ABSTRACT
Colibacillosis is the most common bacterial disease in poultry and it is caused by avian pathogenic Escherichia coli (APEC), which is assigned to various O-serogroups. Previous studies have shown that APEC strains are more often related to certain O-serogroups such asO78, O2 and O1. E. coli has been reported to act either as a primary or secondary agent in complicating other infections. The aim of this study was to investigate the occurrence of and characterize the O-serogroups of E. coli strains isolated from commercial layer and layer breeder flocks showing macroscopic lesions of colibacillosis and increased or normal mortality in Greece. Furthermore, we attempted to assess the interaction between infectious agents such as Mycoplasma gallisepticum (MG), Mycoplasma synoviae (MS), infectious bronchitis (IBV) and infectious laryngotracheitis (ILT) with E. coli infections in layer flocks with increased mortality. Our study revealed that in addition to the common serogroups (O78, O2), many other, and less common serogroups were identified, including O111. The O78, O111 and O2 serogroups were frequently detected in flocks with lesions of colibacillosis and increased mortality whereas O2, O88 and O8 were reported more commonly in birds with colibacillosis lesions but normal mortality rates. These data provide important information for colibacillosis monitoring and define preventative measures, especially by using effective vaccination programs because E. coli vaccines are reported to mainly offer homologous protection. Finally, concerning the association of the four tested infectious agents with E. coli mortality, our study did not reveal a statistically significant effect of the above infectious agents tested with E. coli infection mortality.
ABSTRACT
Objectives: The aim of this study was to investigate the antimicrobial resistance (AMR) patterns of Escherichia coli strains isolated from poultry flocks suffering from colibacillosis in Greece and to detect the presence of the mcr-1 gene in isolates being phenotypically resistant to colistin. Results: A total of 150 E. coli strains were isolated from commercial layers and layer breeder flocks in Greece and tested for antimicrobial susceptibility. A high level of susceptibility was revealed for cephalosporins, neomycin, and colistin. Susceptibility varied for other antimicrobials (tetracycline, doxycycline, lincospectin, trimethoprim/sulfamethoxazole, enrofloxacin, amoxicillin), whereas no susceptibility was reported for macrolides, tiamulin, lincomycin, oxacillin. Concerning colistin resistance, 20 E. coli strains were found to be phenotypically resistant (13 strains showed intermediate resistance pattern and 7 strains fully resistance trait). Further investigation was performed by PCR, which has revealed the presence of the mcr-1 gene in one phenotypically colistin-resistant isolate. Conclusion: AMR is prevalent in layer poultry production, including resistance against colistin confirmed by the presence of the mcr-1 gene.
