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FACTORS AFFECTING CALF ENTERITIS INFECTION CAUSED BY SALMONELLAE AND ESCHERICHIA COLI

Calf diarrhea is a major economic concern in bovine industry all around the world. Therefore, the present study was designed to investigate seasonal and age variations in the prevalence of E. coli and Salmonella species in diarrheic calves and their virulence genes, pathotypes, serogroups and antibiogram. Bacteriological examination of 120 fecal samples collected from diarrheic calves less than three months of age in dry and rainy seasons showed that, 71 (59.5%) and 36 (30%) were positive for E. coli and Salmonella species, respectively while 26 (21.66%) had mixed E. coli and Salmonella species infection. The most prevalent E. coli serogroups were O111 and O26 and Salmonella serovars were S. typhimurium and S. enteritidis. Isolation frequency of E. coli was significantly higher than Salmonella species isolated from diarrheic calves in different ages and seasons (P value=0.004). E. coli and Salmonella species was statistically significant higher in rainy season than dry season. PCR investigation of six virulence determinants among the MDR E. coli isolates revealed that fimH and iss, were the most prevalent (100%), followed by sxt2 (90%), sxt1 (80%), hylA (60% ) and eaeA (40%). All examined multiple drug resisitant (MDR) Salmonella species isolates harbored both invA and sopB virulence genes. E. coli and Salmonella species isolates showed a high sensitivity rate for amikacin (100%), and ciprofloxacin (78.8% and 77.7%), respectively but showed resistance against amoxicillin and tetracycline. The most commonly detected resistance gene was tetA gene. Finally, strict management and hygienic measures should be taken in rearing neonatal calves especially in rainy seasons.