Evaluation of clinical characteristics and bacterial isolates in dogs with bacterial keratitis: 97 cases (1993-2003)

OBJECTIVE: To evaluate clinical characteristics and breeds affected with bacterial keratitis and compare patterns of resistance in bacterial isolates over time in dogs. DESIGN: Retrospective cross-sectional study. ANIMALS: 97 dogs with bacterial keratitis. PROCEDURE: Dogs with bacterial keratitis were identified from teaching hospital medical records at the Universities of Tennessee and Florida during the years 1993 to 2003. Data were collected pertaining to breed, Schirmer tear test results, treatments administered at the time of initial examination, bacterial species isolated, and resistance to selected antimicrobials. RESULTS: 66% of the dogs were brachycephalic, 54% had tear production < 15 mm/min, and 29% were receiving a corticosteroid at the time of initial examination. The most common bacteria isolated were Staphylococcus intermedius (29%), beta-hemolytic Streptococcus spp (17%), and Pseudomonas aeruginosa (21%). Staphylococcus intermedius isolates had limited resistance to certain antimicrobials. More than 80% of beta-hemolytic Streptococcus spp isolates were resistant to neomycin, polymyxin B, and tobramycin. Isolates of P aeruginosa were susceptible to tobramycin and gentamicin and had limited resistance to ciprofloxacin and enrofloxacin. Among bacterial species isolated, there was no evidence of development of antimicrobial resistance over time. CONCLUSIONS AND CLINICAL RELEVANCE: Data suggested that administration of ciprofloxacin or a combination of a first-generation cephalosporin and tobramycin may be used in the treatment of bacterial keratitis while awaiting results of bacterial culture and susceptibility testing. Evidence suggests that current methods of medical management of bacterial keratitis are not associated with increased antimicrobial resistance.     

Modulation of equine neutrophil adherence and migration by the annexin-1 derived N-terminal peptide, Ac2-26

Neutrophil activation, whilst a key component of host defence, must be tightly regulated in order to avoid an inappropriate cellular response. Annexin-1, which is present in large amounts in neutrophils, and its N-terminal peptides, reduce neutrophil accumulation but annexin peptides have also been shown to exhibit neutrophil activating properties. We have recently shown annexin-1 to be present in equine neutrophils and demonstrated that the annexin-1-derived peptide, Ac2-26, can both reduce superoxide production by these cells in response to other stimuli and directly induce free radical production at a higher concentration. In the present study, we have further characterised the effects of Ac2-26 on equine neutrophil function. In addition, as anti-inflammatory glucocorticoids are known to up-regulate annexin-1, we have examined the effects of dexamethasone on annexin-1 expression in equine leukocytes. The effects of Ac2-26 alone and on agonist (CXCL8, leukotriene (LT)B(4) and PAF)-induced adherence and migration were examined by measuring adhesion of neutrophils to serum-coated plastic and by use of a ChemoTx migration assay. The role of formyl peptide receptors (FPRs) in mediating the effects of Ac2-26 was examined using the pan-FPR antagonist, BOC-2. Flow cytometry was used to measure the effects of dexamethasone on annexin-1 expression. Pre-incubation with Ac2-26 (10(-5)M) significantly inhibited neutrophil adhesion and migration in response to other agonists but when used alone could also induce these responses. The stimulatory and inhibitory effects of Ac2-26 were reduced by BOC-2, indicating a dependency on FPR activation. Dexamethasone increased the percentage of annexin-1 positive neutrophils and mononuclear cells by 1h post treatment (from 45±5% to 93±1% and 62±14% to 87±9% for neutrophils and monocytes, respectively) but by 4h there was no difference from control cells. No difference was seen between the percentages of annexin-1 positive cells pre- and post-treatment in animals that had undergone a dexamethasone suppression test. The attenuation of agonist-induced adherence and migration by Ac2-26 may play a part in regulating recruitment of equine neutrophils in inflammatory conditions of the horse. However, if high concentrations are produced in vivo following release of annexin-1 from activated cells, direct stimulatory effects may occur which could be either beneficial or detrimental. The therapeutic efficacy of anti-inflammatory steroids in the horse may be mediated in part by increasing annexin-1 expression although this effect appears to be short-lived.     

Topographic placement of management practices in riparian zones to reduce water quality impacts from pastures

Riparian buffers, a best management practice (BMP), lessen environmental impacts caused by pasture-based agriculture by excluding livestock from streams and removing sediment and nutrients from overland flow before they enter the watercourse. Geospatial data analysis of digital elevation models (DEMs) can improve BMP placement by ensuring that BMPs intercept flow paths. Livestock heavy use areas and riparian buffers within 100?m of the stream were digitized using aerial photography of Spring Creek watershed (Pennsylvania, USA). Flow path lengths and stream entry points from heavy use areas, from all agricultural land uses, and from a random sample of points were calculated using 1, 10, and 30?m DEM resolutions. Euclidean distances identified the nearest stream entry point regardless of topography. Drainage areas for each streambank cell were evaluated using each DEM resolution. Topographic calculations differed significantly from Euclidean, with median differences of 14.3?m for flow path length and 24.1?m between stream entry points for the 10?m DEM. Existing buffers intercepted runoff from only 23?% of heavy use areas. Drainage areas ranged from one to hundreds of DEM cells. Any DEM is an arbitrary representation of a continuous surface; both resolution and processing method affect the suitability of such a representation for any given purpose. We found that 30?m DEMs did not provide reasonable flow path estimates at the scale of grazing agriculture in this region, while Pennsylvania 1?m DEMs were minimally smoothed during DEM preparation, resulting in erratic flow paths. The 10?m DEMs were the most suitable available DEM product, and should be used in conjunction with site visits for planning pasture BMP placement.     

Monoclonal antibodies specific for Campylobacter fetus lipopolysaccharides

Four monoclonal antibodies (mAbs) (M1357, M1360, M1823 and M1825) which reacted with Campylobacter fetus lipopolysaccharide (LPS) core region epitopes were produced and characterized. Reactivity of these mAbs with C. fetus core LPS epitopes was determined by enzyme-linked immunosorbent assay (ELISA) with whole cell proteinase K digests and phenol-water extracted LPS, and by immunoblotting with proteinase K digests. The specificities of the four mAbs were evaluated using an indirect ELISA. One of the mAbs reacted with 42 and three of the mAbs reacted with 41 of the 42 C. fetus strains examined. No reaction was observed between the four mAbs and 32 non-C. fetus bacteria tested, with the exception of one mAb with one organism. The four mAbs reacted with serotype A and B strains indicating the presence of shared epitopes in C. fetus LPS core oligosaccharides. The specificities of three mAbs previously produced to C. fetus LPS O-antigens (M1177, M1183 and M1194) were also evaluated and no reaction was observed with these mAbs and the 32 non-C. fetus bacteria tested. Strong immunofluorescence reactions were observed with the anti-O chain mAbs and selected C. fetus strains of the homologous serotype. These anti-LPS core oligosaccharide and anti-LPS O chain mAbs are highly specific for C. fetus and are potentially useful as immunodiagnostic reagents for detection, identification and characterization of C. fetus.     

Intraperitoneal vaccination of rams against brucella epididymitis

Extract

Sir, —In reply to the letter of Quinlivan and Wallace in this issue, I must state that their comments give me no reason to modify or retract my comments in Surveillance (1978) No.5.     

Source relationships between streambank soils and streambed sediments in a mercury-contaminated stream

Purpose

In contaminated streams, understanding the role of streambank and streambed source contributions is essential to developing robust remedial solutions. However, identifying relationships can be difficult because of the lack of identifying signatures in source and receptor pools. East Fork Poplar Creek (EFPC) in Oak Ridge, TN, USA received historical industrial releases of mercury that contaminated streambank soils and sediments. Here, we determined relationships between the contaminated streambank soils and sand-sized streambed sediments.

Materials and methods

Field surveys revealed the spatial trends of the concentrations of inorganic total mercury (Hg) and methyl mercury (MeHg), Hg lability as inferred by sequential extraction, particle size distribution, and total organic carbon. Statistical tests were applied to determine relationships between streambank soil and streambed sediment properties.

Results and discussion

Concentrations of Hg in streambank soils in the upper reaches averaged 206 mg kg^?1 (all as dry weight) (n?=?457), and 13 mg kg^?1 in lower reaches (n?=?321), while sand-sized streambed sediments were approximately 16 mg kg^?1 (n?=?57). Two areas of much higher Hg and MeHg concentrations in streambank soils were identified and related to localized higher Hg concentrations in the streambed sediments; however, most of the streambank soils have similar Hg concentrations to the streambed sediments. The molar ratio of Hg to organic carbon, correlation between MeHg and Hg, and particle size distributions suggested similarity between the streambank soils and the fine sand-sized fraction (125–250 μm) collected from the streambed sediments. Mercury in the fine sand-sized streambed sediments, however, was more labile than Hg in the streambank soils, suggesting an in-stream environment that altered the geochemistry of sediment-bound Hg.

Conclusions

This study revealed major source areas of Hg in streambank soils, identified possible depositional locations in streambed sediments, and highlighted potential differences in the stability of Hg bound to streambank soils and sediments. This work will guide future remedial decision making in EFPC and will aid other researchers in identifying source–sink linkages in contaminated fluvial systems.