Abstract
BackgroundShiga toxin-producing Escherichia coli (STEC) are emerging foodborne pathogens that are public health concern. Cattle have been identified as the major STEC reservoir. In the present study, we investigated the prevalence and characteristics of STEC strains in beef cattle from a commercial farm in Sichuan province, China.ResultsAmong 120 beef cattle fecal samples, stx genes were positive in 90% of samples, as assessed using TaqMan real-time PCR, and 87 (72.5%) samples were confirmed to yield at least one STEC isolate by culture using four selective agars, MacConkey, CHROMagar™ ECC, modified Rainbow® Agar O157, and CHROMagar™ STEC, from which 31, 32, 91, and 73 STEC strains were recovered, respectively. A total of 126 STEC isolates were selected and further characterized. Seventeen different O:H serotypes were identified, all of which belonged to the non-O157 serotypes. One stx1 subtype (stx1a) and three stx2 subtypes (stx2a, stx2c, and stx2d) were present among these isolates. The intimin encoding gene eae, and other adherence-associated genes (iha, saa, and paa) were present in 37, 125, 74, and 30 STEC isolates, respectively. Twenty-three isolates carried the virulence gene subA, and only one harbored both cnf1 and cnf2 genes. Three plasmid-origin virulence genes (ehxA, espP, and katP) were present in 111, 111, and 7 isolates, respectively. The 126 STEC isolates were divided into 49 pulsed-field gel electrophoresis (PFGE) patterns.ConclusionsOur study showed that the joint use of the selective MacConkey and modified Rainbow® Agar O157 agars increased the recovery frequency of non-O157 STEC strains in animal feces, which could be applied to other samples and in regular STEC surveillance. Moreover, the results revealed high genetic diversity of non-O157 STEC strains in beef cattle, some of which might have the potential to cause human diseases.
Highlights
Shiga toxin-producing Escherichia coli (STEC) are emerging foodborne pathogens that are public health concern
Prevalence of stx genes in beef cattle fecal samples Among the 120 fecal samples screened by TaqMan realtime PCR, 108 (90%) were positive for stx1 or stx2 or both (cycle threshold (Ct) values below 40), among which 80.8% of the samples were positive for both stx1 and stx2, while 9.2% (11 samples) were only stx2 positive (Additional file 1: Table S1)
STEC isolates recovered from different selective chromogenic agars Four different selective chromogenic agars, i.e. MAC (MacConkey), CH-ECC (CHROMagarTM ECC), RBA-NT (modified Rainbow® Agar O157 and CH-STEC (CHROMagarTM STEC), were used simultaneously to isolate STEC strains from all 120 samples
Summary
Shiga toxin-producing Escherichia coli (STEC) are emerging foodborne pathogens that are public health concern. Shiga toxin-producing Escherichia coli (STEC) strains are significant foodborne zoonotic pathogens that are associated with illnesses ranging from mild diarrhea to hemorrhagic colitis (HC) and life-threatening hemolytic uremic syndrome (HUS) complications in humans [1]. Shiga toxin (Stx), including Shiga toxin 1 (Stx1) and Shiga toxin 2 (Stx2) (encoded by stx and stx genes), are essential virulence factors in STEC strains [8]. The presence of stx2a and/or stx2c genes is more frequently related to severe clinical diseases [11]. Strains containing a Shiga toxin gene together with the LEE island are classified as EHEC, which are associated with more severe clinical symptoms in humans [13]. Enterohemolysin (ehxA) can destroy mammalian cell membranes; serine protease (espP) and catalase-peroxidase (katP) contribute to the colonization of STEC strains in the human intestinal tract; and ToxB contributes to the adherence of O157: H7 to Caco-2 cells [18]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
