Bacterial biofilm formation is one of the main reasons for a negative treatment outcome and a high recurrence rate for many chronic infections in humans. The optimal way to study both the biofilm forming bacteria and the host response simultaneously is by using discriminative, reliable, and reproducible animal models of the infections. In this review, the advantages of in vivo studies are compared to in vitro studies of biofilm formation in infectious diseases. The pig is the animal of choice when developing and applying large animal models of infectious diseases due to its similarity of anatomy, physiology, and immune system to humans. Furthermore, conventional pigs spontaneously develop many of the same chronic bacterial infections as seen in humans. Therefore, in this review porcine models of five different infectious diseases all associated with biofilm formation and chronicity in humans are described. The infectious diseases are: chronic wounds, endocarditis, pyelonephritis, hematogenous osteomyelitis, and implant-associated osteomyelitis (IAO).

The assessment of the age of bruises inflicted on livestock is an important component of veterinary forensic pathology investigations. However, the sampling site within a bruise, the anatomical location and the mass and speed of the object inflicting the blunt trauma might influence the intensity of the inflammatory reaction. In the present study, the variation of the inflammatory reaction within and along experimental porcine bruises was evaluated in order to determine the optimal sampling site. Moreover, we evaluated if a combination of histological characteristics and gene expression signatures was able to differentiate bruises according to anatomical location, age of bruises and the speed and mass of the object used to cause the impact. Twelve experimental slaughter pigs were anesthetized, and on each animal four blunt traumas were inflicted on the back using either a plastic tube or an iron bar, respectively. The pigs were euthanized at 2, 5 or 8 h after infliction. Following gross examination, skin and underlying muscle tissue were sampled from the center and both ends of bruises and evaluated histologically. Subcutaneous fat tissue from the center of the bruises was sampled for quantitative real-time polymerase chain reaction to evaluate mRNA expression of 13 selected genes. Uninjured tissue was sampled from the right thigh of all pigs and served as control tissue. The amount of tissue damage and the intensity of the inflammatory reaction in bruises depended on the sampling site within and along a bruise, the anatomical location and the age of the bruise. The optimal site for sampling, i.e. the most pronounced inflammatory reaction, was at the center of the bruises where the plastic tube or iron bar first struck the skin. Moreover, bruises inflicted in areas with a thin layer of subcutaneous fat tissue showed more damage and inflammation in the underlying muscle tissue compared to bruises inflicted in areas with a thicker layer of subcutaneous fat tissue. In addition, hemorrhage in the muscle tissue was more likely present when bruises were inflicted with an iron bar compared to a plastic tube. Combining histology and mRNA expression of the 13 genes showed that the age of bruises could be determined with a precision of ±2.04 h. Moreover, the age of bruises could be determined with a precision of ±1.84 h based solely on mRNA expression of a selection of four genes.

Age estimation is a crucial part of the forensic investigation of bruises in livestock pigs [1], [2], [3]. Currently, age estimations are based on histological evaluation of the lesions in the skin and underlying muscle tissue [2]. However, the intensity of inflammation and tissue damage depends not only on the age of bruises but also on sampling site, anatomical location and the speed, mass and force used to inflict the lesions [1], [4], [5].Twelve experimental slaughter pigs were anesthetized and on each animal, four blunt traumas were inflicted on the back (area of impact Nos. 1–4). The pigs were euthanized at 2, 5 or 8 h after infliction. Skin and underlying muscle tissue were sampled from the center (B) and both ends of bruises (A, C) and evaluated histologically. Descriptive statistics were performed on the data obtained and presented in figures and tables. Differences (odds ratios) between sampling sites (A, B and C), object used to inflict bruises (plastic tube or iron bar), anatomical location (area of impact Nos. 1–4) and bruise age (2, 5 and 8 h) were evaluated using the GENMOD procedure in SAS Enterprise Guide 7.1 and presented in tables. In addition, the agreements (estimated as Cohen׳s kappa) between two observers evaluating the histological parameters were calculated and presented. Data have been further analyzed and discussed in a recent paper [1]

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