Characterization of Diarrheagenic Strains of Escherichia coli Isolated From Cattle Raised in Three Regions of Mexico

Diarrheagenic Escherichia coli with Multidrug Resistance in Cattle from Mexico

Mexico is an important producer/exporter of cattle and cattle products. In the last decade, an increase in antibiotic resistance in E. coli pathotype strains from livestock environments has been reported. This study aimed to determine the prevalence and antibiotic resistance profiles of E. coli pathotype strains from the feces of beef or dairy cattle reared in the states of Aguascalientes (AG, central) and Nuevo Leon (NL, northeastern) in Mexico. One hundred and ten fecal samples were collected (beef cattle-AG = 30; dairy cattle-AG = 20; beef cattle-NL = 30; dairy cattle-NL = 30). From these, E. coli was isolated using selective/differential media and confirmed on chromogenic media. Multiplex PCR was used to identify diarrheagenic E. coli, and the Kirby-Bauer technique was used to determine the antimicrobial susceptibilities. All the animals harbored E. coli, and pathotypes were found in 34 animals from both, beef and dairy cattle, mainly from Aguascalientes. Of the positive samples, 31 harbored a single E. coli pathotype, whereas three samples harbored two different pathotypes; EHEC was the most prevalent, followed by EPEC, ETEC, and EIEC or the combination of two of them in some samples. Most pathotype strains (19/37) were isolated from beef cattle. Neither the animals' productive purpose (beef or dairy cattle) (r = 0.155) nor the geographic regions (Aguascalientes or Nuevo Leon) (r = -0.066) had a strong positive correlation with the number of E. coli pathotype strains. However, animals reared in Aguascalientes had up to 8.5-fold higher risk of harboring E. coli pathotype strains than those reared in Nuevo Leon. All pathotype strains were resistant to erythromycin, tetracycline, and trimethoprim/sulfamethoxazole, and all dairy cattle pathotype strains were further resistant to five β-lactams (χ2, P = 0.017). The existence of these pathotypes and multidrug-resistant pathogens in the food chain is a risk to public health.

Diversity of Potentially Pathogenic Escherichia coli O104 and O9 Serogroups Isolated before 2011 from Fecal Samples from Children from Different Geographic Regions

In 2011, an outbreak of hemorrhagic colitis and hemolytic uremic syndrome (HUS) was reported in Europe that was related to a hybrid STEAEC of Escherichia coli (E. coli) O104:H4 strain. The current study aimed to analyze strains of E. coli O104 and O9 isolated before 2011. The study included 47 strains isolated from children with and without diarrhea between 1986 and 2009 from different geographic regions, as well as seven reference strains. Serotyping was carried out on 188 anti-O and 53 anti-H sera. PCR was used to identify DEC genes and phylogenetic groups. Resistance profiles to antimicrobials were determined by diffusion in agar, while PFGE was used to analyze genomic similarity. Five serotypes of E. coli O104 and nine of O9 were identified, as well as an antigenic cross-reaction with one anti-E. coli O9 serum. E. coli O104 and O9 presented diarrheagenic E. coli (DEC) genes in different combinations and were located in commensal phylogenetic groups with different antimicrobial resistance. PFGE showed that O104:H4 and O9:(H4, NM) strains from SSI, Bangladesh and México belong to a diverse group located in the same subgroup. E. coli O104 and O9 were classified as commensal strains containing DEC genes. The groups were genetically diverse with pathogenic potential making continued epidemiologic surveillance important.

Multiplex PCR Assays for the Detection of One Hundred and Thirty Seven Serogroups of Shiga Toxin-Producing Escherichia coli Associated With Cattle

Escherichia coli carrying prophage with genes that encode for Shiga toxins are categorized as Shiga toxin-producing E. coli (STEC) pathotype. Illnesses caused by STEC in humans, which are often foodborne, range from mild to bloody diarrhea with life-threatening complications of renal failure and hemolytic uremic syndrome and even death, particularly in children. As many as 158 of the total 187 serogroups of E. coli are known to carry Shiga toxin genes, which makes STEC a major pathotype of E. coli. Seven STEC serogroups, called top-7, which include O26, O45, O103, O111, O121, O145, and O157, are responsible for the majority of the STEC-associated human illnesses. The STEC serogroups, other than the top-7, called “non-top-7” have also been associated with human illnesses, more often as sporadic infections. Ruminants, particularly cattle, are principal reservoirs of STEC and harbor the organisms in the hindgut and shed in the feces, which serves as a major source of food and water contaminations. A number of studies have reported on the fecal prevalence of top-7 STEC in cattle feces. However, there is paucity of data on the prevalence of non-top-7 STEC serogroups in cattle feces, generally because of lack of validated detection methods. The objective of our study was to develop and validate 14 sets of multiplex PCR (mPCR) assays targeting serogroup-specific genes to detect 137 non-top-7 STEC serogroups previously reported to be present in cattle feces. Each assay included 7–12 serogroups and primers were designed to amplify the target genes with distinct amplicon sizes for each serogroup that can be readily identified within each assay. The assays were validated with 460 strains of known serogroups. The multiplex PCR assays designed in our study can be readily adapted by most laboratories for rapid identification of strains belonging to the non-top-7 STEC serogroups associated with cattle.

Captive Green Iguana Carries Diarrheagenic Escherichia coli Pathotypes

The green iguana appears to be a carrier for bacteria causing gastrointestinal infections in humans. The presence of diarrheagenic E. coli (DEC) pathotypes, however, has not been studied in this reptile. The aim of the current work was to investigate the prevalence of DEC in the intestines of 240 captive green iguanas, their phylogenetic groups, and the antibiotic susceptibility profile. E. coli strains were isolated from 41.7% (N = 100/240) of the intestinal content of green iguanas. DEC strains was identified in 25.9% of the screened population and were detected in the majority (62%, p = 0.009) of those reptiles carrying E. coli strains. Among DEC strains, STEC strains carrying the stx1 gene were the most prevalent pathotype isolated (38.7%), followed by EAEC and ETEC (27.4% each). Genetic markers of DEC strains belonging to the EHEC pathotype were not detected. More than a half of DEC strains were classified into the Clade I-II phylogroup (64.5%), followed by the phylogroup A (14.5%). The antibiotic susceptibility method demonstrated that a high proportion of DEC strains were resistance, or non-susceptible, to carbenicillin, amikacin, and ampicillin. We conclude that the green iguana kept in captivity is a carrier of DEC strains bearing resistance to first-line antibiotics, including penicillins. Given the increase presence of the green iguana in Latin American households, these reptiles represent a potential source of transmission to susceptible humans and therefore a potential source of gastrointestinal disease.