Escherichia coli Isolated from Organic Laying Hens Reveal a High Level of Antimicrobial Resistance despite No Antimicrobial Treatments.

The present study investigated the resistance characteristics of E. coli isolates originating from 18 organic laying hen flocks. E. coli was isolated from different organs at three different time points, resulting in 209 E. coli isolates. The antibiotic susceptibility was determined by applying a microdilution assay. General, a high resistance rate was found. The antibiotic susceptibility was independent from the presence of pathological lesions, the isolation site, or the affiliation to a pathogenic serogroup. The majority of the isolates proved to be multi-drug-resistant (95.70%), of which 36.84% could be categorized as extensively drug-resistant. All isolates were resistant to oxacillin and tylosin. Resistance rates to amoxicillin (67.94%), cefoxitin (55.98%), ceftazidime (82.30%), colistin (73.68%), nalidixic acid (91.87%), streptomycin (42.58%), tetracycline (53.59%), and sulfamethoxazole (95.22%) were high. None of the isolates revealed pan-drug-resistance. A great heterogeneity of resistance profiles was found between isolates within a flock or from different organs of the same bird, even when isolates originated from the same organ. An increase in antimicrobial resistance was found to be correlated with the age of the birds. The fact, that no antibiotic treatment was applied except in two flocks, indicates that resistant bacteria circulating in the environment pose a threat to organic systems.

Identical Genetic Profiles of Escherichia coli Isolates from the Gut and Systemic Organs of Chickens Indicate Systemic Bacterial Dissemination, Most Likely Due to Intestinal Destruction Caused by Histomonosis.

In laying and breeding chickens, pathomorphological signs of histomonosis often coincide with colibacillosis. Thus, we investigated the systemic spread of Escherichia coli in chickens affected with histomonosis and colibacillosis by characterizing their pheno- and genotypic profiles. For this, 29 birds from 11 affected flocks were necropsied and up to three E. coli isolates each from intestine, heart, and liver of the birds were isolated. A total of 251 isolates were characterized by serotyping, phylogenetic grouping, detection of virulence-associated genes (VAGs), and pulsed-field gel electrophoresis (PFGE). All birds showed egg peritonitis, and fibrinous typhlitis was additionally recorded in 18 birds. Presence of Histomonas meleagridis in ceca was confirmed by PCR and histopathology. Escherichia coli serotype O2:K1 was found to be the most prevalent (37.4%), whereas 31.1% of strains were not typeable. The majority of isolates collected from the intestine and extraintestinal organs belonged to phylogroups B2 (54.1%), D (21.5%), or A (19.5%). Isolates from these phylogroups harbored a higher number of VAGs. Macrorestriction analysis showed that 60.6% of total isolates from all organs tested were included in eight PFGE types. Isolation of E. coli with identical genomic profiles from the intestine and extraintestinal organs of the same or different birds in the same flock indicates for systemic dissemination of the bacteria, independent of E. coli genotype. Intestinal destruction due to H. meleagridis can be considered as the most plausible cause of bacterial dissemination, ultimately leading to colibacillosis.

Species-specific identification and differentiation of Arcobacter, Helicobacter and Campylobacter by full-spectral matrix-associated laser desorption/ionization time of flight mass spectrometry analysis.

Rapid and reliable identification of Arcobacter and Helicobacter species, and their distinction from phenotypically similar Campylobacter species, has become increasingly important, since many of them are now recognized as human and/or animal pathogens. Matrix-associated laser desorption/ionization-time of flight (MALDI-TOF) MS has been shown to be a rapid and sensitive method for characterization of micro-organisms. In this study, we therefore established a reference database of selected Arcobacter, Helicobacter and Campylobacter species for MALDI-TOF MS identification. Besides the species with significance as food-borne pathogens - Arcobacter butzleri, Helicobacter pullorum, Campylobacter jejuni and Campylobacter coli - several other members of these genera were included in the reference library to determine the species specificity of the designed MALDI Biotyper reference database library. Strains that made up the reference database library were grown on Columbia agar, and yielded reproducible and unique mass spectra profiles, which were compared with the Bruker Biotyper database, version 2. The database was used to identify 144 clinical isolates using whole spectral profiles. Furthermore, reproducibility of MALDI-TOF MS results was evaluated with respect to age and/or storage of bacteria and different growth media. It was found that correct identification could be obtained even if the bacteria were stored at room temperature or at 4 degrees C up to 9 days before being tested. In addition, bacteria were correctly identified when grown on Campylosel agar; however, they were not when grown on modified charcoal cefoperazone deoxycholate agar. These results indicate that MALDI-TOF MS fingerprinting is a fast and reliable method for the identification of Arcobacter and Helicobacter species, and their distinction from phenotypically similar Campylobacter species, with applications in clinical diagnostics.