Surveillance of Extended-Spectrum Beta-Lactamase-Producing Escherichia coli in Dairy Cattle Farms in the Nile Delta, Egypt

Introduction: Industrial livestock farming is a possible source of multi-resistant Gram-negative bacteria, including producers of extended spectrum beta-lactamases (ESBLs) conferring resistance to 3rd generation cephalosporins. Limited information is currently available on the situation of ESBL producers in livestock farming outside of Western Europe. A surveillance study was conducted from January to May in 2014 in four dairy cattle farms in different areas of the Nile delta, Egypt. Materials and Methods: In total, 266 samples were collected from 4 dairy farms including rectal swabs from clinically healthy cattle (n=210), and environmental samples from the stalls (n=56). After 24h pre-enrichment in buffered peptone water, all samples were screened for 3rd generation cephalosporin-resistant Escherichia coli using BrillianceTM ESBL agar. Suspected colonies of putatively ESBL-producing E. coli were sub-cultured and subsequently genotypically and phenotypically characterized. Susceptibility testing using the VITEK-2 system was performed. All suspect isolates were genotypically analysed using two DNA-microarray based assays: CarbDetectAS-1 and E. coli PanTypeAS-2 kit (ALERE). These tests allow detection of a multitude of genes and their alleles associated with resistance toward carbapenems, cephalosporins, and other frequently used antibiotics. Serotypes were determined using the E. coli SeroGenotyping AS-1kit (ALERE). Results: Out of 266 samples tested, 114 (42.8%) ESBL-producing E. coli were geno-and phenotypically identified. 113 of 114 phenotypically 3rd generation cephalosporin-resistant isolates harboured at least one of the ESBL resistance genes covered by the applied assays [blaCTX-M15 (n=105), blaCTX-M9 (n=1), blaTEM (n=90), blaSHV (n=1)]. Alarmingly, the carbapenemase genes blaOXA-48 (n=5)and blaOXA-181 (n=1) were found in isolates that also were phenotypically resistant to imipenem and meropenem. Using the array-based serogenotyping method, 66 of the 118 isolates (55%) could be genotypically assigned to O-types. Conclusion: This study is considered to be a first report of the high prevalence of ESBL-producing E. coli in dairy farms in Egypt. ESBL-producing E. coli isolates with different underlying resistance mechanisms are common in investigated dairy cattle farms in Egypt. The global rise of ESBL-and carbapenemase-producing Gram-negative bacteria is a big concern, and demands intensified surveillance.