ABSTRACT
Aim: To investigate the stx1, stx2, hly, cnf2, sfa/foc, afaI, papC, and afaC virulence-associated genes of pathogenic Escherichia coli, isolated from diarrheic and non-diarrheic calves. Materials and Methods: The genes to be investigated were first isolated from the stool samples obtained from 150 diarrheic and non-diarrheic calves, between the ages of one day and six months, during the period 2016 to 2017. Rectal swabs were aseptically and randomly collected from several herds, from different regions in the province of Basra. Results of Research: The polymerase chain reaction (PCR) results showed that pathogenic E. coli were detected in a total of 34 out of 41 (82.9%) distributed as 23 out of 26 (88.5%) and 11 out of 15 (73.3%) of the diarrheagenic and non-diarrheagenic calves, respectively. The results also showed that stx1, hlyA, and stx2genes showed a higher incidence of distribution in both diarrheagenic and non-diarrheagenic calves, in a percentage rate of 69.6%, 65.2%, 56.5% and 63.6%, 63.6%, 45.5%, respectively. Moreover, eight different virulence gene profiles were established in the present study. Most of the isolates analyzed had at least two or three gene arrangements and only four isolates were seen in a combination of four genes stx1, stx2, hlyA, and afaI. Conclusion: It is concluded that E. coli isolates from healthy and diarrheic calves that carried various virulence genes, of which the most frequent were stx1, stx2, and hlyA. A high percentage of these isolates are found in both diarrheic and non-diarrheic calves.
ABSTRACT
BACKGROUND: Calf diarrhea is a major economic concern in bovine industry all around the world. This study was carried out in order to investigate distribution of virulence genes, pathotypes, serogroups and antibiotic resistance properties of Escherichia coli isolated from diarrheic calves. RESULTS: Totally, 76.45% of 824 diarrheic fecal samples collected from Isfahan, Chaharmahal, Fars and Khuzestan provinces, Iran were positive for E. coli and all of them were also positive for cnf2, hlyA, cdtIII, f17c, lt, st, stx1, eae, ehly, stx2 and cnf1 virulence genes. Chaharmahal had the highest prevalence of STEC (84.61%), while Isfahan had the lowest (71.95%). E. coli serogroups had the highest frequency in 1-7 days old calves and winter season. Distribution of ETEC, EHEC, AEEC and NTEC pathotypes among E. coli isolates were 28.41%, 5.07%, 29.52% and 3.49%, respectively. Statistical analyses were significant for presence of bacteria between various seasons and ages. All isolates had the high resistance to penicillin (100%), streptomycin (98.25%) and tetracycline (98.09%) antibiotics. The most commonly detected resistance genes were aadA1, sul1, aac[3]-IV, CITM, and dfrA1. The most prevalent serogroup among STEC was O26. CONCLUSIONS: Our findings should raise awareness about antibiotic resistance in diarrheic calves in Iran. Clinicians should exercise caution when prescribing antibiotics.
Subject(s)
Animals , Cattle , Cattle Diseases/microbiology , Escherichia coli Proteins/genetics , Drug Resistance, Bacterial/genetics , Diarrhea/veterinary , Escherichia coli/pathogenicity , Seasons , Virulence/genetics , Chloramphenicol Resistance/genetics , Serotyping , Polymerase Chain Reaction , Prevalence , Age Factors , DNA Primers , Diarrhea/microbiology , Diarrhea/epidemiology , Escherichia coli/drug effects , Disk Diffusion Antimicrobial Tests , Serogroup , Iran/epidemiologyABSTRACT
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.