Comparison of clinical and immunological findings in gnotobiotic piglets infected with Escherichia coli O104:H4 outbreak strain and EHEC O157:H7

Abstract

BackgroundShiga toxin (Stx) producing Escherichia coli (E. coli) (STEC) is the most frequent cause of diarrhoea-positive haemolytic uraemic syndrome (D + HUS) in humans. In 2011, a huge outbreak with an STEC O104:H4 strain in Germany highlighted the limited possibilities for causative treatment of this syndrome. The responsible STEC strain was found to combine Stx production with adherence mechanisms normally found in enteroaggregative E. coli (EAEC). Pathotypes of E. coli evolve and can exhibit different adhesion mechanisms. It has been shown previously that neonatal gnotobiotic piglets are susceptible for infection with STEC, such as STEC O157:H7 as well as for EAEC, which are considered to be the phylogenetic origin of E. coli O104:H4. This study was designed to characterise the host response to infection with the STEC O104:H4 outbreak strain in comparison to an STEC O157:H7 isolate by evaluating clinical parameters (scoring) and markers of organ dysfunction (biochemistry), as well as immunological (flow cytometry, assessment of cytokines/chemokines and acute phase proteins) and histological alterations (light- and electron microscopy) in a gnotobiotic piglet model of haemolytic uraemic syndrome.ResultsWe observed severe clinical symptoms, such as diarrhoea, dehydration and neurological disorders as well as attaching-and-effacing lesions (A/E) in the colon in STEC O157:H7 infected piglets. In contrast, STEC O104:H4 challenged animals exhibited only mild clinical symptoms including diarrhoea and dehydration and HUS-specific/severe histopathological, haematological and biochemical alterations were only inconsistently presented by individual piglets. A specific adherence phenotype of STEC O104:H4 could not be observed. Flow cytometric analyses of lymphocytes derived from infected animals revealed an increase of natural killer cells (NK cells) during the course of infection revealing a potential role of this subset in the anti-bacterial activity in STEC disease.ConclusionsUnexpectedly, E. coli O104:H4 infection caused only mild symptoms and minor changes in histology and blood parameters in piglets. Outcome of the infection trial does not reflect E. coli O104:H4 associated human disease as observed during the outbreak in 2011. The potential role of cells of the innate immune system for STEC related disease pathogenesis should be further elucidated.

Modeling Hemolytic-Uremic Syndrome: In-Depth Characterization of Distinct Murine Models Reflecting Different Features of Human Disease

“…In accordance with our recent observations in EHEC-infected gnotobiotic piglets ( 25 ) and with the finding by Sauter et al in Stx2-challenged mice ( 33 ), we found low leukocyte counts in both models that were accompanied by persistent neutrophilia. There is some evidence that neutrophilia directly contributes to Stx2 toxicity as mortality and kidney damage are reduced in a murine model of HUS using polymorphonuclear-cell-(PMN)-depleted mice ( 56 ).…”

“…In our study, acute or subacute progression of HUS-like disease in mice was induced by application of different doses of Stx2, purified from the well-characterized EHEC O157:H7 patient isolate 86-24 originating from a HUS outbreak in the USA ( 35 ). Apart from being the causative agent for HUS in humans, this strain reproducibly induced a HUS-like disease in gnotobiotic piglets ( 22 , 24 , 25 ). In contrast to other studies, we injected Stx2 i.v.…”

“…Since Karmali linked sporadic cases of HUS with cytotoxin-producing E. coli isolated from patient feces in a breakthrough discovery in 1983 ( 2 ), numerous in vivo models have been developed to study this syndrome, applying such different animals as non-human primates ( 19 , 20 ), gnotobiotic piglets ( 21 – 25 ), rabbits ( 26 , 27 ), rats ( 28 – 30 ), and mice ( 31 – 34 ). Reportedly, certain aspects of HUS, such as, thrombotic microangiopathy, glomerular damage, and thrombocytopenia, are difficult to reproduce in murine models ( 32 , 33 ).…”

The use of non-rodent model species in microbiota studies

“…[117][118][119] A more comprehensive review of the use of pigs colonized with human GM is provided by Wang and Donovan. 113 Similarly, piglets delivered via cesarean section can be monocolonized 120,121 or colonized with a highly restricted defined microbiota similar to Altered Schaedler Flora used in mice 122,123 to tightly control GM composition.…”

The piglet acute diarrhea model for evaluating efficacy of treatment and control of cryptosporidiosis

“…Although full maturation with CD8 + T cells and IgA + B cells occurs within 7 weeks, lymphoid structures within GALT develop an adult architecture by 10-15 days, and are populated by CD4 + lymphocytes and IgM producing B between 2-4 weeks. 17 Due to lack of maternal antibody and premature gut immune system, GB piglets are very susceptible to human enteric pathogens such as rotavirus, 18 Shiga toxin producing Escherichia coli, [19][20][21] Shigella spp., 22 Clostridium difficile, 23 and Cryptosporidium spp. [24][25][26] The clinical symptoms and the mucosal lesions induced, location and distribution by these agents in GB piglets, are similar or identical to those observed in humans.…”