Abstract
BackgroundAll over the world, Shiga toxin-producing Escherichia coli (STEC) are considered as important zoonotic pathogens. Eight serogroups have the greatest role in the outbreaks and diseases caused by STEC which include O26, O45, O103, O111, O113, O121, O145 and O157. Ruminants, especially cattle are the main reservoirs but the role of small ruminants in the epidemiology of human infections has not been thoroughly assessed in many countries. The objective of this research was to investigate the pathogenic potential of the STEC strains isolated from slaughtered goats. In this study, a total of 57 STEC strains were recovered from 450 goats and characterized by subtyping of stx genes, O-serogrouping, phylo-typing and DNA fingerprinting.ResultsAmongst 57 STEC strains isolated from goats, the prevalence of stx1 was significantly more than stx2 (98.2% vs. 24.5%; P ≤ 0.05), and 22.8% of strains harbored both stx1 and stx2 genes. Three (5.2%) isolates were characterized as EHEC, which carried both eae and stx genes. A total of five stx-subtypes were recognized namely: stx1c (94.7%), stx1a (53.7%), stx2d (21%), stx2c (17.5%), and stx2a (15.7%). In some parts of the world, these subtypes have been reported in relation with severe human infections. The stx subtypes predominantly occurred in four combinations, including stx1a/stx1c (35%), stx1c (31.5%), stx1c/stx2a/stx2c/stx2d (5.2%) and stx1c/stx2c/stx2d (%5.2%). In serogrouping, the majority of STECs from goats did not belong to the top 8 serogroups but two strains belonged to O113, which has been recognized as an important pathogenic STEC in Australia. Interestingly, none of stx+eae+ isolates belonged to the tested serogroups. In phylo-typing the isolates mostly belonged to phylo-group B1 (82.4%), followed by phylo-group A (12.3%). STEC strains showed a substantial diversity in DNA fingerprinting; there were 24 unique ERIC-types (with a ≥95% similarity) among the isolates.ConclusionsDespite the fact that the top 8 STEC serogroups were uncommon in caprine strains, the presence of highly pathogenic stx subtypes indicates that small ruminants and their products can be considered as an overlooked public health risk for humans, especially in developing countries which consume traditional products.
Highlights
All over the world, Shiga toxin-producing Escherichia coli (STEC) are considered as important zoonotic pathogens
Subtyping of stx genes The glycerolated STEC strains were refreshed in Brain Heart Infusion (BHI) broth, (Merck, Germany) plated on MacConkey agar and a single-colony was selected from each plate for DNA extraction
Molecular screening of top eight STEC serogroups We evaluated attendance of eight important and human pathogenic serogroups (O26, O45, O103, O111, O113, O121, O145 and O157) among all stx-positive strains using a multiplex-Polymerase Chain Reaction (PCR); this method has been developed by DebRoy et al (2011) [19]
Summary
Shiga toxin-producing Escherichia coli (STEC) are considered as important zoonotic pathogens. A total of 57 STEC strains were recovered from 450 goats and characterized by subtyping of stx genes, O-serogrouping, phylo-typing and DNA fingerprinting. Shiga toxin-producing Escherichia coli (STEC) are among the most challenging microorganisms of public health concern. This is because they are known as foodborne pathogens and are responsible for the sporadic and epidemic incidence of hemorrhagic colitis (HC) and hemolytic uremic syndrome (HUS), worldwide [1]. The pathogenic potential of STEC strains can be attributed to various factors, such as virulence genes and Shiga toxin subtypes [3]. Some studies have reported the relationship between some subtypes with HC and HUS infections e.g. Stx2a, Stx2c and Stx2d [6, 7]
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