E. coli is one of the most common species of bacteria colonizing humans and animals. The singularity of E. coli 's genus and species underestimates its multifaceted nature, which is represented by different strains, each with different combinations of distinct virulence factors. In fact, several E. coli pathotypes, or hybrid strains, may be associated with both subclinical infection and a range of clinical conditions, including enteric, urinary, and systemic infections. E. coli may also express DNA-damaging toxins that could impact cancer development. This review summarizes the different E. coli pathotypes in the context of their history, hosts, clinical signs, epidemiology, and control. The pathotypic characterization of E. coli in the context of disease in different animals, including humans, provides comparative and One Health perspectives that will guide future clinical and research investigations of E. coli infections.

The nematode Trichuris muris has been shown to interact with specific enteric bacteria, but its effects on the composition of its host's microbial community are not fully understood. We hypothesized that Trichuris muris-infected mice would have altered colon microbiota as compared with uninfected mice. Colon histopathology and microbial community structure and composition were examined in mouse models of colitis (C3BirTLR4^–/– IL10^–/– and C3H/HeJ TLR4^–/– IL10^+/+ mice) with and without T. muris infection, in uninfected C3BirIL10^–/– mice with and without spontaneous colitis, and in normal C3H/ HeJ mice. T. muris-infected mice developed colon lesions that were more severe than those seen in IL10-deficient mice. Ap- proximately 80% of infected IL10^–/– mice had colon neutrophilic exudates, and some had extraintestinal worms and bacteria. The composition and structure of proximal colon microbiota were assessed by using terminal restriction fragment length polymorphism analysis targeting the bacterial 16S rRNA gene. Colon microbiota in C3BirIL10^–/– and C3H/HeJ mice differed both qualitatively and quantitatively. Trichuris infection significantly altered the relative abundance of individual operational taxonomic units [OTU] but not the composition (presence or absence of OTU) of colon microbiota in the 2 mouse genotypes. When C3BirIL10^–/– and C3H/HeJ mouse OTU were considered separately, Trichuris was found to affect the microbiota of C3BirIL10^–/– mice but not of C3H/HeJ mice. Even though 34 of the 75 (45%) C3BirIL10^–/– mice had spontaneous colitis, neither qualitative nor quantitative differences were detected in microbiota between colitic or noncolitic C3BirIL10^–/– mice or noncolitic C3H/HeJ mice. Therefore, Trichuris-infected mice developed distinct microbial communities that were influenced by host background genes; these alterations cannot be attributed solely to colonic inflammation.

With the alarming increase in heart disease and heart failure, the need for appropriate and ethical animal models of cardiac dysfunction continues to grow. Currently, many animal models of cardiomyopathy require either invasive procedures or genetic manipulation, both of which require extensive expertise, time, and cost. Serendipitous findings at our institution revealed a possible correlation between sulfadiazine-trimethoprim (SDZ-TMP) medicated diet and the development of cardiomyopathy in IcrTac:ICR mice. We hypothesized that mice fed SDZ-TMP medicated diet continuously for 3 to 6 mo would develop cardiomyocyte degeneration and fibrosis, eventually leading to dilated cardiomyopathy. A total of 44 mice (22 Hsd:ICR (CD1) and 22 Tac:SW) were enrolled in the study. Half of these 44 mice were fed standard rodent diet and the other half were fed SDZ-TMP medicated diet. Baseline samples, including weights, CBCs, select biochemistry parameters, and echocardiography were performed prior to the start of either diet. Weights were obtained monthly and all other parameters were measured at least once during the study, and again at its conclusion. After 42 wk, mice were euthanized, and heart, lung and bone marrow tissue were submitted for histopathologic evaluation. Histologically, hearts were scored for the degree of degeneration, fibrosis, inflammation, and vacuolation. The data showed that SDZ-TMP did not have a significant effect on cardiac function, RBC parameters, biochemistry parameters (ALT, AST, calcium, magnesium, creatine kinase, and creatinine), hematopoiesis, or histologic heart scores. In addition, mice fed the SDZ-TMP medicated diet gained less weight over time. In summary, we were unable to reproduce the previous findings and thus could not use this approach to develop a novel model of cardiomyopathy. However, these results indicate that SDZ-TMP medicated diet containing 1,365 ppm of SDZ and 275 ppm of TMP does not appear to have long-term detrimental effects in mice.

Despite the use of Syrian hamsters (Mesocricetus auratus) in research, little is known about the evaluation of pain in this species. This study investigated whether the frequency of certain behaviors, a grimace scale, the treat-take-test proxy indicator, body weight, water consumption, and coat appearance could be monitored as signs of postoperative pain in hamsters in a research setting. Animals underwent no manipulation, anesthesia only or laparotomy under anesthesia. An ethogram was constructed and used to determine the frequencies of pain, active and passive behaviors by in-person and remote videorecording observation methods. The Syrian Hamster Grimace Scale (SHGS) was developed for evaluation of facial expressions before and after the surgery. The treat-take-test assessed whether surgery would affect the animals' motivation to take a high-value food item from a handler. The hypothesis was that behavior frequency, grimace scale, treat-take-test score, body weight, water consumption, and coat appearance would change from baseline in the surgery group but not in the no-intervention and anesthesia-only groups. At several time points, pain and passive behaviors were higher than during baseline in the surgery group but not the anesthesia-only and no-intervention groups. The SHGS score increased from baseline scores in 3 of the 9 animals studied after surgery. The frequency of pain behaviors and SHGS scores were highly specific but poorly sensitive tools to identify animals with pain. Behaviors in the pain category were exhibited by chiefly, but not solely, animals that underwent the laparotomy. Also, many animals that underwent laparotomy did not show behaviors in the pain category. Treat-take-test scores, body weight, water consumption, and coat appearance did not change from baseline in any of the 3 groups. Overall, the methods we tested for identifying Syrian hamsters experiencing postoperative pain were not effective. More research is needed regarding clinically relevant strategies to assess pain in Syrian hamsters.

Steroid-induced osteonecrosis of the femoral head (SONFH) is a condition documented in humans and animals exposed to chronic steroid administration. The rabbit has become a preferred animal model for investigating the pathogenesis and treatment of SONFH due to its shared femoral vascular anatomy with human patients, relative size of the femoral head, and general fecundity. However, morbidity and mortality are frequent during the steroid induction period, prior to surgical manipulation. These problems are poorly reported and inadequately described in the literature. In this study, we report the clinical, gross, and histopathologic findings of New Zealand white (NZW) rabbits undergoing the steroid induction phase of the SONFH model. Severe weight loss (>30%), lipemia, hypercholesterolemia, hyperglycemia, and elevations in ALT and AST were consistent findings across all rabbits, although these changes did not differentiate asymptomatic rabbits from those that became clinically symptomatic or died. Euthanized and spontaneously deceased rabbits exhibited hepatomegaly, hepatic lipidosis/glycogenosis, and hepatocellular necrosis, in addition to a lipid-rich and proteinaceous thoracic effusion. A subset of rabbits developed opportunistic pulmonary infections with Bordetella bronchiseptica and Escherichia coli and small intestine infections with Lawsonia intracellularis superimposed on hepatic and thoracic disease. Together, these findings allowed us to establish a clinical decision-making flowchart that reduced morbidities and mortalities in a subsequent cohort of SONFH rabbits. Recognition of these model-associated morbidities is critical for providing optimal clinical care during the disease induction phase of SONFH.

This report describes hemochromatosis associated with chronic parenteral iron dextran administration in 2 female olive baboons (Papio anubis). These baboons were enrolled on an experimental protocol that induced and maintained anemia by periodic phlebotomy for use in studying potential treatments for sickle cell anemia. The 2 baboons both presented with clinical signs consistent with iron overload, including decreased appetite, weight loss, elevated liver enzymes, and hepatosplenomegaly. Histopathologic findings supported a morphologic diagnosis of systemic hemosiderosis, as evidenced by the overwhelming presence of iron in the reticuloendothelial system and liver after the application of Prussian blue stain. This finding, combined with the clinical presentation, lead to a final diagnosis of hemochromatosis. This case report suggests that providing anemic patients with chronic parenteral iron supplementation in the absence of iron deficiency can result in iatrogenic iron overload and subsequent systemic toxicity. Furthermore, these subjects may present with hemochromatosis and its associated clinical signs many years after cessation of iron supplementation.