Ching-Wen Chang

Exposure of Workers to Airborne Microorganisms in Open-Air Swine Houses

ABSTRACT This study quantified the levels of airborne microorganisms in six swine farms with more than 10,000 pigs in subtropical Taiwan. We evaluated breeding, growing, and finishing stalls, which were primarily open-air buildings, as well as partially enclosed farrowing and nursery piggeries. Airborne culturable bacteria, gram-negative bacteria, and fungi were placed on appropriate media by using an all-glass impinger or single-stage Andersen microbial sampler. Results showed that mean concentrations of culturable bacteria and gram-negative bacteria were 3.3 × 105 and 143.7 CFU/m3, respectively. The concentration of airborne culturable fungi was about 103 CFU/m3, with Cladosporium the predominant genus. The highest airborne levels of culturable bacteria and gram-negative bacteria were identified in the finishing units. The air of the nursery stalls was the least contaminated with culturable and gram-negative bacteria. Irregular and infrequent cleaning, high pig density, no separation of wastes from pen floors, and accumulation of water as a result of the processes for cleaning and reducing pig temperature possibly compromise the benefits of the open characteristic of the finishing units with respect to airborne bacterial concentration.

Using filtrate of waste biosolids to effectively produce bio-hydrogen by anaerobic fermentation.

Waste biosolids collected from sewage works is a biomass containing a vast amount of polysaccharides and proteins, and thus is considered a potential substrate for producing hydrogen using anaerobic fermentation. This work demonstrated, contrary to the common assumption, that the solids phase in waste activated biosolids presents extra nutrients for anaerobes; it in fact prohibits effective bio-hydrogen production. Using filtrate after removal of solids from biosolids produces more hydrogen than using the whole biosolids, with the former reaching a level an order of magnitude higher than the literature results.

Exposure assessment to airborne endotoxin, dust, ammonia, hydrogen sulfide and carbon dioxide in open style swine houses.

Information is limited for the exposure levels of airborne hazardous substances in swine feed buildings that are not completely enclosed. Open-style breeding, growing and finishing swine houses in six farms in subtropical Taiwan were studied for the airborne concentrations of endotoxin, dust, ammonia, hydrogen sulfide and carbon dioxide. The air in the farrowing and nursery stalls as partially enclosed was also simultaneously evaluated. Three selected gases and airborne dusts were quantified respectively by using Drager diffusion tubes and a filter-weighing method. Endotoxin was analyzed by the Limulus amoebocyte lysate assay. Average concentration of airborne total endotoxin among piggeries was between 36.8 and 298 EU/m(3), while that for respirable endotoxin was 14.1-129 EU/m(3). Mean concentration of total dust was between 0.15 and 0.34 mg/m(3), with average level of respirable dust of 0.14 mg/m(3). The respective concentrations of NH3, CO2 and H2S were less than 5 ppm, 600-895 ppm and less than 0.2 ppm. Airborne concentrations of total dust and endotoxin in the nursery house were higher than in the other types of swine houses. The finishing house presented the highest exposure risk to NH3, CO2 and H2S. Employees working in the finishing stalls were also exposed to the highest airborne levels of respirable endotoxin and dust. On the other hand, the air of the breeding units was the least contaminated in terms of airborne endotoxin, dust, NH3, CO2 and H2S. The airborne concentrations of substances measured in the present study were all lower than most of published studies conducted in mainly enclosed swine buildings. Distinct characteristics, including maintaining swine houses in an open status and frequent spraying water inside the stalls, significantly reduce accumulation of gases and airborne particulates.

Rapid quantification of viable legionellae in water and biofilm using ethidium monoazide coupled with real‐time quantitative PCR

Aims:  To optimize ethidium monoazide (EMA) coupled with real‐time quantitative PCR (qPCR) and to evaluate its environmental applicability on quantifying viable legionellae in water and biofilm of cooling towers and hot water systems.

Inlet characteristics of bioaerosol samplers

Abstract The inlet sampling characteristics of several commercial bioaerosol samplers operating in indoor and outdoor environments have been analyzed by use of available and newly developed equations for sampling efficiency. With a focus on the physical aspects of sampling efficiency, the aspiration and transmission efficiencies have been calculated for the bioaerosol particle size range 1–30 μm, which represents single bacteria, bacteria aggregates, bacteria carrying particles, fungal spores, yeast, and pollen. Under certain sampling conditions, the bioaerosol concentration was found to be significantly over- or underestimated. At wind velocities between 0 and 500 cm s−1, calculations show that the AGI-30 would sample 1–10 μm particles with an inlet sampling efficiency of 20–100%. The entrance efficiency of the 6-stage Andersen viable sampler is 90–150% when sampling isoaxially with respect to horizontal aerosol flows, and 8–100% when oriented vertically at a right angle to the horizontal aerosol flow. For the Burkard portable air sampler, an even wider range of deviation may occur. The bioaerosol samplers used for large particles such as pollen are even less accurate: e.g. 10 times the ambient concentration of Lycopodium spores has been calculated to be aspirated by the Lanzoni sampler when operated at 0.5 1 min−1 facing the wind at wind velocity of about 500 cm s−1. The actual bioaerosol concentration can be calculated from the measured data by use of the indicated procedures. The sampling efficiency graphs presented can be used to bracket the sampling conditions that enable the investigator to avoid or minimize significant sampling biases for each sampler. The findings can also be used for the design of new samplers or for improving commercially available samplers.

Effects of chlorination and heat disinfection on long-term starved Legionella pneumophila in warm water.

Aims:  To characterize the efficacy of widely accepted heat and chlorination on culturable and non‐culturable Legionella pneumophila in starved and warm water.

Evaluation of real‐time PCR methods for quantification of Acanthamoeba in anthropogenic water and biofilms

Aims:  To assess two real‐time PCR methods (the Riviere and Qvarnstrom assays) for environmental Acanthamoeba.

Factors affecting microbiological colony count accuracy for bioaerosol sampling and analysis.

The effects of the following variables on the occurrence of colony masking (the indistinguishable merging or overlap of sufficiently close colonies) were evaluated experimentally using the bacterium Bacillus subtilis: spore density on a collection surface, concentration of nutrients in the culture medium, sample incubation time, and ability of an observation system to distinguish overlapped colonies. Increasing spore surface density and incubation time increased colony masking, whereas lowering nutrient concentration decreased colony diameter and, therefore, masking but also limited spore germination and growth. Overall, full-strength medium was best for accurate counting of early microcolonies examined with the aid of a microscope, whereas half- or quarter-strength medium was better for counting older readily observable macrocolonies. Masking bias was determined for varying spore surface densities and colony diameters and was applied to two widely used slit-to-agar bioaerosol impactors. Appropriate collection times have been determined for these samplers to minimize colony masking for expected bioaerosol concentrations. It was found, for example, that 6-min samples collected from an environment with an air concentration of 10(3) CFU m-3 would result in colony surface densities, for 3-mm colonies, of 1.5 and 3.9 microorganisms cm-2 for the two samplers with respective masking biases of < 10% and < 20%.

Ultraviolet Germicidal Irradiation and Titanium Dioxide Photocatalyst for Controlling Legionella pneumophila

Legionella pneumophila , a causative agent of Legionnaires disease and Pontiac fever, is an important microbe to be addressed. Total recovery rates of Legionella pneumophila were evaluated in a chamber by three sampling methods: AGI-30 impinger, impactor, and nuclepore filtration and elution. Our results demonstrated that impingers are likely to perform better than impaction and filtration methods. These might be related to the stronger sampling stress from impaction and dehydration stress from filtration. With regard to control techniques, ultraviolet germicidal irradiation (UVGI) and titanium dioxide photocatalyst (PCO) were considered to be promising to inactivate Legionella pneumophila . In this investigation, the influences of UV dosage and relative humidity on UVGI effectiveness and relative humidity and face velocity on germicidal effectiveness of titanium dioxide (TiO 2 ) coating filters were evaluated in a laboratory test chamber. It was indicated that a very low UVGI dosage of 289 to 860 w W sec/cm 2 was required to produce a 5 log decrease in concentration of Legionella pneumophila . Our results demonstrated that penetrations of Legionella pneumophila were in the range of 0.04-0.27 for the TiO 2 -coating filter with UV light. It was recommended that UVGI and the TiO 2 catalyst filter do provide a good germicidal capacity for Legionella pneumophila .

Assessment of Bioaerosol Sampling Techniques for Viable Legionella pneumophila by Ethidium Monoazide Quantitative PCR

Legionella pneumophila causes severe pneumonia and Pontiac fever in humans. Rapid and sensitive bioaerosol monitoring techniques for viable L. pneumophila are unavailable. Coupled with a newly developed viable assay called ethidium monoazide with quantitative PCR (EMA-qPCR), this study applies EMA-qPCR to aerobiology for the first time to evaluate the effects of the method of sampling (all-glass impinger (AGI-30), BioSampler, and MAS-100 sampler) and sampling time (3, 30, 60 min) on the collection of viable L. pneumophila. The effects of the collection fluid (deionized water (DW) and Tween mixture) and the replenishment of DW every 15 min during 60-min sampling were also assessed. Escherichia coli, as a model microorganism in bioaerosol research, was also tested. Using the Tween mixture (DW containing 1% peptone, 0.01% Tween 80, and 0.005% antifoam), the AGI-30 and BioSampler performed significantly better than the MAS-100 sampler for collecting viable L. pneumophila and viable E. coli (P < 0.05). An increase in sampling time adversely affected the quantification of both bacterial species (P < 0.05). The collection with DW yielded greater recovery of viable L. pneumophila than the Tween mixture in both AGI-30 and BioSampler, regardless of sampling time, by a factor of 1.4–6.9 (P < 0.05). The replenishment of DW every 15 min further improved the collection of viable L. pneumophila. This study demonstrates that viable L. pneumophila can be efficiently sampled by the AGI-30 and BioSampler and successfully quantified by EMA-qPCR.