Shawn G. Gibbs

Isolation of antibiotic-resistant bacteria from the air plume downwind of a swine confined or concentrated animal feeding operation.

Objective In this study we evaluated the levels of antibiotic- and multidrug-resistant bacteria in bioaerosols upwind, within, and downwind at locations 25 m, 50 m, 100 m, and 150 m from a swine confined animal feeding operation. Design We used Andersen two-stage samplers to collect bacterial samples, the replicate plate method to isolate organisms, and the Kirby-Bauer disk diffusion method to determine antibiotic resistance. Results The percentage of organisms resistant to at least two antibiotic classes and all four classes evaluated were, respectively, 2.1 and 3.0 times higher inside (n = 69) than upwind (n = 59) of the facility. Staphylococcus aureus was the most prevalent organism recovered. Concentrations of antibiotic-resistant S. aureus decreased with increasing distance from the facility. Using Fisher’s exact methods, the change in distribution of antibiotic resistance profiles for each antibiotic was statistically significant (oxytetracycline, p = 0.010; tetracycline, p = 0.014; ampicillin, p = 0.007; erythromycin, p = 0.035); however, this relationship was not seen with lincomycin and penicillin (p > 0.05). In addition, the levels of antibiotic-resistant S. aureus 25 m downwind were significantly greater than the levels from samples taken upwind from the facility for the same four antibiotics (p < 0.05). The percentage of resistant group A streptococci and fecal coliform increased within the facility compared with upwind values for all antibiotics evaluated, except for lincomycin. The percentage of resistant total coliform organisms increased within the facility compared with upwind values for oxytetracycline and tetracycline. Conclusions Bacterial concentrations with multiple antibiotic resistances or multidrug resistance were recovered inside and outside to (at least) 150 m downwind of this facility at higher percentages than upwind. Bacterial concentrations with multiple antibiotic resistances were found within and downwind of the facility even after subtherapeutic antibiotics were discontinued. This could pose a potential human health effect for those who work within or live in close proximity to these facilities.

Airborne Antibiotic Resistant and Nonresistant Bacteria and Fungi Recovered from Two Swine Herd Confined Animal Feeding Operations

Inhalation of microorganisms could be a health concern for workers inside and downwind of animal confinement units. Using the Andersen two-stage viable microbial particle sizing sampler, air samples were collected from locations upwind, inside, and downwind during two visits to two swine herd confined animal feeding operations. Six samples were taken at each location on each site. Bacteria isolated from each site were then tested for antibiotic resistance using the Kirby-Bauer disc diffusion method. Resistant bacterial forms were found inside and downwind of the swine confinement facilities, indicating that resistant organisms were being produced in and released from these facilities. Resistance to a battery of antibiotics including ampicillin, erythromycin, oxytetracycline, penicillin, tetracycline, and tylosin was found in the following bioaerosols: Staphylococcus aureus,Salmonella spp., and fecal coliforms. The major conclusion reached by this study was that bacteria were recovered inside and downwind of these facilities in levels that previous studies had stated could cause a potential human health hazard.

Bacterial Plume Emanating from the Air Surrounding Swine Confinement Operations

The objective of this study was to evaluate the levels of bacteria in the air plume immediately upwind at 25 m and downwind at locations 25 m, 50 m, 100 m, and 150 m from a confined animal feeding operation (CAFO). It was hypothesized that this would give insight into determining the maximal distance that bacterial organisms release from a CAFO could travel, which would be important in determining the optimal siting distance for future CAFO in relation to high population areas. The Andersen two-stage sampler was used to collect all of the bacterial samples from the animal confinement facilities. The data show a marked increase in bacterial CFUs/m3 inside the facility (18,132 CFU/m3 average) versus upwind (63 CFU/m3 average) and a steady downwind decrease out to approximately 150 m. Staphylococcus aureus was found to account for 76% of the organisms recovered. We conclude that the optimal placement of a swine CAFO would be at least 200 m from a residential area.

Occurrence of faecal contamination in households along the US–Mexico border

Aims:  The study aim was to determine the presence of total and faecal coliforms on kitchen surfaces, in tap water and on the hands of caregivers in households on both sides of the US–Mexico border.

Quantitative microbial risk assessment of a drinking water – wastewater cross-connection simulation

Quantitative microbial risk assessment is a useful way to predict the incidence of infection and illness within a community following exposure to pathogens. We used this risk assessment technique t...

Differential regulation of myometrial prostaglandin production by changes in length

OBJECTIVE The purpose of this study was to determine whether stretching and shortening of human myometrial strips alters prostaglandin production. STUDY DESIGN We measured 6-keto prostaglandin F1alpha (PGF1alpha; a PGI2 metabolite) and PGF2alpha in the contraction baths of myometrial strips that were obtained at cesarean delivery from 5 term pregnant women. Fluid was collected after the stretching and after the strip lengths were decreased by 4%, 6%, or 8%. Prostaglandin concentrations were measured in triplicate by competitive enzyme immunoassay and compared by Kruskal-Wallis tests. RESULTS Stretching myometrial strips increased the production of 6-keto PGF1alpha by 31%, but not PGF2alpha. Shortening strips had little effect on 6-keto PGF1alpha production, but increased PGF2alpha production by 158%. CONCLUSION Stretching myometrial strips from pregnant women increases synthesis of PGI2; shortening strips increases synthesis of PGF2alpha. Differential prostaglandin synthesis that is related to myometrial stretching and shortening could play a role in uterine quiescence during gestation and increased contractility during parturition.

Seasonal Fine and Coarse Culturable Fungal Constituents and Concentrations from Indoor and Outdoor Air Samples Taken from an Arid Environment

This study was undertaken to determine the normal indoor and outdoor airborne culturable fungal constituents and concentrations of an arid environment. Air samples were taken with two-stage, ambient, culturable sampler systems and analyzed for nine specific fungal genera from 50 homes as a repeated measure during each season of the year. These homes had no previous histories of indoor air quality issues. This study detected seasonal differences for the arid environment between different culturable fungal concentrations across the two size ranges. The highest concentrations were during fall, in the outdoor fine-size range. The lowest concentrations were the indoor coarse concentrations in the spring. From this study it can be concluded that Cladosporium spp. had the highest concentrations during fall in an arid environment. The overall findings suggest that Cladosporium had concentrations greater than the other genera evaluated, specifically, the fall outdoor fine concentrations. Seasonality was found to be a key factor in determining the variability of fungal constituents and concentrations within the arid indoor and outdoor environments. The fine-size range was 12 times and 6 times greater than the coarse-size range for indoor and outdoor samples, respectively, which accounted for the majority of fungal organisms. In addition, the results from this study in an arid climate differ from those conducted in a moister climate.

Comparison of Nondeployable Hearing Profiles by Army Component (Active Duty, National Guard, and Reserve) and by Gender

The Hearing Conservation Service at Fort Bliss conducted baseline-hearing assessments from January 2003 to March 2005 on 14,974 soldiers in the Active Duty (AD), National Guard (NG), and Reserve Component (RC). The percentages of soldiers with >H-2 (i.e., nondeployable) hearing profiles based on Army component and gender are as follows: AD male = 2.21%; AD female = 0.65%; NG male = 5.05%; NG female = 1.64%; RC male = 5.02%; and RC female = 0.54%. Female soldiers in all three components and AD male soldiers are not significantly different (p < 0.05) from each other and have a significantly lower percentage of >H-2 hearing profiles than NG and RC male soldiers after adjusting for age. With the Army engaged in worldwide missions, these results should prove useful to commanders and medical officers for assessing deployment capabilities and for hearing conservation interventions.

Hearing Threshold Comparisons between 2001-02 NHANES and 2003-05 Fort Bliss U.S. Army Service Components

This study compares population mean hearing threshold levels in decibels (dB) at 4 kHz among the 2001-02 National Health and Nutrition Examination Survey (NHANES) (n=1872) and the 2003-05 Fort Bliss Army Active Duty (AD) (n=9096), National Guard (NG) (n=3842), and Reserve Components (RC) (n=2025) and by gender. Comparisons between male populations show that mean hearing thresholds are not significantly different (p<0.05) between U.S. Army Active Duty males and NHANES males, which differ from a 1984 U.S. Army Active Duty/1971-74 NHANES study showing significantly higher hearing thresholds for the Army Active Duty population. In addition, this study shows that Active Duty males have significantly lower hearing thresholds than National Guard males at ages <40 years old. Female groups generally have significantly lower hearing thresholds than male groups at all ages, but there are not significant differences between female military and civilian populations.

Evaluation of neighborhood treatment systems for potable water supply.

Piped water is available in Ciudad Juárez, Chihuahua, México, but residual disinfectant is not reliably found in the public drinking water supply. Lack of confidence in the public supply leads many residents to rely on bottled water. To provide consistent disinfection, two health clinics were equipped with ultraviolet disinfection systems, and neighboring households were encouraged to obtain their drinking water from the treatment systems. Use of the treated water declined from 62% of self-selected study participants at the time of the first visit to 40% at the second visit. During the first visit, diarrhea prevalence was similar among households using treated water and other water sources yet diarrhea prevalence was higher among households using the treated water during the second visit. Microbiological quality of the treated water in the homes was not demonstrably superior to that of other sources.