Enterohemorrhagic Escherichia coli serotype O157:H7 is a pathotype of diarrheagenic E. coli that produces one or more Shiga toxins, forms a characteristic histopathology described as attaching and effacing lesions, and possesses the large virulence plasmid pO157. The bacterium is recognized worldwide, especially in developed countries, as an emerging food-borne bacterial pathogen, which causes disease in humans and in some animals. Healthy cattle are the principal and natural reservoir of E. coli O157:H7, and most disease outbreaks are, therefore, due to consumption of fecally contaminated bovine foods or dairy products. In this review, we provide a general overview of E. coli O157:H7 infection, especially focusing on the bacterial characteristics rather than on the host responses during infection.
Animals ; Cattle ; Cattle Diseases/blood/epidemiology ; Developing Countries ; *Enterohemorrhagic Escherichia coli ; Escherichia coli Infections/blood/*epidemiology/veterinary ; *Escherichia coli O157/genetics/pathogenicity ; Feces/microbiology ; Hemolytic-Uremic Syndrome/blood/epidemiology/veterinary ; Operon ; Shiga Toxins/analysis ; Shigella dysenteriae ; Virulence

Enterotoxigenic Escherichia coli (ETEC) causes neonatal and post-weaning diarrhea in pigs. In order to determine the risk factors, rectal/fecal swabs and visceral organs obtained from pig farms in two regions of South Africa were analyzed microbiologically against risk variables. Seventy-two percent of young pigs were found to be positive for ETEC toxin genes; estB (38.9%), estB/STAP (25%), and estB/LT (13.9%) were dominant. Risk factors for ETEC-diarrhea in pigs include: leaving sick piglets in a pen with healthy piglets [odds ratio (OR) = 33.52; P < 0.0001]; water spillage in pen (OR = 42.87; P < 0.0001); hypothermic piglets (OR = 7.29; P < 0.0001); runt piglets in pen with healthy littermates (OR = 3.65; P < 0.0001); and prolonged use of antibiotics (OR = 3.05; P = 0.05).
Animals ; Animals, Newborn ; Diarrhea ; epidemiology ; microbiology ; Escherichia coli ; genetics ; isolation & purification ; Escherichia coli Infections ; epidemiology ; microbiology ; veterinary ; Genes, Bacterial ; Prevalence ; Rectum ; microbiology ; Risk Factors ; South Africa ; Swine ; Swine Diseases ; epidemiology ; microbiology ; Weaning

To examine the genetic background of avian pathogenic Escherichia coli (APEC) that affects virulence of this microorganism, we characterized the virulence genes of 101 APEC strains isolated from infected chickens between 1985~2005. Serotypes were determined with available anti-sera and median lethal doses were determined in subcutaneously inoculated chicks. The virulence genes we tested included ones encoding type 1 fimbriae (fimC), iron uptake-related (iroN, irp2, iucD, and fyuA), toxins (lt, st, stx1, stx2, and vat), and other factors (tsh, hlyF, ompT, and iss). Twenty-eight strains were found to be O1 (2.0%), O18 (3.0%), O20 (1.0%), O78 (19.8%), and O115 (2.0%) serotypes. The iroN (100%) gene was observed most frequently followed by ompT (94.1%), fimC (90.1%), hlyF (87.1%), iss (78.2%), iucD (73.3%), tsh (61.4%), fyuA (44.6%), and irp2 (43.6%). The strains were negative for all toxin genes except for vat (10.9%). All the strains were classified into 27 molecular pathotypes (MPs). The MP25, MP19, and MP10 pathotypes possessing iroN-fimC-ompT-hlyF-iucD-tsh-iss-irp2-fyuA (22.8%), iroN-fimC-ompT-hlyF-iucD-tsh-iss (21.8%), and iroN-fimC-ompT-hlyF-iss (11.9%) genotypes, respectively, were predominant. Redundancy of iron uptake-related genes was clearly observed and some strains were associated with higher mortality than others. Therefore, strains with the predominant genotypes can be used for diagnosis and vaccine.
Animals ; Bacterial Proteins/genetics/metabolism ; Chickens ; Escherichia coli/*classification/genetics/*pathogenicity ; Escherichia coli Infections/epidemiology/microbiology/*veterinary ; Gene Expression Regulation, Bacterial/physiology ; Phylogeny ; Poultry Diseases/epidemiology/*microbiology ; Republic of Korea/epidemiology ; Virulence

This study was conducted to determine the prevalence and characteristics of pathogenic Escherichia (E.) coli strains from diarrheic calves in Vietnam. A total of 345 E. coli isolates obtained from 322 diarrheic calves were subjected to PCR and multiplex PCR for detection of the f5, f41, f17, eae, sta, lt, stx1, and stx2 genes. Of the 345 isolates, 108 (31.3%) carried at least one fimbrial gene. Of these 108 isolates, 50 carried genes for Shiga toxin and one possessed genes for both enterotoxin and Shiga toxin. The eae gene was found in 34 isolates (9.8%), 23 of which also carried stx genes. The Shiga toxin genes were detected in 177 isolates (51.3%) and the number of strains that carried stx1, stx2 and stx1/stx2 were 46, 73 and 58, respectively. Among 177 Shiga toxin-producing E. coli isolates, 89 carried the ehxA gene and 87 possessed the saa gene. Further characterization of the stx subtypes showed that among 104 stx1-positive isolates, 58 were the stx1c variant and 46 were the stx1 variant. Of the 131 stx2-positive strains, 48 were stx2, 48 were stx2c, 11 were stx2d, 17 were stx2g, and seven were stx2c/stx2g subtypes. The serogroups most prevalent among the 345 isolates were O15, O20, O103 and O157.
Animals ; Cattle ; Cattle Diseases/epidemiology/*microbiology ; DNA, Bacterial/chemistry/genetics ; Diarrhea/epidemiology/microbiology/*veterinary ; Escherichia coli/genetics/*isolation & purification/pathogenicity ; Escherichia coli Infections/epidemiology/microbiology/*veterinary ; Feces/microbiology ; Fimbriae, Bacterial/genetics ; Polymerase Chain Reaction/veterinary ; Polymorphism, Restriction Fragment Length ; Vietnam/epidemiology ; Virulence Factors/*genetics

A total of 156 Shiga-like toxin producing Escherichia coli (STEC) were isolated from fecal samples of Korean native (100/568, 18%) and Holstein dairy cattle (56/524, 11%) in Korea between September 2010 and July 2011. Fifty-two STEC isolates (33%) harbored both of shiga toxin1 (stx1) and shiga toxin2 (stx2) genes encoding enterohemolysin (EhxA) and autoagglutinating adhesion (Saa) were detected by PCR in 83 (53%) and 65 (42%) isolates, respectively. By serotyping, six STEC from native cattle and four STEC from dairy cattle were identified as O-serotypes (O26, O111, O104, and O157) that can cause human disease. Multilocus sequence typing and pulsed-field gel electrophoresis patterns highlighted the genetic diversity of the STEC strains and difference between strains collected during different years. Antimicrobial susceptibility tests showed that the multidrug resistance rate increased from 12% in 2010 to 42% in 2011. Differences between isolates collected in 2010 and 2011 may have resulted from seasonal variations or large-scale slaughtering in Korea performed to control a foot and mouth disease outbreak that occurred in early 2011. However, continuous epidemiologic studies will be needed to understand mechanisms. More public health efforts are required to minimize STEC infection transmitted via dairy products and the prevalence of these bacteria in dairy cattle.
Animals ; Anti-Bacterial Agents/pharmacology ; Cattle/microbiology ; Drug Resistance, Multiple, Bacterial ; Electrophoresis, Gel, Pulsed-Field/veterinary ; Escherichia coli Infections/epidemiology/microbiology/*veterinary ; Female ; Genes, Bacterial/genetics ; Latex Fixation Tests/veterinary ; Microbial Sensitivity Tests/veterinary ; Multilocus Sequence Typing/veterinary ; Prevalence ; Republic of Korea/epidemiology ; Shiga Toxin 1/genetics ; Shiga Toxin 2/genetics ; *Shiga-Toxigenic Escherichia coli/drug effects/genetics

A multiplex loop-mediated isothermal amplification (mLAMP) assay was developed for simultaneous detection of the stx1 and stx2 genes and applied for detection of shiga toxin-producing Escherichia coli (STEC) in cattle farm samples. Two target genes were distinguished based on T m values of 85.03 +/- 0.54degrees C for stx1 and 87.47 +/- 0.35degrees C for stx2. The mLAMP assay was specific (100% inclusivity and exclusivity), sensitive (with a detection limit as low as 10 fg/microL), and quantifiable (R 2 = 0.9313). The efficacy and sensitivity were measured to evaluate applicability of the mLAMP assay to cattle farm samples. A total of 12 (12/253; 4.7%) and 17 (17/253; 6.7%) STEC O157, and 11 (11/236; 4.7%) non-O157 STEC strains were isolated from cattle farm samples by conventional selective culture, immunomagnetic separation, and PCR-based culture methods, respectively. The coinciding multiplex PCR and mLAMP results for the types of shiga toxin revealed the value of the mLAMP assay in terms of accuracy and rapidity for characterizing shiga toxin genes. Furthermore, the high detection rate of specific genes from enrichment broth samples indicates the potential utility of this assay as a screening method for detecting STEC in cattle farm samples.
Animals ; Cattle ; Cattle Diseases/epidemiology/microbiology ; Escherichia coli Infections/epidemiology/microbiology/*veterinary ; Feces/microbiology ; Multiplex Polymerase Chain Reaction/veterinary ; Nucleic Acid Amplification Techniques/*veterinary ; Shiga Toxin 1/*genetics/isolation & purification ; Shiga Toxin 2/*genetics/isolation & purification ; Shiga-Toxigenic Escherichia coli/*genetics/isolation & purification

Seventy Escherichia coli isolates recovered from diseasedchickens diagnosed with colibacillosis in Henan Province,China, between 2004 and 2005 were characterized forantimicrobial susceptibility profiles via a broth doublingdilution method. Overall, the isolates displayed resistanceto trimethoprim-sulfamethoxazole (100%), oxytetracycline(100%), ampicillin (83%), enrofloxacin (83%), and ciprofloxacin(81%), respectively. Among the phenicols, resistance wasapproximately 79% and 29% for chloramphenicol andflorfenicol, respectively. Molecular detection revealed thatthe incidence rates of the floR, cmlA, cat1, cat2 and cat3were 29, 31, 16, 13, and 0%, respectively. Additionally,10% of the isolates were positive for both floR and cmlA.As these antimicrobial agents may potentially inducecross-resistance between animal and human bacterialpathogens, their prudent use in veterinary medicine ishighly recommended.
Animals ; Anti-Bacterial Agents/*pharmacology ; *Chickens ; China/epidemiology ; Chloramphenicol/pharmacology ; DNA, Bacterial/chemistry/genetics ; Drug Resistance, Multiple, Bacterial ; Escherichia coli/*drug effects/growth & development ; Escherichia coli Infections/epidemiology/microbiology/*veterinary ; Microbial Sensitivity Tests/veterinary ; Polymerase Chain Reaction/veterinary ; Poultry Diseases/epidemiology/*microbiology ; Thiamphenicol/analogs & derivatives/pharmacology