James E. Urban

Assessment of Bioaerosols in Swine Barns by Filtration and Impaction

Bioaerosol concentrations inside one naturally ventilated and one mechanically ventilated swine finishing barn were assessed by sampling air using membrane filtration and impaction (six-stage Andersen sampler), and assayed by culture method. The barns, located on the same commercial farm in northeast Kansas, did not show any significant difference (p > 0.05) in concentrations of total and respirable airborne microorganisms. The overall mean total concentrations inside the two barns were 6.6 × 104 colony forming units (CFU)/m3 (SD = 3.8 × 104 CFU/m3) as measured by filtration and 8.6 × 104 CFU/m3 (SD = 5.1 × 104 CFU/m3) by impaction. The overall mean respirable concentrations were 9.0 × 103 CFU/m3 (SD = 4.1 × 103 CFU/m3) measured by filtration and 2.8 × 104 CFU/m3 (SD = 2.2 × 104 CFU/m3) by impaction. Total and respirable CFU concentrations measured by impaction were significantly (p < 0.05) higher than that by filtration. The persistent strains of microorganisms were various species of the following genera: Staphylococcus, Pseudomonas, Bacillus, Listeria, Enterococcus, Nocardia, Lactobacillus, and Penicillium. It appears that filtration sampling can be used for a qualitative survey of bioaerosols in swine barns while the Andersen sampler is suitable for both quantitative and qualitative assessments.

Flies and Their Bacterial Loads in Greyhound Dog Kennels in Kansas

Abstract. Breeders of greyhound dogs traditionally feed racing animals and nursing bitches raw meat, and that meat generally is obtained frozen from commercial renderers. Previous studies have shown that the rendered meat is frequently contaminated with enteric bacteria, including Salmonella spp., and that during thawing the rendered meat is exposed to filth flies common in dog kennels. Nursing greyhound pups tend to experience a high morbidity and mortality from intestinal infections, and we attempted to determine in this study whether enterics could be spread to pups through contaminated flies. At intervals during 1995 and 1996, flies were trapped or were net-collected from 10 dog breeding kennels in the region around Abilene, KS. Trapped flies were identified and counted to determine population numbers, and netted flies were cultured in tetrathionate broth and streaked to medium selecting for Salmonella sp. and other lactose-negative Gram (−) bacteria. The relative numbers of different fly species varied with the sampling method, but traps and sweep nets produced similar proportions of the different fly species. Blow flies were twice as likely to be contaminated with enteric bacteria as any other fly. The most common enteric bacteria found were Proteus spp., followed by Providencia spp., Pseudomonas spp., and Salmonella spp. The incidence of Salmonella and Proteus spp. seemed to correlate more with accessibility of flies to dog excrement than to rendered meat. The apparent high incidence of enteric contamination of filth flies clearly implicates them as vectors of enteric diseases in kennels.

Killing of flies in electrocuting insect traps releases bacteria and viruses.

Electrocuting insect traps (EIT) are popular devices frequently used by homeowners and food handlers attempting to localize the control of flying insects, including the ubiquitous house fly (Musca domestica L.). The traps contain a visual attractant and a high-voltage metal grid. Upon contact with the grids, the insects are disintegrated by the high voltage. As part of a systematic evaluation of EITs and their role in infectious disease spread, we quantitated spread of bacteria and a bacterial virus during electrocution of house flies. We loaded flies with Serratia marcescens or with the Escherichia coli phage ΦX174 and placed sprayed or fed flies into a room containing an EIT. While flies were being electrocuted, liberated particles and bacteria were assayed via agar plates or via air filtration samplers. Sprayed flies released one of every 10,000 of the added bacteria or viruses, and fed flies released one of every 1,000,000 of the consumed bacteria or viruses. Results of our studies suggest EITs could play a role in the spread of infectious disease agents, but the potential is influenced by the insects route of contamination.

DNA replication in Escherichia coli 15T− growing at 20 °C

Abstract Escherichia coli 15T − grows slowly in succinate or aspartate-M9 media. In both media, a gap in DNA replication is observed at 37 °C which is either not present at 20 °C or of very much shorter duration than at 37 °C. However, dichotomous replication is not observed in glucose M9 at 20 °C. The results suggest that initiation of replication in glucose is different from that in aspartate or succinate cultures. Replication at 20 °C is faster than expected if cells were allowed to begin replicating their DNA at 37 °C; conversely, replication at 37 °C is slower than expected if cells began replicating their DNA at 20 °C.

Adverse effects of microgravity on the magnetotactic bacterium Magnetospirillum magnetotacticum.

Bacteria that contain magnetosomes display magnetotaxis and align themselves to the earths magnetic field. When magnetotactic bacteria were first isolated several decades ago it was presumed that geomagnetic orientation allowed magnetotactic bacteria to orient themselves downward towards sediments where the habitat is favorable to their growth and metabolism. As more species of magnetotactic bacteria have been isolated and studied, differences in magnetotactic responses have been observed which suggested that the primary role of magnetosomes might simply be to enhance a microorganisms response to gravity. To resolve if gravity influences magnetotactic behavior in bacteria, Magnetospirillum magnetotacticum was used to examine magnetotaxis in the absence of gravity. Experiments to compare the orientation of bacteria to north- or south-pole magnets were conducted in normal gravity and in the microgravity environments aboard the Space Shuttle and Space Station MIR. In each of the microgravity situations studied, bacteria were impaired in their ability to orient to magnets and the failure to exhibit magnetotaxis appeared to be a function of the loss of magnetosomes. The disappearance of aggregated magnetosomes seemed to correlate with a general loss of cellular integrity in microgravity.

Microwave Sanitization of Polyester and Cotton

The potential of using 2450-MHz microwave radiation to dry and sterilize polyester and cotton fabrics was evaluated against Staphylococcus aureus, Escherichia coli, and Bacillus cereus. B. cereus spores were the most tolerant microorganisms of microwave radiation, and E. coli were the most sensitive. All S. aureus and E. coli cells were killed within seven minutes of exposure to microwave radiation. Fabric conditions of steam released and steam retained did not affect the percentage reduction in microorganisms. Microwave drying was substantially more effective than convection oven drying. Microwave exposure had no effect on the elongation of polyester and cotton, but cottons strength decreased 10% after five minutes of microwave exposure.

Antimicrobial activity of dogwood fruits (Cornus drummondii) from winter food caches of eastern woodrats (Neotoma floridana).

Post-harvest loss of resources to microbial competitors affects a number of species of animals, and many of them have evolved behaviors that reduce the likelihood of such loss. We previously described the inhibition ofBacillus psychrophilus by dogwood fruits (Cornus drummondii), which can comprise a significant portion of the winter food cache of the eastern woodrat (Neotoma floridana). The present study is a further investigation of the ability of dogwood fruits to inhibit growth ofB. psychrophilus. Additionally, we tested the antimicrobial activity of dogwood fruits onEscherichia coli andStaphlococcus aureus. Results of our study indicate that fresh fruits inhibit the growth ofB. psychrophilus andS. aureus but notE. coli. However, fruits taken from woodrat dens after four and six months storage inhibited growth of all three species of bacteria. Further, the strength of inhibition increased over the test period. We suggest the presence of an inhibitor allows woodrats to compete effectively for a valuable and limited food resource.

Effects of microgravity on the binding of acetylsalicylic acid by Rhizobium leguminosarum bv. trifolii.

Bacteroids can be induced in vitro by treating growing Rhizobium leguminosarum bv. trifolii with succinic acid or succinic acid structural analogs like acetysalicylic acid. Quantitating bacteroid induction by measuring acetylsalicylic binding under normal (1 g) conditions showed two forms of binding to occur. In one form of binding cells immediately bound comparatively high levels of acetylsalicylic acid, but the binding was quickly reversed. The second form of binding increased with time by first order kinetics and reached saturation in 40 s. Similar experiments performed in the microgravity environment aboard the NASA 930 aircraft showed only one form of binding and total acetylsalicyclic acid bound was 32% higher than at 1 g.

Isolation of a new division altered mutant of Escherichia coli 15T

A Mutant of Escherichia coli 15T− (555-7) has been isolated which grows at a rate equal to that of the wild type at division times of 40 min or less, but grows faster than normal at division times greater than 40 min. At division times greater than 40 min the division time of the mutant is identical to the chromosome synthesis time of the wild type in the same medium. In one slow-growth medium (M9-aspartic acid) chromosome synthesis and gap times of the mutant were measured and the time required for synthesis of a chromosome was approximately the same as that of the wild type, but the gap in DNA synthesis observed in the mutant was only about 12% of that observed in wild type.

Microgravity effects on magnetotactic bacteria

An unusual group of iron bacteria has recently been discovered which form inclusion bodies containing a form of iron oxide known as magnetite (ferrosoferric oxide, Fe3O4.) The inclusions are of a nano-particle size, are encased within a protein envelope, and are called magnetosomes. Magnetosomes are arranged adjacent to one another and parallel to the long axis of the cell such that cells appear to contain an electron-dense string of beads. The bacteria containing magnetosomes exhibit metal reductase activity, an activity critical to element recycling in nature, and the inclusions are a means for the organism to sequester reduced iron atoms and thereby keep iron reduction stoichiometry favorable. The magnetosomes also allow the bacteria to display magnetotaxis, which is movement in response to a magnetic field, such as the north or south magnetic poles. It is presumed that the bacteria use the alignment to the earth’s magnetic field to orient themselves downward towards sediments where the habitat is favo...