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In this opinion, the antimicrobial-resistant bacteria responsible for transmissible diseases that constitute a threat to poultry health have been assessed. The assessment has been performed following a methodology based on information collected by an extensive literature review and expert judgement. Details of the methodology used for this assessment are explained in a separate opinion. A global state of play is provided for: Avibacterium (Haemophilus) paragallinarum, Bordetella avium, Clostridium perfringens, Enterococcus faecalis and Enterococcus cecorum, Erysipelothrix rhusiopathiae, Escherichia coli, Gallibacterium spp., Mycoplasma synoviae, Ornithobacterium rhinotracheale, Pasteurella multocida, Riemerella anatipestifer and Staphylococcus aureus. Among those bacteria, EFSA identified Escherichia coli, Enterococcus faecalis and Enterococcus cecorum with ≥ 66% certainty as being the most relevant antimicrobial resistant bacteria in the EU based on the available evidence. The animal health impact of these most relevant bacteria, and their eligibility for being listed and categorised within the Animal Health Law Framework, will be assessed in separate scientific opinions. info:eu-repo/semantics/publishedVersion

Avian pathogenic Escherichia coli (APEC) is the causal agent of colibacillosis, one of the most common bacterial infections in the poultry sector. Antimicrobial susceptibility testing (AST) is essential for rational and prudent antimicrobial therapy. Subsequently, uniformity in test results from the various testing methodologies used in diagnostic laboratories is pivotal. The aim of this study was therefore to evaluate the agreement between different AST methods in determining fluoroquinolone resistance in APEC. Twenty APEC isolates were selected and subjected to four different susceptibility tests: the quantitative microbroth dilution, agar dilution and gradient strip tests, and the qualitative disk diffusion method. The experiments were performed in triplicate. Categorical agreement, essential agreement and different errors were assessed. Moreover, agreement was also evaluated by calculating intraclass correlation coefficients (ICCs) for the quantitative tests and determining the Pearson correlation coefficients for the agreement between the disk diffusion method and the quantitative tests. Categorical agreement and essential agreement when compared with the microbroth technique ranged from 85–95% and 85–100%, respectively. No very major errors (false susceptible) and only one major error (false resistant) and minor errors (results involving an intermediary category) were detected. The calculated ICC values of the three quantitative tests fluctuated around 0.970 (range 0.940–0.988). There was a high negative correlation between the disk diffusion method and the other tests (correlation coefficients ranging from −0.979 to −0.940), indicating a clear inverse relationship between the minimum inhibitory concentration value and the zone diameter of growth inhibition. In conclusion, the overall agreement between the four different testing methodologies was very high. These results confirm the reliability of the disk diffusion and gradient strip test methods as substantiated alternatives, next to the gold standard agar and microbroth dilution, for fluoroquinolone susceptibility testing of APEC isolates.

The backbone of secreted autotransporter passenger proteins generally attains a stable β-helical structure. The secretion of passengers across the outer membrane was proposed to be driven by sequential folding of this structure at the cell surface. This mechanism would require a relatively-stable intermediate as starting point. Here, we investigated the mechanics of secreted truncated versions of the autotransporter Haemoglobin protease (Hbp) of Escherichia coli using atomic force microscopy. The data obtained reveal a β-helical structure at the C terminus that is very stable. In addition, several other distinct metastable intermediates are found which are connected during unfolding by multi-route pathways. Computational analysis indicates that these intermediates correlate to the β-helical rungs in the Hbp structure which are clamped by stacked aromatic residues. Our results suggest a secretion mechanism that is initiated by a stable C-terminal structure and driven forward by several folding intermediates that build up the β-helical backbone.

Many virulence factors secreted by pathogenic Gram-negative bacteria belong to the autotransporter (AT) family. ATs consist of a passenger domain, which is the actual secreted moiety, and a β-domain that facilitates the transfer of the passenger domain across the outer membrane. Here, we analysed folding and translocation of the AT passenger, using Escherichia coli haemoglobin protease (Hbp) as a model protein. Dual cysteine mutagenesis, instigated by the unique crystal structure of the Hbp passenger, resulted in intramolecular disulphide bond formation dependent on the periplasmic enzyme DsbA. A small loop tied off by a disulphide bond did not interfere with secretion of Hbp. In contrast, a bond between different domains of the Hbp passenger completely blocked secretion resulting in degradation by the periplasmic protease DegP. In the absence of DegP, a translocation intermediate accumulated in the outer membrane. A similar jammed intermediate was formed upon insertion of a calmodulin folding moiety into Hbp. The data suggest that Hbp can fold in the periplasm but must retain a certain degree of flexibility and/or modest width to allow translocation across the outer membrane. © 2007 The Authors.

Contamination of food and feed with mycotoxins is a worldwide problem. At present, acute mycotoxicosis caused by high doses is rare in humans and animals. Ingestion of low to moderate amounts of Fusarium mycotoxins is common and generally does not result in obvious intoxication. However, these low amounts may impair intestinal health, immune function and/or pathogen fitness, resulting in altered host pathogen interactions and thus a different outcome of infection. This review summarizes the current state of knowledge about the impact of Fusarium mycotoxin exposure on human and animal host susceptibility to infectious diseases. On the one hand, exposure to deoxynivalenol and other Fusarium mycotoxins generally exacerbates infections with parasites, bacteria and viruses across a wide range of animal host species. Well-known examples include coccidiosis in poultry, salmonellosis in pigs and mice, colibacillosis in pigs, necrotic enteritis in poultry, enteric septicemia of catfish, swine respiratory disease, aspergillosis in poultry and rabbits, reovirus infection in mice and Porcine Reproductive and Respiratory Syndrome Virus infection in pigs. However, on the other hand, T-2 toxin has been shown to markedly decrease the colonization capacity of Salmonella in the pig intestine. Although the impact of the exposure of humans to Fusarium toxins on infectious diseases is less well known, extrapolation from animal models suggests possible exacerbation of, for instance, colibacillosis and salmonellosis in humans, as well.

This study aimed to define the susceptibility of broilers to colibacillosis through quantification of clinical responses and to examine the relationship between susceptibility and growth retardation. A challenge experiment was carried out twice. In each trial, 192 chicks were challenged intratracheally with Escherichia coli (E. coli ) at 7 days of age and 160 chicks served as controls. Surviving chicks were euthanized at 14 or 15 days. Parameters measured were: daily mortality, lesion scores, body weight at 1, 4, 7, 10, 12 and 14 or 15 days and feeding behaviour at 6, 11 and 13 days. The results were reproducible, and increasing susceptibility to colibacillosis was defined by four categories: chicks without lesions, chicks with airsacculitis but no systemic lesions, chicks with systemic lesions, and chicks that die. Increasing susceptibility was associated with increasing growth retardation, but growth retardation was not inevitably linked to challenge with E. coli