Brandy A. Burgess

Effects of Restricted Antimicrobial Exposure on Antimicrobial Resistance in Fecal Escherichia coli from Feedlot Cattle

OBJECTIVES The primary objective was to evaluate differences in antimicrobial resistance among enteric bacteria recovered from feedlot cattle that were being raised without exposure to antimicrobial drugs (AMDs) and those reared using conventional practices. MATERIALS Forty pens of feedlot cattle (4557 total animals) that were being fed without AMD exposures were selected for enrollment as were 44 pens of cattle (4913 total animals) being fed for production of conventional beef products at the same feedlots. Fecal samples were collected from the floors of pens approximately biweekly through the middle of the feeding period and again prior to slaughter. Samples were cultured to recover nontype-specific Escherichia coli (NTSEC) and Salmonella enterica, and isolates were evaluated for susceptibility to a panel of AMDs. RESULTS Cattle enrolled in the study did not differ between groups in entry weight or finish weight, but cattle with restricted AMD and hormone exposures were fed for an average of 50 days longer than conventionally reared cattle (p < 0.001). Resistance among NTSEC isolates was most common to tetracycline, streptomycin, and sulfamethoxazole, and there were slightly higher prevalence of resistance among NTSEC isolates recovered from conventionally reared cattle. Therapeutic AMD exposures did not have a detectable impact on the prevalence of resistance among NTSEC. Although there were detectable temporal trends through the feeding period for resistance to tetracycline, naladixic acid, chloramphenicol, and cephalothin, the direction of trends differed among drugs and these trends were not associated with study groups. S. enterica was recovered rarely (0.73%) but at similar prevalences from cattle with both rearing methods. CONCLUSIONS These findings suggest that conventional feedlot production methods (including parenteral and in-feed use of AMDs) do not predictably or uniformly increase the prevalence of antimicrobial resistance among fecal NTSEC when compared with rearing methods that restrict exposure to AMDs.

Report of the third Havemeyer workshop on infection control in equine populations

Infectious diseases are an ever present threat to the health of individual horses, local, regional and national herds and the equine industry as a whole. Treating infectious disease has always been one of the foundations of veterinary medicine. However, infectious disease prevention is becoming increasingly important because of the high visibility of recent outbreaks of infectious disease, the increasing frequency and ease of national and international horse movement and emergence and re-emergence of equine pathogens. This is especially true in large, transient horse populations. For many veterinarians and facility managers, infection control remains a subject they are reluctant to discuss for fear of it reflecting poorly on them, yet management of infectious diseases is an unavoidable issue that must be addressed by all equine practitioners regarding every equine population under their care. The field of veterinary infection control, although still young compared with equivalent efforts in human medicine, has advanced considerably in the last decade thanks to those that have willingly and openly shared their experiences – both good and bad – with regard to hospital and field-based outbreaks of infectious diseases and subsequent mitigation efforts. In veterinary hospitals, infection control is often not considered until after individual patient care is addressed and thus prevention of infectious disease transmission can become a secondary activity relative to the treatment of individual horses and a tertiary activity relative to the care of the larger hospital population. Thus infection control has often been largely reactive rather than proactive in many equine facilities. Control efforts are sometimes hurriedly implemented after a disease outbreak is well underway, rather than being used to prevent sporadic cases from escalating into an outbreak. It is clear that outbreaks of infectious disease can occur with alarming frequency, even in highly controlled environments such as veterinary teaching hospitals. A survey of personnel responsible for infection control at 38 American Veterinary Medical Association (AVMA) accredited veterinary teaching hospitals found that 82% had identified at least one outbreak of hospital-associated disease in the previous 5 years with 32% reporting outbreaks so significant that hospital closure was utilised to aid in mitigation efforts [1]. Outbreaks are undoubtedly under-reported in the scientific literature but a variety of organisms have been previously documented as causes of epidemic disease in equine hospitals, including Salmonella enterica [2–5], methicillin-resistant Staphylococcus aureus (MRSA) [6–8], equine herpesvirus type 1 [9–11] and Cryptosporidium [12]. However, equine infectious diseases are not solely associated with veterinary hospitals. The last decade has seen the epidemic spread of West Nile virus in North America, a major equine influenza epidemic in Australia, outbreaks of contagious equine metritis in the USA and South Africa, the re-emergence of piroplasmosis in the USA and dramatically increasing concerns regarding equine herpesvirus myeloencephalopathy and multidrug resistant bacterial pathogens (e.g. MRSA). There are several significant differences with regard to the practice of infection control in equine populations outside of veterinary hospitals (i.e. ‘in the field’). The focus in field situations is likely to be the protection of a relatively healthy population of horses from disease incursion, rather than protection of hospitalised patients with varying degrees of compromised health. The differences are similar to those between protection of public health in the community and infection control in human hospitals. Infection control in the field has often focused heavily on vaccination; however, effective vaccines cannot fully protect all horses as vaccines are not available for many diseases and vaccination cannot be used to control emerging diseases. A fundamental shift in the mindset of clinicians and horse owners must occur whereby vaccination is considered a last line of defence and overall infection prevention emphasises implementation of other control measures. This is particularly critical in large, transient horse populations that gather for specific events due to the potential for serious and widespread repercussions when these populations disperse, as was seen following the National Cutting Horse Association Western National Championship in Ogden, Utah, in May 2011. It is likely that exposure to a single horse shedding equine herpesvirus-1 (EHV-1) at this event resulted in over 165 horses developing clinical disease that was known or suspected to be caused by EHV-1 and at least 13 of these horses were subjected to euthanasia. The outbreak spanned at least 10 western US states and 2 Canadian provinces ([13], P.S. Morley, personal communication 2012). Clearly infectious diseases have a tremendous impact on equine populations and efforts to control and prevent spread are critical to the well-being of individual horses and horse populations. The Dorothy Russell Havemeyer Foundation Inc. (http://www.havemeyerfoundation. org) is a private foundation that supports scientific efforts to improve the health and welfare of horses. To this end, the foundation conducts workshops in a variety of different subject areas, including the control of infectious diseases. The most recent Havemeyer workshop conducted on infection control in equine populations was held in September 2010, bringing together a diverse group of internationally recognised experts in fields related to infection control. The overarching goal of the workshop was to advance the discipline by providing guidance and inspiration to those currently involved in equine infection control and insight to those who may still be on its periphery. More specifically, the objective of this workshop was to identify the most urgent and critical priorities in equine infection control so that these might be targeted for research and resource development. In this report, we summarise the consensus opinions, major ideas and recommendations developed during the workshop. In working to summarise the discussion and major conclusions of this workshop, several common themes became apparent that were deemed essential to the future progress of the discipline of infection control. Specifically, these included ethical obligations and standards of practice regarding infection control, improvements and standardisation for surveillance methods, developing better education and training programmes, standardisation and development of new diagnostic tests for important contagious pathogens, objectively quantifying the costs and benefits of infection control programmes, expanding knowledge necessary for design of control programmes for important contagious pathogens, developing and promoting multicentre studies and promoting judicious antimicrobial use practices. Approaches that can be used for development of infection control programmes (the ‘how to’ of infection control) were discussed in previous Havemeyer workshops and have been reviewed in detail elsewhere [14–17]. Issues regarding the detection and control of specific agents were discussed and were used as examples during the meeting but the focus of this document is on the future needs of infection control in a broader context, not in relation to specific diseases.

Comparison of cytokine responses between dogs with sepsis and dogs with immune-mediated hemolytic anemia.

Cytokine abnormalities have been described previously in dogs with varied immune mediated and inflammatory conditions such as IMHA and sepsis. The purpose of this study was to establish references ranges for cytokine levels in dogs and to compare cytokine levels in normal dogs and dogs with two common inflammatory diseases (sepsis and IMHA). We hypothesized that cytokine response profiles in dogs with sepsis would be significantly different from those in dogs with IMHA due to the very different etiologies of the two diseases. Concentrations of 14 different cytokines in serum were measured and values grouped according to cytokine function. Serum from clinically normal dogs was used to establish cytokine concentration reference ranges. Rank values for each of the 4 cytokine groups were then compared statistically between healthy control, septic and IMHA dogs. This analysis revealed differences in cytokine groups between dogs with sepsis and IMHA when compared to healthy control dogs but no difference between dogs with either of these conditions. In conclustion, dogs in the early stage of sepsis and IMHA have similar circulating cytokines despite different etiologies suggesting activation of common immunologic pathways. This may have implications for immunotherapy of immune mediated diseases in dogs of varying etiology.

Concentrations of serum amyloid A and plasma fibrinogen in horses undergoing emergency abdominal surgery

Objective To compare the perioperative response of serum amyloid A (SAA) to fibrinogen in horses requiring exploratory celiotomy for colic and to determine if SAA could be used to predict complications and outcome. Design Prospective observational clinical study. Setting University teaching hospital. Animals Eighteen horses undergoing exploratory celiotomy for colic. Inclusion criteria for the study included survival and anesthetic recovery from exploratory celiotomy, no history of surgery within the past year. Interventions Blood was obtained via jugular venipuncture before surgery (time 0) and at 24, 48, 72, and 96 hours after recovery from anesthesia. Measurements and Main Results Quantitative and semiquantitative fibrinogen, SAA, total nucleated cell counts, and total protein were evaluated at each time point. Multivariable linear regression was used to assess differences at each time point and after grouping horses according to duration of colic prior to surgery, strangulating surgical lesion or not, presence of systemic inflammatory response syndrome (SIRS) on admission, and postsurgical complications. Significant (P < 0.05) increases in SAA concentrations occurred in all cases after surgery compared to fibrinogen concentration, which only demonstrated a mild, clinically insignificant increase postsurgery. SAA concentrations were also significantly increased (P < 0.05) in cases identified with SIRS prior to surgery and postoperatively at 48 (P = 0.05) and 72 hours (P = 0.02) in horses that developed complications. Conclusions Measurement of SAA is a more sensitive indicator of inflammation than fibrinogen in the perioperative period of horses requiring exploratory celiotomy for colic. Serial measurement of SAA at 48, 72, and 96 hours after surgery may be helpful to determine risk of complications and guide postoperative management. Measurement of SAA on admission also allows for quantification of SIRS when it is detected clinically.OBJECTIVE To compare the perioperative response of serum amyloid A (SAA) to fibrinogen in horses requiring exploratory celiotomy for colic and to determine if SAA could be used to predict complications and outcome. DESIGN Prospective observational clinical study. SETTING University teaching hospital. ANIMALS Eighteen horses undergoing exploratory celiotomy for colic. Inclusion criteria for the study included survival and anesthetic recovery from exploratory celiotomy, no history of surgery within the past year. INTERVENTIONS Blood was obtained via jugular venipuncture before surgery (time 0) and at 24, 48, 72, and 96 hours after recovery from anesthesia. MEASUREMENTS AND MAIN RESULTS Quantitative and semiquantitative fibrinogen, SAA, total nucleated cell counts, and total protein were evaluated at each time point. Multivariable linear regression was used to assess differences at each time point and after grouping horses according to duration of colic prior to surgery, strangulating surgical lesion or not, presence of systemic inflammatory response syndrome (SIRS) on admission, and postsurgical complications. Significant (P < 0.05) increases in SAA concentrations occurred in all cases after surgery compared to fibrinogen concentration, which only demonstrated a mild, clinically insignificant increase postsurgery. SAA concentrations were also significantly increased (P < 0.05) in cases identified with SIRS prior to surgery and postoperatively at 48 (P = 0.05) and 72 hours (P = 0.02) in horses that developed complications. CONCLUSIONS Measurement of SAA is a more sensitive indicator of inflammation than fibrinogen in the perioperative period of horses requiring exploratory celiotomy for colic. Serial measurement of SAA at 48, 72, and 96 hours after surgery may be helpful to determine risk of complications and guide postoperative management. Measurement of SAA on admission also allows for quantification of SIRS when it is detected clinically.

Rapid Salmonella detection in experimentally inoculated equine faecal and veterinary hospital environmental samples using commercially available lateral flow immunoassays

REASONS FOR PERFORMING STUDY Salmonella enterica is the most commonly reported cause of outbreaks of nosocomial infections in large animal veterinary teaching hospitals and the closure of equine hospitals. Rapid detection may facilitate effective control practices in equine populations. Shipping and laboratory testing typically require ≥48 h to obtain results. Lateral flow immunoassays developed for use in food-safety microbiology provide an alternative that has not been evaluated for use with faeces or environmental samples. OBJECTIVES We aimed to identify enrichment methods that would allow commercially available rapid Salmonella detection systems (lateral flow immunoassays) to be used in clinical practice with equine faecal and environmental samples, providing test results in 18-24 h. STUDY DESIGN In vitro experiment. METHODS Equine faecal and environmental samples were inoculated with known quantities of S. enterica serotype Typhimurium and cultured using 2 different enrichment techniques for faeces and 4 enrichment techniques for environmental samples. Samples were tested blindly using 2 different lateral flow immunoassays and plated on agar media for confirmatory testing. RESULTS In general, commercial lateral flow immunoassays resulted in fewer false-negative test results with enrichment of 1 g faecal samples in tetrathionate for 18 h, while all environmental sample enrichment techniques resulted in similar detection rates. The limit of detection from spiked samples, ∼4 colony-forming units/g, was similar for all methods evaluated. CONCLUSIONS The lateral flow immunoassays evaluated could reliably detect S. enterica within 18 h, indicating that they may be useful for rapid point-of-care testing in equine practice applications. Additional evaluation is needed using samples from naturally infected cases and the environment to gain an accurate estimate of test sensitivity and specificity and to substantiate further the true value of these tests in clinical practice.

Comparison of two sampling and culture systems for detection of Salmonella enterica in the environment of a large animal hospital

REASONS FOR PERFORMING STUDY Nosocomial salmonellosis is an important problem in veterinary hospitals that treat horses and other large animals. Detection and mitigation of outbreaks and prevention of healthcare-associated infections often require detection of Salmonella enterica in the hospital environment. OBJECTIVES To compare 2 previously published methods for detecting environmental contamination with S. enterica in a large animal veterinary teaching hospital. STUDY DESIGN Hospital-based comparison of environmental sampling techniques. METHODS A total of 100 pairs of environmental samples were collected from stalls used to house large animal cases (horses, cows or New World camelids) that were confirmed to be shedding S. enterica by faecal culture. Stalls were cleaned and disinfected prior to sampling, and the same areas within each stall were sampled for the paired samples. One method of detection used sterile, premoistened sponges that were cultured using thioglycolate enrichment before plating on XLT-4 agar. The other method used electrostatic wipes that were cultured using buffered peptone water, tetrathionate and Rappaport-Vassiliadis R10 broths before plating on XLT-4 agar. RESULTS Salmonella enterica was recovered from 14% of samples processed using the electrostatic wipe sampling and culture procedure, whereas S. enterica was recovered from only 4% of samples processed using the sponge sampling and culture procedure. There was test agreement for 85 pairs of culture-negative samples and 3 pairs of culture-positive samples. However, the remaining 12 pairs of samples with discordant results created significant disagreement between the 2 detection methods (P<0.01). CONCLUSIONS Persistence of Salmonella in the environment of veterinary hospitals can occur even with rigorous cleaning and disinfection. Use of sensitive methods for detection of environmental contamination is critical when detecting and mitigating this problem in veterinary hospitals. These results suggest that the electrostatic wipe sampling and culture method was more sensitive than the sponge sampling and culture method.

Use of Sentinel Chickens to Evaluate the Effectiveness of Cleaning and Disinfection Procedures in Noncommercial Poultry Operations Infected with Exotic Newcastle Disease Virus

The use of sentinel chickens in establishing the negative status of commercial poultry flocks depopulated due to exotic Newcastle disease (END) is considered to be an economically beneficial process. However, the costs and benefits of using sentinel chickens in noncommercial operations are in question. The objective of this study was to use sentinel chickens to evaluate whether adequate cleaning and disinfection coupled with an appropriate time period without susceptible poultry species on the premises would eliminate END virus from a noncommercial poultry operation and preclude the need for placement of sentinels in previously infected operations before declaring them free of virus. Noncommercial poultry operations were selected from the 2002 to 2003 END outbreak database. Operations included in the study had one or more isolations of END virus (ENDV) from cloacal or oropharyngeal swabs of birds on the premises. A total of 546 birds were placed on 53 premises. All sentinel birds sampled after placements were negative by virus detection methods and serologic tests. Results of this study indicate that time and the application of appropriate cleaning and disinfection procedures will adequately mitigate the risk of viable virus persisting in noncommercial poultry operations. In the future, this information may eliminate the need for sentinel bird placement to ensure virus free status of premises before repopulation, thereby decreasing the costs of END eradication.

Detection of Different Serotypes of Salmonella enterica in Experimentally Inoculated Equine Fecal Samples by Commercially Available Rapid Tests

Background Salmonella enterica can significantly impact management of animal facilities. Comprehensive screening is essential for effective control in high‐risk populations. Availability of reliable point‐of‐care diagnostic tests would facilitate these efforts. Hypothesis/Objectives Compare the ability of commercially available rapid diagnostic assays (2 lateral flow immunoassays [LFIs], DNA hybridization [DNAH], real‐time PCR [qPCR]), and culture to detect common serotypes of S. enterica in feces. Animals n/a. Methods In an experimental study, 112 S. enterica isolates were randomly selected from the 10 most common serotypes recovered at a veterinary hospital. Archived isolates were amplified in broth and standardized inocula (100 colony forming units) were incubated with equine feces in tetrathionate broth (TET). Cultures were tested in a blinded fashion by using LFIs, DNAH, qPCR, and culture. Results The LFIs detected 84% and 67% of isolates, respectively, but reactivity varied among serotypes. Both reacted poorly with serotype Cerro (Group K) isolates, and 1 LFI did not react with any serotype Mbandaka (Group C1) or Montevideo (Group C1) isolates. DNAH detected 94% of isolates, whereas culture and qPCR most reliably detected all serotypes. False‐positive results were obtained for 4 negative controls by using DNAH and 1 negative control by using qPCR, but LFIs and culture had no false‐positive results. Conclusions and Clinical Importance Culture, qPCR, and DNAH were effective in detecting most Salmonella isolates, but have limited application at point‐of‐care settings. LFIs are appealing as point‐of‐care tests because of low cost and ease of use, but limited detection of some serotypes needs to be evaluated with samples obtained from naturally infected animals.