Phenotypic and genotypic characterization of enterotoxigenic <i>Escherichia coli</i> isolated from diarrheic calves in Argentina

Abstract

Enterotoxigenic Escherichia coli (ETEC) is the most common and global cause of neonatal calf diarrhea, but there is a little information regarding calf ETEC strains in Argentina. In this study, five ETEC isolates from diarrheic dairy calves (2–10 d old) from Buenos Aires and Cordoba, Argentina were characterized on the basis of virulence gene (VG) pattern, O:H serotyping, hemolytic phenotype, phylogenetic group affiliation, antimicrobial (AM) resistance profile, and presence of integron class 1 and 2. The five isolates were examined by polymerase chain reaction (PCR) for the presence of 18 bovine VGs and showed the following genotypes: F5 + /F41 + / sta + (D242), F5 + / sta + (D158), F5 + / sta + (D157), F5 + (D151-9), and F5 + / iucD + (D151-5). These VGs confer pathogenic potential and most of them are associated with the ETEC pathotype. The five isolates showed a non-hemolytic phenotype, belonged to five different serotypes: O101:H − , O141:H − , O60:H − , ONT:H10, and ONT:H − , and were assigned to the phylogenetic group A by the quadruplex Clermont PCR method. The AM resistance of the three isolates D242, D157, and D151-5 was determined by agar disk diffusion method for 24 AMs and they exhibited a multi-resistance phenotype (resistance to four different AM classes: Cephalosporins, Penicillins, Macrolides, and Ansamycins). In addition, class 1 integrons were found in the isolate D151-5 containing the dfrA17-aadA5 gene cassette and in the bovine ETEC reference strain FV10191 containing the dfrA1-aadA1 gene cassette. The present study revealed for the first time the occurrence of multi-resistant ETEC associated with neonatal diarrhea in dairy calves in Argentina. This finding may be used for diagnostic and therapeutic purposes.

Relationship between Phenotypic and Genotypic Antimicrobial Resistance of Escherichia coli Isolates from Mastitic Milk

“…Multidrug resistance (MDR) among E. coli isolates was high, where 61% of E. coli isolates (36/59) showed MDR against two or more antimicrobials, nine isolates (15.3%) exhibit MDR for β-lactam antibiotics, six isolates (10.2%) for non-β-lactam antibiotics, 19 isolates (32.2%) were resistant to both (β-lactams and non-βlactams) and two isolates (3.4%) showed resistance to all antimicrobial used in this study. Our results were compatible with Pasayo et al (2019) who declared that frequent use of antibiotic treatment leading to the production of multiresistant strains that pose a major public health threat. But not aligned with Ahmed et al (2009) who stated that lower multi-antibiotic resistance has been found in E. coli…”

Causes of neonatal calf diarrhea and mortality in pasture-based dairy herds in Uruguay: a farm-matched case-control study

“…Furthermore, it should be considered that even though the expression of the fimbrial antigen F5 and the production of heat-stable toxin (STa) are highly associated in enterotoxigenic E. coli , some studies have found E. coli F5+ strains without toxigenic potential (i.e., PCR negative for the STa-encoding gene). This could explain why diarrhea was not observed in some of the positive calves [ 77 – 80 ]. In addition, it is not unexpected to have false negative results using antigen-capture ELISA for F5, as this test has a low sensitivity [ 12 ].…”

Antimicrobial Resistance, Serologic and Molecular Characterization of E. coli Isolated from Calves with Severe or Fatal Enteritis in Bavaria, Germany

“…The expression of potential virulent F5 fimbria was investigated by subculturing the isolates on pH 7.5 stabile, “minimum of casein” (Minca) agar (Sifin Diagnostics GmbH, Berlin, Germany) as previously published [ 76 ]. Finally, potential hemolytic properties of isolates were interpreted as described with subcultures on Columbia Sheep Blood Agar (Sifin Diagnostics GmbH, Berlin, Germany) [ 77 ]. Growth incubation was carried out for 18 to 24 h at 37 °C at all times.…”