Aims:  To study the seasonal variation of Shiga toxin‐encoding genes (stx) and to investigate the presence of Shiga toxin‐producing Escherichia coli (STEC) O157 in cattle belonging to five dairy farms from Argentina. Methods and Results:  Rectal swab samples were collected from 360 dairy cows in each season and 115 and 137 calves in autumn and in spring, respectively. The stx were investigated by multiplex PCR and it was used as the indicator for STEC. Samples positives for stx were tested by PCR for eae‐γ1 of E. coli O157 and then subjected to IMS (immunomagnetic separation). In positive animals significant differences in the prevalence of stx between warm and cold seasons were detected. In warm seasons, stx1 + stx2 increased and stx1 decreased, independently of the animal category. The prevalence of STEC O157 in cows and calves were 0·2% and 0·8%, respectively. Conclusions:  This work provides new data about the occurrence of stx and STEC O157 in dairy herds from Argentina and suggests a relationship between the type of stx and season of year. Significance and Impact of Study:  The detection of STEC O157 and the seasonality of stx and its types provide an opportunity to improve control strategies designed to prevent contamination of food products and transmission animal‐person.

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The aim of this study was to investigate the role and clinical course of verotoxigenic Escherichia coli (VTEC) infections in children with acute diarrhoea from Argentina, the country with the highest worldwide incidence of haemolytic uraemic syndrome (HUS). To accomplish this objective, 437 samples from children up to 6 years old with acute diarrhoea were collected and processed. More than 60 % of the children studied presented watery or mucous diarrhoea without blood, and in 25.2 % of the cases the samples contained blood. In a first screening, a multiplex PCR was performed to detect the presence of the vt 1 , vt 2 , eae, ehxA and saa virulence genes. The strains were then isolated and analysed to characterize their serotypes, virulence genes, antibiotic susceptibility profiles and verotoxin (VT) production. Forty-four of the 437 samples (10.1 %) were positive for VTEC virulence genes. VTEC-infected patients presented different types of diarrhoea (27.3 % belonged to the non-bloody type). Several serotypes and virulence genotypes were found. Isolates belonged to the serotypes O157 : H7, O145 : H " , O26 : H11, O121 : H19, O111 : H2 and O118 : H2. HUS developed in 16 (36.4 %) patients positive for VTEC virulence genes. All of the VTEC isolates produced a cytopathic effect on Vero cell monolayers, confirming the ability to express VT. Despite most strains being sensitive to all of the antimicrobials studied, a positive association between clinical progression to HUS and antibiotic therapy was observed for the total number of patients studied, as well as for the VTEC + group. In conclusion, the data obtained in this study increase our knowledge of the role and clinical course of VTEC infection in childhood acute diarrhoea beyond bloody diarrhoea, and might be considered for the prevention, diagnosis and management of this disease. It is possible that the optimal approach for VTEC diagnosis could be using multiplex PCR to search for the presence of the vt 1 , vt 2 , eae and ehxA genes.

Hygienic behavior of honeybees involves inspection, uncapping and removal of diseased and dead brood from the colony. The objective of this work was to study the activities involved in hygienic behavior of individually tagged bees from selected hygienic (H) and non-hygienic (NH) colonies in the presence of chalkbrood infected brood (Ascosphaera apis) or pin-killed brood. No significant difference was detected in the age of bees inspecting, uncapping or removing brood in H and NH colonies; the median age was 15 days for all activities. The percentage of bees that performed these activities was significantly higher in H colonies. In NH colonies the bees that performed this behavior were more persistent but bees in H colonies were more efficient in the removal of the chalkbrood mummies. H colonies began uncapping more rapidly in response to the stimulus of dead brood independent of the method used to kill it. H and NH bees took the same amount of time to remove the mummies once they initiated the uncapping process but NH colonies took longer to remove pin-killed brood. These findings confirm previous behavioral studies on the activities of hygienic and non-hygienic bees toward freeze-killed brood, but this is the first time the entire process from inspection to removal was focused on individual cells containing actual diseased brood.

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