Submitted by: Patricia Shea, DVM
J Vet Intern Med 2020;34:227–231. DOI: 10.1111/jvim.15674
Amoxicillin and amoxicillin-clavulanate resistance in urinary Escherichia coli antibiograms of cats and dogs from the midwestern United States.
KuKanich K, Lubbers B, Salgado B.
Responsible antimicrobial stewardship in both the human and veterinary fields is now a scientific and moral imperative discussed frequently in professional and public media. In the last several years, a number of human and veterinary professional organizations and working groups have published guidelines advocating conservative use of antimicrobials in common disease states, such as respiratory and urinary tract infections. In particular, the International Society for Companion Animal Infectious Diseases (ISCAID) published its most recent guidelines for the treatment of urinary tract infections (UTIs) in dogs and cats less than one year ago.
In many cases, results of a urinalysis and the presence of clinical signs of a UTI in a companion animal patient may dictate initiation of antibiotic therapy, either prior to or without a urine antimicrobial culture and antibiotic sensitivity testing. Making a rational, evidence-based empirical choice of an appropriate antimicrobial in these situations can improve patient comfort, relieve client frustration, and also decrease the risk of infection ascending into or exacerbating in the upper urinary tract. This is a situation in which an antibiogram, which lists the percentage of a bacterial isolate susceptible to a particular antimicrobial drug, can be useful in planning treatment of a UTI.
Escherichia coli is one of the most common uropathogens in companion animals. In this study of E. coli isolates cultured from the urine of 143 cats and 640 dogs seen in private practice (n = 448) and university practice (n = 335) in the midwestern United States between 2013 and 2017, antibiograms for 10 common antimicrobial agents were reviewed retrospectively. Antibiograms were created from the urine culture and sensitivity data. Sixty-two (43%) of the E. coli isolates from cats came from university practice, while 81 (57%) came from cats seen in private practice.
Only the first culture for a calendar year for an individual cat or dog was used in developing the antibiogram. Because this was a retrospective study, data regarding previous antimicrobial therapy or comorbidities in many individual patients included in the study were not consistently available. Also, there was no information regarding urine collection method, and no consistent time established between urine collection and plating for culture. E. coli-positive samples representing subclinical bacteriuria were probably also included in the study, as there was no consideration of bacterial load (colony forming units) in the sample.
Antibiotics included in the antibiograms for both species were amoxicillin/clavulanate, ampicillin (a surrogate for amoxicillin), cefovecin, cefpodoxime, cephalexin, enrofloxacin, marbofloxacin, orbifloxacin, pradofloxacin, and trimethoprim/sulfamethoxazole. Breakpoints in minimal inhibitory concentration for each antibiotic in each species associated with susceptibility, intermediate susceptibility, and resistance were obtained from references in the veterinary medical literature. In creating the antibiograms, isolates reported as having intermediate susceptibility to an agent were not considered as susceptible at all.
In contrast to the E. coli isolates from dogs, all of the E. coli isolated from cat urine were found to be significantly resistant to ampicillin, amoxicillin, and amoxicillin-clavulanate. These agents are recommended as first-line antimicrobials for UTI in dogs and cats by the most recent (2019) ISCAID guidelines. However, the authors caution that this is not a reason to avoid prescribing these medications in cats with UTI, but may indicate the need to re-evaluate the breakpoint used to determine bacterial sensitivity to these antibiotics in cats.
In dogs, the breakpoint for sensitivity to these beta-lactams is < 8 µg/mL, while in cats this breakpoint is set at < 0.25 µg/mL. Because concentrations for amoxicillin and amoxicillin-clavulanate in feline urine have not been reported, the breakpoints for susceptibility to these antimicrobials are determined from plasma drug concentrations, and are conservative. The susceptibility breakpoints for amoxicillin and amoxicillin-clavulante in canine urine are UTI-specific, based on urine concentration data for these drugs; similar information needs to be determined for feline urine samples, so that a UTI-specific breakpoint for these two antimicrobials is available for cats.
If the feline UTI-specific breakpoint is less conservative than that determined from plasma drug concentrations for amoxicillin and amoxicillin-clavulanate, then more E. coli isolates from cat urine would be reported as susceptible to these affordable, recommended first-line agents. If the canine UTI-specific breakpoint of < 8 µg/mL is applied to the feline samples, the percentage of isolates from these samples reported as susceptible to amoxicillin and amoxicillin-clavulanate would be 89% and 99%, respectively.
Over 90% of the E. coli isolates from feline urine were susceptible to all of the other antibiotics tested; <6% of the isolates from feline urine demonstrated resistance to any antimicrobial agent other than amoxicillin or amoxicillin-clavulanate. The findings in this study are regional, however, and may not apply to E. coli isolates from cats and dogs in other parts of the U.S. or the world. Also, whether or not bacterial isolates come from patients with or without azotemia, or from clinical UTIs or subclinical bacteriuria, may influence antibiogram results and their utility in individual patients.
Scientific Reports 2019;9:19128. DOI: 10.1038/s41598-019-55693-8
Facial expressions of pain in cats: the development and validation of a feline grimace scale.
Evangelista MC, Watanabe R, et al.
The use of facial movement to express pain and suffering, as well as internal emotional states and the ability to recognize this expression in conspecifics, is a well-known part of human heritage and experience. Facial expressions of pain in other species are often much more inscrutable to human caregivers. Therefore, grimace scales have been developed for the evaluation of pain based on facial expression in rats, mice, ferrets, horses, sheep, lambs, piglets, rabbits, and also human infants. Cats are masters at concealing their pain and discomfort, and often do not receive the pain management they need and deserve. Only recently have validated, behavior-based feline pain assessment tools become available.
The purpose of this prospective, case-control study of 35 client-owned and 20 control cats was to develop and validate a feline grimace scale (FGS) to detect naturally occurring acute pain, such as that of diseases causing somatic or visceral pain. Facial expressions can be objectively evaluated using a facial action coding system (FACS) that measures individual movements of the face, called action units (AUs) involved in producing a facial expression. Although orbital tightening and ear flattening are common AUs in all species, other AUs are different. Therefore, the development of species-specific grimace scales is essential.
Cats enrolled in the study were video-recorded in their cages. The painful cats, who had been admitted to the emergency and critical care unit of a veterinary teaching hospital, received analgesic treatment after being video-recorded undisturbed. All animals were video-recorded an hour after the painful cats received the analgesic. Feline patients who had diseases that could affect their facial expressions, such as head trauma or ophthalmic conditions, as well as those requiring emergent care and those who appeared very shy or feral, were excluded from the study. Most of the case cats had diseases that caused them to present with abdominal pain, such as cholangitis, hepatic lipidosis, constipation, urethral obstruction, lymphoma, pancreatitis, inflammatory bowel disease, urolithiasis, idiopathic cystitis, and suspected foreign body.
All of the case cats received a full physical examination, as well as evaluation by one observer with the Glasgow composite measure pain scale for acute pain in cats. Those cats with a score of > 4/16 on this scale were considered painful. A video camera was placed between the cage bars at the level of the eyes, and video recordings of the cats’ facial expressions were made without the presence of human beings in the room. The control cats also received a full physical examination, and were video-recorded twice with a one hour interval between recordings; these cats received no analgesic therapy.
Most of the cats included in the study were domestic shorthairs. Two brachycephalic cats were initially recruited into the study, but were excluded due to poor image quality. Black cats were also excluded due to poor image quality and difficulty in identification of facial landmarks.
Four observers, two PhD candidates and two board-certified anesthesiologists, independently scored all the images of the case and control cats. The AUs indicating pain were defined as follows:
- ear position – tips of the ears pulled apart and rotated outwards;
- orbital tightening – narrowing of the orbital area, or tightly closed eyelids (squinted eyes);
- muzzle tension – flattening and stretching of the muzzle from a round to an elliptical shape;
- whiskers position – forward movement of whiskers rostrally and away from the face;
- head position in relation to the shoulders – head below the shoulder line or tilted down (chin pointed towards the chest).
Linear distance ratios and angles were measured on several facial features:
- ears from tip-to-tip and base-to-base;
- width and height of palpebral fissure;
- muzzle height and width, as well as the angles between the medial border of the ear and the top of the head (medial ear angle), the lateral border of the ear (lateral ear angle), and a line connecting both lateral cutaneous pouches of the ear pinnae.
Each patient image received a single total pain score based on the sum of scores (0-2) from each AU, divided by the maximum possible score (10). The final FGS score was reported on a scale from 0 to 1.
Calculated ratios of ear tips distance/ear base distance, eye height/width, muzzle height/width, medial ear angles, and lateral ear angles differed significantly between case and control groups. The FGS scores were significantly higher (p < 0.001) in the painful group prior to analgesia than in the control group. There was also a very strong correlation between results of the Glasgow composite measure pain scale-feline and the FGS scores. Sex of the animal did not have a significant effect on FGS scores. The FGS also had good inter-rater reliability, and excellent intra-rater reliability. The authors recommend that an FGS score of >0.39/1.0 requires intervention with analgesia, as this represents an optimal balance between sensitivity (90.7%) and specificity (86.6%). This criterion provides the FGS with substantial clinical utility.