MirzazadehMajid Mirzazadeh More articles by this author View All Author Informationhttps://doi.org/10.1016/j.juro.2018.02.353AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookTwitterLinked InEmail INTRODUCTION AND OBJECTIVES Bacterial biofilms are functionally differentiated and organized communities, which have been detected on indwelling devices and in urinary tract infections. The aim of this study is to detect and evaluate bacterial presence and aggregation on uroliths as a potential source of sepsis secondary to stone manipulation. METHODS Urinary stones were collected from patients during PCNL. Samples of uroliths were cultured on LB and MacConkey media under aerobic conditions. Surface bacteria were eliminated with ethanol to delineate the localization of bacteria in renal calculi. Pure cultures of stone-associated bacteria were isolated and species identified with MALDI-TOF mass spectrometry. Stones were dried and coated with gold prior to evaluation by scanning electron microscopy (SEM). Both presence and morphological features of bacterial communities were evaluated. We also reviewed the history of urine cultures and antibiotic therapy within 30 days prior to and during the surgery. RESULTS A total of 23 calculi were obtained from the same number of patients undergoing PCNL. Urine from 8 patients (35%) was culture-positive. Culture of 9 stones (39%) harbored viable Gram-negative bacterial pathogens (Tab 1). Only in one patient (11%), culture of urine and urolith were similar (E. coli). Bacteria were not present in urine of 4 (44%) patients, despite harboring infected calculi. In 7 culture-positive stones (77%), bacterial aggregation was detected by SEM (Fig. 1). The bacterial cells encased in a matrix-like material were suggestive of biofilms. Some stones without biofilm-like structures were colonized by E. coli and P. mirabilis. 4 of the 9 patients (44%) with infected stones were on antibiotics in the month prior to PCNL. Our results do not show correlation between exposure to antibiotics and uroliths infection. CONCLUSIONS Renal calculi colonized with bacteria exhibit morphological features that are reminiscent of bacterial biofilm. Bacteria might be present on the surface or internally within these calculi. There was no correlation between bacterial growth from stone and urine culture. © 2018FiguresReferencesRelatedDetails Volume 199Issue 4SApril 2018Page: e118 Advertisement Copyright & Permissions© 2018MetricsAuthor Information Negar Motayagheni More articles by this author Sargurunathan Subashchandrabose More articles by this author Jorge Gutierrez-Aceves More articles by this author Majid Mirzazadeh More articles by this author Expand All Advertisement Advertisement PDF downloadLoading ...

Is it dead or alive? TLR8 can tell.

The sensing of viable pathogens by the receptor TLR8 on human monocytes provides key signals that initiate the differentiation of naive CD4+ T cells into follicular helper T cells. Targeting TLR8 might represent a novel approach for improving immunity following vaccination.

Use of quantitative real-time PCR to determine viability of Streptococcus equi subspecies equi in respiratory secretions from horses with strangles.

In recent years, molecular approaches have been able to characterise the viability of equine upper respiratory tract pathogens using absolute molecular quantitation as well as detection of transcripts for virulence genes. The objective of this study was to investigate molecular surrogates for S.equi subspecies equi (S.equi) viability in biological samples from horses with strangles. Retrospective cross-sectional study. S.equi culture-positive and culture-negative upper airway secretions were assessed by qPCR at the genomic (gDNA) and complimentary DNA (cDNA) level for various target genes (SeM, SEQ2190, eqbE and szpSe). Absolute quantitation was performed using standard curves, and the results were expressed as number of S.equi target genes per μl of gDNA or cDNA. Additionally, the presence or absence of S.equi gene expression for the various target genes was assessed and compared with the culture results. While all 21 culture-positive samples tested S.equiqPCR positive, up to 43.7 and 18.9% of 64 culture-negative samples tested qPCR positive at the gDNA and cDNA level, respectively. Significant differences in absolute quantitation for S.equi at the gDNA level were found between culture-positive and culture-negative samples. When absolute quantitation of S.equi target genes at the gDNA level was assessed with the presence or absence of transcripts, there was a significantly higher S.equi target gene number in samples with expression of transcripts compared with samples with no expression of transcripts. The lack of standardisation of samples collected in the field and the delay from sample collection to samples processing may have negatively affected the cultivability of S.equi and mRNA quality. Molecular viability for S.equi can be investigated by determining absolute quantitation and/or by detecting mRNA for specific target genes. However, veterinarians have to be cautioned that any qPCR-positive result for S.equi needs to be taken seriously and trigger biosecurity protocols aimed at reducing spread.

Evaluation of the antimicrobial efficacy of neutral electrolyzed water on pork products and the formation of viable but nonculturable (VBNC) pathogens

The goals of this study were to evaluate the antimicrobial efficacy of Neutral electrolyzed oxidizing (NEO) water on E. coli O157:H7, Salmonella Enteritidis and Yersinia enterocolitica in both pure culture and on inoculated pork chops and skin samples, and to investigate the formation of viable but nonculturable (VBNC) pathogens after treatments. Both the plate count method and flow cytometry were used to evaluate antimicrobial efficacy on pure cultures. Different concentrations of NEO water were prepared by diluting the original NEO water (100%) with sterilized deionized water. The antimicrobial efficacy increased as the concentrations of NEO water increased. The flow cytometry results showed that treating with diluted NEO water led to the formation of VBNC cells. No VBNC cells formed when treating pure cultures with 50% or 100% NEO water. Yersinia cultures were found to be more resistant to NEO treatments than Salmonella and E. coli O157:H7 cultures, with Yersinia cultures showing lower reductions and higher levels of VBNC cells after treatments. The antimicrobial efficacy of NEO water was significantly better on skin samples than on pork chops. The differences in protein content and structure between pork chops and skin samples serve as major factors impacting the NEO water's efficacy.

A Genetic Tool to Quantify trans-Translation Activity in Vivo

In bacteria, trans-translation is the main quality control mechanism for rescuing ribosomes arrested during translation. This key process is universally conserved and plays a critical role in the viability and virulence of many pathogens. We developed a reliable in vivo double-fluorescence reporter system for the simultaneous quantification of both trans-translation and the associated proteolysis activities in bacteria. The assay was validated using mutant bacteria lacking tmRNA, SmpB, and the ClpP protease. Both antisense tmRNA-binding RNA and a peptide mimicking the SmpB C-terminal tail proved to be potent inhibitors of trans-translation in vivo. The double-fluorescent reporter was also tested with KKL-35, an oxadiazole derivative that is supposed to be a promising trans-translation inhibitor, and it surprisingly turns out that trans-translation is not the only target of KKL-35 in vivo.

Defining Aerosol Generating Procedures and Pathogen Transmission Risks in Healthcare Settings

BackgroundQuestions remain about the degree to which small particle aerosols are generated during patient care activities and whether such aerosols could transmit viable pathogens to healthcare personnel. This project measured aerosol production during common medical procedures and collected samples for pathogen recovery.MethodsSix procedures were targeted for aerosol sampling: extubation, bronchoscopy, mechanical ventilation, noninvasive ventilation, suctioning (open or tracheostomy), and nebulized medication administration. Any patient undergoing one of these procedures was eligible for sampling, with a preference for patients with a respiratory viral infection. Baseline samples were collected when possible. Four real-time aerosol characterization instruments were used to detect small particle aerosols generated during procedures. SKC Biosamplers, placed at 3 feet and 6 feet from the patient, were used for pathogen recovery. All samples were subjected to bacterial culture; viral PCR, and viral culture were added depending on the patient’s respiratory disease profile.ResultsSamples were collected during extubation (n = 1), bronchoscopy (n = 3), mechanical ventilation (n = 13), noninvasive ventilation (n = 6), suctioning (n = 6), and nebulized medication administration (n = 9). Only nebulized medication administration exhibited differences in particle mass concentration between baseline and procedure aerosol measurements. None of the Biosampler samples were PCR positive for a respiratory virus and none had a positive influenza culture. Five samples had positive bacterial cultures, mainly with common environmental or skin contaminants such as Micrococcus luteus, Staphylococcus pasturei, and Bacillus flexus.ConclusionSignificant small particle aerosol generation was only seen with nebulized medication administration. No viruses were recovered and minimal viable bacteria were recovered. Additional study is needed to confirm these findings and examine aerosol generation during other procedures commonly considered to be aerosol-generating.Disclosures C. A. D. Burnham, bioMerieux: Grant Investigator, Research grant; ThermoFisher: Consultant, Salary; Cepheid: Grant Investigator, Research grant

Selective and concurrent detection of viable Salmonella spp., E. coli, Staphylococcus aureus, E. coli O157:H7, and Shigella spp., in low moisture food products by PMA-mPCR assay with internal amplification control

Salmonella enterica, enterohemorrhagic Escherichia coli, and Staphylococcus aureus are major pathogens contaminating low moisture foods. E. coli and Shigella spp. may acquire significance in future since cross-contamination plays a critical role in outbreaks involving low moisture foods. This study investigated a PMA-IAC-mPCR for rapid, reliable and simultaneous detection of viable Salmonella spp., E. coli, Staphylococcus aureus, E. coli O157:H7, and Shigella spp., in low moisture foods. Propidium monoazide (PMA) was applied to detect only viable cells by eliminating PCR signal from dead cells. In addition, an internal amplification control (IAC) was included in the multiplex PCR as an indicator of false negative results arising due to inhibitors in low moisture foods. The sensitivity of the assay for viable cells with PMA treatment was 102–103 CFU/mL for all the target pathogens reflecting the non-influence of PMA treatment on sensitivity. After 10 h enrichment, the PMA-IAC-mPCR could detect 101 CFU/g of Salmonella spp., E. coli, Staphylococcus aureus, E. coli O157:H7, and Shigella spp., in artificially inoculated low moisture foods (peanut butter, chocolate, milk powder and egg powder). This PMA-IAC-mPCR assay would find its promising application in simultaneous detection of these viable target pathogens in low moisture foods.

Characterization of Aerosols Generated During Patient Care Activities.

Questions remain about the degree to which aerosols are generated during routine patient care activities and whether such aerosols could transmit viable pathogens to healthcare personnel (HCP). The objective of this study was to measure aerosol production during multiple patient care activities and to examine the samples for bacterial pathogens. Five aerosol characterization instruments were used to measure aerosols during 7 patient care activities: patient bathing, changing bed linens, pouring and flushing liquid waste, bronchoscopy, noninvasive ventilation, and nebulized medication administration (NMA). Each procedure was sampled 5 times. An SKC BioSampler was used for pathogen recovery. Bacterial cultures were performed on the sampling solution. Patients on contact precautions for drug-resistant organisms were selected for most activity sampling. Any patient undergoing bronchoscopy was eligible. Of 35 sampling episodes, only 2 procedures showed a significant increase in particle concentrations over baseline: NMA and bronchoscopy with NMA. Bronchoscopy without NMA and noninvasive ventilation did not generate significant aerosols. Of 78 cultures from the impinger samples, 6 of 28 baseline samples (21.4%) and 14 of 50 procedure samples (28.0%) were positive. In this study, significant aerosol generation was only observed during NMA, both alone and during bronchoscopy. Minimal viable bacteria were recovered, mostly common environmental organisms. Although more research is needed, these data suggest that some of the procedures considered to be aerosol-generating may pose little infection risk to HCP.

The impact of the postharvest environment on the viability and virulence of decay fungi

ABSTRACTPostharvest decay of fruits, vegetables, and grains by fungal pathogens causes significant economic losses. Infected produce presents a potential health risk since some decay fungi produce mycotoxins that are hazardous to human health. Infections are the result of the interplay between host resistance and pathogen virulence. Both of these processes, however, are significantly impacted by environmental factors, such as temperature, UV, oxidative stress, and water activity. In the present review, the impact of various physical postharvest treatments (e.g., heat and UV) on the viability and virulence of postharvest pathogens is reviewed and discussed. Oxidative injury, protein impairment, and cell wall degradation have all been proposed as the mechanisms by which these abiotic stresses reduce fungal viability and pathogenicity. The response of decay fungi to pH and the ability of pathogens to modulate the pH of the host environment also affect pathogenicity. The effects of the manipulation of the postharvest environment by ethylene, natural edible coatings, and controlled atmosphere storage on fungal viability are also discussed. Lastly, avenues of future research are proposed.

Non Thermal Pasteurization for Orange Juice Using Pulsed Electric Field

Pasteurization is an act or a process to minimize or eliminate all forms of life, particularly microorganisms in food products. Its aim is to reduce or eliminate the number of viable pathogens, which are likely to cause diseases. Pasteurization can be in the form of thermal and non-thermal methods. Thermal pasteurization typically uses high heat and temperature to reduce or eliminate microorganisms. Although this method has been practiced and proven effective, the process is associated with many side effects. Due to this problem, new approaches using a non-thermal pasteurization to generate pulsed electric field (PEF) is proposed. In this paper, non-thermal sterilization using Cascaded H-Bridge Multilevel Inverter (CHMI) pulse power generator was evaluated in order to produce pulsed electric field in inactivating of microorganisms such as Saccharomyces cerevisiae and Escherichia coli in orange juice. The experimental set-up was conducted where an orange juice was placed inside the treatment chamber. The electrodes between the treatment chamber were applied with pulsed electric field up to 15 kV/cm by using the CHMI. The hardware development was implemented using MOSFET 2K3748 power devices and the gate signal generator was controlled by using dSPACE DS 1104. The experimental results show that, an output voltage of 1.2 kVp−p was effective to inactivate Escherichia coli and Saccharomyces cerevisiae. Thus, power consumption was decreased and energy was saved. The pulsed width of 1000 μs with repetitive rate of 50 Hz was generated from the hardware implementation. The results proved that the specifications of the experimental set-up meet the requirements for liquid food sterilization, particularly to inactivate Escherichia coli and Saccharomyces cerevisiae microorganisms in orange juice by using streaking plate techniques.