Phenotypic and genotypic characterization of enterotoxigenic Escherichia coli isolated from diarrheic calves in Argentina

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. Keywords: Antimicrobial resistance, Dairy cattle, Escherichia coli, Neonatal diarrhea, Virulence gene

Phenotypic and genotypic characterization of enterotoxigenic Escherichia coli isolated from diarrheic calves in Argentina

Enterotoxigenic Escherichia coli (ETEC) is the most common and global cause of neonatal calf diarrhea, but there is little information regarding calf ETEC strains in Argentina. In this study, five ETEC isolates from diarrheic dairy calves (2-10 days-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 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, 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 multiresistance phenotype (resistance to 4 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 multiresistant ETEC associated with neonatal diarrhea in dairy calves in Argentina. This finding may be used for diagnostic and therapeutic purposes

Estudio retrospectivo de multirresistencia antimicrobiana en aislamientos de Escherichia coli de terneros con diarrea neonatal = Retrospective study of multiple antimicrobial resistance in Escherichia coli isolates from neonatal calves with diarrhea

Escherichia coli es una de las principales etiologías de la diarrea neonatal de los terneros y el tratamiento de esta enfermedad incluye el uso de antimicrobianos. Se realizó un estudio retrospectivo durante un período de 22 años con la finalidad de identificar los antimicrobianos de uso más frecuente para el tratamiento de dicha enfermedad y evaluar la frecuencia de resistencia antimicrobiana en aislamientos de Escherichia coli de terneros en dos sistemas productivos. Las muestras de materia fecal se obtuvieron de 93 terneros con diarrea (rodeo para carne, n= 57; rodeo lechero, n= 36) de 1-60 días de vida, los cuales procedían de 57 establecimientos. En 93 aislamientos de Escherichia coli se evaluó la sensibilidad in vitro frente a 26 antimicrobianos, de 10 familias diferentes, utilizando el método de Kirby-Bauer. No se utilizaron técnicas complementarias para diferenciar los aislamientos de Escherichia coli en patógenos o comensales. La información inherente a los terneros y a los tratamientos con antimicrobianos se obtuvo a partir de las anamnesis realizadas o de las fichas que acompañaron a las muestras remitidas al laboratorio. La mayoría de los aislamientos presentaron resistencia a sulfonamidas (88,5%), oxitetraciclina (87%) y enrofloxacina (67%) y estos antimicrobianos fueron comúnmente utilizados para el tratamiento de la diarrea de los terneros. El 88% de los aislamientos de terneros de rodeos para carne y el 95% de los aislamientos de terneros de rodeos lecheros mostraron multirresistencia antimicrobiana. Asimismo, estos últimos desarrollaron resistencia hacia un mayor número de familias de antimicrobianos. El 86% de los aislamientos presentaron resistencia a los antimicrobianos que habían sido utilizados para el tratamiento de los terneros. El mayor nivel de multirresistencia (82%) se encontró en los aislamientos obtenidos en terneros de 1-15 días de vida. La multirresistencia antimicrobiana es una característica fenotípica que está ampliamente distribuida en los aislamientos de Escherichia coli obtenidos de terneros con diarrea. Esta característica tendría una mayor importancia en los aislamientos procedentes de terneros de rodeos lecheros.Escherichia coli is one of the main etiologies of diarrhea in neonatal calves and antimicrobials are frequently used for therapeutic purposes. A retrospective study over a 22 year period was conducted in order to compare antimicrobial resistance in Escherichia coli isolates from diarrheic calves in two husbandry systems. Ninety three fecal samples (beef, n = 57; dairy, n = 36) were collected from 1- to 60-day old diarrheic calves belonging to 57 farms. The antimicrobial susceptibility profiles were evaluated in 93 Escherichia coli isolates using the Kirby-Bauer method. A total of 26 antimicrobials from 10 different families were included in the analyses. No additional techniques were performed to differentiate among commensal and pathogenic Escherichia coli. Most of the isolates showed resistance to sulfonamides (88.5%), oxitetracycline (87%) and enrofloxacin (67%), all of them being widely used for the treatment of calf diarrhea. Multiple antimicrobial resistance was demonstrated in 88% of the isolates from beef calves and in 95% of the isolates from dairy ones. Nevertheless, isolates from dairy calves revealed a broader spectrum of resistance to different antimicrobial families. In addition, 86% of the isolates displayed resistance to those antimicrobials that had been previously used for the treatment of calves. The higher frequency (82%) of multiple antimicrobial resistant Escherichia coli isolates was observed in 1- to 15-day old calves. Multiple antimicrobial resistance represents a phenotypic feature that remains widely spread among Escherichia coli isolates from neonatal calves with diarrhea. Nevertheless, this feature seems to acquire more importance in dairy calves.Fil: Spetter, Lucas Maximiliano. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Balcarce; ArgentinaFil: Louge Uriarte, Enrique Leopoldo. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Balcarce. Grupo de Salud Animal; ArgentinaFil: González Pasayo, Ramón A. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Balcarce. Grupo de Salud Animal; ArgentinaFil: Malena, Rosana Claudia. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Balcarce. Grupo de Salud Animal; ArgentinaFil: Moreira, Ana Rita. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Balcarce. Grupo de Salud Animal; Argentin