Shiga toxin (stx) encoding genes in sheep and goats reared in Trinidad and Tobago

Abstract

Shiga toxin-producing Escherichia coli (STEC) is estimated to cause over two million cases of human disease annually. Trinidad and Tobago is one of the largest livestock producer and consumer of sheep and goat meat in the Caribbean, however, the potential role of these animals in the epidemiology of STEC infections has not been previously described. To fill this critical gap in knowledge, the prevalence of Shiga toxin genes (stx1 and stx2) shed in the faeces of healthy sheep (n = 204) and goats (n = 105) in Trinidad was investigated. Based on PCR screening, goats had a higher stx prevalence than sheep (46% vs 35%, P = 0.06). Most of the recovered STEC isolates were positive for stx1 only; and only three isolates were positive for the eae gene. None of the recovered isolates belonged to the O157 serogroup. In both species, the prevalence of stx was higher in young animals versus older animals. Sheep reared on deep litter flooring (43%) had a higher prevalence than sheep reared other flooring types, however this was not the same for goats. The presence of cows on the same premise was not an associated predictor for STEC carriage in sheep or goats. This study demonstrates that although sheep and goats in Trinidad are reservoirs for stx-positive E. coli isolates, no fecal samples tested positive for O157 STEC, harbored. Furthermore, it appears that non-O157 stx-positive isolates harbored by these animals do not pose a significant threat to human health

A Comprehensive Review on Shiga Toxin Subtypes and Their Niche-Related Distribution Characteristics in Shiga-Toxin-Producing E. coli and Other Bacterial Hosts

“…Other studies conducted in countries such as Ireland [125], Iran [127], Norway [126], Spain [128], New Zealand [129], Australia [130], the United States [131], and Brazil [132] have also reported high STEC prevalences in sheep populations worldwide, ranging from 45% to as high as 87.6%. Conversely, comparatively fewer studies have reported low STEC prevalences in sheep populations, ranging between 32~36% [120,133,134].…”

“…While there does not appear to be an identifiable pattern of distribution of stx1and stx2-positive STEC strains within cattle populations, the STEC strains that colonize sheep appear to be more likely to be positive for stx1 than stx2. For example, Persad et al [134] found that, among 453 sheep STEC strains, 71% were positive for stx1 only, compared with the 11% that were stx2-positive only and the 18% that were positive for both. Similarly, Sánchez et al [128] found that the proportion of stx1-postive STEC strains (52.8%) from sheep was markedly greater than that for stx2-positive strains (8.4%), though a significant proportion of isolates (38.8%) were found to harbor both stx1 and stx2 genes.…”

“…Concerning the distribution of stx types in goat STEC strains, several studies have reported an overabundance of stx1-positive strains compared with those that carry the stx2 gene [142,143]. For instance, Persad et al [134] found that 79% of STEC strains isolated from goats were stx1-positive compared with 18% that were stx2 positive and 8% that were positive for both. Similarly, Wiriyaprom et al [144] found that across several farms in Thailand, the primary stx represented was stx1, found in 75.44% of STEC strains isolated from goats, compared with 22.81% of goat STEC strains that were stx2-positive and 1.75% that carried both stx1 and stx2.…”

In vitro and In silico Evaluation of Antibacterial Effects in Some Oxadiazole Compounds against Escherichia coli O157: H7

“…As a result, all enterohemorrhagic E. coli strains found in animals are considered a risk to humans. However, serotype O157 can cause disease in humans and does not pose a risk to adult animals (7). The virulence factors of E. coli O157:H7, including toxins, adhesins, hemolysin, lipopolysaccharide, and flagellum, significantly contribute to the low infectious dose of this bacterium (8).…”