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During the last 10 years the number of porcine models for human bacterial infectious diseases has increased. In the future, this tendency is expected to continue and, therefore, the aim of the present review is to describe guidelines for the development and reporting of these models. The guidelines are based on a review of 122 publications of porcine models for different bacterial infectious diseases in humans. The review demonstrates a substantial lack of information in most papers which hampers reproducibility and continuation of the work that was established in the models. The guidelines describe overall principles related to the inoculum, the animal, the infected animal and the post-mortem characterization that are of crucial importance when porcine models of infectious diseases are developed, validated and reported.

Keywords

infectious diseases pigs animal models

Introduction

The use of pigs as experimental animals is increasing.¹ In the EU 239,089 pigs have been used for experimental purposes during the last 5 years (Figure 1(a)).² The use of pigs as experimental animals has primarily been in the areas of toxicology, metabolism, cancer and xenotransplantation.¹ However, during the last 10 years the number of porcine models for human bacterial infectious diseases has increased, and it is reasonable to assume that many more models will follow in the future (Figure 1(b)).³ Pigs have been used to model the different human bacterial infectious diseases listed in Table 1. The aims of the different models were to study either the efficacy of novel and well-known antimicrobials, prevention and treatment of infection, specific virulence mechanisms of pathogens or the process of inflammation and disease development. The increased popularity of pigs as experimental animals is also reflected in several reviews about the advantages of porcine models in biomedical research.^1,4–6

Figure 1.

(a) Pigs used for biomedical research from 2012–2016 in the EU. Pigs are frequently used as experimental animals in most of the European countries.² (b) Number of publications where pigs have been used to model human bacterial infectious diseases. The colours indicate the target organ system infected in the models. References for all the models can be found in the supplementary material.

Table 1.

Human bacterial infectious diseases modelled in pigs.

Main organ system of the infection	Disease
Respiratory	Pneumonia
	Pneumonia in cystic fibrosis
	Ventilator associated pneumonia
	Tuberculosis
	Whooping cough (acute respiratory infection in infants)
Genital	Chancroid (sexually transmitted genital ulcer)
	Chlamydia in females
Urinary	Pyelonephritis
	Reflux nephropathy
Vascular	Vascular catheter infection
	Aortic graft infection
	Prosthetic vascular graft infection
	Metallic stent placement infection
Eye	Endopthalmitis
Bone	Hematogenous osteomyelitis
	Implant associated osteomyelitis
Skin	Wound infections
Heart	Endocarditis
Gastrointestinal	Gastroenteritis
	Colitis
	Enteritis
	Enterocolitis
	Typhoid fever
Systemic	Acute respiratory distress syndrome
	Sepsis
	Pyemia

Animal models of infections are important tools to study different aspects of infectious diseases in humans because they provide all factors involved in a pathogen–host interaction.⁷ The reason why pigs are preferred as experimental animals is due to their size, anatomy and physiology which are comparable to humans.^4,6 Recently, the complete genome of the domesticated pig was sequenced⁸ and more laboratory reagents specific for porcine tissue have become available.⁹ However, two additional points make pigs especially favourable for modelling of infectious diseases in humans. Firstly, the immune response of pigs is comparable to that of humans as the porcine and human genome show similarity, both structurally and functionally, among immune-related proteins.¹⁰ Furthermore, as in humans, pigs have a large percentage of neutrophilic granulocytes in the peripheral blood.¹¹ Second, porcine models are advantageous due to spontaneous development (naturally-occurring infections) of the same infectious diseases as in humans.³ As an example, the pathogenesis and lesions of spontaneously occurring chronic pressure wounds, endocarditis, pyelonephritis and hematogenous osteomyelitis are comparable to those seen in humans and are also often caused by the same bacteria.³ Homologous models (same aetiology, pathogenesis and symptoms) are described as the most ideal for capturing the complex nature of diseases.¹² Beside all the advantages of using porcine models in translational research, it is also important to consider the differences between pigs and humans. As an example, there are some major anatomical differences in the gastrointestinal tract. In pigs the caecum, which has a remarkably larger size, and colon are arranged in a series of centrifugal and centripetal coils differing from those in humans.⁴ In a review by Swindle et al. the anatomical similarities and dissimilarities between pigs and humans are described in detail for all organ systems.⁴ Another difference, which is very important for bacterial challenge trials is the body temperature. In normal pigs the rectal temperature can vary between 38–40℃ which can make it difficult to define the occurrence of pyrexia.¹³

For scientific, ethical and economic reasons, animal experiments should be appropriately designed, correctly analysed and clearly described. However, it has been documented recently that there is a lack of detail in the way research using animal models is reported.¹⁴ Furthermore, several authors have stated the need for more efficiency in translational medicine and called for international guidelines to set higher standards for the validity of animal models in different disciplines.¹⁵ Therefore, the aim of this review was to investigate the details of the reported data from existing porcine models of bacterial infectious diseases in humans. Furthermore, the aim was also to describe guidelines of overall principles that are of crucial importance when porcine models are developed, validated and reported.

Material and methods

Data collection

Papers were collected by a comprehensive search of Medline, Web of Science and Google Scholar. The aim of the search was to find papers in which pigs were used to model bacterial infections in humans. Prior to the search, it was decided to allocate all papers into groups based on the target organ-system of the infection. The following target-organ systems were defined: systemic (sepsis models); respiratory; urinary; brain; gastrointestinal; genital; eye; heart; skin; bone; vascular (graft/catheter). Thereafter, Group A search words were combined with Group B search words in the databases:

Group A search words:

Porcine model OR pig model OR swine model NOT guinea, human OR man;

Infection OR infectious OR bacteria OR micro-organism OR pathogen OR disease NOT virus.

Group B search words:

Lung OR pneumonia OR respiratory OR airway;

Kidney OR nephritis OR urinary OR cystitis;

Brain OR CNS OR neuro OR encephalitis OR meningitis;

Gastro OR intestine OR enteritis OR colitis;

Genital OR reproductive;

Sepsis OR pyemia OR bacteraemia OR bacteremia;

Graft OR catheter;

Eye OR orbital OR endophthal OR retin OR uve OR kerat;

Bone OR bone infection OR osteomyelitis;

Heart OR endocarditis;

Skin OR wound.

The following data were extracted from all included publications: bacterial strain used for inoculation (including origin); inoculation dose; inoculation volume; animal data (age, breed, sex, immune status, number); housing data (acclimatization period, diet, individual/group housing, isolation stable, specification of housing condition); inoculation route; anaesthesia during inoculation; surgery during inoculation; methods used to monitor local and systemic infection in alive animals; pain management; time frame; full-body necropsy; occurrence of secondary systemic bacterial (inoculum) spread; methods used to characterize local and systemic inflammation post mortem; methods used to identify the inoculated bacteria post mortem. Finally, the impact of each study was evaluated by registration of the number of citations (with and without self-citation) in Scopus. The extracted data and all references can be found as supplementary material.

Results and discussion

In total, 122 different papers were collected for the present review (Figure 1(b)). All the models followed the same structure: a pathogen was introduced into an animal, which then became infected for a fixed period of time followed by post-mortem analyses. Therefore, the results were organized in four sections dealing with the inoculum, the pig, the infected pig and post-mortem characterization (Figure 2).

Figure 2.

Guidelines for development and reporting of porcine models for human bacterial infectious diseases. The inoculum, the pig, the infected pig and the post-mortem characterization must be well considered and reported to allow reproduction. The bullets listed in the figure should be mandatory in all papers reporting porcine models of human bacterial infections.

The inoculum

The inoculum consists of an exact dose of a specific bacterial strain suspended in a fixed volume (Figure 2).^16–20 The different bacterial strains used for inoculation of pigs for human bacterial infections are shown in Figure 3(a). The most commonly used gram positive and gram negative bacterial species, regardless of target organ system, were Staphylococcus aureus and Escherichia coli, respectively. Staphylococcus aureus was primarily used for establishing catheter,²¹ bone,²² heart,²³ skin²⁴ and systemic infections²⁵ and E. coli for induction of urinary,¹⁷ respiratory,²⁶ gastrointestinal²⁷ and systemic infections.²⁸ The bacterial strains most often originated from humans (48%) or pigs (35%).^20,29 For E. coli, there was no difference in inoculation dose among human and porcine strains. For S. aureus there was a tendency towards a lower inoculation dose when the strain originated from pigs.^23,30

Figure 3.

(a) Bacterial species used in porcine models of human infections. (b) Inoculation doses (colony forming units; CFU) used in porcine models of human bacterial infections with respect to target organ system for the infection. Doses reported as an interval – for example, 10^2–4 – have been reported as 10², 10³ and 10⁴. In studies where multiple doses of the same 10 factor was used, only one dose was reported. (c) Animal number, (d) age and (e) time-frame reported in porcine models of human bacterial infectious diseases. The highest inoculation time for each study was chosen if multiple time points of euthanasia were described. The colours indicate the target organ system in the models.

An optimal inoculum should result in the development of infection in all inoculated animals. However, this was not obtained in all studies.³ In order to find the optimal inoculum dose, a dose-response study can be performed.³¹ In 80% of the papers reviewed, the inoculation dose was between 10⁶ and 10⁹ CFU (colony forming units) (Figure 3(b)). However, for the bone, eye, respiratory system and grafts the most commonly used doses (median) were lower than 10⁶ CFU (Figure 3(b)). Very high bacterial doses might not mimic the clinical situation of, for example, surgical contamination of bone implants and colonization of catheters with skin commensals.³² Most often the inoculation dose was reported as CFU ml⁻¹ followed by the number of ml injected or as CFU in a fixed volume. However, in many of the models the inoculation volume was not registered (Table 2). In a study performed by Soerensen et al. in 2012 it was demonstrated that the volume – that is, the same dose of a specific bacterial strain suspended in two different volumes – had a major impact on the inflammatory response seen in a sepsis model.²⁰

Table 2.

Overview of ‘not reported data’ in 122 publications describing porcine models of human bacterial infectious diseases.

Category	Data extracted	Percent (rounded up) of publications without information on the data
The inoculum
	Origin of the bacterial strain	17% (21/122)
	Inoculation dose	11% (13/122)
	Inoculation volume	32% (40/122)
The pig
	Breed of the used pigs	29% (36/122)
	Number of pigs	5% (6/122)
	Age of the used pigs	38% (46/122)
	Sex of the used pigs	29% (36/122)
The infected pig
	Pain management	65% (80/122)
	Local infection monitoring	17% (21/122)
	Systemic infection monitoring	18% (22/122)
	Time from inoculation to euthanization	2% (3/122)
Post mortem
	Characterization of local pathology (articles for sepsis not included)	21% (19/90)
	Characterization of systemic pathology	51% (63/122)
	Full necrospy	60% (72/122)
	Identification of inoculated bacteria	31% (38/122)

The pig

Different breeds of farm pigs raised for slaughter and mini-pigs were used in 63% and 7.3% of the reviewed papers, respectively. In the rest of the papers the breed of the pigs was not reported (Table 2). The differences between conventional farm pigs and mini-pigs are primarily related to the growth rate and size at sexual maturity. The growth rate of conventional pigs is high (the body weight of an adult is >200 kg) compared to mini-pigs (the body weight of an adult is 40–80 kg), making mini-pigs a more favourable model for adults.⁴ There are various breeds of both farm pigs and mini-pigs available, and there is a wide variation in their genotype and phenotype which impacts the growth rate, size and body weight. Therefore, it is always important to report the used breed as it may have an influence on, for example, the amounts of drug needed for testing.⁴ The health status of domestic farm breed pigs is variable depending on country, region and farmer management.⁶ Specific pathogen free (SPF) status is a specific term used in swine management ensuring that the animals are free of specific infectious diseases. However, they can still have had previous exposure to a broad range of pathogens. The use of SPF pigs was reported in 23 of the reviewed publications. Besides SPF, other descriptions of immune status included the use of gnobiotic pigs and colostrum-deprived pigs, which were used to model gastrointestinal infections. Usually, one to 20 pigs were used in the reported studies (Figure 3(c)). Only one study reports the use of a power analysis to calculate the sample size.³³ Most of the animals were below 12 weeks of age (Figure 3(d)), despite the fact that most of the modelled infectious diseases are seen in adult patients. However, in some studies pigs of 0–2 weeks of age were used to replicate infectious diseases of the respiratory, intestinal and urinary systems which only occur in infants.^34–38 Unfortunately, the age of the pigs was often not reported (Table 2); the age of the pig might influence the immune response towards an infection. In a porcine model of implant-associated osteomyelitis no difference was observed between the use of 12 and 32 week old pigs, respectively.³⁹ However, in a porcine model of pneumonia the possibility of inducing infection with Bordetella pertussis was significantly lower in 4–5 week old pigs compared to newborns.⁴⁰ In the present review, 38% of the pigs were females, 16% were males and in 46% the sex of the pigs was not registered. Due to the physiological differences between female and male pigs, it is relevant to report the sex in order to secure that a study is 100% reproducible. The optimal inoculation route (getting the inoculum into the pig) should replicate the pathogenesis of the infection seen in humans. Therefore, the inoculation routes often reflect the main target organ (Table 3). However, different anatomical inoculation points for the same pathogenesis can result in diverse results; for example, in a model of female genital chlamydia infection a longer infection period was seen for intrauterine inoculation compared to vaginal inoculation.⁴¹ The intravenous inoculation route has been widely used to model many different kinds of infectious diseases; for example, graft infections,⁴² pneumonia,⁴³ osteomyelitis,¹⁸ endocarditis²³ and sepsis.²⁰ However, it might be difficult to control and contain an infection using the intravenous inoculation route.¹⁸ The present review demonstrated that two-thirds of all pigs used to model human bacterial infections are anaesthetized or sedated during the inoculation procedure. Furthermore, in 50% of the models some kind of surgery (defined by cutting) was performed prior to inoculation.

Table 3.

Inoculation routes used in order to establish porcine models of human bacterial infectious diseases. It is registered if the inoculation routes demand anaesthesia and surgery (defined by cutting).

Main organ system for the infection	Reported inoculation routes	Anaesthesia	Surgery
Respiratory	Intra-pulmonary	yes	yes/no
	Oropharyngeal	yes	yes
	Transthoracic	yes	no
	Tonsil deposition	yes	no
	Intravenous	yes	no
	Intra-tracheal	yes	no
Genital	Transcervical	yes	yes
	Intra-uterine	yes	yes
	Intra-vaginal	yes	no
Urinary	Directly in the renal pelvis	yes	yes
	Intra-vesical	yes	yes
Vascular	Infected graft/ catheter	yes	yes
	Intravenous	yes	yes
	Intra-arterial	yes	yes
Eye	Intra-viterous	yes	yes
Bone	Intravenous	yes	yes/no
	Intra-arterial	yes	yes
	Traumatic	yes	yes
Skin	Topical	yes	yes
Heart	Intravenous	yes/no	yes/no
	Subcutaneous	no	no
Gastrointestinal	Peroral	no	no
	Intra-gastrical	no	no
	Intestinal	yes	yes
	Intra-nasal	no	no
Systemic	Intra-bronchial	yes	no
	Intra-pulmonary	yes	yes
	Intravenous	yes/no	yes/no
	Intra-nasal	no	no
	Intra-abdominal	yes	yes
	Intra-peritoneal	yes	yes
	Intestinal	yes	yes

Reporting of housing details was in general found to be very limited. Only 22% of the studies report a period of acclimatization, even though a pre-study stabilization period is recommended for experimental pigs to be used in survival studies.⁶ In 23 of the 122 papers it was mentioned if the animals were housed individually or in groups. Of these 23 studies, group housing was reported in 12 papers and the number of pigs housed together ranged from two to six. Swine are social animals and to reduce stress, it is recommended that they have the opportunity to interact with or see other members of their species.⁶ The use of an isolation stable was reported in 13% of the papers included in the present review. Diet details were reported in 25% of the included papers and housing conditions – for example, pen size, flooring, bedding specification, humidity or temperature – were only reported in 11% of the papers.

The infected pig

It is necessary to consider how to monitor and handle the infected pig with regards to disease development. As the models replicate infectious diseases in humans, discomfort and signs of pain can be expected. In 34% of the papers reviewed analgesic treatment was reported during the study period. Analgesic treatment was primarily used in studies of sepsis, bone infections, infections of the respiratory system and catheter/graft associated infections.^20,39,44,45 Both opioids and NSAIDs have been used as analgesic treatments in porcine models of human bacterial infections.^20,45,46 A drawback of NSAIDs is their anti-inflammatory effect, however recently opioids have also been shown to have anti-inflammatory activity.⁴⁷ In a porcine model of osteomyelitis, macroscopic bone lesions with sequester formation have been established despite daily oral NSAID treatment.³⁹ Beside analgesic treatment, diseased pigs should have an increased number of daily inspections and special requirements to minimize their discomfort, such as fluid therapy or oxygen supply, should be established if possible.²⁵ In the 122 papers collected for the present review, the development of a local infection in the main target organ system was monitored by either clinical signs, imaging techniques (e.g. CT and MR scan), fluid and tissue samples and samples taken for microbiological examination. The systemic response to the local infection, or a systemic response due to spread of infection from the main target organ system, was most often monitored by clinical examinations, blood analysis including microbiological culture and urinary analysis. However, the systemic response was only seldom considered in the models (Table 2). Optimally, the infection time or time-frame of the experiment (time from inoculation to euthanization) should reflect the disease stage of interest (e.g. acute or chronic). For all organ systems, except for sepsis, eye, urinary and genital, porcine models with a time frame of more than four weeks have been developed.^43,48–51 However, in 69% of all the models included in this review the time-frame was below two weeks (Figure 3(e)).

Post-mortem characterization

To characterize a porcine bacterial infectious disease model, it is important to focus on both local and systemic signs of infection post mortem.^{16,17,21,23,27,39,41,43,52,53} Local inflammatory lesions will occur in the main target organ and have been characterized by several methods (Figure 4(a)). However, most often macroscopic pathology and histology were applied. The inflammatory lesions should be described and quantified by semi-quantitative scoring systems or objective measurements.^17,39 It is relevant, in all porcine models of bacterial infectious diseases, to include a definition of infection. Not all inoculated animals may develop an infection, or the same grade of infection. Therefore, it is important to have criteria that define if an animal was infected or not.^22,39,54 From the main target organ the local infection can spread either locally into the adjacent tissue or systemically. A local spread will be registered in the description of the lesions pattern of distribution. However, an infection in the main target organ may result in an infective embolus (bacteria and particular material in the blood) which can settle in other organ systems and initiate secondary lesions. This will result in signs of infection, which can interfere with the signs caused by the primary infection of interest.^18,30,52 Therefore, it is always important to look for and describe the occurrence of secondary, embolic infectious lesions. Macroscopic pathology and histology of internal organs (i.e. lungs, kidneys, spleen and liver) were the predominantly used methods to exclude secondary foci of infection (Fig. 4(a)).^{18,19,39,55,56} However, in half of the porcine models reviewed, occurrence of systemic inflammation was not described, and a full necropsy was only reported in 40% of the papers (Table 2). Microbiologically, it is important to look for the inoculated bacteria both locally within lesions and on inserted implants/devices and systemically.⁵⁷ In 28% of the publications (sepsis models excluded) the inoculated bacteria were recovered from blood or other organs than the local organ in question, or animals were reported dead due to sepsis. The techniques listed in Figure 4(b) have been used to localize and re-isolate the inoculum post mortem. The lungs of pigs trap blood-borne pathogens due to the presence of specialized pulmonary intravascular macrophages.²⁰ Therefore, lung samples for quantitative microbiology were commonly used to look for a hematogenous spread of the inoculated bacteria.^18,31,56 Culture (by the use of swabs) was frequently used, however, the technique will not identify bacteria located inside the tissue.⁵⁸ Clinically, it has been demonstrated that swabs are less effective compared to biopsies for the diagnosis of infections.⁵⁸ The occurrence of bacterial biofilm formation should be considered in future porcine models of bacterial infections.⁵⁹ Biofilm can be formed both inside tissue and on inserted implants and devices, and biofilm is an important factor in sustaining infections in humans.⁵⁹ During the last decades, it has been realized that bacterial biofilm formation is involved in chronic infections.⁵⁹ Chronic infections are of increasing concern due to their high healthcare burden and, recently, diagnostic and therapeutic guidelines for biofilm infections were developed by ESCMID (European Society of Clinical Microbiology and Infectious Diseases).⁵⁹ The guidelines raised the following question: what research is urgently needed to improve diagnosis and treatment of bacterial biofilm infections? Among others, one of the answers was the development of better animal models that realistically reflect infectious diseases in humans. Biofilm formation can be confirmed by different types of microscopy and sonication of implants.³

Figure 4.

(a) Common methods used to characterize the local (bottom) and systemic (top) inflammatory response post mortem in porcine models of bacterial infectious diseases in humans. (b) Common methods used to isolate the inoculum post mortem in porcine models of bacterial infectious diseases in humans.

Citation impact

The analysed porcine models of bacterial infectious diseases in humans showed citation impact. In total, 88 of the 122 papers included in the present review were registered in Scopus. The mean number of citations for the 88 papers were 29.6 ± SEM 4.48 with self-citation and 22.73 ± SEM 3.617 without self-citation. If the porcine models were grouped by organ system the number of citations, without self-citations, from the highest to the lowest was as follows: urinary 85.5 ± SEM 83.5; respiratory 39.7 ± SEM 15.9; gastrointestinal 31.6 ± SEM 10.72; skin 21.4 ± SEM 5.9; sepsis 20.24 ± SEM 4.723; vascular 17.1 ± SEM 4.478; genital 11 ± SEM 6; heart 6.25 ± SEM 1.1 and bone 4.6 ± SEM 1.7. The 20 most cited porcine models of human bacterial infections were models of sepsis, pneumonia, wounds, graft infections, pyelonephritis and gastroenteritis (Figure 5). These most cited models were developed between 1975 and 2013 and they were cited regularly since publication – that is, the mean number of citations per year since publication = 7 ± SEM 2.6 (6 ± SEM 2.3 without self-citation). The most cited porcine model for human bacterial infections was published in Nature in 2013⁶⁰ and demonstrated pathophysiological aspects of cystic fibrosis and pneumonia: since publication this model has been cited 250 times by other authors.

Figure 5.

The 20 most cited porcine models of bacterial infectious diseases in humans. The models have been regularly cited since publication. The last name of the first author and the year of publication is mentioned on the x-axis. Blue, pyelonephritis model; green, sepsis models; pink, gastroenteritis models; grey, graft model; red, pneumonia models; yellow, wound model.

Guidelines for reporting of porcine models of bacterial infectious diseases in humans

The inoculum

The inoculum must be strictly reported and consist of the bacterial strain, the dose and the volume. The bacterial strain defines the virulence of the inoculum. Therefore, it is recommended to report as many details as possible for the used bacterial strain; for example, human or porcine origin, diseases/outbreaks caused by the strain, severity of disease development, expression of known virulence factors including antimicrobial resistance.

The pig

The breed, number, age and sex of the pigs should always be reported. Consider using mini-pigs if the growth of the pigs is a major drawback for the study or if mature pigs are essential. Report housing conditions. The inoculation route/procedure should reflect the natural pathogenesis which might demand anaesthesia and often also surgery.

The infected pig

Clinical signs of both local and systemic infection/response should be monitored, and it is important to report how the diseased animal is handled; for example, analgesic treatment, humane endpoints, any special requirements relevant for the disease. The time frame of the infection should reflect that of human infections.

Post-mortem characterization

A complete necropsy should be performed in order to disclose both local and systemic infectious lesions. Use blinded semi-quantitative or objective methods to evaluate the lesions. Include a definition of infection. Identify the inoculum and consider the formation of biofilm.

Conclusion

We have demonstrated an increase in the number of porcine models for bacterial infections in humans. Furthermore, we have also demonstrated that the models are regularly cited – that is, they have scientific impact. However, there is a substantial lack of information in most of the papers describing the models and, therefore, it was highly important to develop the present guidelines. It is important to emphasize that reporting of methods and their negative results such as ‘no signs of systemic inflammation were found post mortem’ is also valuable. Only then can one rely on, for example, that a high C-reactive protein response is caused by the local infection and not by a systemic spread of the inoculum. The reported guidelines should hopefully help authors to include all essential information in future publications as this will encourage reproducible, clear, comprehensive, accurate, concise and well-written manuscripts of porcine models for human bacterial infections. The guidelines will also help journal editors to facilitate improvement in the quality and validity of porcine bacterial infectious disease models. Recently, the ARRIVE (Animal Research: Reporting of In-Vivo Experiments) guidelines were developed to improve general design, analysis and reporting of research using animals. These guidelines are now endorsed by many scientific journals. However, the ARRIVE guidelines do not fulfil all the special requirements needed for optimal development and reporting of animal models for bacterial infectious diseases in humans. Application of the present guidelines for porcine models will build on the ARRIVE guidelines and comply with the principles of the 3Rs (replacement, reduction, refinement), as maximum information published for each model will decrease the number of unnecessary animal studies (reduction). Furthermore, reproducible, well-described and characterized animal models will have the least possible negative impact on animal welfare (refinement).

Porcine models of bacterial infections must be discriminative for the disease seen in humans. The optimal discriminative model reflects the aetiology, pathogenesis, distribution and appearance of lesions. Pathology (i.e. the macroscopic and histologic examination of lesions) is fundamental for evaluation of whether the developed lesions are discriminative or not. Therefore, pathology should always be used to characterize porcine models of human bacterial infections.

Supplemental Material

Supplemental material for Guidelines for porcine models of human bacterial infections

Supplemental material for Guidelines for porcine models of human bacterial infections by Louise K Jensen, Nicole L Henriksen and Henrik E Jensen in Laboratory Animals

Footnotes

Declaration of Conflicting Interests

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: This work was supported by a grant from the Danish Research Council (grant number 4005-00035B).

References

Gutierrez

Dicks

Glanzner

et al.

Efficacy of the porcine species in biomedical research. Front Genet 2015; 293: 1–9.

European Commission. Animals used for scientific purposes, http://ec.europa.eu/environment/chemicals/lab_animals/member_states_stats_reports_en.htm (2016, accessed 15 September 2017).

Jensen

Johansen

ASB

Jensen

. Porcine models of biofilm infections with focus on pathomorphology. Front Microbiol 2017; 8: 1–13.

Swindle

Makin

Herron

et al.

Swine as models in biomedical research and toxicology testing. Vet Pathol 2012; 2: 344–356.

Schomberg

Tellez

Meudt

et al.

Miniature swine for preclinical modeling of complexities of human disease for translational scientific discovery and accelerated development of therapies and medical devices. Toxicol Pathol 2016; 3: 299–314.

Swindle

Smith

Laber-Laird

et al.

Swine in biomedical research: management and models. ILAR J 1994; 1: 1–5.

Rouse

Wilson

General methodologies for animal models. In: Zak

Sande

(eds). Handbook of Animal Models of Infection, 1st ed. London: Academic Press, 1999, pp. 9–12.

Swindle

Smith

Laber-Laird

et al.

Swine in biomedical research: management and models. ILAR J 1994; 1: 1–5.

Meurens

Summerfield

Nauwynck

et al.

The pig: a model for human infectious diseases. Trends Microbiol 2012; 1: 50–57.

10.

Dawson

Loveland

Pascal

et al.

Structural and functional annotaion of the porcine immunome. BMC Genomics 2013; 332: 1–16.

11.

Fairbairn

Kapetanovic

Sester

et al.

The mononuclear phagocyte system of the pig as a model for understanding human innate immunity and disease. J Leukoc Biol 2011; 6: 855–871.

12.

Hau

Schapiro

. Handbook of Laboratory Animal Science, Volume II, 3rd ed. Florida: CRC Press, 2011, pp. 1–11.

13.

Pullar

. The rectal temperature in normal and infected pigs. Br Vet J 1949; 105: 437–453.

14.

Kilkenny

Parsons

Kadyszewski

et al.

Survey of the quality of experimental designs: Statistical analysis and reporting of research using animals. PLoS One 2009; 4: 1–11.

15.

Reitmaier

Graichen

Shirazi-Adl

et al.

Separate the sheep from the goats. Use and limitations of large animal models in intervertebral disc research. J Bone Joint Surg 2017; 99: 1–11.

16.

Erneholm

Lorenzen

Bøje

et al.

Genital tract lesions in sexually mature Göttingen minipigs during the initial stages of experimental vaginal infection with Chlamydia trachomatis serovar D. BMC Vet Res 2016; 200: 1–11.

17.

Isling

Aalbæk

Birck

et al.

Host response to porcine strains of Escherichia coli in a novel pyelonephritis model. J Comp Pathol 2011; 144: 257–268.

18.

Jensen

Nielsen

Agerholm

et al.

A non-traumatic Staphylococcus aureus osteomyelitis model in pigs. In Vivo 2010; 24: 257–264.

19.

Leifsson

Iburg

Jensen

et al.

Intravenous inoculation of Staphylococcus aureus in pigs induces severe sepsis as indicated by increased hypercoagulability and hepatic dysfunction. FEMS Microbiol Lett 2010; 309: 208–216.

20.

Soerensen

Skovgaard

Heegaard

et al.

The impact of Staphylococcus aureus concentration on development of pulmonary lesions and cytokine expression after intravenous inoculation of pigs. Vet Pathol 2012; 49: 950–962.

21.

Hernandez-Richter

Schardey

Löhlein

et al.

The prevention and treatment of vascular graft infection with triclosan (Irgasan)-bonded Dacron graft: an experimental study in the pig. Eur J Vasc Endovasc Surg 2000; 20: 413–418.

22.

Nielsen

Afzelius

Bender

et al.

Comparison of autologous 111In-leukocytes, 18F-FDG, 11C-methionine, 11C-PK11195 and 68GA-citrate for diagnostic nuclear imaging in a juvenile porcine haematogenous Staphylococcus aureus osteomyelitis model. Am J Nucl Med Mol Imaging 2015; 2: 169–182.

23.

Christiansen

Jensen

Johansen

et al.

Porcine models of non-bacterial thrombotic endocarditis (NBTE) and infective endocarditis (IE) caused by Staphylococcus aureus: a preliminary study. J Heart Valve Dis 2003; 22: 368–376.

24.

Nusbaum

Gil

Rippy

et al.

Effective method to remove wound bacteria: comparison of various debridement modalities in an in vivo porcine model. J Surg Res 2012; 176: 701–707.

25.

Soerensen

Nielsen

Birck

et al.

The use of sequential organ failure assessment parameters in an awake porcine model of severe Staphylococcus aureus sepsis. APMIS 2012; 120: 909–921.

26.

Elman

Goldstein

Marquette

et al.

Influence of lung aeration on pulmonary concentrations of nebulized and intravenous amikacin in ventilated piglets with severe bronchopneumonia. Anesthesiology 2002; 97: 199–206.

27.

Moxley

Francis

Tamura

et al.

Efficacy of Urtoxazumab (TMA-15 Humanized monoclonal antibody specific for shiga toxin 2) against post-diarrheal neurological sequelae caused by Escherichia coli O157:H7 infection in the neonatal gnotobiotic piglet model. Toxins 2017; 49: 1–18.

28.

Goldfarb

Marton

Szabó

et al.

Protectice effect of a novel potent inhibitor of poly(adenosine 5’-diphosphate-ribose) synthetase in a porcine model of severe bacterial sepsis. Crit Care Med 2002; 5: 974–980.

29.

Skorup

Maudsdotter

Lipcsey

et al.

Beneficial antimicrobial effect of the addition of an aminoglycoside to a β-lactam antibiotic in an E.coli porcine intensive care severe sepsis model. PloS One 2014; 9: 1–10.

30.

Johansen

Koch

Frees

et al.

Pathology and biofilm formation in a porcine model of Staphylococcal osteomyelitis. J Comp Pathol 2012; 147: 343–353.

31.

Johansen

Frees

Aalbæk

et al.

A porcine model of acute, haematogenous, localized osteomyelitis due to Staphylococcus aureus: a pathomorphological study. APMIS 2010; 119: 111–118.

32.

Harrasser

Gorkotte

Obermeier

et al.

A new model of implant-related osteomyeliyis in the metaphysis of rat tibiae. BMC Musculoskelet Disord 2016; 152: 1–11.

33.

Gao

Sandermann

Prag

et al.

Prevention of primary vascular graft infection with silver-coated polyester graft in a porcine model. Eur J Vasc Surgy 2010; 39: 472–477.

34.

Elahi

Buchanan

Babiuk

et al.

The host defense peptide beta-defensin 1 confers protection against Bordetella pertussis in newborn piglets. Infect Immun 2006; 5: 2619–2627.

35.

Elahi

Buchanan

Attah-Poku

et al.

Maternal immunity provides protection against Pertussis in newborn piglets. Infect Immun 2006; 4: 2338–2352.

36.

Van Kam

Lutter

Lachmann

et al.

Effect of ventilation strategy and surfactant on inflammation in experimental pneumonia. Eur Respir 2005; 26: 112–117.

37.

Cilieborg

Thymann

Siggers

et al.

The incidence of necrotizing enterocolitis is increased following probiotic administration to preterm pig. J Nutr 2010; 141: 223–230.

38.

Coulthard

Flecknell

Orr

et al.

Renal scarring caused by vesicureteric reflux and urinary infection: a study in pigs. Pediatr Nephrol 2002; 17: 481–484.

39.

Jensen

Koch

Dich-Jorgensen

et al.

Novel porcine model of implant-associated osteomyelitis: a comprehensive analysis of local, regional and systemic response. J Orthop Res 2017; 35: 2211–2221.

40.

Elahi

Brownlie

Korzeniowski

et al.

Infection of newborn piglets with Bordetella pertussis: a new model for pertussis. Infec Immun 2005; 6: 3636–3645.

41.

Lorenzen

Follmann

Secher

et al.

Intrauterine inoculation of minipigs with Chlamydia trachomatis during diestrus establishes a longer lasting infection compared to vaginal inoculation during estrus. Microbes Infect 2017; 19: 334–342.

42.

Ricci

Mehran

Petsikas

et al.

Species differences in the infectability of vascular grafts. J Invest Surg 1991; 4: 45–52.

43.

Bolin

Whipple

Khanna

et al.

Infection of swine with Mycobacyerium bovis as a model of human tuberculosis. J Infect Dis 1997; 176: 1559–1566.

44.

Goldstein

Bughalo

Marquette

et al.

Mechanical ventilation-induced air-space enlargement during experimental pneumonia in piglet. Am J Respir Crit Care Med 2001; 163: 958–964.

45.

Aboshady

Raad

Shah

et al.

A pilot study of a triple antimicrobial-bonded dacron graft for the prevention of aortic graft infection. J Vasc Surg 2012; 3: 794–801.

46.

Johansen

Svalastoga

Frees

et al.

A new technique for modeling of hematogenous osteomyelitis in pigs: inoculation into femoral artery. J Invest Surg 2012; 3: 149–153.

47.

Slater

Kunnathil

McBride

et al.

Pharmacology of nonsteroidal antiinflammatory drugs and opioids. Semin Intervent Radiol 2010; 27: 400–411.

48.

Gao

Lund

Prag

et al.

Laparoscopic diagnosis and treatment of aortic vascular prosthetic graft infections in a porcine model. Eur J Vasc Endovasc Surg 2008; 35: 41–45.

49.

Wood

Cutlip

Shuman

. Osteomyelitis and arthritis induced in swine by Lancefield's group A Streptococci (Streptococcus pyogenes). Cornell Vet 1970; 61: 457–470.

50.

Dewar

Jones

Griffin

et al.

A study of experimental endocarditis in pigs. J Comp Pathol 1987; 97: 567–574.

51.

Breuing

Kaplan

Liu

et al.

Wound fluid bacterial levels exceed tissue bacterial counts in controlled porcine partial thickness burn infections. Plast Reconstr Surg 2003; 2: 781–788.

52.

Thibodeaux

James

Lohr

et al.

Infection of endovascular stents in a swine model. Am J Surg 1996; 172: 151–154.

53.

Chevaleyre

Riou

Bréa

et al.

The pig: a relevant model for evaluating the neutrophil serine protease activities during acute Pseudomonas aeruginosa lung infection. PloS One 2016; 11: 1–17.

54.

Hodson

Maling

McManamom

. The pathogenesis of reflux nephropathy (Chronic atrophic pyelonephritis). Br J Radiol 1975; (Suppl 13)1–23.

55.

Nielsen

Iburg

Aalbaek

et al.

A pig model of acute Staphylococcus aureus induced pyemia. Acta Vet Scand 2009; 14: 1–8.

56.

Soerensen

Olsen

Skovgaard

et al.

Disseminated intravascular coagulation in a novel porcine model of severe Staphylococcus aureus sepsis fulfills human clinical criteria. J Comp Pathol 2013; 149: 463–474.

57.

McDermid

Morck

Olson

et al.

A porcine model of Staphylococcus epidermidis catheter-associated infection. J Infect Dis 1993; 168: 897–903.

58.

Aggarwal

Higuera

Deirmengian

et al.

Swabs cultures are not as effective as tissue cultures for diagnosis of periprosthetic joint infections. Clin Orthop Relat Res 2013; 471: 3196–3203.

59.

Høiby

Bjarnsholt

Moser

et al.

ESCMID guidelines for the diagnosis and treatment of biofilm infections. Clin Microbiol Infect 2015; 21: S1–S25.

60.

Pezzulo

Tang

Hoegger

et al.

Reduced airway surface pH impairs bacterial killing in the porcine cystic fibrosis lung. Nature 2013; 487: 109–113.

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