RoseAnn Miller

Patterns of Antimicrobial Resistance Observed in Escherichia coli Isolates Obtained from Domestic- and Wild-Animal Fecal Samples, Human Septage, and Surface Water

ABSTRACT A repeated cross-sectional study was conducted to determine the patterns of antimicrobial resistance in 1,286 Escherichia coli strains isolated from human septage, wildlife, domestic animals, farm environments, and surface water in the Red Cedar watershed in Michigan. Isolation and identification of E. coli were done by using enrichment media, selective media, and biochemical tests. Antimicrobial susceptibility testing by the disk diffusion method was conducted for neomycin, gentamicin, streptomycin, chloramphenicol, ofloxacin, trimethoprim-sulfamethoxazole, tetracycline, ampicillin, nalidixic acid, nitrofurantoin, cephalothin, and sulfisoxazole. Resistance to at least one antimicrobial agent was demonstrated in isolates from livestock, companion animals, human septage, wildlife, and surface water. In general, E. coli isolates from domestic species showed resistance to the largest number of antimicrobial agents compared to isolates from human septage, wildlife, and surface water. The agents to which resistance was demonstrated most frequently were tetracycline, cephalothin, sulfisoxazole, and streptomycin. There were similarities in the patterns of resistance in fecal samples and farm environment samples by animal, and the levels of cephalothin-resistant isolates were higher in farm environment samples than in fecal samples. Multidrug resistance was seen in a variety of sources, and the highest levels of multidrug-resistant E. coli were observed for swine fecal samples. The fact that water sample isolates were resistant only to cephalothin may suggest that the resistance patterns for farm environment samples may be more representative of the risk of contamination of surface waters with antimicrobial agent-resistant bacteria.

Proposal of a 2-Tier Histologic Grading System for Canine Cutaneous Mast Cell Tumors to More Accurately Predict Biological Behavior

Currently, prognostic and therapeutic determinations for canine cutaneous mast cell tumors (MCTs) are primarily based on histologic grade. However, the use of different grading systems by veterinary pathologists and institutional modifications make the prognostic value of histologic grading highly questionable. To evaluate the consistency of microscopic grading among veterinary pathologists and the prognostic significance of the Patnaik grading system, 95 cutaneous MCTs from 95 dogs were graded in a blinded study by 28 veterinary pathologists from 16 institutions. Concordance among veterinary pathologists was 75% for the diagnosis of grade 3 MCTs and less than 64% for the diagnosis of grade 1 and 2 MCTs. To improve concordance among pathologists and to provide better prognostic significance, a 2-tier histologic grading system was devised. The diagnosis of high-grade MCTs is based on the presence of any one of the following criteria: at least 7 mitotic figures in 10 high-power fields (hpf); at least 3 multinucleated (3 or more nuclei) cells in 10 hpf; at least 3 bizarre nuclei in 10 hpf; karyomegaly (ie, nuclear diameters of at least 10% of neoplastic cells vary by at least two-fold). Fields with the highest mitotic activity or with the highest degree of anisokaryosis were selected to assess the different parameters. According to the novel grading system, high-grade MCTs were significantly associated with shorter time to metastasis or new tumor development, and with shorter survival time. The median survival time was less than 4 months for high-grade MCTs but more than 2 years for low-grade MCTs.

The Use of KIT and Tryptase Expression Patterns as Prognostic Tools for Canine Cutaneous Mast Cell Tumors

Cutaneous mast cell tumors (MCTs) are one of the most common tumors in dogs. Currently, prognostic and therapeutic determinations for MCTs are primarily based on the histologic grade of the tumor, but a vast majority of MCTs are of an intermediate grade, and the prognostic relevance is highly questioned. A more detailed prognostic evaluation, especially of grade 2 canine MCTs, is greatly needed. To evaluate the prognostic significance of KIT and tryptase expression patterns in canine cutaneous MCTs, we studied 100 cutaneous MCTs from 100 dogs that had been treated with surgery only. The total survival and disease-free survival time and the time to local or distant recurrence of MCTs were recorded for all dogs. Using immuno-histochemistry, 98 of these MCTs were stained with anti-KIT and antitryptase antibodies. Three KIT- and three tryptase-staining patterns were identified. The KIT-staining patterns were identified as 1) membrane-associated staining, 2) focal to stippled cytoplasmic staining with decreased membrane-associated staining, and 3) diffuse cytoplasmic staining. The tryptase-staining patterns were identified as 1) diffuse cytoplasmic staining, 2) stippled cytoplasmic staining, and 3) little to no cytoplasmic staining. Based on univariate and multivariate survival analysis, increased cytoplasmic KIT staining was significantly associated with an increased rate of local recurrence and a decreased survival rate. The tryptase-staining patterns were not significantly associated with any survival parameter. On the basis of these results, we propose a new prognostic classification of canine cutaneous MCTs, according to their KIT-staining pattern, that can be used for the routine prognostic evaluation of canine cutaneous MCTs.

Cellular Proliferation in Canine Cutaneous Mast Cell Tumors: Associations with c-KIT and Its Role in Prognostication

Canine cutaneous mast cell tumor (MCT) is a common neoplastic disease in dogs. Due to the prevalence of canine MCTs and the variable biologic behavior of this disease, accurate prognostication and a thorough understanding of MCT biology are critical for the treatment of this disease. The goals of this study were to evaluate and compare the utility of the proliferation markers Ki67, proliferating cell nuclear antigen (PCNA), and argyrophilic nucleolar organizing region (AgNOR) as independent prognostic markers for canine MCTs and to evaluate the use of these markers in combination, as each marker assesses different aspects of cellular proliferation. An additional goal of this study was to evaluate the associations between cellular proliferation and c-KIT mutations and between cellular proliferation and aberrant KIT protein localization in canine MCTs. Fifty-six MCTs treated with surgical excision alone were included in this study. Each MCT was evaluated for Ki67 expression, PCNA expression, and KIT protein localization using immunohistochemistry; for AgNOR counts using histochemical staining; and for the presence of internal tandem duplication c-KIT mutations using polymerase chain reaction amplification. In this study, increased Ki67 and AgNOR counts were both associated with significantly decreased survival. On the basis of these results, we recommend that the evaluation of cellular proliferation, including evaluations of both Ki67 expression and AgNORs, should be routinely used in the prognostication of canine MCTs. Additionally, the results of this study show that MCTs with aberrant KIT protein localization or internal tandem duplication c-KIT mutations are associated with increased cellular proliferation, further suggesting a role for c-KIT in the progression of canine MCTs.

EVALUATION OF THE INFLUENCE OF SUPPLEMENTAL FEEDING OF WHITE-TAILED DEER (ODOCOILEUS VIRGINIANUS) ON THE PREVALENCE OF BOVINE TUBERCULOSIS IN THE MICHIGAN WILD DEER POPULATION

A retrospective study was conducted to test the hypothesis that supplemental feeding of white-tailed deer (Odocoileus virginianus) from 1995 to 1997 was associated with the prevalence of bovine tuberculosis (TB) in free-ranging deer in northeastern Michigan. Bovine TB prevalence data were obtained from an ongoing surveillance program, while data relating to supplemental feeding and other risk factors were collected via in-person interviews. A multivariable Poisson regression modeling approach was used to test the stated hypothesis while controlling for other risk factors. Of the 389 potential participants, 59% agreed to participate in the study. Results showed that supplemental feeding of deer was associated with bovine TB in white-tailed deer. Specific risk factors associated with increasing risk for bovine TB were locating feed sites in areas with high levels of hardwood forests (O.R.=1.8, 95% C.I.=1.3–2.4), other large-scale feeding sites in the area (O.R.=1.1, 95% C.I.=1.0–1.2), the number of deer fed per year (O.R.=3.9, 95% C.I.=1.4–11.4), the numbers of feed sites spreading grain (O.R.=14.7, 95% C.I.=2.2–98.9), the quantity of grains provided at the site (O.R.=1.4, 95% C. I.=1.1–1.7), and the quantity of fruits and vegetables provided (O.R.=1.4, 95% C.I.=1.2–1.7). Conversely, factors associated with decreasing risk of bovine TB were locating feed sites in areas with high levels of hardwood forests (O.R.=0.1, 95% C.I.=0.02–0.4), locating feed sites in forests (O.R.=0.05, 95% C.I.=0.01–0.4), and the level of sites providing grain (O.R.=0.1, 95% C.I.=0.01–0.3). The results of this study suggest that banning the practice of supplemental feeding is a valid policy for control of bovine tuberculosis in free-ranging white-tailed deer.

The association of serum nonesterified fatty acids and cholesterol, management and feeding practices with peripartum disease in dairy cows

A prospective study was conducted to determine the relationship of serum nonesterified fatty acids (NEFA) and cholesterol concentrations and herd management practices to the occurrence of metritis, mastitis and retained placenta in Holstein cows in Michigan. Serum samples were collected once prepartum and once postpartum from 257 cows. Animals were under observation for disease occurrence from the date of calving until 3 months postpartum. Metabolic variables used were (1) prepartum only; (2) postpartum only; (3) the NEFA/cholesterol ratio for both pre- and postpartum samples. Management variables included maternity management, feed management, and factors such as season and parity. Multivariable logistic models with random-effect terms to account for the herd effect were used for data analysis. Results showed that: (1) metabolic events associated with energy insufficiency-increased fat mobilization and serum lipoprotein metabolism-were related to increased risk of metritis and retained placenta; (2) higher energy consumption during the last weeks of the dry period might reduce disease risk at parturition; (3) serum NEFA and cholesterol concentrations have potential as indicators of disease risk in dairy cows.

The Michigan equine monitoring system. II. Frequencies and impact of selected health problems

A prospective study was designed to document the frequencies of equine health problems in the state of Michigan, USA. A total of 2469 horses from a random sample of 138 equine operations were monitored in the study in two 12-month periods: 1992-1993 and 1993-1994. All the major breeds of horses in the state were proportionately represented in the sample. Using weighted annual incidence densities as measures of disease frequencies, the 10 most frequently observed groups of health problems were (from most to least frequent) leg lameness, dermatological problems, respiratory problems, hoof and foot problems, reproductive problems, systemic problems, colic, whole body lameness, neurological problems and gastrointestinal problems (other than colic). This ranking of the top 10 health problems was different from the ranking provided by equine owners/operators at the beginning of the study. Overall, very low specific mortality rates were observed in the study. However, the conditions that were associated with mortality resulted in fairly high case fatalities. The five specific illnesses that most commonly resulted in fatalities were (from greatest to least case fatality risk) systemic problems, colic, gastrointestinal problems (other than colic), neurological problems, and foot and hoof problems. Impact of disease was evaluated in terms of average duration of a case and days lost for performance. Neurological problems, lameness and dermatological problems had the longest duration per case. Neurological problems, lameness, respiratory problems and gastrointestinal problems (other than colic) had the longest average days lost per case.

Risk factors for colic in the Michigan (USA) equine population

A population-based prospective epidemiological study was conducted to assess risk factors for equine colic. A stratified sample of 3925 equids in 138 randomly selected equine farms in the state of Michigan was monitored in two 12-month rounds of data collection. Incidence densities were used to describe the rate of development of colic in the study population. Mortality rates, case fatality rates and survival rates were used to describe the severity of colic on the study population. Multivariable logistic regressions with random effects (grouped according to farm) were used to identify risk factors associated with occurrence of colic. A total of 3175 equids from 132 farms from the starting population of 3925 equids in 138 farms was used in the multivariable analysis. There were 77 cases of colic reported during the study period in 62 animals. Of these animals, 54 (87%) had one case, 5 (8%) had two cases, 2 (3%) had three cases, and 1 (2%) had seven cases. Of the cases reported, 49 (64%) were non-specific diagnoses, 13 (17%) impaction/acute intestinal obstruction colics, 7 (9%) spasmodic colics, 4 (5%) sand colics, 2 (3%) gas colics, 1 (1%) verminous mesenteric arteritis, and 1 (1%) enteritis due to ingestion of moldy grain. The annual incidence density of colic in the study was 3.5 cases per 100 equid-years. The surgical treatment risk was 17% (13/77). The overall mortality risk due to colic was 0.5 deaths per 100 equids, and the case fatality risk was 13% (10/77). The case fatality risk for cases treated surgically was 31% (4/13), while the case fatality risk for non-surgical colics was 10% (7/69). Risk factors associated with significantly increased likelihood of developing colic were foaling during the study, deworming during the study, increased age, and participation in showing activities. Geldings and equids provided group drinking water from sources other than tanks, buckets and automatic waterers were significantly associated with reduced risk of colic.

Risk factors for metritis in Michigan dairy cattle using herd- and cow-based modelling approaches

Abstract A prospective study, using the Michigan portion of the National Animal Health Monitoring System, was conducted to determine disease and management factors that affect the incidence of metritis in Michigan dairy herds. A stratified random sample representing 1% of all Michigan dairy herds was observed. Data related to herd, feeding, and reproduction management, disease and environmental risk factors, and cow-based disease and reproductive data were collected monthly for a 12 month period. Cows with complete management records that were observed for at least 3 months postpartum were included in the study (85 herds, 5278 cows). A multivariate linear regression model was developed for lactational incidence of metritis by herd, and a multivariate random-effects logistic model was developed for the occurrence of metritis by cows. Significant factors associated with increased occurrence of metritis included larger herds, problem calvings, overconditioning, underconditioning, and more active reproductive management. Factors associated with reductions in metritis involved good nutritional management, and working relationships with veterinarians for disease management. Implications for the significance of these factors are discussed, with emphasis on differences in interpretation and use of results from herd and cow-based analyses.

Changes in tetracycline susceptibility of enteric bacteria following switching to nonmedicated milk replacer for dairy calves.

ABSTRACT A randomized intervention study was conducted to determine if discontinuing use of calf milk replacer medicated with oxytetracycline results in increased tetracycline susceptibility in Salmonella and Campylobacter spp. and Escherichia coli in dairy calves over a 12-month period. Dairy herds with enteric bacteria with known low tetracycline susceptibility were enrolled for the study. Fecal samples from preweaned calves and environmental samples were collected from eight dairy herds in Michigan and New York State. Samples were collected monthly for 3 months prior to and 12 months after four of the eight herds discontinued medicated milk replacer feeding. Salmonella and Campylobacter spp. and E. coli were isolated, and antimicrobial susceptibility testing was conducted using automated broth microdilution. A total of 804 intervention and 1,026 control calf fecal samples and 122 intervention and 136 control environmental samples were collected for testing. No differences in owner-reported morbidity and mortality between treatment groups were seen. The intervention was significantly associated with increasing tetracycline susceptibility in E. coli and Salmonella. Tetracycline susceptibility increased in intervention herds for the first 3 months after switching to nonmedicated milk replacer but declined in subsequent months. Discontinuing the practice of feeding medicated milk replacers to calves increased tetracycline susceptibility in E. coli and Salmonella on dairy farms, without increasing cattle disease, but declines in effectiveness after 3 months suggest that other factors contribute to decreasing susceptibility on the farm.