Abstract
Calf diarrhea is one of the considerable infectious diseases in calves, which results in tremendous economic losses globally. To determine the prevalence of Shiga-toxigenicE. coli(STEC) and EnterotoxigenicE. coli(ETEC) incriminated in calf diarrhea, with special reference to Shiga- toxins genes (stx1 andstx2) and enterotoxins genes (ltandsta) that govern their pathogenesis, as well as the virulence genes;eaeA (intimin) andf41(fimbrial adhesion), and the screening of their antibiogram and antimicrobial resistance genes;aadB,sul1, andbla-TEM, a total of 274 fecal samples were collected (April 2018-Feb 2019) from diarrheic calves at different farms in El-Sharqia Governorate, Egypt. The bacteriological examination revealed that the prevalence ofE. coliin diarrheic calves was 28.8%. The serotyping of the isolatedE. colirevealed 7 serogroups; O-26, O-128, O-111, O-125, O-45, O(119)and O-91. Furthermore, the Congo red binding test was carried out, where 89.8% of the examined strains (n = 71) were positive. The antibiogram of the isolated strains was investigated; the majority ofE. coliserotypes exhibit multidrug resistance (MDR) to four antimicrobial agents; neomycin, gentamycin, streptomycin, and amikacin. Polymerase chain reaction (PCR) was used to detect the prevalence of the virulence genes;stx1,stx2lt,sta,f41 andeaeA, as well as the antimicrobial resistance genes;aadB,sul1, andbla-TEM. The prevalence of STEC was 20.2% (n = 16), while the prevalence of ETEC was 30.4% (n = 24). Briefly, the Shiga toxins genes;stx1 andstx2, are the most prevalent virulence genes associated with STEC, which are responsible for the pathogenesis of the disease and helped by the intimin gene (eaeA). In addition, theltgene is the most prevalent enterotoxin gene accompanied by the ETEC strains, either alone or in combination withstaand/orf41 genes. The majority of pathogenicE. coliincriminated in calf diarrhea possesses theaadB resistance gene, followed by thesul1 gene. Enrofloxacin, florfenicol, amoxicillin-clavulanic acid, and ampicillin-sulbactam, are the most effective antimicrobial agents against the isolated STEC and ETEC strains.